The heating capacities, power consumption, COP of
three refrigerants presented an analogous relation during
the whole heating process with the growth of time.
When heating capacities decreased with the increased
of outlet water temperature, power consumption
increased in opposite, which resulted in COP dropping
gradually. Meanwhile, CO2 presented poor performance
due to its high presser drop. So, it is suggested to choose
appropriate structure for CO2 system pointedly.