Frosting And Heating Performance Of Electric Vehicle Heat Pump Air Conditioning System In Cold Area

With the development and change of society and environment,electric vehicles have gradually become the main means of transportation.Electric vehicles do not have an engine,so the electric vehicle air conditioning system can not use the engine waste heat to achieve heating purposes,at present,electric vehicles generally use PTC system as the heating component of air conditioning.PTC system consumes a lot of electricity,which has a great impact on the cruising range of electric vehicles,and it is necessary to develop a new heat pump air conditioner as an electric vehicle air conditioning system,but the heat pump air conditioner has the disadvantage of easy frosting of outdoor heat exchangers in winter.In view of this problem,this paper determines the winter heat load of the electric vehicle air source heat pump system by theoretical calculation of the electric vehicle air conditioning system,and designs the air source heat pump air conditioning system,that is,using the original air conditioning system of electric vehicles,it is transformed into an air source heat pump air conditioning system that can be cooled in summer and heated in winter.A test bench was built to study the frosting characteristics and heating performance changes of electric vehicle heat pump air conditioning system affected by different factors in low temperature environment through experiments,and analyzed them.The main findings of this paper are as follows:(1)The ambient temperature has a serious effect on the frosting condition and heating performance of the outdoor heat exchanger in the heat pump air-conditioning system of electric vehicles.With the decrease of ambient temperature,the frosting time of outdoor heat exchanger is gradually delayed,but the frosting area is increased.Similarly,with the decrease of the ambient temperature,the heat generated by the system during the same operating time also gradually decreases.When the ambient temperature is-10℃,because the heat generated by the system is too low,it cannot meet the heating demand in the crew cabin,and other heating systems are needed to assist heating.(2)Too high or too low wind speed of the heat exchanger inside and outside the heat exchanger will affect the frosting situation of the outdoor heat exchanger of the electric vehicle heat pump air-conditioning system and the heating performance of the system,which will lead to the increase of the stable frosting area of the heat exchanger outside the vehicle,and lead to the low heating capacity of the system and the decrease of COP.(3)In low ambient humidity,due to less water vapor content in the environment,the driving force of water vapor attached to the surface of the heat exchanger outside the vehicle is weak to condense into frost,which can slow down the frost of the outdoor heat exchanger of the heat pump air conditioning of electric vehicles and improve the heating performance of the system.(4)In the low temperature environment,COP of the heat pump air-conditioning system of the electric vehicle is generally less than 1 after 600s of operation.In this case,the energy-saving advantage of heat pump system for heating in the crew cabin is no longer obvious,and other heating systems can be set for auxiliary heating in the crew cabin.