Heat exchanger control: Performance of thermodynamics-based geometrical vs classical PID controllers

In this communication, a control problem based on thermodynamic principles is developed to control the output temperature of a heat exchanger in an experimental setup. The system is controlled through a nonlinear output error, which is proportional to the total entropy production within the heat exchanger. A lumped-parameter model of the heat exchanger allows to define the thermodynamic control scheme, with geometric control principles, a high-gain observer and an anti-windup scheme, which provides robustness against parametric uncertainties and disturbances. To make a comparison with classical control schemes, a Ziegler–Nichols PID controller was tuned for a First Order Plus Dead Time plant approximation. The experimental setup used a National Instruments Compact FieldPoint controller, and the control scheme was programmed in a LabVIEW interface. The performance of the proposed controller was tested under two criteria: energetic performance and total tracking control error. The results show that the classical controller has a better energy-saving performance, while the thermodynamic controller has a better tracking performance, making it more suitable for applications where temperature control needs to be more precise.