基于相变散热的动力电池热管理系统研究

发布时间：2018-06-07 18:27

本文选题：锂离子电池 + 热管理系统　；参考：《中国科学技术大学》2017年硕士论文

【摘要】：近年来在环境污染和能源危机的双重压力下,世界各国都在大力发展新能源汽车以取代传统燃油汽车,而新能源汽车发展的关键在于动力电池技术。目前,锂离子电池因其性能卓越成为了动力电池的主流选择。但是,锂离子电池仍存在一定的安全隐患,火灾爆炸事故时有发生,严重制约了新能源汽车的推广和应用。所以,锂离子电池的热安全问题已经成为了一个研究热点。其中,锂离子电池的温度是影响其电化学性能以及安全性的关键因素,因此为了将锂离子电池的温度控制在最佳的工作温度范围内,亟需对动力电池热管理系统进行研究。本文通过实验和模拟相结合的方法对基于相变散热的动力电池热管理系统进行了研究,并提出了优化设计的方法。本文首先对基于复合相变材料(Phase Change Material,PCM)的电池热管理系统进行了研究,利用石蜡和膨胀石墨制备得到复合相变材料,进一步研究了在电池组动态循环过程中PCM热管理系统的性能以及影响因素。实验结果表明:一个充放电循环过程中单电池及自然对流散热系统下电池组的温度变化曲线中均出现了两个温度峰,而PCM热管理系统中仅仅只出现了一个温度峰。随着电池充放电循环倍率的增大,PCM热管理系统和自然对流散热系统中电池组的最大温升和最大温差也明显增大。此外,PCM热管理系统的散热能力要优于自然对流散热系统,尤其是在高倍率充放电循环过程中更为明显,另外适当延长充放电循环步骤之间的搁置时间有利于提高PCM热管理系统的散热能力。推荐在实际电池PCM热管理系统中使用相变温度为45℃的PCM。其次,本文提出了一种用于电池系统散热及防止热失控传播的复合板,具有"三明治"的结构,主要是由导热壳、相变材料及隔热板三部分组成的。根据电池的产热理论以及相变传热理论等建立了复合板热管理系统中锂离子电池的三维热模型,详细对比分析了四种不同结构下电池组的散热能力以及热失控阻隔能力。模拟结果表明,结构1(电池之间紧密贴合)和结构2(电池之间有空气间隙)的散热性能相近,说明在封闭环境中单纯增加电池间的间隙并不能有效地提高电池组的散热能力。结构3(电池之间有散热板)中电池组具有较好的散热能力,但是该系统的热失控阻隔能力较差。结构4(电池之间有复合板)能够有效提高电池组的散热能力以及电池组温度分布的均一性,同时能够提高电池组的隔热能力。增加复合板中PCM的相变潜热能够有效提高复合板的性能,推荐在复合板热管理系统中使用相变潜热为1125kJ/kg以及相变温度在303.15K到323.15K 之间的 PCM。最后,基于前面的设计思路搭建了基于复合板的电池热管理系统,通过实验和模拟初步验证了设计的可靠性。通过实验对比分析了在正常工作条件和热滥用条件下不同热管理系统的性能。同时建立了电池的电化学-热耦合模型,通过该模型研究了电池的产热特性以及复合板的性能。研究结果表明,电池间有复合板和石墨膜的热管理系统的散热性能最好,放电倍率较高时更为明显;电池表面贴有石墨膜的热管理系统次之,无任何热管理系统的散热性能最差。电化学-热耦合模型能够准确预测电池在放电过程中的电压变化,最大偏差不超过3%,同时能够较好地预测放电末期电池的最高温度。复合板能够有效提高电池组的散热能力以及隔热能力,20A放电条件下复合板结构中电池的最大温升下降了 2℃,热滥用条件下复合板系统中电池的温度稳定在36℃左右,对应的模拟结果与实验结果吻合较好。综上,本文通过实验与模拟相结合的方法,对电池动态循环中的产热规律、PCM热管理系统中电池的传热过程和关键因素的影响规律以及复合板的性能等方面进行了研究,研究方法和结果可以为实际动力电池热管理系统的设计提供理论指导和参考。
[Abstract]:In recent years, under the double pressure of environmental pollution and energy crisis, all countries in the world are vigorously developing new energy vehicles to replace traditional fuel vehicles, and the key to the development of new energy vehicles lies in the power battery technology. At present, lithium ion batteries have become the mainstream choice of power pools because of their excellent performance. However, lithium ion batteries still exist. A certain risk of safety, fire and explosion occurred, seriously restricting the promotion and application of new energy vehicles. Therefore, the thermal safety of lithium ion batteries has become a hot research focus. It is urgent to study the thermal management system of the power battery in the optimum temperature range. In this paper, the heat management system of the power battery based on the phase change heat dissipation is studied by the combination of experiments and simulation, and the optimization design method is put forward. First, the Phase Change Mater based on the composite phase change material (PCM) is used. The battery thermal management system of ial, PCM was studied. The composite phase change materials were prepared by paraffin and expanded graphite. The performance and influence factors of the PCM heat management system during the dynamic cycle of the battery pack were further studied. The experimental results showed that the single cell and the natural convection heat dissipation system in the process of charging and discharging cycle were used. There are two temperature peaks in the temperature change curve of the group, but only one temperature peak is found in the PCM heat management system. With the increase of charge discharge cycle ratio, the maximum temperature rise and maximum temperature difference of the PCM heat management system and the natural convection heat dissipation system are also obviously increased. In addition, the heat dissipation capacity of the PCM heat management system is also increased. It is better to be superior to the natural convection heat dissipation system, especially in the process of high rate charging and discharging cycle, and the proper extension of the shelving time between the charging and discharging cycle steps is beneficial to improve