Determination Of Heat Transfer Characteristics Of Insulating Cooling Fluid For New Energy Vehicle With In-wheel Motors

In-wheel motor technology is a new-generation drive technology for new energy vehicles.It has the characteristics of high integration and light weight,which can achieve higher energy-saving levels and increase vehicle body space utilization.It is a very competitive new energy vehicle drive technology.However,problems such as difficulty in heat dissipation and overheating caused by high integration are the bottleneck restricting the application of in-wheel motor technology.Conventional aircooling and water-cooling technologies may have insufficient cooling capacity or defects of their own weight and large volume,and cannot meet the technical requirements of high integration and efficient cooling at the same time.The currently developed high-performance cooling technology adopts direct immersion boiling cooling for electronic control components,which can realize the integration of electronic control and cooling systems.Since the submerged cooling is used,the heating electronic device and the cooling medium are in direct contact,so the cooling medium with electrical insulation should be selected.At the same time,the cooling system inevitably runs under different climatic conditions and vehicle driving modes,so mastering the phase change heat transfer characteristics of the cooling fluid under complex working conditions is an important basis for the development of this technology.This article plans to select the Novec 7100 series of insulating electronic fluorinated liquid produced as the cooling medium,and to study the specific heat transfer characteristics of Novec 7100.This paper designs and builds an experimental device that can be used for steady-state pool boiling at different saturation temperatures.The experimental device is divided into inner and outer layers.The inner layer can be evacuated and the outer layer is surrounded by a constant temperature water bath.The temperature of the inner working fluid can be adjusted,and the steady-state pool boiling experiment can be carried out under different saturation pressures.In this thesis,the steady-state pool boiling experiment of Novec 7100 working fluid on the smooth copper surface was carried out at different saturation temperatures,and the boiling process was synchronously observed and recorded by an industrial high-speed camera.In order to obtain the effects of saturation pressure and surface inclination on the boiling heat transfer performance of Novec 7100 working fluid pool,and to provide data support for its use as a cooling medium for in-wheel motors of new energy vehicles,this study was carried out at different saturation temperatures(-15～60 ℃)working conditions and different surface inclination angles(0°-up,90°-vertical)observed the steady-state pool boiling heat transfer of Novec 7100 working fluid on a smooth copper surface,the results show that the heat transfer coefficient of nucleate boiling and the critical heat flux(CHF)decreases with decreasing saturation temperature.The nucleate boiling heat transfer coefficient increases with the inclination angle at low superheat,but decreases at high superheat.CHF decreases with increasing surface inclination.At the same time,the experimental data were compared with the CHF prediction model established by Zuber(1958),the pool boiling heat transfer prediction model established by Rohsenow(1952)and the estimated value of the heat transfer coefficient prediction model established by Kutateladze(1948).The overall trend of the values is consistent.