EES Manuel

# EES Manuel - EES Engineering Equation Solver for Microsoft...

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Unformatted text preview: EES Engineering Equation Solver for Microsoft Windows Operating Systems Commercial and Professional Versions F-Chart Software http://www.fchart.com/ email: [email protected] Copyright 1992-2010 by S.A. Klein All rights reserved. The authors make no guarantee that the program is free from errors or that the results produced with it will be free of errors and assume no responsibility or liability for the accuracy of the program or for the results that may come from its use. EES was compiled with DELPHI 5 by Borland The three-dimensional plotting package is based on a modification of the public domain GLScene package (http://www.glscene.org/). The genetic optimization method implemented in EES is derived from the public domain Pikaia optimization program (version 1.2, April 2002) written by Paul Charbonneau and Barry Knapp at National Center for Atmospheric Research (NCAR) (http://www.hao.ucar.edu/public/research/si/pikaia/pikaia.html). Registration Number__________________________ ALL CORRESPONDENCE MUST INCLUDE THE REGISTRATION NUMBER V8.590 Table of Contents Table of Contents............................................................................................................................... iii Overview...............................................................................................................................................1 Getting Started.....................................................................................................................................5 Installing EES on your Computer ....................................................................................................5 Starting EES .....................................................................................................................................5 Background Information ..................................................................................................................6 An Example Thermodynamics Problem ........................................................................................10 EES Windows ....................................................................................................................................23 General Information .......................................................................................................................23 Equations Window .........................................................................................................................25 Formatted Equations Window........................................................................................................29 Solution Window............................................................................................................................32 Arrays Window ..............................................................................................................................34 Residuals Window..........................................................................................................................36 Parametric Table Window..............................................................................................................38 Lookup Table Window...................................................................................................................44 Integral Table Window...................................................................................................................46 Diagram Window ...........................................................................................................................47 Development and Application Modes........................................................................................48 Moving the Diagram ..................................................................................................................49 Resizing the Diagram .................................................................................................................49 Adding and Moving Text on the Diagram Window Adding Graphic Items Group and Ungroup Buttons Adding a Calculate Button ...........................................................49 ..............................................56 ............................................................................................55 ........................................................................................56 ..................................................................................................57 Selecting, Modifying and Aligning Text and Graphic Items Adding a Plot Window Access Button ...............................................................................57 Creating Hot Areas and Child Diagram Windows (Professional Version only)........................58 Saving User Inputs Adding a Help Button ..............................................................................................................59 ...............................................................................59 .........................................................................................................62 Creating Links (Professional Version) Navigating through Child Diagram Window (Professional Version) ...........................62 Adding a Print Button ...........................................................................................................62 .............................................................................................63 Adding an Audio-Visual Item Saving and Loading User Inputs (Professional Version) Creating and Using Check Boxes (Professional Version) ii .............................................64 ..................................................64 Creating and Using Radio Groups (Professional Version) .................................................66 Animation (Professional Version) .............................................................................................67 Plot Windows .................................................................................................................................71 Moving the Plot ...................................................................................................................71 Adding / Changing Text and Text Characteristics .............................................................72 Moving Text ...............................................................................................................................74 Adding Lines and Arrows, Rectangles and Circles ...............................................75 Moving Lines and Arrows, Rectangles and Circles ...................................................................76 Resizing the Plot.........................................................................................................................76 Modifying the Axis Information ................................................................................................77 Aligning Items on the Plot Window ...................................................................................80 .............................................................................................................................80 Crosshairs 3-D Plot Controls .......................................................................................................................81 Report Window (Professional Version) .........................................................................................85 Debug Window ..............................................................................................................................87 Incorrect Degrees of Freedom ....................................................................................................87 Constrained Solution ..................................................................................................................88 Unit Checking Report.................................................................................................................89 Calculator Window ................................................................................................................90 Menu Commands ..............................................................................................................................91 The File Menu ................................................................................................................................91 The Edit Menu ..............................................................................................................................102 The Search Menu .........................................................................................................................106 The Options Menu ........................................................................................................................107 The Calculate Menu .....................................................................................................................126 The Tables Menu ..........................................................................................................................134 The Plot Menu ..............................................................................................................................143 The Windows Menu .....................................................................................................................155 The Help Menu.............................................................................................................................158 The Textbook Menu .....................................................................................................................160 Built-in Functions ...........................................................................................................................162 Mathematical Functions ...............................................................................................................162 CurveFit1D Procedure..................................................................................................................177 String Functions ...........................................................................................................................178 Thermophysical Property Functions ............................................................................................181 Using Lookup Files and Lookup Tables ......................................................................................191 Binary Lookup files (.LKT) .....................................................................................................191 ASCII Lookup files (.TXT)......................................................................................................191 ASCII Lookup files (.CSV) and Format Specification Files. (.FMT)......................................192 -iii- Solid/Liquid Property Library......................................................................................................199 Functions, Procedures, Modules, and Subprograms .....................................................................202 EES Functions ..............................................................................................................................203 EES Procedures ............................................................................................................................206 Single-Line If Then Else Statements...........................................................................................208 Multiple-Line If Then Else Statements ........................................................................................209 GoTo Statements ..........................................................................................................................210 Return Statement .........................................................................................................................210 Repeat Until Statements .............................................................................................................210 Error Procedure ............................................................................................................................211 Warning Procedure .......................................................................................................................212 Print Command in Functions and Procedures ..............................................................................213 Modules and SubPrograms...........................................................................................................214 Library Files .................................................................................................................................218 External Functions and Procedures ...............................................................................................221 EES External Functions (.DLF files) ...........................................................................................221 The PWF Function – a .DLF external routine in written in DELPHI ......................................223 SUM_C – a .DLF external function written in Microsoft’s Visual C++ .................................227 EES External Procedures (.FDL and .DLP files) ......................................................................228 External Procedures with the .FDL Format - a FORTRAN Example......................................229 External Procedures with the .DLP Format - a Pascal Example ..............................................231 External Procedures with the .DLP Format - a C++ Example .................................................233 Multiple Files in a Single Dynamic Link Library (.DLL)............................................................235 Help for External Functions and Procedures................................................................................239 Library Manager (Professional Version)......................................................................................240 Advanced Features ..........................................................................................................................241 String Variables ............................................................................................................................241 Complex Variables .......................................................................................................................242 Array Variables ............................................................................................................................246 The DUPLICATE Command.......................................................................................................248 Matrix Capabilities .......................................................................................................................249 Using the Property Plot ................................................................................................................251 Integration and Differential Equations .........................................................................................252 Method 1: Solving Differential Equations with the Table-Based Integral Function ..............254 Method 2: Use of the $Integral Directive and the Equation-Based Integral Function ............258 Method 3: Solving Differential Equations with the TableValue Function .............................260 Directives .....................................................................................................................................265$ARRAYS On/Off Directive ...................................................................................................265 $CHECKUNITS On/Off/AutoOn/AutoOff .............................................................................265$COMMON Directive..............................................................................................................266 ii $COMPLEX Directive .............................................................................................................266$CONSTANT Directive ...........................................................................................................266 $DOLAST and$ENDDOLAST Directives .............................................................................267 $EXPORT Directive ................................................................................................................267$HIDEWINDOW Directive .....................................................................................................269 $IF/IFNOT Directives ..............................................................................................................269$IMPORT Directive .................................................................................................................271 $INCLUDE Directive ..............................................................................................................272$INTEGRALAUTOSTEP Directive........................................................................................273 $INTEGRALTABLE Directive ...............................................................................................274$LOCALVARIABLES Directive ............................................................................................275 $OPENLOOKUP Directive .....................................................................................................275$PRIVATE Directive ...............................................................................................................276 $REAL Directive......................................................................................................................276$REFERENCE Directive .........................................................................................................277 $REQUIREDOUTPUTS Directive..........................................................................................277$SAVELOOKUP Directive .....................................................................................................277 $SAVETABLE Directive .........................................................................................................278$STOPCRITERIA Directive ....................................................................................................279 $SHOWWINDOW Directive...................................................................................................279$SUMROW Directive ..............................................................................................................279 $TABWIDTH Directive...........................................................................................................280$TRACE Directive...................................................................................................................280 $UNITSYSTEM Directive .......................................................................................................280$WARNINGS On/Off Directive ..............................................................................................280 Creating and Using Macro Files (Professional Version)..............................................................282 Unit Lists ......................................................................................................................................294 Creating Entries to the Visual Libraries .......................................................................................296 Hints for Using EES........................................................................................................................299 Numerical Methods Used in EES ...................................................................................................302 Solution to Algebraic Equations ..................................................................................................302 Blocking Equation Sets ................................................................................................................305 Determination of Minimum or Maximum Values .......................................................................307 Numerical Integration ..................................................................................................................308 References ....................................................................................................................................310 Adding Property Data to EES .........................................................................................................312 Background Information ..............................................................................................................312 Adding Fluid Properties to EES ...................................................................................................313 SAMPLE TESTCO2.IDG File .................................................................................................313 SAMPLE XFLUID.MHE File for pure fluids .........................................................................315 -iii- __________________________________________________________________________ Overview __________________________________________________________________________ EES (pronounced 'ease') is an acronym for Engineering Equation Solver. The basic function provided by EES is the solution of a set of algebraic equations. EES can also solve differential equations, equations with complex variables, do optimization, provide linear and non-linear regression, generate publication-quality plots, simplify uncertainty analyses and provide animations. EES has been developed to run under 32-bit Microsoft Windows operating systems, i.e., Windows 95/98/2000/XP. It can be run in Linux and on the Macintosh using emulation programs. There are two major differences between EES and existing numerical equation-solving programs. First, EES automatically identifies and groups equations that must be solved simultaneously. This feature simplifies the process for the user and ensures that the solver will always operate at optimum efficiency. Second, EES provides many built-in mathematical and thermophysical property functions useful for engineering calculations. For example, the steam tables are implemented such that any thermodynamic property can be obtained from a built-in function call in terms of any two other properties. Similar capability is provided for most organic refrigerants (including some of the new blends), ammonia, methane, carbon dioxide and many other fluids. Air tables are built-in, as are psychrometric functions and JANAF table data for many common gases. Transport properties are also provided for most of these substances. The library of mathematical and thermophysical property functions in EES is extensive, but it is not possible to anticipate every user's need. EES allows the user to enter his or her own functional relationships in three ways. First, a facility for entering and interpolating tabular data is provided so that tabular data can be directly used in the solution of the equation set. Second, the EES language supports user-written Functions and Procedures similar to those in Pascal and FORTRAN. EES also provides support for user-written routines, which are self-contained EES programs that can be accessed by other EES programs. The Functions, Procedures, Subprograms and Modules can be saved as library files which are automatically read in when EES is started. Third, external functions and procedures, written in a highlevel language such as Pascal, C or FORTRAN, can be dynamically-linked into EES using the dynamic link library capability incorporated into the Windows operating system. These three methods of adding functional relationships provide very powerful means of extending the capabilities of EES. 1 The motivation for EES rose out of experience in teaching mechanical engineering thermodynamics and heat transfer. To learn the material in these courses, it is necessary for the student to work problems. However, much of the time and effort required to solve problems results from looking up property information and solving the appropriate equations. Once the student is familiar with the use of property tables, further use of the tables does not contribute to the student's grasp of the subject; nor does algebra. The time and effort required to do problems in the conventional manner may actually detract from learning of the subject matter by forcing the student to be concerned with the order in which the equations should be solved (which really does not matter) and by making parametric studies too laborious. Interesting practical problems that may have implicit solutions, such as those involving both thermodynamic and heat transfer considerations, are often not assigned because of their mathematical complexity. EES allows the user to concentrate more on design by freeing him or her from mundane chores. EES is particularly useful for design problems in which the effects of one or more parameters need to be determined. The program provides this capability with its Parametric Table, which is similar to a spreadsheet. The user identifies the variables that are independent by entering their values in the table cells. EES will calculate the values of the dependent variables in the table. The relationship of the variables in the table can then be displayed in publication-quality plots. EES also provides capability to propagate the uncertainty of experimental data to provide uncertainty estimates of calculated variables. With EES, it is no more difficult to do design problems than it is to solve a problem for a fixed set of independent variables. EES offers the advantages of a simple set of intuitive commands that a novice can quickly learn to use for solving any algebraic problems. However, the capabilities of this program are extensive and useful to an expert as well. The large data bank of thermodynamic and transport properties built into EES is helpful in solving problems in thermodynamics, fluid mechanics, and heat transfer. EES can be used for many engineering applications; it is ideally suited for instruction in mechanical engineering courses and for the practicing engineer faced with the need for solving practical problems. The remainder of this manual is organized into seven chapters and three appendices. A new user should read Chapter 1 which illustrates the solution of a simple problem from start to finish. Chapter 2 provides specific information on the various functions and controls in each of the EES windows. The animation capabilities provided in the Diagram window are described in this chapter. Chapter 3 is a reference section that provides detailed information for each menu command. Chapter 4 describes the built-in mathematical and thermophysical property functions and the use of the Lookup Table for entering tabular data. Chapter 5 provides instructions for writing EES Functions, Procedures, Subprograms and Modules and 2 saving them in Library files. Chapter 6 describes how external functions and procedures, written as Windows dynamic-link library (DLL) routines, can be integrated with EES. Chapter 7 describes a number of advanced features in EES such as the use of string, complex and array variables, the solution of simultaneous differential and algebraic equations, and property plots. The use of directives and macros is also explained. Appendix A contains a short list of suggestions. Appendix B describes the numerical methods used by EES. Appendix C shows how additional property data may be incorporated into EES. 3 4 CHAPTER 1 __________________________________________________________________________ __________________________________________________________________________ Getting Started Installing EES on your Computer EES is distributed in a self-installing compressed form in a file called SETUP_EES.exe. To install EES, it is necessary execute the SETUP_EES installation program. If you are installing EES from a CD, the installation program will start automatically when the CD is placed in the drive. Alternatively, double-click on the SETUP_EES.exe file. The installation program will provide a series of prompts which will lead you through the complete installation of the EES program. The default folder for the EES files is C:\EES32. Starting EES The default installation program will create a directory named C:\EES32 in which the EES files are placed. The EES program icon shown above will identify both the program and EES files. Double-clicking the left mouse button on the EES program or file icon will start the program. If you double-clicked on an EES file, that file will be automatically loaded. 5 Chapter 1 Getting Started Background Information EES begins by displaying a dialog window that shows registration information, the version number and other information. The version number and registration information will be needed if you request technical support. If this is your first time running EES, you may wish to specify the default unit system and other default settings. Clicking the Preferences button will take you to the Preferences dialog where the options can be changed and stored. Alternatively, click the Continue button to dismiss the dialog window and start with an empty EES documents. Detailed help is available at any point in EES. Pressing the F1 key will bring up a Help window relating to the foremost window. Clicking the Contents button will present the Help index shown below. Clicking on an underlined word (shown in green on color monitors) will provide help relating to that subject. 6 Getting Started Chapter 1 7 Chapter 1 Getting Started EES commands are distributed among nine pull-down menus. (A tenth user-defined menu, used below for Examples, can be placed by the user to the right of the Help menu. See the discussion of the Load Textbook command File menu in Chapter 3.) A brief summary of their functions follows. Detailed descriptions of the commands appear in Chapter 3. Note that a toolbar is provided below the menu bar. The toolbar contains small buttons which provide rapid access to many of the most frequently used EES menu commands. If you move the cursor over a button and wait for a few seconds, a few words will appear to explain the function of that button. The toolbar can be hidden, if you wish, with a control in the Preferences dialog (Options menu). The System menu represented by the EES icon appears above the file menu. The System menu is not part of EES, but rather a feature of the Windows Operating System. It holds commands that allow window moving, resizing, and switching to other applications. The File menu provides commands for loading, merging and saving work files and libraries, and printing. The Edit menu provides the editing commands to cut, copy, and paste information. The Search menu provides Find and Replace commands for use in the Equations window. The Options menu provides commands for setting the guess values and bounds of variables, the unit system, default information, and program preferences. A command is also provided for displaying information on built-in and user-supplied functions. The Calculate menu contains the commands to check, format and solve the equation set. The Tables menu contains commands to set up and alter the contents of the Parametric and Lookup Tables and to do linear regression on the data in these tables. The Parametric Table, similar to a spreadsheet, allows the equation set to be solved repeatedly while varying the values of one or more variables. The Lookup table holds user-supplied data which can be interpolated and used in the solution of the equation set. The Plot menu provides commands to modify an existing plot or prepare a new plot of data in the Parametric, Lookup, or Array tables. Curve-fitting capability is also provided. The Windows menu provides a convenient method of bringing any of the EES windows to the front or to organize the windows. The Help menu provides commands for accessing the online help documentation. 8 Getting Started Chapter 1 The basic capability provided by EES is the solution of a set of non-linear algebraic equations. To demonstrate this capability, start EES and enter this simple example problem in the Equations window. Note that EES makes no distinction between upper and lower case letters and the ^ sign (or **) is used to signify raising to a power. If you wish, you may view the equations in mathematical notation by selecting the Formatted Equations command from the Windows menu. Select the Solve command from the Calculate menu. A dialog window will appear indicating the progress of the solution. When the calculations are completed, the button changes from Abort to Continue. Click the Continue button. The solution to this equation set will then be displayed. 9 Chapter 1 Getting Started An Example Thermodynamics Problem A simple thermodynamics problem will be set up and solved in this section to illustrate the property function access and equation solving capability of EES. The problem, typical of that which may be encountered in an undergraduate thermodynamics course, is as follows. Refrigerant-134a enters a valve at 700 kPa, 50°C with a velocity of 15 m/s. At the exit of the valve, the pressure is 300 kPa. The inlet and outlet fluid areas are both 0.0110 m2. Determine the temperature, mass flow rate and velocity at the valve exit. State 1 T = 50°C P = 700 Vel = 15 m/s State 2 T=? P = 300 kPa Vel = ? To solve this problem, it is necessary to choose a system and then apply mass and energy balances. The system is the valve. The mass flow is steady, so that the mass balance is: m1 = m2 (1) (2) (3) where m1 = A1 Vel1 / v1 m1 = A2 Vel2 / v2 m = mass flowrate [kg/s] A = cross-sectional area [m2] Vel = velocity [m/s] v = specific volume [m3/kg] We know that A1 = A2 (4) The valve is assumed to be well-insulated with no moving parts. The heat and work effects are both zero. A steady-state energy balance on the valve is: 2 2 Vel1 Vel2 = m2 h 2 + m1 h1 + 2 2 (5) where h is the specific enthalpy and Vel2/2 is the specific kinetic energy. In SI units, specific enthalpy normally has units of [kJ/kg] so some units conversions may be needed. EES provides unit conversion capabilities with the CONVERT function as documented in Chapter 4. In addition, EES can manually or automatically check that all unit conversions 10 Getting Started Chapter 1 have been made and the units in each equation are dimensionally consistent. The Check Units command (Calculate menu) initiates the unit checking capability manually. From relationships between the properties of R134a: h1 = h (T1 , P ) 1 v1 = v (T1 , P ) 1 (6) (7) (8) (9) h2 = h (T2 , P2 ) v2 = v (T2 , P2 ) Ordinarily, the terms containing velocity are neglected, primarily because the kinetic energy effects are usually small and also because these terms make the problem difficult to solve. However, with EES, the computational difficulty is not a factor. The user can solve the problem with the kinetic energy terms and judge their importance. The values of T1, P1, A1, Vel11 and P2 are known. There are nine unknowns: A2, m1 , m2 , Vel2, h1, v1, h2, v2, T2. Since there are 9 equations, the solution to the problem is defined. It is now only necessary to solve the equations. This is where EES can help. Start EES and select the New command from the File menu. A blank Equations window will appear. Before entering the equations, however, set the unit system for the built-in thermophysical properties functions. To view or change the unit system, select Unit System from the Options menu. 11 Chapter 1 Getting Started EES is initially configured to be in SI units with T in °C, P in kPa, energy units in kJ and specific property values in their customary units on a mass basis. These defaults may have been changed during a previous use. Click on the controls to set the units as shown above. Click the OK button (or press the Return key) to accept the unit system settings. The equations can now be entered into the Equations window. Text is entered in the same manner as for any word processor. Formatting rules are as follows: 1. Upper and lower case letters are not distinguished. EES will (optionally) change the case of all variables to match the manner in which they first appear. 2. Blank lines and spaces may be entered as desired since they are ignored. 3. Comments must be enclosed within braces { } or within quote marks " ". Comments may span as many lines as needed. Comments within braces may be nested in which case only the outermost set of { } are recognized. Comments within quotes will also be displayed in the Formatted Equations window. 4. Variable names must start with a letter and consist of any keyboard characters except ( ) ‘ | * / + - ^ { } : " or ;. Array variables (Chapter 7) are identified with square braces around the array index or indices, e.g., X[5,3]. String variables (Chapter 7) are identified with a $as the last character in the variable name. The maximum length of a variable name is 30 characters. 5. Multiple equations may be entered on one line if they are separated by a semi-colon (;)1. The maximum line length is 255 characters. 6. The caret symbol ^ or ** is used to indicate raising to a power. 7. The order in which the equations are entered does not matter. 8. The position of knowns and unknowns in the equation does not matter. 9. Units for constants can be entered in braces directly following the comment, e.g. g = 9.82 [m/s^2] 10. Underscore characters can be used to produce subscripts on the formatted output. Greek symbol names will be replaced by the Greek characters. After entering the equations for this problem and (optionally) checking the syntax using the Check/Format command in the Calculate menu, the Equations window will appear as shown. Note that _1 and _2 were used in this example to designate states 1 and 2. Array variables with [1] and [2] could also have been used. Comments are normally displayed in blue on a color monitor. Other formatting options are set with the Preferences command in the Options menu. The$TabStops directive makes it easy to align the comments. 1 If a comma is selected as the Decimal Symbol in the Windows Regional Settings Control Panel, EES will recognize the comma (rather than a decimal point) as a decimal separator, the semicolon (rather than the comma) as an argument separator, and the colon : (rather than the semicolon) as the equation separator. 12 Getting Started Chapter 1 Unit consistency is as important as entering the correct equations. EES can check the unit consistency of the equations provided that the units of each variable are known. The units of constants, such as T_1, can be set by following the value with its units in square brackets. The units of variables, such as m_dot_2, can be set in several ways. Perhaps the simplest way is to select the variable in the Equations window and then click the right mouse button. A pop-up menu will appear with a number of useful menu items. The Comment menu item will place commenting braces { } around the selection. If the section has braces, they will be removed. Cut, Copy and Paste have their usual meaning. The Variable Info menu item provides an easy way to enter the units of a variable in the Equations window. 13 Chapter 1 Getting Started Selecting the Variable Info menu item will bring up a small dialog in which the display format and units for the selected variable, m_dot_2 in this case, can be entered. Note the use of the Convert function in energy balance to convert the units of the specific kinetic energy [m^2/s^2] to the units used for specific enthalpy [kJ/kg]. The Convert function is most useful in these problems. See Chapter 4 for a detailed description of its use. The thermodynamic property functions, such as enthalpy and volume require a special format. The first argument of the function is the substance name, R134a in this case. The following arguments are the independent variables preceded by a single identifying letter and an equal sign. Allowable letters are T, P, H, U, S, V, and X, corresponding to temperature, pressure, specific enthalpy, specific internal energy, specific entropy, specific volume, and quality. (For psychrometric functions, additional allowable letters are W, R, D, and B, corresponding to humidity ratio, relative humidity, dewpoint temperature, and wetbulb temperature.) An easy way to enter functions, without needing to recall the format, is to use the Function Information command in the Options menu. This command will bring up the dialog window shown below. Click on the ‘Thermophysical properties’ radio button. The list of built-in thermophysical property function will appear on the left with the list of substances on the right. Select the property function by clicking on its name, using the scroll bar, if necessary, to bring it into view. Select a substance in the same manner. An example of the function showing the format will appear in the Example rectangle at the bottom. The information in the rectangle may be changed, if needed. Clicking the Paste button will copy the Example into the Equations window at the cursor position. Additional information is available by clicking the Function Info and Fluid Info buttons. 14 Getting Started Chapter 1 It is usually a good idea to set the guess values and (possibly) the lower and upper bounds for the variables before attempting to solve the equations. This is done with the Variable Information command in the Options menu. Before displaying the Variable Information dialog, EES checks syntax and compiles newly entered and/or changed equations, and then solves all equations with one unknown. The Variable Information dialog will then appear. The Variable Information dialog contains a line for each variable appearing in the Equations window. By default, each variable has a guess value of 1.0 with lower and upper bounds of negative and positive infinity. The A in the Display options column indicates that EES will automatically determine the display format for numerical value of the variable when it is displayed in the Solution 15 Chapter 1 Getting Started window. In this case, EES will select an appropriate number of digits, so the digits column to the right of the A is disabled. Automatic formatting is the default. Alternative display options are F (for fixed number of digits to the right of the decimal point) and E (for exponential format). The display and other defaults can easily be changed with the Default Information command in the Options menu, discussed in Chapter 3. The third Display options column controls the highlighting effects such as normal (default), bold, boxed. The units of the variables can be specified in the Variable Information dialog. The units will be displayed with the variable in the Solution window and/or in the Parametric Table. EES does not automatically do unit conversions but, by default, it is configured to automatically check unit consistency of each equation. The automatic unit checking can be turned off with a control in the Preferences dialog. Unit checking is one the most important capabilities provided by EES. You will rarely want to disable automatic unit checking, but if you do, manual unit checking is provided with the Check Units command in the Calculate menu. In this example, we will not enter any additional units in the Variable Information dialog in order to see the unit checking warnings that EES will raise when the problem is solved. The last two columns allow a variable to be optionally designated as a Key variable and provide a space for a comment. With nonlinear equations, it is sometimes necessary to provide reasonable guess values and bounds in order to determine the desired solution. (It is not necessary for this problem.) The bounds of some variables are known from the physics of the problem. In the example problem, the enthalpy at the outlet, h_2, should be reasonably close to the value of h_1. Set its guess value to 100 and its lower bound to 0. Set the guess value of the outlet specific volume, v_2, to 0.1 and its lower bound to 0. The lower bound of Vel_2 should also be zero. To solve the equation set, select the Solve command from the Calculate menu. An information dialog will appear indicating the elapsed time, maximum residual (i.e., the difference between the left-hand side and right-hand side of an equation) and the maximum change in the values of the variables since the last iteration. When the calculations are completed, EES displays the total number of equations in the problem and the number of blocks. A block is a subset of equations that can be solved independently. EES automatically blocks the equation set, whenever possible, to improve the calculation efficiency, as described in Appendix B. When the calculations are completed, the button will change from Abort to Continue. 16 Getting Started Chapter 1 By default, the calculations are stopped when 100 iterations have occurred, the elapsed time exceeds 60 sec, the maximum residual is less than 10-6 or the maximum variable change is less than 10-9. These defaults can be changed with the Stop Criteria command in the Options menu. If the maximum residual is larger than the value set for the stopping criteria, the equations were not correctly solved, possibly because the bounds on one or more variables constrained the solution. Clicking the Continue button will remove the information dialog and display the Solution window. The problem is now completed since the values of T_2, m_dot_2, and Vel_2 are determined. However, note that EES indicates that there are potential unit problems. EES will display the unit problems if it set to automatically check units. Usually, the unit problems arise because the units of some of the variables have not been specified. EES will automatically provide the units for variables that are on the left side of an equal sign and have not been previously specified. (This capability can be disabled in the Preferences dialog.) Variables with units that have been automatically set will be shown in purple font. Right click on the variable with the purple units to accept or change the automatically provided unit. Even with the automatically-supplied units, unit conversions may still be 17 Chapter 1 Getting Started needed. Even when units have been specified, one or more equations may be dimensionally incorrect. Click the Check Units button to see a list of the unit errors for this example. In this example, unit problem warnings occur because we have not yet set the units of variable Vel_2. The units can be set in several ways. Perhaps the easiest is to right click on one or more variables in the Solution Window and enter the units into the dialog that appears. Alternatively, we could right click on an equation in the Check Units window shown above. The following pop-up menu will appear. The Set Variable Units menu item will bring up variable information for the selected equation. Enter units of m/s for Vel_2, as shown below. Click on the purple units to change or accept them. If there were other equations with unit warnings, you would repeat the process for the other equations until all of the unit problem warnings are removed. When all of the units have been specified, the Solution Window will indicate that there are no unit problems. 18 Getting Started Chapter 1 One of the most useful features of EES is its ability to provide parametric studies. For example, in this problem, it may be of interest to see how the throttle outlet temperature and outlet velocity vary with outlet pressure. A series of calculations can be automated and plotted using the commands in the Tables menu. Select the New Table command. A dialog will be displayed listing the variables appearing in the Equations window. In this case, we will construct a table containing the variables P_2, T_2, Vel_2, and h_2. Click on P_2 from the variable list on the left. This will cause P_2 to be highlighted and the Add button will become active. Now click the Add button to move P_2 to the list of variables on the right. Repeat for T_2, h_2, and Vel_2, using the scroll bar to bring the variable into view if necessary. (As a short cut, you can double-click on the variable name in the list on the left to move it to the list on the right.). The table setup dialog should now appear as shown above. The default table name is Table 1. This name can be changed at this point or later. Click the OK button to create the table. 19 Chapter 1 Getting Started The Parametric Table works much like a spreadsheet. You can type numbers directly into the cells. Numbers that you enter are shown in black and produce the same effect as if you set the variable to that value with an equation in the Equations window. Delete the P_2 = 300 equation currently in the Equations window or enclose it in comment brackets { }. This equation will not be needed because the value of P_2 will be set in the table. Now enter the values of P_2 for which T_2 is to be determined. Values of 100 to 550 have been chosen for this example. (The values could also be automatically entered using Alter Values in the Tables menu, by right clicking on the table cell that shows P_2 and selecting Alter Values from the popup menu, or by using the Alter Values control at the upper right of each table column header, as explained in Chapter 2.) The Parametric Table should now appear as shown below. Now, select Solve Table from the Calculate menu. The Solve Table dialog window will appear allowing you to choose the runs and the table for which the calculations will be done. 20 Getting Started Chapter 1 When the Update Guess Values control is selected, as shown, the solution for the last run will provide guess values for the following run. Click the OK button. A status window will be displayed, indicating the progress of the solution. When the calculations are completed, the values of T_2, Vel_2, and h_2 will be entered into the table. The values calculated by EES will be displayed in blue, bold or italic type depending on the setting made in the Screen Display tab of the Preferences dialog window in the Options menu. The relationship between variables such as P_2 and T_2 is now apparent, but it can more clearly be seen with a plot. Select New Plot Window from the Plot menu. The New Plot Window dialog window shown below will appear. Choose P_2 to be the x-axis by clicking on P_2 in the x-axis list. Click on T_2 in the y-axis list. Select the scale limits for P_2 and T_2, and set the number of divisions for the scale as shown. Grid lines make the plot easier to read. Click on the Grid Lines control for both the x and y axes. When you click the OK button, the plot will be constructed and the plot window will appear as shown below. Once created, there are a variety of ways in which the appearance of the plot can be changed as described in the Plot Windows section of Chapter 2 and in the Plot menu section of Chapter 3. This example problem illustrates some of the capabilities of EES. With this example behind you, you should be able to solve many types of problems. However, EES has many more capabilities and features, such as curve-fitting, uncertainty analyses, complex variables, arrays and animation capabilities. Read on. 21 Chapter 1 Getting Started 22 CHAPTER 2 __________________________________________________________________________ __________________________________________________________________________ EES Windows General Information The information concerning a problem is presented in a series of windows. Equations and comments are entered in the Equations window. After the equations are solved, the values of the variables are presented in the Solution and Arrays windows. The residuals of the equations and the calculation order may be viewed in the Residuals window. Additional windows are provided for the Parametric and Lookup Tables, a diagram and up to 10 plots. There is also a Debug window. A detailed explanation of the capabilities and information for each window type is provided in this section. All of the windows can be open (i.e., visible) at once. The window in front is the active window and it is identified by its highlighted (black) title bar. The figure below shows three overlapped EES windows. The appearance may be slightly for different versions of the Windows operating system. One difference between EES and most other applications is worth mentioning. The Close control merely hides a window; it does not delete it. Once closed, a window can be reopened (i.e., made visible) by selecting it from the Windows menu. 23 Chapter 2 Every window has a number of controls. EES Windows 1. To move the window to a different location on the screen, move the cursor to a position on the title bar of the window and then press and hold the left button down while sliding the mouse to a new location. 2. To hide the window, select the Close command (or press Ctrl-F4) from the control menu box at the upper left of the window title bar. A Hide control is also accessible at the upper right of the title bar. You can restore a hidden window by selecting it from the Windows menu. Window information is NOT lost when the window is closed. 3. The Maximize box at the upper right of the window title bar causes the window to be resized so as to fill the entire screen. The Restore box with an up and down arrow will appear below the Maximize box. Click the Restore box (or select Restore form the Control menu box) to return the window to its former size. 4. The size of any window can be adjusted using the window size controls at any border of the window. To change the size of any window, move the cursor to the window border. The cursor will change to a horizontal or vertical double arrow. Then press and hold the left button down while moving the mouse to make the window larger or smaller. Scroll bars will be provided if the window is made too small to accommodate all the information. 5. Double-clicking the left mouse button on the EES icon at the upper left of the title bar will hide that window. 6. Use the Cascade command in the Windows menu to move and resize all open windows. 7. Many of the windows in the Professional version will display the two-monitor display button at the right of the title bar, adjacent to the minimize, maximize and close buttons. Clicking this button will cause the window to be remain in front of all other EES windows and it will also allow the window to be moved outside of the bounding box provided by the main EES window. This display state is very handy when using two monitors as then, the selected window can be dragged to the second monitor. Only one EES window is allowed to be in the 2-monitor display format at any one time. The window will return the window to its normal display state if the two-monitor display button for another window is clicked or if the button is clicked. 24 EES Windows Chapter 2 Equations Window The Equations window operates very much like a word processor. The equations that EES is to solve are entered in this window. Editing commands, i.e., Cut, Copy, Paste, are located in the Edit menu and can be applied in the usual manner. Clicking the right mouse button on selected text in the Equations window will bring up editing commands in a popup menu. Additional information relevant to the Equations window follows. 1. Blank lines may be used to make the Equations window more legible. 2. Comments are enclosed in braces {comment} or in quote marks "another comment" and may span multiple lines. Nested comment fields within braces are permitted. Comments within quote marks will appear in the Formatted Equations window. Comments that begin with and exclamation mark ! will appear in a different font or color as determined by the settings made with the Preferences command in the Options menu. Comments may be of any length. The comments will automatically line break to fill the Equations window if the Wrap Long Lines option in the Preferences Equations tab is selected. Note that the Wrap Long Lines option can also be turned on or off by clicking on Wrap: in the Equations window status bar. The Formatted Equations window will also line break the comments in the display window and in the printed output. Any line in the Equations Window that begins with // will be ignored as if the entire line is a comment. 3. Equations are normally entered one per line, terminated by pressing the Return or Enter keys. Multiple equations may be entered on one line if they are separated by a semicolon2. Long equations are accommodated by the provision of a horizontal scroll bar which appears if any of the equations is wider than the window. Earlier versions of EES required that equations consist of 255 or fewer characters. This limitation no longer exists, but use of shorter equations is recommended as it assists in debugging in clarity 4. Equations may be entered in any order. The order of the equations has no effect on the solution, since EES will block the equations and reorder them for efficient solution as described in Appendix B. 5. The order of mathematical operators used in the equations conforms to the rules used in FORTRAN, Basic, C or Pascal. For example, the equation X = 3 + 4 * 5 will result in X having a value of 23. The caret symbol ^ or ** can be used to indicate raising to a power. Arguments of functions are enclosed in parentheses. EES does not require a variable to appear by itself on the left-hand side of the equation, as does FORTRAN and most other programming languages. The above equation could have been entered as (X – 3) / 4 = 5 2 If a comma is selected as the Decimal Symbol in the Windows Regional Settings Control Panel, EES will recognize the comma (rather than a decimal point) as a decimal separator, the semicolon (rather than the comma) as an argument separator, and the vertical bar | (rather than the semicolon) as the equation separator. 25 Chapter 2 EES Windows 6. Upper and lower case letters are not distinguished. EES will (optionally) change the case of all variables to match the manner in which they first appear in the Equations window depending on the settings selected in Preferences dialog in the Options menu. However, this change is made only when an equation is first compiled or modified or when Check/Format command in the Calculate menu is issued. 7. Variable names must start with a letter and consist of any keyboard characters except (‘|)*/+-^{ } ":;. The maximum variable length is 30 characters. String variables hold character information and are identified with a $as the last character in their names, as in BASIC. Array variables are identified with square braces around the array index or indices, e.g., X[5,3]. The quantity within the braces must be a number, except within the scope of the sum, product or Duplicate commands. As a general rule, variables should not be given names that correspond to those of built-in functions (e.g., pi, sin, enthalpy). 8. As you enter an equation, an unmatched open or close parenthesis will be displayed in bold font. 9. The commercial and educations versions of EES have an upper limit of 6000 variables. The Professional version can have 12,000 variables. 10. EES compiles equations into a compact stack-based form. The compiled form is saved in memory so that an equation needs to be compiled only when it is first used or when it is changed. Any error detected during the compilation or solution process will result in an explanatory error message and highlighting of the line in which the problem was discovered. 11. Equations can be imported or exported from/to other applications by using Cut, Copy and Paste commands in the Edit menu. The Merge and Load Library commands in the File menu and the$INCLUDE directive may also be used to import the equations from an existing file. The Merge command will import the equations from an EES or text file and place them in the Equations window at the cursor position. Equations imported with the $INCLUDE directive will not appear in the Equations window. 12. Clicking the right mouse button in the Equations window will bring up a pop-up menu that will allow commenting (or uncommenting), with either of the two types of comments. The menu also provides options for cutting, yellow highlighting, copying or printing of the selected text. A units list is also available in the pop-up menu to simplify entering the units of constants. 13 If EES is configured to operate in complex mode, all variables as assumed to have real and imaginary components. The complex mode configuration can be changed in the Preferences Dialog (Options menu) or with the$Complex On/Off directive. 14. Selecting a variable in the Equations window will cause a small hint window to appear just below the variable. The hint window will show the value of the variable, if calculations have been completed, and variable unit. The variable can be easily selected by double-clicking. This capability makes it unnecessary to refer to the Solutions window to determine values of EES variables. Right-clicking on a selected variable will 26 EES Windows Chapter 2 bring up a pop-up menu that has Variable Info as one of the menu items. Selecting Variable Info will bring up a small dialog window in which the format and units of the variable can be entered. This is perhaps the easiest way to enter the units of a variable. 15. Active hypertext can be entered into the Equations window. Obviously, this should only be done within comments. EES will automatically identify hypertext links that begin with http:\\, https:\\ or file: In addition, a hypertext link that begins with \\EES_ following by the name of an EES window is understood to be a link to that window. Clicking on a link will move the focus to that location, opening another program if necessary. A summary of the recognized links is shown below: http:\\fchart.com {open a browser and point it at the web page that follows http:} https:\\fchart.com {open a browser and point it at the web page that follows https:} file:c:\ees32\ees_manual.pdf {open the local file with a filename that follows file: and start the appropriate application} \\EES_Solution {open the Solution window and bring it to the front} \\EES_Format {open the Formatted equations window and bring it to the front} \\EES_Plot {open the Plot window and bring it to the front} \\EES_Plot3 {open the Plot window and bring the 3rd plot to the front} \\EES_Parametric {open the Parametric table and bring it to the front} \\EES_Lookup {open the Lookup table and bring it to the front} \\EES_Array {open the Array table and bring it to the front} \\EES_Integral {open the Integral table and bring it to the front} \\EES_Report {open the Report window and bring it to the front} \\EES_Diagram {open the Diagram window and bring it to the front} \\EES_Residual {open the Residuals window and bring it to the front} \\EES_Calculator {open the EES Calculator window and bring it to the front} \\EES_Solve {solve the current set of equations} \\EES_SolveTable {apply the Solve Table command in the Calculate menu} \\EES_MinMax {apply the MinMax command in the Calculate menu} \\EES_MinMaxTable {apply the MinMax Table command in the Calculate menu} 16. Constants representing time may be entered in Time Format. For example, a time of 9 hours, 30 minutes and 10 seconds may be entered as 9:30:10. EES will internally convert this value to hours and associate units of hours with its value. 17. A status bar is provided at the bottom of the Equations window showing the position of the cursor, and settings for word wrap, Caps lock, Insert mode, unit system, warnings, unit checking, and complex math mode. Clicking on any of the settings in the status bar 27 Chapter 2 EES Windows toggles their settings. The status bar can be disabled by clicking on the X in the leftmost panel area. 28 EES Windows Chapter 2 Formatted Equations Window The Formatted Equations window displays the equations entered in the Equations window in an easy-to-read mathematical format as shown in the sample windows below. Note that comments appearing in quotes in the Equations window are displayed in the Formatted Equations window but comments in braces are not displayed. An examination of the Formatted Equations Window will reveal a number of EES features to improve the display, in addition to the mathematical notation. Array variables, such as B[1] are (optionally) displayed as subscripted variables. Sums and integrals are represented by their 29 Chapter 2 EES Windows mathematical signs. If a variable name contains an underscore, the underscore will signify the beginning of a subscript, as in variable G_2. However, note that although G[2] and G_2 will display in the same manner in the Formatted Equations Window, they are different variables with different properties. The index of array variables, e.g., G[2], can be used within the scope of Duplicate statements, or with the Sum and Product functions. In addition, the calculated value of G[2] can be displayed in the Arrays Window. Placing _dot, _ddot, _bar, _hat or _tilde after a variable name places a dot, double dot, bar, hat (^) or tilde (~) centered over the name. The _infinity results in a subscript with the infinity symbol (∞). A vertical bar character in a variable name signifies the start of a superscript. For example, G|o will display as G o . Variables having a name from the Greek alphabet are displayed with the equivalent Greek letter. For example, the variable name beta will display as ß and mu will display as a µ. If the variable name in the Equations window is entered entirely in capital letters, and if the capital Greek letter is distinct from the English alphabet, the capital Greek letter will be used. For example, the variable name GAMMA will be displayed as Γ. The variable JTHETA will be displayed as a J in Symbol font which appears as a theta with a “curly” tail. A special form is provided for variables beginning with DELTA. For example, DELTAT displays as ΔT. Capital BETA looks just like a B, so EES will display the lower case equivalent, i.e., ß. Both the equations and comments will be formatted using these special symbols. The formatted equations and comments appearing the Formatted Equations window can be moved to other positions if you wish. To move an equation or comment, move the cursor to the item and then press and hold the left mouse button down while sliding the equation or comment to a new location. The formatted equations can be displayed with the units of constants and/or variables shown. Displaying the units makes it easier to identify a units inconsistency in the equations. To change the display setting for units of constants and/or variables, right click anywhere in the Formatted Equations window. The popup menu shown below will appear with menu options for displaying units. The formatted equations and comments are internally represented as Windows MetaFilePict items or pictures. You can copy one or more equation pictures from this window to other 30 EES Windows Chapter 2 applications (such as a word processor or drawing program). In addition, the equations can be copied in either LaTeX or MathType 5 compatible formats in the Professional version. To copy an equation, first select it by clicking the left mouse button anywhere within the equation rectangle. A selected equation or comment will be displayed in inverse video. You may select additional equations. Alternatively, the Select All Equations command in the Edit menu can be used to select all of the equations and comments which are currently visible in the Formatted Equations window. Next, right-click to bring up the following popup menu and select on of the three copy commands at the bottom of this menu to place the equation on the Clipboard in the desired format. The text in the Formatted Equations window cannot be edited. However, clicking the right mouse button on an equation in the Formatted Equation window will bring up the popup menu shown above. Selecting the first command in this menu will cause the display focus to move to the Equations window with the cursor positioned on the equation that was selected in the Formatted Equations window. 31 Chapter 2 EES Windows Solution Window The Solution window will automatically appear in front of all other windows after the calculations, initiated with the Solve or Min/Max commands in the Calculate menu, are completed. The values and units of all variables appearing in the Equations window will be shown in alphabetical order using as many columns as can be fit across the window. The format of the variables and their units can be changed using the Variable Info command in the Options menu, or more simply, directly from the Solution window. Clicking the left mouse button on a variable selects that variable which is then displayed in inverse video. Clicking the left mouse button on a selected variable unselects it. Double-clicking the left mouse button (or clicking the right mouse button) brings up the Format Variable dialog window. The changes made in the Format Variable dialog are applied to ALL selected variables. Pressing the Enter key will also bring up the Format Variable dialog window. The numerical format (style and digits) and the units of the selected variables can be selected in this dialog window. When configured in Complex mode, an additional formatting option is provided for displaying the variable in rectangular or polar coordinates. The selected variables can also be highlighted (with underlining, bold font, foreground (FG) and background (BG) colors, etc.) or hidden from the Solution window. If a variable is hidden, it can be made visible again with the Display controls in the Variable Info dialog window. Additional information pertaining to the operation of the Solution window follows. 1. The Solution window is accessible only after the calculations are completed. The Solution menu item in the Windows menu will be dimmed when the Solution window is not accessible. 2. The unit settings made with the Unit System command in the Options menu will be displayed at the top of the Solution window if any of the built-in thermophysical property or trigonometric functions is used. 32 EES Windows Chapter 2 3. If any of the variables have been designated to be key variables, a separate tabbed window will display these variables with optional comments. The order in which variables appear is not alphabetical, as in other Solution window displays, but instead by the order in which key variables are designated. The order can be changed by dragging a variable to the line that it should appear. 4. The Solution window will normally be cleared and hidden if any change is made in the Equations window. However, there is an option in the Preferences dialog of the Options menu to allow the Solution window to remain visible. 5. The number of columns displayed on the screen can be altered by making the window larger or smaller. 6. If EES is unable to solve the equation set and terminates with an error, the name of the Solution window will be changed to Last Iteration Values and the values of the variables at the last iteration will be displayed in the Solution window. Variables that were not evaluated are shown in gray. 7. When the Solution window is foremost, the Copy command in the Edit menu will appear as Copy Solution. The Copy Solution command will copy the selected variables (shown in inverse video) to the clipboard both as text and as a picture. The text will provide for each variable (selected or not) a line containing the variable name, its value, and its units. The picture will show only those variables which are selected in the same format as they appear in the Solution window. The Select Display command in the Edit menu will select all variables currently visible in the Solution Window. (If you wish to force a black and white picture, hold the Shift key down when you issue the Copy Solution command.) Both the text and the picture can be pasted into another application, such as a word processor. Most word processors will, by default, paste the text. To paste the picture instead of the text, select the Paste Special command and select picture. 8. If the Display subscripts and Greek symbols option in the General Display tab of the Preferences dialog is selected, EES will display subscripts and superscripts of variable units. For example, m^2 will appear as m2. An underscore character is used to indicate a subscript so lb_m will appear as lbm. 9. If the Show function/procedure/module values option in the General Display tab of the Preferences dialog is selected, EES will display the most recent values of local variables in EES Functions, Procedures, Modules and Subprograms in separate tabbed windows within the Solution window. 33 Chapter 2 EES Windows Arrays Window EES allows the use of array variables. EES array variables have the array index in square brackets, e.g., X[5] and Y[6,2]. In most ways, array variables are just like ordinary variables. Each array variable has its own guess value, lower and upper bounds and display format. However, simple arithmetic operations are supported for array indices so array variables can be more convenient in some problems as discussed in Chapter 7. The values of all variables including array variables are normally displayed in the Solution window after calculations are completed. However, array variables may optionally be displayed in a separate Arrays window, rather than in the Solution window. This option is controlled with the Place array variables in the Arrays window check box in the Preferences dialog (Options tab) in the Options menu. If this option is selected, an Arrays window such as that shown below will automatically be produced after calculations are completed showing all array values used in the problem with the array index value in the first column. Clicking the Sort button will arrange the columns in alphabetical order. The positions of the columns can be changed by dragging the column header cell to the desired column position. The values in the Arrays window may be plotted using the New Plot Window command in the Plot menu. Part or all of the data in the Arrays window can be copied to another application by selecting the range of cells of interest followed by use of the Copy command in the Edit menu. If you wish to include the column name and units along with the numerical information in each column, hold the Ctrl key down while issuing the Copy command. The format of values in any column of the Arrays window can be changed by clicking the right mouse button on the array name at the top of the column. The following dialog window will appear in which the units, display format and column position can be changed. 34 EES Windows Chapter 2 Note that you can enter a number in the column number field or use the up/down arrows to change its value. If the value you enter is greater than the number of columns in the table, the column will be positioned at the right of the table. The sum, average, and standard deviation of the numbers in the selected column of the table are also shown in this display. Selected columns in the Arrays Table can be hidden by right-clicking on the column header and selecting Properties from the pop-up menu. In the Properties dialog, set the format Style type to be Hidden. 35 Chapter 2 EES Windows Residuals Window The Residuals window indicates the equation blocking and calculation order used by EES, and the status of the unit checking, in addition to the relative and absolute residual values. The absolute residual of an equation is the difference between the values on the left and right hand sides of the equation. The relative residual is the magnitude of the absolute residual divided by the value of left side of the equation.3 The relative residuals are monitored during iterative calculations to determine when the equations have been solved to the accuracy specified with the Stopping Criteria command in the Options menu. Consider, for example, the following set of six equations and six unknowns. EES will recognize that these equations can be blocked, i.e., broken into two or more sets, as described in more detail in Appendix B. The blocking information is displayed in the Residuals window. Variables having values that can be determined directly, i.e., without simultaneously finding the values of other variables, such as G in the example above, are determined first and assigned to Block 0. Note the EES has placed a question mark by this equation, since its unit consistency is suspect. Once G is known, H can be determined. The order in which these individual equations are solved in Block 0 is indicated by the order in which they appear in the Residuals window. After solving all equations in Block 0, EES will 3 If the value of the left hand side of an equation is less than 1E-20, the absolute and relative residuals assume the same value. 