Impact of hot water temperature on the performance of cascade heat pump system

Presents the operation principle of the system. By the analysis of experimental data under different conditions, including different environmental conditions with the same hot water temperature and the same environmental condition with different temperatures of hot water, finds that the cascade heat pump can operate stably in the extreme low ambient temperature of -25 ℃. The system can generate hot water with temperature 80 ℃, and the system COP reaches 1.55. The highest water temperature available by the system is 85 ℃. Compared with the traditional single stage heat pump unit, the traditional heat pump unit is more efficient to produce hot water around 65 ℃, when the ambient temperature is higher than 10 ℃.