Research On Performance Of Air Conditioning System For Electric Vehicle With Low GWP Refrigerant

In recent years,as the future development direction of automobile,electric vehicle(EV)has become increasingly popular in recent years because of its advantages in energy security,environmental protection and sustainable development.Compared with traditional internal combustion vehicles,there is no engine waste heat for electric vehicle to heat the cabin.The Air conditioning(AC)systems present the highest power consumption of the auxiliary components of the EVs,and using AC system to achieve cabin thermal comfort will seriously affect the driving range of electric vehicle.Moreover,the European Union has passed regulations to restrict the use of refrigerants with a GWP higher than 150 in automobile AC systems.Because of the high GWP of R134a,the investigations on the alternative refrigerants are energetically underway.This thesis in view of the electric vehicle air conditioning system using R1234yf and R513a as alternative refrigerants,operation condition complex,winter heating system energy consumption factors such as research and development EVs designed a high efficiency heat pump air conditioning(HPAC)system.The work done in this paper is as follows:1.The AC system solutions to EVs as well as combined the thermodynamic and the application of two low GWP refrigerant(include R1234yf and R513a)are critically reviewed in this thesis.According to the recent years’ studies,R1234yf is considered as the most probable replacement of R134a in automobile air conditioning(MAC).2.The steady-state analysis method is used to calculate the heat load of the whole vehicle,and the cycle process of the HP system is also analyzed.Taking an existing HPAC system for instance,this thesis built several experiments which matched the work conditions for the EV.Then a 1-D model for AC system had been built by KULI.After1-D calculation and contrast with experiment,an acceptable result of average relative error is acquired.As a result,the model can be used to predict and analyze the optimized AC system.3.Designing and building the performance test-rig of HPAC system for EV.The components of the test-rig are selected according to the vehicle climate control load.New system is designed based on the 3-heat exchanger AC systems commonly used in fuel vehicles at present,which can test the system performance with the variation of compressor speed,environmental temperature,air speed,electronic expansion valve and different refrigerants.4.In order to explore the performance of the HP system,the experiments in cooling is carried out including the optimal refrigerant charge test,the optimal expansion valve opening test,refrigeration performance test based on the variable compressor speed and different refrigerant(including R1234yf,R513a and R134a).It shows that the optimal charge amount of system by R134a is 1100 g,by R513a is 1050g,and 1000g by R1234yf,and there is an optimal expansion valve opening to obtain the optimal COP regardless of cooling;the performance of this three systems is the best when the expansion valve opening is between 20% and 25%;the cooling capacity increases with the increase of the speed of the compressor,but COP is opposite.It is worth noting that R134a system has a best performance.5.Considering the problem of heat performance degradation of electric vehicle HPAC system at low temperature,a thermodynamic analysis model of electric vehicle HPAC system based on quasi-two-stage compression and vapor injection technology is established,analyze the impact of changes in HP system by different refrigerant.In low temperature,the performance of the improved HP system has a significantly enhance,and is more stable.Through comparison,it is found that the performance of R1234yf system has a maximum enhance by using vapor injection technology.