热管阵列内相变换热与两相流动机理及其优化设计的研究

A heat pipe is a high performance heat transfer device which is used to transfer a large amount of heat with a small temperature difference. With an arrangement, heat pipes can be connected to work as heat pipe array, which has incomparable advantages in heat transfer performances and applications，but has also special heat transfer problems. In this project, for the heat pipe array with header pipe, the mechanism of boiling heat transfer in the evaporation section, the mechanism of two phase flow and the optimization between different heat exchange units were studied systematically. The experimental technology such as Micro-PIV particle image technology, high speed micro-photography, high precision infrared thermal imager and electrical capacitance tomography were comprehensively used to dynamically measure the three dimensional distributions of working fluid, flow field, temperature field and the characteristic of the bubble dynamics. Through theoretical analysis, numerical simulation and visualization, boiling heat transfer characteristics and the law of liquid film evaporation in the evaporation section of heat pipe array were illuminated. Also the mechanism of two phase flow in the adiabatic section of the heat pipe array were illuminated. Through the establishment of heat transfer model for the heat pipe array, combined with influence of various parameters on the heat transfer performance of heat pipe array, the work mechanism of heat pipe array was revealed. Finally the criteria of optimization design and matching to get the best heat transfer performance of the heat pipe array and optimal thermal resistance was obtained, which provided a theoretical basis for the optimization design of heat pipe array and heat exchanger.

热管是一种高效传热元件，小温差下就能传输大量的热量。多根热管串并联形成的热管阵列，具有普通热管难以比拟的传热性能和应用优势，同时具有独特的传热机制。本项目针对带母管的热管阵列，对蒸发段沸腾传热机理、绝热段汽液两相流动机理以及不同换热单元之间的耦合匹配与优化进行系统深入的研究。综合利用Micro-PIV粒子图像测速技术、超高速显微摄像仪、高精度红外热像仪以及电容层析成像技术，实现对热管阵列内工质的三维空间分布、流场、温度场及汽泡动力学行为的动态测量。通过理论分析、数值模拟及可视化实验研究，阐明热管阵列蒸发段内的沸腾及液膜蒸发换热规律；阐明热管阵列绝热段内汽液两相流动规律；通过建立热管阵列的整体传热模型，结合各参数对热管阵列换热性能的影响规律，揭示热管阵列各部件协同工作的机制，以优化热阻为目标，得到最佳换热性能下的热管阵列各部件之间的优化匹配准则，为热管阵列及其换热器的优化设计提供理论依据。

热管阵列比单根热管具有更强的换热能力和均温特性，内部的相变换热与两相流动机理更为复杂。本项目建立了热管阵列换热性能综合测试平台，详细研究了输入功率、热源位置、充液率、管径、倾斜角度、工质、冷却水流量和温度等因素对热管阵列热阻及效率的影响，获得了热管阵列沿程及内部工质的压力场与温度场变化规律。结合可视化研究，揭示了热管阵列启动特性、循环流动规律、流型转变规律以及汽泡动力学行为。在此基础上，借助数值模拟研究，阐述了热管阵列内部流动沸腾换热机理，获得了连续的相分布及汽液两相分界面上的流动特性，从而对热管阵列中的流动换热与工作机理有了充分认识。项目的研究成果对于设计和优化热管阵列具有理论指导作用。同时，本项目开展了基于热管阵列技术的空气除湿及空气余热回收、新能源汽车动力电池热管理领域的应用研究，成功的示范运行案例充分显示热管阵列换热器具有很好的应用前景，对于降低行业的能耗，实现国家节能减排的战略目标具有重要的意义。