Study of CO2 transcritical cycle heat pump water heater

A CO2 transcritical cycle heat pump water heater was set up and the experiments were conducted in this study. The efficiency of the CO2 compressor is calculated based on the testes data, the water heater was tested at different operating conditions. The results show that the efficiency of system increases when the temperature of ambient become higher and inlet water temperature keeps constant, so the system can get high efficiency at the warm season when more hot water is needed for residents. COPh (coefficient of performance of heating) of heat pump system can reach 3.0 when the outlet temperature of water is 60 degrees C. The higher inlet temperature of water is not good for performance of CO2 transcritical cycle heat pump, so the straight flow type water heater can help to get higher COPh. In this paper, it is found that the COPtotal of system can reach above 5.0 when both refrigeration and heating water can be utilized at the same time. But the operation condition must be control and the system should be redesign for application.