动力电池为电动汽车、飞行汽车和电动飞机等电动化交通的动力核心，是决定交通工具性能的关键。温度是影响动力电池性能的重要因素，不合适的温度范围及分布会导致其性能衰竭，缩短使用寿命。随着电池快充、大容量电池和高放电倍率飞行汽车及航空动力电池的发展，其热问题更加严峻，风冷和液冷电池热管理系统散热能力明显不足，难以满足电池对工作温度和温差控制的要求。热管具有双向高导热特性，在电池热管理领域日益受到重视。常见热管为一维传热元件，纵向传热性好而横向均温性受限。微通道热管阵列为准二维传热的新型平板式热管元件，可实现较好的均温性能，但其内部相变传热复杂，相关研究十分欠缺。论文针对微通道热管阵列热特性开展研究，通过建立基于其热阻网络模型的电池热管理系统仿真模型，发展基于微通道热管阵列的电池热管理系统热特性分析方法，研究热管理结构设计参数对动力电池热特性的影响规律，探讨微通道热管阵列技术下的电池热管理系统结构优化设计。论文工作包括以下几点。论文通过假设微通道热管阵列不同区域为不同流动传热现象引起的分布式热特性，建立了微通道热管阵列的分段式热阻网络模型，与动力电池热模型相耦合，发展了基于微通道热管阵列的电池热特性分析方法；通过实验对该方法验证，结果表明该方法可靠准确，为电池热管理系统热特性分析和结构设计奠定基础。论文通过数值仿真分析，研究了基于微通道热管阵列的电池热管理系统的结构设计参数对电池热特性的影响规律和机制。结果表明：电池模组热特性受微通道热管流体物性与槽道尺寸影响，高导热相变介质、深槽道可强化传热，增大换热接触面积的同时减小液膜厚度，降低传热热阻；电池模组热特性还受微通道热管阵列在系统中几何布置的影响，其置于电池单体之间时温升小；其与冷却流体顺流换热时温度均衡性好，此时热管壁面边界层内速度梯度小，对流换热系数均匀；冷却流体流量及其热物性影响散热，增大流体雷诺数可提高对流换热系数。论文通过优化基于微通道热管阵列的电池热管理系统几何尺寸与热物性参数设计，对应用于未来飞行汽车和航空动力的电池模组进行热管理设计。基于仿真分析发现，在小于5C放电倍率的恒流或动态工况下和40 ℃环境温度下，论文提出的热管理系统设计可将动力电池模组的温升和温差分别控制至50 ℃和5 ℃以下，验证了基于微通道热管阵列的车用动力电池热管理系统设计的有效性。
Power batteries are the core of power systems for electrified transportation, such as electric vehicles, flying cars, and electric airplanes, and they are the key components that determine the overall performance of those vehicles. Batteries are sensitive to the operating temperatures. Excessively high / low temperature or non-uniform temperature distribution would cause the performance deteriation and the battery aging. With the development of large-capacity batteries and high-discharge-rate power batteries for flying cars or aviation, the thermal problems will be increasingly severe. Traditional air cooling and liquid cooling methods are no longer sufficient to meet the thermal management requirements of batteries. Heat pipes have highly bi-directional thermal conductivity and are increasingly valued in this field. Comomon sintered heat pipes are one-dimensional heat transfer element, and they have good longitudinal heat transfer capability with limited horizontal temperature uniformity. A micro heat pipe array (MHPA) is a new two-dimensional flat type of heat pipes, which can achieve good temperature uniformity performance. However, related thermal investigation of the micro heat pipe array is lacking, due to the complex phase change process inside.Based on the thermal characteristics of the MHPA, a thermal resistance model was developed and integrated into a battery thermal management system (BTMS) model. A thermal analysis method for the MHPA-based BTMS was developed. The thermal performance of the BTMS was investigated at different structural design parameters, and the optimal design was proposed. The work includes the following parts.By assuming the distributed thermal characteristics caused by different flow heat transfer phenomena at different sections of the MHPA, the work established a segmented thermal resistance network model for the MHPA. The model was integrated with a BTMS model and related thermal analysis method was developed. The method was verified through experiments, and the results showed that the method was reliable and accurate, which lays the foundation for the following systematic thermal analysis and structural design of the BTMS.Through numerical simulation analysis, the work studied the influences and mechanisms of the structural design parameters on the thermal characteristics for the MHPA-based BTMS. The major results are: (1) conductive heat transfer capability can be enhanced by adopting deep grooves and high-thermal-conductivity fluid, which increase thermal contact areas and reduce thermal resistance of the liquid film; (2) convective heat transfer capability can be enhanced by increasing the Reynolds Number and Prandtl Number of the working fluid; (3) the battery module can achieve a better temperature uniformity when the evaporator of the MHPA is arranged at battery tabs or the condenser is aligned along the cooling flow direction in the BTMS, due to a smaller gradient in the thermal / velocity boundary layer. This work performed a thermal management design for battery modules applied in future flying cars and aviation through optimizing the design of the MHPA-based BTMS. The designed system can control the maximum temperature of the power battery module to be below 50 ℃ and a desired temperature difference below 5 ℃ at a constant or dynamic discharge rates of less than 5C or under an ambient temperature of 40 ℃. The results proved the effectiveness of the proposed MHPA-based BTMS design.
