| A pure electric car produced by a certain enterprise uses air cooling to dissipate the power battery.Now,in order to improve the energy density of the battery system,and plans to develop a new battery pack scheme,this pure electric car re-chooses 2170 cylindrical lithium-ion battery as the power battery.In order to improve the performance and safety of the battery module,Through experiments and simulations,a new liquid cooling structure scheme for batteries is designed.The main research contents of this paper are as follows:(1)Based on the analysis of the basic structure and working principle of the 2170 cylindrical lithium-ion battery,the heat generation mechanism,thermal physical parameters and heat transfer mechanism of the single battery were studied.A three-dimensional simulation model of the single battery was established,and the heat generation rate model of the single battery was used to predict the temperature changes of the single battery under different working conditions.(2)In order to obtain the parameters of the heat generation rate model,the HPPC method was used to carry out the battery internal resistance test.During the test,the temperature of the thermostat was adjusted to the set value,and the single battery was charged to the cutoff current at constant current and constant voltage.Then,the battery was pulse charged and discharged at every 10%SOC at different discharge rates,and the voltage and current data were collected.The variation of internal resistance at different discharge rates and temperatures was obtained.In order to compare with the calculation results of the subsequent simulation model,a temperature rise test was carried out.Two thermocouples were placed on the side of the battery and the battery was placed in an incubator.The battery was charged to the cutoff voltage at different rates,and the surface temperature of the battery was collected in real time.(3)The Fluent software was used for the simulation analysis of single battery,and the heat source required for the simulation of single battery was established based on the internal resistance test data combined with the heat generation rate model,and then the heat source was introduced into the three-dimensional simulation model of single battery.The simulation results of battery heat generation under different discharge rates showed that the error rate of simulation and test data was within 5%.The accuracy of single battery simulation model is verified.(4)The liquid cooling cooling system of lithium ion battery was designed.The simulation and analysis of the heat dissipation effect of the modules(three rows of cells in dislocation arrangement)under the natural cooling mode with different cell spacing(2mm,4mm,6mm,8mm)were carried out.The results show that the heat dissipation effect of 6mm cell spacing is the best.The snake,square and honeycomb liquid cooling structures were designed on the basis of optimal spacing,and then the battery packs of these three cooling structures were simulated,and the temperature field changes of the battery modules and the carrier coolant were analyzed.Considering the temperature rise of the modules,the pressure of the carrier coolant,the cooling effect and the manufacturing process,the honeycomb liquid cooling battery packs cooling structure was determined to be the optimal structure.The structural parameters are as follows: the liquid cooled plate is provided with six microchannels,each of which is 10.5mm high and 4mm wide;The total thickness of the liquid cooled plate is 6mm,and the wall thickness of the liquid cooled plate is 2mm(Figure4-18).(5)The heat dissipation structure of honeycomb liquid cooled battery pack was studied and analyzed from the perspective of different cooling factors,considering the influence of different inlet flow rates of carrier coolant(0.02m/s,0.04m/s,0.06m/s,0.08m/s),different inlet temperatures(15℃,20℃,25℃)and changing inlet and outlet positions on the heat dissipation of battery modules.The simulation results show that: under the same discharge rate,the flow rate of the carrier coolant inlet is 0.08m/s,and the carrier coolant inlet temperature is 15℃,the cooling effect of the battery module is better,which can provide reference for the load regulation and control of the BMS thermal management system.The upper three runner channels on the left side of the model are all inlet channels,and the lower three runner channels are outlet channels,which have a good cooling and heat dissipation effect on the battery module.Through the above research,the heat dissipation structure and main parameters of the power battery module are determined,which provides a reference for the subsequent development of battery liquid cooling system. |
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