Modeling and control of a real time shell and tube heat exchanger

Abstract

Process industries generate large amount of heat that needs to be transferred. Shell and tube heat exchangers are extensively used in industriesfor utilization of the heat energy generated from different processes. For definite utilization of this energy, the temperatures of the hot and coldfluids passing through the heat exchanger should be monitored and controlled efficiently. A proper model of heat exchanger is required for thepurpose of monitoring and control. The objective of the paper is to mathematically model the heat exchanger using system identification methodsand experimentally evaluate the effectiveness of two PID controller tuning methods such as Internal Model Control (IMC) and relay auto-tuningfor temperature control. The Auto Regressive–Moving-Average model with eXogenous inputs (ARMAX) model of the heat exchanger is obtainedfrom the Pseudo Random Binary Signal (PRBS) experiment performed on the heat exchanger system. The outlet temperature of the cold fluid isconsidered as the controlled variable. Based on the obtained model, PID settings are designed using the two tuning methods, and the closed loopresponses such as servo and regulatory are compared experimentally. It is seen from the experimental results that the IMC based controller showsbetter results than the relay auto tuning method in terms of time integral error (i.e., ISE and ITAE).