| Facing the dual problems of energy exhaustion and emission pollution,countries around the world are promoting policies to encourage new energy vehicles to replace traditional fuel vehicles.However,new energy vehicles have been frequently reported due to accidents such as combustion and explosion of battery modules in recent years.The safety of power batteries has attracted the attention of relevant departments and industries once again.The safety of power batteries is closely related to the working temperature of the battery.The temperature management of the battery is the key technology to avoid and alleviate the thermal safety problem.In order to solve the thermal safety problem of the battery,heat transfer performance of the battery thermal management system was studied from the perspectives of the battery thermal management structure and the battery thermal management heat transfer working fluid,respectively,combined with simulation and experiment.The main research contents and conclusions are as follows:（1）Aiming at the thermal safety problem of battery monomer,a battery thermal management structure with integrated heat pipe and cold plate（IHPCP）was designed,and the model was established and calculated by COMSOL 5.5 software.The influence of the number of heat pipes distributed in the cold plate n,the ratio of the plate runner width to the thickness of the heat pipeω,and the ratio of the thickness of the cold plate to the battery thicknessζon battery temperature rise and temperature distribution were studied.The results show that the heat exchange performance of the battery thermal management system was the best when n=4 in the range of 0 to 4.When n=4 and Re=100,the maximum dimensionless temperature and the dimensionless temperature difference of the battery were decrease by 8.8%and 8.0%respectively,and the value of PEC was also the highest at this time,about 1.7.Theωhad a greater influence on the temperature difference between the inlet and outlet of the flow channel,Nu and PEC.With the increase ofω,the temperature difference between the inlet and outlet of the flow channel,Nu and PEC all showed a downward trend;the maximum temperature of the battery and the battery temperature difference increase with the increase ofζin the range of 0.25 to 0.5.It will gradually decrease in the range of 0.5 to 1.5.Whenζ=0.50,the maximum dimensionless temperature and the dimensionless temperature difference of the battery are the largest,that is,the cooling effect and uniform temperature effect of the heat exchange structure were the worst at this time.（2）In order to enhance the heat transfer effect of heat pipe and cold plate integrated battery thermal management system,modified silica nanoparticles for improving thermal conductivity were prepared from the heat transfer fluid of the system.Silica nanoparticles with thiol groups on the surface were prepared by sol-gel method.The electrophilic ring-opening reaction between the silica nanoparticles and dihydropyran was further carried out under the catalysis of Lewis acid to generate silica nanoparticles with alkane chains.The alkane chains contained 1,3-dicarbonyl functional groups,which could effectively coordinate with metal nanoparticles.Si O2-SH-DP nanoparticles with alkane chains were reacted with copper acetylacetonate to form Si O2-SH-DP-Cu nanoparticles with copper nanoparticles embedded on the surface.The morphology characterization of the three kinds of nanoparticles shows that the surface of the modified Si O2-SH nanoparticles is smoother and has no pore structure.The morphology of Si O2-SH-DP nanoparticles modified by organic binder has no obvious change,and the surface is smoother.The surface of Si O2-SH-DP-Cu is rough and the diameter increases slightly.At the same time,XPS and other test results also verified that alkane chains were connected to the skeleton of silica,and copper was also successfully connected to the modified silica.（3）Appropriate deep eutectic solvent was selected as the base solution,and three kinds of modified silica nanoparticles were dispersed into the base solution to prepare nanofluids.The static thermophysical parameters such as thermal conductivity and viscosity of nanofluids were explored,and convective heat transfer experiments were carried out on EG/Ch Cl based nanofluids with good performance.According to the physical parameters of the existing single battery,battery thermal management system and nanofluid,a thermal management system model based on nanofluid battery is established,and its influence on the heat dissipation performance of the thermal management system is simulated and analyzed.The results showed that due to the hydrogen bond between the nanoparticle and the solvent,the hydrogen bond association between the solvent molecules is broken,and the viscosity of the nanofluid decreases within a certain range.The thermal conductivity of the eutectic solvent-based nanofluid dispersed with Si O2-SH-DP-Cu can be increased by 13.6%at the maximum.The results of convective heat transfer experiments showed that the addition of nanoparticles can increase the convective heat transfer coefficient of the flowing working fluid by up to 24.9%.In addition,compared with the base fluid without nanoparticles,the maximum temperature of the battery can be reduced by5.1%under the heat transfer of Si O2-SH-DP-Cu nanofluid.This paper has 32 figures,6 tables and 127 references. |
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