Research On The Cooling Technology Of Pump-driven Two-phase Flow Lithium Battery

As people’s awareness of environmental protection increases,the environmental hazards of fuel-fueled vehicles are gradually being valued by people,so people have introduced electric vehicles to improve the current situation.The water-cooling system is widely used in lithium battery cooling due to its simple and effective characteristics,but the water-cooling system uses sensible heat to exchange heat,which has poor heat exchange capacity.At the same time,the water-cooling system has a battery short circuit caused by the leakage of the working fluid,which can cause combustion and explosion.And other safety hazards.Therefore,this paper proposes a two-phase pump drive system to replace the water-cooling system with a lithium battery cooling scheme,and combines simulation and experiment methods to explore the impact of various parameters in the system on performance.The same experimental bench and experimental conditions are used to compare the heat dissipation effects of the pump drive two-phase flow system and the water-cooling system,and then analyze and summarize the advantages and characteristics of the pump drive two-phase flow technology.In this paper,R1233zd,which is non-toxic,non-flammable and insulating,is selected as the circulating working fluid.Compared with the traditional refrigerant R134a,R1233zd has higher latent heat and lower GWP,and is more environmentally friendly.In order to reduce the risk of the experiment,this article uses a single lithium battery charge and discharge experiment to obtain the equivalent heat generation power of the lithium battery,so that the heat source of the corresponding power is used in the simulation and experiment to replace the lithium battery.In the lithium battery charging and discharging experiment,this article draws the conclusion:The heat generation power of the square lithium battery with a size of 130mm x 35mm x 234mm under 1C,2C and 2.5C magnification conditions is 9.39k W/m~3,30.06k W/m~3 and 43.20k W/m~3.In this paper,by means of simulation,25 ternary lithium batteries are used as a battery pack,and a module-level simulation is performed to simulate the use of pump-driven two-phase flow as a heat dissipation system under 1C,2C,and 2.5C rate conditions.The results show that when the ambient temperature is 25°C,the cold source temperature is 10°C,and the charge and discharge rates of 1C,2C,and 2.5C,the average temperature of the battery pack is 23.88℃,39.27℃,49.17℃,respectively.The temperature difference of the battery pack is 0.86℃,1.47℃,and 1.79℃respectively.This paper explores the impact of load power,flow rate,cold source temperature and liquid storage tank temperature on system performance in a pump-driven two-phase flow system through experimental research.The results show that:1)The system has strong stability during operation,and the load power is The change has little effect on the state of the working fluid;2)The flow rate can control the outlet dryness,and a better cooling effect can be achieved when the outlet dryness is 0.3;3)The liquid storage tank can effectively control the subcooling of the working fluid;4)The temperature of the cold source can significantly affect the heat dissipation effect.The lower the temperature of the cold source,the greater the power required by the liquid storage tank and the preheater.This article compares the experimental results of a pump-driven two-phase flow system and a water-cooled system under the same load power,the same ambient temperature and the same cold source temperature,and concludes:1)The pump-driven two-phase system only needs less heat to achieve the same heat dissipation.2)The temperature difference between the cold plate and the cold plate of the pump drive two-phase system is lower.When the load power is 0.5k W to 1.1k W,the average temperature of the lower surface of the cold plate is 2℃to 3℃lower than that of the water cooling system.The average surface temperature of the cold plate is2°C to 6°C lower than that of the water-cooled system,and the temperature uniformity of the cold plate is 7 times that of the water-cooled system;3)The pump-driven two-phase system can better inhibit the spread of local hot spots.In this experiment,the local hot spots of the water-cooling system spread to 1/3 of the entire cold plate area,while the local hot spots of the pump-driven two-phase system only occupy 1/10 of the cold plate area.In summary,the pump-driven two-phase flow system has stronger heat dissipation capacity,higher temperature uniformity,and better safety,so the pump-driven two-phase flow system has very broad application prospects.