36 EES Windows Chapter 2 simultaneously solve the equations in Block 1, then Block 2, and so on until all equations are solved.4 The first and third equations in the example above can be solved independently of other equations to determine X and Y and are thereby placed in Block 1. Similarly, the second and fourth equations, which determine A and B, are placed in Block 2. With X, Y, A, and B now known, Z can be determined, so it appears in Block 3. Note that the variable(s) that are determined by the equation(s) in each block are shown in bold font. The Residuals window will normally be hidden when any change is made in the Equations window. This automatic hiding can be disabled with the Display Options command in the Options menu. It is possible to display the Residuals window in a debugging situation. If the number of equations is less than the number of unknowns, EES will not be able to solve the equation set, but the Residuals window can be made visible by selecting it from the Windows menu. Normally, the block numbers appear in sequential order. When one or more equations are missing, EES will skip a block number at the point in which it encounters this problem. The equations in the following blocks should be carefully reviewed to determine whether they are correctly and completely entered. The information in the Residuals window is useful in coaxing a stubborn set of equations to converge. An examination of the residuals will indicate which equations have been solved by EES and which have not and how many times each equation was evaluated in the process of solving the set. The status bar at the bottom of the Residuals window shows the values of variables in the equation under that mouse cursor. The block number will be displayed in bold font for equations that have residuals greater than the tolerance specified with the Tolerance command (Options menu). In this way, the block of equations that EES could not solve can be identified. Check these equations to be sure that there is a solution. You may need to change the guess values or bounds for the variables in this block using the Variable Info command in the Options menu. Doubling-clicking the left mouse button (or clicking the right mouse button) on an equation in the Residuals window will cause the Equations window to be brought to the front with the selected equation highlighted. Use the Find command in the Search menu to help locate the equations. The entire contents of the Residuals window will be copied as tab-delimited text to the Clipboard if the Copy command is issued when the Residuals window is foremost. 4 Variables specified in the Diagram Window are identified with a D rather than a block number. See the Diagram Window section. In Complex mode, each equation is shown twice, once for the real part identified with (r) and again for the imaginary component labeled with (i) 37 Chapter 2 EES Windows Parametric Table Window The Parametric Table window contains one or more Parametric Table(s). A Parametric table operates somewhat like a spreadsheet. Numerical values can be entered into any of the cells. Entered values, e.g., the values in the P2 column in the above table, are assumed to be independent variables and are shown in normal type in the font and font size selected with the Preferences command (Options menu). Entering a value in the Parametric Table produces the same effect as setting that variable to the value with an equation in the Equations window. Dependent variables will be determined and displayed in the table in blue, bold type, or italics (depending on the choice made with the Preferences command) when the Solve Table or Min/Max Table command in the Calculate menu is issued. 1. A Parametric table is created using the New Parametric Table command in the Tables menu. The variables that are to appear in the table are selected from a list of variables currently appearing in the Equations window. Each new table is given a name that appears on a tab at the top of the Parametric Window. Clicking the left-mouse button on the tab brings the corresponding Parametric Table to the front. Clicking the right-mouse button on the tab brings up the following dialog with controls that allow the tab position to change, or to duplicate, delete, or save the table to an external file. 38 EES Windows Chapter 2 2. Each row of the Parametric Table is a separate calculation. The number of rows is selected when the table is generated, but may be altered using the Insert/Delete Runs command in the Tables menu. The maximum number of rows in the Commercial version is 6500. There is no limit to the number of rows in the Professional version. 3. Variables may be added to or deleted from an existing Parametric Table using the Insert/Delete Vars command in the Tables menu. One or more columns can be deleted more simply by right-clicking in the column header and selecting Delete from the popup menu. 4. The initial order in which the columns in the Parametric Table appear is determined by the order in which the variables in the table were selected in the New Parametric Table dialog. To change the column number order, click the left mouse button in the column header cell and drag it to the desired column position. Alternatively, click the right mouse button in the column header cell (but not on the alter values control at the upper right). A pop-up menu will appear with Properties as one of the menu items. Select the Properties menu item. A dialog window will appear as shown below in which the column number can be changed be clicking the up or down arrows to the right of the column number or by directly editing the column number. The display format, units, column width, and column background color can also be entered or changed at this point. 39 Chapter 2 EES Windows 5. Values can be automatically entered into one or more Parametric Table(s) using the Alter Values command in the Tables menu. Alternatively, right-clicking in the column cell header and selecting Alter values from the pop-up menu or clicking the left mouse button on the control at the upper right of the column header cell will bring up the dialog window shown below which provides the same automatic entry somewhat more conveniently in addition to providing additional capabilities. In some situations, it is necessary to fill a table with a pattern of some type. For example, you may wish to enter 1, 2, 3, 4, and 5 in the first 5 rows of the column and then repeat these values in the next five rows and so on down the table. Alternatively, you may wish to enter 1, 1, 1, 1, 1 in the first 5 rows followed by 2, 2, 2, 2, 2 in the next five rows and so on. The capability to enter patterns of this type is provided with the controls that are above the OK and Cancel buttons. Click the check box to enable the controls. Select Repeat Pattern every to enter a repeating pattern of the form 1, 2, 3, 4, 5. Select Apply Pattern Every to enter a sequence such as 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, etc. The pattern is specified by the first value and the last value / increment / multiplier. The pattern repeats every N rows where N is the value you provide. The pattern is applied to rows indicated with the First Row and Last Row controls. 6. A green 'go' triangle is displayed in the upper left cell of the Parametric table. Clicking the left mouse button in this triangular area will initiate the foremost Parametric Table calculations for the rows indicated below the triangle. The row range is that selected during the last use of the Solve Table dialog. To select a different range, click the left mouse button in the first row. Hold the Shift key down and then click the mouse in the last row. Continue to hold the Shift key down while clicking in the green triangle. 7. A Sum row which displays the sum of the values in each column may be hidden or made visible using the 'Include a Sum row in the Parametric table’ control provided in the Preferences dialog window (Options tab) in the Options menu. 8. Clicking the left mouse button in the leftmost column of a row in any table will select all of the cells in that row. If the mouse button is held down while the clicking in leftmost 40 EES Windows Chapter 2 column of other rows, these rows will be added to the selection. Rows can also added by holding the Shift key down while clicking in the leftmost column. All of the cells in a column can be selected in a similar manner by clicking the left mouse button in the column header. 9. Right-clicking in Parametric, Lookup, Arrays, or Integral table windows will bring up the following pop-up menu allowing the current selection to be cut, copied, or printed. This option provides a convenient way to print a specified section of a table. The Copy (E-format) will copy values with 12 significant figures so that they can be pasted to another application with no loss in precision. Alternatively, holding the Shift key down while copying a selection from the Parametric or Lookup tables will cause all numbers to be copied in E-format. 10. Right clicking in the Row column of any table brings up a menu that allows a back color or border to be associated with the row. Also rows and be inserted or deleted from the Parametric and Lookup tables. 11. A right-click in the cell header will bring up the following popup menu. The Alter Values menu option will allow values to changed as described in item 5 above. The Properties menu item brings up the Format Column dialog that allows the format, units, and other information in a column to be edited, as indicated in item 3 41 Chapter 2 EES Windows above. The Sort menu option allows the data in the column to be sorted in ascending or descending order. The sort can be applied to a single column or to all columns table. 12 A Parametric Table can be used to solve differential equations or integrals. See Chapter 7 for additional information. 13. The TableValue function returns the value of a table cell at a specified row and column. 14. The TableRun# function returns the row of the table for which calculations are currently in progress. 15. The TableName$function returns the name of the Parametric table (as displayed on the tab in the Parametric window) that is currently in use. 16. The independent variables in the Parametric Table may differ from one row to the next. However, when the independent variables are the same in all rows, EES will not have to recalculate the Jacobian and blocking factor information and can thus do the calculations more rapidly. 17. Tabular data may be imported or exported from the Parametric Table via the Clipboard using the Copy and Paste commands in the Edit menu. To copy data from any of the EES tables, click the mouse in the upper left cell. Hold the Shift key down and click in the lower right cell, using the scroll bar as needed. The selected cells will be shown in inverse video. (When the Shift key is released, the upper left cell that has the focus will return to normal display. However, even though it may not be displayed in inverse video, the upper left cell is selected and it will be placed on the clipboard with other cells when the Copy command is issued.) Use the Select All command in the Edit menu to select all of the cells in the table. The data are placed on the clipboard with a tab between each number and a carriage return at the end of each row. With this format, the table data will paste directly into a spreadsheet application. If you wish to include the column name and units along with the numerical information in each 42 EES Windows Chapter 2 column, hold the Ctrl key down while issuing the Copy command. The Copy command is also accessible from a pop-up menu by right-clicking the mouse in a selected cell. 18. An entire table can be duplicated or deleted by right-clicking on its tab at the top of the table window. A small dialog will appear having a Duplicate and a Delete button. The Delete cannot be undone so be careful. 19. The tabs used to select different table windows can be 'dragged' to a different tab location. This method of reordering the tabs is quicker than the alternative of rightclicking on each tab and specifying the tab position. 43 Chapter 2 EES Windows Lookup Table Window A Lookup Table provides a means of using tabular information in the solution of the equations. A Lookup Table is created using the New Lookup Table command in the Tables menu. There is no limit, other than available memory, on the number of Lookup Tables that can be placed in the Lookup Table Window. Each Lookup table is associated with a table name that appears on the tab at the top of the Lookup Table Window. The number of rows and columns in the table are specified when the table is created and may be altered with Insert/Delete Rows and Insert/Delete Cols commands in the Tables menu or by right-clicking in the row or column headers. All Lookup Tables are saved with other problem information when the EES file is saved. In addition, a Lookup Table may be saved on a disk (separately from the EES file) using the Save Lookup command in the Tables menu. A .LKT filename extension is used to designate EES Lookup files. Lookup files can also be saved in ASCII format with a .TXT or .CSV filename extension. The Lookup table may then be accessed from other EES programs in any of these formats. The Interpolate commands provide linear, quadratic or cubic interpolation or extrapolation of the data in the Lookup Table. See Chapter 4 for details. In addition, the Lookup, LookupCol, and LookupRow functions allow data in a Lookup Table to be linearly interpolated (forwards and backwards) and used in the solution of the equations. The Lookup Table may either reside in the Lookup Table Window or in a previously-saved Lookup File with a .LKT, .TXT, or .CSV filename extension, as explained in more detail in Chapter 4. A sample Lookup Table is shown above. The column number is displayed in small type at the upper left of each column header cell. The column number can be used to specify a specific column when used with the Lookup functions. However, the Lookup functions will also accept ‘ColumnName’ in place of the column number where ‘ColumnName’ is the name of the column shown in the column heading surrounded by single quote marks.5 The 5 EES will also accept #ColumnName in place of the column number. 44 EES Windows Chapter 2 column names are initially Column1, Column2, etc. but these default names can be changed by clicking the right mouse button in the header cell and selecting Properties from the popup menu that appears. The column title can be changed and units for the values in the column may be specified. The Format controls allow the data in each column of the table to be displayed in an appropriate numerical format. A control is provided to change the background color for each column. The column width and position may also be changed by either clicking the up or down arrows to the right of the column number or by editing the number directly. Data can be pasted into a Lookup Table via the Clipboard from another application, such as a spreadsheet. The Paste command will initiate the paste, starting in the row and column in which the cursor is located. However, the names of each column and the units cannot be pasted in this manner. The Paste Special command has been developed to provide this capability. The Paste Special command is accessed by clicking in the Paste Special box in the upper left of the table. Doing so will provide a choice of pasting the values, the values and column names, and the values, column names and units, as shown in the figure below. 45 Chapter 2 EES Windows Data may be automatically entered into the Lookup table by clicking on the control at the upper right of the column header cell, as described for the Parametric table. Values can be entered into a column of a Lookup tables using an equation, similar to capability provided in spreadsheet programs. The equation can refer to values in other columns of the table and to defined EES variables. All of the built-in functions can be employed in the equations. Values in a column are represented in the equations with #n where n is the column number. For example, to convert temperatures in °C in column 1 of the Lookup table to values in K in the selected column, enter convertTemp(C,K,#1). Hold the Shift key down when issuing the copy command if you wish to copy the column names and units with the other numerical information on the Clipboard. Data may be interchanged between the Parametric and Lookup Table windows. Data in the table can be sorted by right-clicking in the column header for the column that is to control the sort and selecting Sort from the popup menu. One or more Lookup Tables can be deleted from the Lookup Table Window, if desired, with the Delete Lookup Table menu item in the Options menu. Lookup Table files saved with a .LKT, .TXT , or .CSV filename extension can not be deleted from within EES. Integral Table Window An Integral Table is automatically generated during calculations when one or more equation-based Integral functions are in use and the$IntegralTable directive is supplied. The Integral Table holds intermediate values of specified variables that occur during the numerical integration process. The values in this table can be plotted using the New Plot Window and Overlay Plot commands in the Plot mneu. The values can also be printed or copied in the same manner as for data in the Parametric table. When the $IntegralTable directive is used with the Solve Table command, an Integral Table is produced for each run (i.e., row) of the Parametric Table. All of these Integral tables appear in the Integral Table window and a set of tabs is provided at the top of the window to facilitate access to any one of the tables. See the$IntegralTable directive in Chapter 7 for more information. 46 EES Windows Chapter 2 Diagram Window The Diagram window serves several functions. First, it provides a place to display a graphics and text relating to the problem that is being solved. For example, a schematic diagram of a system identifying state point locations can be displayed in the Diagram window to help interpret the equations in the Equations window. Second, the Diagram window can be used for to provide convenient input and output of information and for report generation. In the Professional version, 'hot areas' can be defined that, when clicked, open additional child Diagram windows. A Calculate button can be placed on Diagram and child windows to conveniently initiate the calculations. Link buttons can be put on the Diagram that display plots, save or load input values, or start other programs. A Help button can be used to access help information from a text file, Windows help file, or web site. Shown below is a typical diagram window. Third, the Diagram window provides the focus for the animation capabilities in EES. Creating the Diagram There are two ways to place objects on the Diagram window. First, a graphical or text objects can be created in any drawing program that produces an object drawing such as Corel Draw, Designer, or PowerPoint. Select and copy the item(s) in the drawing application and then use the Paste command to place them into the Diagram window. A scanned image in bitmap format can also be used as the diagram provided that it is copied as 47 Chapter 2 EES Windows an picture, rather than a bitmap. An easy way to convert the bitmap into a picture is to paste the bitmap into PowerPoint, PaintBrush or other programs that convert graphical images. Then copy the image from this program into the Diagram window. A second way to create a drawing is to use the drawing tools provided on the Diagram window toolbar. The toolbar provided graphic primitives such as lines/arrows, circles, and rectangles. The characteristics of these graphic objects can be changed by right-clicking or double-clicking the mouse button on the object while the toolbar is visible. The two methods of creating a drawing can be combined. For example, you can position a rectangle on top of a scanned image. Graphic objects generated in either manner are saved along with all other problem information. Development and Application Modes The Diagram window and child Diagram windows operate in two modes. When the tool bar (shown below) is visible, the Diagram window is in development mode. The tool bar can be made visible or hidden using the Show/Hide Diagram Tool Bar command or the Diagram window speedbutton. In the development mode, all objects such as the picture, text, and graphic objects (lines/arrows, rectangles, ellipses) added to the Diagram window, can be moved, modified, or deleted as indicated below. Input variables are disabled in development mode and calculations initiated with the Calculate button are suppressed. A statusbar is visible at the bottom of the Diagram window in development mode. The statusbar shows the cursor position, Diagram window identity and information about the object that the cursor is positioned on. When the tool bar is hidden, the Diagram window is in application mode. The tool bar can be hidden by clicking on the X in its title bar or by selecting the Show/Hide Diagram Tool Bar command. In application mode, it is not possible to move any of the objects or change their display characteristics. Input variables are enabled and calculations can be initiated using the optional calculate button or the commands in the Calculate menu. 48 EES Windows Chapter 2 The Copy command in the Edit menu can be used to copy the either the entire contents of the Diagram window or selected items to the Clipboard. The copied information on the clipboard can then be pasted into a word processor or other application, into a different child Diagram window, or into the Diagram window of another instance of EES. In general, Input/Output text items should not be copied into another instance of EES since they contain specific pointers to EES variables that will not be appropriate in the copy. Use the Select All and Delete command to remove the entire contents of a Diagram window. Right-clicking on the Diagram window will bring up a popup menu that allows the size of the window contents to be changed. Moving the Diagram Selected items in the Diagram window can be moved in development mode by pressing and holding the left mouse button down anywhere within a selected item while sliding the mouse. The items can also be moved one pixel at a time with each press of the arrow keys. Use the Select All command in the Edit menu to move the all of the contents of the Diagram Window to a new position. Resizing the Diagram In development mode, the contents of the Diagram window can be resized by doubleclicking the left mouse button (or clicking the right mouse button) anywhere within the Diagram window (or child Diagram window) except on a text, graphic object or button. After a positive confirmation, the graphical and text items will be proportionally resized to fit in the Diagram window. The contents of the Diagram window can be made larger or smaller by first changing the size of the Diagram window itself by dragging its lower left corner to a new location and then double-clicking in the window to resize the contents. The aspect ratio of Diagram window information is not changed it is resized. Buttons that are placed on the Diagram window can be resized independently by holding the Ctrl-key down while using the arrow keys. For example, to increase the width of a button, click on the button to select it (in development mode) and then press the right arrow key while holding the Ctrl key down. Each right arrow press increases the width of the button by one pixel. The left arrow key reduces the width. The up and down arrow keys increase and decrease the button height, respectively. Adding and Moving Text on the Diagram Window The Add Text button on the Diagram window toolbar allows text to be placed anywhere on the Diagram window. Four different types of text may be selected using the radio buttons at the upper left of the Add Text dialog window. Selecting the Text radio button will cause the window to appear as shown below, in which the text and its characteristics can be specified. The formatting buttons to the right of the text type radio buttons simply entry of subscripts, superscripts, and symbols. The text will initially appear in a default position within the 49 Chapter 2 EES Windows Diagram window when the dialog is dismissed. It can then be dragged to a new position by pressing and holding the left mouse button down while sliding the text to the desired location. Alternatively, selected text items can be moved by pressing the arrow keys. The text or any of its characteristics can later be changed by double-clicking the left mouse button (or by clicking the right mouse button) while the cursor is positioned over the text. Clicking the Input or Output radio buttons changes the dialog window display so that a list of currently defined variables replaces the text edit box, as shown. Select the variable by clicking on its name in the list. Both Input and Output variables values are displayed on the diagram with the option of also displaying the variable name and unit string. An Output variable displays the value of the selected variable calculated during the previous calculation. An Input variable will be displayed with the value enclosed in a rectangle. This value can be edited and it provides the same function as an equation in the Equations window which sets the variable to a value. If a string variable (identified with a $character as the last character in the variable name) is selected for an Input variable, EES will provide the option of selecting the variable from a pull-down list of string constants that you provide. For example, the Diagram window shown at the start of this section employs pull-down lists for the unit system and type of compressor data. The selection from the pull-down menu is assigned to the string variable. 50 EES Windows Chapter 2 String variables can be used for many purposes including the names of fluids as described in Chapter 7. String variables can also be used to enter EES equations, as described below. Assuming that the Diagram window is not hidden, EES will first examine the Diagram window to see which variables, if any, are to be input from the Diagram window when the Solve or Min/Max commands (Calculate menu) are issued.. The Solve Table and Min/Max Table commands provide a check box to indicate whether Diagram window information should be used. A value which is set in the Diagram window cannot also be set in the Equations window. After the calculations are completed, the newly-calculated values of the Output variables will be displayed on the Diagram window. Output values will display in gray-colored text if the value is not currently defined. The Formatted text button allows a formatted text item be placed in the Diagram window and in child diagram windows. A formatted text item can consist of one or more lines of formatted text with embedded font, font size, font style, and font color information. The text item can include line breaks and tabs. The text item can be a table, copied from a spreadsheet program. In addition, EES variables can be included in the text so that the current value of the variable is automatically displayed. The Professional version of EES provides a field to enter the name of the text item as shown in the above dialogs. Assigning a name to a text item is useful only when the item is to have 51 Chapter 2 EES Windows its attributes determined by the value of EES variables, such as for animation. If a name is provided, EES will create variables and associate them with this text object. For example, if the name of the text item is Area as shown in the above dialog, the following EES variables will be created (if they do not already exist) after pressing the OK button. Area.left Area.top Area.color Area.Hide These variables can be set in the Equations window or in Check Boxes, Radio Groups, or Drop-Down lists in the Diagram window. Note that items can be hidden or shown by entering Name.hide or Name.show. A complete equation with an equal sign is not required. Creating a Formatted Text Item Formatted text items can be created or edited when the Diagram window is in Development mode. There are two ways to create a new item. One way is to click the Text button on the toolbar. This action will bring up the Add Diagram Text Item dialog. Click the Formatted text button at the upper left and enter the text in the large edit box that appears. An easier way is to simply copy the text from any application such as a word processor or spreadsheet program and then use the EES Paste command while the Diagram window is in front. If a formatted text item is selected, the Paste command will add the text to the existing text item. Otherwise a new text item will be created. Often applications place information on the Clipboard in more than one format. For example formatted text copied from WORD may exist on the Clipboard both as a picture and as text. In this case, EES will present the a dialog showing the possible paste formats, as shown below. Selecting Text will result in just text being pasted. All formatting and pictures will be stripped. The Enhanced Metafile and Picture formats will paste a picture of the information, just as it appears in the application it was copied from. The picture does not allow editing of the text. The Linked Object format (Professional version) will paste the selection in manner in which it can be edited by the original program. Double-clicking on the item after it is pasted into the Diagram window while in Development mode will start the original program and copy the item into that program where it can be edited. Closing the original program will place the revised selection into the Diagram window, replacing the original selection. 52 EES Windows Chapter 2 Note that a section of a spreadsheet can be inserted into the EES Diagram window in this manner. Resizing and Moving a Formatted Text Item Select the formatted text item by clicking on it while in Development mode. A selected item will be displayed with a red dotted line border and 'resize' boxes, as shown for a table item below. It may be necessary to resize the item when it is first pasted in. To resize, click the left mouse button on one of the eight resize boxes and drag it to a new location. To move the formatted text item to a different location in the window, click anywhere in the region between the red dotted line and the border of the text item and drag the text item to a new location. Editing a Formatted Text Item The Diagram window must be in Development mode in order to edit the Formatted text item. Select the item by clicking on it. Click again at the point that you wish to edit. Text can then be edited in the usual manner. Formatted options are available by clicking the right mouse button which will display the following popup menu. Inserting EES Variable Information into a Formatted Text Item The calculated value of one or more EES variables, optionally including its units and the EES variable name, can be inserted into a formatted text item while in Development mode. The contents of the text item are automatically updated as the EES variables are changed. This capability is similar to that available for Output variables in the Diagram Window. It differs in that it allows the calculated variable to be placed in a formatted paragraph or table, simplifying the construction of the Diagram window and facilitating report generation. 53 Chapter 2 EES Windows To insert a variable, place the cursor at the insertion point and click the right mouse button to bring up the menu shown above. Select the Insert Variable command which will display the following dialog. Select the EES variable you wish to insert from the list on the left. Typing the first letter of a variable will scroll the list to a variable beginning with that letter. Check the Hide array variables control to eliminate array variables from list. Indicate whether you wish to include the variable name and units with the EES variable by clicking the appropriate radio button. In Development mode, EES will display the inserted variable with a #, followed by 1, 2, or 3 (depending which of the three radio button options was selected) and then the EES variable name. For example, if variable XYZ is inserted with its value and units, it will appear as #2XYZ in the formatted text item. When the Diagram window is in Application mode, the insertion indicator will be replaced with the current EES variable information. Deleting a Formatted Text Item To delete a formatted text item, place the Diagram window in Development mode and select the item by clicking on it. Then press the right mouse button. A pop up menu will appear with Properties as one of the menu item choices. Select the Properties command. A dialog will appear with a Delete button. Clicking the Delete button will remove the formatted text item. The Diagram window input is ignored if the Diagram window is hidden. The Diagram window can be used with the Parametric table (i.e., the Solve Table command) if the ‘Use Input from Diagram’ check box is checked in the Solve Table dialog window. Using Drop-Down Lists to Set One or More EES Variables When a string variable is selected for input in the Diagram Window, the option of including the units is replaced with an option for providing a list of alternative choices for the string variable in a drop-down list. An Edit button will appear which will allow the existing choices to be viewed and/or changed. The string choices are displayed in a drop-down list box which displays the available choices when the user clicks in the box. 54 EES Windows Chapter 2 It is possible to use the strings in the drop-down list to set the values of one or more EES variables. This is accomplished by following the string that is to be displayed with characters // and then with one or more EES equations on one line. The EES equation can also be a$INCLUDE directive which add one or more lines of text to the Equations window. For example, suppose you wish to use a drop-down list to have a user select the density and thermal conductivity of one of several substances. You could create a dropdown list with the following strings. Note that the strings could also be read from a file in the Professional version or set within Check Box or Radio Group controls. When an item from the drop-down list is selected or when calculations are initiated, EES will execute the equations to the right of the // characters and update the Diagram Window display. If the Format Display control in the Modify Diagram Text dialog is checked, the drop-down list will only show the characters to the left of // like this. An interesting extension of this concept is provided in the last string of this list which is 'User Input // density=?; conductivity=?'. In this case, EES interprets the '=?' to mean that that the value of the variable should be entered in an edit box. In order for this to work, the variables density and conductivity must be displayed on the Diagram window as Output variables. When the 'User Input' item is selected, EES will look for these Output variables and change them to Input variables. The general capability afforded by the '=?' notation is that selected variables can be changed from Output to Input or from Input to Output variables on the Diagram Window by a user selection from a drop-down list. An example of this capability is provided in the Diagram_In_Out.ees example file. Adding Graphic Items Lines, rectangles or circles (ellipses) can be drawn on the Diagram window or child diagram windows using the line, rectangle, and circles tools on the toolbar. Holding the Shift key down while drawing a line will cause the line to be drawn horizontal, vertical, or to the closest 45° angle. Holding the Shift key down while drawing rectangles and circles will 55 Chapter 2 EES Windows cause them to be draw with its width equal to its height. The graphic items can be resized or moved in development mode as described in the next section. Clicking on the line button in the Diagram window tool bar allows a single line to be drawn. If you want do draw several lines in succession without having to click the line button for each one, hold the right mouse down while clicking the left mouse button on the line button. When you are done drawing lines, click the left mouse button on the toolbar line button or press the Esc key. In the Professional version, the graphic item can be given a name. The name can then be used to assign attributes to the graphic item with EES variables in the Equation window or Parametric table. For example, the left and top of the item named Bottle could be specified with EES variables Bottle.left and Bottle.top, respectively. Objects return to the location specified in the dialog when the Diagram window is in development mode. In a similar manner, the width, height, angle, fill color and line color of the graphic item can be specified with EES variables, allowing programmatic control over the attributes of a graphic item. Logical uses for this capability are to move a figure (animation) or to show one of several figures while hiding the others based on the selection from a drop-down list. Selecting, Modifying and Aligning Text and Graphic Items One or more text and graphic items in the Diagram window or child diagram windows can be selected by clicking the left mouse button on the item while in development mode. A red dotted box will be displayed around each selected text item. Hold the Shift key down to select more than one item. A selected graphic object will be displayed with its 'handles' (small boxes on each edge) showing. All selected items can be moved at once using the mouse or the arrow keys. The align button in the tool bar can be used to facilitate alignment of the selected items relative to one another. If all of the selected items are text items, pressing the right mouse button will bring up a dialog box in which the font, size, color, and style of the selected text items can be changed as a group. When it first appears, the dialog box displays the characteristics of the first selected text item. Any change made to a text characteristic in the dialog window will be applied to all selected text items. If a text characteristic, such as the font size, is not changed in the dialog window, then the font size of the selected text items will not be changed. Similar capability is provided if all selected items are graphic objects. Clicking anywhere in the Diagram window that is not on a text or graphic object unselects all selected items. Group and Ungroup Buttons Two or more graphic and/or text items can be grouped in development mode. However, only simple text items can be included in a group. Text items which provide input or output on the Diagram window can not be grouped. Grouped items act just like a single item. A 56 EES Windows Chapter 2 group can be resized, moved, copied and pasted. A group can be included in another group to form nested groups. To create a group, select the items that are to be in group and then click the Group button the toolbar. Alternatively, right click on one of the selected items and select the Group menu command from the pop-up menu that appears. Group information is saved with other file information when the Save command is issued. To ungroup a previously defined group, click on the grouped item and then click the Ungroup button on the toolbar. Alternatively, right click on the grouped item and select the Ungroup menu command from the pop-up menu. Adding a Calculate Button One or more Calculate buttons can be placed on the Diagram or (child Diagram) window by selecting the Add Calculate button in the Diagram window tool bar. By default, the Calculate button caption is "Calculate" and pressing the button provides exactly the same function as selecting Solve from the Calculate menu or pressing F2. The calculate button caption and the action taken when the Calculate button is clicked can be changed by rightclicking the button and providing the desired text while in development mode. The position and size of the button can also be specified in this manner. In the Professional version, the Calculate button can be given a name. The name can be used to dynamically control the left,, top and hide attributes of the Calculate button. Adding a Plot Window Access Button A 'live' plot and/or a link button to a particular Plot Window can be placed on the Diagram window or child Diagram window by selecting the Display Plot Window button in the toolbar. The dialog window shown on the left will appear after clicking this toolbar button. The plot that is to be displayed (or linked to) is selected from the drop down list at the top of the dialog. The names appearing in this list are the names on the tabs of the Plot window. The 57 Chapter 2 EES Windows dialog window provides two radio buttons. If the first radio button is selected (as shown on in the Dialog window on the right), the selected plot will be displayed in the Diagram or child Diagram window. The location and size of the plot can be specified using the edit controls at the bottom of the dialog. In addition, the plot can be dragged to a desired location and resized in the same manner as any other graphic items while in the Development mode. If the Maintain aspect ratio check box is selected, the height to width ratio of the plot will be maintained when the plot is resized. If the Add button to link to Plot window radio button is selected (as shown in the left dialog), a button will be placed on the Diagram window. Clicking this button in Application mode will open and display the selected plot window. If the plot window does not exist, this button will do nothing. The location and size of the plot window access button can be specified in the plot window button dialog. Alternatively, the plot window access button can be dragged to any location when then toolbar is visible. Finer positioning is available by pressing the left, right, up, or down arrow keys which move the button one pixel for each press. The width and height of the button can be changed by holding the Ctrl key down while pressing arrow keys. The right arrow increases the button width by one pixel. Left arrow decreases the width. Down and up arrows affect the height. Right-clicking on the plot or the plot window access button when the toolbar is visible (i.e., in Development mode) will bring up the dialog so that the characteristics of the plot access button (name, glyph, or position) or the plot position and size can be changed. The Professional version allows a picture that is stored in a bitmap (.bmp) or JPEG (.jpg) file to be displayed on the button. The picture option is selected with the drop-down control below the caption. A standard file selection dialog box to facilitate selection of the picture file will appear when the picture option is chosen. Creating Hot Areas and Child Diagram Windows (Professional Version only) A 'Hot Area' is a rectangular region on the main Diagram window that will open a child Diagram window when the cursor is positioned in the region and the left mouse button is clicked. The child Diagram window includes all of the features of the main Diagram window, including the ability to have hot areas with its own child windows. To create a hot area, move the cursor to the upper left of the region and drag it to the lower right while holding both the Ctrl and Shift keys down. When the mouse button is let up, a window will appear in which you provide a name for the child Diagram window. The child Diagram window will appear whenever you click the mouse in the designated area. You can copy a figure into this window and add text and graphic objects using the commands in the tool bar in the same manner as in the main Diagram window. Note that the tool bar must be visible (i.e., development mode) to move or modify any text or graphic objects. The characteristics of the child Diagram window can be changed by clicking the right mouse button in the region while holding the Ctrl and Shift keys down. A dialog window will 58 EES Windows Chapter 2 appear in which the name and the region bounds, and other information can be viewed or changed. The hot area can also be deleted with this dialog. Hold the Ctrl and Shift keys down to see an outline of all currently defined hot areas. Saving User Inputs A Save User Inputs button can be placed on the Diagram window (but not on a child Diagram window) by selecting the Show/Hide Save Inputs button in the Diagram window tool bar. The Save button is needed only for Distributable6 programs, since regular EES programs can always save all program information with the normal Save command. When the user presses the mouse on the Save button, a file containing the current values of the all EES variables, including the current values of inputs, is written to the disk. The file that is written has the same parent name as the EES file that is executing and a .VAR filename extension. The file is written to the directory that the Distributable program is located in. EES will look for this .VAR file when the Distributable program is started or when one of the five files contained in the Distributable program is selected from the recent file list at the bottom of File menu. If the .VAR file is found, it will be automatically loaded and the input information on the Diagram windows will be updated. The Save button is disabled until calculations have been successfully completed. In this way, it is not possible to write a set of input information that will not successfully calculate. By default, the Save button caption is "Save". The caption can be changed by right-clicking on the button and providing the desired text while in development mode. Use the arrow keys to reposition the button and the Ctrl arrow keys to resize the button. Creating Links (Professional Version) Link buttons can be placed on the Diagram window or child Diagram window by selecting the Create Link button in the tool bar. A dialog window will appear after clicking this toolbar button in which the caption and link properties can be specified and assigned to a button that will appear on the foremost Diagram window. An option is provided for a transparent button which can be placed anywhere in the Diagram or child Diagram windows. The caption and properties can be changed at a later time by right-clicking on the link button while the Diagram window is in development mode. Six different types of links can be created: Link type 1: Start an External Program This link type allows any program, including another instance of EES, to be started when the user clicks the link button in the Diagram window while in application-mode. The link 6 See the Make Distributable Program command in the File Menu section of Chapter 3 for information on Distributable programs. 59 Chapter 2 EES Windows button property can be the full filename and optionally, the name of the file that is to be opened when the application starts. Alternatively, just the name of the file that is to be opened is needed if the application information is provided in the operating system registry, as usually the case. As an example, the following link property will start a second copy of EES and load file TEST.EES. C:\EES32\TEST.EES EES can communicate with other programs using Lookup files (Chapter 4). The $SAVELOOKUP and$OPENLOOKUP directives make this process more convenient. In addition, EES will check the date/time stamp of any lookup file it uses and if the file is changed, it will be automatically reloaded. Link type 2: Open EES File This link type will close the existing EES file and open the EES file specified as the link button property. EES will check to see that the current EES file is saved, and if not, ask for confirmation before closing the existing file. This option is useful when the results of one EES program provides data for use in the next EES program. For example, information can be calculated and saved in a Lookup Table that is automatically loaded in the next EES program with the $OPENLOOKUP directive. Link type 3: Open Distributable File This link type is applicable only to distributable programs created with the Make Distributable Program command. Distributable programs can include up to 5 EES files. As with option 2, this link type allows one EES file to open another, but in the case of a distributable program the EES file must be one of the five included with the distributable program. It is referred to by its number, 1 to 5. Link type 4: Open Child Diagram Window This link type is applicable if one or more child Diagram Windows have been created. A list box showing the names of all child Diagram windows is provided. Clicking the button will open the specified child Diagram Window, just as if the user had clicked the mouse within the hot area for the child Diagram window. However, the button can be positioned anywhere in the Diagram window, so it no necessary to click on the hot area for the child Diagram window. Link type 5: Play Macro adapted with EES variables This link type will play a predefined Macro file that has been stored with a .EMF filename extension. The first parameter that must be supplied in the edit box is the macro filename, including the .EMF filename extension. All other parameters are optional. It is possible to provide information to the macro file that allows its capability to be programmed. This is 60 EES Windows Chapter 2 done by providing parameters after the macro file name separated with a space or comma. These parameters can be EES variable names, numerical values, or strings. EES will process the Macro file looking for the character sequence %%N where N is an integer value. If this sequence is found, %%N is replaced with the Nth parameter. For example, suppose the macrofile name doPropPlot.EMF has a line that contains: PropPlot %%1 PH 2 %%2 %%3 0 DoQLines If the Play Macro link information is doPropPlot.EMF R$, Thigh, 0 EES will replace %%1 with the value of the EES string variable R$, %%2 with the value of EES variable Thigh, and %%3 with 0. The property plot will then be drawn. Note that calculations must be completed to enable the button. Link type 6: Open a Lookfile File A Link button can be placed on the Diagram window that, when clicked, will display the familiar Open File dialog. A user can then select a Lookup file having a filename extension of .LKT, .TXT, or .CSV and that Lookup file will be opened. After the selection has been made, an EES string variable having the same name as the caption of the Link button is created and its value is set to the name of the Lookup table that has been read in. EES does not allow spaces in a variable name so any spaces in the caption are set to underscores. Also, the maximum length of the variable is 29. The last character of the EES variable name is set to$ to indicate that it is a string variable. As an example, if the caption of the Link button is "Open Lookup File”, clicking the button will read the file, create variable Open_Lookup_Fileand set the value of this variable to the name of the Lookup table that was created. If the Lookup table already exists, it will not be re-read. Clicking OK in the Link Properties dialog will create the link button. The button can be dragged to any location while the Diagram Window is in development mode or moved with the arrow keys. Right-clicking on the link button while in development mode will bring up the Link Properties dialog so that link properties can be changed or the button can be deleted. In this dialog, the Link button can be given a name. The name is used to dynamically control the button attributes. For example, if the button name is Link1, EES will create variables Link1.Hide, Link1.left, and Link1.top. These variables can be set in the EES program or in other parts of the Diagram window, such as in the code that accompanies Check Boxes, Radio Groups, or Drop-down lists. The button size can be set in the Link button dialog. Alternatively, the Ctrl-arrow keys allow adjustment of the height and width of the button. 61 Chapter 2 EES Windows Adding a Help Button One or more Help buttons can be placed on the Diagram window or child Diagram window when the window is in development mode. In this case, the toolbar will be visible. Click on the Add Help button icon on the tool bar which is identified with a yellow circle containing a question mark symbol. The Help button will appear along with a small dialog in which you may enter the caption for the Help button and the name of the help file that will be displayed when the user selects the Help button in Application mode. This file can either be an ASCII text file (*.TXT), a Windows help file (*.HLP) or an HTML file (*.HTM). EES will automatically determine the file type independent of the filename extension. In the Professional version, the Help button can be given a name. The name is used to dynamically control the button attributes. For example, if the button name is Help1, EES will create variables Help1.Hide, Help1.left, and Help1.top. These variables can be set in the EES program or in other parts of the Diagram window, such as in the code that accompanies Check Boxes, Radio Groups, or Drop-down lists. The help button can be removed by by right-clicking on the button in Development model and then clicking the Delete button. Navigating through Child Diagram Window (Professional Version) The main Diagram window can have 'hot areas' which bring up child Diagram windows when clicked. The child Diagram window can also have 'hot areas' forming grandchildren and so on. Each child Diagram window will have a small 'home' button which, by default, is initially located in the lower right corner of the window. Clicking this button will close the window and bring up the main Diagram window. If the parent of the Diagram window is not the main Diagram window, a second button with a left arrow will also be displayed at the lower right. Clicking this button will close the child Diagram window and bring its parent. The location and size of these navigation buttons can be changed using the arrow and Ctrl-arrow keys, respectively. A caption can be added to either button by right-clicking on the button in development mode. Adding a Print Button One or more Print buttons can be placed on the Diagram window or child Diagram window when the window is in development mode. In this case, the toolbar will be visible. Click on the ‘Add Print button’ icon on the tool bar which is identified with a printer icon. The Print button can be dragged to any location in the window while the toolbar is visible. The location of the button can also be changed with the arrow keys. The caption and button location and size can be changed by right-clicking on the button to bring up the Print Button dialog. In the Professional version, the Print button can be given a name and variables name.left, name.top, and name.hide are then created. These variables can be set in the Equations window or in other Diagram window controls. The Print button can be 62 EES Windows Chapter 2 configured in two ways. It will either print the Diagram window (with no confirmation) or it will bring up the Print dialog as if the Print command in the File menu were selected. Adding an Audio-Visual Item Audio-visual items such as movie files (having an .avi file name extension) or sounds (having a .wav filename extension) can be placed on the Diagram window or child Diagram windows by selecting the Add Audio-Visual item button in the toolbar. The following dialog window will appear after clicking this toolbar button. The Browse button facilitates selection of the audio-visual file. Any file that following the MDI interface should be acceptable, including files that have a .avi or .wav file name extension. If a movie file is selected, EES will automatically fill in the Width and Height of the movie. These fields can be changed. If the Lock aspect ratio button is selected, changing either width or height will result in an automatic change in the height or width to ensure that the original aspect ratio remains unchanged. will be placed If the Show control buttons is checked, a control bar below the audio-visual item. The bar has the familiar play, pause, stop, step, previous control buttons. If the control buttons are not selected for display, then the movie is controlled by the left and right mouse buttons. To play, click the left mouse button within the item rectangle while in Application mode. To pause a playing item, click the left mouse button within the item rectangle. Clicking the right-mouse button stops a playing move and resets it to the beginning. The audio-visual control information can be viewed or changed by right-clicking in the item rectangle while in Development mode. 63 Chapter 2 Saving and Loading User Inputs (Professional Version) EES Windows Save and Load Inputs buttons can be placed on the Diagram window (but not on a child Diagram window) by selecting the “Add Save Inputs” or “Add Load Inputs” button in the Diagram window tool bar. Save and Load buttons are needed only for Distributable programs, since regular EES programs always save all program information with the normal Save command. This capability is available only in the Professional version. When the user clicks the Save button, a standard file save dialog will appear in which the name of a file can be entered. The default name is the same name as the EES file with a filename extension of .VAR. The filename and directory information can be changed but the filename extension must be .VAR in order for EES to recognize the file. If confirmed, a file containing the current values of the all EES variables, including the current values of inputs, is written to the disk. This .VAR file can later be loaded with the Load button. A standard file open dialog will appear in which a .VAR file can be selected. The Diagram windows will be updated with the values of the variables found in this file. When opening one of the five EES files contained in the Distributable program, EES will look for a .VAR file in the same directory the Distributable program having the same parent name as the EES file. If a .VAR file is found with this parent name, automatically loaded and the input information on the Diagram windows will be updated. The Save button is disabled until calculations have been successfully completed. In this way, it is not possible to write a set of input information that will not successfully calculate. Both the Save and Load buttons will be disabled if the Diagram window does not contain input variables. By default, the Save button caption is "Save" and the Load button caption "Load". The captions can be changed by right-clicking on the button and providing the desired text while in development mode. A dialog will appear in which the caption, size, location and name of the button can be specified. If the button is given a name, the button attributes can be controlled by assigning name.hide, name.left and/or name.top with EES variables in the Equations window or in Check Box, Radio Button or drop-down Diagram window controls. Creating and Using Check Boxes (Professional Version) A check box can be placed on the Diagram window using the Add Check Box button on the Diagram window toolbar (Professional Version). A check box allows the equation set that EES solves to be modified by the check box setting. After selecting the Add Check Box button on the toolbar, the setup checkbox dialog will appear that allows the caption text, location on the Diagram window, and font to be specified. The location can be later changed by dragging the check box to the desired location while the Diagram window is in development mode. 64 EES Windows Chapter 2 The checkbox can be given a name. If a name is provided, the attributes shown with underlined text can be set with EES variables. For example, the left position of the check box in the example below could be specified by setting the value of PressureLoss.left. In the following example, several input and output text items have been defined and been given names. These text items are either hidden or shown depending on the check box setting. The check box dialog provides two windows in which EES commands (comment, equations and directives) can be entered, just as if they were entered in the Equations window. If the check box is unchecked, the commands in the first window are included with other commands in the Equations window when calculations are initiated. If the check box is checked, the commands in the second window are included. If "Execute EES commands when check status is changed" is selected, EES will attempt to execute the commands in the unchecked or checked window, depending on the setting of the check box, directly after the change is made to the check box. This capability is most useful when the check box setting affects the display in the Diagram window in some way. In the example below, some text inputs and outputs are immediately hidden if the check box to calculate pressure losses is not selected. Graphical objects and buttons can be hidden or positioned in this manner as well. 65 Chapter 2 Creating and Using Radio Groups (Professional Version) EES Windows A radio button group is placed on the Diagram window using the ‘Add Radio Group’ button on the Diagram Window Toolbar (Professional version). A radio button group provides up to 8 radio buttons. Each button is associated with a set of EES commands that are enabled when the corresponding radio button is selected. The following dialog window will appear after licking the toolbar button. The number of radio buttons is set with the spin control, or by entering the value. The number of buttons can be between 2 and 8. The number of columns controls how the buttons are positioned. The number of columns can be between 1 and 4. An optional group caption can be entered for the radio button group. The background color, width, height, location, and font characteristics can also be specified. Changing any of these controls will cause the group box in the dialog window to be redrawn as it will appear in the Diagram window. Each button is associated with EES commands. The caption and EES commands for the currently selected button appear at the bottom of the dialog. Both the caption and the EES commands for this button can be modified. 66 EES Windows Chapter 2 The radio group can be given a name. If a name is provided, the characteristics identified with underlined text, e.g., left, top, color, and hide, can be set with EES variables. In the example above in which the name is RG, setting EES variable RG.Color would change the background color of the radio button group. If "Execute EES commands when check status is changed" is selected, EES will attempt to execute the commands associated with the selected button directly after it is selected. This capability is most useful when the check box setting affects the display in the Diagram window in some way. The frivolous example above sets the background color of the radio group to different colors depending on the selected button. A more useful application of the radio button capability would be to control the position and visibility of objects, text, and buttons on the Diagram window. For example, a Calculate button can be hidden by setting the EES variable, Name.Hide=true# where Name is the name give to the Calculate button in the Calculate Button Characteristics dialog. After clicking the OK button the radio button group will appear in the Diagram window. In Development mode, the radio button group can be dragged to a new postion by pressing and holding the mouse on the group border will moving the group to a new location. If the mouse is pressed on the lower right corner of the radio button group the cursor will change to a resize arrow cursor. Dragging the mouse at this point will allow the width and height to be changed. Right-clicking (or double-clicking the left mouse button) in Development mode brings up the Radio Button Characteristics dialog so changes can be made. Animation (Professional Version) The Professional version of EES provides powerful capabilities to animate drawing and plots in the Diagram and Plot windows. Unlike many other animation programs that provide capability to create animated drawings, EES allows the animation to be controlled by calculated values. The animation in the Diagram window can thus be accurately displayed and directly coupled to information in the plots. Animations can only be created by the Professional version, but once created, they can be displayed in any version of EES, including distributable programs. Creating an animation with EES is very simple. The first step is to draw the object in a the Diagram (or child diagram Window). Alternatively, the object can be created in an external program such as Power Point and pasted into the Diagram window. The object must be given a name in the name field of the object properties dialog. Then equations are added into the Equations window to specify the position, size, or color of the object or text. The position and size are specified in pixels with 0,0 being the upper left corner of the window. EES provides functions DiagramHeight#, DiagramWidth#, and PixelsperInch# to allow the 67 Chapter 2 EES Windows position and size to be computed in other units and converted to the pixels needed in the Diagram window. The final step is to add an Animation control bar to the Diagram window. This is done by selecting the Add Calculate button in the Diagram Window Toolbar when the Diagram window is in Development mode. The following dialog will appear. Click the Animation Control Bar button to place an animation control bar on the Diagram window. The functions of the controls on the animation bar are indicated above. The bar can be dragged to a desired location by pressing and holding the mouse button down anywhere on the first four buttons and sliding the mouse to a new location. As a simple example, we will animate the position of a ball in the Diagram window. Bring the Diagram window to the front and set it into Development mode. Click the circle tool on the toolbar and create a red ball. Enter the name of the object to be Ball, as shown. 68 EES Windows Chapter 2 In the Equations window, enter the following equations. ball.left=X ball.top=150 + 100*sin(X) Create a Parametric table with columns X, ball.left, and ball.top and 360 rows. Enter values for X between 0 and 360. Click the Add Calculate button and select the Animation bar. Right-click on the start button in the animation bar to bring up the animation characteristics dialog. Select the Solve Table button. Hide the Diagram toolbar so that the Diagram window is now in application mode. Click the start button and watch the show. Text and lines can also be animated in this way. 69 Chapter 2 EES Windows The animation can be coupled to a plot. Crate a new plot with the x-variable set to Ball.left and the y-variable set to Ball.top. Right click on the plot and select the Automatic Update checkbox. Start the animation and watch the plot. Its EESy to create animations. Animations generated in the Diagram window (Professional version) can be saved in a sequence of .EMF files that can be assembled into a stand-alone movie with Microsoft Movie Maker or other software. This capability is enabled by clicking the Save Movie button on the animation control bar. 70 EES Windows Chapter 2 Plot Windows Variables which appear in the Parametric, Lookup, Array or Integral tables may be plotted with the New Plot Window or Overlay Plot commands in the Plot menu. The New Plot Window command allows 2-D and 3-D plots to be created. In addition, 2-D plots of the thermodynamic properties can be generated using the Property Plot command. All plots appear in the Plot Window, which is equipped with tabs at the top of the window to allow easy identification and access to each plot. There is no limit on the number of tabbed plot windows that can be constructed (other than available memory), and each 2-D plot may have any number of overlaid plot lines. A hint appears when the mouse is moved over that tab on a plot or table window. The hint normally contains the descriptive text that can be added when you right-click on the tab. If no descriptive text has been added, the hint for the plot window is the names of the variables that are plotted on the X and Y axes. The hints make it easier to find the plot or table when many have been created. There are many plotting options such as choice of line type and plot symbol, linear/logarithmic scaling, spline fitting, tick frequency, and grid line control. These options can be set when the plot is first drawn or at a later time using the Plot window controls described below or the Modify Plot and Modify Axes commands in the Plot menu. A tool bar, shown below, is provided on 2-D plots with buttons to add text, lines, boxes, and ellipses. An alignment button on the tool bar allows selected items to be aligned in a specified manner. The visibility of the tool bar is controlled by the Show/Hide Tool Bar menu item in the Plot menu. Right-clicking the mouse within the plot window (but not on any plot item) will also toggle the visibility of the tool bar. Add text item Add rectangle Align selected items Move plot Add line or arrow Add circle or oval Show crosshairs and values Zoom a section of the plot The appearance of a 2-D plot can be changed in many ways using the plot menu commands in the Plot menu and controls in the Plot window. Moving the Plot The entire plot, including the axis scales and all text items, can be moved to a different location in the Plot window by by clicking the move plot button in the plot window toolbar or by holding the Ctrl key down. Either action is then followed by pressing the mouse button within the plot rectangle and dragging the mouse to move the plot to the desired location in the window. 71 Chapter 2 EES Windows Adding / Changing Text and Text Characteristics A text item can be added to the plot window by clicking on the text button in the plot window toolbar. When clicked, the Format Text dialog shown below will appear. Three basic types of text items can be created: plain text, EES variables, and integral. The choice is made by checking the corresponding radio button at the top of the dialog. Plain text is used to identify fixed information displayed in the plot or to produce a legend. The EES variable option provides the same capability with the difference being that the text can include the name, value and units of a pre-defined EES variable and this information can optionally updated dynamically. If the Integral button is selected, EES will create a text item holding the integral of a selected line on the plot. If Auto Update is selected for the plot and the values being plotted change, the integral will also change accordingly. The text is entered or edited in the text edit field and it is displayed as it will appear on the plot at the top of the dialog. Controls are provided to change the font, size, color and style of the text item as well as the text itself. For example, to set some or all of the text to have a bold style, select the text and the click the B button. The I and U buttons set italic and underline styles. The button places a linebreak. Subscripts and superscripts can be generated using the appropriate buttons after selecting the text that is to be subscripted or superscripted. Three additional speed buttons are provided below the subscript button to facilitate entry of lower or upper case Greek letters and useful symbols. The symbol entry buttons operate as follows. Press and hold the mouse button down on one of the three symbol buttons. A palette of symbols will be displayed to the right of the button. While holding the mouse button depressed, slide the mouse cursor to the symbol palette and position it over the symbol you wish to select. When the mouse button is released, that symbol will be added to the text item at the current insertion point. EES allows any horizontal text item to be associated with a plot symbol to facilitate construction of a legend. Clicking in the Legend symbol box will produce a drop-down list containing a descriptor of each existing plot. If a plot is selected, the line type and symbol used for that plot will be displayed just to the left of the text item and it will move when the text item is moved. 72 EES Windows Chapter 2 When you click on a text item in a plot window when the tool bar is visible, a red dotted box will be drawn around it to indicate that this item is selected. You can select multiple text items by holding the Shift key down as you click on the text items. Alternative, a rectangular area within the plot window can be selected when the tool bar is visible by pressing the mouse at the upper left corner and dragging it to the lower right corner. All text and graphic objects within this rectangle will be selected when the mouse button is released. Double-clicking the left mouse button (or clicking the right mouse button) on a text item will bring up a dialog window in which the characteristics of all selected items can be changed. If only one text item is selected, the Format Text Item dialog window shown above will appear displaying the text and its current characteristics. When more then one text item is selected, the Format Text Item dialog window displays the characteristics of the first selected text item. Any change made to a text characteristic in the dialog window will be applied to all selected text items. If a text characteristic, such as the font size, is not changed in the dialog window, then the font size of the selected text items will not be changed. In this way, you can change just the font without affecting other characteristics such as the size or color. The selected items can be copied or cut using the Copy or Cut commands. The Paste command can then be applied to move them from the clipboard to this plot or to any other EES plot window. The Delete key provides the same function as the Cut command. If you accidentally delete text or lines, use the Paste command to restore them. 73 Chapter 2 EES Windows Selected text items can be copied to the Clipboard using the Cut and Copy commands in the Edit menu. The Delete key will cut all selected text items. Once on the Clipboard, the Paste command can be applied to move the text item from the Clipboard to any EES plot window. The Professional version of EES will also show the following information in the Format Text Item dialog. These controls can be used to position a text item relative to data point in a selected plot. If the data change and Automatic Update is selected for the plot, the text item will move with the data. This option is particularly convenient when plotting arrays. Selecting Show Array Indices in the New Plot Setup or Overlay Plot dialogs will automatically generate a text item for each plotted array point containing the number of the data point for identification. Note that the text item is initially placed just to the upper right of the data point. However, the text item can be moved to a different location by clicking on it to select it and then dragging it with the mouse or using the arrow keys. Alternatively, the X and Y offset values (in pixels) can be set. (These offset values are referenced to the default value that EES uses when it first places the test to the upper right of the data point.) If the text item is linked to a data point, its poistion relative to the data point will be maintained, even if the data point is subsequently moved. Moving Text Text fields to label the X and Y axes are automatically generated when a plot is constructed. Additional text items can be added to the plot using the Add Text command in the Plot menu. You can move any text item or set of selected text items to any position on the screen by pressing and holding the left mouse button down while the cursor is on the text item and dragging it to its new location. (Use the Shift key to select more than one text item.) Selected text items can also be moved using the arrow keys. Clicking the left mouse button on a text item will select it. Selected text items are displayed within a red dotted rectangle. Each arrow key press moves all selected text one pixel in the arrow direction. Adding Graphics and Text from the Clipboard Graphic and text items that have been copied to the Clipboard from other applications in the Windows metafile format can be pasted into the Plot Window using the Paste command in the Edit menu when the plot window tool bar is visible. After an item has been pasted, it can be moved and sized, just like any of the other items in the Plot window. With this capability, it is possible to, for example, place equations from Mathtype in the Plot Window 74 EES Windows Chapter 2 or place a small version of another plot within a Plot. The easiest way to place a plot within a plot is to copy the Plot Window to the Clipboard and then Paste it into PowerPoint or Word. Rescale it and then paste it back into the EES Plot window. Two or more instances of EES may be open at the same time. In this case, graphic and text items be copied from one instance and pasted into another. Adding Lines and Arrows, Rectangles and Circles The Add Line toolbar button in the plot window toolbar allows lines or arrows to be placed anywhere within the Plot window. After clicking on the line button in the toolbar, the cursor will appear as a cross. Press and hold the mouse button down at the position where you wish the line to begin. Hold the mouse button down while moving the mouse to the desired end position of the line. If you hold the Shift key down, the line will be forced to drawn at an angle of 0°, 30°, 45°, 60° or 90°. Release the mouse button to complete the line construction. Initially, a line will be created of the type that was last chosen. If you wish to change the type, for example to add or change an arrowhead, double-click or right-click on the line. A dialog window will appear in which the arrowhead type, line thickness, and color may be selected. By default, the line can be resized, moved, or rotated. If you wish to prevent these capabilities, deselect the Moveable check box. The current line and following lines created with the Add Line toolbar button will then have the same characteristics as the previous line. Rectangles and circles can be drawn in a similar fashion using the rectangle and circle buttons on the Plot window toolbar. 