Research On Characteristics Of Heat Pump Air Conditioning System For Pure Electric Vehicle

Electric vehicle has become a hotspot due to its advantages of low noise,low emission and high energy efficiency under the background of global environmental degradation and serious energy crisis.Compared to the traditional fuel vehicles,pure electric vehicles can not use the engine waste heat for heating in winter.So we need to design a two-way heat pump air conditioning system including cooling and heating.At the same time,the system also takes into account the battery cooling and motor waste heat recovery.At last,the heat pump air conditioning system is more concerned about energy efficiency while considering the mileage of electric vehicles.The main research contents and results are as follows:(1)The temperature characteristic of the battery and motor is studied,and calculating heat load of the vehicle.(2)A steady-state simulation model of pure electric vehicle heat pump system and its main components was established.And its accuracy is verified,the average relative error of heat transfer within ± 15%,in line with the accuracy requirements.As a result,the model can be used to predict and analyze the steady state operating point.(3)Taking into account the frosting and heat transfer capacity of outdoor heat exchangers in winter.Compared the thermodynamic properties of microchannel parallel flow heat exchanger and small diameter finned tube heat exchanger.The steady state model was established and compared the experimental results,the results show that the heat transfer capacity of parallel flow heat exchanger is better than that of small diameter fin tube heat exchanger,which increased by 3%-8% as condenser,11.5%-17.5% as evaporator.(4)Design and build pure electric vehicle heat pump system platform.In order to explore the performance of the heat pump system,the experiments in both cooling and heating are carried out including the optimal refrigerant charge test,the optimal expansion valve opening test,refrigeration performance test,heat pump test based on motor heat recovery and the variable speed test.It shows that the optimal charge amount of system without heat recovery from motor is 660 g,and 800 g with heat recovery from motor,and there is an optimal expansion valve opening to obtain the optimal COP regardless of cooling or heating;the heat pump system can significantly improve the heat and efficiency of the heat recorvey heat pump.The heating capacity increases with the increase of the speed of the vehicle,the power of the compressor is reduced,and the COP is greatly increased.(5)Experimental test for vehicle,run the system at different ambient temperatures for 30 minutes,at heating mode,the maximum heating capacity is 4901 W,COP is 1.86;at cooling mode,the cooling capacity is 5336 W,COP is 1.6.Both of them are in line with system requirements.