Based on the operation testing of new air-water double source composite heat pump system (AWDSHPS-N)

three defrosting modes were investigated under the same ambient condition

which included the condenser outlet refrigerant recooling defrosting(D-I)

the low temperature-hot water defrosting(D-Ⅱ)

the condenser outlet refrigerant recooling and low temperature-hot water defrosting at same time (D-Ⅲ). Total coefficient of performance (COP) of AWDSHPS-N was used to evaluate the influence of the three modes. The influence on the total COP

defrosting operating characteristics and energy consumption of D-I

D-Ⅱ and D-Ⅲ were discussed and compared with those in the reverse-cycle defrosting mode

under the same ambient condition. The results of test conditions indicated that for D-I and D-Ⅱ

the total COP can be decreased by 0.42% and 3.93%

respectively

compared with the COP of frosting period. The heating power and COP during D-Ⅱ defrosting were 27.4% and 17.8% higher than those of frosting operation

respectively. The total COP of AWDSHPS-N choosing D-I

D-Ⅱ and D-Ⅲ were 26.06%

29.79% and 17.02% higher than that of verse-cycle defrosting

and the defrosting energy consumption of D-I

D-Ⅱ and D-Ⅲ were only 3.11%

34.78% and 28.26% of the reverse-cycle defrosting energy consumption.