75 Chapter 2 EES Windows Moving Lines and Arrows, Rectangles and Circles Clicking on a line when the plot window tool bar is visible will cause it to be displayed with small boxes at both ends. Multiple lines can be selected by holding the Shift key down or by using the mouse to draw a selection rectangle around the objects. Double-clicking the left mouse button (or clicking the right mouse button) will cause the Modify Line dialog window to appear in which the characteristics (such as arrow style, arrow size, line thickness, and color) of all selected lines can be changed at one time. Selected lines can be copied to the Clipboard using the Cut and Copy commands in the Edit menu. The Delete key will cut all selected lines. Once on the Clipboard, the Paste command can be applied to move the line from the Clipboard to any EES window of the same type. Rectangles and Circles can be moved and copied in the same manner. You can move, resize, or rotate the line after it is created. To move the line, press and hold the mouse button down anywhere near the middle of the line while dragging it to its new position. You can also use the arrow keys to move one or more selected lines. When you select a line by clicking on it, small boxes will be displayed at either end of the line. To rotate the line and/or change its length, press and hold the mouse button within either of the two small boxes. Move the end to its new position and release the mouse button. Holding the Shift key down while rotating the line will force it to be horizontal, vertical, or on a 45° angle. Holding the Shift key down while resizing a rectangle or circle will force the width and height to be the same size. The position and length of the line can also be controlled by entering values for the Start and End position in the plot line dialog. Zooming In on an Area in the Plot A rectangular area within the plot window can be selected by pressing the mouse at the upper left corner and dragging it to the lower right corner. If the Shift key is held down during this process, the selected rectangle will have the same aspect ratio as the plot rectangle. If the plot window toolbar is visible, all text and graphic objects within this rectangle will be selected when the mouse button is released. If the plot window toolbar is not visible or if the Zoom Selection button on the plot tool bar has been pressed, the plot information within selected rectangle will be drawn with the enlarged scale in a new plot window. The axes and any other information in this zoomed plot can be adjusted in the same manner as for any other plot window. Resizing the Plot The size or aspect ratio of the plot can be changed by pressing and holding the left mouse button with the cursor located within the resize area at the lower right corner of the plot rectangle. If the tool bar is visible, the resize area is marked with three 45° lines. The when it passes over the resize cursor will change from an arrow to the resize indicator control. The size of the plot will change as you drag the lower right corner to a new 76 EES Windows Chapter 2 position. When the plot is resized, the size and positions of all text items and lines are proportionally changed. (You can prevent the text font size from changing if you hold the Ctrl key down while resizing the plot.) Modifying the Axis Information The axis scaling and appearance can be changed by double-clicking the left mouse button on the abscissa or (left or right) ordinate scales or by selecting the Modify Axes menu item in the Plot menu. Either action will bring up the Modify Axes dialog window. The axis for which the changes are to be made is indicated by the radio-button controls at the upper left. By default automatic axis scaling if off and the scaling of the selected axis is controlled by the minimum, maximum and interval values shown in the edit boxes. These values can be changed as desired. However, if the 'Automatic scaling' checkbox is checked then the axes will be automatically scaled as appropriate to contain plotted data for all lines in this plot window. In this case, the edit boxes for the minimum, maximum and interval values will be disabled. If a new plot line is added or if the data in one or more of the plots are changed such that one or more points are outside the range of the axis scale, the axis scale will automatically change. Scale numbers are placed at the position of each interval, as are Grid lines if selected. Selecting the Zero line causes a vertical (for x-axis) or horizontal (y-axis) line to be drawn at a value of zero. The #Ticks/Division is the number of minor ticks, i.e., the number of tick marks between each interval. Enter 4 ticks/division to break the major division into 5 pieces. If Grid lines is selected, clicking on #Ticks/Division will change it to #Grids/Division allowing grid lines to be placed at points in between the major ticks. If the Show Scale control is selected (as shown), the scale numbers will be displayed. The characteristics of these numbers are controlled by the remaining fields on the right-side of the dialog window. The X and Y-axis scaling can also be changed without using the Modify Axis dialog. As the mouse cursor passes over an axis of the plot, its appearance will change to a left-right or up77 Chapter 2 EES Windows down arrow. Holding the left mouse button down at this point will allow the axis to be dragged to a new location. Duplicating or Deleting a Plot Window An entire plot window can be duplicated or deleted by right-clicking on its tab at the top of the plot window. A small dialog will appear having a Duplicate and a Delete button. The duplicate plot provides a convenient means of creating a plot template so that all of your plots have the same appearance. The Delete cannot be undone so be careful. Saving the Plot All plots are automatically saved with the EES file. However, in some circumstances, you may wish to save a file just containing the plot. Right-clicking the plot tab at the top of the plot window will bring up the dialog window below. Clicking the Save button in will allow you to save the specified plot as a TIFF (.TIF) file, bitmap (.BMP), JPEG (.JPG), Windows Metafile (.WMF), or Windows Enhanced Metafile (.EMF). Modifying the Plot Information The line type, color, plot symbol (or bar type for bar plots), and other information relating to each plot can be viewed or modified by double-clicking the left mouse button anywhere within the plot rectangle (but not on text or a line.) The dialog window shown below will appear. This dialog window can also be made to appear with the Modify Plot menu item in the Plot menu. All current plots in the current plot window will be listed in the rectangle at the upper left in the order in which they were constructed. Select the plot by clicking on its name. 78 EES Windows Chapter 2 EES allows plots to be created that use the right-hand y-axis (Y2) and a top x-axis (X2) scale. The scales in use for the selected plot are shown at the lower left of the dialog in radio button controls that allow changes to be made. The Spline fit control, if selected, will cause EES to plot the line using cubic splines to produce a smooth curve through the data. Automatic Update sets up a direct link between the plot and the data in the Parametric Table so that the plot will be automatically redrawn if any change is made to the data in the Parametric Table. Clicking the Data button to the right of Automatic Update allows the characteristics of the link (e.g., row range, X and Y axis variables) to be changed. The error bars control allows error bars to be placed in the horizontal, vertical or both directions. Error bar information can come from one of two sources. If calculations are initiated with the Uncertainty Propagation command, the error bar information is assumed to be the calculated or specified uncertainty values for the variables plotted on the X and Y axes. If the Uncertainty Propagation Table command is not used, clicking the X-Axis or Y_axis check box in the Error bars box will bring up the Specify Error Bars dialog in which the data needed to draw symmetric or unsymmetrical error bars is entered. Click the Apply button if you wish to view the changes you have made. When there is more than one plot line within a plot window, the plots are drawn in the order displayed in the plot line list in the Modify Plot dialog. The order can be changed by selecting a plot line and dragging it to the desired location with the right mouse button. When the order is changed, reordered will be displayed below the left corner of the plot line list. The reordering is not actually done until the Apply or OK buttons are clicked. 79 Chapter 2 EES Windows Aligning Items on the Plot Window The Align button on the Plot Window toolbar is enabled when two or more text items, lines, rectangles, or ellipses are selected. These objects are created with the Add Text, Add Line, Add Rectangle, and Add Ellipse toolbar buttons. After selecting this button, a small dialog window will appear showing alignment choices. Click OK to proceed with the alignment of the selected items. Crosshairs Clicking the crosshairs button on the plot window toolbar or holding the Shift and Ctrl keys down will change the cursor into crosshairs. The coordinates at the intersection of the crosshairs can be viewed in the status bar at the bottom of the plot window. If the plot was generated using the Properly Plot command in the Plot menu, the values of all thermodynamic properties corresponding to the state fixed by the crosshairs will be displayed in the plot window title bar. Displaying Plot Windows Pressing the left and right arrow keys in the Plot Window displays the previous or next plot, respectively, provided a text or graphic item is not selected. If an item is selected, the arrow keys move the item by one pixel. 80 EES Windows Chapter 2 3-D Plot Controls The three-dimensional plotting package is based on a modification of the public domain GLScene package (http://www.glscene.org/). An example 3-D plot window is shown below. The image is generated with the New Plot|X-Y-Z plot menu command. The image in the plot window can be rotated around any axis by clicking the mouse on the image and dragging it to a new location. The image can be colored or gray scale. In either case, the color can be used to represent the values of any variable. If no specification is made, the colors are chosen relative to the z-axis variable. General Controls The 3-D plot control panel, shown at the bottom of the 3-D plot window, can be made visible or hidden by double-clicking or right-clicking the mouse in the plot window. The Show/Hide Toolbar command in the Plot menu also provides this function. The Axes checkbox has 3 positions. Clicking in the box rotates through the positions. If the box is checked, X, Y, and Z axis lines are drawn through the plot origin with red, green, and 81 Chapter 2 EES Windows blue dotted lines, respectively. If the box is checked with a white background, axis labels will be displayed to help identify the rotational position. If the box is unchecked, the axis lines are not drawn. If the Perspective checkbox is checked, a perspective projection of the 3-D surface is displayed. If the box is not checked, orthogonal projection is employed. Perspective projection appears more correct to the eye but orthogonal projection is easier interpret. The Color checkbox has three positions. If the box is unchecked, the surface is displayed with with shades of gray. The color can be controlled with the slider to the right of the color checkbox. If the box is checked once, the value of Z (or the value of an optional color variable) is represented on the surface in color ranging from blue to red. If the box is checked a second time, the colors are changed to be full-spectrum as shown in the figure above. The optional color variable is chosen in the X-Y-Z Plot Setup. If a variable is not chosen, the color variable is Z itself. A legend indicating the values associated with the colors if the Legend box is clicked. The Resolution slider controls the size of the polygons used to form the surface plot. High resolution (slider bar to the right) results in a crisp plot, but rendering and rotating may be sluggish. You may want to experiment with this control to determine a suitable compromise between display speed and quality. Scale Slider controls are provided to separately scale the X, Y and Z axes. Moving the slider to the right increases the scale factor for the selected axis. The slider can be moved with the mouse or with the left/right arrow keys. The check boxes for X and Y control the visibility of surface grid lines. The vertical slider scales the X, Y, and Z directions uniformly. Moving the slider down increases the apparent size of the plot. This slider can also be controlled with the up/down arrow keys. The lower and upper limits of the plotting range can be changed for the X and Y axes by right-clicking on the slider control. Grid Position The option of displaying grids in each of the orthogonal planes is controlled with the checkboxes. For example, the grid in the YZ plane will be visible if the checkbox preceding X is checked. The grid can be moved to any position within the range of values chosen in the X-Y-Z Plot Setup using the mouse or the left/right arrow keys. The current location of the grid is shown in the box to the right of the slider. A value can be directly entered into this box which will cause the grid to move to the specified value. 82 EES Windows Chapter 2 Orientation Buttons Clicking the Top button will rotate the display so that the view is of the X-Y plane looking down the positive Z-axis towards the origin. The Front button presents a Y-Z plane viewed along the positive X axis. The Side button displays the X-Z plane from the positive Y axis. Tool Bar The tool bar provide buttons to place text, lines, boxes, and circles on the plot in the same manner as for 2-D plot windows. An align button is also provided. The help button displays this page. Position Indication Holding the Shift and Ctrl keys down will cause the 3-D coordinates to be displayed in the window caption, provided that the X and Y-axis grids are visible. The information displayed is the current locations of the X and Y grids, followed by the value of Z on the surface for the given X and Y. If the color corresponds to a variable other than Z, its value on the surface at the specified X and Y is also shown. If the X and Y grids are moved using the mouse while the Shift and Ctrl keys are held down, the information in the window caption will be automatically updated. Saving and Loading Plot Templates The Professional version allows plot templates to be saved and applied. A plot template contains information that affects the visible display of a plot. The characteristics of an existing plot can be set as desired and then these characteristics can be be saved in a .EPT (EES plot template) file. The characteristics can be transferred to other plots by selecting the .EPT file and applying it. The Save Plot and Apply Plot Template buttons are accessed by right-clicking the mouse on the tab at the top of the plot window. That will bring up the following dialog. Click the Save Template or Apply Template button to initiate the operation. 83 Chapter 2 EES Windows The .EPT file is a text file that can be viewed and edited by the user. The Save Template saves the characteristics for the current file, but these characteristics can be edited with any standard text editor. Each item in the file is annotated with a comment. Setting a value in the .EPT file to -99 disables the change in that characteristic. Open an .EPT file for further explanation. The tabs used to select different plot windows can be 'dragged' to a different tab location. This method of reordering the tabs is quicker than the alternative of right-clicking on each tab and specifying the tab position in the above dialog. 84 EES Windows Chapter 2 Report Window (Professional Version) The Report Window operates just like a typical word processor offering the usual choice of fonts, font sizes, text style, color, highlighting, tabs, left and right indents, etc. Graphics can be pasted into the window at the cursor position. The graphics can be equations copied from the Formatted Equations window, a plot from the Plot window, or any graphics in the Diagram window. Graphics can also be pasted from other applications. In addition, the Report Window can include EES variables that are automatically updated as their values change. A sample Report Window is shown below. 85 Chapter 2 EES Windows To include the name, value, and/or units of an EES variable, click on the EES button in the tool bar or, alternatively, click the right mouse button and select Insert Variable from the popup menu. Either action will bring up a dialog showing all current EES variables. Select the variable you wish to insert from the list on the list and then indicate with the check boxes the information about this variable that is to be inserted in the Report Window. Click OK. The information inserted in this manner is automatically updated in the Report Window when changes value of the variable is changed. and Export Note that the Report Window provides buttons on the tool bar to Import text. The Import button will insert the contents of a selected .RTF or .TXT file at the cursor position. The Export file will export the entire file to a specified .RTF or .TXT file. The .RTF files can include graphics. For example, you can include a graphical letter head in an .RTF file and import it whenever you wish to prepare a formatted report. The report can be printed, by clicking the print button. button on the toolbar shows or hides the coding that EES uses to identify variables. The In some cases, the hidden text will interfere with the ability to add text. If this problem occurs, click this button and you should then be able to enter text anywhere. Exposing the coding also helps to identify where in the text the EES variables have been placed. Click the text again to hide the coding. 86 EES Windows Chapter 2 Debug Window The Debug Window displays diagnostic information of three types: Incorrect Degrees of Freedom, Constrained Solution, and Unit Checking Report. Each of these capabilities is described below. Incorrect Degrees of Freedom Whenever an attempt is made to solve a set of equations in which the number of equations is not equal to the number of variables, a message box such as that shown below will appear. Clicking the Yes button will bring up the Debug window. For example, This window provides two lists of variables. The first list shows all variables which are referenced only once in the Equations Window. These variables are possibly spelled wrong or otherwise not being directly used in the problem, except for informational purposes. The second list shows the variables which are most likely to be involved in any missing or extra equations. The information used to construct this second list is determined by examination of the blocking order of the equations in the Residuals window. You may also find the information in the Residuals window helpful in identifying the problem with your equation set. 87 Chapter 2 EES Windows Clicking the left mouse button on a variable name in the Debug window will bring the Equations Window to the front with that variable name selected. Constrained Solution In some cases, a problem cannot be solved to within the specified tolerances because the lower and/or upper bounds one or more variables have restricted the solution. If this happens, EES will present a dialog box warning of this problem and offer more information. If the user wishes to see the additional information, the Debug window will appear similar to that shown below showing the variables that are constrained and the affected equations. Clicking the left mouse button on a variable name will open the Variable Info dialog window in which the lower or upper bound can be changed. Clicking on an equation will move the cursor to that equation in the Equations window. 88 EES Windows Chapter 2 Unit Checking Report The Check Units command in the Calculate menu will display its finding in the Debug window. Each equation that is found to have a dimensional or unit inconsistency will be displayed (in black) followed by an explanation (in blue). Clicking the left or right mouse button will bring up a popup menu. The pop-up menu offers the options of jumping the focus to offending equation in the Equations window or bringing up an abbreviated form of the Variable Information dialog window showing only the variables in that equation. In addition, the unit checking for the selected equation can be disabled from this menu. The units that are associated with each variable can be entered in a number of ways. A direct way of entering units is to type them directly into the Variable Info dialog (Options menu). It may be somewhat more convenient to enter the units of each variable in the Solution window. Clicking the mouse button on an variable will toggle its selection state. Right-clicking will open a dialog in which the units of all selected variables can be set. Units of constants can be declared directly in the Equations Window by following the numerical value with the units provided in brackets. For example, the following equation will set the Q_dot to 1000 with units of Btu/hr. Q_dot = 1000 [Btu/hr] The units of variables in the Parametric and Arrays tables can be changed by right-clicking on the column header. The Default Variable Info command (Options menu) allows the units (and other information) to be set based on the first letter of the variable name. The Professional version allows .var files to be saved from the Variable Info dialog which save the units and all other information. Opening a .var file using the Read .Var File button in the Variable Info dialog or using aInclude directive sets the variable information for all variables that have been previously saved. The units that EES recognizes can be displayed using the Unit Conversion Info command (Options menu). Note that the Check Units command uses the dimensional information contained in the Units.txt file which exists in the directory that the EES program is located. You can add new units or modify information in this file using any text editor. 89 Chapter 2 EES Windows Calculator Window The Calculator window allows single-line expressions to be evaluated. For example, if you enter: ?sqrt(5) and then press the Enter key, EES will evaluate the expression and place the result on the following line, as shown. The expression you enter can involve EES variables that have been previously defined (and evaluated) in the Equations window. Any of the built-in functions can be used, as well. Note that the value returned in the Calculator window is the current value of the variable. If you have not initiated the Solve or SolveTable commands, the value may not be current. New variables may be defined in the Calculator window, provided that they are not already defined in the Equations window. For example, in the above example, variable x is set to the enthalpy of R134a. If any of the thermodynamic property functions are used, the unit system in effect is that which is defined with the Unit System command. Be sure to press the Enter key after entering each line in order to process the command. The contents of the Calculator window are deleted when the window is closed. If you need to save the information in this window, select it and copy it to another window or another application. The Calculator window recognizes the following commands. % {insert the last calculated value in place of the % character} Clear {clear the contents of the Calculator window} Solve {initiates the same action as the Solve command in the Calculate menu} Exit {close the Calculator window} 90 CHAPTER 3 __________________________________________________________________________ __________________________________________________________________________ Menu Commands The File Menu Open will allow you to access and continue working on any file previously saved with the Save or Save As… commands. After the confirmation for unsaved work, the dialog window shown above will appear. The current directory is indicated below the text Folders: and EES files in that folder (directory) are shown in the list on the left. To select a file, click on the file name in the 91 Chapter 3 Menu Commands list or enter the filename in the File Name: edit box. You can open files in another directory by entering the directory name in File Name: field or by clicking on the folders listed in the Folders list. Clicking on the Drives list displays the available drive designations. Click on the drive name to select it. Choose the OK button to select the file (or directory) displayed in the Filename field. EES can read five types of files that are identified as EES file, Import file, Text file, Library file and Compressed EES file formats. The format is selected with the dropdown list at the bottom left of the dialog window. EES files with a .EES filename extension are the norm. Import files with a .XPT extension are files saved by EES with the Export option from a different operating system, such as the Macintosh. Text files with a .TXT filename extension contain ASCII text which is read into the Equations window. Library files are EES files containing one or more functions, procedures or modules which can be automatically loaded at startup, as described in Chapter 5. Compressed EES files have a .EEZ filename extension. These files can only be written in the Professional version, but they can be read by any version. The compressed files use the zip compression techniques and they can be much smaller than the corresponding .EES file when the EES file contains a lot of data or employs graphics in the Diagram window. New initiates a new work session. All variables and equations will be cleared. The unit system will be restored to the settings that would be in effect if the program were restarted. If an unsaved problem definition exists, you will be asked if you first wish to save your current problem information. Merge allows the equations previously saved in an .EES file to be merged with the current contents of the Equations window at the cursor position. The Merge dialog window operates in the same manner as for the Open command. Equations can also be entered from a text file using the $INCLUDE directive. EES functions, procedures and modules can be loaded using the Load Library command or$INCLUDE directive. Save will save your problem definition with the same file name (which appears after Save in the File menu and in the title bar of the Equations window) as it was last saved. For a new work session which has not yet been named, you will be prompted to supply a file name, just as if the Save As… command were given. All information concerning the problem definition is saved, including the equations, variable information, the tables, the plots, and the size and locations of the windows. By default, the file will be saved in the standard EES file format with a .EES filename extension. If you wish to export the file to a version of EES on a different operating system, use the Export format in the file type available in the Save As… command. A check mark will appear to the left of the word Save in the File menu if the current problem information has been saved on disk. Any change in the problem information will cause the check mark to disappear. Note that 92 Menu Commands Chapter 3 EES will check your equations before saving the file and any error in the file will be flagged before the save operation is initiated. Save As… provides the same function as the Save command except that it will first prompt you to supply a filename in the Save File dialog window. The Save As command allows the problem definition to be saved with another filename or in a form which can be exported to EES versions on other operating systems. Enter the file name of your choice in its place. The 32-bit version of EES supports long file names. The file name may include drive and directory information. However, it is not necessary to enter a filename extension, since EES will supply the extension automatically. EES recognizes five file types. If EES is displayed in the Type box at the lower left, the extension in the File Name: field will be set to .EES (the norm) and files having this extension will be displayed in the filenames list. The Export file type will apply a .XPT filename extension and save the file in a generic ASCII format which can be transferred to other operating systems such as the Macintosh. The Text file type will apply a .TXT filename extension and save only the text in the Equations window in an ASCII file. The Library type will change the filename extension to be .LIB. Each time EES is started, it opens all of the .LIB files located within in the USERLIB\ sub-directory and automatically loads the functions, procedures, and modules in these files. These functions can be used exactly like the EES built-in functions. Library files are one of the most powerful features of EES because the user can easily develop special purpose functions. See Chapter 5 for additional information. The Compressed EES file with .EEZ filename extension contains exactly the same information as an .EES file, but it is compressed and therefore is often a much smaller file than the .EES file. 93 Chapter 3 Menu Commands EES normally saves every variable defined during the work session regardless of whether or not it currently is in use when the Save or Save As command is issued. For example, if you define a variable X with the equation X=6 and later decide that the equation should read X1=6, EES will still keep the variable X and all of its characteristics in memory, e.g., guess value, bounds, units, and format. The Commercial version EES can store up to 6,000 variables. The Professional provides storage for 12,000 variables. For very large problems, particularly problems using array variables, EES could run out of space. In cases when there are many variables that are not in use, EES will display a check box in the Save As dialog with the caption "Purge XXX unused variables" as shown above. To save only those variables which are currently in use, click this checkbox. When purging variables, it is advisable to save the file with a new name. In this case, the original file can be recovered if a problem develops. Print will print any or all of the EES windows to the printer or to a file on the disk. Each window has a small check box preceding its name. If the check box is grayed (as it is for the Arrays window in the Print dialog window shown below) the window is not available for printing. If an X appears in the box, the window will be printed. To place an X in the box or to remove an existing X, click the mouse while the cursor is positioned in the box. Some windows, such as the Plot Window and the Parametric and Lookup Table windows, may contain many sub-windows, accessible by tabs at the top of the window. For these windows, clicking in a check box will bring up a small supplementary window to select the plots or tables that are to be printed. 94 Menu Commands Chapter 3 The printed output will be sent to the selected printer. The drop-down box at the top of the dialog allows the printer selection to be changed. It is possible to direct the output to a file, rather than a printer, with the Connect options in the Printers applications. See the Windows manual for additional information on selecting printers. Printing options such as the font, line spacing, and font size are set in the Preferences dialog window (Options menu). If the “Print in color” check box is selected, EES will attempt to print selected windows using the same colors as appear on the screen. Colored text may not print clearly on some black and white printers. When this control is deselected, all printing will occur in black and white. If the “Page breaks” check box is selected, a forced page break will occur so that the printed output for each window starts on a new page. The Preview button will direct a facsimile of the printed output to the screen. Printer Setup provides a dialog window that allows the printer to be selected along with printing options, such as the paper size and orientation. The printer selection can also be made in the Print dialog window. Load Library will bring up the standard open file dialog showing EES Library files (which have a .LIB file name extension) in the file selection box. Library files contain usersupplied functions, procedures, and/or modules which operate as described in Chapter 5. Once loaded, these library files remain in memory until EES is closed. Note that when EES starts, it will preload all of the library and externally-compiled files which are found in the USERLIB\ sub-directory so the Load Library command is not needed for these files. The Load Library can also be used to load external functions and procedures with filename extensions of .DLF, .DLP, and .FDL. See Chapter 6 for additional information. The $INCLUDE directive described in Chapter 7 can also be used to load library files. Load Textbook reads a user-generated Textbook index file with the filename extension (.TXB) and uses the information in this file to create a Textbook menu at the far right of the menu bar. A textbook index file can also be loaded automatically by placing the textbook index file and associated problem files in a subdirectory within the USERLIB subdirectory The Textbook menu provides convenient access to set of problems, such as 95 Chapter 3 Menu Commands those developed for use with a text. The Textbook menu section at the end of this chapter provides instructions for creating and using a Textbook menu. Make Distributable Program will create a special purpose version of EES which will run up to 100 pre-selected problems. The following dialog will appear when this menu command is chosen. A special version of the EES program with the selected EES problems and all supporting files are placed in an executable file when you select the OK button. If the Create Zip file option is selected, the executable file and any library files that you select to include with it are compressed into a single .zip file. The executable file can be freely distributed to others. An expiration date can be optionally set which will prevent the program from being used thereafter. The executable file can be password protected. This Make Distributable Program command is available only in the Professional version. When the distributable program is started, the first file will automatically be loaded by default. However, any one of the files can be selected as the file that appears at startup by providing /# as a parameter where # is an integer between 1 and 100. For example, entering MyPrg.exe /2 in the Windows Run dialog will start the distributable program and display EES file 2. A menu with the file names is provided at the rightmost position of the menu bar. The name of the menu is entered at the bottom of the dialog. Any of the other files can be selected from this menu. 96 Menu Commands Chapter 3 Two small buttons are provided just below the Cancel button in the Make Distributable dialog. These buttons allow saving and loading of scripting files to simplify the process of creating distributable programs. The button on the right saves all of the information in the Make Distributable dialog window into a file having a .MDI (Make Distributable Information) filename extension. The other button will open *.MDI files and fill all of the field in the Make Distributable dialog window using the information in the file. Clicking on the File Information tab displays the following dialog with specific information for each EES file that is to be included in the distributable program. An optional help file can be provided for each EES file. The help is accessed from the Help menu. The name of the file as it appears in the menu can also be specified. The remaining items in for each EES file are a series of check boxes that control the capabilities the user will have when running the distributable version. If you want you user to have the ability to view the equations window, click the 'Equations Window Visible' check box. You can make this window read-only by clicking the following check box. However, even if the user changes the equations, the changes cannot be saved with the distributable version. The advantage of this feature is that you can freely distribute any program you generate in EES to others. 97 Chapter 3 Menu Commands Open or Create Macro (Professional version only) will initiate the process of recording a series of EES instructions that can later be started from the Windows Run command or from a different program to replay all of the instructions in the Macro file. Used in this manner, EES can be directed to solve a set of equations in a specified text or EES file and put the solution into another specified text file without ever appearing on the screen. EES can also run the Macro file on demand by a Dynamic Data Exchange (DDE) command. Additional information concerning Macro files is provided in Chapter 7. Create Latex/PDF Report generates a report including the Diagram, equations, solution, tables, and plots. In this respect, this command is similar to the Print command. However, the Create LaTeX/PDF Report command does not directly print but instead creates a TeX document in LaTeX2e. The TeX document is an ASCII file with a .tex filename extension that must be processed by a LaTeX2e compiler. LaTeX2e produces a .dvi (device independent) output file that can be viewed and printed by various utilities. However, the PDFLaTeX accessory that is included with the TeX compiler can also produce a .pdf (portable document interface) file that can be viewed and printed with Adobe Acrobat Reader. To make use of the output generated by this command you will need to install the LaTeX2e compiler and Adobe Acrobat Reader, if they are not already installed on your computer. Both of these programs are available at no cost. The recommended installation of Latex2E is MiKTeX. The MiKTeX homepage is http://miktext.org. The following installation directions are applicable to MiKTeX version 2.1. Download the distribution zip file in one step by either clicking on the appropriate link in the MiKTeX home page or entering the following URL into your browser program: http://www.miktex.org/2.1/index.html. Instructions for downloading the MikTeX files are provided on this webpage. The downloading is facilitated by the MikTeX Setup Wizard. Clicking on this option causes a small file to be downloaded which supervises the remaining download process. Run the Setup.exe wizard program and select the download radio button. Some of the downloading sites are slow so you may want to try a few. Select the small option. After the files have been downloaded, run the setup.exe program again and select the Install radio button. This installation program will install MiKTeX into the directory that you specify. EES must know the directory path of the PDFLaTeX.exe program that is provided with MiKTeX so make a note of the directory that you are installing the MiKTex package into. To configure EES to work with the MikTeX package, start EES and select the Create LaTeX/PDF Report command from the File menu. Click the Setup button in the PDF LaTeX box and enter the directory information for the PDFLaTeX.exe program. Adobe Acrobat Reader can be downloaded from: http://www.adobe.com/products/acrobat/readstep.html. 98 Menu Commands Chapter 3 Select the language and operating system from the dialogs provided on this webpage and download file ar405eng.exe to a temporary directory. Execute this file to install Adobe Acrobat Reader. Adobe Acrobat can also be installed from the EES CD when you install EES. A dialog shown above will appear after selecting the Create LaTeX/PDF Report command. At the top of the dialog is an edit field for a filename. By default, this filename is set to the name of the EES file but with a .tex filename extension. The filename can be changed, but is should have a .tex filename extension if it is to be recognized by the pdflatex application. The Browse button to the right of the filename should make it easy to select an alternative location for the file. The Title field is by default filled with the EES filename and the date. This title, which can be changed to whatever you wish, will be displayed centered at the top of report. On the left side of the 99 Chapter 3 Menu Commands dialog are controls to select the windows that will be included in the report. Each window is represented with a group box with one or more options. If the group box is displayed in grayed text, the corresponding window is not available. The title of each group box begins with a left bracket character. If the window is to be included in the report, the character following the left bracket must be an X or a number. Click on the group name to change the selection. The Parametric Table, Lookup Table, Integral Table and Plot windows, have tabs with the possibility of accessing more than one window. If there are multiple windows, a dialog will appear when you click on the group name to allow selection of the tables or plots that are to be included in the report. In this case, the number enclosed in the brackets in the group name is the number of tables or plots that are to be included. If there is only one possibility, such as for the Equations, Solution, and Arrays windows, an X, rather than a number will be enclosed within the brackets if the window is to be included. One limitation of the LaTeX report is that it will not automatically fit the contents to the width of the paper. For example, long equations may end up running off the right margin. Each group box provides controls to deal with this situation. Long equations are the major problem. You can control this situation somewhat by modifying the equations you enter in the Equations window. For example, a long equation can be broken into two or more shorter equations by introducing some new variables. Also, EES allows you to break an equation so that it continues on the following line if the last character on the line is a &. (Note: the total length of an EES equation must be less than 255 characters, even if it is broken into multiple lines with the & character.) The LaTeX report will also attempt to break the equation at the & symbol, but depending on the formatting, it may produce a LaTeX error. If you are familiar with LaTeX code, you can of course modify the .TeX file as needed. The check boxes in the Equations group box allow multiple equations that are entered on a single line in EES to appear on separate lines in the report and comments that appear on the same line as the equation to be be placed on a separate line. Both of these options help to reduce the long line problem. Other tools available to deal with long lines are the font size and margins that are specified on the right side of the dialog. The Solution and table group boxes each have a field to specify the number of columns that will be used to display the data in the report. The .TeX processor does not wrap the information if it is too wide for the page, but you can control this problem quite well by specifying the number of columns. The width of the Diagram and plot windows can be directly entered. The figures will be scaled to the width you specify while maintaining the existing aspect ration. The Diagram and Plots that are to be included in the LaTeX document are stored in separate files having a .jpg filename extension in the same directory as the .tex file. These .jpg files have same parent name as the .tex file with the addition of _D for the 100 Menu Commands Chapter 3 diagram and _P1, _P2, etc. for the plots. When creating a .jpg file, a decision must be made to balance the file size with file quality. The user has control over this decision with the JPG quality input box. The allowable values are 1 to 99. Low values result in small .jpg file sizes (which result in small .pdf file sizes) but sacrifice graphic quality. Large values result in high quality graphics, but at an expense of great file sizes. The default value, 75, seems to provide a reasonable balance. The PDFLaTeX group box on the right side of the dialog contains three checkboxes. If the Create PDF document checkbox is selected, EES will attempt to start the PDFLatex.exe application to compile that .tex file that it has just saved. If the Display PDF document checkbox is selected, EES will attempt to start Abode Acrobat to display the .pdf file. If the Delete TEX document checkbox is selected, the LaTeX file will be deleted leaving only the .PDF file. EES must know where the PDFLaTeX.exe application resides. The default location is C:\textmf\miktex\bin\pdflatex.exe. You can specify or change the default location by clicking on the Setup button. When you click the Create button, EES will write the information in the dialog to a small file called EES_TeX.ini so that it is available as the default the next time you enter this dialog. The file is written in the Default File Folder specified in the Preferences dialog. If no folder is specified, the file will be placed in the same directory as the EES application. Also, note that EES will save your file when starting the Create LaTeX/PDF report command with a filename created by appending a ~ to the current name. Should any problems occur that cause EES to stop, your file can be recovered. Exit provides a graceful way to exit the program. The remaining items in the File menu are recently accessed filenames. Selecting any of these filenames opens the file. This list can be disabled in the Preferences dialog. It is recommended that this list be disabled if the program is installed and used on a network. 101 Chapter 3 Menu Commands The Edit Menu Undo restores the Equations window to the condition it was in before the last editing operation. The Equations window supports 8 levels of Undo. If Undo is unavailable, the menu will be disabled. Cut deletes the selected (highlighted) text or selected item. The deleted item is placed on the Clipboard where it can be pasted to another location with the Paste command. Copy functions in a manner dependent on which window is foremost. Copy will place the selected text from the Equations window on the Clipboard from which it can be restored at the cursor position with the Paste command. When the Parametric, Lookup, or Array Table window is foremost, the Copy command will copy the selected cells (shown in inverse video.) The data copied from the table are stored on the Clipboard in a standard format in which numbers within the same row are separated by a tab and each row ends with a carriage return - line feed. Data in this standard format can be pasted into any location of the Parametric or Lookup tables or into other applications. (Hold the Shift key down when selecting the Copy command if you wish to also copy the column heading and units.) Copy will move a selected Plot window or the Diagram window graphics into the Clipboard from which it can be pasted into other applications. EES copies the Plot window to the clipboard in two formats: as a picture and as a high-resolution bitmap. Most programs, such as a word processor, provide a Paste Special command in which you can select among the available formats that have been placed on the clipboard. The bitmap requires more memory, but it produces a high quality image when printed. The Picture format produces exactly the image that you see on the screen. If you are intending to print the image that you have copied and you are concerned with the print quality, use the Paste Special command and select the bitmap option. If you hold the Ctrl key depressed while copying the Diagram window, the text items added with the Add Diagram Text command will not be included. The copy of the Plot 102 Menu Commands Chapter 3 or Diagram window is stored in MetaFilePict object format. Copy Solution will place the contents of the Solution window on the Clipboard both as ASCII text with each variable is on a separate line and as a picture of the formatted Solution window. Use the Paste Special in another application, such as a word processor, to select either the text or the picture for pasting. See the description of the Solution Window for more information. Copy will place the entire contents of the Residuals window on the Clipboard as text. Tabs separate the different items on each line of the Residuals windows. The Clipboard contents can be pasted into a word-processor. Copy Table with Headers is only enabled when the Parametric, Lookup, Arrays, or Integral table window is the foremost window. In this case, both the Copy Table and Copy Table with Headers commands will be visible. The Copy Table command will copy to the Clipboard the selected cells in the table as tab-delimited text. This text can be directly pasted in a spreadsheet application. The Copy Table with Headers command will copy the Header and Units of each column in addition to the selected data. Use the Select All command to select all of the cells in the table before issuing the Copy Table or Copy Table with Headers command. Copy Diagram is only enabled when the Diagram window is the foremost window. The contents of Diagram window are placed on the clipboard as a bitmap and as an extended metafile. Save Diagram is only visible when the Diagram window is the foremost window and the Diagram window tool bar is hidden. The Diagram can be saved as a .jpg or .bmp file. Paste is active for the Equations, Parametric, Lookup, Plot and Diagram windows. Paste moves the text (or graphics for the Diagram window) previously placed on the Clipboard with the Cut or Copy commands in EES or in other applications. When Paste is used in the Parametric or Lookup Table window, the values stored on the clipboard will be copied to the table starting in the cell in which the cursor is currently located. Data can thus be moved between the Parametric and Lookup tables. Copy and Paste can also be used with text items placed on the Plot windows. Clear removes the selected text without placing a copy on the Clipboard. Clear can also be used to delete the contents of the Diagram window. Select All will select all of the text in the Equations window, or all of the cells in any of the three tables, depending on which window is foremost when the command is issued. The Select All command is normally followed by Copy which places the selected items on the clipboard. If the Formatted Equations window or Solution window is foremost, the 103 Chapter 3 Menu Commands Select All command appears as Select Display. This command will select all currently visible items in the window. Insert/Modify Array provides an easy way to enter or modify the values in EES Arrays. The dialog window is shown below. The dropdown edit rectangle at the top of the dialog displays the names of all of the arrays that are defined in the Equations window. Select the name of the array for which you wish to enter or modify values. If no arrays are defined, this rectangle will display -> Enter array name. Enter the name of the new array. The number of columns and rows in the array can be adjusted with the Rows and Columns controls. Scroll bars will appear as needed to allow access to array cells that are not visible in the window. The two speed buttons provide access to Copy and Paste. The top button is the Copy button. It is enabled only if two or more cells in the table are selected. To select a range of cells, click the mouse in the upper left cell. Hold the Shift key down and click in the lower right cell. The Copy button should then be enabled. The Paste button is enabled only if text has been placed on the clipboard. To paste text into this window, click the mouse in the upper left cell for which the paste operation is to start. Pasting will proceed to the right and down the table. The copy and paste capability make it possible to import or export data to and from a spreadsheet. 104 Menu Commands Chapter 3 Enter the values of the array elements that you wish to define in the table. When you click the OK button, EES will convert the values that you have entered into EES equations and enter these into the Equations window. The entered will be placed within comments of the form: {Array A} A[1]=1 A[2]=2 … {Array A end} where A is the array name. Do not delete or edit these comments. EES uses these comments to locate the position in the equations window in which the array elements are defined. If you later wish to redefine the array, EES will find the previous array using these comments and overwrite the array with the newly entered values. 105 Chapter 3 Menu Commands The Search Menu Find will search the Equations window for the first occurrence of the text entered in the Find what: field. The search is case-insensitive unless the ‘Match case’ option is selected. If the ‘Match whole word only’ option is selected, the text will be found only if it is delimited by spaces or mathematical operators. The Cancel button will change to Done after the find process is completed. Replace will search the Equations window for the first occurrence of the text in the Find what: field and replace it with the text in the Replace with: field. The search options are as described for the Find command. The Replace All button will replace every occurrence of the search text with the replacement text. The Cancel button will change to Done after the find process is completed. Next will find the next occurrence of the text previously entered with the Find or Replace command. The search options will be remain in effect if they were set in the Find command. 106 Menu Commands Chapter 3 The Options Menu Variable Info will provide a dialog window, as shown below, in which the guess value, lower and upper bounds, display format, and units of all variables currently appearing in the Equations window can be viewed and changed. These data are initially set to default values. The defaults, selected based on the first letter of the variable name, may be set with the Default Info command. If the program contains one or more subroutine, i.e., Functions, Procedures, Modules or Subprograms) (see Chapter 5 for a discussion of subroutines), a control will be provided at the top of the dialog to select the subroutine or main program. The information for the selected routine can then be changed or viewed. The “Show Array Elements” checkbox control will be visible at the upper left of the dialog window if there are any arrays are used in the Equations window. When this control is selected, all array elements appear in the Variable Info dialog and the guess value, bounds, display format, and units can be set for each individual element as for any other variable. However, when the control is not selected, all arrays elements are represented by a single entry. For example, X[ ] represents all array elements having the 107 Chapter 3 Menu Commands parent name X. If any of the characteristics for a parent array are changed, that change is applied to ALL array elements. Changing the guess value for X[ ] will result in the new guess value being applied to all array elements in array X. However, other characteristics, such as the bounds and units, would not be affected. In addition, the array name can be changed by editing the name in the first column of the Variable Info dialog. Use the scroll bar on the right side of the dialog window to bring the variable information into view. Note that the height and width of this dialog window can be changed by selecting an edge and dragging it in the usual Windows manner. All fields, including the variable name, may be changed as required. If the variable name is changed, EES will change every occurrence of the original variable name in the Equations, Parametric table and Diagram windows. The control above the second column allows either the guess values or current values of the variables to be displayed the second column. The words, -infinity and infinity can be used to indicate unlimited lower and upper bounds, respectively. The Guess, Lower and Upper value fields will also accept a variable name, as well as a number. When a variable name is provided, EES uses the current value of that variable as the guess value or bound. Before this dialog window appears, EES will attempt to solve equations that have a single unknown. If the value of a variable has been pre-calculated, its pre-calculated value will be displayed instead of the its guess value in the guess value column and the value will be shown in bold font. These bold values can be changed and doing so will change the guess values. In some cases, that will affect the calculated result for these variables. The display format of a variable in the Solutions or Table window is controlled by the three fields in the Display columns. Clicking in these fields will produce a pop-up menu for the display style, number of significant digits, and highlighting effects. The units of the variable may be entered in the units column. Units are displayed with the variable value and also used for unit checking. A comment can be embedded within a unit string by surrounding the comment with either braces ({}} or backslash (\) characters. The comment will be displayed with the unit but it will be ignored by the Convert function when doing unit conversions. The length of the unit string, including the comment, is limited to 30 characters.. The Convert function described in Chapter 4 can be used to convert units. Note that the display format and units of each variable can also be changed by clicking on the variable in the Solution Window. When the OK button is pressed, all changes made to the variable information since the dialog window appeared are accepted. The Update button replaces the guess value of each variable with its current value, i.e., the value determined in the last calculation. The same update feature is provided with the Update Guesses command in the Calculate 108 Menu Commands Chapter 3 menu. The Print button will direct a copy of the information in this table to the selected printer. The Cancel button will restore all fields to the condition they were in when the Variable Information dialog was first presented and then remove the dialog. The Variable Info dialog window can be resized by dragging the lower right corner. As shown in the figure above, there are two display modes. In Selection Mode, the active cell is outlined and there is a small box at the lower right of the cell. The contents of the cell can be copied to other cells above or below it by pressing the mouse button while the cursor is positioned within the small box and dragging the cursor to the desired location. (The cursor will change to an up/down arrow when it is positioned over the small box.) While in Selection mode, Ctrl-C will copy the contents of the active cell to the clipboard and Ctrl-V will paste the contents of the clipboard to the active cell. Selection and Edit modes are applicable to the Guess, Lower, Upper, and Units columns. Clicking the mouse within the selected cell causes a change to Edit mode. In Edit mode, the outline and small box will not be displayed. Instead the contents of the cell will initially be highlighted. The usual editing procedures can be applied to modify the contents of the cell. Pressing F2 causes the display to toggle between Edit Mode and Selection Mode. Alternatively, clicking on any other cell or in the header or footer of the dialog will change the display to Selection Mode. Professional Version Variable information for a module or main EES program can be saved to or loaded from a disk file. The file operations are accomplished using the two small buttons at the upper right of the Variable Information dialog. Variable information is saved in a file having a .VAR filename extension. However, the information in this file is in tab-delimited ASCII format so that it can be opened, viewed or modified with a word processor or spreadsheet. Variable information data can be saved to an existing .VAR file. In this case, the file is updated with the current information for the variables that are in use. Information in the file concerning variables that are not currently in use is not modified or deleted. For example, suppose you have a program that uses variables X, Y, and Z. You save the variable information to an existing file that already has variable information for variables A, B, C, and X. The information for variables A, B, and C is not altered. The variable 109 Chapter 3 Menu Commands information for X is updated to the current settings and variable information for Y and Z are appended to the file. If a program contains one or more modules, a dropdown list appears at the top center of the Variable Info dialog from which the module or main program can be selected. In this case, the Save or Open Variable Information operation will be applied only to the selected module or main program. Variables that are in a module are stored in the variable information file with the module name so that the same variable names can be used in modules and the main program with no confusion. There are several important applications for variable information files. The first application is to provide different sets of guess values for a problem that has difficulty converging. Each set of guesses can be stored in a separate file and loaded as needed. A more general application is to use a variable information file to store information for variables that you use repeatedly in your problems. For example, if you commonly use variables T1, T2, and T3 in your problems, you can set their guess values, limits and units in the Variable Information dialog and Save the information in a Variable information file. Then, when preparing your next problem, you can open this variable information file and the guess values, limits and units will be automatically updated. Used in this way, the variable information files provide a similar capability to that available with the Default Variable Information command, but in this case, the saved information does not need to relate to the first letter in the variable name. The information in a .VAR file can be automatically loaded using the$Include directive (Chapter 7). 110 Menu Commands Function Info will bring up the following dialog window. Chapter 3 The six buttons at the top of the dialog window indicate which information is to be provided. Math functions, Fluid properties, and Solid/Liquid properties refer to the builtin mathematical functions and the thermodynamic and transport property functions for fluids and solids (See Chapter 4). The User Library button provides a list of the user functions, procedures, and modules loaded from Library files. (See Chapter 5 for additional information on Library files). The External Routines button refers to external routines which can be linked to EES as described in Chapter 6. The lower right button provides access to the user-supplied Visual Access libraries. Information on how to add content to this control is provided in Chapter 7. The functions corresponding to the selected button will be displayed in the Function list on the left. To select a function, click on the function name in the scrollable list. Click the Function Info button to obtain specific information relating to the function you have selected. The Fluid Info button provides information relating to the source and range of applicability of the property correlations. The units of the thermophysical property function are shown in the function list box. Thermophysical property functions require specification of a substance. The substances for which property data are available are shown in the Substance list on the right. Click on the substance name in the scrollable list to select the substance. ‘Ideal gas’ will appear above the substance list if the properties of the selected substance are calculated using ideal gas law approximations. ‘Real substance’ will appear if liquid and vapor states are 111 Chapter 3 Menu Commands determined. Substances represented by their chemical formula (e.g., CO2) are modeled as an ideal gas and use JANAF table reference values for enthalpy and entropy. Substances with their name spelled out (e.g., CarbonDioxide) are modeled as real fluids and do not use JANAF table reference values. Air is an exception to this rule. Air is modeled as an ideal gas. Psychrometric functions are applicable only to the substance AirH20. Additional information regarding all built-in functions is provided in Chapter 4. Thermophysical functions may require between 0 and 3 independent properties depending on the choice of function and substance. If the function requires independent properties, a box will appear with drop-down menus listing the alternatives available for the selected function-substance combination. The example box will display a sample use of the function with the selected independent properties. The small index edit box at the right of the example box provides a convenient way to customize the display in the example box. The text in the edit box is appended to each thermodynamic variable. For example, if the text in the index edit box above were changed from _1 to [1], the example box would then display h[1]=ENTHALPY(Steam,T=T[1],x=x[1]). You can also edit the information in the Example text box if you wish. Click the Paste button to copy the text in the Example box into the EES Equation window at the cursor position. Unit Conversion Info provides information to support the use of the Convert and ConvertTemp conversion functions. The Convert function has the following format: Convert('From', 'To') where From and To are character strings identifying the unit type such as 'Btu/hrft2-R' or 'mph'. (Note that the single quotes marks around the unit identifies are optional.) Many of the unit identifiers are obvious, but not all. The purpose of this command is to list the unit identifiers that have been defined, as shown below. Click on the dimension in the list at the left. All of the units which have been defined with the selected dimension are listed in the list on the right along with some unit combinations that have the same dimension. For example, if you click on Area, a list of units have dimensions of area will be displayed. Click on any two units in the list of the 112 Menu Commands Chapter 3 right to see the conversion and inverse conversion factors relating them.. Any combination of units having the dimensions indicated at the top of the right list (e.g., L^2 for Area) can be used in the Convert function. You can add additional units if needed. They are stored in the UNITS.TXT file in the main EES directory. Instructions for adding information are provided at the top of the file. This file may be read as a text file and edited in Notepad. Unit System provides a dialog window shown below in which the units of the variables used in the built-in mathematical and thermophysical property functions may be set. The unit settings are displayed in the Solution window. The unit system is only needed for the built-in function calls. EES does not provide automatic unit conversion but it can optionally check the unit consistency of each equation. The units will be changed for the remainder of the work session if the OK button is pressed. The selected units are saved with other problem information when the Save command in the File menu is issued. These units are then restored with the problem using the Open command. If you wish to permanently change the default values, press the Store button. 113 Chapter 3 Menu Commands Tolerances will display a dialog with two tabbed windows allowing a specification of Stop Criteria and Integration auto step parameters. The stop criteria are the number of iterations, the maximum relative residual, the maximum change in a variable value from one iteration to the next and the elapsed time. If any of these criteria is satisfied, the calculations terminate. All calculations in EES are done in extended precision with 21 digits of significance. Loss of precision is unlikely to be a problem even when very small values are set for the maximum residual or variable change. However, small values for these quantities increase the number of iterations required for a solution and therefore the computation time. The stop criteria will be set as displayed for the remainder of the session by pressing the OK button. The stop criteria are saved with other problem information when the Save command in the File menu is issued and restored using the Open command. To change the default stop criteria that EES presents at the start of a new session, press the Store button. 114 Menu Commands Chapter 3 EES uses numerical integration to determine the value of an integral or to solve differential equations. The equation-based Integral function can use either a fixed usersupplied step or an automatic step adjusted to meet some accuracy criteria. The parameters in this tabbed section of the Tolerances dialog only affect the step size that EES automatically selects during numerical integration with the equation-based integral function. The two radio buttons control whether EES will use a fixed or a variable step. If the "Use fixed step size' button is selected, EES will not attempt to adjust the step during calculation, but rather use a fixed step equal to the interval divided by the number of steps indicated by the user. If "Vary step at intervals of" is selected, EES will check the numerical situation of the integration process every N steps where N is input by the user. During this checking process, EES may decrease, increase, or maintain the current step size. The minimum and maximum allowable steps and tolerances which control whether the step size is changed are input by the user. The test that is done is as follows: Every N steps EES will compare the value of the integral for that step with the value obtained using two half steps. The difference between these two values is the truncation error. The truncation error is normalized by dividing it by the value of the integral for the two half-steps, assuming that it differs from zero. If the normalized truncation error is greater than the value provided for 'Reduce step if rel. error >' the step size if reduced, assuming that it is greater than the minimum allowable step size. If the normalized truncation error is less than the value provided for 'Increase step if rel. error <', the step is increased, provided that the increased step size does not exceed the maximum allowable step. Otherwise, no change is made to the step size. Richardson extrapolation is provided as an option when the equation-based Integral function is used with a fixed step size. A fixed step size can either be specified in one of two ways. The step size can be specified (as the fifth parameter) in the equation-based integral function. Alternatively, if a step size is not provided in the function, EES will use the step size setting indicated in the Integration tab of the Tolerances dialog. Richardson extrapolation can be employed if the 'Use fixed step size' radio button is selected. Richardson extrapolation is a clever technique to reduce the truncation error associated with numerical integration. An explanation of this technique can be found in Numerical Methods for Engineers by S.C. Chapra and R.P. Canale, McGraw-Hill, 1985. Default Info provides a means for specifying the default guess values, bounds, display format and units of new or existing variables depending on the first letter in the variable name. There are two ways to use this command. If the problems you do all tend to have the same nomenclature, it is best to set the default variable information and save it by pressing the Store button. The Store button will cause the current default settings to be permanently saved so that these defaults will appear at the start of the program the next time EES is run. 115 Chapter 3 Menu Commands The Default Variable Information command can also be used to selectively change information for existing variables. For example, if you change the units for variables beginning with letter T to [K] and press the OK button, all existing variables beginning with letter T will take on these new units. No other changes to existing variables will be made. Each new variable beginning with letter T will then also take on units of [K]. The OK button sets the current default setting for this problem session only. Show/Hide Diagram Tool bar is enabled when the Diagram window or a child Diagram window (Professional version) is foremost. When enabled, selecting this command will toggle the state of the tool bar for the foremost Diagram window. When the tool bar is visible, the Diagram window is in development mode. Text and graphic objects such as (lines/arrows, rectangles, and ellipses) may be moved, changed or deleted in development mode. An Align button is provided to facilitate alignment of objects relative to one another. When the tool bar is hidden, all text and graphic objects are locked and the window is in application mode. Input is accepted for input variables and calculations can be initiated using the input variables supplied in the Diagram window. The tool bar visibility can also be toggled using the Diagram Window button on the speedbutton bar just below the menu bar. See the Diagram window section in Chapter 2 for more detail. Preferences provides six tabs for user choices concerning program options, general display options, equations display, printer display, plot window, and complex number options. These options are shown and described below. If the OK button is clicked, the selected preferences remain in effect for the remainder of the work session. The Store button saves the preferences so that they will be in effect at the start of the program the next time EES is run. 116 Menu Commands Chapter 3 Autosave every XXX minutes instructs EES to save all information at regular intervals. The information is saved to a temporary .EES file that has the same name as the open EES file, but with a tilde (~) preceding the filename. For example, file C:\EES32\ABC.EES will be autosaved as C:\EES32\~ABC.EES. Under normal operation, the autosave file is deleted when a new file is created or opened or when EES is closed at the end of the worksession, so do not depend upon it for permanent storage. You should always save any file that you intend to use at a later time using the Save or Save As commands. However, if EES quits unexpectedly, the last saved copy of the backup file should still be available in your directory. Allow = in function/procedure equations will suppress the error message that would normally occur if the assignment symbol (:=) is not used in EES Functions and Procedures. EES Internal Functions and Procedures (Chapter 5) employ assignment statements as in FORTRAN and Pascal, rather than equations as used in the main body of the EES programs. (EES modules use equality statements as in the main body of the EES program and thus cannot use the := assignment statement syntax.) An assignment statement sets the variable identified on the left of the statement to the numerical value on the right. X:=X+1 is a valid assignment statement, but it obviously is not an equality. The := sign is used to signify assignment, but if this control is selected, EES will also accept X=X+1. Show function/procedure/module values will allow the most recent values of local variables in EES functions, procedures and modules to be displayed in the Solution window. Module equations will also appear in the Residuals window. The values of these local variables are ordinarily not of interest but you may wish to know them, particularly for debugging purposes. Only the Functions, Procedures, Modules, and Subprograms which appear in the Equations window are affected by this setting. The local values of variables in Functions, Procedures, Modules, and Subprograms that have been loaded from library files (See Chapter 5) are not displayed. 