152A_Quiz_2

152A_Quiz_2 - introducing a step change of 10% in an input...

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Department of Chemical Engineering University of California, Santa Barbara Ch.E. 152A Fall, 1999 QUIZ 2 Problem 1 (20 points) The dynamic model between an input variable x and an output variable y can be expressed as 2 d y d 2 t + 3 dy dt + y ( t ) = 4 dx ( t 2) dt x ( t 2) Briefly justify your answers to the following questions: a. Will this system exhibit an oscillatory response after an arbitrary change in x? b. What is the steady-state gain? Problem 2 (20 points) Consider the temperature control system for the shell and tube heat exchanger shown on page 331 of your textbook. Both the temperature transmitter and the I/P transducer are direct- acting devices. Briefly justify your answers to the following questions: a. Do you recommend using an air-to-open or an air-to-close control valve? b. If an air-to-open control valve is used, should the PID controller be direct acting or reverse acting? Problem 3 (30 points) Four process reaction curves are shown in Figures 1a - 1d. Each one was obtained after

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Unformatted text preview: introducing a step change of 10% in an input variable. Suggest the form of a reasonable transfer function model for each of the four processes. It is not necessary to actually determine the numerical values of the model parameters. Problem 4 (30 points) A control valve is placed in series with a heat exchanger, as shown in the schematic diagram below. The following information is available: 1. The pump discharge pressure, P 1 , remains constant at 45 psig; pressure P 2 is constant at 0 psig. 2. The specific gravity of the liquid flowing through the line is 1.0. 3. At the nominal operating conditions, the valve stem position is l = 0.5, the flow rate is q = 160 GPM, and the pressure drop across the control valve is P v = 16 psig. 4. The pressure drop across the heat exchanger, P he , is proportional to q 2 . 5. The control valve has quick opening trim. What is the flow rate q when the valve position is l =0.4?...
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This note was uploaded on 07/12/2009 for the course CHE 162A taught by Professor Seborg during the Fall '08 term at UCSB.

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152A_Quiz_2 - introducing a step change of 10% in an input...

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