界面热质耦合作用下对流与相变传热机制研究

Because of the absorption or release of latent heat, liquid-vapor phase change process is a very efficient heat transfer mechanism, and has a very important practical significance for the space technology. However in microgravity environment, the buoyant force is greatly weakened. Phase change and thermocapillary convection become the dominant factor of liquid-vapor phase change process. So the mechanisms of convection and phase change heat transfer, and the origin and effect of thermocapillary convection at the liquid-vapor interface in microgravity environments are of important basis to understanding the characters of microgravity liquid-vapor phase change phenomenon. In present studying, we will use the phase change process of curve liquid-vapor interface in the closed different diameter quartz tubes to thoroughly research the evaporation and convection phenomena and the visual technology will be used to observe the characters of evaporation and condensation process in the liquid-vapor two-phase system. Combining the ground normal gravity experiments, microgravity drop tower experiments and numerical simulation research methods, we hope to establish the proper theoretical model of interface thermodynamics in the liquid-vapor phase change process, and reveal the origin and effect of thermocapillary convection in the microgravity liquid-vapor phase change process.

液气相变过程中伴随着潜热的释放或吸收，具有极大的传热能力和效率，对于航天技术应用具有非常重要的现实意义。在空间微重力环境下，浮力被大大削弱，相变、热毛细对流等界面现象成为液气相变过程的主导因素，因此，要揭示微重力条件下液气相变过程的机理，就必须了解微重力液气相变过程中液气界面附近对流与相变传热机制，以及相变界面体系中热毛细对流的产生机理和作用机制。本项目利用不同直径的封闭石英玻璃管中液气弯曲界面上的相变过程，对液气界面上的蒸发对流现象进行深入研究，采用可视化技术观测伴随有蒸发和冷凝过程的液气两相体系中的对流特征与传热特性，综合利用地面常重力和地基短时微重力落塔实验研究以及数值模拟等方法，以期构建能够正确描述液气相变过程中界面热动力学行为的理论模型，揭示微重力液气相变过程中热毛细对流的产生机理及其作用机制。

本项目数值模拟和实验研究热、质耦合作用下液气界面附近的局部对流与相变传热现象。通过调研液气相变过程的数理模型，比较了不同模型对液气相变特征预测能力及其优劣，筛选了动理学比拟模型用于目前液气相变过程的计算。构建了包括加热固壁内部的瞬态热传导及其周期性的蓄-放热效应、液气相变过程等因素在内的多相数值模型，开展了含固壁热效应和相变过程的液-气-固三相接触区流动与传热现象的数值模拟，发现在蒸发-凝结作用驱动下的流动中，沿相界面温度梯度很小，热毛细效应几乎可以完全忽略不计。在实验方面，研制了伴有相变界面的液-气-固体系观测实验装置，进行了常重力和短时微重力条件下非均匀温度体系流动与传热现象的实验观测，增进了对界面热质输运特性的认识。本项目研究结果有助于深化对微重力沸腾传热机理的认识。