AUGUST 2016 – HOW TO TUNE PID LOOPS: TEMPERATURE CONTROL CHALLENGES
Temperature control applications can be broken into two main categories—fully continuous and semi-continuous (or batch). An example of a fully continuous temperature controller is a shell-and-tube heat exchanger. In this application, the exit temperature is controlled by adjusting the flow rate of heating fluid, such as steam, through the shell side. As the flow of heating fluid is increased, the temperature also increases until it eventually settles at a temperature well below that of the heating fluid. Similarly, by decreasing the flow of steam, the temperature drops. The change in steam flow impacts the final steady state temperature of the exit steam. Processes such as this are relatively easy to tune using the basic tuning rules available. How can practitioners apply these rules to tune more complex temperature applications?