A Model and Multi-Mode Control of a Centrifugal Chiller System: A Computer Simulation Study

In this paper, a model of a water-cooled centrifugal chiller system is developed and its control performance is studied. The overall system consists of three control loops: (i) a compressor speed control; (ii) an inlet guide vane control and (iii) a condenser liquid-level control. The model is validated by comparing the simulation results with the experimental data under steady state conditions. The results match to within 10% accuracy. A multi-mode control strategy was designed to simulate the operation of the centrifugal chiller as it transitions between start-up, speed control mode, IGV control mode and shutdown mode during a typical day operation. COP of the chiller was studied by conducting simulation runs under a wide range of operating conditions. The results showing the coefficient of performance of the system at different cooling loads as a function of cooling water temperature under IGV control mode and compressor speed control mode are presented.