Question

15.3 A conventional controller is to be used in the scheme shown below in Figure P15.1 for controlling the exit temperature of the industrial heat exchanger first introduced in Problem 14.2. Assuming that Tz, the brine temperature (in °C), remains constant, the transfer function relations for the process have been previously given as: 1 -0.5e-10* (40s I)(15s)(BB (P14.3b) Assume that the valve dynamics are negligible. (a) Use the provided model in a control system simulation package to obtain a process reaction curve; use this process reaction curve to design a PI controller for th is process based on: 1. 2. 3. The Ziegler-Nichols approximate model tuning rules The Cohen-Coon tuning rules The IMC approximate model tuning rules (Improved PI) Chilled Brine TC Ti.F Heat Exchanger T, F Feed Stream Chilled Brine Out Figure P15.1 (b) Using each of the PI controllers designed in part (a) in tum, obtain the overall closed-loop response of the heat models given in Eq. (P14.3)) to: exchanger system (using the actual transfer function a+1°Cexit temperature set-point change 2. 1. a +2°C change in the inlet temperature In each case briefly evaluate the performance of each of the three PI controllers. If you had to recommend one controller for use on the actual process, which one would

Answer 1