Experimental Study on Air-source Heat Pump Water Heater with Vapor-liquid Adjustment Evaporator

A vapor-liquid adjustment evaporator exhibits superior heat transfer performance by adjusting vapor quality and mass flux. In this study, two vapor-liquid adjustment evaporators with circuitries of 4-2-4-6-4(evaporator 1) and 5-4-3-4-4-4(evaporator 2) are applied to heat pump water heaters(respectively referred to as systems A and B), and an experimental comparative study is conducted. The results show that compared with that in evaporator 1, the refrigerant is more uniformly distributed in evaporator 2, and its pressure drop is reduced by 10.91%. Under nominal working conditions, the heating capacity and power consumption of system B are reduced by 1.69% and 1.45%, respectively, compared to system A; the coefficients of performance(COPs) of the two systems are generally the same. The pressure at the compressor outlet of system B is 26.35-84.78 kPa lower than that of system A; this range is conducive to the safe operation of the compressor. At different ambient temperatures, the power consumption of the compressor of system B is lower than that of system A. When the ambient temperature is 30 ℃, the COP of system B is 2.1% higher than that of system A.