低温流体在微细管道内大温差条件下湍流换热机理研究

Study of turbulent heat transfer of cryogenic fluids in mini-channels under large temperature difference is very important in the cooling down and quench protection of the superconductor systems, and heat exchanger in the air-breathing engine of hypersonic aircrafts. Three key problems will be solved within this project, turbulent heat transfer of cryogenic fluids at supercritical pressure in mini-channels under large temperature difference, heat transfer of cryogenic fluids at near critical pressure in mini-channels and the influence of micro structures inside the channel on the heat transfer. The turbulent heat transfer of cryogenic fluids at supercritical pressure in mini-channels under large temperature difference will be studied experimentally, theoretically and numerically, as well as the boiling heat transfer of cryogenic fluids near critical pressure, the change of heat transfer patterns due to pressure variation and the heat transfer enhancement of cryogenic fluids in mini-channels. The expected results will help lay the foundation for the improvement of cryogenic cooling system and the advancement of new generation of aircrafts.

低温流体在微细管道内大温差条件下的湍流换热问题研究在超导磁体冷却和失超保护、高超音速吸气/火箭混合式发动机研发等领域有着重大意义，近年来受到学术界的广泛关注。大温差条件下超临界压力低温流体在微细管道中的湍流换热机理、近临界压力低温流体在微细管道中的流动换热规律和微细管道内部结构影响低温流体换热的机理等是本项目拟解决的关键科学问题。本项目拟通过实验研究、理论分析和数值模拟，深入研究超临界压力低温流体在微细管道中大温差条件下的湍流换热机理；揭示低温流体在微细直管道中近临界压力沸腾换热机理和压力波动带来近临界压力沸腾换热/超临界单相流体换热形式改变的规律；阐明微细管道中低温流体流动换热的强化方法与规律。预期研究成果可以为低温冷却技术的进步和新型空天飞行器的发展提供理论支持。

本项目研究内容顺利开展，深入研究了大温差条件下超临界压力低温流体在微细直管道中湍流换热机理、近临界压力流动换热规律和低温流体喷射/喷雾冷却机理。搭建了超临界压力氮高压低温流动换热实验系统；获得了大温差条件下超临界压力氮在微细直管道中流动换热的机理、浮升力和热加速对垂直管内换热的影响规律，以及准临界温度附近的传热恶化现象；揭示了低温流体喷射/喷雾冷却过程中工质温度和壁面温度的变化规律，冷却开始时间对温度变化的影响，冷量利用率和制冷剂需求量之间的关系。研究成果有助于深入认识液化天然气制备储存过程中的低温传热问题，优化天然气开采工艺；提出的液氮喷射/喷雾冷却技术，在快速大幅降温的前提下，避免低温工质和被冷却壁面直接接触而造成低温损坏，在高热流密度电子器件冷却领域有广阔的应用前景。研究成果已在国际国内会议发表，撰写2篇期刊论文。