受冷湿空气在低表面能泡沫金属纤维骨架内相变组分凝析与疏导机制

Metal foams have extremely large specific areas, and they may enhance the instantaneous dehumidifying coefficient during the cooling dehumidification process. The key to practical application of metal foam is to ensure the sustainability of high effective dehumidification, and the condensate droplet of phase change component must be timely drained out of the metal foam. In the present project, the idea to improve the drainage ability of droplet from metal fiber by using low surface energy coating on metal fiber surface is proposed, and the condensation and drainage mechanisms of phase change component of the cooled moist air in metal foam fiber skeleton with low surface energy are studied. Through the investigation of the droplet wetting effect and the dynamic droplet behavior characteristics on the metallic fiber and cell with low energy surface energy, the microcosmic condensation and drainage mechanisms of the phase change component are clarified. The prediction models for the droplet formation, growth and fall characteristics on the metallic fiber and cell are developed based on nucleation theory, mixture diffusion theory and Level-set method. The mathematic method for describing the spatial topological structure of metallic fiber, cell, metal foam fiber skeleton and the droplet is developed based on graph theory, connecting the local heat and friction resistance characteristics of droplets to the heat and mass transfer characteristics in the whole metal foam; the development for the heat and mass transfer model reflecting the condensation and drainage mechanisms of the phase change component can be finally established. The research results will provide the theoretical basis for applying the metal foam to achieve the efficient dehumidification, and will enrich the theory of heat and mass transfer during the condensation process in porous medium.

泡沫金属具有超大比表面积，可大幅提高冷却除湿过程的瞬时析湿效率；其实际应用的关键是要保证高效除湿的持续性，为此必须使相变组分凝结析出的液滴得到及时疏导。本项目基于纤维表面低表面能改性增加液滴脱离纤维能力的思路，开展受冷湿空气在低表面能泡沫金属纤维骨架内相变组分凝析与疏导机制的研究。通过对低表面能金属纤维与胞元上凝结液滴浸润模式及动态行为特征的研究，掌握相变组分凝析与疏导的微观机制；基于液滴成核和混合物扩散理论以及水平集方法，建立纤维及胞元上液滴形成、生长及脱落等行为特征的预测模型；开发基于图论的纤维、胞元和泡沫金属纤维骨架拓扑结构以及液滴位置的描述方法，构建联系液滴局部热阻和摩阻特性与整体泡沫金属内热质传递特性的桥梁，完成反映低表面能改性泡沫金属内相变组分凝析疏导机制的热质传递特性模型的建立。项目成果为应用泡沫金属实现持续高效除湿提供理论依据，并丰富多孔介质内的凝结相变热质传递理论。

泡沫金属具有超大比表面积，可大幅提高冷却除湿过程的瞬时析湿速率；应用泡沫金属高效除湿的关键是保证相变组分凝结析出的液滴得到及时疏导。本项目基于低表面能改性增加纤维表面液滴脱离能力的思路，开展受冷湿空气在低表面能泡沫金属纤维骨架内相变组分凝析与疏导机制的研究。对泡沫金属骨架内湿空气析湿过程的换热和压降特性进行了实验测试，得到了具备析湿工况下最优综合性能的泡沫金属结构为孔密度20PPI，孔隙率95%；低表面能泡沫金属内湿空气的换热系数比未改性泡沫金属增大了5%-34%，同时压降也增大了1%-95%；通过同时考虑换热和压降特性的综合性能评价，发现析湿工况下低表面能改性泡沫金属的综合性能在相对湿度小于50%时优于未改性泡沫金属，而高表面能改性泡沫金属的综合性能优于低表面能改性和未改性泡沫金属；通过对纤维及胞元上液滴的生长和脱落等行为的观测实验，开发了液滴在泡沫金属纤维表面脱落和在泡沫金属胞元内排出的预测模型；基于液滴成核和混合物扩散理论，开发了泡沫金属骨架内湿空气析湿过程的数值模型，构建了联系局部液滴特性和整体泡沫金属热值传递特性的桥梁，建立了反映低表面能改性泡沫金属内相变组分凝析疏导机制的热质传递特性模型。本项目超额完成了研究计划，取得了一系列创新成果。共发表标注基金编号的论文28篇，其中英文SCI论文12篇、EI论文5篇。本研究为应用泡沫金属实现持续高效除湿提供理论依据，并丰富多孔介质内的凝结相变热质传递理论。