117 Chapter 3 Menu Commands Hide Solution Window after change causes the Solution, Arrays, and Residual windows to be removed from the screen display if a change is made in the Equations window. If this option is not selected and a change is made in the Equations window, the Solution window title will change to Last Solution. Include a Sum row in Parametric Table will result in an extra row being added to the Parametric table which displays the sum of the values in each column. If the table is currently displaying results from the Uncertainty table calculation, the sum row will display the uncertainty of the summed values, i.e., the square root of the sum of the squared uncertainty values from each row. Place array variables in the Arrays Window instructs EES to display all array variables in the Arrays window rather than in the Solution window after calculations are completed. Values in the Arrays window can be plotted and copied just like values in the Parametric and Lookup tables. See the Arrays Window section of Chapter 2 for additional information. Display warning messages will enable or disable warning messages during calculations. Warnings are issued if thermophysical property correlations are applied outside of their range of applicability. Warnings can also be turned on or off using the $Warnings On/Off directive in the Equations window or by clicking the Warnings On/Off field in the Equations window status bar. Maintain a list of recent files in the File menu enables or disables a list of up to 8 recent files at the bottom of the File menu. This list is a convenience that you normally would want to have. The file names are stored in a file entitled EES.FNL in the EES directory. However, if EES is placed on a server where multiple users can access the program, it is best to disable this feature. (This capability is disabled for educational versions.) Display menu speedbar controls the visibility of the toolbar appearing below the menu bar. The toolbar will be hidden if this control is unselected. Check Units automatically will, if enabled, check the unit consistency of each equation when the Solution Window or Residuals window is displayed. If the Show function/procedure/module values option in this dialog is enabled, the unit consistency for equations in internal functions, procedures, modules and subprograms will also be reported. This option can also be turned on or off with the$CHECKUNITS AutoON/AutoOff directive. Check units automatically will, if enabled, check the unit consistency of each equation when the Solution Window or Residuals window is displayed. 118 If the Show Menu Commands Chapter 3 function/procedure/module values option in this dialog is enabled, the unit consistency for equations in internal functions, procedures, modules and subprograms will also be reported. This option can also be turned on or off with the $CHECKUNITS directive. Set units automatically when possible will, if enabled, cause EES to enter the units of variables for which the units have not been previously specified. Units will be set only when a variable is by itself on the left hand side of an equal sign and a unit warning would otherwise occur. Note that the same effect can be accomplished using the$AutoSetUnits directive. Use enhanced convergence techniques will, if checked, algebraically rearrange equations into equivalent forms that converge more readily, reducing the need to provide guess values. The font and font size can be selected from the drop-down lists. The new font and font size will display in all of the EES windows. The printer display is unaffected. The printer font and font size is selected separately in the Printer Display Tab. The Use thousands separator will display values with a thousands separator. However, the thousands separator is not used to input values. Display subscripts and Greek symbols controls the appearance of EES variables in the Solution, Formatted Equations, Parametric Table and Diagram windows. If this option is selected, the underscore will be used to signify the start of a subscript. The following characters in the variable name will be displayed in smaller type and lower case. Additional underscores within the same variable name will be changed into commas. Array variables 119 Chapter 3 Menu Commands will also be changed to appear as subscripted variables. Variables which have the name of Greek symbols, such as alpha, beta, and gamma, will appear in Symbol font. If the variable name is entirely in capital letters, the Greek symbol will be shown as a capital letter. A dot, bar, or hat can be positioned over the variable name by adding _dot, _ddot, _bar, _hat or _tilde to the name. For example, X_dot will display as X . X_infinity will display as X ∞ . ˆ X_star will display as X*. X_hat will display as X . The vertical bar character signifies the start of a superscript. For example, G|o will be displayed as G o . The Calculated Table Values and Entered Table Values pertain to the display of values in the Parametric Table. Entered table values are values which are provided by the user, either directly by typing the value or indirectly through application of the Alter Values dialog. Calculated values are provided by EES during the Solve Table or Min/Max Table commands. Two fields are provides for each category to set the color and the font style of the display. Note that a separate font style can be selected for printing in the Printer Preferences tab. EES can display comments in two different colors and/or styles which are selected by the user with the two drop down controls that follow the comment type label. Comment Type 2 is distinguished from Comment Type 1 by having an exclamation character ! as the first character in the comment. Both Type 1 and Type 2 commands must be enclosed within braces or single quotes. If braces are used, the comment will be displayed in the Equations window but not in the Formatted Equations window. For example, {!This is a Type 2 comment} "!This is also a Type 2 comment and it will display in the Formatted Equations Window} "This is a Type 1 comment." Function names (such as ENTHALPY, SIN, etc.) and keywords (such as FUNCTION, DUPLICATE, fluid names, etc.) can be displayed in upper case, lower case, or as typed, as selected with the drop-down controls. 120 Menu Commands Chapter 3 Wrap long lines in the Equations window will hide the horizontal scroll bar. Lines which are too long to be displayed in the Equations window will be broken at an appropriate point and continued on the following line. A red > symbol will be displayed in the left margin of continuation lines if Display line-break indicator is selected. Display line-break indicator is applicable only if the Wrap long lines option is selected. This option controls whether line break characters appear in the left margin of continuation lines. Display uniform case for variable names causes each variable to appear with the upper and lower case lettering sequence set in the first occurrence of the variable in the Equations window. If the first occurrence of the variable is changed, the Check/Format command in the Calculate menu will change all other occurrences. The Tab Stops edit field allows up to five tab stops to be set for use in the Equations window. These tab setting can also be specified with the $TABSTOPS directive which overrides this setting in the Preferences dialog. The options in the Printer Tab only affect the appearance of the printed output. Font and size provide choices for the type in which the printed output will appear. Printed output line spacing provides single, space and one-half, or double-space options. Printed comment style 1 and Printed comment style 2 fields allow a font style to be set for each comment type. Comment type 2 is distinguished from comment style 1 by having an exclamation mark (!) as its first character. These controls allow the comments to be printed in a different style than is displayed on the screen. This option is particularly useful when the comments are displayed in color on the screen but are to be printed on a black and white printer. A Print in Color control is provided in the Print dialog window. 121 Chapter 3 Menu Commands The Plot Options tab allows the default setting for the plot width and height, the font, font size, font style, and the major and minor tick sizes for the axis scales to be changed. The plot width and height are entered in point units. Depending on your equipment and video setting, a point is either 1/96 or 1/120 inch. Ticks are the short line segments on the axis scale. Major ticks are placed on the scale at the point where the axis numbers appear whereas minor ticks occur between the axis numbers. Ticks which are drawn into the plot rectangle are represented with positive numbers. The plot can be configured for outdented ticks by specifying negative values for the tick sizes. These default characteristics are applied whenever a new plot is generated. The controls in the Clipboard Copy box affect the manner in which plots from EES are transmitted to other applications. The plot will be copied to the clipboard as a picture (enhanced metafile), as a bitmap, or as both a picture and bitmap depending on the setting of the radio buttons in the Copy as box. The resolution of the copy may be specified as 100, 300, 600, or 1200 dots per inch. The default value is 300 dots per inch. Higher resolutions generally produce a better image, but in the case of the bitmap copy, they result in much greater memory utilization particularly if the copy is done in color. After a plot has been copied to the Clipboard, it can be pasted into another application using the application's Paste or Paste Special command. If the plot is copied as both a picture and bitmap, the paste special command provides a choice of picture, picture (enhanced), bitmap, device independent bitmap. Selecting Picture will paste the enhanced metafile. The device independent bitmap will paste the bitmap. You may want to test both of these options to see which provides the best choice for a high quality image in your application. The Copy in Color check box controls whether the Copy command will reproduce the plot in color or in black and white. 122 Menu Commands Chapter 3 The Complex Numbers Tab allows the complex algebra capability in EES to be turned on or off. The complex capability can also be turned on or off with the$COMPLEX ON/OFF directive. The imaginary variable name representing the square root of –1 can be designated to be either i or j depending on the radio button setting. Complex mode can also be turned on or off but clicking on the Complex field in the status bar of the Equations window. The Default File Folder tab specifies the folder that EES will use for the Constants.txt, Units.txt and the units list (*.unt) files. If this field is left blank, the default file folder will be the same folder that the EES application is located int. The Constants.txt, Units.txt and default .unt files found in the specified folder will be opened and read, replacing the information that may have been read earlier. Also, EES will use the Default file folder whenever the Open or Save As... command is issued. If the directory specified 123 Chapter 3 Menu Commands in this field does not exist or if no directory is specified, EES will initially use the file folder that EES is located in and thereafter, it will use the last accessed folder. The Default file folder provides a method of allowing each use to have his or her own personal settings although EES may reside on a write-protected network. Note that the Default directory information is stored in the EES.prf file. This file must be loaded in order to determine the default directory information. EES will automatically load the EES.prf file found in the same directory as the EES application. An existing .PRF file can be loaded from any directory with the Load button in the Preferences dialog or with a $INCLUDE directive. When EES is started, it transparently loads library files from the USERLIB folder located in the directory in which the EES application is located. However, if a valid directory name is provided in the Additional user library folder field, EES will use also open all of the library files in this directory at startup. The Default Macro folder holds files used when the Build Macro command (Professional vesion) is issued. If no folder name is provided, EES will use the directory in which EES is located. The Sounds tab allows the sounds that EES generates for different situations to be customized. Click the arrow to the right of the sound file name to play the sound. In any of the Preferences in any of the tabbed windows are changed, pressing the OK button will set the Preferences for this session only. The Store button will cause the Preferences to be permanently saved in a user-specified file. The usual name and location for this file is EES.prf in the same directory as the EES application. EES will automatically load the EES.prf file in the when it starts so that the default settings will be 124 Menu Commands Chapter 3 in effect at the start of the program the next time EES is run. However, if EES is running off of a write-protected network or if there are multiple users on the same computer, it is better to store the default setting in a personal location. These default settings can be loaded at a later time using the Load button in the Preferences dialog. Note: If EES is started from a short-cut, it is possible to specify the starting directory by right-clicking on the short-cut and entering the starting directory in the short-cut properties. If EES finds the EES.PRF file that contains the user preferences in this starting directory, it will use it rather than the EES.PRF found in the EES directory. This provides a way for each user to have unique preferences. 125 Chapter 3 Menu Commands The Calculate Menu Check/Format will recompile all equations and apply the formatting options selected with the Preferences command in the Options menu. The first syntax error found will be indicated with a message. If no syntax errors are encountered, EES will indicate the number of equations and variables in the Equations window. Solve will first check the syntax of the equations in the Equations window. If no errors are found and if the number of equations is equal to the number of variables, a solution to the equation set will be attempted. The methods used by EES for solving equations are described in Appendix B. An information dialog window summarizes the progress of the solution. When the calculations are completed, the information dialog indicates the elapsed time, number of blocks, the maximum residual (i.e., difference between the left and right hand sides of an equation), and the maximum change in the value of a variable since the previous iteration. If the number of equations is not equal to the number of variables, EES will provide the option of viewing the Debug window which may help locate a problem. If the Diagram window is being used to enter one or more variable values, it must be open when the Solve command is issued. See Chapter 2 for more information concerning the Debug and Diagram windows. Solve Table will initiate the calculations using the Parametric Table. (See the description of Table menu commands on the following pages for information on the use of the Parametric Table.) The dialog shown below will appear. More than one Parametric tables may be defined in which case the table for which the calculations are to be done must be selected from the drop-down list. One of the choices in the drop-down list is “All Parametric Tables”. Choosing this option results in EES doing the calculations for all of the Parametric tables in sequential order. 126 Menu Commands Chapter 3 Each row in a Parametric Table is a separate problem. The values of independent variables are shown in normal type. Blank cells (or cells with bold, blue, or italic type from a previous Solve Table command) are dependent variables. The values of these variables will be cleared and the newly calculated values will be entered in the table. If the Update guess values control is selected, the guess values for each run will be set to the calculated values from the previous run; otherwise each run will be initiated with the guess values specified with the Variable Info command. If the Stop if error occurs control is selected, EES will terminate the table calculations on the run at which the error occurred. Otherwise, EES will continue the calculations for the remaining rows. A message will be displayed after the table calculations are completed indicating the rows in which a error occurred. The Use input from Diagram control will be enabled if the Diagram window is open and if it has one or more input variables. If this control is selected, EES will accept input values from the Diagram window, just as if these inputs were specified in the Equations window. EES will automatically check units if the Check Units Automatically control in the Options tab of the Preferences dialog is selected. A warning dialog will appear if any unit problems are found. The Show unit checking warnings control allows this warning dialog to be disabled. In the Professional version, the start and stop runs for the Parametric table calculations can be set to EES variables. Clicking in the First Run box will allow a selection of First Run Number or First Run Variable. If First Run Number is selected, a number corresponding to the first row in the Parametric table for which calculations are to be done is entered. If First Run Variable is selected, a drop down list appears from which an EES variable can be selected. 127 Chapter 3 Menu Commands Min/Max is used to find the minimum or maximum of an undetermined variable in an equation set for which there is at least one and up to 20 degrees of freedom. EES will first check the syntax of the equations in the Equations window. If no errors are found, a dialog window will appear presenting the undetermined variables in two lists. Click the Minimize or Maximize button above the left list. The variable which is to be minimized/maximized is selected by clicking on its name in the list on the left. The independent variable(s) whose value(s) will be changed in searching for the optimum appear in the list on the right. It is necessary to select as many independent variables as there are degrees of freedom in the Equations window. The number of independent variables which must be selected is indicated above the right-hand list. To select (or unselect) a variable, click on its name in the list. If there is one degree of freedom, EES will minimize/maximize the selected variable using either a Golden Section search or a recursive quadratic approximation method, depending on the settings of the buttons at the bottom of the dialog window. (See Appendix B for information on the optimization algorithms.) The recursive Quadratic Approximations method is usually faster, but the Golden Section method is more reliable. Multi-dimensional optimization may be done using Direct Search, the Variable Metric algorithm or the Genetic method (Professional version). The Variable Metric method, which uses numerical derivatives, usually performs much better than the Direct Search method, but it may be confounded if the optimum is constrained to be on a bound. The Genetic method nearly always finds the global optimum but it is slow. The Nelder Mead simplex method does not use derivatives and is effective for some optimization problems. 128 Menu Commands Chapter 3 EES requires finite lower and upper bounds to be set for each independent variable. Careful selection of the bounds and the guess value(s) of the independent variables will improve the likelihood of finding an optimum. You can view or change the bounds and guess value for each selected independent variable by clicking the Bounds button. This will bring up an abbreviated version of the Variable Info dialog containing just the selected independent variables. See the description of the Variable Info command in the Options menu for additional information on setting the bounds. The maximum number of times in which the equations are solved (i.e., the number of function calls) may be specified, along with the relative tolerance. Calculations will stop if: 1) the relative change in the independent variable(s) between two successive steps is less than the specified tolerance; or 2) the number of steps exceeds the specified maximum. EES will also stop the calculations if the equations cannot be solved with specified value(s) of the independent variables within the tolerance and allowable number of iterations specified with the Stopping Criteria command in the Options menu. The Professional version allows the optimization results to be written to a file. The values of the dependent variable and the independent variables are output to a specified text file for each iteration. Min/Max Table provides the same capability as the Min/Max command, except that the calculations will be repeated for each row in the Parametric Table. (See the description of Table menu commands on the following pages for additional information on the use of the Parametric Table.) As with the Min/Max command, a dialog window will appear in which the variable to be maximized or minimized and the independent variable(s) can be selected. In this case, however, the variable which is to be optimized and all of the independent variables (whose values will be varied in seeking the optimum) must appear in the Parametric Table. The start and stop runs in the Parametric Table for which the calculations will be done may be specified. Values in the Parametric Table which are shown in normal type are fixed and are treated just as if they were set to that value with an equation in the Equations window. The variable which is to be optimized and the independent variable(s) must be the same for each run. If no errors are encountered, the optimum is computed and the values of the remaining columns in the table are entered for each run. Uncertainty Propagation determines the uncertainty of up to 30 calculated variables as a function of the uncertainties of one or more measured values upon which it depends. In many experiments, an important quantity is not directly measured but is rather calculated as a function of one or more variables that are directly measured, i.e., Y = f( X1, X2, ....). The measured variables, X1, X2, etc. have a random variability which is referred to as its uncertainty. In EES, that uncertainty is displayed with a ± symbol, e.g., X1 = 300 ± 2. 129 Chapter 3 Menu Commands The purpose of this command is to calculate how the uncertainties in all of the measured variables propagate into the value of the calculated quantity, Y. The method for determining this uncertainty propagation is described in NIST Technical Note 1297 (Taylor B.N. and Kuyatt, C.E., Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, National Institute of Standards and Technology Technical Note 1297, 1994). Assuming the individual measurements are uncorrelated and random, the uncertainty in the calculated quantity can be estimated as UY = F ∂Y I G ∂X J U HK 2 i i 2 Xi where U represents the uncertainty of the variable. After selecting this command, EES will present two lists of variables. Select the variable for which the uncertainty propagation is to be determined from the list on the left. Select one or more measured variables from the list on the right. Note that the variables appearing in the measured variables list must be constants so that their values are set to a numerical constant with an equation in the EES Equations window. To specify the uncertainty associated with the measured variables, click the Set Uncertainties button below the right list. A second dialog window will appear in which the absolute or relative (fraction of the measured value) uncertainties for each selected measured variable can be specified. An uncertainty value for each measured variable must be provided. Click the OK button to set the uncertainties and close the Specify Uncertainties dialog window. Click the OK button Uncertainty Propagation dialog to start the calculations. Note that the variables initially appearing in the Measured variables list are constants, i.e., values that are independent of the values of other variables. However, some variables (shown in red) that initially appear in the Calculated variable list can be moved to the Measured variables list. For example, consider the following simplistic set of equations. Row=1 X=Lookup('Lookup 1',Row,1) Y=Lookup('Lookup 1',Row,2) Z=X^2+Y^3 In this case, X and Y are read from the first row of a Lookup table. Z is a function of X and Y and the uncertainty propagation of X and Y into Z is to be determined. Selecting the Uncertainty Propagation command produces the following display: 130 Menu Commands Chapter 3 Row is the only variable initially appearing in the Measured variables list since it is the only variable that is completely independent of all other variables. However, X and Y (which are both functions of Row) can be moved the Measured variables list by selecting each variable and then clicking the arrow button (or dragging the selection to the Measured variables list). After this is done, the display will appear as: After the calculations are completed, EES will display a Solution window with two tabs, as shown below. The Uncertainty Results tab displays the calculated and measured variables and their respective uncertainties. The partial derivative of the calculated variable with respect to each measured variable will also be displayed. In addition the % of the total uncertainty in the calculated variable resulting from the uncertainty in each measured variable will also be displayed. This % is calculated as the ratio of the square of the product of the partial derivative and uncertainty of each measured variable to the square of the uncertainty in the calculated variable. The Solution tab shows the Solution window as it would normally appear without the uncertainty calculations. 131 Chapter 3 Menu Commands Uncertainty Propagation Table provides the same function as the Uncertainty Propagation command, namely the determination of the uncertainty propagation in a calculated variable. The difference is that this command allows the uncertainty calculations to be repeated for one or more measurements by using the Parametric Table. NOTE: The calculated and measured variables must all be in the Parametric Table. After selecting the command, the Uncertainty Propagation dialog window will appear in which the calculated quantity is selected from list of variables on the left and the measured variable(s) are selected from the list on the right. Click the Set Uncertainties button to set the uncertainty value associated with each measured variables. Note that the uncertainty value can be provided as a variable in the Parametric table. The Parametric Table calculations will proceed after the OK button is selected. The value and uncertainty for the calculated variable and each measured variable will be displayed in the Parametric Table after the calculations are completed. The calculated variable can then be plotted with error bars representing the propagated uncertainty using the New Plot Window command. If the Sum row in the table has been made visible with the ‘Show Sum Row in Parametric table’option in the Preferences dialog or with the$SUMROW ON directive, the sum row will display the uncertainty of the summed values which is the square root of the sum of the squared uncertainty values from each row. Check Units will check the dimensional and unit consistency of all equations in the Equations window. The unit checking will be extended to equations in internal functions, procedures, Modules and Subprograms if the Show Function/Procedure/Module values option in the Options tab of the Preferences dialog is selected or if a LOCAL ON directive is provided in the Equations window. The results are reported in the Debug window. It is necessary to enter the units of each variable for the checking process to function properly. The units can be entered in the Variable Info dialog window or in the Solution window. In addition, selecting the variable in the Equations window and rightclicking the mouse will bring up a pop-up menu with a Variable Info menu item that allows the units of the selected variable to be entered. The units of a constants in the 132 Menu Commands Chapter 3 Equations window can be set by following the value with the units enclosed in square brackets. For example: P=140 [kPa] “this line will set P=140 and its units to kPa” Unit consistency can be obtained by specifying the units of a constant or by using the Convert function. For example, suppose you have two variables, L_inch and L_feet, whose units are set to inches and feet, respectively which are used in the following equation. L_inch=L_feet*12 When the Check Units command is issued, the Debug window will appear and this equation will be flagged as having an error because the units of 12 are not known. This problem can be corrected by either entering the units for 12 L_inch=L_feet*12 [in/ft] or by using the Convert function. L_inch=L_feet*convert(ft,in) The Check Units command will display the equation and an explanatory message for each equation that is found to have dimensional consistency or unit consistency errors. If you click the left mouse button on an equation, the focus will jump to that equation in the Equations window. If you click the right mouse button on an equation, an abbreviate form of the Variable Information dialog window will appear showing just the variables that appear in that equation. Update Guesses replaces the guess value of each variable in the Equations window with the value determined in the last calculation. This command is accessible after calculations have been successfully completed. Update Guesses improves the computational efficiency of an EES calculation since it ensures that a consistent set of guess values is available for the next calculation. Exactly the same function is provided with the Update button in the Variable Info dialog window, but the Update Guesses command is more accessible. Reset Guesses replaces the guess value of each variable in the Equations window with the default guess value for that variable. Unless otherwise specified, EES assumes all guess values are 1.0. You can change the default guess values with the Default Info command in the Options menu. You should reset the guess values only if you are experiencing convergence difficulties and you have changed the guess values in an attempt to find a solution. Reset Guesses will not change the lower and upper limits. Reset Limits replaces the lower and upper limits of each variable in the Equations window with the default limits for that variable. 133 Chapter 3 Menu Commands The Tables Menu New Parametric Table creates a new Parametric Table in the Parametric Table Window. Parametric Tables are used in EES to automate repetitive calculations, to solve differential equations, and to present data for plotting or curve-fitting. A dialog window will appear in which information must be entered to create the table, as in this example. There is no limit on the number of tables that can be created, other than available memory. Each table is identified with a table name that is entered when the table is created. The table name is displayed on a tab at the top of the Parametric Table Window. The table name can later be changed by clicking the right mouse button on the tab. The number of runs, which corresponds to rows in the table, is entered in the field at the top. All variables (both independent and dependent) which are to appear in the table are selected 134 Menu Commands Chapter 3 from the alphabetical list of variables on the left. To select a variable, click on its name in the list, which will cause it to be highlighted. Multiple names can be selected. Click the Add button to move the highlighted variable names to the list on the right. (As a shortcut, a variable is automatically added to the list on the right when you double-click on its name in the list on the left.) The variables in the right-hand list will appear in the columns of the table in the same order in which they appear in the list. A variable can be removed from the table list by clicking on its name in the right list and then clicking the Remove button or by double-clicking on the variable name. Pressing the OK button will create the Parametric Table, overwriting any existing table. The Parametric Table operates somewhat like a spreadsheet. Numerical values can be entered in any of the cells. Entered values are assumed to be independent variables and are shown in normal type. Entering a value in a table produces the same effect as setting that variable to the value in the Equations window. Dependent variables will be determined and entered into the table in blue, bold, or italic (depending on the choice made in the Preferences dialog) when the Solve Table, Min/Max Table, or Uncertainty Propagation Table command is issued. If a variable is set in the table, it can not also be set in the Equations window; otherwise the problem will be overspecified. Each row of the table is a separate calculation. The independent variables may differ from one row to the next. However, for every row, the number of independent variables plus the number of equations must equal the total number of variables in the problem. Alter Values provides an automatic way to enter or clear the values of a variable for multiple runs in one or more tables. This command will bring up the Alter Values dialog, shown below. When there is more than one Parametric table, the Alter Values command initially shows data for the Parametric table that is formost. If there is more than one Parametric Table, clicking on the table name will allow other Parametric tables to be chosen. It is possible 135 Chapter 3 Menu Commands to have the Alter Values dialog operate on more than one table. To do so, click on the table name or the down arrow at the right of the table name. The list of available Parametric tables will be displayed. Hold the Shift key down while clicking on the table names in this dropdown list to select or unselect the tables for which the changes will be applied. The runs (i.e., rows) affected are specified at the upper left of the dialog. The variable for which changes are to be made is selected from the list by clicking on its name. The column for this variable will be cleared if the Clear Values control is selected. If Set Values is selected, values for the selected variable will be entered automatically in the table starting with the value in the First Value field. The list box below the First Value controls the manner in which successive values in the table are generated. The choices are Last Value, Increment, and Multiplier. Increment or Multiplier result in successive values in the table being determined by either adding or multiplying, respectively, the preceding table value by the value provided in the box. If Last Value is selected (as shown) the increment will be selected such that the last run has the specified value. The Apply button will change the Parametric table as specified but control will remain in the Alter Table Values dialog window so that additional changes can be made. The OK button accepts and finalizes all of the changes made to the Parametric table. The numerical values entered in a table, either directly or through the Alter Values command, identify independent variables in the equation set; they are shown in normal type. Independent variables are fixed to a constant for each run, just as if there were an equation in the Equations window setting the variable to the constant. Dependent variables are shown in italic, blue or bold depending on the choice made in the Preferences dialog. These values are automatically entered in the table with the Solve Table and Min/Max Table commands. If a value is set in a table, it must not also be set in the Equations window; otherwise an error message will be displayed. There are other ways of changing the data in the Parametric table. Clicking on the control at the upper right of each column header cell (or selecting Alter Values from the popup menu that appears when the right-mouse is clicked in the header cell) will bring up a dialog window which operates just like the Alter Values dialog. Also, you can simply type the values directly into the Parametric Table. Retrieve Parametric Table will read a specified .PAR file and restore the Parametric table to the same condition it was in when the Store Parametric Table command was issued. See the Store Parametric Table command below for details. Store Parametric Table saves the current Parametric Table to a binary disk file which, by default, has a .PAR filename extension. All information related to the Parametric Table is 136 Menu Commands Chapter 3 saved. The file can later be read to recreate the table with the Retrieve Parametric Table command. The Store and Retrieve Parametric Table commands were originally developed to overcome the limitation of a single Parametric Table in earlier versions of EES. However, EES now allows an unlimited number of Parametric Tables to be defined, so it should no longer necessary to Store and Retrieve Parametric Tables. The Retrieve Parametric Table is provided to allow Parametric Tables saved in older versions of EES to be opened and to allow Parametric Tables from one EES file to be ported to another EES file. Insert/Delete Runs allows the number of runs in an existing Parametric Table (or for selected tables) to be changed by inserting or deleting one or more rows in a specified Parametric table at a specified position. Rows in the Parametric Table can also be inserted or deleted by clicking the right mouse button in the first column of the table and selecting Insert Row or Delete Row from the popup menu. Insert/Delete Variables allows variables in an existing Parametric Table or set of selected tables to be added or removed. The following dialog window will appear. 137 Chapter 3 Menu Commands The list on the right shows the variables which currently appear in the Parametric Table. Variables that may be added to the table appear in the list on the left. To add one or more variables to the table, click on the variable name(s) causing them to be highlighted. Click the Add button to move the highlighted variable names to the list on the right. (You can also add a variable by double-clicking on the variable name.) Variables can be deleted from the table by selecting them from the list on the right, followed by clicking on the Remove button. Variables can also be added or deleted from the Parametric Table by clicking the right mouse button in the column header cell following by selecting Insert Column or Delete Column from the popup menu that appears. Variables will appear in columns of the Parametric Table in the same order as they appear in the list on the right. The order of the variables in this list can be changed by pressing and holding the left mouse button on a variable name while sliding it up or down to a new position in the list. The column order of an existing Parametric table can also be changed by clicking on the column header cell as described in Chapter 2. Delete Parametric Table will, after a confirmation, delete the Parametric Table and recover the memory it required. New Lookup creates a table with the specified number of rows and columns in which tabular numerical or string data may be entered. A name must be provided for the Lookup Table. This is the name that must be used with commands that use the Lookup Table. The name will appear on a tab at the top of the Lookup Table Window. The tabular data may be automatically interpolated, differentiated, and used in the solution of the problem using the Interpolate, Differentiate, Lookup, LookupRow, and LookupCol functions described in Chapter 4. There is no limit (other than available memory) on the number of Lookup Tables that may appear in the Lookup Table Window. In addition, data in the Lookup Window may be saved in a Lookup File (with a .LKT, .TXT. or .CSV filename extension) and the Lookup Files stored in disk files can also be accessed by the Interpolate, Differentiate, Lookup, LookupRow, and LookupCol functions. Lookup tables and files provide a great deal of power to EES by allowing any functional relationship between variables which can be represented by tabular information to be entered and used in the solution of the equations. Open Lookup will read into the Lookup Table Window a Lookup file which was previously stored with the Save Lookup command or as a text file. A name derived from the filename is given to the Lookup Table and this name appears on the tab at the top of the Lookup Table Window. A Lookup file is a two-dimensional table of data that has been stored in a disk file. A name and display format for each column of data may also be stored, depending on the file format. Lookup files can be accessed by the Differentiate, Interpolate, Lookup, LookupCol, and LookupRow commands. EES recognizes both 138 Menu Commands Chapter 3 binary and ASCII forms for Lookup files. Binary files are identified with an .LKT filename extension. ASCII Lookup files usually have a .TXT or. .CSV filename extension. Each file format has advantages and disadvantages. The binary form is read in more quickly and it requires smaller file sizes. The ASCII form is easier to edit and it can be written by spreadsheet or other applications. See Chapter 4, Using Lookup Files and the Lookup Table, for details. Insert/Delete Lookup Rows and Insert/Delete Lookup Cols allows one or more rows or columns to be inserted or deleted at a specified position in an existing Lookup Table. Rows and columns can also be inserted by clicking the right mouse button in the header column (for rows) or header row (for columns) followed by selection of Insert or Delete from the table popup menu. Delete Lookup will delete one or more selected Lookup Tables from the Lookup Table Window and recover the memory it required. There is no Undo for this operation. Save Table provides the ability to save any EES table (Parametric, Lookup, Arrays or Integral) to a file on disk. There are three possible file formats and any one of the three formats can be applied with this command. In addition, the Save Table command allows to be saved with the rows and columns transposed. The three file formats are identified with the filename extension which can be *.txt, *.csv or *.lkt. The .txt file saves the data in a .txt file with tabs between each value and a carriage return at the end of a row of data. Most spreadsheet programs can read data in this format. If 139 Chapter 3 Menu Commands the Include column header information checkbox is checked, the name and unit information of each column in the table will be written to the file. If the Use EES Lookup file text format checkbox is selected, the .txt file will be written in a Lookup table format that allows the column names and units, format information and the data to be read into an EES Lookup table using the Open Lookup Table command. If the Transpose rows and columns checkbox is selected, the rows and columns in the table will be interchanged before the data are stored in the disk file. Transposed data cannot be saved using the .lkt format. The .CSV format saves only the data (no column names or formatting information) as a comma-delimited ASCII file. (Note semicolons are used for European format.) The .CSV format is convenient when you wish to export the data to another application, such as a spreadsheet. The binary format (.LKT) saves the data in the table in the EES binary Lookup Table format. All information in the file including the column heading, units, and display format are saved. The file can then be read into another EES program with the Open Lookup Table command but it is not readable by external programs. Data stored in a Lookup File on disk can be directly accessed with Interpolate, Differentiate, LOOKUP, LOOKUPCOL and LOOKUPROW functions. Note that data can also be moved from any EES table to another table or another application with the Copy and Paste commands. Linear Regression provides regression capability for the data in the Parametric, Lookup, or Arrays tables. Note that the Curve Fit command in the Plot menu also provides regression capability but only for one independent variable. With the Linear Regression command, the data in any column can be regressed as a function of the data in up to 9 other columns. The dialog window shown below appears after the command is chosen. Select the table you wish to operate on from the drop down lists at the upper right and the starting and stopping rows in that table. Specify the dependent variable by clicking on the variable name in the list on the left. The independent variable(s) are selected by clicking on the names in the right list. To de-select an item, click it a second time. 140 Menu Commands Chapter 3 The dependent variable will be represented as a linear polynomial function of the independent variables. The order of the polynomial is set between 0 and 9 by clicking on the 'spin button' up or down arrows. If the cross-terms box is selected then terms involving the product of the independent variables will be included in the correlation. As any information relating to the equation form is entered, a representation of the equation to be fit is displayed in the box at the bottom as shown above. You may exclude some terms from the regression by clicking on the term. This action will display a box around the selected term and enable the Exclude button. Click the Exclude button to remove the term from further consideration. A removed term is displayed within a crossed-out red box as shown above. If you later wish to include an excluded term, click on it. The Exclude button will then be titled Include. Click the Include button. When the form of the equation is that which you want to fit, click the Fit button. If the fitting process is successful, the fitted equation will appear in the display box. The Stats button will been enabled. Clicking the Stats button will provide a table listing all of the coefficients, their associated standard errors, and other statistics such as the root-meansquare (rms) error, the bias error, and the R2 value, as shown below. Coefficients which have been excluded will be represented in the table with stars. The coefficients can be copied to the clipboard by checking the Copy to clipboard box. After a successful fitting process, the Fit button in the Linear Regression dialog window will be changed to Copy and the Cancel button will changed to Done. Either button will 141 Chapter 3 Menu Commands dismiss the dialog window. The Exclude button will become the Plot button. Clicking the Plot button will display a plot of the predicted values of the dependent variable versus the values in the table. The Copy button will first copy the fitted equation to the clipboard. You can then paste this equation into the EES Equations window or into any other application that accepts text. Note, however, that the Copy process will overwrite any other information in the clipboard, such as the coefficients copied from the Linear Regression Coefficients dialog window. 142 Menu Commands Chapter 3 The Plot Menu New Plot Window will display a child menu to generate an X-Y, bar, or contour involving two or more variables defined in the Parametric, Lookup, Arrays, or Integrals Tables as a function of any other variable in that table. Use the Overlay Plot command if you wish to plot in an existing plot window. There is no intrinsic limit on the allowable number of plot windows. Each plot created with this command is placed in a separate window of the Plot Window. All plot windows are saved with other program file information when the Save or Save As commands are applied. Once created, the plots can be modified or copied using the Plot Window controls. The plot windows can have of plot overlays that are created with the Overlay Plot command. The information needed to produce the plot is specified in the New Plot Window dialog. All of the information provided in this dialog window can later be changed using Modify Axes and Modify Plot commands and the Plot Window controls described in Chapter 2. X-Y and Bar Plots 143 Chapter 3 Menu Commands To create an X-Y or bar plot, first select the table from which you wish to plot using the drop-down list controls at the upper right of the window. Enter a name for the plot in the edit box at the top of the dialog. This name will appear on the tab at the top of the Plot Window. The name can later be changed by right-clicking on the tab. The variables to be plotted on the X and Y axes are selected from the lists by clicking on their names, using the scroll bar or up/down arrow keys, if necessary to bring the variable names into view. One or more Y-axis variables can be selected. Clicking on an unselected variable name selects that variable, while clicking on a selected variable unselects it. A separate plot line will be generated for each selected Y-axis variable. All selected variables will be plotted with the same axis scale. EES will automatically select appropriate values for the number of display digits, the minimum and maximum axis values, and the interval when a variable is selected. All of these axis formatting variables may be changed. The two fields to the right of the word Format contain pop-up menus that control the format of the numbers appearing in the scale for each axis. F and E format the numbers with a fixed number of decimal places or exponential notation, respectively. The number in the second field is the number of decimal places (for fixed notation) or significant figures (for exponential notation). Grid lines will be drawn if the ‘Grid Lines’ checkbox control is selected. The number of grid lines and scale numbers is determined by the specified interval value. The plot may be formatted in a variety of ways. Clicking the spin box arrows to the right side of the Line list box toggles the display through a list of the available line types. Click on the desired line type or make a selection with the up and down arrow keys. The plot symbol and line color are chosen in a similar manner. If more than one Y-axis variable is selected, the symbol and color list boxes will display 'auto'. With the 'auto' option, the symbol and color for each plot line will be automatically selected by EES so that each plot line has a different symbol and color. This feature can be overridden by simply selecting the symbol and color. The ‘Spline fit’ control will provide a spline-fit curve through the plotted points. When the ‘Automatic update’ control is selected, the plot will be generated using the current data in the Parametric Table, rather than the data which existed when the plot was first drawn. The plot will be updated as the data in the table are changed. The Data button allows the number of rows and the X and Y axis variables to be viewed or changed. If the ‘Add legend item’ is selected, a text item having the name of the Y-axis variable will be placed at the upper left corner of the plot, preceded by the line and symbol type used for the plot. The legend item text can be moved, changed, or deleted just as any plot window text item, as described in the Plot Window section of Chapter 2. 144 Menu Commands Chapter 3 The “Show error bars” control is accessible only if one or both of the variables selected for plotting have associated uncertainty values specified with the Uncertainty Propagation Table commands. By default, error bars are generated in both the X and Y directions. The X and Y error bars can be individually controlled with the Modify Plot command. X-Y-Z Plots The X-Y-Z plot option generates contours lines and contour color bands indicating the path of a fixed value of the contour variable (Z) in X-Y space. Gradient arrows may be optionally drawn on the contour plot. In addition, a 3-D plot option is provided in the EES3D.exe application. An X-Y-Z plot requires three-dimensional data for construction. The data may be provided in either of two ways from the Parametric, Lookup, Arrays or Integral table windows. If the 3-column data radio button is selected, EES will expect the three dimensional data to be provided in three columns from one of the table windows. The X, Y, and Z variables are then selected from the three lists. If the 2-D table data radio button is selected, EES will assume the column numbers in the table are proportional to the X-coordinate and the rows are proportional to the Ycoordinate. The Z-values will be read from the table. Controls are provided to allow a subset of rows and/or columns in the table to be plotted. The X and Y axis scaling is, by default, set to the number of columns and rows in the table, but it can be changed to provide scaling. 145 Chapter 3 Menu Commands A contour plot is shown above with superimposed gradient arrows. See the Plot Window section of Chapter 3 for an example of a 3-D plot. To prepare a contour plot, the selected data must be interpolated or extrapolated as necessary to provide values of the contour variable Z over the entire range of X and Y at relatively fine intervals. A number of methods were investigated for this task. Two methods are provided: Bi-Quadratic Polynomials and Radial Basis Functions. When Radial Basis Function is chosen, the data are first scaled and then fitted to a function of the form Z x , y = wi j =1 bg N d x − xi + d y − yi + σ 2 2 j j 2 where N is the number of data points, the w values are weighting factors, and s is a relative smoothing parameter which, based on experimentation, is best set to zero for numerically-generated data. However smoothing may be needed for experimental data or for sparse data sets. Moving the Smoothing slider bar to the right increases s which increases the smoothing effect. The weights are found by solving the linear system of N equations that force the above equation to perfectly represent the provided data. Once the weights are determined the equation is used to interpolate or extrapolate the values of Z to particular values of x and y. The computations needed to determine the weights are O(N cubed) so there is a practical upper limit to the number of points (N) that can be accommodated. This upper limit is controlled by the Resolution slider. The range of the Resolution slider is 400 to 1600. If more data points are provided than are specified by the Resolution slider, EES 146 Menu Commands Chapter 3 will select a subset of the data using a clustering algorithm. At full resolution, it is necessary to solve a 1600 x 1600 system so you may have to wait a while for the plot to be prepared depending on the speed of your computer. When Bi-Quadratic Polynomial is chosed, the data are fitted to a second-order polynomial of the form: Z ( X , Y ) = ao + a1 X + a2 X 2 + a3Y + a4Y 2 + a5 XY A separate set of the a coefficients is fitted for each point in the grid using weighted linear least squares. The number of grid points, controlled by the setting of the Resolution slider, ranges from 2,500 to 10,000. Contour plots may be produced using isometric lines or color bands representing constant values of Z. The number of lines or bands is determined by as the difference between the maximum and minimum values divided by the interval value. Each isometric line is a separate plot overlay, whereas the color band plot is simply one plot. A maximum of 25 isometric lines and 250 colors is allowed. Note that selecting a large number of colors (>100) results in a plot that has nearly continuous colors ranging from blue (low values) to red (high values). The resulting plot can be quite pretty, but the time required to display the plot will increase with the number of colors. A Label Contours check box control is provided for isometric contour plots. In this case, EES will generate a text item containing the value for each contour line and place it on the line. These text items can be moved or changed just as any other Plot window text items. If a banded color plot is chosen, an Include Legend check box is provided. If the Include Legend check box is selected, a color legend will be displayed to the right of the plot relating colors to the values of Z. Note that, on a color band contour plot, you can read the value of Z directly in the Plot Window title bar at any X-Y position by holding the Ctrl and Shift keys down and moving the mouse. An X-Y or bar plot can be overlaid on 2 two-dimensional contour plot using the Overlay Plot command. A Label Contours check box control is provided for isometric contour plots. In this case, EES will generate a text item containing the value for each contour line and place it on the line. These text items can be moved or changed just as any other Plot window text items. If a banded color plot is chosen, an Include Legend check box is provided. If the Include Legend check box is selected, a color legend will be displayed to the right of the plot relating colors to the values of Z. Note that, on a color band contour plot, you can read the value of Z directly in the Plot Window title bar at any X-Y position by selecting the cross-hairs tool from the tool menu and moving the mouse. Overlay Plot allows a new plot curve to be drawn over existing plots. The use of this command is identical to that for the New Plot command described above except that it 147 Chapter 3 Menu Commands does not first clear the Plot window. Controls are provided to create or select an existing top x-axis or right y-axis. Modify Plot allows the characteristics of existing plot curves to be changed by manipulation of information in the following dialog window. This command can also be invoked by double-clicking the mouse button within the plot rectangle. The plot for which changes are to be made is selected from the list at the upper left. The plots appear in this list in the order in which they were generated. A (Y2) following a variable name indicates that it is plotted using the right Y-axis. Similarly (X2) indicates that the plot uses the X-axis at the top of the plot. The X-axis and Y-axis scales employed for the selected plot are indicated with the radio buttons at the lower left of the dialog. The axis scales can be changed by clicking on these buttons. The line type, symbol, symbol size, symbol frequency, and color of the plot curve can be changed using the drop-down lists at the lower left. ‘Automatic update’ options may be changed. (See the New Plot Window command for a description of this options. 148 Menu Commands Chapter 3 To enable smoothing, click the check box within the Smoothing group. There are three smoothing options, accessible with a menu box control. The first option is a cubic spline fit that smoothly tries to direct the line through all points. The second option is a polynomial fit. The order of the polynomial is increased by moving the slider bar to the right. The third option is a moving average that is intended to reduce scatter when experimental data are plotted. A slider will appear as shown below. Moving the slider to the right increases the number of data points that are used to compute the moving average and thus reduces the scatter in the data. The plot is updated as the slider is moved so the effects of a change can be viewed. Controls are provided to change the plot window title, the size and characteristics of the plot border, the grid lines and the major and minor ticks. Negative tick sizes are displayed outside of the plot rectangle. Click the Apply button after changing the plot line characteristics and before selected another plot. The plot window will immediately show any changes. A single plot curve may be selectively deleted (leaving all other plots intact) using the Delete button. Legend text for the plot is also deleted. The Delete Plot Window command described below will delete an entire plot window, including all overlays. Note that multiple plots can be selected by holding the Shift key down while clicking (or dragging) the mouse in the plot line list. In this case, the plot line parameters will be displayed for the last selection. If a change is made to a parameter, that change will be applied to all selected plots when the Apply or OK button is clicked. This capability makes it easy to, for example, change the size of the symbols for all plots in the plot window at one time. Other parameters can be changed in a similar manner. However, the data sources (accessed with the Data button) are disabled when more than one plot is selected. It is possible to change the range (First Row and Last Row) of all selected plots at one time provided that they were all plotted from the same table. Clicking the Get Data button will allow the recover the data used to generate the plot. The data will be saved to a Lookup table having a name entered in the prompt that appears when the button is clicked. Modify Axes allows the appearance of the axes of an existing plot to be changed. This command can also be invoked by double-clicking the mouse on the axis scale for which changes are to be made. The dialog window shown below will appear. The axis for which changes are to be made is selected with the radio-button controls at the upper left. The current minimum, maximum, and interval values for the selected axis are shown. These values can be changed and the plot will be redrawn, scaled with the new values. 149 Chapter 3 Menu Commands The #Ticks/Division is the number of minor tick marks in each interval. If selected, Grid lines are normally placed at each major tick mark. However, the #Ticks/Division toggles to #Grids/Division if you click on this control. Grid lines can be placed at positions between the major ticks by setting the No. Grids/Division to a value greater than 0. The display format, font, font size, font style, and color of the scale numbers can be changed using the drop-down menus appearing on the right of the dialog window. These fields will be hidden if the Show Scale checkbox is not selected, in which case a scale will not be drawn. The Professional version also allows the angle of the scale numbers to be specified. Clicking the Apply button applies the changes so that they can be viewed in the Plot window. The OK button accepts the changes and exits the dialog. The Cancel button will restore the plot to the condition it was in before this command was issued. Note that the 2nd axis scales (initially located at the top of the plot for the X axis and to the right of the plot for the Y-axis) can be moved to other locations by holding the Ctrl key down while pressing the arrow keys. The up/down arrows control the position of the X2 scale and the left/right arrows control the position of the Y2 scale. Show/Hide Toolbar controls the visibility of the tool bar that is provided with each 2-D plot window to add new text or drawing items to the plot window or to manipulate these items. The toolbar is ordinarily displayed when the plot window is created. It can be hidden by clicking in the small box with the cross at the upper right of the toolbar. The Show Toolbar command displays the toolbar if it was previously hidden. If the toolbar is visible, this command will have a Hide Toolbar caption and if selected, it will hide the toolbar. The toolbar contains buttons to add text, add lines, add rectangles, add ellipses and to align selected items. On 3-D plots, this command toggles the visibility of the 3-D control panel. 150 Menu Commands Chapter 3 Delete Plot Window will delete the entire contents of the selected Plot Window. Use the Delete button in the Modify Plot dialog window if you wish to delete only one of several overlayed plots. Property Plot creates a new plot window with thermodynamic property data for a selected substance. Once created, additional property data or thermodynamic cycle state points can be superimposed on the plot using the Overlay Plot command. Also, the plot characteristics and axis scales can be modified in the usual manner with the Modify Axes and Modify Plot commands. Select the substance from the list at the left. The substance type (real fluid or ideal gas) is shown above the list. The general rule is that the substance is modeled as a real fluid if its name is spelled out (e.g., Oxygen) and as an ideal gas if its name is a chemical formula (e.g., O2). Air is the exception to this rule. For all substances except AIRH2O (psychrometric air-water mixtures), there are buttons to allow specification of the axes for the property plot. The AIRH2O substance provides fields in which the total pressure and temperature limits can be specified. Controls are provided to allow specification of up to six isobars, isotherms or isentropes. A line with the value shown in a box will be superimposed on the plot. Suggested values are provided. If you do not wish to display this line, click on the check box preceding the value. For some fluids, a choice of reference state is available for the values of enthalpy and entropy. See theReference directive Chapter 7 for more information. 151 Chapter 3 Menu Commands Curve Fit will find the best fit of a smooth curve through a previously plotted set of data points using unweighted least squares. (The Curve fit dialog provides a fit with a single independent variable. The Linear Regression command in the table menu allows a variable to be fitted with as many as 6 independent variables.) The dialog window shown below will appear. Choose the data to be fitted from the list of plots at the left. Note that data can be plotted from the Parametric Table, the Lookup Table, or the Arrays Table with the New Plot or Overlay Plot commands. Select the form of the curve fit by clicking the appropriate radio button. A sample of the equation form will appear in blue in the box at the bottom of the dialog window. The first four buttons correspond to commonly used equation forms for which linear least squares can be used to determine the unknown coefficients. The Enter/edit equation button allows you to enter any equation form or to edit a previously entered equation. The equation you enter may be linear or non-linear in the unknown parameters. You will be prompted to supply guess values and bounds for the unknown parameters. Click the Fit button (or press the Enter key). The fitted equation will be displayed in the box at the bottom of the dialog window. A Stats button will appear. Clicking the Stats button will display the following statistical information relating to the curve fit. 152 Menu Commands Chapter 3 Std. Error is the standard error of the curve-fitted parameter value; rms is the root mean square error of the fit; bias is the bias error of the fit. R^2 is the ratio of the sum of squares due to regression to the sum of square about the mean of the data. The Fit button will now have changed into the Plot button. Click the Plot button if you wish to have the curve fit equation overlayed on your plot. If the Plot Legend check box is selected, a legend containing the equation will be created and displayed on the plot. The curve fit equation will be copied to the clipboard if the To Clipboard checkbox is selected when either the Plot or Cancel button is selected. The Enter/Edit Equation option allows the user to enter a curve fit equation of the form YName=f(X-Name) with up to 7 unknown coefficients. X-Name and -YName are the names of the X and Y variables appearing in the edit fields just above the equation. By default, X-Name and Y-Name are set to the names appearing in the plot axis labels. However, other names may be entered. The coefficients must be entered as a0, a1, a2, ... a6. Upper case or lower case letters may be used. It is not necessary to use the coefficients in any order. The equation must begin with Y-Name= and involve X-Name and at least one coefficient. An example is shown in the figure below. Note that the equation you enter may be either linear or nonlinear in the coefficients. EES will employ a nonlinear least squares method to determine the coefficients. The parameter estimation algorithm requires that you supply a guess value for each of the parameters. The Curve Fit Guess Values window will appear after you click Fit. 153 Chapter 3 Menu Commands 154 Menu Commands Chapter 3 The Windows Menu Equations causes the Equations window to become the active window by bringing it to the front of all other windows and making it visible if it were hidden previously. Formatted Equations first checks the syntax of the equations and then brings the Formatted Equations window to the front displaying the contents of the Equations window in mathematical format. Solution, Arrays and Residuals cause the Solution, Arrays, and Residual windows, respectively, to be moved to the front of all other windows. These windows are normally viewed after the Solve, Min/Max, or Uncertainty Propagation command has been successfully completed. Any change made to the Equations window will remove these windows from the screen if the Hide Solution after Change Option in the Preferences dialog (Options tab) is selected. If EES is unable to solve the equation set and terminates with an error, the name of the Solution window will be changed to Last Iteration Values and the values of the variables at the last iteration will be displayed in the Solution window; the residuals for the last iteration will be displayed in the Residuals window. Plot Windows will bring the Plot Window to the front of all other windows. Each plot is identified by a title that appears on the tab displayed at the top of the Plot Window. This title is entered when the plot is first created. The title can be modified by right-clicking on the tab or by entering the modified title in the Modify Plot dialog. The tab position 155 Chapter 3 Menu Commands can be modified by right-clicking on the tab. There is no limit (other than memory limitations) to the number of plot windows that can be created and an unlimited number of overlayed plots may be drawn in each plot window using the Overlay Plot command. The menu item will be grayed if no plots have been created. The graphics in any of the plot windows can be copied to the Clipboard by selecting Copy from the Edit menu. Parametric Table and Lookup Table bring the Parametric and Lookup Table windows, respectively, to the front of all other windows and make it the active window. There may be one or more tables in each of these windows. Click on the tab at the top of the window to access the desired table. The Parametric and Lookup Table windows may be hidden by choosing close from the Windows control menu or by pressing Ctrl-F4. Diagram Window will bring the Diagram Window or a child Diagram Window to the front of all other windows. If one or more child Diagram Windows have been created, the Diagram Window menu option will display a ‘fly-out’ menu listing all of the Diagram and child Diagram windows. A diagram can be entered into EES from a drawing program or it can be created in EES using the Diagram Window drawing tools. Report Window provides access to the Report Window which operates like a word processor but with the capability to substitute the current values of EES variables. Macro Window provides access to the Macro window. Debug Window will generally be disabled. This window is available only after the Solve command is attempted with the number of equations not equal to the number of variables. In this case, an option is presented to display the Debug Window and this menu item becomes enabled. Any change made to the Equations window will clear the Debug window and disable this menu item. Warning will bring up a window showing warning messages that were issued during the preceding calculation. Warning will appear only if the Display Warning Messages setting in the Options Tab of the Preferences dialog is selected or if the $Warnings On directive appears in the Equations window. If no warning messages exist, the menu item will be disabled. Note that the generation of warning during calculations may reduce the calculation speed. Turn warnings off in calculation-intensive problems. Tile arranges all open windows to fill the screen so that a portion of each can be viewed. Cascade arranges the currently visible windows so that the title bar of each is shown. 156 Menu Commands Calculator activates the Calculator window. Chapter 3 157 Chapter 3 Menu Commands The Help Menu Help Index will activate the Help processor which provides specific information on the use of EES. The Help processor will open to the EES Information index which lists the subjects for which help is available. Clicking on the subject opens the Help window to information for that subject. Help can also be accessed by pressing the F1 key which will bring up help information specific to the window or dialog which is foremost. The online help provides most of the information contained in this manual. Help for External Libraries provides access to .HLP or .HTM files created by a user to document external routines written in EES itself or in a compiled language such as C++, Pascal, or FORTRAN. External functions and procedures that are placed in the \USERLIB folder are automatically loaded at startup. External routines can have a separate help file having an .HLP or .HTM filename extension. Because these routines are not truly part of EES, the help files cannot be included within the EES help file. However, access to the help file for any external routine is provided in the Function Information dialog by selecting the desired function and clicking the Function Info button or directly with the Help for External Libraries command. Using Help shows information provided by the Windows Help processor on how to use the features in the Help program. EES Manual (Acrobat) will start Abode Acrobat and display the electronic version of this manual which is in file ees_manual.pdf. Note that ees_manual.pdf must be in the same folder as the EES application. About EES will bring up the EES header window. This window registration information and indicates the version of your EES program. This information will be needed in any correspondence with F-Chart Software. New Features shows a list of new features in EES ordered by version number and date. 158 Menu Commands Chapter 3 f-Chart web site will open your default browser program and set the URL to the f-Chart web site. The f-Chart web site has a “goodies’ section with free examples and support programs for EES. The program developers can be contacted by e-mail through the web site. EES Instant Update facilitates obtaining a new version of EES from the F-Chart Software server. Note that you must have an internet connection and a current subscription to Instant Update service to download a new version. This command will exit EES as this is necessary to install the new version. The Help menu may also contain a menu item to provide specific help for a problem that has been accessed with the Textbook menu, as described in the next section. 159 Chapter 3 Menu Commands The Textbook Menu The Textbook menu is a user-defined menu that is designed to allow easy access to EES files. It has been used to provide a convenient means to access EES problems associated with a textbook, and thus its name. This menu can be created either by opening a textbook index file with the Load Textbook command (File Menu) or by placing the textbook index file in the USERLIB subdirectory. A textbook index file is an ASCII file identified with the filename extension (.TXB). When EES reads a textbook index file, it creates the Textbook menu at the far right of the menu bar, as shown above. The format of the textbook index file is quite simple. The menu shown above was created with the following textbook index file. Your Menu Here 1 Textbook information line 1 Textbook information line 2 Textbook information line 3 Reserved >Your menu item 1 Descriptive problem name1 | FileName1.EES | HelpFile1.HLP | Descriptive problem name2 | FileName2.EES | HelpFile2.HLP | Descriptive problem name3 | FileName3.EES | HelpFile3.HLP | >Your menu item 2 Descriptive problem name4 | FileName4.EES | HelpFile4.HLP | Descriptive problem name5 | FileName5.EES | HelpFile5.HLP | Descriptive problem name6 | FileName6.EES | NO.HLP | NO.BMP >Your menu item 3, etc. etc | FileName1.EES | HelpFile1.HLP | NO.BMP NO.BMP NO.BMP NO.BMP NO.BMP NO.BMP The first line in the file is the menu title. This title is the name of the menu which will appear in the menu bar to the right of the Help menu. The following line is a version number used internally by EES. EES currently ignores this line but a 1 should be provided, as shown. The following three lines provide information about the textbook or problem set. This information will be displayed whenever any menu item is selected from the Textbook menu. A fourth line containing the word "reserved" is provided for possible future use. EES currently ignores the information on this line, but it must be provided. The following lines contain a menu item name (preceded by an identifying > character) and then one or more problem descriptions. The menu item name is the name that will appear in the Textbook menu list. The combination of >- will place a break line in the menu. Note that a second level of menu nesting is supported. If a 160 Menu Commands Chapter 3 menu item name is preceded with >>, this menu item will become a 'flyout' menu which is displayed when the parent menu item is chosen. Each problem description line contains four pieces of information, separated by a | character. The first item is a descriptive name for the problem, which may be up to 128 characters. The second item is the filename for the EES program file. This filename may be partially or fully qualified with directory information, e.g., C:\myBook\Chapter1\Problem1.EES. However, in most cases, directory information is not necessary and it should not be included. The third item is an optional help file which is to be associated with this file. The help file can be an ASCII text file, a Windows HLP file produced by a Help formatting program, or an HTML file readable by a browser program. By convention, the help files have a .HLP or .HTM filename extension. The help file, if provided, can be accessed from an additional menu item that is placed in the Help menu. If no help file is available, enter NO.HLP for this field. The final item is the filename for a figure associated with the problem. EES does not currently use the figure, but a figure name must be provided. Use NO.BMP as a placeholder. The textbook index file should be placed in the same location (i.e., floppy disk, subdirectory, or folder) with all of the referenced EES program and help files. When the user selects a command from the Textbook menu, a dialog window will appear showing a list of the descriptive names of the problems for that menu item. The user can then select a name from the list and the file associated with that problem will be opened. EES currently uses the Textbook menu to display examples. The Examples menu provides convenient access to a number of instructive EES programs that may be of use to a new user. You can remove this menu by moving the Examples folder out of the USERLIB folder or be deleting the Example.TXB file. 161 CHAPTER 4 __________________________________________________________________________ __________________________________________________________________________ EES has a large library of built-in mathematical functions. Many of these (e.g., Bessel, hyperbolic, error functions, etc.) are particularly useful for engineering applications. EES also provides a function to convert units and functions that help manipulate complex numbers. The major feature that distinguishes EES from other equation solving programs, however, is its extensive library of built-in functions for thermophysical properties. Thermodynamic and transport properties of steam, R22, R134a, R407C, air, ammonia, carbon dioxide, and many others are implemented in a manner such that any independent set can be used to determine the remaining unknown properties. The first two sections of this chapter provide reference information for the built–in mathematical and thermophysical functions. EES also provides a Lookup Table which allows tabular data to be entered and used in the solution of the equation set. The third section provides information on the use of the Lookup Table. Much of the information provided in this chapter can also be obtained from within the program using the Info button in Function Info dialog. Built-in Functions Mathematical Functions The mathematical functions built into EES are listed below in alphabetical order. (The functions which operate on the Lookup Table are described in the Using the Lookup Table section at the end of this chapter.) All of the functions (except pi and tableRun#) require one or more arguments which must be enclosed in parentheses and separated with commas. The argument may be a numerical value, a variable name, or an algebraic expression involving values and variables. abs(X) returns the absolute value of the argument. In complex mode, abs returns the magnitude of the complex argument. (See also Magnitude(X)); angle(X), angleDeg(X) and angleRad(X) all return the angle (also called amplitude or argument) of complex variable X. Representing X as X_r + i*X_i, this function returns arctan(X_i/X_r). Angle will return the angle in either degrees or radians depending on the Trig Function setting in the Unit System dialog. AngleDeg will always return the angle in degrees and AngleRad will always return the angle in radians. All three functions return the angle in the correct quadrant of the complex plane. Note that the Angle functions are used to extract the angle of a complex number variable or expression but they cannot be used for assigning the angle of a complex number. For example, the equation Angle(X)=4 will produce an error. 