INVESTIGATION OF THE EFFECTS OF THERMOSTATIC AND ELECTRONIC EXPANSION VALVES ON THE STEADY-STATE AND TRANSIENT PERFORMANCE OF COMMERCIAL CHILLERS

This paper investigates the steady-state performance and transient response of a commercial fixed-speed on-off controlled chiller and presents comparative performance results obtained during operation with a thermostatic and with an electronic expansion valve. The aim was to establish the effect of the two valves on the transient and steady-state performance of the chiller and to quantify the effects of on-off cycling losses during part-load operation. The results indicate that the chiller has a very fast response during start-up and that cycling losses are very low. The thermostatic expansion valve gives a slightly faster response than the electronic expansion valve with the penalty, however, of less stable operation with larger superheat oscillations at steady-state conditions.