Improved energy performance of air-cooled chiller system with mist pre-cooling

This study investigates how to lower the dry bulb temperature of outdoor air via mist pre-cooling to enhance the coefficient of performance (COP) of an air-cooled chiller system. Based on standard chiller models in commercial simulation software DOE-2E, a modified model was made to analyse how the chiller COP varies under two different condensing temperature controls with mist pre-cooling of air entering the air-cooled condenser. Drawing on the model calibrated by manufacturer and operating data, it was estimated that around 18% decrease in the electricity consumption could be achieved by coupling floating condensing temperature control with an optimal mist generation rate, with regard to a chiller system serving a hotel in a sub-tropical climate. Remarks have been made on how optimal mist control can be implemented to maximize electricity savings while reducing surplus mist carrying over the condenser coil.