A study on the performance of the airside heat exchanger under frosting in an air source heat pump water heater/chiller unit

Air source heat pump water heater/chiller (ASHPWHC) units, a cooling and heating source for buildings becomes increasingly popular. However, when such a unit is operated as a heating source under low ambient temperature in winter, the formation of frost on the surface of its airside heat exchanger becomes problematic, leading to the degradation of the heat exchangerʹs performance or even the shutdown of a unit. Therefore it is necessary to have a detailed investigation on the operational characteristic of the airside heat exchanger in an ASHPWHC unit under frosting in order to optimize its structural layout, thus increasing its energy efficiency and operational reliability.