Optimization Of Heat Pump Air Conditioning System For Electric Vehicle Based On Three-dimensional And One-Dimensional Coupling

Under the dual pressures of energy consumption and air pollution,low-emission and high-efficiency new energy vehicles have gradually attracted people's attention.Because of its safety and noise-free,and the advantages of zero emissions during operation,electric vehicles are the hotspot of almost all auto manufacturers.Without the residual heat of the internal combustion engine,many electric vehicle air conditioning systems use PTC to heat,which seriously affects the endurance of electric vehicles,so the energy-efficient heat pump air conditioning system is gradually applied to electric vehicles.As a key component of the heat pump air conditioning system,the in-vehicle heat exchanger requires both the refrigeration cycle as the evaporator and the heating cycle as the condenser,which requires excellent heat transfer performance.The main content of this paper is based on an electric vehicle evaporator,designed a microchannel heat exchanger,which has both condensation and evaporation performance,as an in-vehicle heat exchanger for electric vehicle heat pump air conditioning system.In a microchannel heat exchanger,the refrigerant undergoes a phase change in the microchannel for evaporation and condensation.To test the flow,phase change and heat transfer process of the refrigerant in the microchannel by experiment,the cost is difficult to achieve.Based on the theory of computational fluid dynamics(CFD),this paper writes the evaporation and condensation phase transition UDF based on Fluent software,and selects the appropriate turbulence model and multiphase flow model to establish the three-dimensional simulation calculation model of the evaporator.In order to ensure the accuracy of the simulation calculation,the experimental data of the evaporator was used to verify the 3D simulation model by comparing with the simulation results.On the basis of the original heat exchanger,a variety of shapes of spoiler structures were designed for the microchannels,and the heat transfer performance of different structures in the evaporation and condensation conditions was investigated.Further explore the size of the spoiler structure,the effect on the evaporation performance and condensation performance of the heat exchanger.Considering the heat exchanger as a heat pump air conditioner,condensation performance and evaporation performance are indispensable.Finally,the spoiler structure with good evaporation performance and the spoiler structure with good condensation performance are combined to analyze the heat transfer performance and select the best combination structure.Improving the performance of the heat exchanger,the ultimate goal is to improve the performance of the electric vehicle heat pump air conditioning system.Based on the three-dimensional calculation results of the original heat exchanger and the improved heat exchanger,a one-dimensional simulation model of the air conditioning system was established to analyze the performance of the air conditioning system under different compressor speed,external ambient temperature and condenser air volume.Under refrigeration conditions,the compressor system power and cooling power of the improved system are improved compared with the original system,but under some conditions,the improved refrigeration COP is not as good as the original type.Under the heating condition,the compressor system power,heating power and heating COP of the improved system are higher than the original type.The electric vehicle air conditioning system is mainly controlled by the compressor speed.Based on the calculation formula of the air conditioning load,based on the reasonable assumptions,the air conditioning heat load is a function of the external environment temperature and the vehicle speed.According to the one-dimensional simulation calculation results of the air conditioning system,a binary nonlinear regression model and a BP neural network model are established.The optimal temperature of the compressor is predicted by the external environment temperature and the vehicle speed,so that the temperature inside the vehicle is maintained at the set comfortable temperature.