Cascade control for a steam-heated double-pipe heat exchanger

The goal of this thesis is to create the experimental setup and the necessary instrumentation for the temperature control of a double-pipe heat exchanger. The heat exchanger, located at the Chemical Engineering Control Laboratory at the California State University, Long Beach, has been used in the past for temperature control experiments, in which the manipulated variable was the incoming water flow. In the control experiments performed for the current work, the manipulated variable is the incoming steam pressure. For this purpose cascade control has been used, with an inner loop controlling the steam pressure setpoint, and an outer loop controlling the water outlet temperature. Despite major fluctuations in the steam pressure supply and inappropriate sizing of a control valve, the experimental results show that the designed cascade control can track the temperature setpoint and reject load-induced disturbances satisfactorily. System parameters are obtained via experimental modeling through open loop experiments. A LabView-based data acquisition and control program has been written and implemented for acquiring and processing sensor outputs, and for providing control commands to the final control elements. Several controller parameter tuning methods, such as IMC, ITAE, Cohen-Coon, and Ziegler-Nichols, were implemented and evaluated experimentally through a set of performance indices.