Unformatted text preview: Homework 4 Problem 5 HYSYS Heat Exchanger Design
20 points possible due Tuesday September 27, 2011 Grader: Israel Problem Statement: A gas under an average pressure of 1010 kPa with properties equivalent to those of air must be cooled from 65.5 to 37.8°C. Cooling water is available at a temperature of 21.1°C and 60 psig. Use of a shell‐and‐tube floating‐head heat exchanger with cooling water as the utility fluid has been proposed. On the basis of the following optimized data and specifications, model the given heat exchanger which will handle 2.52 kg/s of high pressure gas. Exchanger Specifications Steel shell‐and‐tube exchanger with cross‐flow baffling TEMA type AES Cooling water on the shell side of the exchanger Horizontal exchanger orientation One tube pass and countercurrent flow Tube pitch of 1.25 Tube dimensions: OD = 0.0254 m, ID = 0.0198 m Tube Length : 3.65 m 48 tubes Baffle grid in horizontal orientation Baffle Cut Area : 31 % Baffle Spacing : 0.054 m Method of Solution: Use the Heat Exchanger Unit Operation in HYSYSTM to model the described heat exchanger. Solution: 1) Start the HYSYSTM program: Programs/AspenTech/Apen Engineering Suite/Aspen HYSYS 2006/Aspen HYSYS 2006 2) Open a new case by either clicking the New Case icon on the toolbar, or by selecting File New Case from the Menu bar. 3) The Simulation Basis Manager window will appear. First we must add fluid property packages to estimate the physical properties of our process components. Click on Page 1 of 9 the Fluid Pkgs tab. Click Add. Select the UNIQUAC package from the Property Package Selection list. 4) Now, let’s add our components. Click View in the Component List Selection box. 5) The Component List View window should open. In the Match field, type “water”. Be sure that H2O is highlighted and then click Add Pure to add it to the Selected Components List. Page 2 of 9 6) In the Match field, type “air”. Be sure that air is highlighted and then click Add Pure to add it to the Selected Components List. 7) Close the Component List View window and Fluid Package Basis window 8) Click Enter Simulation Environment. 9) Add a Heat Exchanger unit to the PFD workspace by clicking the icon on the Object Palette or by selecting FlowsheetAdd OperationHeat Exchanger from the menu bar. 10) Double‐click on the heat exchanger icon on the workspace. Input a Tube Side Inlet, Tube Side Outlet, Shell Side Inlet, and Shell Side Outlet. Page 3 of 9 11) Click on the Worksheet tab. Enter the problem flow specifications. Be sure the units are correct. Page 4 of 9 12) Click on Composition on the left hand side of the E‐100 window. Enter a mole fraction of 1 for Air in the Gas In Stream. Enter a mole fraction of 1 for Water in the Cooling Water In Stream. An Input Composition will open for each stream. Click OK in the lower right hand corner of the pop‐up window. 13) If you click back to Conditions, you will see that the Gas In stream is fully defined. 14) Click on the Rating tab. With the Overall radio button selected in the Sizing Data box, specify 1 shell (1 pass, 1 in series, 1 in parallel). Specify 1 tube pass per shell. Click OK in the HYSYS pop‐up window. Specify horizontal orientation and a counter flow direction. Specify the TEMA type as AES. Page 5 of 9 15) Click the Shell radio button in the Sizing Data box. Specify the Number of Tubes per Shell as 48 and a tube pitch of 31.75 mm ( OD x tube pitch specification = 31.75 mm). Change the Shell Baffle Type to Grid by clicking on the drop‐down arrow in the input window. Specify the Baffle Cut as 31% and the Baffle Spacing as 54 mm. Page 6 of 9 16) Click the Tube radio button. Specify the outer and inner diameter and the tube length. The default thermal conductivity is set for steel. 17) All data giving in the problem statement is now defined in the heat exchanger, but the unit has not solved. This is because the appropriate heat exchanger model has not been set. Click on the Design tab and click on Parameters on the left hand side of the window. Click the drop‐down arrow in the Heat Exchanger Model box. Select Steady State Rating. 18) The Heat Exchanger will take a moment to solve. The Status bar should change color to green and display OK when the unit has converged. Page 7 of 9 19) Close the E‐100 window. Right click on the PFD and select Add Workbook Table. In the pop‐up window, highlight Material Streams and click Select. 20) The final PFD should appear similar to the following figure: Page 8 of 9 Results/Considerations: Using HYSYSTM, the optimized heat exchanger was modeled with relative ease. Hand‐
calculations would require more time. Computer simulations are essential for an Engineer to provide realistic results in a realistic timeframe. Page 9 of 9 ...
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