微米纤维表面修饰通孔金属泡沫热质输运机理研究

The distinctive properties, ultra-low density, enhanced flow mixing and high surface area-to-volume ratio of open-cell metallic foams, have led to their utilization in a variety of thermal engineering applications involving heat transfer enhancement. Without destroying the macro-structural topology of the foam, a novel approach is proposed to further enlarge its surface area-to-volume ratio by growing micro rods (ZnO) on the surface of metallic ligaments for enhancing the forced convective heat transfer. The micro rods synthesized on the cell walls of the open-cell foam squarely addresses their capability of improving the local convective heat transfer coefficient via locally enhancing flow mixing near the metallic ligaments at the pore level, favoring higher efficiency of utilizing the rich extension surface for heat transfer enhancement and increase the structure compactness. The present project aims to: (1) effectively characterize open-cell metallic foams with surface modified by micro rods via μ-CT-based 3D reconstructed topology and develop an idealized self-similarity periodic unit cell (UC) model; (2) establish analytical links between macro transport properties (effective thermal conductivity, permeability and inertial coefficient) and cellular topological characteristics (porosity, pore size and fractal dimension); (3) explore the effects of topological properties on the characteristics of thermal and fluid transport and reveal the mechanisms of the improvement for local convective heat transfer coefficient through direct numerical simulations coupled with the μ-CT reconstructed topological entity. The research achievements will enrich the existing theory system of local convective heat transfer and provide engineering guidelines for designing porous surface to enhance convection heat transfer.

通孔金属泡沫孔隙率高、相对密度小，具有丰富的比表面积和极强的流体扰动能力，是强化强制对流换热的优良载体。本项目建议以微米纤维修饰通孔金属泡沫网状骨架表面的方式，在不破坏泡沫宏观结构的基础上，进一步增大泡沫比表面积，同时增强孔内流体扰动，提高局部对流传热系数，更加高效的利用泡沫的丰富扩展表面，以强化对流传热的同时提高结构紧凑性。本项目提出基于工业Micro-CT三维拓扑重构的自相似周期性单元体模型，结合孔形貌参数和分形维数对表面修饰泡沫有效表征，建立泡沫宏观热质输运性质与微观结构参数之间的关系；结合局部非热平衡模型和拓扑重构实体直接数值模拟对流传热过程，研究孔隙尺度下泡沫骨架表面纤维对对流传热性能的影响，揭示纤维提高局部对流传热系数的机理；结合实验/数值模拟结果，建立纤维修饰表面的局部对流换热模型。本项目的实施将为多孔表面强化对流传热设计提供工程指导，丰富和发展现有局部对流换热理论体系。

通孔金属泡沫孔隙率高、相对密度小，具有丰富的比表面积和极强的流体扰动能力，是强化强制对流换热的优良载体。本项目建议以微米纤维修饰通孔金属泡沫网状骨架表面的方式，在不破坏泡沫宏观结构的基础上，进一步增大泡沫比表面积，同时增强孔内流体扰动，提高局部对流传热系数，更加高效的利用泡沫的丰富扩展表面，以强化对流传热的同时提高结构紧凑性。本项目的研究内容如下：①微米金属氧化物纤维修饰通孔金属泡沫拓扑结构参数表征研究；②不同微米纤维几何结构参数下，热质输运性质实验与理论建模研究；③微米纤维几何结构参数和换热工质对单相强制对流传热性能影响及传热强化机理研究；④通孔金属泡沫强化固液相变储能的实验及多尺度数值模拟研究。本项目所达成的目标如下：①通过本项目将建立表面修饰通孔金属泡沫热质输运性质与泡沫宏/细观拓扑参数之间的关系，确立有效导热系数、渗透率、惯性系数等基本输运物性参数的解析模型；②探明热质输运机理、阐明微米纤维修饰对孔内局部对流传热的影响；③建立泡沫孔内局部对流传热模型，揭示泡沫骨架表面附着微米纤维对单相强制对流传热的强化机理。本项目公开发表SCI检索论文11篇、EI检索论文17篇、授权发明专利6项、实用新型3项，申请人成功入选2018年“陕西省青年科技新星”及2017年西安交通大学第三届“十大学术新人”。本项目的研究成果将为新型强化单相强制对流传热表面的设计提供理论指导，补充和发展现有多孔介质对流传热的理论体系，有望满足特殊环境（如载人航天器环境控制系统、航天器热控系统、可重复运载航天器电子控制模块温控系统）对材料的多功能需求，减轻结构质量、提高结构的功能效率，具有重要的实际指导意义。