| Nowadays,environmental and sustainable development has become a primary rhythm.Electric vehicle(EV)owned unique characteristic such as zero emission,minor pollution and so on,receiving widely advancing and pushing.Power battery have been only dynamic resource of EV and used commonly type of lithium-ion battery.Single cell cannot satisfied the driving requirements in the automobile,so it is available for electric vehicle unless being a module across series and parallel connection.Because of the existence of internal resistance and often ran at different working conditions,battery would generate large heat,further rising the temperature of cell.However,it is widely acknowledged that the optimal temperature ranges from 25℃ to 40℃ and then the surface temperature difference below 5℃.As far as lithium battery higher or lower temperature have an irreversible effect.Some special working conditions such as quick charging-discharging,high ambient and large current discharging are aggravated heat generation and greatly rise temperature of cell.In this point,lots of problems like capacity declining,life reducing as well as thermal control away will be accident.So a suitable heat dissipation way can effectively throw away it,securing battery working at the optimal temperature.In present,liquid cooling should be recognized such a method due to its advantages that has higher heat transfer coefficient and greater miniature spatial arrangement.Meanwhile,introducing mini-channel and flow boiling technology in liquid cooling system makes it get greater heat transfer performance.Firstly,this paper expose the background and sense why need to study power battery cooling technique,heat dissipation method that is usually employed in modern vehicle,and liquid cooling system research status at home and abroad.Next,it can be explained about the structure,heat generation and transfer mechanism for the object lithium-ion battery.Moreover,in order to provide data support for the later work,there also introduce calculation formulation related to the major thermal performance parameters.A based-on cold plate indirect cooling system that is used to absorb heat which is generated by cells can be designed and constructed.Under three discharging rate 1C,3C and 5C,the effect of thickness of cold plate to peak temperature and maximum temperature difference on the surface of battery,also the influence of pressure drop of coolant inlet and outlet can be study through numerical simulation.According to the results analysis would harvest an excellent thickness of cold plate.Subsequently,this system its cold plate has experienced optimizing stage will be further research aiming at the relationship of cooling system as coolant temperature and mass flow rate.Before the calculation of liquid cooling as foundation,added mini-channel to enhance heat transfer designed a mini-scale cooling system.Placement modes,ambient temperature,coolant inlet temperature and velocity can be investigated focused on the influence in the battery peak as well as distribution of temperature.Then the change of the width and height of the channel to the heat transfer and pressure drop performance of the cooling system is analyzed in rest part in the section.Ultimately,carrying out some preliminary study is expected to explore the application of mini-channel flow boiling in the battery thermal management system.Simplified the heat generation rate of cell as constant heat flux,along with create 3D geometry model.Numerical simulation can be used to analyze the variation of heat transfer performance that has been produced by those influence factors heat flux,inlet subcooled of coolant as well as inlet velocity via both VOF multi-phase flow and Lee phase change model. |
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