Lecture_F11_ECH157_SimulinkTutorial

Lecture_F11_ECH157_S - ECH 157 A Simulink Tutorial This tutorial exposes you to the main ideas youll need to use Simulink in ECH 157 A tutorial

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E CH 157 A Simulink Tutorial - 1 - This tutorial exposes you to the main ideas you&ll need to use Simulink in E CH 157 . A tutorial example Consider the heat exchange process shown in Figure 1. Suppose that you can adjust the inlet liquid rate ( i w ) and temperature ( T i ), and the steam temperature ( T s ) independently. The liquid outlet temperature ( T o ) and flow rate ( o w ), and the heat transfer rate ( q ) vary accordingly. w o Steam Condensate shell tube Liquid In Liquid Out T s . T s T o T i w i . . q Figure 1 Shell-and-tube heat exchanger schematic We make the following simplifying assumptions: 1. The inlet steam is saturated, and the condensate leaves as a saturated liquid at the same temperature. 2. U = 800 W m 2 K A = 300 m 2 , so UA = 240 kW/K (constant) 3. Other constants: liquid density, ρ L = 800 kg/m 3 ; liquid holdup in tubes, V L = 2.1 m 3 ; liquid heat capacity, C p = 1.8 kJ/kg-K, all independent of temperature. 4. Energy accumulation in the tube wall material is negligible. 5. Liquid in tubes is well-mixed in the radial and axial dimensions (a poor assumption if the tubes are long) and incompressible. Using background from previous courses (and a few additional assumptions), you should be able to obtain the following model equations: w w w o i = = (1) ) ( o s T T UA q = (2) () () ) ( o s o i p o i p o p T T UA T T C w q T T C w dt dT wC + = + = (3) where
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E CH 157 A Simulink Tutorial - 2 - w mass rate of liquid entering and leaving the tubes, kg/s q rate of heat transfer to the liquid in the tubes, kW w mass of liquid in the tubes (= ρ L V L ), kg UA product of overall heat transfer coefficient and tube surface area, kW/K T s steam temperature, o C T i , T o temperature of liquid entering and leaving tubes, o C. C p specific heat of liquid at constant pressure, kJ/kg-K Given the values of w , T i , and T s as functions of time & and suitable initial conditions & it should be possible to solve equations (2) and (3) for T o and q as functions of time. One way would be to use MATLAB techniques. The purpose of this tutorial is to illustrate some related methods that are more convenient for process control. NOTE: All graphics are from a PC running MATLAB Version 6, Release 12. Some window views may change on other configurations. Figure 2 The Simulink Library Browser window has just been opened. Building a Simulink model Opening the Library Browser and model windows With MATLAB running, type simulink 1 in the command window. This opens the Simulink Library Browser window (see Figure 2), which provides building blocks for model creation. 1 I±ll use a Courier font to represent MATLAB commands that you should type in the MATLAB Command Window.
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E CH 157 A Simulink Tutorial - 3 - Use the Library Browser&s File menu (or the blank document icon) to open a new model window. We will build the model by copying Library blocks into this window. The idea is to translate each equation into a sequence of blocks, and to hook them together in the
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This note was uploaded on 01/28/2012 for the course ECH 157 taught by Professor Palagozu during the Fall '08 term at UC Davis.

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Lecture_F11_ECH157_S - ECH 157 A Simulink Tutorial This tutorial exposes you to the main ideas youll need to use Simulink in ECH 157 A tutorial

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