Design And Optimization Of Heat Pump Air Conditioning Heat Exchangers For Electric Vehicle

As energy and environmental pollution problems are increasingly brought to the attention of the people,the power source of automobiles has gradually begun to develop from traditional internal combustion engines to new types of electric drive machines.In the process of the development of electric vehicles,there will be many problems that the traditional internal combustion engines do not have.It is the existence of these problems make the electric car is not very popular.This article mainly aims at the problems existing in the electric car heat pump air conditioning system and designs and optimizes key parts.The most critical components of an electric vehicle heat pump air conditioning system include heat exchangers,compressors,and electric motors,and the heat exchangers have the most direct and important impact on the air conditioning system.In order to effectively reduce the energy consumption of the electric vehicle heat pump air-conditioning system and the number of heat exchangers,this article is ready to design a heat exchanger that can meet the dual purpose of evaporation and condensation.At present,the commonly used car heat exchangers are mainly composed of parallel flow evaporators and condensers.Therefore,they are optimized mainly from the louver fins and the fluid flow channels.The structure of the louver fins has a great influence on the performance of the heat exchanger,such as the fin angle,fin thickness,wave length and wave height of the heat sink,therefore,the influence of these parameters on the heat transfer performance of the louver fins needs to be studied.However,phase change occurs during the working process of the automotive heat exchanger,it is not only a large amount of computation,but also difficult to guarantee the accuracy of direct numerical simulation.Therefore,based on a model of a vehicle water radiator,the numerical calculation of the louver fins is calibrated based on the experimental values,and the appropriate turbulence model and wall functions are determined as the reference model for the subsequent simulations.After determining the appropriate turbulence model and wall function,the effects of the window opening angle of the blind,the wave length of the heat sink and the wave height of the heat sink on the heat transfer performance of the heat exchanger were studied respectively.It was found that when the window opening angle of the shutter is in the range of 18?30°,the air flow resistance gradually increases with the increase of the angle of the window,and the heat transfer performance increases first,then decreases,and there is a peak.When the wave length of the heat sink is 1.8mm?2.3mm,the air flow resistance gradually decreases as the wave length increases,and the heat transfer performance also gradually decreases,but the heat exchange performance will be maintained when the wave length is reduced to a certain value.When the wave height of the heat sink is 7.0mm?8.6mm,the air flow resistance gradually increases as the wave height increases,but the flow resistance will remain unchanged when the wave height reaches a certain value,and the change trend of the heat transfer performance is basically the same as the flow resistance.For the design optimization of the flow path of the refrigerant fluid,this paper first determines the operating conditions for the evaporation and condensing conditions as a reference input boundary condition for subsequent calculations and analyze the performance of traditional porous flat tube structure under evaporating conditions and condensing conditions.The relationship between the amount of phase change produced by the refrigerant and the structure of the refrigerant is mainly investigated.It is found that the conventional porou's flat tube is more conducive to the evaporation of the refrigerant due to its regular geometric shape along the flow direction,and the condensation is not effective.According to the analysis results,the improvement direction of the new structure is proposed,and a total of two new structural improvements are proposed.One idea is to optimize the rectangular rectangular cross section of the rectangular flat tube with a transitional arc on the basis of maintaining the original structure.Considering the effect of the surface with depressions on the evaporation and condensation performance,after calculation and analysis,it was found that the improved new structure was inferior to the original structure in terms of evaporation performance and condensation performance.After analyzing the reasons,a second improvement idea was proposed.Based on the original structure,a flow structure such as a pit is arranged on the fluid passage in the flow direction of the refrigerant,and the influence of different flow structures on the evaporation and condensation performance is examined.Evaporation and condensation simulations were performed on different structures under the same boundary input conditions.The calculation results show that the rectangular structure of the original structure has a great advantage over other structures for the evaporation performance,and for the condensation performance,the structure with round pits is superior to other structures.Taking into account the above factors,a flat tube channel structure for evaporation and condensation is proposed.