Research And Optimization On Performance Of Heat Pump Air Conditioning System For Pure Electric Vehicles

Based on prophase experimental and theoretical research, and combined with a certain type of pure electric vehicle, a heat pump air conditioning system with low pressure gas-mixing for pure electric vehicles is developed through design calculation and system analysis, and set up the test bench to carry on the experiment study. Through the results analysis of the standard cooling, high-temperature cooling and heating conditions in different compressor speed and air output of the car fan, shows that the system is not only reasonable in design and matching, but runs Efficiently and stably. In standard cooling condition, the cooling capacity of the system can reach 3456 W and COP is 1.68; in high-temperature cooling, the cooling capacity can reach 3329 W and COP is more than 1.5; in test conditions to heat, the system can operate stablely and is more efficient compared to the PTC electric heating system which efficiency value is lower than 1.0. When the ambient temperature is-15℃, the heat capacity can reach 3085 W, and the heating efficiency is 1.85.The system of test-bed experime is optimized and improved, then installs the new system in the vehicle to carry out experimental and research the performance of the system. The results show that the heat pump system in the vehicle can operate stably under the condition of cooling and heating, and can meet the safety and comfort requirements of the members in vehicle basically. In 38℃ cooling conditions, the head and foot lowest temperature can reach 18.5℃ and 23℃ of the seat in front, the lowest average temperature reached 21.5℃ of the members in the back seat, through adjust compressor speedand and the superheat of main valve and gas-mixing valve. In heatingconditions, the foot temperature of the seat in front and the average temperature in the back seat of blowing foot mode are higher than that of blowing face mode. So the blowing foot mode is more suitable for winter heating air. When the ambient temperature is-5℃, the foot highest temperature of the seat in front reachs 31.7℃ and the average temperature in the back seat can reach 22.6℃.When the ambient temperature is-15℃,the foot highest temperature of the seat in front reachs 15.2℃ and the average temperature in the back seat can reach 10.4℃. PTC electric heating can be used to meet the requirements of thermal performance and comfort of the vehicle. In addition, in the vehicle air conditioning system test researches find that the system has problems of poor efficiency when compressor at low speed and problems of the crews’ different parts have large temperature difference at the same model. Besides the reseaches lay the foundation for further research and improvement and provide experimental basis for the vehicle heat pump system research.