162 Built-in Functions Chapter 4 arcCos(X) returns the angle which has a cosine equal to the value of the argument. The units of the angle (degrees or radians) will depend on the unit choice made for trigonometric functions with the Unit System command. arcCosh(X) returns the value which has a hyperbolic cosine equal to the value of the argument. arcSin(X) returns the angle which has a sine equal to the value of the argument. The units of the angle (degrees or radians) will depend on the unit choice made for trigonometric functions with the Unit System command. arcSinh(X) returns the value which has a hyperbolic sine equal to the value of the argument. arcTan(X) returns the angle which has a tangent equal to the value of the argument. The units of the angle (degrees or radians) will depend on the unit choice made for trigonometric functions with the Unit System command. arcTanh(X) returns the value which has a hyperbolic tangent equal to the value of the argument. average(Arg1, Arg2, Arg3, ... ) will return the average value of the arguments. The number of arguments must be between 1 and 1000. An array or subset of an array can be provided as an argument list by using array range notation, e.g., X[1..50]. avgLookup ('TableName', 'ColumnName', RowStart, RowStop) returns the average of all or selected cells in a specified column of a specified Lookup table or Lookup file on disk. RowStart and RowStop are optional. If they are not provided, all rows in the Lookup table will be averaged. 'TableName' is a string constant or string variable that contains the name of the Lookup table. The name of the Lookup table is shown on its tab at the top of the table. 'ColumnName' is a integer value, string constant or string variable the identifies the column. If an integer value is provided, it is taken to be the column number in the Lookup table. If a string constant is provided, it is assumed to be the name of the variable for the column in the Lookup table. The single quotes that normally identify a string constant are not required. If a string variable is provided, it must contain the name of one of the columns in the Lookup table. avgParametric('TableName', 'ColumnName', RowStart, RowStop) provides the same column average capability as described for avgLookup, but for a Parametric table. besseli(j, x) returns the value of jth-order Modified Bessel function of the first kind for argument value x where x>0. If j=0, this function automatically calls the bessel_I0 function. 163 Chapter 4 Built-in Functions besselj(j, x) returns the value of jth-order Bessel function of the first kind for argument value x where x>0. If j=0, this function automatically calls the bessel_J0 function. besselk(j, x) returns the value of jth-order Modified Bessel function of the second kind for argument value x where x>0. If j=0, this function automatically calls the bessel_K0 function. bessely(j, x) returns the value of jth-order Bessel function of the second kind for argument value x where x>0. If j=0, this function automatically calls the bessel_Y0 function bessel_I0(X) returns the value of zeroth-order Modified Bessel function of the first kind for argument value X where -3.75≤ X <infinity. bessel_I1(X) returns the value of first-order Modified Bessel function of the first kind for argument value X where -3.75≤ X<infinity. bessel_J0(X) returns the value of zeroth-order Bessel function of the first kind for argument value X where -3≤ X <infinity. bessel_J1(X) returns the value of first-order Bessel function of the first kind for argument value X where -3≤ X <infinity. bessel_K0(X) returns the value of zeroth-order Modified Bessel function of the second kind for argument value X where 0≤ X <infinity. bessel_K1(X) returns the value of first-order Modified Bessel function of the second kind for argument value X where 0≤ X <infinity. bessel_Y0(X) returns the value of zeroth-order Bessel function of the second kind for argument value X where 0< X <infinity. bessel_Y1(X) returns the value of first-order Bessel function of the second kind for argument value X where 0< X <infinity. ceil(x) returns the lowest integer greater than or equal to X. cis(X) is a complex mode function that returns cos(X)+i*sin(X). The required units (degrees or radians) of the angle is controlled by the unit choice made for trigonometric functions with the Unit System command. However, you can append deg or rad to the angle to override the Unit System setting. For example, V=3*cis(20deg) will set the value of complex variable V to have a magnitude of 3 and an angle of 20 degrees, regardless of the Unit System setting. 164 Built-in Functions Chapter 4 conj(X) returns the complex conjugate of a complex variable X. Representing X as X_r + i*X_i, this function returns X_r - i*X_i. Note the this function returns a complex result. The EES equation, Y=conj(X), will set the real part of Y (Y_r) to the real part of X and the imaginary part of Y to negative of the imaginary part (Y_i). convert('From', 'To') returns the conversion factor needed to convert units from the unit designation specified in the ‘From’ string to that specified in the ‘To’ string. The single quote marks are optional. For example, FI = convert(ft^2, in^2) will set FI to a value of 144 because 1 square foot is 144 square inches. Combinations of units and multiple unit terms may be entered. In a combination of units, such as Btu/hr-ft^2-R, the individual units are separated with dash (i.e., minus), a star, a dot (character Alt-250) or division symbols. Only one division symbol may be used in any one term. All units to the right of the division symbol are assumed to be in the denominator (i.e., raised to a negative power.) The ^ symbol is optional so ft2 and ft^2 are equivalent. The convert function will accept multiple unit terms if each term is enclosed within parentheses. Terms are separated with an optional * symbol or with a / symbol, as in the example below. P =15* Convert((lbm/ft3)*(ft)/(s^2/ft), kPa) The defined unit symbols can be displayed with the Unit Conversion Info command in the Options menu. If you find that a unit you need is not defined, you can enter it by editing the UNITS.TXT file in the EES directory. ConvertTemp('C', 'F', T) converts temperatures from one scale to another. Four scales are supported: Celsius (C), Kelvin (K), Farenheit (F), and Rankine (R). The first two parameters are string constants or string variables which must be C, K, F, or R. Both upper and lower case letters are permitted. The single quotes surrounding the string constants are not required. The third parameter is a temperature in the scale indicated by the first parameter. The function returns the temperature in the scale indicated by the second parameter. Example: TF=convertTemp('C', 'F', 100) sets TF to 212. cos(X) will return the cosine of the angle provided as the argument. The required units (degrees or radians) of the angle is controlled by the unit choice made for trigonometric functions with the Unit System command. cosh(X) will return the hyperbolic cosine of the value provided as the argument. diagramheight#('Name') and diagramwidth#('Name') return the height and width in pixels of the Diagram window or child diagram window that has the specified name. The main diagram window is called 'Main'. If the specified name can not be found, this function returns the height of the main diagram window. The height of the Diagram window can be 165 Chapter 4 Built-in Functions converted into inches using the PixelsPerInch# function. Knowing the height of the Diagram window is useful when moving object such as during animation. differentiate('Filename', 'ColName1', 'ColName2', ColName2=Value) returns the derivative determined from two columns of tabular data based on cubic interpolation. See the Using Lookup files and the Lookup Table section of this chapter for more information and examples. A warning message will be generated if the command attempts to extrapolate data. Warnings will not be visible unless the Display Warning Messages control in the Options tab of the Preferences dialog is checked. differentiate1 is used exactly like the differentiate function. The only difference is that differentiate1 uses linear interpolation whereas the differentiate function uses cubic interpolation. differentiate2 is used exactly like the differentiate function. The only difference is that differentiate1 uses quadratic interpolation whereas the differentiate function uses cubic interpolation. erf(X) returns the Gaussian Error function of X. erfc(X) returns the complement of the Gaussian Error function of X which is 1-erf(X). exp(X) will return the value e raised to the power of the argument X. floor(X) will return a value equal to the largest integer value that is less than or equal to the value of X. Note that FLOOR differs from TRUNC in that FLOOR when X is less than zero. For example TRUNC(-2.5) = -2 whereas FLOOR(-2.5) = -3. gamma_(X) returns the Γ (GAMMA) function for the argument value X. The Gamma ∞ function is defined as: Γ(x) = t x −1e − t dt . The Gamma function is approximated as a series expansion as described by 0 Abramowitz and Stegun, "Handbook of Mathematical Functions", Dover Publications, 10th printing, 1972. if (A, B, X, Y, Z) allows conditional assignment statements in the Equations window. If A<B; the function will return a value equal to the value supplied for X; if A=B, the function will return the value of Y; if A>B, the function will return the value of Z. In some problems, use of the if function may cause numerical oscillation. It is preferable to use the if then else, repeat until and goto statements in a function or procedure for conditional assignments. See Chapter 5 for additional information. 166 Built-in Functions Chapter 4 imag(X) returns the imaginary part of a complex variable X. Representing X as X_r + i*X_i, this function returns X_i. The Imag function cannot be used for assigning the imaginary part of a complex number. For example, the equation Imag(X)=4 will produce an error. Instead you should just enter X=4*i which will set X to 0 + 4*i. If you wish to only set the imaginary part of X, you can enter X_i=4.0 integral(Integrand, VarName) or integral(Integrand, VarName, Start, Stop, Step) returns the integral of the expression represented by Integrand with respect to the variable VarName, i.e., (Integrand) d(VarName). There are two basic forms of the integral function which differ in their reliance on the Parametric table. If the values of Start, Stop, and Step are not provided, the integral function is used only in conjunction with the Parametric Table. In this case, VarName must be a legal variable name which has values defined in one of the columns of the Parametric table and Integrand can be a variable or any algebraic expression involving VarName and other variables or values. If Start, Stop, and (optionally) Step are provided, EES will numerically integrate all equations involving variable VarName, setting the value of VarName to values between Start and Stop as appropriate. If Step is not provided, EES will internally choose a step size using an automatic stepsize adjustment algorithm. The integral function can be used to solve initial value differential equations. See Chapter 7 for additional information. integralValue(t,’X’) returns a value from the Integral Table that is created using the$IntegralTable directive. In that sense, the IntegralValue function is similar to the TableValue function which retrieves data from the Parametric Table and the Lookup and Interpolate functions which retrieve data from the Lookup Table window or Lookup files. t is the value of the independent integration variable for which the value of X is to be returned. X is the name of a variable that has been included in the Integral Table. (The single quotes around the variable name are optional.) The value provided for t must be less than or equal to the current value of the independent integration variable. Values of X corresponding to values of t that are not included in the integration range may not be properly defined. interpolate('Filename', 'ColName1', 'ColName2', ColName2=Value) returns an interpolated or extrapolated value from tabular data in the Lookup table, a Lookup file (if filename is provided), or the Parametric table using cubic interpolation. See the Using Lookup files and the Lookup Table section of this chapter for more information and examples. interpolate1('Filename', 'ColName1', 'ColName2', ColName2=Value) provides the same function as the interpolate command except that it uses linear interpolation. 167 Chapter 4 Built-in Functions interpolate2('Filename', 'ColName1', 'ColName2', ColName2=Value) provides the same function as the interpolate command except that it uses quadratic interpolation. interpolate2D('Filename', 'X', 'Y', ‘Z’, X=value1, Y=value2, N) returns an interpolated or extrapolated value as a function of two independent variables from tabular data. A minimum of 8 data points are required. These data can be in a Lookup table in the Lookup Table Window or a Lookup file (stored on disk). This function extends the capability of the Interpolate function which returns a value as a function of one independent variable. 'Table Name' is a string constant or string variable that provides the name of the Lookup table in the Lookup Window or the name of an existing Lookup file stored on disk. The string constant must be enclosed within single quote marks. Lookup table names appear on the tabs at the top of the Lookup Table Window. If the name of a disk file is supplied, it must be the name of an existing Lookup file having either the binary (.LKT) or ASCII (.TXT, .CSV) Lookup file Formats. X, Y, and Z are the names of three different columns in the specified table. These arguments can be string constants or string variables. Since there is no ambiguity, the single quotes that are normally required for string constants are optional. The next two parameters identify the two independent variables and set their values. The format is ColumnName=Value where the text to the left of the equal sign must be one of the three column names specified in the second, third and fourth parameters. Note that if a string variable was provided for the column name, then the same string variable must be used for this parameter. Value1 and value2 are numerical values or expressions. The last parameter, N, is optional. It serves two purposes. First, it indicates which of two different interpolation algorithrms are used. If N < 0, then a bi-quadratic method is used in the interpolation. If N > 0 then a multi-quadric radial basis function interpolation method is used. The absolute value of N is the maximum number of data points used in the interpolation process. The two-dimensional interpolation algorithm is computationally intensive for large values of N. If no value for N is provided, N is set to 128. If the data table contains more than N points, EES will use the N points in the table that are nearest to the point for which the interpolate is requested in normalized coordinates. If the data table contains fewer than N points, N is set to the number of points in the table. If N is set to be less than 8, EES will reset it to 8 and issue a warning message. If N is not provided, a value of -16 is assumed so that the default case is a bi-quadratic method with 16 points. Values for two of the three specified columns in the data table are specified in the calling parameters. EES will return the interpolated value from the data as a function of these independent variables using interpolation or extrapolation, as required using a multiquadric radial basis function interpolation method. 168 Built-in Functions Chapter 4 (Note: use a semicolon instead of a comma as the list separator when using the European numerical format). interpolate2DM ('Table Name', X, Y) provides two-dimensional linear interpolation for data in a Lookup table or Lookup file that are arranged in a row and column matrix format. Note that the INTERPOLATE2D function also provides two-dimensonal interpolation, but for this function, the data must be arranged in three columns and a gridding method is applied to the data. The interpolate2DM function has the following format. 'Table Name' is a string constant or string variable that provides the name of the Lookup table in the Lookup Window or the name of an existing Lookup file stored on disk. The string constant must be enclosed within single quote marks. Lookup table names appear on the tabs at the top of the Lookup Table Window. If the name of a disk file is supplied, it must be the name of an existing Lookup file having either the binary (.LKT) or ASCII (.TXT, .CSV) Lookup file Formats. X is the value of the independent variable whose values appear in the first row of the table. The columns used to determine the interpolated value will be identified by this value. Y is the value of the independent variable whose values appear in the first column of the table. The rows used to determine the interpolated value will be identified by this value. lookup$function operates just like the lookup function except that it returns a string rather than a numerical value. As in the lookup function the, lookup$ function can have two or three arguments. If three arguments are provided, the first is a string that provides the name of a Lookup table stored on disk. The next argument is a numerical value or expression that provides the row in the table. This row value should be an integer. Interpolation between rows is not allowed, as it is in the lookup function. The final parameter indicates the column. The column can be indicated by a numerical value or expression which provides the column number or by the name of the column provided in a string constant or string variable. In order to accept string information, the format style of the column in the Lookup table must be set to STRING. To change the format style, click in the column header and make the change in the Format Table dialog window. lookupCol(‘Filename’, Row, Value) uses the data in the specified row of the Lookup Table or Lookup file to determine the column which corresponds to the value supplied as the second argument. Filename is optional. See the Using Lookup files and the Lookup Table section of this chapter for more information and examples. 169 Chapter 4 Built-in Functions lookupRow(‘Filename’, Col, Value) uses the data in the specified column of the Lookup Table or Lookup file to determine the row which corresponds to the value supplied as the second argument. Filename is optional. The column may be indicated in several ways. First, it may be entered as an integer value. Alternatively, it may be entered by providing the column name as a string constant or a string variable. An older format which is still accepted is to supply the column title preceded with the # symbol. The function will return the row in the Lookup Table corresponding to the value supplied as the second argument. The row value returned will not necessarily be an integer. Interpolation between rows will be provided as needed. See the Using Lookup files and the Lookup Table section of this chapter for more information and examples. Lookup$Row operates just like the LookupRowfunction except that it its final argument is a string rather than a value. The function returns the row in the table in which this string exists. As in the LookupRowfunction the, Lookup$Row function can have two or three arguments. If three arguments are provided, the first is a string that provides the name of a Lookup table stored on disk. The next argument is the column in the table. The final argument is a string constant or string variable holding the string that will be searched in the table. Note. In order to accept string information, the format style of the column in the Lookup table must be set to STRING. To change the format style, click in the column header and make the change in the Format Table dialog window. LOOP# is useful only when animation is employed. The animation control in the Diagram window allows the calculations to be restart after they are completed thereby providing a continuous display. Loop# is a counter indicating the number of times the calculations have been started. Under some circumstances, this information can be used in the Equations window. For example, it is possible to solve a dynamic steady-state problem in which the end condition is the starting condition using the animation control. In this case, the initial conditions is found by reading the value at the end of the Parametric Table, but this value does not exist until the table has completed one loop. The Loop# variable can be used in a Function to test for this condition. Loop# has no arguments and it should only be used with animation. Otherwise the function returns 0. ln(X) will return the natural logarithm of the argument. log10(X) will return the base 10 logarithm of the argument. magnitude(X) returns the magnitude (also called modulus or absolute value) of a complex variable X. In complex mode, the abs function also returns the magnitude. Representing X as X_r + i*X_i, this function returns sqrt(X_r^2+X_i^2). The magnitude function cannot be used for assigning the magnitude of a complex number. For example, the equation magnitude(X)=4 will produce an error. 170 Built-in Functions Chapter 4 max(X1, X2, X3, …) will return the value of the largest of its arguments. The number of arguments must be greater or equal to 1. maxLookup('TableName', 'ColumnName', rowStart, rowStop) returns the maximum of all or selected cells in a specified column of a specified Lookup table or Lookup file on disk. RowStart and RowStop are optional. maxParametric('TableName', 'ColumnName', rowStart, rowStop) returns the maximum of all or selected cells in a specified column of the Parametric table. RowStart and RowStop are optional. min(X1, X2, X3, …) will return the value of the smallest of its arguments. The number of arguments must be greater or equal to 1. minLookup('TableName', 'ColumnName', rowStart, rowStop) returns the minimum of all or selected cells in a specified column of a specified Lookup table or Lookup file on disk. RowStart and RowStop are optional. minParametric('TableName', 'ColumnName', rowStart, rowStop) returns the minimum of all or selected cells in a specified column of the Parametric table. RowStart and RowStop are optional. nArrayColumns(0) takes one numerical argument which should be set to 0. The argument is used to ensure that nArrayColumns is a function name and not a variable name. The function returns the number of column in the Arrays window. If the Arrays table does not exist, the function call will return 0. nArrayRows(0) takes one numerical argument which should be set to 0. The argument is used to ensure that nArrayRows is a function name and not a variable name. The function returns the number of rows in the Arrays window. If the Arrays table does not exist, the function call will return 0. nFileRows(F$) takes one argument which must be either a string constant or a string variable that contains the name of a text file stored on the disk. The function returns the number of rows in that file. If the file does not exist or it cannot be read, the function returns 0. nLookupColumns('name') returns the number of columns in a Lookup table or Lookup file. The argument to this function can be a string variable. 171 Chapter 4 Built-in Functions nLookupRows(‘name’) takes one argument which must be either a string constant or a stringvariable. The string contains the name of a Lookup table (as in appears on a tab in the Lookup TableWindow) or the name of a Lookup file stored on disk. The function returns the number of rows in the specified table. If the specified table does not exist, the function call will result in an error message. Example: n=nlookuprows('LOOKUP 1') "number of rows in the Lookup Table1" ntableruns(‘name’) takes one string argument which must be 'Parametric', 'Lookup', 'Arrays', or the name of a Lookup file stored on disk. In this last case, the name may be provided as a string constant or string variable. The function returns the number of rows in the specified table. If the specified table does not exist, the function returns zero. Example: n=ntableruns('LOOKUP') “returns the number of rows in the Lookup Table. pi is a reserved variable name which has the value of 3.1415927. pixelsperinch# returns the number of pixels per inch used to display images on the screen. This function takes no argument. It is most useful in placing text and graphic objects on the Diagram window in particular locations, such as needed during animation. probability(x1, x2, mu, sigma) returns the probability (as a fraction less than 1) that a value x will lie between x1 and x2 in a normal distribution having average mu and standard deviation sigma. The mathematical description is z2 −z2 1 probability( x1 , x2 , μ , σ ) = exp dz 2π 2 z1 where z1 = x1 − μ σ and z2 = x2 − μ σ product(Arg, Series_info) returns the product of a series of terms. Arg can be any algebraic expression. Series_info provides the name of the product index variable and the lower and upper limits which must be integers or variables which have been previously set to integer values. product (j, j=1,4) will return 1*2*3*4 or 24, which is 4 factorial. The product function is most useful when used with array variables, e.g., X[j]. For example, the product of the square of all 10 elements in the vector X can be obtained as product (X[j]*X[j], j=1,10). real(X) returns the real part of a complex variable X. Representing X as X_r + i*X_i, this function returns X_r. The real cannot be used for assigning the real part of a complex number. For example, the equation real(X)=4 will produce an error. Instead you should just enter X=4 which will set X to 4 + i*0. If you wish to only set the real part of variable X, you can enter X_r=4. 172 Built-in Functions Chapter 4 random(A,B) returns a uniformly distributed number in the range between A and B. This function can be used only within EES Functions and Procedures rgb(red,green,blue) returns the value of color formed by providing the red, green, and blue color component values. The component values can range from 0 to 255. The RGB function is used to specify the color of objects or text items in the Diagram window that have been associated with EES variables. For example, if an object has been created in the Diagram window and given the name Ball, then Ball.fillColor=RGB(0,255,0) will set its color to be green. round(X) will return a value equal to the nearest integer value of the argument. shortfilename$(aStringVar$) accepts one argument which can be a string constant or string variable that is expected to be a Windows style filename including the path and filename name extension. The function returns a string that is set to the filename with the path information removed. sign(X) will return the sign (+1 or -1) of the argument. sin(X) will return the sine of the angle provided as the argument. The required units (degrees or radians) of the angle is controlled by the unit choice made for trigonometric functions with the Unit System command. sinh(X) will return the hyperbolic sine of the value provided as the argument. sqrt(X) will return the square root of the value provided as the argument which must be greater than or equal to zero. stddevlookup('TableName', 'ColumnName', RowStart, RowStop) returns the standard deviation of all or selected cells in a specified column of a specified Lookup table or Lookup disk file. 'TableName' is a string constant or string variable that contains the name of the Lookup table. The name of the Lookup table is shown on its tab at the top of the table. 'ColumnName' is a integer value, string constant or string variable the identifies the column. If an integer value is provided, it is taken to be the column number in the Lookup table. If a string constant is provided, it is assumed to be the name of the variable for the column in the Lookup table. The single quotes that normally identify a string constant are not required. If a string variable is provided, it must contain the name of one of the columns in the Lookup table. RowStart and RowStop are integers or EES variables specifying the starting and stopping rows for which the average will be performed. If these two parameters are not provided, the standard deviation will be determined using all of the data in the selected column. 173 Chapter 4 Built-in Functions stddevparametric ('TableName', 'ColumnName', RowStart, RowStop) returns the standard deviation of all or selected cells in a specified column of the Parametric table. 'TableName' is a string constant or string variable that contains the name of the Parametric table. The name of the Parametric table is shown on its tab at the top of the table. ''ColumnName' is a integer value, string constant or string variable the identifies the column. If an integer value is provided, it is taken to be the column number in the Parametric table. If a string constant is provided, it is assumed to be the name of the variable for the column in the Parametric table. The single quotes that normally identify a string constant are not required. If a string variable is provided, it must contain the name of one of the variables in the Parametric table. RowStart and RowStop are integers or EES variables specifying the starting and stopping rows for which the sum will be performed. If these two parameters are not provided, the standard deviation will be determined using all of the data in the selected column. step(X) will return a value of 1 if the argument is greater than or equal to zero; otherwise the Step function will return zero. The step function can be used to provide conditional assignments, similar to the if function. The step and if functions are provided to maintain compatibility with earlier versions. Conditional assignments are more easily and clearly implemented with the IF THEN ELSE statement in functions or procedures as described in Chapter 5. There are two forms for the sum function. EES determines which format is in use by context. sum(Arg, Series_info) returns the sum of a series of terms, i.e., ΣArg. Arg can be any algebraic expression. Series_info provides the name of the summation index variable and the lower and upper limits. These limits must be integers or variables which have been previously set to integer values. The function is best explained by examples. sum(j, j=1,4) will return 1+2+3+4 or 10. The sum function is most useful when used with array variables, e.g., X[j]. For example, the scalar product of two vectors, X and Y, each with 10 elements can be obtained as sum(X[j]*Y[j], j=1,10). See Chapter 7 for information on how the sum function can be used with array variables to manipulate matrices. sum(Arg1, Arg2, ...ArgN) returns the sum of the arguments. Array range notation is particularly convenient for the list form. For example, SUM(X[1..100]) returns the sum of the 100 elements in the X array. sumLookup ('TableName', 'ColumnName', RowStart, RowStop) returns the sum of all or selected cells in a specified column of the Lookup table. RowStart and RowStop are optional. If they are not provided, all rows in the Lookup table will be summed. 'TableName' is a string constant or string variable that contains the name of the Lookup table. The name of the Lookup table is shown on its tab at the top of the table. 174 Built-in Functions Chapter 4 'ColumnName' is a integer value, string constant or string variable the identifies the column. If an integer value is provided, it is taken to be the column number in the Lookup table. If a string constant is provided, it is assumed to be the name of the variable for the column in the Lookup table. The single quotes that normally identify a string constant are not required. If a string variable is provided, it must contain the name of one of the columns in the Lookup table. sumParametric ('TableName', 'ColumnName', RowStart, RowStop) provides the same capability as described above for sumLookup, but for the Parametric table. tableName$ returns the name of Parametric Table that is currently being used in the calculations. Parametric table names are seen on the tabs at the top of the Parametric Table Window. The name of a Parametric Table can be changed by right-clicking on the tab. This function has no arguments and it should only be used only when calculations are initiated with the Solve Table or Min/Max Table command in the Calculate menu. tableRun# returns the Parametric Table run number, i.e., the current row in the Parametric Table or zero, if the Parametric Table is not being used in the calculations. This function should only be used with the Solve Table or Min/Max Table command in the Calculate menu. tableValue(Row, Column) or tableValue(Row, ‘VariableName’) returns the value stored in a specified row and column of the Parametric Table. The column number may be either entered directly as an integer number or indirectly by supplying the variable name for the desired column, enclosed by the single quotes, e.g., TableValue(6,’ABC’)7. An error message will be generated if the row or column (or corresponding variable name) does not exist in the Parametric Table or if the referenced cell does not have a value. The tableValue function is useful in the solution of some 'marching-solution' type problems in which the current value of a variable depends on its value in previous calculations. tan(X) will return the tangent of the angle provided as the argument. The required units (degrees or radians) of the angle is controlled by the unit choice made for trigonometric functions with the Unit System command. tanh(X) will return the hyperbolic tangent of the value provided as the argument. trunc(X) will return a value equal to the integer value corresponding to the argument rounded toward zero. 7 For compatibility with earlier versions, EES will also accept the #symbol preceding the variable name in place of enclosing it within single quotes, e.g., TableValue(6, #ABC). 175 Chapter 4 Built-in Functions Uncertaintyof(X) returns the assigned or calculated uncertainty of the variable name that is provided as the argument to the function. The returned value will be zero if uncertainty information has not been specified for the specified variable or if the calculations are not initiated with the Uncertainty Propagation or Uncertainty Propagation Table commands. UnitsOF$returns a string that is the units of the EES variable that is provided as a parameter to the function. One use of this function is to provide help to users (e.g., in the Diagram Window) to inform them of the units of a variable for which they are expect to provide a value. UnitSystem(‘Unittype’) is a function which allows an EES program to know what unit settings have been selected with the Unit System command. This function takes one argument which must be placed within single quote marks. Legal arguments are 'SI', 'Eng', 'Mass', 'Molar', 'Deg', 'Rad', 'kPa', 'bar', 'psia', 'atm', 'C', 'K', 'F', and 'R'. The function returns either 1 (for true) or 0 (for false). As an example, the following assignment statement in an EES function or procedure. g:=unitsystem('SI') + 32.2*unitsystem('Eng') will set g equal to 1 if the user has selected the SI unit system and g equal to 32.2 if the user has selected the English unit system. 176 Built-in Functions Chapter 4 CurveFit1D Procedure CURVEFIT1D is a built-in procedure that provides the parameters and statistics resulting from a linear regression curve fit to data provided in array variables. This procedure provides the same capability as the Curve Fit menu item but it may be more convenient in that the data do not first have to be plotted and the curve fit parameters are returned so that they can be used in following equations. The CURVEFIT1D procedure has the following format: Call CURVEFIT1D(FitType, X[1..n], Y[1..n]: a[1..m], RMS, Bias, R|2, a_stderr[1..m]) FitType is a string constant or string variable that can be any of the following: 'LINEAR' {fit Y[i]=a[0]+a[1]*X[i]} 'POLYNOMIAL1' or 'POLY1' {same as linear} 'POLYNOMIAL2' or 'POLY2' {fit Y[i]=a[0]+a[1]*X[i]+a[2]*X[i]^2} 'POLYNOMIAL3' or 'POLY3' {fit Y[i]=a[0]+a[1]*X[i]+a[2]*X[i]^2+a[3]*X[i]^3} 4 6 'POLYNOMIAL4' or 'POLY4' {fit Y[i] = a[j]* X[i] j Y[i] = a[j]* X[i] j 5 j=0 j=0 'POLYNOMIAL5' or 'POLY5' {fit Y[i] = a[j]* X[i] j 6 j=0 'POLYNOMIAL6' or 'POLY6' {fit Y[i] = a[j]* X[i] j j=0 'EXPONENTIAL' or 'EXP' {fit Y[i]=a[0]*exp(a[1]*X[i])} 'POWER' {fit Y[i]=a[0]*X[i]^a[1]} 'LOGARITHMIC' or 'LOG' {fit Y[i]=a[0]+a[1]*ln(X[i])} X[1..n] is an array of values for the independent variable and Y[1..n] is an array of values for the dependent variables. n can be a numerical constant or a previously defined EES variable. The number of data points in the X and Y arrays must be greater than the number of parameters that are being determined and less than 1,000. a[1..m] is the array of curve fit parameters returned by the CURVEFIT1D procedures. Note that m is equal to 2 for all cases except for the POLYNOMIAL fit types. For those type, m is equal to one greater than the polynomial order. It is not necessary to use array range notation for the curve fit parameters. For example, a[1..2] can be replaced with a0, a1. All following outputs are optional. RMS is root mean square error defined as: sqrt(1/n*sum[(Y-Y)^2] where n is the number of data points, and Y is the estimated value of Y. BIAS is the bias error define as: 1/n*sum[(Y-Y`)]. R|2 is the correlation coefficient between Y and X a_stderr[1..m] is the standard error of the curve fit parameters defined as the square root of the estimated variance of the parameter 177 Chapter 4 Built-in Functions String Functions EES supports both numerical and string variables. String variable are identified by a$ as the last character in the variable name, e.g., Fluid$. String constants are enclosed in single quote marks. The following functions operate on string constants and variables. Chr$ requires one parameter (x) which must be between 0 and 255. The function returns a string consisting of one character having an ASCII code as given by x. This function is useful for providing characters that cannot be entered on the keyboard or would not be accepted by EES. Some common uses are: CHR$(13) {returns carriage return} CHR$(39) {returns a single quote} CHR$(123) {returns { } Concat$ accepts two arguments both of which must be either a string constant or a string variable. The function returns a single string that concatenates the two strings. Example: R$=CONCAT$('R','22') {R$will be set to 'R22'} Copy$ creates a string that is a substring of the string expression provided as the first argument. The second argument indicates the character position at which the substring starts, and the third parameter is the substring length. If this length exceeds the length of the string expression, it is set to the length of the string expression. Example: Neat$=COPY$('This is neat', 9, 255) {sets Neat$to 'neat'} Date$ returns the current date. The function has no arguments. The format of the date is controlled by the settings in the Regional Options Control Panel of your Windows Operating System. Example: T$=concat$('Today is ',DATE$) EESFILEDIR$ and EESPROGRAMDIR$return the directory of the current EES file and the EES application, respectively. The string returned from these functions can be used with the Concat$ function to create a string variable with a completely specified path. LOOKUPCOLNAME$('TableName',ColNo) returns or sets the name of a specified column in a Lookup table. 'TableName' is the name of a Lookup table or a Lookup file. It may be a string constant or string variable. ColumnNo can be a number or expression that evaluates to the column number in the table. If the column is not found, the function will return '??'. The name of an existing column in a Lookup table can only be changed within an internal Function or Procedure. To change the column name, place the LOOKUPCOLNAME$ function call on the left hand side of an equation. Note that the both the column name and the units can be set. The units are assumed to be to the right of the \ character. 178 Built-in Functions Chapter 4 LowerCase$accepts one string variable or string constant argument. It returns a string in which all letters in the string are converted to lowercase. It is not necessary to change the case of fluid names or file names as the functions that use this information are case insensitive. Example: E$=LowerCase$('EESy') {sets E$ to ‘eesy’} String$accepts one argument which can be a numerical constant, variable, or expression. The function returns a string representing the numerical value of the argument. The function uses Auto format to set the format of the value before converting it to a string. The StringVal function provides the inverse operation, converting a string to numerical value. Example: R$=CONCAT$('R',String$(10+12)) {sets R$to 'R22'} StringLen returns the number of characters in the string constant or string variable provided as the argument. This function can be applied with a string variable dropdown list on the Diagram window when it is desired to allow the user to select from a pre-determined set of numerical values. Example: R$='12345'; V=StringLen(R$) “V is set to value 5” StringPos accepts two arguments both of which must be either be a string constant or string variable. The function returns the position of the first string within the second. If the first string is not contained within the second, the function returns 0. This function is casesensitive. You may wish to use the LowerCase$ or UpperCase$functions. Example: p=StringPos(‘y’, ‘EESy does it’) {Sets p to 4} StringVal returns the numerical value formed by the characters of a string constant or string variable. This function provides the inverse operation of the String$ function. This function can be applied with a string variable dropdown list on the Diagram window when it is desired to allow the user to select from a pre-determined set of numerical values. Example: R$='22'; V=StringVal(R$) {Sets V to 22} Time$returns the current time. The function has no arguments. The format of the string returned by this function is controlled by the settings in the Regional Options Control Panel of your Windows Operating System. Example: T$=concat$('The time is now ',TIME$) Trim$removes any leading or trailing spaces in the string provided as the argument, returning a string without these spaces. Example: G$=' abc '; H$=Trim$(G$) UnitSystem$ provides string information relating to the current settings in the Unit System dialog window. The function takes one character-string argument that must be surrounded by single quote marks. Legal arguments are 'Temperature', 'Pressure', 'Mass', 'Energy, 'Entropy', 'Volume', and 'Trig', The function will return a string that represents the current 179 Chapter 4 Built-in Functions unit setting. Note that the units of energy, entropy and volume are returned for specific properties. Possible return strings for each of the arguments are as follows: Temperature: F, C, R, K Pressure: psia, atm, Pa, kPa MPa, bar Energy: Btu/lb_m, Btu/lbmol, J/kg, J/kmol, kJ/kg, kJ/kmol Entropy: Btu/lb_m-R, Btu/lbmol-R, J/kg-K, J/kmol-K, kJ/kg-K, kJ/kmol-K Volume: ft^3/lb_m, ft^3/lbmol, m^3/kg, m^3/kmol Trig: radians, degrees Example: T$=UnitSystem$('Temperature') {T$holds the temperature unit setting} Uppercase$ accepts one string variable or string constant argument. It returns a string in which all letters in the string are converted to uppercase. It is not necessary to change the case of fluid names or file names as the functions that use this information are case insensitive. Example: E$=UpperCase$('ees') {Sets E$to 'EES'} 180 Built-in Functions Chapter 4 Thermophysical Property Functions The first argument of all built-in thermophysical property functions is the name of the substance. EES provides built-in thermophysical property data for the fluids listed in the table below. All names in EES are case-insensitive. Note that, in addition to the list of fluids shown below, the property functions will recognize and operate with any of the 1262 ideal gases provided in the NASA ideal gas data base compiled by McBride et al.8 Additional fluid property data can be added as described in Appendix C. Note: Property data for liquid secondary refrigerants, such as propylene and ethylene glycol, are provided in the BrineProp2 external routine. Names of Built-In Substances in EES Real Gas * Air_ha n-Octane* R290* * Acetone* n-Pentane R404A Ammonia* Neon* R407C * * Argon Nitrogen R410A CarbonMonoxide* Parahydrogen* R423A CarbonDioxide* Propane* R500 Cyclohexane* Propylene* R502 Deuterium* R11 R507A * Ethane R12 R508B Ethanol* R13 R600* * Fluorine R14 R600a Helium* R22 R717* * Hydrogen R23* R718* HydrogenSulfide* R32* R744* Ice* R41* RC318* * Isobutane R114 R1234yf Krypton* R116* Siloxane_1* Methane* R123* Siloxane_1* Methanol* R124* SF6* * * Oxygen R125 Steam* n-Butane* R134a* Steam_IAPWS# n-Decane* R141b* Steam_NBS* * * n-Dodecane R142b SulfurHexafluoride* n-Heptane* R143a* Toluene* * * n-Hexane R152a Water* n-Nonane* R218* Xenon* * R245fa Ideal Gas Air AirH2O + Ar CH4 C2H2 C2H4 C2H5OH C2H6 C3H8 C4H10 C5H12 C6H14 C8H18 CO CO2 H2 H2O He N2 NO2 O2 SO2 8 Bonnie J. McBride, Michael J. Zehe, and Sanford Gordon, "NASA Glenn Coefficients for Calculating Thermodynamic Properties of Individual Species", NASA/TP-2002-211556, Sept. 2002 181 Chapter 4 Built-in Functions + * AirH2O provides psychrometric relations Fluid is represented with a high-accuracy equation of state. Refer to the online help for the specific reference for the equation of state. # Steam_IAPWS implements high accuracy thermodynamic properties of water substance with the 1995 Formulation for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use, issued by The International Association for the Properties of Water and Steam (IAPWS). This correlation replaced the 1984 formulation of Haar, Gallagher, and Kell (NBS/NRC Steam Tables, Hemisphere Publishing Co., 1984) which is implemented in substance Steam_NBS. The new formulation is based on the correlations of Saul and Wagner (J. Phys. Chem. Ref. Data, 16, 893, 1987) with modifications to adjust to the International Temperature Scale of 1990. The modifications are described by Wagner and Pruss (J. Phys. Chem. Ref. Data, 22, 783, 1993). This correlation provides accurate results for temperatures between 273.15 K and 1273.15 K at pressures up to 1000 MPa. The formulation allows extrapolation of properties to 5000 K. Steam_IAPWS is available only in the Professional version. Additional substances may be provided in external files in the USERLIB subdirectory with a user-supplied property file having a .MHE filename extension, as described in Appendix C. Also provided in the USERLIB subdirectory are external library routines providing thermodynamic property data for lithium bromide-water mixtures (LiBrH2O.LIB), lithium chloride-water mixtures (LiClH2O.lib), ammonia-water mixtures (NH3H2O), brine property data (BRINEPROP2.LIB), the Peng-Robinson equation of state (Peng_Robineson.DLL) and others. Also, the specific heat, enthalpy and entropy for hundreds of additional substances with NASA function reference compiled by McBride et al. Documentation for these routines is provided through the Function Info command in the Options menu. Click the EES Library routines button for the lithium bromide-water and lithium chloride-water properties. Click the External routines button for the NH3H2O and Peng_Robinson libraries.. Clicking the Function Info button will provide the documentation. It may appear from the above list that some substances, e.g., N2 and Nitrogen, CO2, R134a, and R134a_ha, H2O, Steam, Water and Steam_NBS, are duplicated, but this is not quite true. Whenever a chemical symbol notation (e.g., N2, CO2, CH4 etc.) is used, the substance is modeled as an ideal gas and the enthalpy and entropy values are based on JANAF table references. The JANAF table reference for enthalpy is based on the elements having an enthalpy value of 0 at 298K (537R). The entropy of these substances is based on the Third Law of Thermodynamics. Whenever the substance name is spelled out (e.g., Steam (or Water), Nitrogen, R12, CarbonDioxide, Methane, etc.) the substance is modeled as a real fluid with subcooled, saturated, and superheated phases. Exceptions to this rule occur for Air and AirH2O, both of which are modeled as ideal gases. AirH2O is the notation for air-water vapor mixtures, i.e., psychrometrics. 182 Built-in Functions Chapter 4 The property keywords Steam, Water, R718, and Steam_NBS are treated identically. All three keywords use property correlations for water substance published by Harr, Gallagher, and Kell (Hemisphere, 1984). These property correlations are accurate over a large range of conditions. In addition, property keyword Ice provides the same properties as Steam, Steam_NBS, Water and R718 except that it will return the state corresponding to a lower temperature when two solutions are possible, as in the following example. T_ice=temperature(Ice,v=1.088e-3,x=0) T_steam=temperature(Steam,v=1.088e-3,x=0) {T_ice=-16.85 [C]} {T_steam=147.8 [C]} The Steam_IAPWS keyword provides the 1995 Formulation for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use which supercedes the formulations provided in Steam_NBS. Information concerning the source of the property data and the range of applicability is provided when the Fluid Info button in the Function Info dialog. Many of the thermodynamic functions can take alternate sets of arguments. For example, the enthalpy function for steam can be accessed with temperature and pressure as arguments; alternatively, the same function could be accessed with entropy and quality as arguments. In general, any independent set of arguments can be supplied for thermodynamic functions. All arguments in thermophysical property functions, aside from the substance name, are identified by a single case-insensitive letter followed by an equal sign. The value or algebraic expression representing the value of the argument follows the equal sign. The letters which are recognized in function arguments and their meaning are as follows: Property I ndicators for Use in Thermophysical Functions B =W etbulb Temperature D = Dewpoint Temperature H =S pecific Enthalpy P = Pressure R = Relative Humidity S = Specific Entropy T = Temperature U = Specific Internal Energy V =S pecific Volume W = Humidity Ratio X = Quality Arguments must be separated with commas and may be in any order, provided that the substance name is first, as in the examples shown below. EES will display the function name in the format selected for Functions in the Display Options dialog window. The substance name is an EES keyword and it will be displayed in the format selected for Keywords in the Display Options dialog window 183 Chapter 4 Built-in Functions EES does not require the argument to a function to have a known value. For example: h1 = enthalpy(STEAM, T=T1, P=P1) will return the value of h1 corresponding to known temperature and pressure, T1 and P1. If, however, the value of h1 is known, but T1 is unknown, the same equation will return the appropriate value of the temperature. Alternatively, the temperature could be found by: T1 = temperature(STEAM, h = h1, P=P1) The latter method is preferable in that the iterative calculations implemented for thermodynamic properties are less likely to have convergence difficulty. The built-in thermophysical property functions are listed below in alphabetical order. The units, which depend on the choices made with the Unit System command in the Options menu, are shown in brackets. One or more examples, showing the allowable formats for the function, are also given. AcentricFactor [dimensionless] returns the acentric factor, a thermodynamic property of a fluid that is defined by ω = -1.0 - log10(Psat/Pcrit) where Psat is the vapor pressure of the fluid at a temperature equal to 0.7 * Tcrit Pcrit is the critical pressure Tcrit is the critical temperature [R or K] Conductivity [W/m-K, Btu/hr-ft-R] returns the thermal conductivity of the specified substance. For ideal gas substances, the Conductivity function takes one parameter in addition to the fluid name and this parameter must be temperature. For AirH2O (moist air), the temperature, pressure, and humidity ratio (or relative humidity) must be supplied as arguments. For real fluids, any two independent properties can be supplied, provided that the state does not consist of two phases. Examples: k1 = conductivity (AIR, T=200) k2 = conductivity (AMMONIA, T=100, P=200) k3 = conductivity (STEAM_NBS, T=100, x=1) k4 = conductivity (AIRH2O, T=80, P=14.7,R=0.5) CP and CV [kJ/kg-K, kJ/kgmole-K, Btu/lb-R, Btu/lbmole-R] return the constant pressure and constant volume specific heats of the specified substance, respectively. For pure substances which obey the ideal gas law, the specific heat function has temperature as its only other argument in addition to the substance name. Two independent properties, e.g., temperature 184 Built-in Functions Chapter 4 and pressure, must both be provided as arguments for substances modeled as real fluids. Note that, at saturation, pressure and temperature are not independent. If the constant volume specific heat of saturated liquid or vapor is required, it is necessary to provide the quality or some other quality-dependent property. The specific heat of a two-phase mixture with a quality other than 0 or 1 is infinite and a value cannot be returned for this state. For AirH2O, three arguments are required for the CP function. One of these arguments must be total pressure (P). The remaining two can be any of the following: temperature (T), enthalpy (H), relative humidity (R), humidity ratio (W), wetbulb (B), or dewpoint (D). X (for quality) is not allowed. Note also that the specific heat returned for substance AirH2O (psychrometrics) is per unit mass of dry air. Example: Cp1 = CP(AIR, T=350) Cv2 = CV (AMMONIA, T=100, P=30) CP3 = CP(AIRH2O,T=25,P=101.3,R=0.50) Density [kg/m3, kgmole/m3, lb/ft3, lbmole/ft3] returns the density of a specified substance. Two arguments are required for all pure substances; three are needed for moist air. Example: d1 = Density(AIR, T=300, P=100) d2 = Density (Steam, h=850, P=400) d3 = Density (AirH2O, T=70, R=0.5, P=14.7) DewPoint [°F, °C, R, K] returns the dewpoint temperature for air-water gas mixtures. This function can be used only with AIRH2O as the substance name. Three arguments follow the substance name in any order: temperature, total pressure, and relative humidity (or humidity ratio or wetbulb temperature). Example: D1 = dewpoint(AIRH2O, T=70, P=14.7, w=0.010) D2 = dewpoint(AIRH2O, T=70, P=14.7, R=0.5) D3 = dewpoint(AIRH2O, T=70, P=14.7, B=50) ek_LJ [K, R] returns the Lennard-Jones energy potential (often called epsilon) divided by Boltzmann's constant (k). The units of the returned value will be K in SI units and R in English units. Enthalpy [kJ/kg, kJ/kgmole, Btu/lb Btu/lbmole] returns the specific enthalpy of a specified substance. The exact form of the enthalpy function depends on the substance and independent variable(s) selected. Substances which obey the ideal gas law, such as air, require a single argument, (temperature or internal energy), in addition to the substance name whereas real fluid substances, e.g., STEAM and CARBONDIOXIDE, will always require two independent variables. For AIRH2O, three arguments are required. Example: h1 = enthalpy(AIR, T=300) 185 Chapter 4 Built-in Functions h2 = enthalpy(STEAM, T=900, P=300) h3 = enthalpy(AIRH2O, T=70, P=14.7, R=0.50) ENTHALPY_FUSION [kJ/kg, kJ/kmole, Btu/lbm Btu/lbmole] returns the difference between the specific enthalpy of the liquid and solid phases at the normal melting temperature, i.e., the temperature on the solid-liquid phase boundary corresponding to atmospheric pressure. If the triple-point pressure is above atmospheric pressure, as it is for carbon dioxide, the enthalpy change of fusion corresponds to the triple-point temperature rather than the normal melting point. The normal melting temperature is not provided as an EES function, but the effect of pressure on the melting temperature is small so that the temperature returned by the T_triple property function provides a good estimate of the melting temperature. Entropy [kJ/kg-K, kJ/kgmole-K, Btu/lb-R, Btu/lbmole-R] returns the specific entropy of a specified substance. For all pure substances, the entropy function always requires two arguments, in addition to the substance name. For AIRH2O, three arguments are required. Example: s1 = entropy(O2, T=400, P=100) s2 = entropy(AIRH2O, T=70, P=14.7, R=0.50) Fugacity [kPa, bar, psia, atm] returns the fugacity of the specified pure fluid for the given conditions. For an ideal gas fluid, f is identical to P. HumRat [dimensionless] returns the humidity ratio (defined as the mass of water vapor per mass of dry air) for air-water gas mixtures. This function is applicable only to the substance AIRH2O. The function requires three arguments which must include pressure and any two remaining independent variables such as temperature, relative humidity, enthalpy, or dew point. Example: w1 = humRat(AIRH2O, T=70, P=14.7, R=0.50) w2 = humRat(AIRH2O, T=70, P=14.7, h=25) IntEnergy [kJ/kg, kJ/kgmole, Btu/lb, Btu/lbmole] returns the specific internal energy of a specified substance. The exact form of the IntEnergy function depends on the substance and independent variable(s) selected. Substances which obey the ideal gas law, such as air, require a single argument (temperature or enthalpy) whereas real fluid pure substances, like steam, will always require two arguments in addition to the substance name. AIRH2O requires three additional arguments. Example: u1 = intEnergy(AIR, T=300) u2 = intEnergy(STEAM, T=1320, P=300) u3 = intEnergy(AIRH2O, T=70, P=14.7, R=0.50) IsIdealGas is a very simple function that requires only one parameter and that is the name of the fluid. The function returns either 1 (meaning true) or 0 (meaning false). If the function 186 Built-in Functions Chapter 4 returns true, the fluid is considered to behave according to the ideal gas law. The convention used in EES is that fluid names that are chemical symbols, e.g., O2, N2, and CO2, are modelled with the ideal gas law whereas fluid names that are spelled out, e.g., Oxygen, Nitrogen, and CarbonDioxide, are considered to be real fluids with subcooled, saturated and vapor phases. Air is an exception to this rule. The need for the IsIdealGas function arises because the number of arguments may differ is the fluid is represented by the ideal gas law. Enthalpy, for example, is determined by temperature alone for O2, but temperature and another property such as pressure are needed to determine the enthalpy of Oxygen. If you are trying to write a general function to return a property of a fluid that is specified in a string variable, you may not know how many parameters it requires unless you know if the fluid is represented by the ideal gas law. That is the purpose of this function. Use an IF THEN ELSE statement testing on the value of IsIdealGas to branch to the correct form of the property function you wish to determine. The IsIdealGas function will return -1 if the argument is one of the fluids in the Solid-Liquid_Props library. Specifically, the fluid must appear in the Fluids.txt file and property data for density, specific heat, viscosity and thermal conductivity must be provided. Example: B=IsIdealGas(O2) C=IsIdealGas(R$) MolarMass [kg/kmol, lb_m/lbmol] returns the molar mass (often called molecular weight) of the fluid provided as the parameter. Example: M_CO2 =MolarMass(CarbonDioxide) Phase$returns a stringwith the phase (superheated, saturated, liquid, ideal gas) of the specified fluid at the stated condition. Example: P$=PHASE$(Water, T=100 [C], P=50 [kPa]) Pressure [kPa, bar, psia, atm] returns the pressure of a specified substance. The argument list for the pressure function always requires the substance name followed by two arguments, each item separated by commas. The pressure function is not implemented for AIRH2O; however, an unknown pressure can still be determined using any of the functions which are applicable to moist air and which take pressure as an argument. Example: P1 = pressure(STEAM, h=1450, T=900) P_Crit [kPa, bar, psia, atm] returns the critical pressure of the specified fluid. The fluid may be a fluid name or a string variable. Example: Pc=P_Crit(R134a) "returns the critical pressure of R134a" 187 Chapter 4 Built-in Functions P_sat [kPa, bar, psia, atm] returns the saturation vapor pressure of a specified pure substance at the specified temperature. This function accepts only one argument, in addition to the fluid name, and that is the temperature. The T= must precede the value, variable, or expression providing the temperature. The temperature must be provided in the units specified in the Unit Information dialog. The fluid may be a fluid name or a string variable. Example: PS=P_sat(R134a, T=25 [C]) Prandtl returns the dimensionless Prandtl number for the specified fluid defined as Pr = μ cp k where μ is the viscosity, cp is the specific heat, and k is the thermal conductivity. The Prandtl number requires temperature as an input for ideal gas substances and temperature and pressure for real substances. Example: Pr_1=Prandtl(Air,T=100) Pr_2=Prandtl(Steam,T=100,P=50) Quality [dimensionless] returns the quality (vapor mass fraction) for substances modeled as real fluids such as WATER and R12. Two independent arguments are required. Temperature and pressure are not independent for saturated states. If the state of the substance is found to be subcooled, the quality is returned as –100. If it is superheated, 100 is returned. Example: x1 = quality(R12, h=50, T=80) Relhum [dimensionless] returns the relative humidity as a fractional number for air-water gas mixtures. There are three arguments to this function, in addition to the substance name, AIRH2O. The three arguments are temperature, total pressure and any two remaining independent variables such as temperature, wetbulb, enthalpy, dew point, or humidity ratio. Example: R1 = relhum(AIRH2O, T=70, P=14.7, w=0.01) R2 = relhum(AIRH2O, T=70, P=14.7, h=25) R3 = relhum(AIRH2O, T=70, P=14.7, B=55) Sigma_LJ [m, ft] returns the Lennard-Jones length potential (often called sigma). Specheat [kJ/kg-K, kJ/kgmole-K, Btu/lb-R, Btu/lbmole-R] returns the constant pressure specific heat of the specified substance. For pure substances which obey the ideal gas law, the specific heat function has temperature as its only other argument in addition to the substance name. The temperature and pressure must both be provided as arguments for substances modeled as real fluids. The specific heat of the liquid or vapor may be returned, depending on the temperature and pressure values provided. Example: Cp1 = specheat(AIR, T=350) Cp2 = specheat (AMMONIA, T=100, P=30) 188 Built-in Functions Chapter 4 SoundSpeed [m/s, ft/s] function returns the speed of sound c with units [m/s, ft/s] through the fluid. The speed of sound is defined as: c= ∂P ∂ρ s but for an ideal gas, this simplifies to: c = RT cp cv Examples: C1 = SoundSpeed(Air, T=300) C2 = SoundSpeed(R134a_ha,T=300,P=100) SurfaceTension [N/m, lbf/ft] returns the surface tension at the liquid-vapor interface of a saturated fluid. This function requires only one argument, in addition to the fluid name, and that is the temperature. Example: sigma=surfacetension(Water, T=400) Temperature [°C, K, °F, R] returns the temperature of the substance. The exact form of the function depends on the substance and argument(s) selected. Substances which are assumed to obey the ideal gas law, such as air, may require one or two arguments whereas pure real fluid substances, like STEAM, will always require two arguments. Example: T1 = temperature(AIR, h=300) T2 = temperature(AIR, s=1.75, P=100) T_Crit [°C, K, °F, R] returns the critical temperature of the specified fluid. Example: Tc=T_Crit(R134a) T_sat [°C, K, °F, R] returns the saturation temperature of a specified substance at the specified pressure. This function accepts only one argument, in addition to the fluid name, and that is the vapor pressure. The P= must precede the value, variable, or expression providing the pressure. The pressure must be provided in the units specified in the Unit Information dialog. The fluid may be a fluid name or a string variable. Example: TS=T_sat(R134a, P=100 [kPa]) 189 Chapter 4 Built-in Functions Volume [m3/kg, m3/kgmole, ft3/lb, ft3/lbmole] returns the specific volume of a specified substance. Two arguments are required for all pure substances; three are needed for moist air. Example: v1 = Volume(AIR, T=300, P=100) v2 = Volume(Steam, h=850, P=400) v3 = Volume(AirH2O, T=70, R=0.5, P=14,7) V_Crit [m3/kg, m3/kgmole, ft3/lb, ft3/lbmole] returns the critical specific volume of the specified fluid. Example: vc=V_Crit(R134a) "returns the critical volume of R134a" Wetbulb [°C, K, °F, R] returns the wetbulb temperature for air-water gas mixtures. This function is applicable only to the substance AIRH2O. There are three arguments to this function, in addition to the substance name. The three arguments are temperature (or enthalpy), total pressure, and relative humidity (or humidity ratio or dewpoint). Example: B1 = wetbulb(AIRH2O, T=70, P=14.7, w=0.01) B2 = wetbulb(AIRH2O, h=25, P=14.7, w=0.01) B3 = wetbulb (AIRH2O, h=25, P=14.7, D=30) 2, lb /ft-hr] returns the dynamic viscosity of the specified substance. For Viscosity [N-sec/m m ideal gas substances, the Viscosity function takes one parameter in addition to the fluid name and this parameter must be temperature. For AirH2O (moist air), the temperature, pressure, and humidity ratio (or relative humidity) must be supplied as arguments. For real fluids, the Viscosity function takes two parameters. Any two independent properties can be supplied, provided that the state does not consist of two phases. Example: v1 = viscosity(AIR, T=300) v2 = viscosity(R134a, T=40, x=1) v3 = viscosity(STEAM_NBS, T=100, v=0.335) v4 = viscosity(AIRH2O, T=80, P=14.7, R=0.5) 190 Built-in Functions Chapter 4 Using Lookup Files and Lookup Tables A Lookup file is a two-dimensional set of data with a specified number of rows and columns. Lookup files provide a means to enter functional relationships with tabular data and to use these relationships in the solution of the equations. Lookup files can be stored in a disk file. In addition, one or more Lookup Tables can exist in the Lookup Table Window where they can be viewed and changed. The six menu commands which pertain to the Lookup Table Window appear at the bottom of the Tables menu and are summarized here. New Lookup Table creates a new empty Lookup Table with a specified number of rows and columns in the Lookup Table Window. A name must be provided for the Lookup Table. This is the name that must be used with commands that use the Lookup Table, including the Lookup, Lookup$, LookupRow, Interpolate, and Differentiate commands. The name will appear on a tab at the top of the Lookup Table Window. The Open Lookup Table command will read the data in a Lookup file stored on disk into a Lookup Table in the Lookup Table Window. There are three Lookup File Formats, and all three can be opened with the command. In addition to being read into the Lookup Table, Lookup files can be accessed directly with Interpolate, Differentiate, Lookup, LookupCol, and LookupRow functions. Lookup Tables must have a name to be used with functions that operate on the Lookup Table data. The name that is given to the Lookup Table that is read in is the filename without the drive and filename extension. The name appears on a tab at the top of the Lookup Table Window. You can change the name by right-clicking on the tab. Binary Lookup files (.LKT) Binary Lookup files store all of the information that appears in a Lookup Table window in a binary file on disk, including the data, and the column name, units, and display format for each file type. A binary (.LKT) Lookup file is created using the Save Lookup Table command. Once created, the Lookup file can be opened into the Lookup Table window using the Open Lookup Table command. Binary files require less disk storage space and the can be opened and saved more quickly by EES. However, they cannot be created, edited or viewed by any application other than EES. ASCII Lookup files (.TXT) There are several variations for the ASCII Lookup file format. In the basic form, the first line of the file contains the number of rows and columns in the table. Each following line provides the data for one row with the value for each column separated by one or more spaces or a tab character. The basic form does not provide a means of specifying the names, units, or display format for the data. EES assigns the names "COLUMN1', 'COLUMN2', etc. and these column names should be used when the file is used with the 191 Chapter 4 Built-in Functions Interpolate or Differentiate commands. Automatic formatting is used to display the data if the file is read into the Lookup Table with the Open Lookup Table command. The following example shows the ASCII data needed for a Lookup file with five rows and three columns. 