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 industries for utilization of the heat energy generated from different processes. For definite utilization of this energy, the temperatures of the hot and cold fluids passing through the heat exchanger should be monitored and controlled efficiently. A proper model of heat exchanger is required for the purpose of monitoring and control. The objective of the paper is to mathematically model the heat exchanger using system identification methods and experimentally evaluate the effectiveness of two PID controller tuning methods such as Internal Model Control (IMC) and relay auto-tuning for temperature control. The Auto Regressive-Moving-Average model with eXogenous inputs (ARMAX) model of the heat exchanger is obtained from the Pseudo Random Binary Signal (PRBS) experiment performed on the heat exchanger system. The outlet temperature of the cold fluid is considered as the controlled variable. Based on the obtained model, PID settings are designed using the two tuning methods, and the closed loop responses such as servo and regulatory are compared experimentally. It is seen from the experimental results that the IMC based controller shows better results than the relay auto tuning method in terms of time integral error (i.e., ISE and ITAE).