| Power battery as a source of new energy electric vehicle power,is the main energy storage component and the key part of an electric car,also is directly related to the safety of the electric car driving and dynamic performance.Currently applied in electric cars,there are many different kinds of forms of batteries,lithium-ion batteries because of its excellent power output characteristics and long life,currently various car manufacturers has widely used in the battery pack.But lithium-ion batteries also has a drawback,lithium-ion batteries is more sensitive to changes in temperature.Due to the cell body dense putting,middle area must accumulate more quantity of heat,and the edge area has less heat,which result in the in-homogeneous heat of the batteries in the battery pack monomer,makes every single battery temperature differences,this also leads to the battery module,different internal resistance and capacity.After a long time,can cause part of the battery charging and discharging,and will affect the battery's life and performance,cause potential safety hazard.So in order to prolong the service life of the battery,electric vehicle needs a good cooling system.Lithium-ion battery's ideal working status temperature range from 25 to 50 ?,the difference of the temperature between the battery module must be less than 5 ?.Due to the large capacity and high power lithium-ion battery applied more and more,and battery pack inside limited the space,the traditional cooling system can not meet the requirements of lithium-ion battery cooling.There are more and more products using liquid-cooling system.The purpose of this paper is to design a new type of micro-channel flat tube type battery cooling system.The new cooling system consists of micro-channel flat tube heat pipe and micro-channel tubes.The heat comes from the battery firstly passed to the heat pipe,heat pipe transmit the heat to the cooling pipe due to phase transformation,and the cooling pipe takes the heat out of the system.Making lithium-ion batteries and battery modules work in ideal temperature range,guarantee the ideal work for the battery pack.In this system,liquid-cooled medium using pure water.The thesis uses three design methods,theoretical calculation,star-ccm+ simulation,and experimental verification.Firstly,the temperature rise of the coolant in the liquid cooling system can be obtained through theoretical calculation.The temperature rise can be used as the theoretical basis for the convergence of the simulation software,and can be also verified whether the data measured in the experiment is accurate.Secondly,star-ccm+ was used formodeling and simulating to obtain the temperature cloud diagram distribution of the whole battery pack,the pressure cloud diagram of the coolant,the inlet and outlet water temperature data of the coolant,etc.By comparing the temperature rise of the coolant calculated theoretically and the temperature measurement point obtained in the experiment,the feasibility of the cooling system was verified.Moreover,star-ccm+ can be used to calculate different battery heating conditions and steady-state transient conditions.In the thesis,three steady-state heating conditions of the battery are calculated,which are the steady-state heating conditions of the battery at 0.5c,1C and 2C respectively.After the calculation model of steady-state heating conditions can be converged,the unsteady-state heating condition of batteries at 2C is calculated.Where C represents the capacity of the battery,charging time of0.5c,1C and 2C is 2h,1h and 0.5h respectively.Experimental verification is to make a trial-produce model,carry out experiment and verify theoretical calculation values and simulation values.The thesis uses three design method,the theoretical calculation,the star-ccm+ software simulation,and experimental verification.Through three methods,mutual authentication,reasonable design and calculation,design a set of simple structure,high reliability of battery cooling system. |
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