53 1 2 3 4 5 11 22 33 44 55 111 222 333 444 555 If a negative number is provided in the file for the number of rows, EES will determine the number of rows of data in the file. If the number of columns is a negative number, EES will expect to find the format specification (e.g., A3, F3 or E4) followed by one space and then the column heading and units for each column. The units are enclosed in square brackets. The following lines contain the data for each row, separated by one or more spaces or a tab. The example below would create a table with 2 rows and 3 columns. The columns would be formatted with E4, F0, and F3 format specifications and the column names will be ColA, ColB, and ColC. 2 -3 E4 ColA [Btu] F0 ColB F3 Col 1.23E-12 2 2.34E-11 4 4.56 7.89 In addition to being read into the Lookup Table, Lookup files in either the binary or ASCII formats can be accessed directly with Interpolate, Differentiate, Interpolate2D, Lookup, LookupCol, and LookupRow functions. These functions are documented below. ASCII Lookup files (.CSV) and Format Specification Files. (.FMT) The .CSV file provides only data without any information concerning the column names or data format. Values in the same row can be separated with a Tab, comma, or semincolon character. The number of values in the first non-skipped row of the file determines the number of columns in the table. The number of rows in the table is equal to the number of rows of data excluding the number of rows that skipped. Each row ends with a linefeed carriage return. The .CSV format is necessary when you wish to export the data to another application, such as a spreadsheet. Note that when EES tries to open a .CSV file and encounters character data, it will bring up the following dialog which allows options on reading the data. 192 Built-in Functions Chapter 4 One of the options is to read the data with a format specification provided in a Format file (.fmt). A Format file can be provided with the $OPENLOOKUP directive or the OPENLOOKUP macro commands to read a LOOKUP file into a LOOKUP table in a specified manner. The .fmt file provides the column display format and optionally, the name and units of the data that are to read into the LOOKUP table. An example .fmt file is: //this is a format specification for .tm2 files skip 1 2-3 F0 year 4-5 F0 Month 6-7 F0 Day 8-9 F0 Hour 10-13 A G_o W-hr/m^2 18-21 A G W-hr/m^2 24-27 A DNI W-hr/m^2 30-33 A G_D W-hr/m^2 68-71 A T_a*10 C 74-77 A T_dp*10 C 80-82 A RH % 85-88 A P_a millibar 96-98 A Wind m/s Any row that begins with // is understood to be a comment and is not further considered by EES. The first (non-comment) rows can optionally be any of the following specifications: Skip n //skip the specified number of rows (n) when reading the file ReadHeaders //consider the first non-skipped row to be the text in the header ReadUnits //consider the row after the headers to be the units that appear in the header 193 Chapter 4 Built-in Functions Separator Tab // Legal separators are: space tab, comma, or any single character such as ; FixLFCR //needed only when the text file to be opened was written on a Unix system AllowStrings //automatically set column in the Lookup table to be string format if the data file contains a non-numerical character in the first row of data The remaining rows are all of the same form. Each row has 4 fields separated by the Tab character. The first field provides the range of columns that will be read with a hyphen (-) delimiting the start and end columns. The second field provides a format specification which directs EES on how to display the data. The following specifications are valid Fn En A S display the data as fixed decimal showing n figures after the decimal point display the data as floating decimal with n significant figures display the data and let EES automatically select the display format read the data as string input The third and fourth fields are optional. If present, they provide the name in the column header and then units Save Lookup saves the foremost Lookup Table in the Lookup Table Window as a Lookup file on the disk. Lookup files can be accessed with the Lookup functions described below. The Lookup file can be saved as a binary file with a .LKT filename extension or as an ASCII text file. The ASCII format allows the data to be exported to another application. Note that the Lookup Tables in the Lookup Table Window are also saved with other problem information when the Save command is issued. It is not necessary to save a Lookup Table separately unless it is to be used with another program. Insert/Delete Lookup Rows will allow one or more rows to be added or removed from an the specified Lookup Table in the Lookup Table Window. Select the name of the Lookup Table for which the change is to be made from the drop-down list at the top of the dialog. Note that rows in a Lookup Table can be delete more simply by clicking in the row header (in the leftmost column) to select the row followed by pressing the Delete key or selecting the Delete command in the Edit menu. Insert/Delete Lookup Cols will allow one or more columns to be added or removed from an existing Lookup Table in the Lookup Table Window.. Select the name of the Lookup Table for which the change is to be made from the drop-down list at the top of the dialog. Note that columns in a Lookup Table can be deleted more simply by clicking in the column header to select the column followed by pressing the Delete key or selecting the Delete command in the Edit menu. 194 Built-in Functions Chapter 4 Delete Lookup Table will present a dialog that shows all Lookup Tables in the Lookup Table Window. Select the Lookup Tables that you wish to delete by clicking on their names in the list. Selected files will be deleted when the OK button is clicked. Data in the Lookup Table can be accessed with the Differentiate, Interpolate, Interpolate2D Lookup, Lookup$, LookupRow, Lookup$Row, and LookupCol functions. These functions may either operate on data in the Lookup Table window or in a Lookup file on disk. In the former case, the name of the Lookup Table that is accessed is provided as the first argument as a string constant (surrounded with single quotes) or string variable (identified by the$ character at the end of the variable name). In the latter case, the first argument of the function is the Lookup filename as it is stored on disk. The file name can be supplied as a string constant or as a string variable. Chapter 7 provides details on the use of string variables. The filename extension can either be .LKT (for binary lookup files) or .TXT or .CSV (for ASCII lookup files). If a filename extension is not provided, EES will assume that the file format to be binary (i.e., EES will automatically append the .LKT extension). Differentiate(TableName, 'ColName1', 'ColName2', ColName2=Value) returns the derivative determined from two columns of tabular data based on cubic interpolation. These data can be in the Lookup table, a Lookup file, or the Parametric table. TableName is a string constant or string variable that provides the name of the Lookup table in the Lookup Window or the name of an existing Lookup file stored on disk. The string constant must be enclosed within single quote marks. Lookup table names appear on the tabs at the top of the Lookup Table Window. If the name of a disk file is supplied, it must be the name of an existing Lookup file having having a .LKT, .TXT. or .CSV filename extension. If the TableName parameter is not supplied, the Differentiate function will be applied to date in the foremost Lookup Table. ColName1 and ColName2 are the column header names. The single quotes enclosing the column header names are optional. These columns names can also be supplied with string variables. The final parameter is of the form ColName2=Value where the text to the left of the equal sign can be either of the column header names (ColName1 or ColName2) specified with the two previous parameters. Value is a numerical value or expression. EES will return an estimate of the derivative d(ColName1)/d(ColName2) at a point fixed by the specified value of either ColName1 or ColName2. The Differentiate function can also be made to operate on data in the Parametric table if Filename is set to ‘Parametric’. In this case, the values in the Parametric table must already exist, such as those entered from the keyboard. Values which are to be calculated when the Solve Table command is issued cannot be used with the Differentiate command. Examples: dXdY=Differentiate(‘Lookup 1’,'X', 'Y', Y=2.34) {returns the derivative dX/dY at a value of Y=2.34 using data in Lookup Table l} 195 Chapter 4 Built-in Functions Y=Differentiate('C:myFile',T,X,T=100) {returns the derivative dT/dX at a value of T=100 using data from Lookup file myFile.LKT on drive C} Interpolate('TableName, 'ColName1', 'ColName2', ColName2=Value) returns an interpolated or extrapolated value from tabular data in the Lookup table, a Lookup file, or the Parametric table using cubic interpolation. TableName is a string constant or string variable that provides the name of the Lookup table in the Lookup Window or the name of an existing Lookup file stored on disk. The string constant must be enclosed within single quote marks. Lookup table names appear on the tabs at the top of the Lookup Table Window. If the name of a disk file is supplied, it must be the name of an existing Lookup file having with a .LKT, .TXT. or .CSV filename extension. If TableName is not supplied, the Interpolate function will be applied to date in the foremost Lookup Table. ColName1 and ColName2 are the column header names. These single quotes enclosing the column header names are optional. The column header names can alternatively be entered as string variables. The final parameter is of the form ColName2=Value where the text to the left of the equal sign can be either of the column header names (ColName1 or ColName2) specified with the two previous parameters. Value is a numerical value or expression. EES will return the interpolated value from the data in column ColName1 corresponding to the specified value of ColName2. If the value of ColName1 is supplied, EES will return the interpolated value of ColName2. If Filename is 'Parametric', the interpolate command will be applied to the existing Parametric table. In this case, the values in the Parametric table must already exist, such as those entered from the keyboard. Values which are to be calculated when the Solve Table command is issued cannot be used with the interpolate command. Examples: Z=interpolate(‘Lookup 1’, ‘Col1’, ‘Col2’, Col1=2.3) {returns a value from the Lookup Table in table Lookup 1 from column Col2 of the Lookup table corresponding to a value in Col1 equal to 2.3 using cubic interpolation. Note that the quotes are optional.} X= Interpolate(C:\myData.LKT,X,Y,Y=4.5) {returns a value from column X in the lookup table called myData.LKT on drive C: corresponding to a value in column Y equal to 4.5 using cubic interpolation.} Lookup(TableName, Row, Column) returns the value in a Lookup Table or Lookup file at the specified row and column. TableName is a string constant or string variable that provides the name of the Lookup table in the Lookup Window or the name of an existing Lookup file stored on disk. The string constant must be enclosed within single quote marks. Lookup table names appear on the tabs at the top of the Lookup Table Window. If the name of a disk file is supplied, it must be the name of an existing Lookup file having with a .LKT, .TXT. or .CSV filename extension. Note that the column (last argument) can be specified 196 Built-in Functions Chapter 4 either by providing a numerical value (or expression) for the column number or by providing the column name as a string constant (enclosed in single quotes) or as a string variable. An older format in which the column name is preceded with the # symbol is still supported. The row and column arguments need not be integers. The value returned will be interpolated between rows and columns as needed. For example, Lookup(‘Lookup 1’,2.5, 3) will return a value which is midway between the values on the second and third rows in the third column. If the specified row or column is less than 1, the value in the first row or column will be returned. Similarly, if the row or column is greater than the number of rows and columns in the lookup table, the value in the last row or column will be returned. The Lookup function can be used with the LookupCol and LookupRow functions to provide interpolated values of user-supplied tabular information. However, the Interpolate commands are usually more convenient for this purpose. Examples: X=Lookup(‘Lookup 1’,1,2) { Set X to the value in row 1, column 2 in the Lookup Table named ‘Lookup 1’} X=Lookup(‘Lookup 1’,1,’X’) { Set X to the value in row 1 of the column in the Lookup table which is named X. } X=Lookup(‘C:\abc\ CopperK.LKT’,R,’T’) {Set X to the value in row R and the column which is named T in Lookup file C:\ abc\ CopperK.LKT} Lookup$operates just like the Lookup function except that it returns a string rather than a numerical value. As in the Lookup function the first argument is the name of the table in the Lookup Table window or a name of a Lookup file stored on disk.. The next argument is a numerical value or expression that provides the row in the table. This row value should be an integer. Interpolation between rows is not allowed, as it is in the Lookup function. The final parameter indicates the column. The column can be indicated by a numerical value or expression which provides the column number or by the name of the column provided in a string constant or string variable. Note. In order to accept string information, the format style of the column in the Lookup table must be set to STRING. To change the format style, click in the column header and make the change in the Format Table dialog window. Example: R$=Lookup$(‘Lookup 1’,1,2) {Column 2 must be set to STRING format} LookupCol(‘Filename’, Row, Value) uses the data in the specified row of the Lookup Table or Lookup file to determine the column which corresponds to the value supplied as the second argument. The column value returned may not be an integer. Interpolation between columns will be provided as needed. The purpose of the LookupCol function is to provide 197 Chapter 4 Built-in Functions a means of relating tabular information in different rows of the Lookup Table or Lookup file. Examples: C=LookupCol(‘Lookup 1’,2, 100) {Set C to the column number in row 2 of table Lookup 1 which has a value of 100} C=LookupCol(‘C:\abc\ CopperK.LKT’, R, X) {Set C to the column number in row R of \Lookup file C:\abc\ CopperK.LKT having the value X} LookupRow(Tablename,Column, Value) uses the data in the specified column of the Lookup Table or Lookup file to determine the row corresponding to the value supplied as the second argument. TableName is a string constant or string variable that provides the name of the Lookup table in the Lookup Window or the name of an existing Lookup file stored on disk. The string constant must be enclosed within single quote marks. Lookup table names appear on the tabs at the top of the Lookup Table Window. If the name of a disk file is supplied, it must be the name of an existing Lookup file having with a .LKT, .TXT. or .CSV filename extension. Note that the last argument which indicates the column in the table can be indicated either by supplying its numerical value or by providing the column name as a string constant (enclosed in single quotes) or as a string variable. An older format in which the column name is preceded by the # symbol is also accepted. The row value returned may not be an integer. Interpolation between rows will be provided as needed. The purpose of the LookupRow function is to provide a means of relating tabular information in different columns of the Lookup Table. Examples: R=LookupRow(‘Lookup 1’, 2, 100) {Set R to the row number in column 2 of the Lookup table which has a value of 100} R=LookupRow(‘C:\abc\ CopperK.LKT’, C, X) {Set R to the row number in column C Lookup file C:\abc\ CopperK.LKT which has the value X} Lookup$Row operates just like the LookupRow function except that it its final argument is a string rather than a value. The function returns the row in the table in which this string exists. As in the LookupRowfunction the, Lookup$Row function can have two or three arguments. If three arguments are provided, the first is a string that provides the name of a Lookup table stored on disk. The next argument is the column in the table. The final argument is a string constant or string variable holding the string that will be searched in the table. Note. In order to accept string information, the format style of the column in the Lookup table must be set to STRING. To change the format style, click in the column header and make the change in the Format Table dialog window. 198 Built-in Functions Chapter 4 When a new Lookup Table is created, the columns are initially named Column1, Column2, etc. These default names and the table display format can be changed by clicking the right mouse button in the header cell and selecting Properties from the popup menu. See the Lookup Window section of Chapter 2. Information can be copied to or from the Lookup Table via the Clipboard. In this way, data may be transferred between the Lookup Table and the Parametric Table or between other applications such as a spreadsheet program. To select a rectangular group of cells in the Table, click the left mouse in the upper left cell. Hold the Shift key down and then click in the lower right cell. Selected cells will be displayed in inverse video. Use the Select All command in the Edit menu to select all of the cells in the Lookup table. Next, use the Copy command in the Edit menu to copy a selected range of table cells to the Clipboard. Hold the Ctrl key depressed if you wish to copy the column header name and units, in addition to the selected data. Data may be copied from the Clipboard by clicking the upper-left cell into which the data are to be pasted, followed by the Paste command. The data in the Clipboard will be pasted into the Lookup Table, starting from the selected cell. Solid/Liquid Property Library Clicking the Solid/Liquid Property button in the Function Information dialog changes the display to appear as follows. 199 Chapter 4 Built-in Functions The list on the left shows the property functions that have been currently implemented which include: alpha_ linear thermal expansion coefficient beta_ volumetric coefficient of thermal expansion c_ specific heat DELTAL\L_293_ change in length relative to the length at 293 K E_ modulus of elasticity k_ thermal conductivity mu_ viscosity nu_ Poisson's ratio Pv_ vapor pressure rho_ density Note that only some of these functions are available for most of the substances. On the right are names of substances to which these functions can be applied. The drop-down list box in the center allows a selection criterion to be applied to the list of substances. The selection criteria are: All data, metals, liquid metals, building materials, insulation, miscellaneous, and fluids. An example indicating the format of the function use appears in the examples box. Note that Temperature can be a numerical value, and EES variable, or an algebraic expression that evaluates to the desired temperature in the scale selected in the Unit System dialog. Details such as the source of the data and the applicable range of the correlation can be obtained by clicking the Function Info or Info buttons. The substance name can be supplied as a string constant (within single quotes) or string variable. (The quotes are optional) Solid/liquid property functions require only one numerical parameter and that is the temperature. The T= indicator used in fluid property functions is optional. Thus, the following function references are equivalalent. k=k_('Copper',25 [C]) k=k_(Copper,T=25[C]) S$='Copper'; T=25 [C]; k=k_(S$,T=T) The Solid/Liquid property functions are not truly built into EES but rather implemented in a user-accessible internal function library file named Solid-Liquid_Props.lib. The property data 200 Built-in Functions Chapter 4 are stored in EES Lookup files having a .LKT filename extension. The library and data files are in the UserLib/Solid-Liquid_Props folder. The library file uses the Interpolate command to determine the property data values. You can add additional property data and other functions if you wish as explained in the Solid/Liquid Properties help file that is accessed by clicking the Function Info button. Use the Open command to open the Solid-Liquid_Props.lib file to view or modify the EES code. Use the Open Lookup Table command to view or modify the data for any substance. If the Solid-Liquid_Props folder is renamed or moved out of the USERLIB folder the Solid/Liquid properties button will be disabled. The USERLIB folder is located in the working directory. 201 Chapter 5 Functions, Procedures, Modules, and Subprograms CHAPTER 5 ____________________________________________________________________________ ____________________________________________________________________________ Most high-level programming languages allow the user to write subroutines. EES also offers this capability in a variety of ways. An EES subroutine is a Function, Procedure, Module or Subprogram written within EES. A Function is a subroutine that accepts one or more inputs and returns a single result. A Procedure can return one or more results. A Module is similar to a Procedure in that it can return one or more results. However, it differs from a Procedure in that it employs equalities rather than assignment statements, as explained below. The equations in a Module are grafted into the main EES routine. A Subprogram differs from a Module in that it forms a stand-alone EES program that can be called from the main EES program or from a subroutine. EES can access both internal subroutines that have been written within EES and external subroutines written in Pascal, C, C++, FORTRAN, or any compiled language. The development of external subrouitnes is described in Chapter 6. Both internal and external subroutines can be stored in the USERLIB\ subdirectory from which they are automatically loaded when EES is started. EES subroutines offer a number of advantages. First, they make it easier to formulate the solution for a complicated system by breaking the problem up into a number of smaller parts. Programs which rely on subroutines are easier to understand. Second, subroutines can be saved in a library file and reused in other EES programs. Third, EES functions and procedures (but not modules) allow use of if then else, repeat until and goto statements. The statements appearing in functions and procedures differ from those in the main body of EES in that they are assignment statements, similar to those used in most high-level programming languages, rather than equality statements. They are executed in the order in which they appear. Modules employ equality statements just as those used in the main body of an EES program. EES reorders the equality statements as needed to efficiently solve the equations. The combination of both statement types offers a great deal of flexibility in the manner in which a problem can be formulated in EES. There are several ways to access subroutines. The Merge command in the File menu can be used to import EES subroutines from one EES file into another. In addition, EES also allows subroutines to be saved in a library file. Library files are EES files containing one or more functions, procedures, and/or modules which have been saved with a .lib filename extension using the Save As command. Subroutines stored in library files that reside in the USERLIB\ subdirectory are automatically and transparently loaded when EES starts. Library files can also be loaded with the Load Library command in the File menu and with the$INCLUDE directive. Functions, procedures and modules in library files act just like EES internal functions. They 202 Functions, Procedures, Modules, and Subprograms Functions, Procedures, Modules, and Subprograms Chapter 5 can even provide help when requested. described at the end of this chapter. The steps necessary for creating library files is EES Functions EES provides the capability for the user to write functions directly in the Equations window using the EES equation processor. EES functions are similar to those in Pascal. The rules for these functions are as follows: 1. The user functions must appear at the top of the Equations window, before any of the equations in the main body of the EES program. 2. User functions begin with the keyword FUNCTION. The function name and arguments, enclosed in parentheses and separated by commas, follow on the same line. 3. The function is terminated by the keyword END. 4. The equations appearing in EES Functions and Procedures are fundamentally different from those appearing in the main body of EES. The equations in Functions and Procedures are more properly called assignment statements, similar to those used in FORTRAN and Pascal. An assignment statement sets the variable identified on the left of the statement to the numerical value on the right. X:=X+1 is a valid assignment statement but it obviously cannot be an equality, as assumed for all equations in the main body of EES. The := sign (rather than the = sign) is used to signify assignment. However, EES will accept an equal sign in assignment statements if the Allow = in Functions/Procedures control in the Display Options dialog window (Options menu) is selected. 5. EES normally processes the assignment statements in a function or procedure in the order they appear. However, If Then Else, Repeat Until, goto and Return statements may be used in functions and procedures to alter the calculation order. The format of these logic control statements is described below. 6. Functions are called simply by using their name in an equation. The arguments must follow the name, enclosed in parentheses. The function must be called with the same number of arguments appearing in the FUNCTION statement. 7. Equations in user functions may call any of the built-in functions. In addition, they may call any user function or procedure or any functions or procedures previously loaded as Library files. Recursive functions which call themselves are, however, not allowed. A functions may not call a Modules, but it can call a Subprogram. 8. All variables used in the function body are local to the function except those variables defined in the scope of the $COMMON directive. The function returns the value to which its name is assigned. 203 Chapter 5 Functions, Procedures, Modules, and Subprograms 9. Functions always operate in real mode regardless of the setting for complex algebra. Functions can be used to implement an analytical relationship between two or more variables. For example, the specific availability of a flowing stream, often called ψ, is ψ = (h - ho) - To (s - so) + V2/2 + g z where h and s are specific enthalpy and entropy, respectively ho and so are specific enthalpy and entropy at the ‘dead’ state condition, To and Po V is the velocity g is gravitational acceleration z is elevation, relative to a selected zero point Once the temperature and pressure of the dead state are selected, ho and so are constants. A user function for the availability of steam, with To=530 R and Po=1 atm, could be implemented by placing the following statements at the top of the Equations window. A reference to psi(T1, P1, V1, Z1) from an equation would return the specific availability of steam in Btu/lbm for the chosen ‘dead’ state. FUNCTION psi(T, P, V, Z) To := 530 [R] “dead state temperature” ho := 38.05 [Btu/lbm] “specific enthalpy at dead state conditions” so := 0.0745 [Btu/lbm-R] “specific entropy at dead state conditions” h := enthalpy(STEAM, T=T, P=P) s := entropy(STEAM, T=T, P=P) g = 32.17 [ft/s^2] “gravitational acceleration” psi := (h-ho)- To * (s – so) + (V^2 / 2 + g * Z) * Convert(ft^2/s^2, Btu/lbm) “[Btu/lbm]” END Functions can also be used to change the name of any built-in function and/or to shorten the argument list. For example, the following function changes the name of humrat, the built-in function for humidity ratio, to w, eliminates the need to specify the substance AIRH2O as an argument, and sets the total pressure to 100 kPa in each case. FUNCTION w(T,RH) w := humrat(AIRH2O, T=T, P=100, R=RH) END The two example functions both employ EES internal property functions and as a result, they depend on the EES unit settings to be properly set. Using the UnitSystem function (Chapter 4) 204 Functions, Procedures, Modules, and Subprograms Chapter 5 and the IF THEN ELSE statements documented below, it is possible to write general functions that will operate correctly with any unit settings. Note that the units for variables in a Function/Procedure/Module/Subprogram can be set in the Equations window by selecting the variable and right-clicking the mouse to select the Variable Info menu item or with the Variable Information menu command (Options menu). The Variable Information dialog for Function psi would appear as shown below. The Guess value, and Lower and Upper bounds are not applicable for functions since variables in Functions and Procedures are set with assignment statements. The units of variables in Functions and Procedures can also be set in the Solutions window. 205 Chapter 5 Functions, Procedures, Modules, and Subprograms EES Procedures EES procedures are very much like EES functions, except that they allow multiple outputs. The format of a Procedure is: PROCEDURE test(A,B,C : X,Y) ... ... X :=... Y :=... END Procedures must be placed at the top of the Equations window, before any of the modules or equations in the main body of an EES program. The procedure name, TEST, in the example above, can be any valid EES variable name. The argument list consists of a list of inputs and a list of outputs separated by a colon. In the example above, A, B, and C are inputs and X and Y are outputs. Each procedure must have at least one input and one output. Each output variable must be defined by an equation with the output variables name on the left of the assignment sign. An END statement closes the procedure. To use the procedure, place a CALL statement anywhere within your equations. The CALL statement appears as ... CALL test(1,2,3 : X,Y) ... The numbers of inputs and outputs in the CALL statement argument list must exactly match the PROCEDURE declaration statement. The arguments may be constants, string variables, numerical variables, or algebraic expressions. Additional arguments can be passed between the main body of an EES program and a procedure using the$COMMON directive. EES will evaluate the outputs using the input variables supplied in the argument list. Procedures may also call other functions and procedures, provided that they are defined previously. Procedures may not call modules. The equations within a procedure differ from ordinary EES equations in modules or in the main body of an EES program. First, all variables except for the inputs and outputs are local to the procedure. Second, the equations are really assignment statements, rather than equalities, and to make this distinction clear, the assignment symbol (:=) is used in place of the equal sign. You may override this convention by enabling the Allow = in Functions/Procedures control in the Preferences dialog window (Options menu). Third, if then else, repeat until and goto statements may be used. The format of these flow control statements is described in the next section. 206 Functions, Procedures, Modules, and Subprograms Chapter 5 Implicit equations can not be directly solved in a procedure or function, as they are in modules and in the main equation body. Using the If Then Else, Repeat Until and goto statements, it is possible to program your own iterative loop. However, it is also possible to have EES solve implicit equations within a procedure. For example, consider the following two non-linear equations. X^3 + Y^2 = 66 X/Y = 1.23456 To solve for X and Y in a procedure, subtract the right-hand side from the left hand side of each equation and set them to residuals, R1 and R2, respectively. Now use EES to solve for X and Y such that the residuals are 0. Here's a program which does this. However, it should be noted that implicit equations could be solved more directly and efficiently using a module, as described later in this chapter. PROCEDURE Solve(X,Y:R1,R2) R1:=X^3+Y^2-66 R2:=X/Y-1.23456 END CALL Solve(X,Y:0,0) {X = 3.834, Y = 3.106 when executed} Procedures offer a number of advantages for the EES user. Commonly-used procedures may be saved separately and merged into the Equations window with the Merge command in the File menu. Alternatively, the procedure could be saved as a library file so that it is loaded automatically when EES is started. Procedures can be selectively loaded with the Load Library command in the Options menu or with the $INCLUDE directive. For example, the equations describing a turbine can be entered once and saved. Each time a turbine calculation is needed, the CALL Turbine statement can be used to determine the turbine work and outlet state variables. EES supports both internal and externally-compiled procedures. Internal procedures are entered directly at the top of the Equations window, as described in this section. External procedures are written in a high-level language such as C, Pascal, or FORTRAN and called from EES. The CALL statement for both types of procedures is identical. See Chapter 6 for a detailed description of writing and using external functions and procedures. 207 Chapter 5 Functions, Procedures, Modules, and Subprograms Single-Line If Then Else Statements EES functions and procedures support several types of conditional statements. These conditional statements can not be used in modules or in the main body of an EES program. The most common conditional is the If Then Else statement. Both single-line and multiple-line formats are allowed for If Then Else statements. The single-line format has the following form. If (Conditional Test ) Then Statement 1 Else Statement 2 The conditional test yields a true or false result. The format is very similar to that used in Pascal. Recognized operators are =, <, >, <=, >=, and <> (for not equal). The parenthesis around the conditional test are optional. Note that string variables (see Chapter 7) can be used in the condition test. The Then keyword and Statement 1 are required. Statement 1 can be either an assignment or a GoTo statement. The Else keyword and Statement 2 are optional. In the single-line format, the entire If Then Else statement must be placed on one line with 255 or fewer characters. The following example function uses If Then Else statements to return the minimum of its three arguments.9 Function MIN3(x,y,z) { returns smallest of the three values} If (x<y) Then m:=x Else m:=y If (m>z) Then m:=z MIN3:=m End Y = MIN3(5,4,6) { Y will be set to 4 when this statement executes} The AND and OR logical operators can also be used in the conditional test of an If Then Else statement. EES processes the logical operations from left to right unless parentheses are supplied to change the parsing order. Note that the parentheses around the (x>0) and (y<>3) are required in the following example to override the left to right logical processing and produce the desired logical effect. If (x>y) or ((x<0) and (y<>3)) Then z:=x/y Else z:=x 9 Note the the built-in MIN function accepts any number of arguments so this function would not be needed. 208 Functions, Procedures, Modules, and Subprograms Chapter 5 Multiple-Line If Then Else Statements The multiple-line If Then Else statement allows a group of statements to be executed conditionally. This conditional statement can be used in functions and procedures, but not in modules or the main body of an EES program. The format is as follows: If (Conditional Test) Then Statement Statement ... Else Statement Statement ... EndIf The If keyword, the conditional test, and Then keyword must be on the same line. The parentheses around the conditional test are optional. The statements which are to be executed if the conditional test is true appear on following lines. These statements may include additional If Then Else statements so as to have nested conditionals. An Else (or EndIf) keyword terminates this first group of statements. The Else keyword should appear on a line by itself, followed by the statements which execute if the conditional test is false. The EndIf keyword, which terminates the multiple-line If Then Else statement, is required and it must appear on a line by itself. The format is illustrated in the following example. Indentation is used to make the logic flow more clear. However EES ignores the blank spaces. Also upper and lower case are treated equally. Function IFTest(X, Y) If (X<Y) and (Y<>0) Then A:=X/Y B:=X*Y If (X<0) Then { nested If statement} A:=-A; B:=-B EndIf Else A:=X*Y B:=X/Y EndIf IFTest:=A+B End G=IFTest(-3,4) { G will be set to 12.75 when this statement executes} 209 Chapter 5 Functions, Procedures, Modules, and Subprograms GoTo Statements EES will normally process the assignment statements in a function or procedure in the order they appear starting with the first statement. However, the flow control can be altered using GoTo statements. The format of a GoTo statement is simply GoTo # where # is a statement label number which must be an integer number between 1 and 30000. Statement labels precede an assignment statement separated with a colon (:). The GoTo statement must be used with If Then Else statements to be useful. The following function illustrates the use of GoTo and If Then Else statements in the calculation of the factorial of a value supplied as the argument. Function FACTORIAL(N) F:=1 i:=1 10: i:=i+1 F:=F*i If (i<N) Then GoTo 10 FACTORIAL:=F End Y= FACTORIAL(5) { Y will be set to 120 when this statement executes} Return Statement The Return statement can only be used within Functions and Procedures. When EES encounters a Return statement, it will exit the Function or Procedure and control will resume at the point where the Function or Procedure was called. The Return statement is used in logic constructions with the If Then Else or Repeat-Until statement. Repeat Until Statements Looping within functions and procedures can be implemented with If Then Else and GoTo statements described above, but it is generally more convenient and readable to use a Repeat Until construct. The Repeat Until statement has the following format. Note that Repeat Until statements can only be used in functions and procedures. Repeat Statement Statement ... Until (Conditional Test) 210 Functions, Procedures, Modules, and Subprograms Chapter 5 The conditional test yields a true or false result using one of the following operators: =, <, >, <=, >=, and <> (for not equal). The format is identical to that used in Pascal. Here is the same Factorial example presented in the previous section implemented with a Repeat Until construct. Function Factorial(N) F:=1 Repeat F:=F*N N:=N-1; Until (N=1) Factorial:=F End Y= FACTORIAL(5) { Y will be set to 120 when this statement executes} Error Procedure The Error procedure allows the user to halt calculations if a value supplied to a function or procedure is out of range. The format of the Error procedure is: Call Error(‘error message’,X) or Call Error(X) where ‘error message’ is an optional character string enclosed within single quotes and X is the value of the parameter which caused the error. If the error message string is not provided, EES will generate the following error message when it executes the ERROR procedure. Calculations have been halted because a parameter is out of range. The value of the parameter is XXX. The value of X supplied to the Error procedure replaces XXX. If an error string is provided, EES will display that string, inserting the value of X in place of the characters XXX. If a formatting option, such as F1 or E4 follows the XXX, as in the example below, the value of X will be accordingly formatted, otherwise a default format will be applied. The ERROR procedure will most likely be used with an IF - THEN - ELSE statement as in the following example. Function abc(X,Y) if (x<=0) then CALL ERROR('X must be greater than 0. supplied.', X) abc:=Y/X end g:=abc(-3,4) When this function is called, the following message will be displayed and calculations will stop: X must be greater than 0. A value of -3.000E0 was supplied. 211 A value of XXXE4 was Chapter 5 Functions, Procedures, Modules, and Subprograms Warning Procedure The WARNING procedure can be used only within an internal function or procedure. The WARNING procedure generates a warning message which is placed in the warning message que and displayed when calculations are completed. Note that the message que is displayed only if the 'Display Warning Messages' checkbox in the Options tab of the Preferences dialog is selected, or if a$Warnings On directive is provided. The WARNING procedure is similar to the ERROR procedure which halts calculations when some user-specified error condition is encountered. The WARNING procedure has the following formats: CALL WARNING(X) CALL WARNING('My warning message XXXF1',X) CALL WARNING('My warning message') The warning string is optional, but if it is provided, it must be placed within single quote. If a warning string is provided, the variable X is optional. X is the value of the parameter which initiates the warning. If a warning string is not provided, EES will generate the following generic warning message. "A warning message was issued due to the value XXX in XXX." Here XXX is the parameter value provided in the WARNING call statement and YYY is the function or procedure name in which the Call WARNING statement appears. If a warning string is provided, EES will display that string, inserting the value of X in place of the characters XXX. If a formatting option, such as A3, F1 or E4 follows the XXX, as in the example above, the value of X will be accordingly formatted, otherwise a default format will be applied. If no format is supplied, automatic format is assumed. Note: To insert a string, rather than a numerical value, use $as the formatting option following the XXX, for example: CALL WARNING('My error string is XXX$',X$) The WARNING procedure will most likely be used with an IF - THEN - ELSE statement as in the following example. 212 Functions, Procedures, Modules, and Subprograms Chapter 5 Print Command in Functions and Procedures The Print command can be used with the assignment statements in Internal Functions and Procedures to output intermediate results. The format of the Print command is Print "filename" x, y, z Filename is the name of the text file into which the values of the designated variables will be written. Filename can be a string constant or a string variable. x, y, and z are names of variables within the Function or Procedure for which the values will be written to the designated file. The Print command will allow one or more more variable names to be specified. The values of the variables appearing in the Print command must be defined before the Print command is executed. The Print command will write to file each time the Print command is executed, creating a new row in the file output. The first column of each row will show the name of the function or procedure followed by the number of times the function or procedure has been called since the start of the calculations in parentheses. See the example below. The file will be cleared at the start of the calculations unless the Print command is followed by the /A option. In this case, the new information will be appended to the existing file; e.g., Print/A "filename", x, y, z Example: The following function will output values of i, x, and y in text file 'text.txt'. function test(x,y) t=x+y F$='text.txt' i=0 repeat i=i+1 print F$, i,x,y until (i>=t) test=t end g=test(2,3) Listing of file Text.txt after running the above program. "test(1)" 1 2 3 "test(1)" 2 2 3 "test(1)" 3 2 3 "test(1)" 4 2 3 "test(1)" 5 2 3 213 Chapter 5 Functions, Procedures, Modules, and Subprograms Modules and SubPrograms Modules and Subprograms can be considered to be stand-alone EES programs that can be called from the main EES program. The format of a Module / Subprogram is similar to that for an internal Procedure. The Module / Subprogram is supplied with inputs and it calculates outputs. Like a Procedure, the Module statement can (optionally) use a colon in the argument list to separate inputs from outputs. The number of arguments provided to the left of the colon is the number of degrees of freedom in the Module / Subprogram, or stated another way, the number of values that must be supplied to have the number of equations equal to the number of unknown. Examples of Module / Subprogram statements with a colon in the argument list are: MODULE Testme(A, B : X, Y) or SUBPROGRAM Testme(A, B : X, Y) In this case, EES understands that there are two inputs (A and B) and two outputs (X and Y). However, the equations in EES Modules / Subprograms are equalities rather than assignment statements as used in Procedures. In most cases, it does not matter what variables are specified as inputs as long as the appropriate number are specified. As a consequence, the colon which separates inputs from outputs is unnecesary and it can be replaced with a comma (or semicolon for the European numerical format). In fact, this is the preferred way to use Modules and Subprograms. The following Module / Subprogram statements are equivalent to the format shown above. MODULE Testme(A, B, X, Y) or SUBPROGRAM Testme(A, B, X, Y) A Module / Subprogram is accessed with a CALL statement. For example, the following statement would access the Testme Module or Subprogram. CALL Testme(77,1.5, X,Y) Note that if a colon is used to separate the inputs and output in the MODULE / SUBPROGRAM statement, it must also be used in the CALL statement. Similarly if a colon is not used in the MODULE /SUBPROGRAM statement, it should not be used in the CALL statement. At this point, you must be curious as to the difference between a Module and a Subprogram. The difference is as follows: When EES encounters a CALL statement to a SUBPROGRAM, it opens a new workspace and it then solves the equations in the SUBPROGRAM, using blocking and iteration as necessary. The calculated variables appearing as parameters in the SUBPROGRAM statement are returned to the main program. When EES encounters a CALL statement to a MODULE, it transparently grafts the equations in the module into the equations in the main program. The steps necessary for this process are as follows. First, every variable in the module, including each input and output in the MODULE statement, is renamed with a unique qualifier that EES can recognize. Then EES 214 Functions, Procedures, Modules, and Subprograms Chapter 5 adds one equation for each input and output which sets the value of the parameter in the calling program to the value of the value in the module. Note that the guess values and limits for the EES variables appearing in the CALL statement in the main program override the specified guess values and limits for the variables in the argument list of the MODULE statement. Finally, all of the equations in the module, with their renamed variables, are merged into the EES program at the point at which it is called. If the Module is called a second time, the process is repeated, but with a different qualifier for the variable names in the Module. The net effect is that a copy of all of the equations in the Module is merged into the main EES program each time a CALL statement is encountered. EES currently allows up to 6000 equations (10,000 in the Professional version) so rather large problems can be developed. EES then uses its efficient blocking techniques to reorganize the equations for optimal solution. As a result of this reorganization, the equations in the Module may not necessarily be called in sequence. In fact, this is rarely the case. You can view the equations in the order that EES has rearranged them in the Residuals window. Equations from a Module are identified with the Module name followed by a backslash and then the call index number. For example, the following equation in the Residuals window Turbine\2: h2=h1+Q/m indicates that the equation h2=h1+Q/m originated from the second call to the Turbine module. The Module / Subprogram is terminated with an END statement. A CALL statement is used to call the Module / Subprogram, just as for a Procedure. The important difference between a Procedure and a Module / Subprogram is that the Module / Subprogram is composed of equality statements whereas the Procedure is composed of assignment statements. Consequently, a Module / Subprogram cannot support logic constructs such as IF THEN ELSE, but it can provide iterative solutions to implicit equations, when needed, and order independent equation input, just as in the main part of EES. The following example uses a Module to solve an implicit set of two equations and two unknowns. The local values of variables in Modules / Subprograms are normally not displayed in the Solution window. However, you can view these local solutions for Modules / Subprograms 215 Chapter 5 Functions, Procedures, Modules, and Subprograms that appear in the Equations window by selecting the 'Show function/procedure/module variables' control in the Options tab of the Preferences dialog. So should you use a Module or a Subprogram? Limited tests thus far indicate that a Module tends to solve a problem more efficiently than a Subprogram, although you may wish to test both forms to determine which is better for your application. A major advantage of a Subprogram is that it can be called from a Function or Procedure. Conditional statements, such as the IF THEN ELSE, GOTO, and REPEAT - UNTIL are only supported in Functions and Procedures. If your application requires integration with conditional statements, you will necessarily have to use a Subprogram. Shown below is a short program which calls a Function that uses an IF THEN ELSE statement to call one of two Subprograms, one of which calls another function. Subprograms can call and be called by Functions and Procedures and that is their most significant difference from Modules. If automatic unit checking is enabled, EES will check the unit consistency of all equations in Subprograms and Modules. It will further check to see that the units variables provided in the Call statement match those in the Module or Subprogram statement. 216 Functions, Procedures, Modules, and Subprograms Chapter 5 Variables values are normally passed to a Module / Subprogram through the argument list. The$COMMON directive may be used to pass variables that are defined in the main program to a Module / Subprogram. Variable information, including guess values and lower/upper limits for Module / Subprogram variables is accessible with the Variable Info command. The local variables in a Module / Subprogram are always real regardless of the Complex Numbers setting. Modules / Subprograms may be stored as library files, just like Internal Functions and Procedures. The library files can be automatically loaded if they are placed in the USERLIB subdirectory. Alternatively, a $INCLUDE directive can be used to transparently load a library file. Help can be included within the Module / Subprogram (using the same syntax as used in Procedures) or it can be supplied with a separate help file having the same filename as the library file with a .HLP or .HTM filename extension. Modules and Subprograms can significantly increase the capabilities of your EES programming. 217 Chapter 5 Functions, Procedures, Modules, and Subprograms Library Files EES allows files containing one or more functions, procedures or modules (subprograms) to be saved as Library files. A Library file has a .LIB filename extension. When EES starts, it will automatically load all of the functions, procedures, and modules in the library files that reside in the USERLIB\ subdirectory or in subdirectories therein. Files within shortcut folders that ar eplaced in the USERLIB directory will also be automatically loaded. Library files can also be loaded manually with the Load Library command in the File menu and with the$INCLUDE directive. Library subprograms will not displayed in the Equations window. They are used just like EES built-in functions. To create a Library file, enter one or more functions, procedures, and/or modules into the Equations window. Compile the equations using Check, Solve or Solve Table. Then save the file with a .LIB filename extension using the Save As command. Subprograms in library files can provide help information in the Function Info dialog window, just like the built-in functions. There are several ways to provide the help information. The simplest way is to include the help text as a comment within the EES library file. In this case, the first character after the opening comment brace must be a $, followed by the name of the function, procedure or module followed by a carriage return. The lines following, up to the closing comment brace, are the help text that will be displayed when the user selects the Info button in the Function Info dialog window as shown in the example below. Alternatively, a separate help file can be supplied with the same name as the library file and a filename extension of .hlp or .htm. The .hlp file can contain ASCII text or it can be a Windows Help file. EES will be able to recognize the file type from its contents. The .htm file should be designed to be read by a browser. The Library file concept is among the most powerful features of EES because it allows the user to easily write customized subprograms for personal use or for use by others. The following example uses a library file to provide a fourth-order Runge-Kutta numerical integration function in EES. The Runge-Kutta algorithm is used to numerically solve a differential equation of the form: dY = f ( X ,Y) dX where f(X,Y) is any function involving the dependent variable Y and independent variable X. Y must have a known initial value, Y0, corresponding to the initial value of X. The Runge-Kutta algorithm has been implemented as a general purpose library function called RK4. RK4 requires 4 parameters: the initial value of X (LowX), the final value of X (HighX), the step size (StepX), and the value of Y at X=LowX (Y0). The function returns the value of Y at X=HighX. The RK4 function calls another function, fRK4(X,Y), to provide the value of dY/dX for given X and Y values. A dummy fRK4 function is provided in the RK4.LIB file as 218 Functions, Procedures, Modules, and Subprograms Chapter 5 a placeholder. In an actual application, the user overrides the dummy fRK4 function by entering another fRK4 function in the EES Equations window. The RK4 and fRK4 functions have been saved in a library file called RK4.LIB in the USERLIB\ sub-directory. EES will load these functions when it starts. If you were to open the RK4.LIB file in EES, you would see the following statements. Note how the functions provide help text as a comment with the$filename key. FUNCTION fRK4(X,Y) {$fRK4 fRK4 is a user-supplied function to evaluate dY/dX. This function is used with the RK4 function to solve differential equations with the Runge-Kutta method. Enter a fRK4(X,Y) function in the Equations window to evaluate dY/dY for your problem. See the RK4 function for additional information.} fRK4:=(Y+X)^2 END FUNCTION RK4(LowX,HighX,StepX,Y0) {$RK4 RK4 is a general purpose function which solves a first-order differential equation of the form dY/dX=fRK4(X,Y) using the Runge-Kutta 4th order algorithm. The RK4 function calls function fRK4(X,Y) supplied by the user to evaluate dY/dX at specified values of X and Y. The user must supply the fRK4 function. RK4 requires four input parameters. LowX is the initial value of independent variable X. HighX is the final value of independent variable X and StepX is the step size. Y0 is the value of Y when X is equal to LowX.} X := LowX Y := Y0; Tol := 0.1*StepX 10: IF (X>HighX-Tol) THEN GOTO 20 k1 := fRK4(X,Y)*StepX k2 := StepX*fRK4(X+0.5*StepX,Y+0.5*k1) k3 := StepX*fRK4(X+0.5*StepX,Y+0.5*k2) k4 := StepX*fRK4(X+StepX,Y+k3) Y := Y+k1/6+(k2+k3)/3+k4/6 X := X+StepX GOTO 10; 20: RK4:=Y END 219 Chapter 5 Functions, Procedures, Modules, and Subprograms 2 Suppose you wish to numerically solve the equation 0 X 2dx using the RK4 function. You provide a function fRK4 to evaluate the integrand, which is X2 in this case. Your function overrides the fRK4 function in the RK4 library file. Assuming RK4 was in the USERLIB\ subdirectory when EES was started, all that would be needed is: FUNCTION fRK4(X,Y) fRK4:=X^2 END V=RK4(0,2,0.1,0) When you solve this problem, EES will display V=2.667 in the Solution window. Note: The RK4 function solves an integral or differential equation using the Runge-Kutta algorithm. This algorithm works fine for differential equations it fails when there are combined algebraic and differential equations that must be solved. The built-in Integral function is more efficient for solving differential equations and integrals than the Runge-Kutta method described in the above example. The order in which library files are loaded can be an issue if one library file calls another. Note that library files in the USERLIB\EES_System folder are loaded before any other library files. Library files that are called by other library files and thus need to be loaded first can be placed in this folder. 220 CHAPTER 6 __________________________________________________________________________ __________________________________________________________________________ EES has an extensive library of built-in functions, but it is not possible to anticipate the needs of all users. A remarkable feature of EES is that the user can add (and later remove) functions and procedures written in any compiled language, such as Pascal, C, C++ or FORTRAN. These external routines may have any number of arguments. Functions return a single value whereas procedures may return multiple values. The external routines are used in exactly the same manner as internal EES subprograms. This capability gives EES unlimited flexibility and it is among its most powerful features. External functions and procedures are written as dynamic link library (DLL) routines under the Windows operating system. External functions are identified with a .DLF. There are two formats for external procedures identified by .DLP and .FDL filename extensions. Files having a .DLL filename extension can hold one or more functions and procedures. When EES is started, it examines the files in the \USERLIB\ subdirectory. Any files having a .DLF, .DLP, .FDL, or .DLL filename extension are assumed to be external functions or procedures and they are automatically loaded unless otherwise directed by the Library Manager described later in this chapter. External routines can also be loaded using the Load Library command in the File menu or with the $INCLUDE directive. The function name to be referenced in EES equations is the filename (without the extension). External functions and procedures can (optionally) be setup to work with the Function Info command (Options menu) so that they provide an example and detailed help when it is requested. The following sections in this chapter provide detailed information and examples of external functions and procedures. External Functions and Procedures EES External Functions (.DLF files) External functions can be written in C, C++, Pascal, or any language that can produce a dynamic link library (DLL). The function statement header, however, must have a specific format. To avoid having to set a fixed upper limit on the number of inputs, the input information to a external function is implemented as a linked list. The linked list record or structure consists of a double precision value and a pointer to the next input. The last input points to nil. FORTRAN 77 does not support pointers so .DLF external functions cannot be written in this language. The .FDL format described in this chapter should be used in this case. 221 Chapter 6 Compiled Functions and Procedures The external function should provide an example of the calling statement and check that the number of inputs supplied in the linked list is equal to the number the function expects. The PWF and SUM_C function examples in the following subsections show how this checking can be done in Pascal and C, respectively. Although the values of the inputs may be changed in the function, these changes are local and will be disregarded by EES. Only the function result will be used by EES. A skeleton listing of a external function written in Borland's Delphi 5 is as follows: library XTRNFUNC; type charstring=array[0..255] of char; ParamRecPtr = ^ParamRec; ParamRec = record { defines structure of the linked list of inputs } Value: double; next: ParamRecPtr; end; function FuncName (var S:charstring; Mode:integer; Inputs:ParamRecPtr):double; export; stdCall; begin ... FuncName:=Value; { Funcname must be double precision } end; exports FuncName; begin end. The major concern is the function header. To be recognized by EES, the function name, called FuncName in the above example, must be the same as the filename. The function statement has three arguments. S is a 256-character C string terminated with an ASCII 0. S can be used for both input and output. If the first parameter provided in the EES function is a string (within single quotes), EES will pass this string to the external routine. If an error is encountered, S should be set in the external routine to an appropriate error message. If the length of S is not zero, EES will terminate calculations and display S as an error message. Mode is an integer set by EES. If Mode=–1, then EES is requesting that the function return in S an example of the function call. If Mode>=0, then the function should simply return the function value. Currently, EES does not use the return value of Mode. Inputs is a pointer to the head of a linked list of input values supplied by EES. Each input consists of a value (double precision) and a pointer to the next input, as indicated by the 222 Compiled Functions and Procedures Chapter 6 ParamRec structure. The function may have one or more inputs. The next field of the last input will be a null pointer (nil). The function should count the inputs to be sure that the number supplied is as expected and issue an error message in S if this is not the case. A number of external functions are included with standard version of EES. For example, the following four functions implement a generalized equation of state using Redlich-KwongSoave equation10. Compress(Tr, Pr, w) returns the compressibility of a gas, i.e., the ratio of the specific volume of the gas to the specific volume of an ideal gas at the same conditions. Tr is the reduced temperature, Pr is the reduced pressure, and w is the acentric factor. The third parameter is optional. EnthalpyDep(Tr, Pr, w) and EntropyDep(Tr, Pr, w) return the dimensionless enthalpy and entropy departures, respectively. The dimensionless enthalpy departure is defined as (h[ideal]h)/(R Tc). h[ideal]-h is the difference in enthalpy between an ideal gas and a real gas at the same temperature and pressure, R is the gas constant and Tc is the critical temperature. The dimensionless entropy departure is similarly defined as (s[ideal]-s)/(R). FugCoef(Tr, Pr, w) returns the dimensionless fugacity coefficient (fugacity / pressure). Another useful function that is provided as an external function for EES is the PWF or Present Worth Factor function described in the following subsection. The PWF Function – a .DLF external routine in written in DELPHI EES does not have any internal economic functions. An economic function called the present worth factor (PWF)11 has been added as a external function. PWF is the present worth of a series of N future payments which inflate at rate i per period accounting for the time value of money with a market discount rate per period of d. The equation for PWF is PWF( N ,i,d ) = Σ N j=1 1+i j–1 j 1+d = 1 d –i 1– 1+i 1+d N 1+i N if i ≠ d if i = d where N is the number of periods (e.g., years) i is the interest rate per period, expressed as a fraction d is the market discount rate per period, expressed as a fraction 10 11 G. Soave, Chem. Eng. Science, Vol. 27, pp. 1197-1203, 1972 Duffie, J.A. and Beckman, W.A., Solar Engineering of Thermal Processes, 2nd edition, J. Wiley and Sons, 1992, Chapter 11. 223 Chapter 6 Compiled Functions and Procedures A external function, called PWF, has been written to do this economic calculation. This function is stored in the PWF.DLF file on the EES disk. EES treats this external function just like any of its internal functions. Shown on the following pages is the complete listing for the PWF external function written in Borland’s Delphi 3.0 (32-bit version). library PWFP; const doExample = -1; type CharString = array[0..255] of char; ParamRecPtr=^ParamRec; ParamRec=record Value:double; next:ParamRecPtr; end; function CountValues (P: ParamRecPtr): integer; var N: integer; begin N := 0; while (P <> nil) do begin N := N + 1; P := P^.next end; CountValues := N; end; {CountValues} function PWF(var S:CharString; Mode:integer; Inputs:ParamRecPtr):double; export; stdcall; var P: ParamRecPtr; V: double; function CountValues (P: ParamRecPtr): integer; var N: integer; begin N := 0; 224 Compiled Functions and Procedures Chapter 6 while (P <> nil) do begin N := N + 1; P := P^.next end; CountValues := N; end; {CountValues} function PWFCalc: double; var NArgs: integer; interest, discount, periods: double; begin PWFCalc:=0; {in case of error exit} S := ''; P := Inputs; Periods := P^.value; if (Periods < 0) then begin S := 'The number of periods for the PWF function must be >0.'; exit; end; P := P^.next; interest := P^.value; if (interest >= 1) or (interest < 0) then begin S := 'The interest rate is a fraction and must be between 0 and 1.'; exit; end; P := P^.next; discount := P^.value; if (discount >= 1) or (discount < 0) then begin S := 'The discount rate is a fraction and must be between 0 and 1.'; exit; end; if (interest <> discount) then PWFCalc := 1 / (discount - interest) * (1 - exp(Periods * ln((1 + interest) / (1 + discount)))) else PWFCalc := Periods / (1 + interest); end; {PWF} begin PWF:=1; 225 Chapter 6 Compiled Functions and Procedures if (Mode = doExample) then begin S := 'PWF(Periods,Interest,Discount)'; exit; end; if (CountValues(Inputs)<>3) then S := 'Wrong number of arguments for PWF function.' else begin PWF:=PWFCalc; end; end; {PWF} exports PWF; begin {no initiation code needed} end. When this Pascal code is compiled with the Borland Delphi 3.0, a dynamically-linked library routine is created. The compiler automatically generates a .DLL filename extension for the compiled code. EES must distinguish external functions from external Procedures. It does this by the filename extension. External functions must have a .DLF filename extension. Rename the external file so that it has a .DLF extension. Access the external PWF function by a statement of the following form in your EES program. P = PWF(Periods,Interest,Discount) 226 Compiled Functions and Procedures SUM_C – a .DLF external function written in Microsoft’s Visual C++ Chapter 6 The SUM_C function listed below returns the sum of its two arguments. There is of course no need for a function of this type in EES. However, this simple function clearly demonstrates how to write a .DLF external function for EES in C++. #include <windows.h> // Structure for handling EES calling syntax struct EesParamRec { double value; struct EesParamRec *next; }; // Tell C++ to use the "C" style calling conventions rather than the C++ mangled names extern "C" { __declspec (dllexport) double SUM_C(char s[256], int mode, struct EesParamRec *input_rec) { double In1, In2, sum_res; int NInputs; if (mode==-1) { strcpy(s,"a = SUM_C(b,c)"); // return example call string return 0; } // Check the number of inputs NInputs=0; EesParamRec * aninput_rec=input_rec; while (aninput_rec!= 0) { aninput_rec= aninput_rec->next; NInputs++; }; if (NInputs!=2) { strcpy(s,"SUM_C expects two inputs"); return 0; } In1= input_rec->value; input_rec=input_rec->next; In2=input_rec->value; sum_res = In1+In2; return sum_res; } }; 227 Chapter 6 Compiled Functions and Procedures EES External Procedures (.FDL and .DLP files) EES external procedures are very similar to EES external functions. In either case, the user supplies the function or procedure in external form as a Windows dynamically linked library routine. The major difference between functions and procedures is that procedures can return one or more values, whereas a function returns a single value. Procedures are useful, for example, for thermodynamic property evaluations where multiple properties (e.g., volume, enthalpy, entropy, etc.) are to be determined given one set of independent variables (e.g., temperature and pressure). External procedures are written dynamic link libraries (DLL's) in the Windows operating system. There are two formats for external procedures and they are identified to EES by their filename extension. The two formats differ in the manner in which EES exchanges information with the external routine. The .FDL format passes inputs and outputs in double precision floating point arrays. The .DLP format passes inputs and outputs as linked lists (as in the .DLF functions) so there is no limit to the number of inputs and outputs. EES identifies the format by the filename extension which must be .FDL or .DLP. External procedures using arrays to hold the inputs and outputs must have a .FDL filename extension. This is the usual case when providing DLLs written in FORTRAN. C, C++, and Pascal procedures can use either format. External procedures are accessed from EES with the CALL statement which has the following format, CALL procname(‘text’, A, B : X, Y, Z) where procname is the name of the procedure ‘text’ is an (optional) text string that will be passed to the procedure. This text can either be a string constant enclosed in single quote marks or a string variable. (See Chapter 7). A and B are inputs. There may be one or more inputs, separated by commas, appearing to the left of the colon. Inputs may be numerical constants, EES variable names, or algebraic expressions. String variables cannot be supplied as inputs. X, Y, and Z are outputs determined by the procedure. There should be one or more outputs to the right of the colon, separated by commas. Outputs must be EES numerical variable names. String variables cannot be provided for outputs. Note that the CALL statement used to access external functions is identical in format to the CALL statement used for internal EES Procedures. The following three sections describe the .FDL and .DLP external procedure formats and provide examples in FORTRAN, DELPHI, and C++ which should serve as a model. 228 Compiled Functions and Procedures External Procedures with the .FDL Format - a FORTRAN Example Chapter 6 The .FDL format is illustrated by the following FORTRAN subroutine fragments. The code may differs slightly depending on which compiler is being used. 32-bit .FDL library using the Digital Visual FORTRAN 6.0 compiler SUBROUTINE MYPROC(S,MODE,NINPUTS,INPUTS,NOUTPUTS,OUTPUTS) !DEC$ATTRIBUTES ALIAS:'MYPROC' :: MYPROC !DEC$ATTRIBUTES DLLEXPORT :: MYPROC INTEGER(4) MODE, NINPUTS, NOUTPUTS REAL(8) INPUTS(50), OUTPUTS(50) CHARACTER(255) S … OUTPUTS(1)=… … RETURN END S is a null-terminated C-style character string containing 255 characters. If the first parameter in the EES Call statement is a text string (within single quotes), EES will pass this string to the external program in S. When EES calls the subroutine with MODE =-1, it is asking for an example of the calling sequence of this procedure from EES to be placed in S so that it can be displayed in the Function Info Dialog window. S is also used to return user-supplied error messages if necessary. If an error is detected in the subroutine, MODE should be set to a value greater than 0 to signal EES to terminate calculations. If S is defined, it will be displayed in the EES error message. In normal operation, MODE =0 and S need not be defined. and NOUTPUTS are the number of inputs and outputs provided by EES. The routine should check to see if these agree with the expected number of inputs and outputs and return an error condition (MODE>0) if this is not the case. INPUTS and OUTPUTS are arrays of double precision (REAL*8) values. There is no inherent limit on the number of elements of these arrays, as EES will allocate memory as necessary. Up to 1000 variables can be passed in the argument list of external functions and procedures using array element notation, i.e., X[1..1000]. EES will supply the values in the INPUTS array. Results calculated by the subroutine are placed in the OUTPUTS. The external program must be compiled and linked as a dynamic link library (DLL) routine. The compiling procedure differs among different languages and compilers. NINPUTS Creating a 32-bit DLL with Digital Visual Fortran 6.0 is most easily done within the Microsoft Developer Studio environment. A new project workspace is selected as a Dynamic Link Library. The FORTRAN sources file(s) are inserted into the workspace and compiled with the standard options. Note that the two !DEC$ATTRIBUTES directives should be included in the main program, as noted above. The output filename in the Link settings should be set to MYPROC.FDL where MYPROC is the name that will be used in the EES Call statement. 229 Chapter 6 Compiled Functions and Procedures Alternatively, the default filename MYPROC.DLL should be changed to MYPROC.FDL after building the dynamic link library project. The simple FORTRAN program listed below provides the product, dividend, sum, and difference of two input values. This program should provide a model for writing external EES procedures in FORTRAN. SUBROUTINE MDASF(S,MODE,NINPUTS,INPUTS,NOUTPUTS,OUTPUTS) The following two lines are specific to Microsoft Power Station 4.0 !MS$ATTRIBUTES ALIAS:'MDASF' :: MDASF !MS$ATTRIBUTES DLLEXPORT :: MDASF INTEGER(4) MODE, NINPUTS, NOUTPUTS REAL(8) INPUTS(25), OUTPUTS(25) CHARACTER(255) S IF (MODE.EQ.-1) GOTO 900 IF (NINPUTS.NE.2) GOTO 100 IF (NOUTPUTS.NE.4) GOTO 200 DO CALCULATIONS X=INPUTS(1) Y=INPUTS(2) IF (ABS(Y).LE.1E-9) GOTO 300 OUTPUTS(1)=X*Y OUTPUTS(2)=X/Y OUTPUTS(3)=X+Y OUTPUTS(4)=X-Y MODE=0 S=''C RETURN CONTINUE ERROR: THE NUMBER OF INPUTS ISN'T WHAT THIS SUBROUTINE EXPECTS NOTE: SET MODE>0 IF AN ERROR IS DETECTED. IF S IS EQUAL TO A NULL STRING, THEN EES WILL DISPLAY THE MODE NUMBER IN AN ERROR MESSAGE. IF S IS DEFINED, EES WILL DISPLAY THE STRING IN THE ERROR MESSAGE. THE C AT THE END OF THE STRING INDICATES C-STYLE S='MDASF REQUIRES 2 INPUTS'C MODE=1 RETURN CONTINUE S='MDASF EXPECTS TO PROVIDE 4 OUTPUTS'C MODE=2 RETURN CONTINUE S='DIVISION BY ZERO IN MDASF'C MODE=3 RETURN CONTINUE PROVIDE AN EXAMPLE OF THE CALLING FORMAT WHEN MODE=-1 S='CALL MDASF(X,Y:A,B,C,D)'C RETURN END C. C. 100 C. C. C. C. C. C. 200 300 900 C. 230 Compiled Functions and Procedures External Procedures with the .DLP Format - a Pascal Example Chapter 6 The .FDL format described in the previous section was illustrated with FORTRAN, but it can be implemented in any compiled language. The .DLP calling format described in this section uses linked lists for inputs and outputs, and thereby is not suitable for use with FORTRAN. There is essentially no difference in efficiency between the two formats. Both are provided for backward compatibility and complete flexibility. External procedures using the .DLP format are very similar to external functions (.DLF files) described previously. The only difference is that a procedure must have, in addition to a linked list of input values, a linked list of output values. The calling sequence for a external Pascal procedure with the .DLP format has the following form procedure procname (var S: string; Mode: integer; Inputs, Outputs: ParamRecPtr); S, Mode, and Inputs are identical to their counterparts for the EES external functions. Outputs is a linked list of double values which provides the results of the calculations to EES in the order in which they appear in the CALL statement. Shown on the following page is a complete listing of an EES external procedure, called MDAS (an acronym for MyDearAuntSally) which provides the product, dividend, sum, and difference of two input values. (This is the same program used in the .FDL example.) The code checks to make sure that the number of inputs and outputs provided in the CALL statement are what the routine expects before it does the calculations and sets S to an error message if this is not the case. library MDASP; const Example = -1; type CharString = array[0..255] of char; ParamRecPtr=^ParamRec; ParamRec=record Value:double; next:ParamRecPtr; end; function CountValues (P: ParamRecPtr): integer; var N: integer; begin N := 0; while (P <> nil) do begin N := N + 1; P := P^.next 231 Chapter 6 end; CountValues := N; end; {CountValues} procedure MDAS(var S:CharString; Mode:integer; Inputs,Outputs:ParamRecPtr); export; stdcall; procedure MyDearAuntSally; var P1, P2: double; P: ParamRecPtr; begin P := Inputs; P1 := P^.Value; P := P^.next; P2 := P^.value; P := Outputs; P^.Value := P1 * P2; P := P^.next; P^.Value := P1 / P2; P := P^.next; P^.Value := P1 + P2; P := P^.next; P^.Value := P1 - P2; end; {doCall} begin {MDAS} if (Mode = -1) then S := 'CALL MDAS(In1,In2:Out1,Out2,Out3,Out4)' else begin if (CountValues(Inputs) <> 2) then begin S := 'Wrong number of inputs for MDAS.'; exit; end; if (CountValues(Outputs) <> 4) then begin S := 'Wrong number of outputs for MDAS.'; exit; end; MyDearAuntSally; S:=''; end; end; {MDAS} exports MDAS; begin {no initiation code needed} end. Compiled Functions and Procedures 232 Compiled Functions and Procedures External Procedures with the .DLP Format - a C++ Example Chapter 6 The .DLP format for external procedures can be written in C++. Listed here is the MDAS_C procedure which provides exactly the same capabilities as those provided above in FORTRAN and Pascal. #include <windows.h> // Structure for handling EES calling syntax struct EesParamRec { double value; struct EesParamRec *next; }; // Use the "C" style calling conventions rather than the C++ mangled names extern "C" __declspec (dllexport) void MDAS_C(char s[256], int mode, struct EesParamRec *input_rec, struct EesParamRec *output_rec) { double v, v1, v2; int NOutputs; EesParamRec *outputs, *inputs; if (mode==-1) { strcpy(s,"CALL MDAS_C(X,Y : M, D, A, S)"); return; } if (input_rec->next==NULL) { strcpy(s,"MDAS_C expects two inputs"); mode=1; return ; }; outputs=output_rec; NOutputs=0; while (outputs!=NULL) { NOutputs++; outputs=outputs->next; } if (NOutputs!