An experimental study on energy-storage based defrosting performance of an air source heat pump system with a micro-channel heat exchanger as outdoor coil

Abstract

For air source heat pump systems used for indoor space heating in cold areas, when the surface temperature of the outdoor coil is lower than the dew point temperature of the air and the freezing point temperature of the water, the metal surface of the outdoor coil will frost. The formed frost layer affects the normal operation performance of the air source heat pump system and reduces the energy efficiency, so the periodic reverse cycle defrosting becomes very necessary. Since the studies on defrosting performances of air source heat pump systems with micro-channel heat exchangers as outdoor coils were insufficient, especially for those coupled with energy storage technology, this study investigates the energy-storage based heating and defrosting performances of an air source heat pump system with a micro-channel heat exchanger as its outdoor coil. Based on the experimental results, the defrosting efficiency of the experimental air source heat pump system was quantitatively evaluated. The results show that the defrosting energy amount from the compressor decreased by 55.8%, and the defrosting energy consumption for evaporating frost and heating ambient air decreased by 25.0% and 64.9% when the energy storage unit was employed. Besides, the defrosting period decreased by 43.9%, and the defrosting efficiency increased by 7.72% when the energy storage unit was employed. The results of this study are meaningful for the optimization of the air source heat pump system used in cold regions.