孔隙尺度非饱和多孔介质基于VOF方法的冷凝传热特性研究

The moisture in the pore space in the unsaturated porous media exists in the forms of liquid and vapor. The fluid flows continuously in the small pore space surrounded by the solid skeleton. The mass transfer, momentum transfer and energy transfer of the moisture are very complicated transport phenomena. The aim of this project is to study the microscopic condensation phenomenon of moisture in the unsaturated porous media. The pore-scale fundamental study will be performed to investigate the coupled flow characteristics and condensation heat transfer in porous media on pore scale, in which the free interface exists between the liquid and vapor phase. The theoretical analysis and numerical simulation will be carried out to study the liquid flow pattern, the development and evolution of liquid-vapor interface and the interaction between liquid and vapor phase in the pore space in porous media. Multi-scale numerical model based on the VOF method is to be studied to predict the multiphase flow with phase change in the complex geometries. The technique to solve the numerical model is also taken into account. The pore-scale experimental work on the condensation heat transfer in porous media will be carried out to validate the numerical model. The pore-scale prediction model will be developed to calculate the condensation heat transfer. The effects of liquid-vapor phase change and surface physical characteristics of the porous media solid skeleton, the structure characteristics of pore-scale flow channel and the scale effect are considered in the model. The objective of this project is to investigate the characteristics of condensation heat transfer in unsaturated porous media on pore scale. The research work of this project contributes to the micro-scale study on the moisture and heat transport problem in the unsaturated porous media. The results of this project will have a scientific and technological significance for contributing to the contents of the prediction of the condensation heat and mass transfer in the unsaturated porous media.

湿分以液体和蒸汽形式存在于非饱和多孔介质的孔隙空间中，在微小的骨架孔隙空间中流体连续流动，其质量、动量和能量的传递是极为复杂的传输现象。本项目以非饱和多孔介质中的湿分微观凝结传热特性为研究对象，在孔隙尺度下对多孔介质内包含自由交界面的气-液耦合流场特征及冷凝传热规律进行基础科学研究。具体内容包括：理论分析与计算多孔介质骨架孔隙中液相流态、气-液交界面发展与演化规律以及气-液相间作用规律；基于VOF方法研究复杂几何结构体中多尺度涉及相变的多相流动传热数值建模及求解；通过孔隙尺度冷凝传热试验，建立基于气液相变效应、多孔介质表面物理特性、孔隙流道结构特征和尺度效应等多因素复杂耦合的孔隙尺度冷凝传热预测模型。本项目旨在揭示孔隙尺度下非饱和多孔介质中冷凝传热规律，为从微观结构尺度上去研究多孔介质内热湿传输现象和准确预测非饱和多孔介质冷凝传热传质过程奠定理论和技术基础。

非饱和多孔介质孔隙空间中以液体和蒸汽形式存在着湿分，在复杂结构孔隙空间中湿分连续流动，其质量、动量和能量的传递是极为复杂的输运过程。本项目以非饱和多孔介质中的湿分微观凝结传热特性为研究对象，在孔隙尺度下对多孔介质内包含自由交界面的气-液耦合流场特征及冷凝传热规律进行了基础科学研究。制备与表征了不同类型多孔介质实验样品，研究堆叠扫描图片处理以及实体三维数值重建技术，从而实现了多孔介质固体骨架边界的微观结构数值重建。基于VOF方法进行两相流动数值建模，模拟研究了复杂多孔介质中两相流动问题，揭示了多孔介质骨架孔隙中液相流态、气-液交界面发展与演化规律以及气-液相间作用规律，并对孔隙尺度下单相/多相对流传热特性进行了深入研究分析。基于VOF方法研究了涉及相变的多相流动传热数值建模及求解，在此基础上揭示了膜状冷凝以及多气泡冷凝特传热特性规律。并开展了气液两相流动可视化以及借助红外热像仪的冷凝传热可视化实验研究，孔隙尺度冷凝传热试验为建立基于气液相变效应、多孔介质表面物理特性、孔隙流道结构特征和尺度效应等多因素复杂耦合的孔隙尺度冷凝传热预测模型提供了科学参考。本项目旨在揭示孔隙尺度下非饱和多孔介质中冷凝传热规律，为从微观结构尺度研究多孔介质内热湿传输现象和准确预测非饱和多孔介质冷凝传热传质过程奠定理论和技术基础。