=4) { strcpy(s,"MDAS_C requires 4 outputs"); mode=2; return ; } strcpy(s,""); inputs=input_rec; v1=inputs->value; inputs=inputs->next; v2=inputs->value; v=v1*v2; 233 Chapter 6 outputs=output_rec; outputs->value=v; outputs=outputs->next; if (v2==0) { strcpy(s,"attempt to divide by zero in MDAS_C"); mode=3; return; } v=v1/v2; outputs->value=v; outputs=outputs->next; outputs->value=v1+v2; outputs=outputs->next; outputs->value=v1-v2; mode=0; }; Compiled Functions and Procedures 234 Compiled Functions and Procedures Chapter 6 Multiple Files in a Single Dynamic Link Library (.DLL) EES recognizes three different types of externally compiled files. The three types are: DLF - dynamically-linked function DLP - dynamically-linked procedure FDL - dynamically-linked procedure with calling sequence accessible from FORTRAN Originally, only one external routine could reside in a file. The filename extension (.DLF, .DLP, or .FDL) identified the type of externally compiled file and the name of the external routine had to be the same name as filename (without the extension). However, it is also possible to place one or more external routines in a single file and this single file can contain all three types of external routines. The external file can have any name but it must have a .DLL filename extension. If this file is placed in the USERLIB subdirectory, EES will automatically load all the external routines in the file at startup provided that the Library Manager does not direct otherwise. (The Library Manager is described below.) EES must know the names of the external routines in the .DLL file and their type (.DLF, .DLP, or .FDL) because the calling arguments differ for each type. The mechanism for telling EES the names and types of the external routines is to provide three short routines in the DLL file with names DLFNames, DLPNames, and FDLNames that do nothing but return the calling names of each routine type in the DLL file. DLFName, DLPNames, and FDLNames must be exported in the DLL. They have one argument which is a character string. The character string is filled with the names of the routines of each type that are contained in the DLL file. A comma separates each file name. A zero length string is used to indicate that there are no files of that type. A short example in DELPHI 5 code follows. library MYEXTRNLS {This DLL file contains two DLF functions and one DLP procedure} uses SysUtils; const doExample = -1; {***********************************************************************} type CharString = array[0..255] of char; ParamRecPtr = ^ParamRec; ParamRec = record Value : Double; Next : ParamRecPtr; end; {***********************************************************************} {There are 2 functions; names are separated with commas} procedure DLFNames(Names : PChar); export; stdcall; begin StrCopy(Names,'myFunc1, myFunc2'); end; {***********************************************************************} 235 Chapter 6 {There is one DLP procedure} procedure DLPNames(Names : PChar); export; stdcall; begin StrCopy(Names,'myDLP'); end; Compiled Functions and Procedures {***********************************************************************} {no FDL procedures so return a null string} procedure FDLNames(Names : PChar); export; stdcall; begin StrCopy(Names,''); end; {***********************************************************************} function myFunc1 (var S: CharString; Mode: integer; Inputs: ParamRecPtr): double; export; stdCall; begin {Code for myFunc1} ... ... end; {myFunc1} {***********************************************************************} function myFunc2 (var S: CharString; Mode: integer; Inputs: ParamRecPtr): double; export; stdCall; begin {Code for myFunc2} ... ... end; {myFunc2} procedure myDLP(var S:CharString; Mode:integer; Inputs,Outputs:ParamRecPtr); export; stdCall; begin {Code for myDLP} ... ... end; {myDLP} {***********************************************************************} exports DLFNames, DLPNames, FDLNames, myFunc1, myFunc2, myDLP; begin end. 236 Compiled Functions and Procedures Chapter 6 #include <windows.h> #include <math.h> // Defines the entry point for the dll BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved ) { return TRUE; } // Tell EES which functions and procedures are exported in the library : // List of DLF format functions __declspec(dllexport) void DLFNames(char* Names) { strcpy(Names,"myFunc1,myFunc2"); } // List of DLP format procedures __declspec(dllexport) void DLPNames(char* Names) { strcpy(Names,"myDLP"); } // List of FDL format procedures __declspec(dllexport) void FDLNames(char* Names) { strcpy(Names,"myFDL"); } // DLF functions implementation __declspec(dllexport) double myFunc1(char s[256], int mode, EES_PARAM_REC *rec_in) {Code for myFunc1} ... ... return; } __declspec(dllexport) double myFunc2(char s[256], int mode, EES_PARAM_REC *rec_in) {Code for myFunc2} ... ... return; } // DLP procedure implementation __declspec(dllexport) void myDLP(char s[256], int mode, EES_PARAM_REC *rec_in, EES_PARAM_REC *rec_out) {Code for myDLP} ... ... return; 237 Chapter 6 } Compiled Functions and Procedures // FDL procedures implementation (FORTRAN style) // Note : fortran is always passing the length of the string after // a string parameter. FORTRAN is always expecting parameters to be // passed by reference // __declspec(dllexport) void myFDL(char s[256], int& clen, int& mode, int& NInputs, double inputs[25], int& NOutputs, double outputs[25]) { {Code for myDLP} ... ... return; } 238 Compiled Functions and Procedures Chapter 6 Help for External Functions and Procedures The Function Info dialog (Options menu) has an INFO button which, when used, provides help explaining the use of the selected function. When the user clicks the INFO button, EES will look for a file with the name of the external routine. This file can be an ASCII text file (with a .TXT extention, a portable document file (.PDF), a Windows .HLP file or an HTML file. This help file will be displayed if the file is found in the directory in which the external library file resides; otherwise a message will appear which states the help is not available for this item. If an ASCII file is provided, it should be formatted so that each paragraph ends with a carriage return. Long lines which do not fit within the Help window will be broken and word-wrapped as needed. Blank lines and spaces can be used to make the text more clear. Note that the .PDF format and the Windows .HLP and HTML (.HTM) files allow figures and formatting options to be used so it is a better way of providing help. These help file formats can be composed using any of the commercial Help generating programs. A single library file can hold many functions. For example, a (.DLL) library file written in EES can have any number of functions and procedures. It is possible to design a Windows .HLP file such that EES will jump the appropriate topic when the user clicks the Func Info button. This is done by providing a file containing help context information. The help context file has the same name as the library file but with a .CTX filename extension. EES will look for the .CTX file when help is requested. If a .CTX file is found, EES will open the file to find the context number for the topic that has the name of the function for which help is requested. The Help file will be then opened directly to that topic. If the topic is not found or if the .CTX file is not provided, the Help file will open to the first topic. Each line in the .CTX file contains two items: the context number (as it is used in the Help program) and a string which contains the function name. Shown below is the context file for the external files in the LiBr.DLL. 1 LiBr_External_Routines 2 H_LIBR 3 T_LIBR 4 P_LIBR 5 V_LIBR 6 X_LIBR 7 Q_LIBR 8 VISC_LIBR 9 COND_VISC 239 Chapter 6 Compiled Functions and Procedures Library Manager (Professional Version) Normally, all files placed in the USERLIB folder (within the folder that the EES.exe program resides) are automatically loaded when EES is started. These files can be library files with filename extensions .LIB, .FDL, .DLF, .DLP, or .DLL. Textbook menu files having a .TXB filename extension are also automatically loaded, but only one .TXB file can be active at a time. The user can control which files are loaded at startup by moving files into and out of the USERLIB folder. However, a more convenient alternative is to use the Library Manager provided in the Professional version of EES. The Library Manager is accessed by clicking the Auto Load button in the Function Information dialog. This button is visible when any of the radio buttons at the top right of the Function Information dialog are selected. Clicking Auto-Load will bring up a dialog having the appearance shown in the figure below. The Auto Load button is visible if either the EES Library Routines or the External Routines radio buttons is selected. Each file in the USERLIB folder appears in the list. The check box to the left of the list controls whether or not the file is automatically loaded when EES is started. If the checkbox is gray, the function is located in the EES_System directory and it cannot be unloaded in the Library Manager. Changing the loading status of any file has an immediate effect. If a file is not currently loaded, clicking the check box will automatically load the file and also ensure that it is loaded the next time EES is started. Unchecking a box will remove a loaded file from memory and prevent it from loading the next time EES is started. Information is written by the Library Manager into file LibraryManager.txt in the USERLIB folder. Deleting this file will cause all files to be automatically loaded. 240 CHAPTER 7 ____________________________________________________________________________ ____________________________________________________________________________ The advanced features in EES allow the program to work with string, complex, and array variables and solve simultaneous algebraic and differential equations. The commands and functions which implement these features are described in this chapter and illustrated with examples. Advanced Features String Variables EES provides both numerical and string variables types. A string variable holds character string information. A string variable is identified to EES with a variable name that ends with the $character, as in the BASIC language. The variable name must begin with a letter and consist of 30 or fewer characters, including the$ character. String variables can be set to string constants. A string constant is a set of up to 255 characters enclosed within single quote marks, e.g. A$='carbon dioxide' String variables can be set equal to other string variables, e.g., B$=A$String variables may be passed as arguments to internal functions, procedures and modules or to external functions and procedures as described in Chapter 6. In general, string variables can be used in EES equations anywhere in which character information is provided. For example, the name of a fluid provided to a thermophysical property function may be a string variable, e.g., h=enthalpy(R$,T=T,P=P) String variables may be used with the Parametric table. In the example below, a Parametric table is used to tabulate the values of specific enthalpy for four refrigerants at 0°C, 100 kPa. Note that the single quote marks which are normally used when specifying a string constant should not be used when entering the strings in the Parametric table. 241 Chapter 7 Advanced Features A string variable may be used to hold the name of a Lookup file or the name of a column for use with the Interpolate or Lookup commands, e.g., m=Interpolate(File$,Col1$,Col2$,Col1$=x) k=Lookup(File$,Row,Col$) String variables can be used to specify the units of other variables. For example: U$='kJ/kg' h=15 [U$] The comment to the right of the 15 sets the units of variable h to U$. The units could also be set in the Variable Info dialog or by clicking on h in the Solution window. In any case, EES will recognize that U$ is a string variable and set the units of h to the string that is assigned to U$. String variables may be supplied to the Equations Window using the Diagram Window, either with an edit box or with a pull-down list of alternatives. See the Diagram Window section in Chapter 2 for more information on this capability. Complex Variables EES will solve equations involving complex variables of the form a+b*i if the ‘Do Complex Algebra’ control in the Complex tab of the Preferences dialog is checked. The imaginary number operator may be set to either i or j in the Preferences dialog although i is used in the following discussion. When set in complex mode, every (non-string) EES variable is represented internally as two variables corresponding to the real and imaginary components of a complex number. The real part is internally identified by appending _r to the variable name. The imaginary part has an appended _i. (You should not use _r or _i at the end of a variable name unless you are 242 Advanced Features Chapter 7 specifically referring to the real or imaginary component.) If, for example, you enter the equation X=Y EES will automatically create variables X_r, X_i, Y_r and Y_i corresponding to the real and imaginary components of the variables. You will normally not have to refer to the renamed variables, although they will appear with these names in the Variable Info and New Parametric Table dialogs, as well as in column headers of the Parametric Table. However, you can set the value of a real or imaginary part of a complex number by entering the real or imaginary variable name on the left of an equation in the Equations window. For example, the following equation will set the imaginary part of variable omega to 0. omega_i=0 Any later attempt to set the imaginary part of omega will cause EES to display an error message. If, for example, you also enter the equation, omega = 3 in the Equations window, EES will present an error message when you attempt to solve because the omega=3 equation sets both the real and imaginary parts of omega and the imaginary part would have already been set. You could, of course, enter omega_r=3. Complex numbers can be entered in either rectangular or polar form. In rectangular form, the complex number is entered using the imaginary number operator (i or j) with a multiplication symbol (*) separating the imaginary number operator from variables or constants. A complex constant can be entered in polar form by entering the magnitude (also called absolute value) of the number and the angle separated with the < symbol. The < character will be displayed in the Solution and Formatted Equations windows as ∠. The angle can be entered in either degrees or radians. If no designation is provided, the angle is assumed to be in the same units as indicated for trigonometric functions in the Unit System dialog. However, you can ensure that the angle you enter is in degrees or radians regardless of the unit system setting by appending deg or rad to the number (with no spaces). For example, the value of Y can be set to the same complex constant in any one of the following three ways. Y=2 + 3 * i Y=3.606 < 56.31deg Y=3.606 <0.9828rad The use of deg or rad to indicate the units of the angle is strongly recommended for three reasons. First, the value of the constant you enter will not be changed by the unit system 243 Chapter 7 Advanced Features setting. Second, you can enter complex variables in polar form with the angle in degrees yet do all calculations with the unit setting in radians which is more efficient. Third, if you designate the angle to be in degrees, the degree sign will be shown with the angle in the Formatted Equations window. The output display of the number in the Solution Window can be set for degrees or radians (in polar notation) independent of how the number is entered. The display is changed by clicking the right mouse button on the value and selecting the display options from the Format Variable dialog. Internally, EES creates two equations for each equation that is entered in the Equations window. One equation is used to equate the real parts of the variables whereas the second equation equates the imaginary parts. The actual set of equations used in complex mode is most clearly seen by viewing the Residuals window which displays the residual and blocking order for each equation. Equations used for the real and imaginary parts are identified with (r) and (i), respectively. When configured in complex mode, some EES functions, such as Min and Max, are not accessible. However, most of the built-in functions (including the thermophysical property functions) have been modified to work with complex numbers. For example, the sin, cos, ln, exp, and tanh functions will accept and return appropriate complex numbers. User-written functions, procedures, and external routines can be used but they will accept and return real numbers only. (Modules are currently not supported in complex mode.) Only the real part of a complex variable will be placed in the argument list of internal or external functions, procedures, and modules. There are a few built-in functions that operate only in complex number mode. They are Real, Imag, Cis, Magnitude, Angle, AngleDeg, AngleRad, and Conj. These functions all take one (complex number) argument and set the real part of the complex variable to the selected value. One limitation of the manner in which EES implements complex numbers is that EES can only return one solution, although two or more solutions may exist. There is, however, a simple way to coax EES into providing multiple solutions. Consider the problem of determining the five roots to the complex equation z5 + 9 + 9 i = 0. Entering this equation into the Equations window and solving with the default guess values will produce a solution of z=1.176+1.176 i. Setting the Solution window display to polar (degree) coordinates will produce the following solution. 244 Advanced Features Chapter 7 This is a correct solution to the equation, but there are four others. To find a different solution (without changing guess values), divide the equation by the difference between z and the value of this root. The Formatted Equations window will appear as shown. Now, a second solution will be found. This process can be repeated to find the third, fourth, and fifth roots. The Formatted Equations window and solution for this last step are shown below. 245 Chapter 7 Advanced Features Array Variables EES recognizes an array variable by placing the array index within square brackets, e.g. X[5]. Multi-dimensional array variables may also be used with the indices separated by commas, e.g., Z[1,2,3]. The special requirements pertaining to array variables are: 1. An array index may be an integer number, an EES variable which has been previously set to a constant value, the TableRun# function, or an algebraic expression involving these quantities with operators +, –, *, and /. Index arithmetic is done left to right with no operator precedence. For example, X[2*3+1] is a valid array variable which EES will transform into X[7]. X[1+2*3] will be transformed into X[9]. The index variable for the DUPLICATE command or the sum or product functions can also be used in an expression for the array index as shown below. 2. Valid index values range between –32760 and +32760, including zero. 3. The right bracket must be the last character in the variable name. 4. The total length of the variable name, including the brackets and the integer value of the index, must not exceed 30 characters. 5. Array values can be entered with a short-hand array range notation (see below), e.g., X[1..4]=[11, 22, A*B, Z^2] EES treats array variables in a very different manner than FORTRAN or Pascal. In EES, each array variable, such as X[99], is a unique variable name. As such, X[99] appears to EES just like any other variable such as ZZZ. The guess value and bounds (along with other information) may be specified for X[99] with the Variable Info command, just as for any other variable. It is legal (but not good practice) to have EES variables names of X, X[1], X[2,3] all within the same equation set. The fact that X[99] appears in the Equations window does not cause EES to reserve memory for 99 elements. Memory is allocated only for the variables which appear in the equations. Array variables can be useful in several ways. They provide a means of grouping variables of similar type. For example, the temperatures at each state in a system can be written as T[1], T[2], etc. Array variables can be plotted. For example, the temperature and entropy of each state in a thermodynamic cycle can be overlaid on a T-s property diagram. See Property Plot in the Plot Menu section of Chapter 3 for details. Finally, array variables can be used with the DUPLICATE command and the sum and product functions to provide matrix capability and thereby significantly reduce the amount of typing needed to specify some problems. Array Range Notation Array range notation is a shorthand notation to facilitate passing of array variables to internal and external Functions and Procedures. A range of array variables can be indicated by separating the first array index value from the last index value by two decimal points. For 246 Advanced Features Chapter 7 example, X[1..5] can be used in place of X[1], X[2], X[3], X[4], X[5] as the argument list to a function. This shorthand notation is supported for two dimensional array variables as well, e.g., Z[2,1..3]. EES variables may be used in the index range (e.g., X[N..M]) provided that their values have been previously set in assignment statements. The notation can be used in the arguments of function calls and CALL statements, in Function and Procedure statements and in$Common directives. Array range notation can be convenient when array variables are being used as arguments to internal and external functions. However, the major purpose of this notation is to allow long argument lists to be passed. A long argument list is not possible in any other way since EES statements must be 255 or fewer characters. A maximum of 2000 arguments may be passed to a function or procedure using array range notation. Array range notation can be used with variable limits, provided that the variable is previously specified. For example, X[1..n] can be used if n is set to a value in a statement before the X[1..n] is encountered. When Array range notation is used in the header statement of an internal Function or Procedure, a problem occurs since the value of variable, cannot possibly be known. In this case, EES provides a default maximum dimension which currently is 100. If you wish to have a larger maximum, you can specifically provide a number for the maximum. This capability is only applicable for one-dimensional arrays. The calling program can provide any number of elements for the array provided it is less than the maximum. The following example illustrates array range notation. 247 Chapter 7 Advanced Features The DUPLICATE Command The DUPLICATE command provides a shorthand way of entering equations into EES. The equations which are to be duplicated are enclosed between the DUPLICATE and END command words. DUPLICATE is useful only when used with array variables. For example, the following statements: N=5 X[1]=1 DUPLICATE j=2,N X[j]=X[j–1]+j END are equivalent to: X[1]=1 X[2]=X[1]+2 X[3]=X[2]+3 X[4]=X[3]+4 X[5]=X[4]+5 Note that, within the scope of the DUPLICATE command, the DUPLICATE index variable (j in the example above) can be used in an algebraic expression for the array index. The DUPLICATE index is not an EES variable, but rather just a temporary placeholder for the integers applied in the DUPLICATE command. The special format requirements pertaining to the DUPLICATE command are as follows: 1. The DUPLICATE command must be on its own line in the Equations window or separated from other equations with a semicolon. 2. The lower and upper loop limits can be any of the following: i) a numerical quantity or expression ii) an EES variable that has been set to a value ahead of the Duplicate statement iii) an EES variable that is set to a value in the Parametric tableWindow_Parametric iv) the TableRun#_TABLERUN_ keyword. 3. DUPLICATE commands may be nested within one another as deep as desired. However, each DUPLICATE command must use a different index variable name and each must be terminated with an END command. The lower or upper limit of an internal DUPLICATE may be the index value of an external DUPLICATE, e.g., DUPLICATE i=1,5; DUPLICATE j=i,6; X[i,j] = i*j; END; END 4. The END command terminates the last opened DUPLICATE command. 248 Advanced Features Chapter 7 Matrix Capabilities Many engineering problems can be formulated into a linear system of algebraic equations of the form [A] [X] = [B] where [A] is a square matrix of coefficients, and [X] and [B] are vectors. Ordinarily, the matrix equation is solved to determine the elements in the vector [X] for known [A] and [B]. In this case, [X] = [A] [B] EES can directly solve the equations represented by [A] [X] = [B] by entering each equation directly into the Equations window in any format or order. However, a more elegant and convenient method for solving these equations in EES is to make use of the matrix capability. EES can solve matrix equations, formulated with array variables, by using the DUPLICATE command and the sum function. For example, consider the following radiation heat transfer problem in which [A] and [B] are given below, and the radiosity vector, [X] is to be determined.12 -1 LM10 A = M −1 MN−1 −1 −1 3.33 −1 −1 2 OP PP Q LM940584OP B = M 4725 P MN 0 PQ The equations required in EES to solve this problem are as follows: The calculated elements in the X array will appear in the Arrays window. 12 Incropera, F.P. and DeWitt, D.P., Fundamentals of Heat and Mass Transfer, 2nd edition, John Wiley and Sons, 1985, Chapter 13 249 Chapter 7 Advanced Features Note that it was not necessary to determine the inverse of [A] to obtain the solution. EES calculates the inverse matrix internally, as needed to solve these and any other simultaneous equations. However, the inverse matrix [A]-1 can be determined by setting the matrix product [A] [A]-1 equal to the identity matrix in the following manner. The inverse matrix Ainv will appear in columns of the Arrays window. The two examples above provide a general procedure for determining the product of a matrix and a vector or the product of two matrices. Using the DUPLICATE command along with array variables in EES is no more efficient than the alternative of entering each equation separately with non-array variable names; however, the matrix capabilities in EES can significantly reduce the amount of typing required to enter the problem and, more importantly, make the equations easier to follow. 250 Advanced Features Chapter 7 Using the Property Plot The Property Plot menu item in the Plot menu generates T-s, T-v, P-v, or P-h diagrams for any of the fluids in the EES data base. A psychrometric chart is generated if substance AirH2O is selected. The property plot is placed in one of the EES plot windows. Additional property data or thermodynamic state point information can be superimposed on the property plots using the Overlay Plot command in the Plot menu. Overlays can be plotted if array variables are used for the thermodynamic variables. Another benefit of using array variables is that the state property data then appear in the Arrays Table in a convenient tabular form. The P-h plot below shows the state points for simple refrigeration cycle operating between an evaporator temperature of 10°C and a condensing temperature of 48°C with a compressor isentropic efficiency of 0.70. The plot was prepared by first producing a P-h plot for R12 with isotherms at 10°C and 48°C with the Property Plot command and then overlaying the P[i] and h[i] arrays (plotting from the Arrays table) for the four state points in a refrigeration cycle analysis. The equations can be found in file REFRIG.EES in the Examples subdirectory. 251 Chapter 7 Advanced Features Integration and Differential Equations The INTEGRAL function is used to evaluate an integral and in the solution of differential equations. The format of the Integral function is: t2 f dt = Integral(f, t) t1 There are two basic forms of the integral function which differ in their reliance on the Parametric table. Table-based Integral function The table-based Integral function uses the Parametric table to provide the limits and step size of the integration variable. The format of this function is Integral(f, t). This form of the Integral function can be used only in conjunction with the Parametric Table. The integration variable, t, must be a legal variable name which has values defined in one of the columns of the Parametric table. The limits on the integration variable, t1 and t2 are the first and last values specified for variable t. The integrand, f, can be a variable or any implicit or explicit algebraic expression involving variables, values, and the integration variable, t. Equation-based Integral function The Equation-based integral function serves the same purpose as the table-based integral function but it does not require the use of the Parametric table. The format for the equationbased integral function is F = INTEGRAL(f, t, t1, t2, tStep) or F = INTEGRAL(f, t, t1, t2) {automatic step size} t1 and t2 are the lower and upper limits of the integration variable. These limits may be specified with a constant or an EES expression. However, the limits cannot be a function of the integration variable t or any other variable which changes during the course of the integration. tStep is the increment EES will use for the integration variable while numerically evaluating the integral between the specified limits. tStep can vary during the course of the integration. This capability allows, for example, the user to provide a function in which the step-size is small at the start of the integration but increases as the integration proceeds. Note that specification of tStep is optional. If tStep is not provided, EES will select the stepsize using an automatic stepsize adjustment algorithm as specified in the Integration tab of the Preferences dialog. 252 Advanced Features Chapter 7 EES uses a second-order predictor-corrector algorithm for evaluating the integral. This algorithm is designed for solving combined algebraic and differential equations which result when the integrand is a complex function of other variables. The algorithm is especially suited to stiff equations. EES uses the Integral function to solve initial value differential equations. Any first-order differential equation can be transformed into an appropriate form by integrating both sides. For example, the differential equation, dy/dx = f(x,y) can be equivalently written as y = y0 + f(x,y) dx where y0 is the initial value of y. This equation can be solved using either the table-based or equation-based forms of the Integral function. The table-based form would be entered into the EES Equations Window as y = y0 + INTEGRAL(fxy, x) where fxy is an EES variable or expression. To solve the equation it is necessary to create a Parametric table containing a column for variable x. Values of x are entered into the Parametric table with the value in first row corresponding to the lower limit of x and the value in the last row corresponding to the upper limit. The step size is determined by the difference between the value of x in successive rows and need not be a fixed value. The integral is evaluated when the Solve Table command is applied. The equation-based form would appear in the EES Equations window as y = y0 + INTEGRAL(fxy, x, low, high) y0 and fxy are as defined above. Low and high are the lower and upper limits for x. A Parametric table is not required for use with this form of the Integral command. Since the stepsize is not specified, EES will use automatic stepsize selection. Solving First-Order Initial Value Differential Equations Initial-value differential equations can be solved in a number of ways with EES. Chapter 5 describes a Library function included with EES in the USERLIB subdirectory which implements a 4th order Runge-Kutta algorithm. This method can only be used if the derivative can be expressed explicitly as a function of the dependent and independent variables. This section demonstrates two ways of solving simultaneous algebraic and differential equations using the Integral function or the TableValue function in conjunction with the Parametric Table. 253 Chapter 7 Advanced Features Method 1: Solving Differential Equations with the Table-Based Integral Function Consider the problem of determining the time–temperature history of a sphere of radius r=5 mm, initially at a uniform temperature of 400°C. The sphere is exposed to 20°C air with a convection coefficient of h=10 W/m2-K. The thermophysical properties of the sphere material are: ρ = density = 3000 kg/m3 k = thermal conductivity = 20 W/m-K c = specific heat = 1000 J/kg-K Calculation of the Biot number will indicate that the sphere can be treated as a lumped system, and therefore it may be assumed to be at a uniform temperature at any instant of time.13 The relation between the sphere temperature and time is given by an energy balance on the sphere, which results in the following differential equation – h A (T – T∞) = ρ c V d T dt where h is the convective heat transfer coefficient T is the uniform temperature of the sphere at any time T∞ is the temperature of the air stream = 20°C A is the surface area of the sphere = 4 π r2 V is the volume of the sphere = 4/3 π r3 t is time This differential equation has the following analytic solution which can be used to check the accuracy of the numerical solution provided by EES. T – T∞ = exp – h A t ρcV Ti – T∞ To solve the differential equation numerically in EES, enter the following equations. 13 Incropera, F.P. and DeWitt, D.P., Fundamentals of Heat and Mass Transfer, 2nd edition, John Wiley and Sons, 1985, Chapter 5 254 Advanced Features Chapter 7 Next, a Parametric Table is generated with the New Table command in the Parametrics menu. (Note that, if the start and stop times were provided as the third and fourth parameters for the Integral function, it would not be necessary to use the Parametric table. Intermediate results for times between the start and stop times could be directed to the Integral Table using the $IntegralTable directive as shown in Method 2.) Select T, Time, and Texact as the three variables to include in the table. Enter 11 runs which will allow a time–temperature history for 1000 seconds starting at 0 with 100 second intervals. The New Table dialog window should now appear as shown below. Click the OK button. It is next necessary to enter the values of Time in the table for which the temperature T is to be calculated. A timestep of 100 seconds has been chosen. With a fixed control at the timestep, the values of Time can be most easily entered by clicking on the upper right of the Time column header cell. Enter 0 for the First Value. Set the drop-down list control to ‘Last Value’ and enter 1000 for the last value as shown. 255 Chapter 7 Advanced Features The value of Time from 0 to 1000 will be automatically entered into the table when you click the OK button and displayed in normal type. Now select Solve Table from the Calculate menu to calculate the numerical and analytical values of temperature corresponding to each value of Time in the table. When the calculations are completed, the Parametric Table window will display the solutions. Calculated values are shown in bold. (The format of calculated values in the Parametric Table can be set using the Preferences command in the Options menu.) The plot shows that the numerically determined temperature agrees closely with the exact analytic solution. 256 Advanced Features Chapter 7 257 Chapter 7 Advanced Features Method 2: Use of the$Integral Directive and the Equation-Based Integral Function In this section, we solve the same first-order differential equation described in Method 1 using the equation-based Integral function in conjunction with the $IntegralTable directive. The equation-based Integral function does not employ the Parametric table to specify the values of the integration variable, as does the table-based Integral function. Rather, the lower and upper limits and optionally, the step size of the integration variable is specified as arguments within the Integral function, e.g., F = Integral (Integrand, VarName, LowerLimit, UpperLimit, StepSize) The last argument in the Integral command is the integration step size. If a step size is not provided or if the step size is 0, EES will use automatic step size. Normally, EES does not keep intermediate values of any variable used during the numerical integration. Such information is needed if you with to know the trajectory or path of variables as well as their values at a specified time. The$IntegralTable directive instructs EES to store the intermediate values in an Integral Table. The values can then can be plotted, printed, or copied to another application. The format of the $IntegralTable directive is:$IntegralTable Time:100, T, Texact where Time is the integration variable, but it of course can have any legal EES variable name. Time is used here as an example. This variable must appear in one or more equation-based Integral functions within the Equations window. The first column in the Integral Table will hold values of this variable. The colon and number (or variable) following the integration variable are optional. If a number is supplied, this number will be taken to be the output step size and integration variables will be reported in the Integral Table at the specified step size. If a step size is provided, it must be a number - not a variable. If a step size is not specified, EES will select a step size. Note that the step size used to report integration results is totally independent of the step size of used in the numerical integration. If the numerical integration step size and output step size are not factors, linear regression will be used to determine the integrated quantities at the specified steps. The remaining parameters in the $IntegralTable directive are variables in the EES program that you wish to see as a function of the integration variable. T and Texact have been selected here. A separate column will be created in the Integral Table for each specified variable. Array range notation, e.g., X[1..5] can be used. The variables must be separated by a space or list delimiter. When calculations are initiated, EES will first check to ensure that all variables in the$IntegralTable command are used in the equations. If no errors are found, an Integral Table will be created and filled with intermediate values results from the numerical integration. 258 Advanced Features Chapter 7 Values from this table can then be plotted, printed, and copied, in exactly the same manner as for other tables. When the $IntegralTable directive is used with the Solve Table command, an Integral Table is produced for each run (i.e., row) of the Parametric Table. Only one Integral Table can be viewed at one time. The run number control in the upper left cell of the Integral Table indicates the Parametric Table run number for which data are currently displayed. This run number may be changed by clicking on the up/down arrows or by directly entering the run number. The data in the table will be automatically updated when the run number is changed. Shown below are the Equations window and the Integral Table that is produced when the equations are solved. 259 Chapter 7 Advanced Features Method 3: Solving Differential Equations with the TableValue Function In this section, we solve the same first-order differential equation described in Method 1. – h A (T – T∞) = ρ c V d T dt The differential is approximated as new old d T ∼T – T Δt dt T new is the temperature at the current time which is to be calculated. T old is the temperature at the previous time which can be found in the previous row of the Parametric table using the TableValue function. The TableValue function returns the value in the Parametric Table at a specified row and column, as described in Chapter 4. With this function, it is possible to access the values of variables calculated in previous runs during the Solve Table calculations. Δt is the timestep which, in the equations shown below, is the difference of the current and previous values of the variable Time. Both an explicit method (Euler's method) and an implicit method (Crank-Nicolson) are used to solve this first-order differential equation and compared with the exact solution. In the Euler method, only previous temperatures are used to evaluate the right-hand side of the differential equation. In the Crank-Nicolson method, the average of the previous and current temperatures is used. The Crank-Nicolson method is implicit because the current temperature is not as yet determined. The implicit method is no more difficult to implement since EES is designed to solve implicit equations. Shown below is a listing of all of the equations needed to solve this problem. Most of the equations are identical to those used for Method 1. T_Euler is the temperature calculated by Euler’s method. T_CN is the temperature calculated by the Crank-Nicolson method. (In the Formatted Equations and Solution windows, these variables will display as TEuler and TCN, respectively.) To proceed, a Parametric table must be defined, as in Method 1. The values of T_Euler, T_CN and T_exact in the first row of the table, corresponding to Time=0, are the initial conditions and their values (400°C) must be entered. Then, the Solve Table command is used to complete the table, with calculations starting at Run 2. Note the use of the TableRun# function to return the row number in the Parametric Table for which calculations are currently being done, and the TableValue function which returns the value at a specified row and column in the Parametric Table. 260 Advanced Features Chapter 7 Shown below is the completed table with the numerical and analytical solutions. Calculated values are shown in italics. It is evident that Euler’s method does not provide as accurate a solution as that obtained with the Integral function (Methods 1 and 2) or the Crank-Nicolson method. Improved accuracy could be obtained by reducing the time step, but this would require additional computational effort and storage space (which is not significant here). 261 Chapter 7 Advanced Features Solving Second and Higher Order Differential Equations Higher order differential equations can also be solved by repeated use of the Integral function. Shown below is an EES program which solves a second-order differential equation to calculate the velocity and position of a freely falling object, subject to aerodynamic drag. The Solution Window appears after the Solve command (F2) is issued. The Integral Table that is produced shows how the velocity and position of the object vary with time. 262 Advanced Features Chapter 7 263 Chapter 7 Advanced Features Multiple-Variable Integration Multiple integration is provided by nesting calls to the Integral function. Up to six levels can be nested. The following example performs a numerical double integration using the equationbased Integral function. 264 Advanced Features Chapter 7 Directives Directives are special EES commands that are placed in the Equations window. Directives are distinguished from equations by the$ that precedes each directive name. The directives are listed alphabetically with a short description of their functions. $ARRAYS On/Off Directive EES provides an option in the Preferences dialog to display array variables, e.g., X[5], in a separate Arrays window, rather than in the Solution window. This option and other preferences are not saved with a EES program but rather with the user preferences. In some situations, it is desirable for the EES program to control whether the Arrays window is used or not used. This can be done with$ARRAY On or Off directive in the Equations window. $BOOKMARK Name The$Bookmark directive must be on a line by itself with the $character in the first column. Name is any name that you wish to associate with the text that follows the$Bookmark directive. The Name that you supply will be sorted in alphabetical order and placed in the lower section of the Search menu and in the popup menu that appears when you press the right mouse button within the Equations or Formatted Equations window. Selecting the Name from either of these menus will adjust the vertical scrolling of the Equations or Formatted Equations window so that the information following the selected $Bookmark directive appears near the top of the window.$CHECKUNITS On/Off/AutoOn/AutoOff When EES encounters a $CHECKUNITS Off directive, equations that follow will not be subject to unit checking.$CHECKUNITS On restores the unit checking to the equations that follow. Automatic unit checking is controlled with the Check Units Automatically option is set in the General Tab of the Preferences dialog. When automatic unit checking is enabled, the unit consistency of all equations will be checked each time the Solve or Solve Table command is applied. The results of the unit checking will be summarized in the Equations window. Also, when automatic unit checking is on, the Residuals window will display a Units column indicating OK, ? or X for the status of the unit checking of each equation. OK indicates that the units appear to be correct. ? indicates that a problem was found. X indicates that the equation was not checked for unit consistency. The X will appear if the equation follows a $CHECKUNITS Off directive or if the unit checking was disabled for this equation by rightclicking on it in the Residuals window.$CHECKUNITS AutoOn/AutoOff overrides the setting in the Preferences dialog. To ensure that automatic unit checking is on, place the following directive at the top of the EES file. $CHECKUNITS AutoOn 265 Chapter 7 Advanced Features$COMMON Directive The $COMMON directive provides a means for passing information from the main program to internal functions, procedures, and modules. Use of$COMMON provides an alternative to passing values as arguments. This directive is similar in concept to the COMMON statement in FORTRAN. It differs in that information flow is one-way. Variable values can be passed from the main program to the function or procedure. However, the function or procedure may not assign or alter these values. The $COMMON directive must directly follow the FUNCTION, PROCEDURE, SUPROGRAM, or MODULE declaration on a line by itself. Variables appearing in the$COMMON statement are separated with commas, as in the following example. FUNCTION TESTCOMMON(X) $COMMON B,C,D {variables B,C, and D are from the main program} TESTCOMMON:=X+B+C+D END B=4; C=5; D=6 G=TESTCOMMON(3)$COMMON should only be used with functions, procedures, and modules appearing in the Equations window. It should not be used with library functions. Problems with calculation order can order if variables that are not set to constants are used in $COMMON.$COMPLEX On/Off i/j Directive EES provides an option in the Complex tab of the Preferences dialog to enable or disable complex algebra. The $COMPLEX On or Off directive provides a means of setting the option for complex numbers in the Equations Window. The directive also optionally allows whether i or j is to be used to represent the square root of -1. Subprograms can be configured to operate with complex variables by placing a$COMPLEX ON directive within the text of the Subprogram. The real and imaginary parts of complex variables that are passed to the Subprogram must be passed as separate parameters. $CONSTANT Name# = ValueSI [UnitsSI] ValueEng [UnitsEng] The$CONSTANT directive allows the specification of a constant. A constant is similar in some respects to an EES variable in that it has a value and units, but its value cannot be changed. In addition, it is a global (rather than a local) variable in the respect that all EES functions, procedures, subprograms, modules, as well as the main program have access to constants. A constant is recognized by EES by the last character in its name which must be the # character. Constants are normally specified in the Constants.txt file that is read in when EES is started. These constants are permanent constants that are available to all EES files. The difference between a constant that is defined in the Constants.txt file and one that is defined with the $CONSTANT directive is that the latter is only available to the EES file that it is 266 Advanced Features Chapter 7 defined within. It is, in this sense, a temporary constant. The$CONSTANT directive in no way changes the Constants.txt file. The format, shown above is as follows: Name# is the name of the constant. The $CONSTANT directive will allow a constant that has been previously defined in the Constants.txt file to be redefined, but you generally do not want to do this. ValueSI is a numerical value that will be the value of this constant when EES is configured to operate in SI units. ValueSI must be a numerical value and not an EES variable. UnitsSI is the units for the constant that will be used when EES is configured in SI units. Note that the units must be enclosed in square braces. The units specification is optional. ValueEng is a numerical value that will be the value of this constant when EES is configured to operate in English units. ValueEngI must be a numerical value and not an EES variable. If ValueEng is not provided, it is assumed that the constant has the same value in either unit system. UnitsEng is the units for the constant that will be used when EES is configured in English units. Note that the units must be enclosed in square braces. The units specification is optional. Multiple constants can be defined, but each requires a separate$CONSTANT directive. The $CONSTANT directive should appear before the constant is used, preferably at the very top of the EES file.$DOLAST and $ENDDOLAST Directives Equations that are placed between the$DOLAST and $ENDDOLAST directives are compiled and executed after all of the other calculations are completed. The capability to control the order in which equations are executed is seldom needed since EES automatically orders the equations to provide the most efficient calculation. However, EES attempts to compile all equations before the calculations begin. Some equations, such as those involving a Duplicate statement cannot be compiled unless the limits are known apriori. In some cases, information such as the limits can be calculated and then used in further calculations. The$DOLAST directive is useful in these situations. Another applications of the $DOLAST directive would be to set the limits of an Integral function or to control calculation order with Functions that are using$COMMON. Note that each $DOLAST directive must be matched with a$ENDDOLAST directive. More than one set of these directives can be used but they cannot be nested within each other. $DOLAST directives can only be used within the main program, i.e., not within Modules or Subprograms.$EXPORT Directive The $Export directive provides a simple way of writing selected variables to an ASCII file. Numerical or string constants may also be include with the variables that are written to a file. 267 Chapter 7 Advanced Features This file can then be read by the Open Lookup Table command in EES or by another application, such as a spreadsheet program. If the filename extension is .CSV (commaseparated values), the data will be written as a CSV ASCII text file that is easily recognized by spreadsheet applications. In this format, each value is separated by a list separator character. If the filename extension is .TXT, EES will assume that the data should be written with header information in the EES Lookup file format that can be read directly by the Open Lookup Table command. The header information will include the name of the variable, its units, and its display format. The format of the$Export Directive is $Export /A /T /C /Q 'FileName', Var1, Var2, X[1..5], ... The /A is optional. If present, it indicates that the values should be appended to the existing file, if it exits. The /T is optional. Normally, results are exported for each run in the Parametric table. If the /T is present, only the results for the last run in the Parametric table will be exported. This option is ignored if the calculations do not involve the Parametric table. The /C is optional. If present, the file (or clipboard) is cleared before exporting. The /Q is optional. If present, the single quotes that normally surround string information will not be included. FileName can be either a string constant (within single quotes) or a string variable containing the name of the file that the values will be written to. If filename is specified to be 'CLIPBOARD', the output will be placed as delimited text on the clipboard. A maximum of 32760 characters can be written to the clipboard. Filename can have a .DAT and .TAB filename extension, in addition to the existing .CSV and .TXT options. .DAT files separate values with one space and .TAB files separate value with a tab character. Var1, Var2, X[1..5] represent variables that are used in the main section (not in a Module) of your EES program. Note that array range notation is supported. The$Export directive can be placed anywhere in the Equations Window. Multiple $Export directives are permitted, and they will be evaluated in the order that they occur in the Equations Window. The format of the numerical value for each variable in the$EXPORT statement can be followed with a format specification that controls how it is written to the file. Appending :A (e.g., Var1:A) causes the value to appear in the same format as seen in the Solution window,. :Fn and :En format for fixed decimal or exponential format with n digits where n is an integer between 0 and 9. The Lookup command can be used to write (as well as read) values in the Lookup Table. Saving the Lookup table as a .CSV file also provides export capability, but the $Export directive is much more convenient.$EXPORT directives can be placed in Subprograms or in Functions. The designated variables in the Function or Subprogram will be exported to the specified file after calculations are completed. Example: T$='C:\temp\junk.csv' 268 Advanced Features Chapter 7 A=5 B=A^2 C=A^3$Export T$A,B,C After solving, file C:\temp\junk.csv will be written with the values 5.00000000E+00,2.50000000E+01,1.25000000E+02$HIDEWINDOW Directive $HIDEWINDOW Windowname hides the specified window where Windowname can be any of the following keywords: Equations Formatted Plot Diagram Solution Arrays Parametric Lookup Residuals Integral Report$IF/IFNOT Directives The $IF and$IFNOT directives allow conditional exclusion of EES equations that are entered in the Equations window. The format of these directives is $IF Condition ... ...$ELSE ... ... $ENDIF These directives test the condition that follows the$IF/IFNOT keyword during equation compilation. The OR keyword can be used to accept a second condition. If the condition is true (for the $IF directive) or not true (for the$IFNOT directive), the equations that follow the $IF/IFNOT directive up to the$ELSE (if present) or the $ENDIF keyword are compiled and included with other equations in the EES Equations window. If the condition is false, the equations are ignored. Multiple$IF/IFNOT directives can be used and they may be nested. Recognized condition keywords are: INTEGRALTABLE This condition is true if a $INTEGRALTABLE directive appears in the EES file. The$INTEGRALTABLE directive can appear above or below this conditional test as EES will initiate a 2-pass compilation if a test for the existence of an Integral Table is required. DIAGRAMWINDOW 269 Chapter 7 Advanced Features This condition is true if the main Diagram Window is displayed on the screen. In this case, any input variables that are defined in the Diagram Window will be used while compiling the equations. If the Diagram Window is hidden (by selecting the close button at the upper right corner of the window), any input variables defined in the Diagram window are ignored and the DIAGRAMWINDOW condition is false. MACRO This condition is true if calculations have been initiated with the Run or Play Macro commands. MIN/MAX This condition is true if calculations have been initiated with the Min/Max command. MIN/MAXTABLE This condition is true if calculations have been initiated with the Min/Max Table command. MIN/MAXTABLE='Table Name' This condition is true if calculations have been initiated with the Min/Max Table command operating on the Parametric table named ‘Table Name’ which must be a string constant enclosed within single quotes. String variable names are not accepted. PARAMETRICTABLE This condition returns true if calculations have been initiated with the Solve Table, Min/Max Table or Uncertainty Propagation Table commands. It otherwise returns false. PARAMETRICTABLE='Table Name' The condition returns true if calculations initiated with the Solve Table, Min/Max Table or Uncertainty Propagation Table commands are applied to the Parametric Table named 'Table Name'. The table name should be a string constant enclosed in single quotes. String variable names are not accepted. TABLERUN# = Value or TABLERUN# < Value or TABLERUN# > Value The condition returns true if calculations are initiated with the Solve Table, Min/Max Table or Uncertainty Propagation Table commands and the run (or row) in the Parametric Table that is currently being solved is equal to Value. Value must be an integer number. When this directive is used, EES must recompile the equations in the Equations window after every run in the Parametric Table, so the calculation speed is reduced. UNITSYSTEM('XX') 'XX' can be any of the following unit specifications: 'SI', 'Eng', 'Mass', 'Molar', 'Deg', 'Rad', 'kPa', 'bar', 'psia', 'atm', 'C', 'K', 'F', 'R', 'Pa', 'MPa', and 'KJ'. The UNITSYSTEM condition returns true if the unit specification provided as the argument with the UNITSYSTEM condition is selected in the Unit System dialog. StringVariable$='String constant' StringVariable$ is any EES string variable that is defined before the $IF directive. The string variable can be defined in the Equations window, Parametric Table or the Diagram window. The text to the right of the equal sign is a string constant. Single quotes around the string constant are optional. Upper and lower case letters are not distinguished when testing equivalence between a string variable and string constant. A dropdown list of 270 Advanced Features Chapter 7 strings is the most convenient means of setting a string variable in the Diagram window. A common use of this directive is to set variables that are used with the Solve command but not with the Solve Table command. UNCERTAINTY This condition is true if calculations have been initiated with the Uncertainty Propagation command. UNCERTAINTYTABLE This condition is true if calculations have been initiated with the Uncertainty Propagation Table command. UNCERTAINTYTABLE='Table Name' The condition returns true if calculations are initiated with the Uncertainty Propagation Table command are applied to the Parametric Table named 'Table Name'. The table name should be a string constant enclosed in single quotes. String variable names are not accepted. Examples:$IFNOT ParametricTable Row=1 {This equation is used only if a Parametric Table is not used} $endif x=Row^2$IF UNITSYSTEM('F') TR=(T-32)/1.8 {This equation converts the temperature from F to C} $ELSE TR=T$ENDIF X$='abc'$IF X$='abc y=3 {This equation is executed only if X$='abc'} $ELSE y=5 {This equation is executed if X$ is not equal to ‘abc’} $ENDIF$IMPORT Directive The $Import directive provides a simple way of reading selected variables from an ASCII file. The data could be provided from a file written using the$Export directive or from another application. The combination of $EXPORT and$IMPORT directives provides a convenient way to transfer information from one EES program to another. The format of the $IMPORT Directive is 271 Chapter 7 Advanced Features$Import FileName //skiplines=10 Var1, Var2, X[1..5], S$... FileName can be either a string constant (within single quotes) or a string variable (ending with a$) holding the name of the file that the values will be read from. If FileName is specified to be 'CLIPBOARD', the values of the variables will be read from the clipboard in text format. The //skiplines=n is optional. If provided, EES will skip n lines before reading the data. Var1, Var2, X[1..5] represent variables that are used in your EES program. Note that array range notation is supported as are string variables. The $IMPORT directive can be placed anywhere in the Equations Window. Multiple$IMPORT directives are permitted, and they will be evaluated in the order that they occur in the Equations Window. Example: File text.csv contains the following data: 1.2, 3.4 5 'string 1' 'string 2' 6 $IMPORT 'text.csv' X[1..3], A$, B$, C After solving, variables X[1], X[2], X[3], A$, B$, and C will be set to the values in the file.$INCLUDE Directive The $INCLUDE directive provides an automatic method for loading a library file or ASCII text file containing EES equations. The format is:$INCLUDE FILENAME FILENAME is the filename including the filename extension which can be one of .TXT, .LIB, .FDL, .DLF, .DLP, or .PRF. The filename should also include the complete path name, e.g., C:\EES32\myDefn.TXT. However, if a path name is not provided, EES will look in the current directory. If EES is unable to find the file, it will provide the opportunity to browse so that you can locate it. The $INCLUDE statement must be on a line by itself, starting in column 1. It is best to place the$INCLUDE directives at the top of the Equations Window to ensure that the directive is processed before compilation of the equations is initiated. .TXT Files If the filename extension is .TXT, EES expects FILENAME.TXT to be an ASCII text file containing EES equations. Syntax errors can not be identified in the library file so care should be taken to ensure the equations are correct before saving the library file. EES will include these equations with others in the Equations window during compilation. However, the equations and the variables associated with these equations will be hidden. Nested use of the $INCLUDE directive is not supported; the text file must not include$INCLUDE statements. 272 Advanced Features Chapter 7 Equations can also be entered from a file with the Merge command in the File menu. The difference between the Merge command and the $INCLUDE directive is that equations entered with the Merge command are placed directly into the Equations window as if they were typed and they remain visible. The text entered with the$INCLUDE directive will be hidden. Note that the speed of editing in the Equations window is reduced as the size of the text in the Equations window increases. Use of the $INCLUDE directive for very large problems can eliminate this problem on slower machines. Library Files If the filename extension is .LIB, .FDL, .DLF, or .DLP, EES will expect the file to be a library file of a type corresponding to the filename extension. EES internal functions, procedures. and modules are recognized with the .LIB extension, whereas external functions use a .DLF extension and external procedures use either the .FDL or .DLP extension. EES will automatically load the referenced library file if it is not already loaded. Note that library files can also be loaded automatically when EES is started by placing them in the USERLIB subdirectory or by applying the Load Library command. Help files having the same name as the library file and a filename extension of .HLP or .HTM will also be loaded automatically. Preference Files (.PRF) A specified user preferences file will be automatically loaded.$INTEGRALAUTOSTEP Directive $IntegralAutoStep provides an alternative to selecting the integration auto step size parameters from the Preferences dialog. The$IntegralAutoStep directive is processed when the equations are compiled and the specifications made with the directive will override any previous settings. The format of the $IntegralAutoStep directive is$IntegralAutoStep Fixed=250 Richardson=Off or $IntegralAutoStep Vary=1 Min=50 Max=2000 Reduce=1e-3 Increase=1e-5 Integration with automatic step size is assumed when the equation-based Integral command does not include a step size or when the specified step size is zero. In either case the step size will be chosen so as to provide a fixed number of steps or according to an automatic step-size adjustment algorithm. The first form of the$IntegralAutoStep shown above specifies the fixed number of number of steps and optionally allows the Richardson extrapolation to be turned on or off. The second form of the $IntegralAutoStep directive instructs EES to use an automatic step size adjustment algorithm that is applied every N steps where N is the number specified with the Vary keyword. The minimum and maximum number of steps can be specified with the Min and Max keywords. The step size is reduced if the relative error tolerance increased above the 273 Chapter 7 Advanced Features value provided with the Reduce keyword. The step size is increased when the relative error falls below the value provided by the Increase keyword. All of the keywords, with the exception of the Vary keyword are optional. Note that parameters must be provided with numerical constants. EES variables cannot be used to provide the integration parameter values.$INTEGRALTABLE Directive The $IntegralTable directive is used in conjunction with the equation-based Integral function. The equation-based Integral function does not employ the Parametric table to specify the values of the integration variable, as does the table-based Integral function. Rather, the lower and upper limits and optionally, the step size of the integration variable is specified as arguments within the Integral function, e.g., F = INTEGRAL(Integrand, VarName, LowerLimit, UpperLimit, StepSize) Normally, EES does not keep intermediate values of any variable used during the numerical integration. Such information is needed if you with to know the trajectory or path of variables as well as their values at a specified time. The$IntegralTable directive instructs EES to store the intermediate values in an Integral Table. The values can then can be plotted, printed, or copied to another application. The format of the $IntegralTable directive is:$IntegralTable t:0.1, x,y,z where t is the integration variable. It of course can have any legal EES variable name. t is used here as an example. This variable must appear in one or more equation-based Integral functions within the Equations window. The first column in the Integral Table will hold values of this variable. The colon and number (or variable name) following the integration variable are optional. If a number is supplied, this number will be taken to be the output step size and integration variables will be reported in the Integral Table at the specified step size. The step size may be a variable name, rather than a number, provided that the variable has been set to a constant value preceding the $IntegralTable directive. If a step size is not specified, EES will output results for each calculation set. In this case, the step size may vary from row to row in the table if automatic step size is used. Note that the step size used to report integration results is totally independent of the step size of used in the numerical integration. If the numerical integration step size and output step size are not factors, linear regression will be used to determine the integrated quantities at the specified steps. x, y, z ... are variables in the EES program. Algebraic equations involving variables are not accepted. A separate column will be created in the Integral Table for each specified variable. Array range notation, e.g., X[1..5] can be used. The variables must be separated by a space or list delimiter (comma or semicolon) 274 Advanced Features Chapter 7 When calculations are initiated, EES will first check to ensure that all variables in the$IntegralTable command are used in the equations. If no errors are found, an Integral Table will be created and filled with intermediate values results from the numerical integration. Values from this table can then be plotted, printed, and copied, in exactly the same manner as for other tables. When the $IntegralTable directive is used with the Solve Table command, an Integral Table is produced for each run (i.e., row) of the Parametric Table. Only one Integral Table can be viewed at one time. The run number control in the upper left cell of the Integral Table indicates the Parametric Table run number for which data are currently displayed. This run number may be changed by clicking on the up/down arrows or by directly entering the run number. The data in the table will be automatically updated when the run number is changed. Starting in version 7.110, the Integral Table is saved with when the EES file is saved. If an Integral Table exists when calculations are initiated, it will be deleted if a new Integral Table is created.$LOCALVARIABLES On/Off Directive $LOCALVARIABLES ON/OFF controls whether the values of local variables used in Functions, Procedures, Modules and Subprograms will be displayed in the Solution and Residuals windows. If ON, the local values of all Functions, Procedures, Modules, and Subprograms that appear in the Equations window will be displayed in the Solution window. (Functions, Procedures, Modules and/or Subprograms that have been loaded from a library file will not be displayed.) This directive overrides the Show function/procedure/module value setting in the Options tab of the Preferences dialog. EES only changes the first 5 letters of the keyword, so it is acceptable to use$LOCAL ON/OFF. $OPENLOOKUP Directive The$OPENLOOKUP directive (available in the Professional version) opens a file having the specified name and reads that file into the Lookup Table. The file can have .CSV, .TXT or .LKT Lookup file format. The filename should include the filename extension. The filename may be a string constant (enclosed within single quotes) or a string variable that has been previously assigned to the filename, as in the following examples. $OPENLOOKUP 'C:\EES32\myTable.lkt'$OPENLOOKUP FILE${File$ has been previously set to a valid lookup file name} $OPENLOOKUP ? {Bring up a dialog window to choose the lookup file}$OPENLOOKUP ?.csv {Bring up a dialog window showing only .csv files} When EES encounters this directive, it will first check to see if it has already opened a Lookup table with this filename. If the Lookup table has already been opened and the time/date information for the disk file has not changed, no action will be taken. 275 Chapter 7 Advanced Features If a single question mark (?) is provided as a file name, EES will present a Windows open file dialog and use then substitute the selected file name for the ? after opening the file. If two question marks are provided, EES will open the selected file, but not make the substitution so that the open file dialog is presented during every execution. The $OPENLOOKUP directive can have an optional second parameter which must be a string variable name. The name of the Lookup file that is opened is assigned to this variable. For example:$OpenLookup ?? myLookupFile$will bring up a standard file input dialog from which the file name can be selected. That Lookup file will be opened and copied into the Lookup Table and the string variable myLookupFile$ will be set to the name of the file. The /FORMAT specification is optional. If present, EES will look for the specified format file with a .fmt filename specification and it will read the Lookup file according to the format specification. The /RENAME specification is optional. Normally, EES will associate the name on the tab of the Lookup window with the name of the file. However the /RENAME specification provides the option to change the table name as desired using either a string constant or predefined string variable. $PRIVATE Directive Library files can contain EES Functions, Procedures, Modules and/or Subprograms. These library files can be loaded manually with the Load Library command or automatically by placing the library file in the USERLIB folder. The name of each Function, Procedure, Module, and Subprogram in the loaded library files can normally be seen with the Function Information dialog by selecting the EES library routines radio button. Help information, if available, can be accessed for the routine and the EES code can be viewed. However, in some cases, you do not want a routine to be displayed in the Function Information listing. It may be intended for private use or to only support other routines or perhaps you just don't want others to view the code. Including the$PRIVATE directive will remove the routine from the Function Info display. $REAL Directive The$REAL X, Y, Z directive indicates to EES that the variables that follow (e.g., X, Y, Z) are to be considered to be real i.e., their imaginary component is zero. This directive is only useful when operating in the complex mode with a Parametric table. In this case, EES will not require both the real and imaginary components of the variable to be set in the table. The $REAL 276 Advanced Features Chapter 7 command should be placed at the top of the Equations window directly following the$Complex ON directive. The variables can be separated by a space or a list separator. $REFERENCE Directive The$REFERENCE directive allows the default reference state for a specified fluid to be changed. The format for this directive is $REFERENCE Fluid ReferenceID where Fluid is the name of the fluid, e.g., R134a. ReferenceID is one of the following: DFT the reference is reset to the default value. See the fluid property information for the specified fluid to determine the default reference state NBP the values of specific enthalpy and specific entropy are each set to 0 for saturated liquid at the normal boiling point. Note that this option is not applicable to fluids for which the critical pressure is less than one atmosphere. In this case, the reference will be reset to the default value. ASH the values of specific enthalpy and specific entropy are each set to 0 for saturated liquid at -40°C (-40°F). This is the ASHRAE standard reference. Note that this option is not applicable to fluids for which the critical temperature is less than -40°C. In this case, the reference will be reset to the default value. IIR - the value of specific enthalpy is set to 200 kJ/kg and the value of specific entropy is set to 1.0 kJ/kg-K for saturated liquid at 0°C (273.15 K). This is the standard reference state for the International Institute of Referigeration. Note that this option is not applicable to fluids for which the critical temperature is less than 0°C. In this case, the reference will be reset to the default value.$REQUIREDOUTPUTS Directive The $REQUIREDOUTPUTS allows the number of outputs in the Call statement for a Procedure to be less than the number of outputs in the Procedure header statement. This directive must be placed after the Procedure statement but before the END statement for that procedure. If this directive appears in other places or if it indicates that more outputs are required than in the Procedure header statement, it will be ignored. This directive is most useful for library files.$SAVELOOKUP Directive The $SAVELOOKUP directive will save a specified Lookup table into a disk file after calculations are completed. The format is:$SAVELOOKUP LookupTableName 'C:\EES32\myTable.lkt' 277 Chapter 7 Advanced Features LookupTableName is the name of the Lookup Table (as seen on the tabs in the Lookup Table Window) that is to be saved. LookupTableName can be a string constant contained in single quotes or a string variable (identified with a $as its last character). The last parameter is the name of the file. This name must be a string constant, a string variable that has been set to a valid file name or a ? or ??. If a ? is provided, EES will display a standard save file dialog from which the name of the file can be selected. That file name will then overwrite the ? so that the save file dialog does not reappear. For example,$SAVELOOKUP 'LookupTableName' ? will save the data in the lookup table name 'LookupTableName' into a file that is selected from the save file dialog. The ? will be overwritten with the selected filename. If ?? is provided, it will not be overwritten and the save file dialog will appear after every calculation. Lookup tables are automatically saved and opened when an EES file is saved and opened. It is not necessary to use the $OPENLOOKUP and$SAVELOOKUP directives for this purpose. The directives are useful for chaining EES programs, i.e., when the an EES program writes information into the Lookup Table using the Lookup command in a function or procedure so that a following EES program can use that information. The Lookup command can be used to save calculated results in the Lookup Table. Several EES programs can be chained in sequential operation by saving the Lookup table as a Lookup file in one EES program and loading that Lookup file in the next EES program. Link buttons on the Diagram window facilitate the chaining process. $SAVETABLE The$SAVETABLE directive allows an automatic way to save any table to a .LKT, .CSV or .TXT file. Options are provided to save the column header information, save in EES format, append to existing file, and transpose rows and columns. The $SAVELOOKUP provides many of the same capabilities, but only for Lookup Tables. The$SAVETABLE directive can be used for any table. Optional parameters are as follows: These parameters are not applicable for .LKT files. /A append to existing file. /E save in EES format so that the file can be read directly by the EES Open Lookup Table command (applicable only for .TXT files) /F Normally, results are exported for each run in the Parametric table. If the /F is present, only the results for the last run in the Parametric table will be exported. This option is ignored if the calculations do not involve the Parametric table. /N include column name and unit information /T transpose rows and columns (can not be used with /E option) /Q do not surround strings with single quotes 278 Advanced Features Chapter 7 $STOPCRITERIA The$STOPCRITERIA directive provides an alternative way to set the stop criteria that control the results of iterative calculations. The format of the $StopCriteria directive is:$StopCriteria Iterations=200 Residuals=1e-5 Variables =1e-9 Time=3000 Note that it is not necessary to enter all four parameters and that they can be entered in any order. $SHOWWINDOW WindowName1 WindowName2 After EES successfully solves, it displays a window with calculated results. By default, the Solution window is brought to the front after the Solve, Min/Max or Uncertainty Propagation commands are completed provided that the calculations were not initiated with a Calculate button in the Diagram Window. The Solve Table, Min/Max Table and Uncertainty Propagation Table commands display the Parametric table after the calculations are completed. In some cases, it would be better to display a different window, e.g., the Arrays Window or the Diagram Window. The$ShowWindow directive provides the capability to display a selected window after calculations are successfully completed. WindowName1 can be any of the following: Equations Parametric Formatted Lookup Plot Residuals Diagram Integral Solution Report Arrays None If WindowName1 is Solution, Plot, Parametric, or Lookup, then WindowName2 can be the name of any of the tabs that appear in the window. $SUMROW On/Off Directive EES provides an option in the Preferences dialog to display a sum row in the Parametric table. This option and other preferences are not saved with a EES program but rather with the user preferences. In some situations, it is desirable for the EES program to control whether the sum row is to be used. This can be done simply with a$SUMROW On or $SUMROW off directive which in the Equations window.$TABSTOPS Directive $TABSTOPS sets one to ten tab stops that are used in the Equations window. The format of this directive is$TABSTOPS TabStop1 TabStop2 ... TabStop5 Units where TabStop1 through 5 must be numerical values, separated by one or more spaces or list delimeters. The tab stop values should be entered in increasing numerical order. Units must be 279 Chapter 7 Advanced Features either in or cm. If no units are specified, in is assumed if the Unit System is set to English units and cm is assumed for SI units. Example: $TABSTOPS 0.5 2 3 in will set the tabstops at 0.5, 2 and 3 inches. Tabstops can also be set in the Equations tab of the Preferences dialog. However, if a$TABSTOPS directive appears in the Equations window, the setting made with this directive override the default settings appearing in the Preferences dialog. $TABWIDTH Directive$TABWIDTH provides exactly the same capability as the $TABSTOPS directive.