| The battery pack of an electric car is enclosed in space,and the battery cells are arranged in a dense manner.The heat generated by the battery can easily accumulate inside and cause fire accidents.Therefore,the cooling design of the battery must be carried out to ensure that the battery temperature is controlled within a reasonable range.In this paper,a certain 18650 ternary lithium ion battery is taken as the research object.Based on the analysis of the thermal generating mechanism of a single battery,the influence of coolant flow,cold plate wall thickness,coolant temperature and discharge rate on battery cooling behavior are analyzed by numerical simulation method,which provide reference for the design of liquid cooled battery pack.Meanwhile,in order to improve the simulation efficiency,AMESimsoftware is used to build a one-dimensional model of battery liquid cooling and heat dissipation for simulation analysis,which provides a new idea for the simulation research of battery heat management.In order to study the thermogenic characteristics of the battery,the battery test bench was built by using equipment such as incubators,battery charging and discharging instruments,and HPPC method was used to measure the internal resistance of the single battery at different temperatures and under different SOC states.The entropy heat coefficient of the battery was measured by direct measurement.The temperature rise of a single battery at different discharge rates was measured.The results show that the internal resistance of the battery decreases with the increase of temperature,and the internal resistance at the end of discharge increases rapidly with the decrease of SOC.In the process of discharge,the reversible reaction of the battery is not always shown as heat release,but first heat release,then heat absorption,and then heat release.When the battery is discharged at low power ratio,the heat generation is mainly the reversible reaction heat,while the heat generation is mainly the irreversible internal resistance heat when the battery is discharged at high power ratio.The liquid cooled system of battery pack was designed.A cold plate is used to cool the battery,the contact point between the cold plate and the battery is bent by 50.75 ° to maximize the thermal conductivity area.The influence of different mass flow rate of coolant,different thickness of cold plate,different temperature of coolant and different discharge rate on the cooling effect of battery pack was analyzed.Through comparative study,it is found that the mass flow of cooling fluid of 20g/s can control the maximum temperature of the battery pack at 36.6? and the maximum temperature difference at 4.5?,the maximum temperature and the maximum temperature difference of the battery can be reduced by increasing the mass flow rate of the coolant,but the effect of further increasing the mass flow rate on the maximum temperature and the maximum temperature difference is very small when the mass flow rate is greater than 30g/s;by comprehensive comparison of battery temperature change and flow channel pressure loss,the thickness of cold plate wall is 0.5mm;reducing the temperature of the coolant can effectively reduce the maximum temperature of the battery pack,but will increase the maximum temperature difference between the batteries,in order to ensure that the maximum temperature difference between the coolant and the battery is less than 5?,the initial temperature difference between the coolant and the battery should be less than 5?;under different discharge rate,the liquid cooling system can control the battery temperature in a reasonable range.The AMESim software was used to simulate the temperature rise of a single battery under different discharge rates,and the results were compared with the experimental results to verify the accuracy of the one-dimensional particle model.On this basis,a one-dimensional battery cooling and heat dissipation model is built,and the temperature change of the battery is simulated under different discharge rates.And the battery temperature rise at the inlet and outlet of coolant is compared with that of 3d simulation,and the accuracy of simulation is verified. |
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