Transient modeling of an air-cooled chiller with economized compressor. Part II: Application to control design

Based on the transient modeling developed in the previous paper, the control design of the air-cooled chiller is studied. The main electronic expansion valve (EXV) controls the suction superheat, the compressor controls the leaving water temperature and the sub EXV regulates the injection superheat. Since the system reliability is sensitive to the control of the suction superheat, it is the focus in this paper. Dynamic simulation cases are built to compare two control algorithms, PID and fuzzy logic. The case studies show that the fuzzy controller has higher reliability and performance. Both the two controllers are fully tested and tuned on a chiller test facility and the experiments indicate that the fuzzy controller works better as well.