$TRACE Directive $TRACE allows the values of selected variables to be recorded during the process in which the equations are iteratively solved. The format is$Trace x, y, z where x, y, and z are variables for which an iteration to iteration trace is needed. $UNITSYSTEM Directive The unit system is needed only when the built-in thermophysical (e.g., enthalpy) or trigonometric (e.g., sine) functions are used. Normally, the unit system is specified with the Unit System menu command. However, the unit system can also be specified with the$UnitSystem directive which has the following format: $UnitSystem SI[or ENG] MASS[or MOLE] DEG[or RAD] KPA[or PSIA] BAR[or ATM] C[or F] K[or R] The unit specifications can be made in any order and only those which are to be changed need to be provided. Note it is not possible to specify a mixed unit system. That is, if the unit system is SI, specifying F for the temperature will result in temperature units of C, not F. Similarly specifying psia for pressure will result in pressure units of kPa. Since the unit system specifications are saved with an EES file, there is no need to provide a$UnitSystem directive in an EES file. However, the unit system is not saved with text files that may be read into EES, possibly under the control of a macro command file. In this case, the $UnitSystem directive may be need to ensure that the unit system is configured as needed.$WARNINGS On/Off Directive EES provides an option in the Preferences dialog to display warning, should any occur. The warnings could be generated by a property correlation if is used beyond its range of applicability or by the user with the WARNING procedure. However, the option to display 280 Advanced Features Chapter 7 warnings and other preferences are not saved with the EES program but rather with the user preferences. In some situations, it is necessary to ensure that the warnings are set properly for a particular EES program to function properly. For example, EES approximates the subcooled properties of many fluids by assuming them to be incompressible. Ordinarily this approximation provides excellent results, but EES will issue a warning in any case if the Show Warnings option is selected in the Preferences dialog. To overide this setting, place the $Warnings Off directive in the Equations Window. 281 Chapter 7 Advanced Features Creating and Using Macro Files (Professional Version) A macro is a set of instructions to EES that are read from an ASCII file or from the EES Macro window. The filename extension for a macro file is .emf, which signifies EES Macro File. The instructions allow EES to open a file, solve the equations, create and solve a table, store calculated results in a file, print, and many other functions. In fact, many of the capabilities provided with the menu commands in EES can be implemented with a macro instruction. EES variables can be assigned a value in a macro files. For example, the Macro command, X$='GUESS' sets the string variable X$just as it would if this statement appeared in the Equations window. EES can directly communicate with Microsoft WORD with the WORD macro commands. Using the macro file capability, EES can be run from the Windows command line or it can be controlled from another program, either by running EES with the macro file name or by dynamic data exchange (DDE) with the calling program. To run an EES macro from the command line or from another application, the macro file name is placed after the EES executable file name. For example, to start EES and have it run the commands in file myMac.emf stored in the C:\EES32 directory, you would enter: C:\EES32\EES.EXE C:\EES32\myMac.emf If EES is launched from the command line with the /NOSPLASH parameter, the splash screen will be skipped, as in the following example: C:\EES32\EES.exe C:\EES32\HELLO.ees /NOSPLASH The .emf filename extension is required. Otherwise EES will consider the file to be a normal EES file. When EES is started with this command, it will remain hidden while it opens the macro file and executes each of the instructions in that file. Provided that no errors are encountered, all of the instructions will be executed in the order in which they appear and then EES will quit. EES writes an ASCII log file called EESMacro.LOG that indicates what instructions it has completed and any error messages. This log file is placed in the same directory as the EES executable. Creating an EES Macro File The easiest way to create an EES Macro file is to use the Build Macro command in the File menu. After selecting this command, EES will prompt the user to provide a name for the macro file. Then a small macro file window will appear at the bottom of the screen. If the filename you provided already exists, it will be read into macro file window. Otherwise it will be blank. Now as you select commands form the EES menus, the macro equivalents of the 282 Advanced Features Chapter 7 commands will be automatically entered into the macro file window. For example, when you apply the Open command, EES will add a line to the window of the form. Note the control buttons at the right of the EES Macro window. The top row provides capability to play, pause or stop the macro execution. The bottom row of buttons saves the macro file, locks/unlocks the macro file window, and displays help for macro commands. The macro command window is editable, so that you can modify the commands that appear in this window or delete them if you wish. Most of the EES menu commands will produce a macro instruction. Some commands, such as those in the Windows menu, are not applicable for a macro file since EES is usually not visible while running the macro commands. The Build Macro command name is changed to Close Macro after you open a macro command window. When you are done entering instructions, select the Close Macro command to close the macro file. The major purpose of the macro capability is to allow an external program to use the EES solving engine. Using the macro file, EES can be instructed to open an existing EES or .TXT file and solve the equations in that file. EES macro files provide instructions to save the contents of the Solution and Parametric Table windows so that the solution can be returned to the program that called EES. See the EXCEL_EES.xls file for an example on how Microsoft EXCEL can call EES. Running an EES Macro File by Dynamic Data Exchange The easiest way to run an EES macro file from another application is to simply start EES and provide the macro file name (with an .EMF filename extension) as a parameter on the command line. However, the disadvantage of this method is that EES quits when the macro file commands have been executed. If it is necessary to call EES repeatedly, this method becomes very inefficient as EES must be repeatedly loaded into memory. An alternative approach is to use dynamic data exchange (DDE) messages. EES must be running to receive a DDE message. This is not really a problem as EES can be started from a remote application using the Windows CreateProcess command. However, when EES starts, it normally displays its splash screen and waits for the user to click the OK button. To avoid having EES display the splash screen and wait for user input, supply /HIDE as a parameter on the command line, i.e., start EES with the following command. 283 Chapter 7 Advanced Features C:\EES32\EES.EXE /HIDE After receiving this command EES will start in a minimized mode. Its icon will be visible in the Windows task bar, but the program will otherwise not be visible on the screen. The calling program must next send EES a series of messages according to the DDE message protocol. The first message that must be sent is the wm_DDE_initiate message. This message is normally sent using the Windows SendMessage command. The SendMessage command requires four parameters. The first should be a broadcast message to all running applications. The second must be wm_DDE_initiate. The third is the handle of the calling application. EES will use this handle to send message back to the calling application. The final parameter is a global atom referring to 'EES', so that EES knows to act on this initiate message. Shown below is a code fragment in Delphi 4 that sends the wm_DDE_initiate message to EES. procedure TForm1.doInitiate(Sender: TObject); var theApp, theTopic:Atom; lParam:longInt; begin theApp:=GlobalAddAtom('EES'); theTopic:=GlobalAddAtom(''); lParam:=MakeLong(theApp,theTopic); SendMessage(HWND(-1),wm_DDE_Initiate,Handle,lParam); GlobalDeleteAtom(theApp); GlobalDeleteAtom(theTopic); end; EES will respond to the wm_DDE_Initiate message by sending the application a wm_DDE_ack message. Included in this message is the handle to the EES application, here called EESWindowHandle, that the calling program must provide in following messages. A code segment that receives the wm_DDE_Ack message may appear as shown below. procedure TForm1.GetACK(var theMessage:TMessage); var AppName,TopicName:charString; S:shortString; begin EESWindowHandle:=theMessage.wParam; end; After the wm_DDE_initiate message has been received by EES, the calling application can next send a wm_DDE_Request message to play a macro. The information sent to EES includes a global atom referring to the string 'PLAY' and a character string containing the DOS 284 Advanced Features Chapter 7 filename of the macro file. The complete file name should be sent, including the directory information and the .EMF filename extension. The code fragment below shows how this is done. procedure TForm1.PlayMacro(Sender: TObject); var cfile,command:atom; lParam:longint; CSTR:charString; begin StrCopy(CStr,'c:\ees32\myMacro.emf'); cfile:=GlobalAddAtom(CStr); Command:=GlobalAddAtom('PLAY'); lParam:=MakeLong(cfile,Command); PostMessage(EESWindowHandle,wm_DDE_REQUEST,Handle,lParam); end; After receiving this message, EES will open the macro file and execute the instructions therein. It will then post a WM_DDE_ACK message to inform the calling program that the calculations are completed. When EES executes a macro file, it writes results to a specified text file. The calling application can open this text file to retrieve the results. The only other message EES will accept is the quit command which terminates EES. Here's how it can be sent. procedure TForm1.QuitClick(Sender: TObject); var cformat,command:atom; lParam:longint; begin cformat:=GlobalAddAtom(''); Command:=GlobalAddAtom('QUIT'); lParam:=MakeLong(cformat,Command); PostMessage(EESWindowHandle,wm_DDE_REQUEST,Handle,lParam); end; EES Variable Assignment in a Macro EESVariable = value or expression //Assign an EES variable to a value or to an expression involving previously defined variables. The variable remains assigned to this value until it is reassigned. A variable assigned with a macro command cannot be reassigned in the Equations window. Note that // signifies the start of a comment. Comments can be placed anywhere in the macro file. 285 Chapter 7 Macro Command List Advanced Features Macro commands can be entered in the Macro Command List window accessed from the Open or Create Macro item in the File Menu. Multiple commands can be entered on a single line if separated by a line break character (;) AlterValues 'Table 1' P2 Rows=1..10 First=100 Last=550 {Enter values into the Parametric Table named 'Table 1' for the column holding variable P2 setting the values of rows 1 to 10 to values starting at 100 and ending at 550. You can specify Inc=50 instead of providing Last=550. Row numbers can be specified with predefined variables.} Beep 3 {Execution of this command will result in an audible sound. An integer between 1 and 5 can optionally follow the beep keyword. If the integer is present, EES will play the specified sound defined in the Sound tab of the Preferences dialog. Otherwise it will just sound the default beep.} Check {Check the equations. A summary statement is not issued. This command is useful only in rare situations in which it is necessary to have EES review the existing equations before processing following Macro commands.} Copy ArraysTable R1 C1:R10 C4 {Copy the specified range of the Arrays table to the clipboard. If no range is provided, the entire table is copied} Copy IntegralTable R1 C1:R10 C4 {Copy the specified range of the Integral table to the clipboard. If no range is provided, the entire table is copied} Copy EquationWindow L3 C1:L5 C9 {Copy the characters in the Equations Window starting with character 1 on line 3 through character 9 on line 5} Copy LookupTable 'Lookup 1' R1 C1:R10 C4 {Copy the specified range of the Lookup table with name 'Lookup 1' to the clipboard. If no range is provided, the entire table is copied} Copy ParametricTable 'Table 1' R1 C1:R10 C4 {Copy the specified range of the Parametric table named 'Table 1' to the clipboard. If no range is provided, the entire table is copied} Copy PlotWindow 3 {Copies the graphics in Plot Window 3} Copy SolutionWindow {Copies the entire contents of the Solution window in ASCII format} 286 Advanced Features Chapter 7 Delete 'FileName' {Delete the specified file. FileName can be a string variable (ending with character$) or a filename enclosed in single quotes} DeleteLookup 'TableName' or DeleteLookup 1 {Delete the specified Lookup table. The Lookup table can be indicated by: 1) providing its name (optionally surrounded in single quotes), 2) providing a string variable that contains the name of the table or 3) by providing a number indicating the position of the table. The first table is number 1.} GOTO 10 //Transfer execution of the next macro command to the line having label 10. Labels must be numerical values ranging between 1 and 30000 followed by a color (:). Labels will usually ge used with the IF THEN ELSE command, e.g., IF (X<Y) then GOTO 10 DeletePlot 1 {Delete Plot Window 1.} Export /A 'FileName' X,Y,Z {Export opens the specified file and writes the values of the specified EES variables to that file. Filename can be Clipboard. This command has the same format and options as the $EXPORT directive. For example, the optional /A option appends the specified data to the existing file.} GetDirectory {F$=GetDirectory will assign the specified string variable (F$in this case) to the current Windows directory.} If (X<=Y) then Z=3 else Z=4 {The If THEN ELSE command in a macro file can test variables that have been defined in the macro or set in the previous execution of the Solve command. The tests can use any of the following logic operators: <, <=, =, <>, >, >= The entire command must be all on one line. The ELSE clause is optional. The IF command will usually be used with the GOTO command and line labels.} Import 'FileName' X,Y,Z {Import opens the specified file and reads the values of the specified EES variables from that file. Filename can be Clipboard. This command has the same format and options as the$IMPORT directive.} InsertLookupColumn 'TableName' After 'ColumnName\Units' ColumnFormat {Inserts one column into the existing Lookup table that has name (showing on the tab in the window) TableName. TableName may be a string variable containing the name of the table. The column is inserted after column number After, where After is an integer. If After is 0, the column will be inserted as the first column in the table. If After is greater than the number of columns in the table, the column will be inserted as the last column in the table. 'ColumnName\Units' is optional. If 'ColumnName\Units' is provided, the column name will be set to "ColumnName' and its units will be set to Units. 'ColumnName\Units' may be a string variable. Note that a \ separates the column name and the units. If a \ is not 287 Chapter 7 Advanced Features provided, the units will be left blank. ColumnFormat is optional. If this field is provided, the 'ColumnName\Units' field must also be provided. ColumnFormat is a 2 digit field. The first digit can be A (auto), F (fixed decimal), E (float decimal) or S (string). The second digit is a number between 0 and 9.} InsertLookupRows 'TableName' After NRows {Inserts NRows into the existing Lookup table that has name (showing on the tab in the window) TableName. TableName may be a string variable containing the name of the table. If NRows is not provided, it is assumed to be 1. The row(s) are inserted after row number After, where After is an integer. If After is 0, the row will be inserted as the first row in the table. If After is greater than the number of rows in the table, the row will be inserted as the last row in the table. After and NRows may be variables defined in the macro or in the EES program.} Load #n {This command is useful only for macro files (.emf filename extension) that control the execution of a distributable file. The distributable file can contain up to 100 separate programs. This command will clear the memory space and then load program n where n is a number between 1 and the number of programs provided with the distributable program.} LoadLib C:\EES32\myLib.lib {Load a library file called C:\EES32\myLib.lib} Lookup['Lookup 1', 2,3]=10 {Set the value in row 2 column 3 of the Lookup table having name 'Lookup 1' to 10} Maximize G a,b,c {Maximize variable G with respect to variables a, b, and c. Note that the all variables must be defined in the Equations Windowand variables a, b, and c must have non-infinite lower and upper limits. Error checking is not provided.} Merge C:\EES32\Examples\Regen.ees /56 {Merge the specified file with the current contents of the Equations window after character position 56. If the /number is not provided the file will be merged to the bottom of the existing equations.} MessageDialog([OK, Cancel], 'message text') {MessageDialog will put up a user-provided message dialog with 1, 2 or 3 buttons. The button captions (which each should be less that 16 characters) are provided in brackets as the first parameter. For example, [OK, Cancel] will result in a message dialog with two buttons captioned OK and Cancel. The message text is the second parameter. The message text can reference a URL. For example, the message text could be 'Please visit http:\\fchart.com. Press the OK button when you return.' The URL name is hot so that clicking on it will start your browser and point it at the specified URL. Note that backslash \\ characters must be used because // is interpreted to 288 Advanced Features Chapter 7 be the start of a comment. The dialog will optionally return the button number (1, 2, or 3) if a variable name is provided in the following manner. R=MessageDialog([OK, Cancel], 'message text'). In this case R will be set to 1 if the OK button is selected and it will be set to 2 if the Cancel button is selected.} Minimize G a,b,c {Minimize variable G with respect to variables a, b, and c. Note that the all variables must be defined in the Equations Window and variables a, b, and c must have non-infinite lower and upper limits. Error checking is not provided.} ModifyAxis X Plot=1 Min=100 Max=600 Int=100 Linear Grids=on Showscale=off Size=10 Style=BoldItalic Format=A3 {Change the scaling of the X axis of plot window 1 to the specified minimum, maximum and interval in linear or log coordinates. The scale numbers are shown in bold italic with fontsize 10 using automatic format. The gridlines and scale can be turned on or off. Use Y for the left Y axis and Y2 for the right Y axis} ModifyPlot 1 Width=12 cm Height=15 cm {Change the size of plot rectangle for the specified plot window. If the plot window number is not provided, the command is applied to the foremost plot window. Size can be specified in cm or in} New {Clear the workspace and bring up an empty Equations window} NewLookup 'Lookup 1' Rows=24 Cols=2 {creates a new Lookup table having name 'Lookup 1' with 24 rows and 2 columns. The Lookup table name can be a previously defined string variable, e.g., L$} NewContourPlot Table=PAR1 X=x Y=y Z=z TYPE=Isometric LEGEND=YES RESOLUTION=25 XMIN=0 XMAX=1 XINT=0.1 ZINT=0.2 {creates a new contour plot in which contours of variable identified by Z are displayed in one of three ways as a function of variables identified by X and Y. The data used to construct the plot are taken from the specified table. The table can either be identified by its name within quotes or by specifying the identifier for the table (PAR, LOOK, ARR, INT, followed by the position of the table. For example, PAR1 designates the first parametric table. ARR designates the arrays table. The three types of plots are identified by keywords: Isometric, Colorbands, and Gradient. The Legend and Resolution are optional. If Legend is provided, it must be followed by =Yes or =No. Resolution must be followed (without spaces) by a equal sign and a number that is between 0 and 100. A default value is used if no resolution is provided. The limits and interval of the X, Y and Z plotting variables can optionally be specified, as shown in the above example. Note that only plots based on 3 columns of data are currently supported.} 289 Chapter 7 Advanced Features NewPlot Table=’myTable’ X=P2 Y=T2 Rows=1..10 Line=1 Symbol=1 SymbolSize=6 Color=Red Legend //Create a new plot window and Plot T2 vs P2 using the first 10 rows of data in the Parametric table named ‘myTable’. The Legend keyword causes a legend item to be created. Row numbers can be specified with pre-defined variables. NewTable 'Table 1' Rows=10 X Y Z Create a new Parametric table having name 'Table 1' with 10 rows and columns for variables X, Y and Z. The Parametric table name can be a previously defined string variable, e.g., T$} Open C:\EES32\Examples\Regen.ees {open the specified file} OpenLookup C:\EES32\myTable.lkt {open the specified Lookup file} If ? is provided in place of a file name, a select file dialog will appear in which the file name can be chosen. The filename extension can follow the ?, e.g., ?.csv and then the select file dialog will only display files having this file name extension. The table having this file name will then be opened. A string variable can be provided after the ?. If provided, the string variable is set to be the name of the Lookup file that has been read in. This name is valid for the remainder of the macro file execution. Example: OpenLookup ?.csv TableName$/FORMAT myFormat.fmt OverlayPlot 1 Table=’myTable’ X=P[4] Y=Eff Rows=1..10 Line=1 Symbol=4 SymbolSize=10 Color=Blue Right Legend //overlay a plot of Eff vs. P[4] from data in rows 1..10 of the Parametric table named myTable. Use the right Y-scale. Use plot symbol 4 with a size of 10 pixels. Allowable sizes range from 4 to 18. To plot other tables, use LookN for Tab N of the Lookup table, Arr for Arrays table or Int for Integral table. The Legend keyword causes a legend item to be created. Parametric['Table 1',1,4]=20 {Set the value in row 1 column 4 of the Parametric table named 'Table 1' to 20} Paste Lookup 'Lookup 1' R2 C3 {Paste the contents of the clipboard into the Lookup table named 'Lookup 1' starting at row 2 column 3.} Paste Parametric 'Table 1' R2 C3 {Paste the contents of the clipboard into the Parametric table named 'Table 1' starting at row 2 column 3.} Pause 2.5 {Pause execution for a specified number of seconds. This command is useful when the EES macro file is being cycled and EES is to periodically read a file that has been written to a disk by another application, such as a data acquisition program.} 290 Advanced Features Chapter 7 Print Diag Equ For Arr Par2 Look3 Plot1 {Print the Diagram, Equations, FormattedEqns, Arrays, the Parametric table in the second tab of the Parametric Table, the Lookup Table in the 3rd tab of the Lookup Table and Plot 1 windows} PrintSetup PRINTER='\\SEL\Sandy' Orientation=PORTRAIT Copies=1 {Set the printer specifications} PropPlot Steam TS 4 11000 5300 2100 660 6 0.074 0.94 3.37 12 45 155 DoQLines {Create a TS property plot for Steam. Include 4 constant pressure lines and 6 constant entropy lines at the specified values and draw lines of constant quality} PropPlot AirH2O PSY 6 10 15 20 25 30 35 4 0.8 0.85 0.9 095 P=101.3 {Create a Psychrometric chart with 6 wetbulb lines at values of 10, 15, 20, 35, 30, 35 C and 4 specific volume lines of 0.8, 0.85, 0.90, and 0.95 m3/kg at a total pressure of 101 kPa.} QUIT {Close the EES application} Repeat ...... Until (X-Y>5) {The commands in the macro file between the Repeat and Until keywords (which must be on separate lines) are repeated in sequence until the expression with the parentheses is true. Each command appears on a separate line. The parentheses are optional. Note that any legal expression involving existing variables that are defined in the main section of the Equations window can be used in the expression. If the expression is never true, the macro instructions will be repeated indefinitely or until the Esc key or Macro Window stop button is pressed. Reset a, b {Reset will reset the status of the list of variables that follow the Reset keyword (e.g., a and b) to unassigned. This command may be useful if a variable has previously been used in a macro command list and is now to be used in another manner in the same macro command list.} ResetGuesses {Reset the guess values of all variables to their default values} Run Program name and parameters {The Run command will start the indicated program with the given parameters, just as if this string were entered with the Run command in the Windows Start menu. For example, to start EXCEL enter: Run EXCEL You can start EXCEL and open the file C:\temp\TEST.xls with the following macro command: Run c:\temp\text.xls 291 Chapter 7 Advanced Features EES knows that the .xls filename extension is an EXCEL file. Using the Run command, it is possible to start external programs that read data exported by EES and then have EES import the data output by the program.} Save {Save the current file with its existing file name} {Save the contents of the Arrays table to a file called SaveArrays myArrays.txt myArrays.txt. SaveLookup 'Lookup 1' myTable.txt /A /T /N /E /Q {Save the contents of the Lookup table having the tab name 'Lookup 1' to a file called mytable.txt. The /A /E /F /N /T and /Q are optional parameters as explained below under SaveTable.} SaveSolution mySoln.txt /Append {Save the contents of the Solution window to an existing file called mySoln.txt. The /Append option will allow writing to the bottom of the file without deleting the existing information.} SaveTable 'Table 1' myTable.txt /A /T /N /E /Q {save the contents of the table named 'Table 1' in the Parametric Table Window to an existing file called myTable.txt. The /A /E /F /N /T and /Q are optional parameters. These parameters are not applicable for .LKT files. /A append to existing file. /E save in EES format so that the file can be read directly by the EES Open Lookup Table command (applicable only for.TXT files) /F Normally, results are exported for each run in the Parametric table. If the /F is present, only the results for the last run in the Parametric table will be exported. This option is ignored if the calculations do not involve the Parametric table. /N include column name and unit information /T transpose rows and columns (can not be used with /E option) /Q do not surround strings with single quotes} SetDirectory(F$) {SetDirectory(F$) will set the current Windows directory to the string constant or string variable within the parentheses.} ShowWindow Arrays ShowWindow Diagram ShowWindow Equations ShowWindow Format //Bring the Arrays table the front //Bring the Diagram window to the front //Bring the Equations window to the front //Bring the Formatted Equations window to the front 292 Advanced Features Chapter 7 ShowWindow Integrals //Bring the Integrals table the front ShowWindow Lookup 'Table Name' //Bring the Lookuptable to the front. The name of the Lookup table (surrounded with single quotes) can be optionally provided in which case the table having this name on its tab will be selected. ShowWindow Parametric 'Table Name' //Bring the Parametric table to the front. The name of the Parametric table (surrounded with single quotes) can be optionally provided in which case the table having this name on its tab will be selected. ShowWindow Plot 'Plot Name' //Bring the plot to the front. The name of the plot (surrounded with single quotes) can be optionally provided in which case the plot window having this name on its tab will be selected. ShowWindow Progress {Normally, a series of EES commands initiated from a macro command list will not show the Progress window. However, if the macro has been started from the Calculate button in the Diagram window, it may be desirable to show the Progress window to reassure the user that the calculations are proceeding in a long calculation. Including this macro command will ensure that the Progress window is visible.} ShowWindow Residuals ShowWindow Solution {Bring the Residuals window to the front} {ring the Solutions window to the front} ShowWindow Solution Key {ring the Solutions window to the front and show the Key Variables window if it exists.} Solve {Solve as if the Solve command has been issued} SolveTable 'Table 1' Rows=1..10 {Solve rows 1 through 10 of the Parametric Table having the name 'Table 1'. If no range is specified, all rows are solved. The start and stop row numbers may be specified with variables that have been previously defined, e.g., SolveTable 'Table 1' Rows=Start..Stop} StopCrit It=100 Time=3600 Res= 1.0E-0006 Var= 1.0E-0006 {Set the Stop Criteria properties as indicated} Uncertainty h, Q, T_s=A1, Vel=R0.01 {Initiate the Uncertainty Propagation calculations to determine the uncertainty in variables h and Q as a result of uncertainties in variables T_s and Vel. The uncertainty in variable T_s is 1 on an absolute (A) basis. The uncertainty in variable Vel is 0.01 of its current value (relative basis).} 293 Chapter 7 Advanced Features Units C kPa MASS DEG supported.} {Set the Units as indicated. Mixed units, e.g., C and psia, are not UpdateGuesses {Update the guess values of all variables to the last set of calculated values} VarInfo P2 Lower=200 Upper=500 Guess=300 {Set the lower bound, upper bound, and guess value for variable P as specified} WORD.FileNew {Start WORD and create a new empty document.} WORD.FileOpen('FileName'){Start WORD and open the specified Word file. It is necessary to provide the complete file name.} WORD.FileSaveAs('FileName') filename.} WORD.Hide {Save the current WORD document with the specified {Hide the open WORD document.} WORD.Insert('any text here') {Insert the text contained with single quotes into the WORD document at the current position.} WORD.Paste {Paste the current contents of the Clipboard into WORD.} WORD.PasteSpecial(formatType) {Paste the current contents of the Clipboard into WORD in the specfied format. The formatType can be TEXT, PICTURE, BITMAP, DEVICE INDEPENDENT BITMAP, and ENHANCED METAFILE.} WORD.Quit WORD.Show {Close the communication with WORD.} {Make the open WORD document visible.} Note that any of the commands can be sent directly from an external program to EES with the application's DDEExecute command. For example, the following command issued from EXCEL Visual Basic will cause EES to execute its SOLVETABLE command for Table 1. Note that when macro commands must be enclosed in square brackets. Application.DDEExecute ChannelNumber, "[SOLVETABLE 'TABLE 1', Rows=1..10]" Unit Lists EES can check the unit consistency of each equation in the Equations Window. This is a very important capability since experience has proven that unit errors are a very common problem both for students and practicing engineers. However, in order for EES to check unit consistency, the units of each variable used in the equations must be specified. There are several ways to enter unit information. Units can be entered for constants in the Equations window, as in the following example: 294 Advanced Features Chapter 7 L = 15 [m] Units for each variable can also be entered in the Variable Information dialog and by right clicking on a variable in the Solutions window or Parametric table. In each case, it is necessary to enter the unit designation from the keyboard, and this chore can be cumbersome. The Units List eliminates the need to key in the units. The Units List can be accessed from the Equations window, the Variable Information dialog, the Parametric table and the Solutions window by clicking the right-mouse button and selecting Units List from the popup menu. This action will bring up the following dialog window. The title bar shows the name of the units list file. EES provides two default lists named SI_DefaultUnits.unt and ENG_DefaultUnits.unt that hold common units for the SI and English system, respectively. The units are shown in the list. Clicking on the desired unit and then clicking the Paste button will paste that unit string into the window that the Units List was accessed from, eliminating the need to enter the units. If you do not wish to have the pop-up list appear, move the SI_DefaultUnits.unt and ENG_DefaultUnits.unt out of the EES folder. Note that double-clicking on a units string in the list has the same effect as clicking the Paste button. If the units list was accessed from the Equations window, the unit string will be enclosed within quotes and square braces before it is pasted into the Equations window. The name of the current units list file is shown in the title bar of the units list dialog. Note that the filename extension is .UNT, but the units file is a simple text (.txt) file that contains the desired unit strings. It is possible to develop customized units lists in separate .UNT files. The buttons located on the panel at the right of the dialog facilitate this process. 295 Chapter 7 Advanced Features Load brings up a file open dialog from which a previously stored units list file (.UNT or .TXT) can be selected. The unit strings in this file will then be displayed in the units list. Save brings up a file save dialog that saves the current units list in a specified .UNT file. Note that EES will automatically read the SI_DefaultUnits.UNT or the ENG_DefaultUnits.UNT file, depending on the current unit system setting, if this file is found in the EES directory or in the default file folder specified in the directories tab of the Preferences dialog. Add New allows a new unit string to be added to the current list. Note that the information in this list is case insensitive. EES will not add a units string if it already exists. Merge will add all of the units strings in the currently open EES file to the existing units list file. Remove will remove the selected units string from the units list. Clear All will remove all units strings from the units list. If any changes are made to the units list, the Exit button will be enabled. Clicking the Exit button will close the dialog, keeping any changes that have been made, but without pasting any information into a window. This behavior differs from the Cancel button in which the dialog is closed without saving any changes, and the Paste button in which the dialog is closed with the specified changes, but the selected units string is pasted into the window that was open when the units dialog was opened. Note that you can edit the .UNT file with a text editor if you wish. If the .UNT file is located in a write-protected directory, it will not be possible for EES to save any specified changes. An error condition will be displayed. This situation occurs when EES is run from a write-protected server. In this case, it will be necessary to Save the units file into a directory that provides write permission to the user. An ideal location is the default file folder specified in the directories tab of the Preferences dialog. A units file, other than the default file, can be automatically loaded with the$INCLUDE directive. Creating Entries to the Visual Libraries The available visual access libraries appear in the Function Information dialog in a drop-down list to the right of the lower right button. Each entry in this list is associated with a folder in the UserLib directory. The contents of this folder include: 296 Advanced Features Chapter 7 One or more EES.lib files that contain the functions that will be accessed One or more .HLP, .TXT, or .PDF files that provide help for the selected function One or more .BMP files that provide the figures shown in the Function dialog. These files may be placed in a subfolder. A XXX .TOC file that provides information EES needs to display the library named XXX. The process is best illustrated by with the View Factors.TOC file shown below. The first 6 lines are currently not used, but they may be used in future versions of EES. Line 1: Name of the library file Line 2: Version Lines 3-5: User-supplied information Line 6: Reserved Following these six lines are groups of information needed to present the visual information in the Function Info dialog. Lines that begin with > indicate a new subheading. The subheadings are shown in the drop downlist to the right of the picture. Following lines provide a set of information for each function using the | character to separate information items. The required information is 1) A name of the function that appears in the dialog 2) The filename of the EES function that provides the external library 3) The filename of the Help file. This file can be a .PDF, .HLP or .TXT file. If a .HLP file is used, the item context number may be included by following the filename with the @ symbol and the help file context number. 4) The filename of the bitmap file that holds a picture representative of the function. The bitmap file has a maximum width of 212 pixels and a maximum height of 160 pixels. Bitmaps will be scaled with a constant aspect ratio if they are larger in either of these dimensions. 5) An example that appears in the Example text box at the bottom of the Function Information dialog. ____________________________________________________________________________ View Factors 1 Intermediate Heat Transfer: Practical Tools and Useful Concepts by G.F. Nellis and S.A. Klein University of Wisconsin - Madison, 2006 297 Chapter 7 View factor information Reserved >2-Dimensional Advanced Features Infinitely long directly opposed parallel plates |View Factors.lib|View [email protected]|BMPS\F2D_1.bmp|F=F2D_1(h,w) Infinitely long plates at angle alpha|View Factors.lib|View [email protected]|BMPS\F2D_2.bmp|F=F2D_2(alpha,w) Infinite plate to cylinder|View Factors.lib|View [email protected]|BMPS\F2D_3.bmp|F=F2D_3(r,a,b,c) Infinite cylinder to cylinder|View Factors.lib|View [email protected]|BMPS\F2D_4.bmp|F=F2D_4(r,s) Infinite concentric cylinders|View Factors.lib|View [email protected]|BMPS\F2D_5.bmp|F=F2D_5(r_1,r_2) >3-Dimensional Finite parallel plates|View Factors.lib|View [email protected]|BMPS\F3D_1.bmp|F=F3D_1(a,b,c) Finite perpendicular plates|View Factors.lib|View [email protected]|BMPS\F3D_2.bmp|F=F3D_2(a,b,c) Disk to disk (same center)|View Factors.lib|View [email protected]|BMPS\F3D_3.bmp|F=F3D_3(r_1,r_2,a) Concentric cylinders|View Factors.lib|View [email protected]|BMPS\F3D_4.bmp|F=F3D_4(r_1,r_2,w) >Differential Plane element dA_1 to plane parallel rectangle|View Factors.lib|View [email protected]|BMPS\FDiff_1.bmp|F=FDiff_1(a,b,c) Strip element dA_1 to plane parallel rectangle|View Factors.lib|View [email protected]|BMPS\FDiff_2.bmp|F=FDiff_2(a,b,c) Plane element dA_1 to plane perdendicular rectangle|View Factors.lib|View [email protected]|BMPS\FDiff_3.bmp|F=FDiff_3(a,b,c) Strip element dA_1 to plane perdendicular rectangle|View Factors.lib|View [email protected]|BMPS\FDiff_4.bmp|F=FDiff_4(a,b,c) 298 Appendix A _____________________________________________________________________________ _____________________________________________________________________________ Hints for Using EES 1. The Variable Information command in the Options menu produces an alphabetical list of all variables appearing in the Equations window. Check this list to make sure that you have not misspelled a variable name. 2. The Residuals window provides an indication of the accuracy in which each non-trivial equation in the Equations window was solved, the order in which the equations are solved, and a summary of the unit checking results. An examination of the residuals indicates which equations were not solved when EES indicates that a solution could not be found. 3. If your equations do not converge, it may be that the guess values are poor. In this case, the problem can often be solved by entering equations which set guess values for one or more of the unknown variables and modifying the equations as needed to ensure an equal number of variables and equations. If a solution is then obtained, use Update Guesses in the Calculate menu to set the guess values of all variables to their current values. Then return the Equations window to its original form and solve again. 4. If EES is unable to solve your set of nonlinear equations, try exchanging some independent and dependent variables to produce an equation set which is easier to solve. For example, EES may not be able to solve the following heat exchanger equations to determine NTU with the default guess values and bounds. Eff=.9 Cmax = 432 Cmin = 251 eff = (1 - exp(-NTU * (1 - (Cmin/Cmax)))) / (1 - (Cmin/Cmax) * exp(-NTU * (1 - (Cmin/Cmax)))) However, the equations would be easily solved if the value of NTU were specified in place of Eff. NTU = 5 Cmax = 432 Cmin = 251 eff = (1 - exp(-NTU * (1 - (Cmin/Cmax)))) / (1 - (Cmin/Cmax) * exp(-NTU * (1 - (Cmin/Cmax)))) A few trials will indicate that NTU must be between 3 and 5 for Eff = 0.9. Setting a guess value for NTU of 4 allows EES to quickly determine the final value of 3.729. 299 Appendix A Hints for Using EES 5. A sure way to solve difficult problems with EES is to add an additional variable so that the problem has one more degree of freedom. Then, use the Parametric Table to vary the values of one of the implicit variables in order to find the solution in which the additional variable has a value of zero. For example, consider the following radiation calculation in which the value of T is to be determined. The first three equations must be solved simultaneously and they are non-linear because T is raised to the fourth power. EES may have trouble determining the solution, depending upon the guess values. QL = AL*Sigma*(T^4 - TL^4) QB = AH*Sigma*(TH^4 - T^4) QL = QB Sigma=0.1718E-8; AL=.5; AH=1; TL=300; TH=1000 Alternatively, add a variable, Delta, such that QL = AL*Sigma*(T^4 - TL^4) QB = AH*Sigma*(TH^4 - T^4)+Delta QL = QB Sigma=0.1718E-8; AL=.5; AH=1; TL=300; TH=1000 Now, set up a Parametric Table containing variables T and Delta. Use the Alter Values command to set a range of values of T and Solve Table to calculate the corresponding values of Delta. The value(s) of T for which Delta is zero constitute a solution to the equation set. The New Plot Window command is handy for visualizing the relationship between T and Delta. If the values of Delta do not cross zero, there is no solution to the equation set for the range of T values investigated. Once a reasonable value of T is found, it can be entered as an equation in the Equations window and an approximate solution corresponding to this value of T can be found. The final step is to use the Update Guesses command in the Calculate menu, set Delta=0 and remove the equation that set the value of T. EES will now quickly converge to the correct solution. This is perhaps the most useful method of solving a difficult set of non-linear equations. 6. The Store button in the Default Info dialog can be helpful if you use a customary set of nomenclature for your variable names. For example, if variables beginning with letter T often designate temperatures, set the bounds, display format and units for letter T and then Store the default information. You can later use the Load button to restore this set of default variable information. EES will then always set this information for you at startup. 7. The arrow keys help some users move about more quickly in the Equations, Parametric and Lookup Tables. In the Equations window, the up and down arrows move the cursor up and down one line; left and right arrow move the cursor left and right one character. Home and End move to the start and end of the current line. In the tables, the arrow keys move to the 300 Hints for Using EES Appendix A next cell in the direction of the arrow. The Return and Tab keys produce the same effects as the down arrow and right arrow keys, respectively. 8. Use the Tab key in the Equations window to set off the equations for improved readability. 9. The Arrays window can be quite useful for organizing the property information in a thermodynamics problem having multiple states. Use array variables, such as T[1], P[1], and h[1] (rather than T1, P1, and h1) for the properties at each state. The state properties will appear in a neat table in the Arrays window, rather than jumbled together in the Solutions window. Be sure the Use Arrays window option in the Display Options dialog has been selected. 10. Considerable effort has been expended to design EES so that it does not unexpectedly quit under any circumstances. However, this may still happen. In this case, EES will try to save your work in a file called EESERROR before it terminates. You can restart EES and load the EESERROR file so none of your work is lost. If you are using the AutoSave option (setting in the Preferences dialog), you may also find the AutoSave temporary file which is a tilda followed by the file name. 11. Use the $INCLUDE directive to load commonly used constants, unit conversions, or other equations into the Equations window. You won’t see them, but they’re there, available for use. You can also load library files with the$INCLUDE directive. 12. If you write an EES Library Function which calls any of the built-in thermodynamic or trigonometric functions, use the UnitSystem command to determine the current unit system settings. Then you can use If Then Else statements to ensure that the arguments provided to the thermodynamic or trigonometric functions have the correct values. 13. The background color option for columns in the Parametric Table is useful if you are preparing an EES program in which others will be entering data into the columns, as in a spreadsheet. Set the background color for the columns in which data are to be entered, to distinguish them from the columns in which calculated results will appear. 14. If you are working in Complex Mode, use the \$COMPLEX ON directive at the top of the Equations window. It is more convenient than changing the Complex Mode setting in the Preferences dialog. 15. To enter µm, hold the Alt-Key down and type 230 on the numeric keypad. Let the Alt key up and the µ should appear. Then enter m. Other useful characters are Alt-248 which displays the degree symbol ° and Alt-250 which appears as a dot (·) and is used to represent multiplication. 301 Appendix B _____________________________________________________________________________ _____________________________________________________________________________ EES uses a variant of Newton's method [1-4] to solve systems of non-linear algebraic equations. The Jacobian matrix needed in Newton's method is evaluated numerically at each iteration. Sparse matrix techniques [5-7] are employed to improve calculation efficiency and permit rather large problems to be solved in the limited memory of a microcomputer. The efficiency and convergence properties of the solution method are further improved by the step-size alteration and implementation of the Tarjan [8] blocking algorithm which breaks the problems into a number of smaller problems which are easier to solve. Several algorithms are implemented to determine the minimum or maximum value of a specified variable [9,10]. Presented below is a summary of these methods, intended to provide users with a better understanding of the processes EES uses in obtaining its solutions. Numerical Methods Used in EES Solution to Algebraic Equations Consider the following equation in one unknown: x3 - 3.5 x2 + 2 x = 10 To apply Newton's method to the solution of this equation, it is best to rewrite the equation in terms of a residual, ε, where ε = x3 - 3.5 x2 + 2 x - 10 The function described by this equation is shown in Figure 1. There is only one real solution (i.e., value of x for which ε = 0) in the range illustrated at x = 3.69193. 20 I mproved guess I nitial guess 1 0 ε -1 0 0 -20 -2 -1 0 1 2 3 4 5 x Figure 1: Residual of x3 - 3.5 x2 + 2 x = 10 as a function of x 302 Numerical Methods used in EES Appendix B Newton's method requires an estimate of the total derivative of the residual, J. For this equation, the derivative is: J = d ε = 3 x2 – 7 x + 2 dx To solve the equation, Newton's method proceeds as follows: 1. An initial guess is made for x (e.g., 3). 2. The value of ε is evaluated using the guess value for x. With x = 3, ε = -8.5. 3. The derivative J is evaluated. With x = 3, J = 8. 4. The change to the guess value for x, i.e., Δx, is calculated by solving J Δx = ε. In this example, Δx is -1.0625. 5. A (usually) better value for x is then obtained as x - Δx. In the example, the improved value for x is 4.0625 (which results in ε = 7.4084). Steps 2 to 5 are repeated until the absolute value of ε or Δx becomes smaller than the specified tolerances in the Stop Criteria dialog. The method, when it converges, converges quite quickly. However, a bad initial guess can cause the method to diverge or to converge quite slowly. Try, for example, an initial guess of 2 and see what happens. Newton's method can be extended for solving simultaneous non-linear equations. In this case, the concept of "derivative" generalizes into the concept of "Jacobian matrix." Consider the following two simultaneous equations in two unknowns: x2 + x2 – 18 = 0 1 2 x1 - x2 = 0 The equations can be rewritten in terms of residuals ε1 and ε2: ε1 = x2 + x2 – 18 = 0 2 1 ε 2 = x1 - x 2 = 0 The Jacobian for this matrix is a 2 by 2 matrix. The first row contains the derivatives of the first equation with respect to each variable. In the example above, the derivative of ε1 with respect to x2 is 2 x2. The Jacobian matrix for this example is: J= 2⋅x1 2⋅x2 1 –1 Newton's method as stated above applies to both linear and nonlinear sets of equations. If the equations are linear, convergence is assured in one iteration, even if a "wrong" initial guess was made. Non-linear equations require iterative calculations. Consider the following initial guess: x= 2 2 303 Appendix B Numerical Methods used in EES ε = – 10 0 J= 44 1 –1 The values of ε and J for this initial guess are: Improved values for the x vector are obtained by solving the following matrix problem involving the Jacobian and the residual vector. 44 1 –1 Δx1 = –10 Δx2 0 Solving this linear equation results in: Δx1 = – 1.25 – 1.25 Δx2 Improved estimates of the x1 and x2 are obtained by subtracting Δx1 and Δx2, respectively, from the guess values. x1 3.25 x2 = 3.25 The correct solution to this problem is x1 = x2 = 3.0. The calculated values of x1 and x2 are closer to the correct solution than were the guess values. The calculations are now repeated using the most recently calculated values of x1 and x2 as the guess values. This process is repeated until convergence is obtained. The Jacobian matrix plays a key role in the solution of algebraic equations. The Jacobian matrix can be obtained symbolically or numerically. Symbolic evaluation of the Jacobian is more accurate, but requires more processing. Accuracy of the Jacobian, however, does not necessarily lead to more accuracy in the solution, only to (sometimes) fewer iterations. EES evaluates the Jacobian numerically. Because EES does all calculations with 96 bit precision (about 20 decimal places), numeric evaluation of the Jacobian rarely results in convergence problems from loss of precision. In most equation sets, many of the elements of the Jacobian matrix are zero. A matrix with many zero elements is called a sparse matrix. Special ordering and processing techniques make handling of sparse matrices quite efficient. In fact, without sparse matrix techniques the number of simultaneous equations which could be solved by EES would be substantially less than 6000, (10,000 in the Professional version) the current limit implemented in EES. Further references on sparsity and on how to handle sparse matrices are available in [5, 6]. A collection of routines that are designed to handle very large sparse matrices are described in [7]. Newton's method does not always work, particularly if a "bad" initial guess for the x vector is supplied. The solution obtained after applying the correction Δx to the previous x vector should be more correct (i.e., result in a smaller maximum residual) than the solution obtained before 304 Numerical Methods used in EES Appendix B the correction. EES always checks for this condition. If this is not true, EES will halve the step Δx and evaluate the residuals again. If this does not improve the solution, the step is halved again (up to 20 times). If the resultant solution is still not better than the solution prior to the correction, EES will reevaluate the Jacobian and try again until one of the stopping criteria forces the calculations to stop. Step halving is very helpful when a bad initial guess is provided. Figure 2 illustrates the process for the solution of the single equation in the first example, starting from a guess of x=2.5. In this case, step halving works quite well. 60 40 Initial step ε 20 Initial guess Reduced step 0 Half step -20 0 1 2 3 4 5 6 Full step x Figure 2: Use step-halving for improving the convergence Blocking Equation Sets Even though you may have what looks like a set of simultaneous equations, it is often possible to solve these equations in groups (sometimes one at the time) rather than all together as one set. Solving equations in groups makes Newton's method work more reliably. For this reason, EES organizes the equations into groups (or blocks) before solving. Consider, for example, the following set of equations: x1 + 2 x2 + 3 x3 = 11 5 x3 = 10 3 x2 + 2 x3 = 7 These equations can be solved as one simultaneous set. However, they can be more easily solved if they are reordered and blocked. It is better to re-order first. EES automatically 305 Appendix B Numerical Methods used in EES recognizes that equation 2 can be solved directly for x3. Once this is done, equation 3 can be solved for x2. Finally, equation 1 can be solved for x1. This results in three blocks of equations, each with one equation and one variable which are directly solved. Because the equations in this example are linear and they can be totally uncoupled, the process looks trivial. Things can get a little more interesting if the blocks are a little less obvious. Consider the following example with 8 linear equations in 8 unknowns: x3 x5 x1 x2 x3 x4 x1 + x6 + x7 - x5 + x4 - x6 - x6 x7 - x7 + x8 + x7 + x8 = 11 =7 = -8 = -1 = 10 =5 =4 = 14 These equations and variables can be re-numbered and blocked. Each block is solved in turn. In the case above, blocking allows the equations to be solved in 6 blocks as follows: Block 1: Equation 7 x4 = 4 Block 2: Equation 2 x7 = 7 Block 3: Equations 4 and 8 x1 + x4 - x6 = -1 x1 + x6 + x7 = 14 Block 4: Equation 3 x5 - x6 - x7 = -8 From here and: From here: From here: and: From here: x1 = 1 x6 = 6 x5 = 5 x3 = 3 x8 = 8 x2 = 2 Block 5: Equations 1 and 6 x3 + x8 = 11 x3 - x5 + x7 = 5 Block 6: Equation 5: x2 + x8 = 10 The first two blocks contain a single equation with a single variable. These blocks simply define constants. EES will recognize that equations that depend from the start on a single variable are in reality parameter or constant definitions. These parameters are determined before any solution of the remaining equations takes place. No lower and upper limits on the guesses are needed for parameters, since the values of these parameters are determined 306 Numerical Methods used in EES Appendix B immediately. The solution of the remaining equations is now very simple, although it did not appear trivial at the beginning of the process. Grouping of equations is useful when the equations are linear, but it is not essential. When the equations are nonlinear, grouping of equations is nearly indispensable, otherwise later groups of equations begin iterating with totally incorrect values of earlier variables. The result is often divergence. EES is able to recognize groups of equations prior to solution by inspecting the Jacobian matrix using the Tarjan [8] algorithm. See reference [6] for more details on this algorithm. Determination of Minimum or Maximum Values EES has the capability to find the minimum or maximum (i.e., optimum) value of a variable when there is one to ten degrees of freedom (i.e., the number of variables minus the number of equations). For problems with a single degree of freedom, EES can use either of two basic algorithms to find a minimum or maximum: a recursive quadratic approximation known as Brent's method or a Golden Section search [9]. The user specifies the method, the variable to be optimized and an independent variable whose value will be manipulated between specified lower and upper bounds. When there are two or more degrees of freedom, EES uses Brent's method repeatedly to determine the minimum or maximum along a particular direction. The direction is determined by a direct search algorithm known as Powell's method or by the conjugate gradient method [9,10]. The recursive quadratic approximation algorithm proceeds by determining the value of the variable which is to be optimized for three different values of the independent variable. A quadratic function is fit through these three points. Then the quadratic function is differentiated analytically to locate an estimate of the extremum point. If the relationship between the variable which is being optimized and the independent variable is truly quadratic, the optimum is found directly. If this is not the case, the algorithm will use the newly obtained estimate of the optimum point and two (of the three) points which are closest to it to repeat the quadratic fit. This process is continued until the convergence criteria set for the minimization/maximization process are satisfied. 307 Appendix B Numerical Methods used in EES The Golden Section search method is a region-elimination method in which the lower and upper bounds for the independent variable specified by the user are moved closer to each other with each iteration. The region between the bounds is broken into two sections, as shown in Figure 3. The value of the dependent variable is determined in each section. The bounds for the section which contains the smaller (for minimization) or larger (for maximization) dependent variable replace the interval bounds for the next iteration. Each iteration reduces the distance between the two bounds by a factor of (1-τ) where τ =0.61803 is known as the Golden Section ratio. Sect i on 1 τ (1 − τ ) Sect i on 2 Figure 3: Region Elimination using the Golden Section Method Numerical Integration EES integrates functions and solves differential equations using a variant of the trapezoid rule along with a predictor-corrector algorithm. In explaining this method, it is helpful to compare the numerical scheme with the manner one would use to graphically determine the value of an integral. Consider the problem of graphically estimating the integral of the function f = 5 -5 X + 10 X2 for X between 0 and 1. In graphical integration, a plot of f versus X would be prepared. The abscissa of the plot would be divided into a number of sections as shown below. The area under the curve in each section is estimated as the area of a rectangle with its base equal to the width of the section and its height equal to the average ordinate value in the section. For example, the ordinate values at 0 and 0.2 in the plot below are 5 and 4.4, respectively. The area of the first section is then 0.2 * (5+4.4)/2 or 0.94. The estimate integral value between 0 and 1 is the sum of the areas of the 5 sections. The accuracy of this method improves as the number of sections is increased. 308 Numerical Methods used in EES 10.0 8.0 Appendix B f = 5.5 X + 10 X2 6.0 4.0 2.0 0.0 0. 0 0. 2 0. 4 X 0. 6 0. 8 1. 0 Figure 4: Numerical approximation of an integral Integration in EES takes place in a manner quite analogous to the graphical representation. The abscissa variable, X, in the example above, is placed in the Parametric Table. The values of X entered into the table identify the width of each section. EES does not require each section to have the same width. The numerical value of the function, f, which is to be integrated, is evaluated at each value of X and supplied to EES through the Integrate function, e.g., Integral(f,X,0,1). In some situations, such as in the solution of differential equations, the value of f may not be explicitly known at a particular value of X. The value of f may depend upon the solution to non-linear algebraic equations which have not yet converged. Further, the value of f may depend upon the value of the integral up to that point. In this case, iteration is needed. EES will repeatedly evaluate the section area using the latest estimate of f at the current value of X until convergence is obtained. The procedure in which the estimate of the integral made on the first calculation is corrected with later information is referred to as a predictor-corrector algorithm. 309 Chapter 7 Advanced Features References 1. A. W. Al-Khafaji and J. R. Tooley, Numerical Methods in Engineering Practice, Holt, Rinehart and Winston, 1986, pp. 190 & ff. 2. C. F. Gerald and P. O. Wheatley, Applied Numerical Analysis, Addison-Wesley 1984, pp. 135 & ff. 3. J. H. Ferziger, Numerical Methods for Engineering Application, Wiley-Interscience 1981, Appendix B. 4. F. S. Acton, Numerical Methods that Usually Work, Harper and Row 1970. 5. I. S. Duff, A. M. Erisman and J. K. Reid, Direct Methods for Sparse Matrices, 1986 Oxford Science Publications, Clarendon Press. 6. S. Pissanetsky, "Sparse Matrix Technology," Academic Press 1984. 7. F. L. Alvarado, "The Sparse Matrix Manipulation System," Report ECE-89-1, Department of Electrical and Computer Engineering, The University of Wisconsin, Madison, Wisconsin, January 1989. 8. Tarjan, R. "Depth-First Search and Linear Graph Algorithms," SIAM J. Comput. 1, 146160, (1972) 9. Powell's Method of Successive Quadratic Approximations, Reklaitis, Ravindran and Radsdell, Engineering Optimization, John Wiley, New York, (1983) 10. W. H. Press, B. P. Flannery and S. A. Teukolsky, and Vetterling, W.T., Numerical Recipes in Pascal, Cambridge University Press, Chapter 10, (1989) 310 311 Appendix C _____________________________________________________________________________ _____________________________________________________________________________ Adding Property Data to EES Background Information EES uses an equation of state approach rather than internal tabular data to calculate the properties of fluids. For some substances and conditions, the ideal gas law is applicable. EES employs a naming convention to distinguish ideal gas and real fluid substances. Substances which are represented by their chemical symbol (e.g., N2) are modeled with the ideal gas law whereas substances for which the name is spelled out (e.g., Nitrogen) are considered to be real fluids. (Air and AirH2O are exceptions to this naming convention.) Ideal gas substances rely on JANAF table data [Stull, 1971] to provide the enthalpy of formation and absolute entropy at a reference state of 298 K, 1 atm. Specific heat correlations for these gases and the ideal gas law are used to calculate the thermodynamic properties at conditions other than the reference state. A number of ideal gas substances are built into EES. The external JANAF program provides thermodynamic property information for hundreds of additional substances. Additional ideal gas fluid data can be added with .IDG files in the USERLIB folder, as explained below. Real fluids properties are implemented with several different equations of state. Early versions of EES used the Martin-Hou [1955] equation of state (or variations of it) for all real fluids except water. The Martin-Hou property data base is still supported in EES. However, this equation of state is unable to provide accurate results for states near the critical point or at very high pressures. It is also unable to provide properties in the subcooled region. For this reason, a high accuracy equation of state has been implemented in the form of the Fundamental Equation of State (Tillner-Roth [1998]). The Fundamental Equation of State provides highly accurate properties in all regimes. In some cases, properties for a fluid, e.g., carbon dioxide, are implemented with both the Martin-Hou and the Fundamental Equation of State. In this case, the letters ha are appended to fluid name, e.g., R134a_ha. Several equations of state are provided for water, the most accurate and computationally intensive being the equation of state published by Harr, Gallagher, and Kell [1984]. Ice properties rely upon correlations developed by Hyland and Wexler [1983]. Thermodynamic property relations are used to determine enthalpy, internal energy and entropy values based upon the equation of state and additional correlations for liquid density, vapor pressure, and zero-pressure specific heat as a function of temperature. A modification to the 312 Martin-Hou equation of state proposed by Bivens et al. [1996] allows this equation equation of state to be applied for mixtures, such as the R400 refrigerant blends. Viscosity and thermal conductivity of liquids and low-pressure gases are correlated with fluid specific relations. Many rely on polynomials in temperature. Temperature alone determines the transport properties for ideal gases. For real fluids, the effect of pressure on the gas transport properties is estimated using correlations from Reid et al. [1977] or included in the fluid specific relations. For example, the transport properties for fluid CarbonDioxide use the transport properties of Vesovic et al. [1990]. The source of all data implemented in EES can be viewed using the Fluid Info button of the Function Info dialog in the Options menu. Adding Fluid Properties to EES EES has been designed to allow additional fluids to be added to the property data base. Currently, it is possible to add property information for ideal gas fluids and for fluids represented by the Martin-Hou [1949] equation of state. Fluids represented by the Fundamental Equation of State cannot be added by the user. To add property information, the user must supply the necessary parameters for the thermodynamic and transport property correlations. The parameters are placed in an ASCII text file which must be located in the EES\USERLIB subdirectory. EES will load all fluid files found in the EES\USERLIB subdirectory at startup. The additional fluids will appear in every way identical to the built-in fluids. The following sections describe the format required for the property data files. Ideal Gas files Ideal gas files must have a .IDG filename extension. An equation of state is not needed since it is assumed that the fluid obeys the ideal gas equation of state. However, particular attention must be paid to the reference states if the gas is to be used in calculations involving chemical reactions. The enthalpy of formation and Third-law entropy values at 298 K and 1 bar (or 1 atm) must be supplied. An example file providing the parameters for CO2 is provided below. The properties of ideal gas fluid can be entered by adapting the file format to the new fluid. SAMPLE TESTCO2.IDG File TestCO2 44.01 100.0 250 1500 -3.7357 30.529 -4.1034 0.02420 00 {Molar mass of fluid {Tn Normalizing value in K} {Lower temperature limit of Cp correlation in K} {Upper temperature limit of Cp correlation in K} 0 {a0, b0 Cp=sum(a[i]*(T/Tn)^b[i], i=0,9 in kJ/kgmole-K} 0.5 {a1, b1} 1.0 {a2, b2} 2.0 {a3, b3} {a4, b4} 313 00 {a5, b5} 00 {a6, b6} 00 {a7, b7} 00 {a8, b8} 00 {a9, b9} 298.15 {TRef in K} 100 {Pref in kPa} -393520 {hform - enthalpy of formation in kJ/kgmole at TRef} 213.685 {s0 - Third law entropy in kJ/kgmole-K at Tref and PRef} 0 {reserved - set to 0} 0 {reserved - set to 0} 200 {Lower temperature limit of gas phase viscosity correlation in K} 1000 {Upper temperature limit of gas phase viscosity correlation in K} -8.09519E-7 {v0 Viscosity = sum(v[i]*T^(i-1)) for i=0 to 5 in Pa/m^2} 6.039533E-8 {v1} -2.8249E-11 {v2} 9.84378E-15 {v3} -1.4732E-18 {v4} 0 {v5} 200 {Lower temperature limit of gas phase thermal conductivity correlation in K} 1000 {Upper temperature limit of gas phase thermal conductivity correlation in K} -1.1582E-3 {t0 Thermal Conductivity = sum(t[i]*T^(i-1)) for i=0 to 5 in W/m-K} 3.9174E-5 {t1} 8.2396E-8 {t2} -5.3105E-11 {t3} 3.1368E-16 {t4} 0 {t5} 0 {Terminator - set to 0} Real Fluid Files Represented by the Martin-Hou Equation of State A pure real fluid is identified with a .MHE (for Martin-Hou Equation) filename extension. A sample file named XFLUID.MHE is listed on the following pages illustrating the required file format. (The sample file contains the parameters used for n-butane.) The file consists of 75 lines. The first line provides the name of the fluid which EES will recognize in the property function statements. For example, the first line in the sample file contains UserFluid. The enthalpy for this substance would then be obtained as follows. h=Enthalpy(UserFluid,T=T1, P=P1) The fluid name will appear in alphabetical order with other fluid names in the Function Information dialog window. The following 74 lines each contain one number. A comment follows on the same line (after one or more spaces) to identify the number. The forms of all of the correlations except the pressure-volume-temperature relation are indicated in the 314 XFLUID.MHE file. Pressure, volume and temperature are related by the Martin-Hou equation of state in the following form. A method for obtaining the coefficients is described by Martin and Hou, [1955]. Martin-Hou Equation of State (parameters in lines 18-36) A + B2T + C2e– βT/Tc A3 + B3T + C3e– βT/Tc P= RT + 2 + 2 3 v–b v–b v–b + A4 + B4T + C4e– βT/Tc A5 + B5T + C5e– βT/Tc A6 + B6T + C6e– βT/Tc + + 4 5 eαv(1 + C′eαv) v–b v–b where P [=] psia, T [=] R, and v [=] ft3/lbm You may need to curve fit tabular property data or data obtained form a correlation in a different form to obtain the appropriate parameters. Most of the correlations are linear with respect to the parameters so that they can be determined by linear regression. A parameter set which improves upon the fit resulting from the Martin and Hou method can be determined by non-linear regression. EES can be used to do these regressions. SAMPLE XFLUID.MHE File for pure fluids UserFluid 58.1 0 12.84149 { molecular weight} { not used} { a} Liquid Density=a+b*Tz^(1/3)+c*Tz^(2/3)+d*Tz+e*Tz^(4/3)+f*sqrt(Tz)+g*(Tz)^2} 33.02582 { b} where Tz=(1-T/Tc) and Liquid Density[=]lbm/ft3 -2.53317 { c} -0.07982 { d} 9.89109 { e} 0 { f} 0 { g} -6481.15338 { a} Vapor pressure fit: lnP=a/T+b+cT+d(1T/Tc)^1.5+eT^2 15.31880 { b} where T[=]R and P[=]psia -0.0006874 { c} 4.28739 { d} 0 { e} 0 { not used} 0.184697 { Gas constant in psia-ft3/lbm-R} 1.5259e-2 { b} Constants for Martin-Hou EOS/English_units -20.589 { A2} 9.6163e-3 { B2} -314.538 { C2} 0.935527 { A3} -3.4550e-4 { B3} 19.0974 { C3} 315 -1.9478e-2 0 0 0 2.9368e-7 -5.1463e-3 0 0 0 5.475 0 0 -7.39053E-3 e/T^2 6.4925e-4 9.0466e-8 -1.1273e-10 5.2005e3 124.19551 0.0956305 550.6 765.3 0.07064 0 0 2 260 535 -3.790619e6 5.42356586e4 -7.09216279e1 5.33070354e-2 115 235 2.79677345e3 -2.05162697e1 5.3698529e-2 -4.88512807e-5 2 change} 250 535 7.5931e-3 -6.3846e-5 3.95367e-7 -2.9508e-10 115 235 2.776919161e-1 -8.45278149e-4 1.57860101e-6 { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { { A4} B4} C4} A5} B5} C5} A6} B6} C6} Beta} alpha} C'} a} Cv(0 pressure) = a + b T + c T^2 + d T^3 + b} where T[=]R and Cv[=]Btu/lb-R c} d} e} href offset} sref offset} Pc [=] psia} Tc [=] R} vc [=] ft3/lbm} not used} not used} Viscosity correlation type: set to 2: do not change} Lower limit of gas viscosity correlation in K} Upper limit of gas viscosity correlation in K} A} GasViscosity*1E12=A+B*T+C*T^2+D*T^3 B} where T[=]K and GasViscosity[=]N-s/m2 C} D} Lower limit of liquid viscosity correlation in K} Upper limit of liquid viscosity correlation in K} A} Liquid Viscosity*1E6=A+B*T+C*T^2+D*T^3 B} where T[=]K and Liquid Viscosity[=]N-s/m2 C} D} Conductivity correlation type: set to 2: do not Lower Upper A} B} C} D} Lower Upper A} B} C} limit of gas conductivity correlation in K} limit of gas conductivity correlation in K} GasConductivity=A+B*T+C*T^2+D*T^3 where T[=]K and GasConductivity[=]W/m-K limit of liquid conductivity correlation in K} limit of liquid conductivity correlation in K} LiquidConductivity=A+B*T+C*T^2+D*T^3 where T[=]K and LiquidConductivity[=]W/m-K 316 -1.8381151e-9 0 { D} { not used: terminator} Fluid Properties for Blends The Martin-Hou equation of state can be adapted for mixtures as proposed by Bivens et. al. The major modifications needed to make this pure component equation of state applicable to blends is to provide separate correlations for the bubble and dew point vapor pressures and a correlation for the enthalpy of vaporization, since the equation of state can not provide this information. Shown below is a listing of the R410A.MHE file that is used to provide property data for R410A, along with an explanation of each line in the file. R410A 72.584 {molecular weight Bivens and Yokozeki} 400 {Indicator for blend} 30.5148 {a} Liquid density = a+b*Tz^(1/3)+c*Tz^(2/3)+d*Tz 60.5637 {b} +e*Tz^(4/3)+f*sqrt(Tz)+g*(Tz)^2} -5.39377 {c} where Tz=(1-T/Tc) and Liquid Density[=]lbm/ft3 55.5360815 {d} -21.88425 {e} 0 {f} 0 {g} -5.9789E+03 -5.9940E+03 {a} Bubble and Dew Pt Vapor pressure fit: 24.06932 24.04507 {b} lnP=a/T+b+cT+d(1-T/Tc)^1.5+eT^2 -2.1192E-02 -2.1084E-02 {c} where T[=]R and P[=]psia fit -5.5841E-01 -4.4382E-01 {d} 1.3718E-05 1.3668E-05 {e} 00 {not used} 0.1478 {Gas constant in psia-ft3/lbm-R} 0.006976 {b} Constants for Martin-Hou EOS/English_units from Bivens -6.40764E+00 {A2} 3.40372E-03 {B2} -2.34220E+02 {C2} 1.41972E-01 {A3} 4.84456E-06 {B3} 9.13546E+00 {C3} -4.13400E-03 {A4} 0 {B4} 0 {C4} -9.54645E-05 {A5} 1.17310E-07 {B5} 2.45370E-02 {C5} 0 {A6} 0 {B6} 0 {C6} 5.75 {Beta} 0 {alpha} 0 {C'} 317 0.036582 {a} Cv(0 pressure) = a + b T + c T^2 + d T^3 + e/T^2 2.808787E-4 {b} where T[=]R and Cv[=]Btu/lb-R from Bivens -7.264730E-8 {c} 2.6612670E-12 {d} 0 {e} 65.831547 {href offset} -0.082942 {sref offset} 714.5 {Pc [=] psia} 621.5 {Tc [=] R} 0.03276 {vc [=] ft3/lbm} 0 {not used} 7 {# of coefficients which follow - used for blends} 1 {DeltaH Correlation type} 0.5541498 {Xo} 87.50197 {A} DeltaH_vap=A+B*X+C*X^2+D*X^3+E*X^4 Bivens 185.3407 {B} where X =(1-T/Tc)^.333-X0, T in R and enthalpy in Btu/lb 13.75282 {C} 0 {D} 0 {E} 2 {Viscosity correlation type: set to 2: do not change} 200 {Lower limit of gas viscosity correlation in K} 500 {Upper limit of gas viscosity correlation in K} -1.300419E6 {A} GasViscosity*1E12=A+B*T+C*T^2+D*T^3 5.39552e4 {B} where T[=]K and GasViscosity[=]N-s/m2 -1.550729e1 {C} 0 {D} -999 {Lower limit of liquid viscosity correlation in K} -999 {Upper limit of liquid viscosity correlation in K} 0 {A} Liquid Viscosity*1E6=A+B*T+C*T^2+D*T^3 0 {B} where T[=]K and Liquid Viscosity[=]N-s/m2 0 {C} 0 {D} 2 {Conductivity correlation type: set to 2: do not change} 200 {Lower limit of gas conductivity correlation in K} 500 {Upper limit of gas conductivity correlation in K} -8.643088e-3 {A} GasConductivity=A+B*T+C*T^2+D*T^3 7.652083e-5 {B} where T[=]K and GasConductivity[=]W/m-K 2.144608e-9 {C} 0 {D} -999 {Lower limit of liquid conductivity correlation in K} -999 {Upper limit of liquid conductivity correlation in K} 0 {A} LiquidConductivity=A+B*T+C*T^2+D*T^3 0 {B} where T[=]K and LiquidConductivity[=]W/m-K 0 {C} 0 {D} 0 {terminator} {The forms of the correlations and in some cases the coefficients have been adapted from D.B. Bivens and A. Yokozeki, "Thermodynamics and Performance Potential of R-410a," 1996 Intl. Conference on Ozone Protection Technologies Oct, 21-23, Washington, DC.} 318 References ASHRAE Handbook of Fundamentals, (1989, 1993, 1997), American Society of Heating, Refrigerating and Air Conditioning Engineers, Atlanta, GA ASHRAE, Thermophysical Properties of Refrigerants, American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Atlanta, GA, (1976) D.B. Bivens and A. Yokozeki, "Thermodynamics and Performance Potential of R-410a," 1996 Intl. Conference on Ozone Protection Technologies Oct, 21-23, Washington, DC. Downing, R.C. and Knight, B.W., "Computer Program for Calculating Properties for the "FREON" Refrigerants," DuPont Technical Bulletin RT-52, (1971); Downing, R.C., "Refrigerant Equations", ASHRAE Transactions, Paper No. 2313, Vol. 80, pt.2, pp. 158-169, (1974) Gallagher, J., McLinden, M, Morrison, G., and Huber, M., REFPROP - NIST Thermodynamic Properties of Refrigerants and Refrigerant Mixtures, Versions 4, 5, and 6, NIST Standard Reference Database 23, NIST, Gaithersburg. MD 20899, (1989) Harr, L. Gallagher, J.S., and Kell, G.S (Hemisphere, 1984). 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