摘 要

随着当今社会化石能源的进一步衰竭以及温室效应的加剧，传统燃油汽车的发展和应用逐渐向新能源汽车方向发展。电动汽车节能环保的特点，让它得到了政府部门、汽车领域和广大消费者的密切关注。用新能源汽车来逐步替代燃油汽车，是从能源因素和环保因素考虑的必然要求。和发动机对于燃油汽车一样，电池对于电动汽车来说像是“心脏”，是电动汽车的关键组成；电池的温度不仅在很大程度上影响电池的性能，还极大地影响电池的使用安全和寿命，因此，电池温度是电池耐用性、可用性以及可驱动性的重要影响因素之一，合理有效的电池冷却系统十分必要。随着现在电池的能量密度的提高，在一些放电速率较高的场景下，电池的热负荷较大，传统的光滑通道冷却板的传热能力不足以带走电池的热量。而泡沫金属由于很高的表面积与体积之比，并且泡沫金属的骨架导热系数较大，因而具有强大的传热能力。因此，泡沫金属填充式电池冷却系统更能满足较高热负荷场景下的散热要求。

在冷却过程中，多孔介质冷却板的孔隙率以及流体的流速会对电池系统的散热效果和压力损失产生影响，这两个参数是电池冷却系统的散热性能的重要因素。本文首先基于某电动汽车动力磷酸铁锂电池冷却系统，简化建立泡沫金属填充式电池冷却系统的流动传热模型，再使用CFD软件FLUENT进行流动传热过程的数值模拟，通过改变孔隙率以及冷却介质流速的大小，研究了具有不同孔隙率和冷却介质流速的泡沫金属填充式电池冷却系统散热效果和压力损失的影响规律。

在得到计算结果以后，首先分析有/无填充泡沫金属电池冷却系统的散热性能与压力损失，相同的冷却空气的流速下，泡沫金属填充式电池冷却系统的最高温度明显低于无泡沫金属填充电池冷却系统，这说明冷却介质流动区域在填充一定的泡沫金属后可以加强电池的散热性能。虽然同时冷却介质的压力损失会增大，但是泡沫铝仍是动力电池非常具有潜力的散热材料。接下来研究空冷/水冷泡沫金属填充式电池冷却系统的散热性能，相同冷却介质流速下，水冷泡沫金属填充式电池冷却系统散热性能明显强于空冷泡沫金属填充式电池冷却系统散热性能，在0.7泡沫铝孔隙率、1m/s的冷却介质流速下，水冷泡沫金属填充式电池冷却系统电池的温度较空冷泡沫金属填充式电池冷却系统电池的温度降低了18.14K。最后研究了泡沫金属孔隙率以及冷却空气流速对系统散热性能和压力损失影响，结果表明：冷却空气速度一定时，电池散热效果会随着泡沫铝孔隙率的减小而加强，但是压力损失会不断增大，且增大的趋势逐渐变大。冷却介质流速越大，电池冷却系统的散热性能越好，流过泡沫金属区域的压力损失越大。

关键词：多孔介质；铝泡沫；锂离子电池；热分析；压降

Abstract

With the further depletion of fossil energy in today's society and the intensification of the greenhouse effect, the development and application of traditional fuel vehicles are gradually developing towards new energy vehicles. The characteristics of energy-saving and environmental protection of electric vehicles have made it get close attention from government departments, the automotive field and consumers. The use of new energy vehicles to gradually replace fuel vehicles is an inevitable requirement in consideration of energy and environmental factors. Like engines for fuel-powered vehicles, batteries are like a "heart" for electric vehicles and a key component of electric vehicles; the temperature of the battery not only greatly affects the performance of the battery, but also greatly affects the safety and life of the battery. Therefore, battery temperature is one of the important factors affecting battery durability, availability, and driveability, and a reasonable and effective battery cooling system is necessary. With the increase in the energy density of batteries now, in some scenarios with higher discharge rates, the heat load of the battery is larger, and the heat transfer capacity of the traditional smooth channel cooling plate is not enough to take away the heat of the battery. Due to the high surface area-to-volume ratio and the thermal conductivity of the foam metal skeleton, the foam metal has a strong heat transfer capability. Therefore, the foam metal-filled battery cooling system can better meet the heat dissipation requirements under higher thermal load scenarios.

During the cooling process, the porosity of the porous medium cooling plate and the fluid flow rate will affect the heat dissipation effect and pressure loss of the system. These two parameters are important factors for the heat dissipation performance of the cooling system. In this paper, based on the cooling system of an electric vehicle power lithium iron phosphate battery, the flow heat transfer model of the foam metal-filled battery cooling system is simplified, and then the CFD software FLUENT is used to perform the numerical simulation of the flow heat transfer process. By changing the porosity and the cooling medium The flow rate of the aluminum foam with different porosity and cooling medium flow rate is studied.

This paper first studies the heat dissipation performance and pressure loss of the cooling system with/without foam metal foam battery. Under the same cooling air flow rate, the maximum temperature of the foam metal-filled battery cooling system is significantly lower than that of the non-foam metal-filled battery cooling system. It shows that the cooling medium flow area can enhance the heat dissipation performance of the battery after being filled with a certain foam metal. Although the pressure loss of the cooling medium will increase at the same time, aluminum foam is still a very potential heat dissipation material for power batteries. Next, the heat dissipation performance of the air-cooled/water-cooled foam metal-filled battery cooling system is studied. Under the same cooling medium flow rate, the heat dissipation performance of the water-cooled foam metal-filled battery cooling system is significantly stronger than that of the air-cooled foam metal-filled battery cooling system. At an aluminum porosity and a cooling medium flow rate of 1 m/s, the temperature of the water-cooled foam metal-filled battery cooling system battery is 18.14K lower than that of the air-cooled foam metal-filled battery cooling system battery. Finally, the effects of foam metal porosity and cooling air flow rate on the heat dissipation performance and pressure loss of the system are studied. The results show that: When the cooling air speed is constant, the heat dissipation effect of the battery will be strengthened as the porosity of the aluminum foam decreases, but the pressure loss will continue to increase, and the increasing trend will gradually become larger. The greater the flow rate of the cooling medium, the better the heat dissipation performance of the battery cooling system, and the greater the pressure loss through the foam metal area.

Key Words：Porous media; aluminum foam; lithium ion battery; thermal analysis; pressure drop.

目录

摘 要 3

第1章 绪 论 2

1.1电动汽车发展趋势及动力电池散热的重要性 2