Research On Temperature Uniformity Of Heat Dissipation Microchannel For High Power Density Automotive Power Module

Power modules were widely used in various fields of energy transformation by virtue of their unique advantages.As the core component of power conversion of new energy vehicles,the power module directly affected the power release speed and charging performance of new energy vehicles.With the increase of power density,the power module's requirements for heat dissipation become stricter.Liquid-cooled microchannels with strong heat exchange capability can be used for heat dissipation of high-power density power modules,but liquid-cooled microchannels had the problem of uneven heat dissipation in the flow direction.Excessive temperature gradients and local high temperature hot spots caused by uneven heat dissipation under complex working conditions will affect the thermal reliability of the power module.Long-term operation will cause fatigue,aging and degradation of the heat dissipation capacity of the power module solder layer and Its irreversible failure Therefore,it was of great significance to improve the temperature uniformity of microchannel for high power density power modules.Based on the enhanced heat transfer technology of microchannels,this thesis designed and manufactured reverse oblique truncated microchannel,and analyzed and optimized the structure through experimental testing,numerical simulation and multi-objective optimization methods to study the flow of reverse oblique truncated microchannel,Heat transfer characteristics and wall temperature uniformity.The main contents in this thesis were as follows:(1)By analyzing the basic structure,power loss and heat dissipation mode of the power module,combined with the liquid-cooled microchannel heat dissipation theory,a microchannel heat dissipation model for the power module was constructed to provide a theoretical basis for the subsequent microchannel structure design and optimization.(2)Through the microchannel heat dissipation experiment,it was found that the variable cross-section reverse oblique truncated microchannel had stronger heat transfer energy and uniform heat dissipation than the rectangular straight channel,and the local hot spot temperature on the wall of the reverse oblique truncated channel was lower than the rectangular straight channel and moved forward from the downstream of the channel to near the middle.Increasing Re significantly enhanced the heat transfer capacity of the reverse oblique channel and improved the temperature uniformity of the wall.In addition,the uniformity of the wall decreased with the increase of the external thermal load.Therefore,it was necessary to improve overall heat dissipation capacity and improve the heat dissipation uniformity,for the high power density power module heat dissipation microchannel.(3)Through grid independence verification and experimental model verification,the appropriate grid size and reliable simulation method were determined.When the oblique intercept number was fixed,reducing the intercept angle,increasing the intercept or decreasing the intercept interval can strengthen the heat transfer and increase the wall surface temperature of the reverse oblique intercept microchannel,and the pressure drop was small.Increasing Re can significantly improve the heat dissipation capacity and wall temperature uniformity of the reverse oblique truncated microchannel under various structural parameters,but the pressure drop increased significantly.Increasing Hc/Wc can strengthen the heat dissipation capacity and wall temperature uniformity of the reverse oblique microchannel,and the pressure drop was reduced.Reducing Wc/Wf can also improve heat dissipation capacity and wall uniformity,but the pressure drop increased.(4)Through multi-objective optimization of the wall junction temperature,pressure drop and temperature difference of the reverse oblique truncated microchannel,a reverse oblique truncated microchannel with low wall junction temperature,small pressure drop and uniform heat dissipation was designed.Compared with the model before optimization,the wall junction temperature of the reverse oblique truncated microchannel after optimization was 323.33K,the reduction rate was 0.75%,the inlet and outlet pressure drop was 2698.88pa,the reduction rate was 6.72%,and the wall temperature difference was 10.50 K,the reduction rate was 17.52%.