the heat dissipation capacity of the PCM heat management system. It is recommended to use the PCM. of the phase transition temperature of 45 C in the actual battery PCM heat management system. A composite plate used for the heat dissipation of the battery system and preventing the transmission of heat out of control. It has a sandwich structure, mainly composed of three parts: heat conduction shell, phase change material and heat insulation board. Based on the theory of heat production and the theory of phase change heat transfer, the three-dimensional thermal model of lithium ion battery in the composite plate heat management system is established in detail. The heat dissipation capacity and thermal control capacity of the four different structures are analyzed. The simulation results show that the heat dissipation performance of structure 1 (close bonding between batteries) and structure 2 (the air gap between batteries) is similar, indicating that only increasing the gap between batteries in a closed environment can not effectively improve the heat dissipation capacity of the battery pack. The battery pack has good heat dissipation capacity, but the heat loss barrier ability of the system is poor. The structure 4 (the composite plate between the batteries) can effectively improve the heat dissipation capacity of the battery and the homogenization of the temperature distribution of the battery group, and can improve the insulation ability of the battery group. The PCM in the composite panel can be increased. The latent heat of phase change can effectively improve the performance of the composite plate. It is recommended to use the 1125kJ/kg in the heat management system of the composite plate and the PCM. of the phase transition temperature between 303.15K and 323.15K. Based on the previous design idea, a battery thermal management system based on the composite plate is built. The design is preliminarily verified through experiments and simulation. The performance of different heat management systems under normal working conditions and heat abuse conditions was compared and analyzed. The electrochemical thermal coupling model of the battery was established. The heat production characteristics of the battery and the performance of the composite plate were studied by this model. The results showed that the heat management system of the composite plate and graphite membrane was found in the electric pool. The heat dissipation performance is the best, the discharge ratio is higher, the heat management system with graphite membrane on the surface of the battery is the second, and the heat dissipation performance of the system is the worst. The electrochemical thermal coupling model can predict the voltage change of the battery in the discharge process accurately, the maximum deviation is not more than 3%. At the same time, it can predict the end of the discharge better. At the highest temperature of the battery, the composite plate can effectively improve the heat dissipation and heat insulation ability of the battery. The maximum temperature rise of the battery in the composite plate structure under 20A discharge is 2 degrees C. The temperature of the battery in the composite plate system is stable at about 36 C under the condition of heat abuse. The corresponding simulation results are in good agreement with the experimental results. Through the combination of experiments and simulation, the heat production law in the dynamic cycle of the battery, the heat transfer process and the key factors in the PCM heat management system and the performance of the composite board are studied. The research methods and results can provide theoretical guidance for the design of the actual power pool heat management system. Reference resources.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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