液氮温区回路热管微通道凝结过程气液界面作用机制及其影响的研究

Cryogenic loop heat pipes (CLHPs) are advanced heat transfer technology with high efficiency which is developing rapidly in recent years. The subject is a research hotspot of cryogenics. With the development of aerospace and electronics, the weight, cooling performance and electromagnetic or vibration interference of the cryogenic cooling devices are more strictly limited. As a result, CLHPs with miniaturization, light weight, high flexibility and efficiency are becoming pressing desired. However, the decreased structure will result in more complicated problems on two phase flow and heat transfer mechanism in the channel of the condenser, which is a difficult problem in miniaturization of CLHPs. This project is aimed at studying the fundamental mechanisms on the gas-liquid mechanism of action during condensation process in microchannels at liquid-nitrogen temperature range, with the unique structure of CLHPs. Many complicated scientific problems like two phase flow and phase change heat transfer in microchannel will be investigated theoretically and experimentally. The influence of the problems on the operating mechanism of miniature CLHPs will be researched and relevant two phase flow model and heat transfer model will be established. This work will provide theoretical basis for developing miniature CLHP prototypes and broaden the cryogenics to more widely application areas.

低温回路热管技术是近年来发展起来的一种高效低温冷量传输技术，是低温技术领域的研究热点。随着航空航天、电子器件等领域的迅速发展，对低温冷却技术在重量、性能、电磁或振动干扰等方面提出了更严格的限制，要求低温回路热管向微型化、轻量化、高柔性和高效率的方向发展。而结构尺寸的缩小也会使冷凝通道内两相流动及换热机理变得更为复杂，这是低温回路热管向小型化迈进的重要科学难题。本项目将借助小型低温回路热管的独特结构，针对液氮温区微通道冷凝过程的气液界面作用机制开展基础研究，通过理论分析和实验研究，探索低温微通道气液两相流型变化规律和换热特性，及其对热管传热特性的影响，并建立相应的流动模型和传热模型，为研制小型化低温回路热管样机提供理论依据，拓宽低温技术的应用领域。

低温回路热管技术是一种应用于低温领域的高效传热技术，能够实现被冷却器件与低温冷源之间的柔性连接，有效隔离振动和电磁干扰等，在航空航天、超导电子等领域具有广阔的应用前景。本项目针对液氮温区小型低温回路热管微通道内冷凝过程的气液界面作用机制开展研究和分析，探索气液两相流动与换热对低温回路热管超临界启动特性和运行特性的影响。本项目开展小型低温回路热管的方案设计工作，不仅使其满足低温环境下启动和传热工作要求，还满足在低温下实现冷凝微通道局部可视化的要求，根据方案设计研制了具有局部可视化功能的冷凝器以及小型低温回路热管原理样机，并且对该样机进行了高低温冷热冲击试验和耐压能力测试等。针对该低温回路热管的结构特点和实验要求，开展了低温试验系统方案设计，在该方案设计的基础上进行了低温回路热管试验系统搭建工作，使低温试验系统满足低温回路热管试验要求。对低温冷凝微通道内工质流动开展初步的可视化实验研究，观测到在微小尺度通道内气体形成长气泡然后逐渐缩小为圆形气泡直至消失的变化过程，初步验证了前期的分析结果。结合能量守恒定律，对低温回路热管的超临界降温启动过程中热流量分配进行了深入分析，探索低温工质在不同流动路径中流量分配对降温过程的影响，得出降温过程经历时间的估算方法。结合低温回路热管实验研究结果，与理论分析结果进行对比分析，通过对整个过程进行分阶段研究，探索导热漏热、次热负荷等因素的影响，验证了理论分析正确性。