Heat pump water heaters are more energy efficient than the conventional ones using electricity or gas. A wrap-around micro-channel condenser was proposed to reduce the system charge of refrigerant

improve the heat transfer efficiency

reduce cost of heat pump water heaters

and improve safety. A quasi-steady-state system modeling approach to performance simulation of the air source heat pump water heater using wrap-around micro-channel condenser was developed. The refrigerant components were described by steady-state models

while the water tank was described by a dynamic lumped-parameter model. The model was well validated with the laboratory test data of the dynamically cumulative power consumption

time-variant water temperature rise

and the overall time-average COP of heat pump water heaters. Parametric analysis revealed that the insulation layer of water tank can reduce the heating time and improve the system COP around 9.2%

while a bigger condenser can improve the system COP but has negligible impact on the heating time. At last

pass number of the micro-channel condenser was optimized and three-pass design were recommended for higher performance and less chance of refrigerant maldistribution.