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.