To solve the problem that frosting leads to lower efficiency of the heat pump air conditioner for electric vehicle in the heating process

a new method of composite defrosting is proposed after analyzing the deficiency of the existing defrosting method.At the beginning of the defrosting

firstlyenter the bypass defrost stage. Then reverse cycle defrost stagetimelyaccording to the defrost state.An electric bus air conditioning system with a rated power 8.0 kW was transformed

and the comparative test was carried out in the simulated environment of the outdoor at (2±0.5) ℃

the indoor at (20±0.5) ℃ and the relative humidity of (80±5)%. The change of the compressor suction and discharge pressure

the outdoor heat exchanger temperature

indoor temperature and power consumption were measured. The experimental results indicated that

compared with the method of reverse cycle defrosting

the compressor shock of discharge and suction was reduced

the fluctuation of indoor temperature was decreased and energy consumption decreased by 8.13%; compared with the method of hot-gas bypass defrosting

the time of defrosting was decreased by 60 s and energy consumption decreased by 6.56%.