基于孔隙尺度的开孔泡沫金属内固液相变传热特性研究

The solid-liquid phase change heat transfer in open-cell metal foams is the typical multi-scale transport phenomena coupled with multi-phases and multi-physics. The properties of metallic foams are greatly interrelated with the pore-scale effect. Macroscopic average methods, however, are deficient to study these transport phenomena. In this project, the solid-liquid phase change heat transfer in open-cell metallic foams is investigated using the pore-scale simulations, thus providing more fundamental understandings of these transport problems. Due to the limitations of macroscopic models and existing experimental methods at the present time, the lattice Boltzmann method (LBM), which is based on gas kinetic theory and supplemented with necessary measurements and visualized experiments on the surface of metal foams, will be used in this work to perform quantitative investigations of solid-liquid phase change heat transfer and fluid flow within open-cell metal foams with three-dimensional pore structure. The major contents in this project include the investigations of solid-liquid phase change processes in metal foams with open cell, the influences of pore structure and structure defect on solid-liquid phase change heat transfer, the calculations of some important transport parameters. This project is helpful for the optimization of the heat transfer by changing the inner structure of metal foams, provides theoretical basis for the design of high efficiency porous phase change heat exchange, and also lays the foundation for developing the theory of enhancing heat transfer of porous media with high porosity.

开孔泡沫金属内固液相变传热是典型的非稳态、多相、多物理场耦合的多尺度传输问题。泡沫金属的宏观性能往往具有显著的孔隙尺度效应，但是现有基于表征体元尺度的宏观平均方法却不能精确地描述和揭示这种效应，具有局限性。本项目将从泡沫金属的微观孔隙结构出发,在孔隙尺度上揭示开孔泡沫金属内固液相变传热特性及其规律，对泡沫金属材料的三维孔隙结构进行描述和表征，以介观格子Boltzmann方法为理论研究方法，并辅以必要的实验测量和泡沫金属结构表面上传输现象的可视化观测，重点探讨泡沫金属的微观孔隙结构及其缺陷对固液相变传热的影响机制，获取开孔泡沫金属中相关重要传输参数与孔隙结构参数之间的定量关系，以弥补传统宏观模型和实验观测在微观定量研究上的不足。本项目将为优化泡沫金属孔隙结构调控其传热性能奠定基础，为高性能多孔相变换热器的研发提供理论依据，丰富高孔隙率多孔介质强化传热理论。

开孔泡沫金属内固液相变传热过程的研究在相变贮能、可再生能源利用、电子器件热控制等领域有着重要的理论意义和应用价值。多孔泡沫金属的宏观性能往往具有显著的孔隙尺度效应，但是现有基于表征体元尺度的宏观平均方法却不能精确地描述和揭示这种效应，具有局限性。因此本项目主要从孔隙尺度上开展开孔泡沫金属内固液相变传热过程的理论和实验研究工作。在实验研究方面，采用光学显微及红外热成像技术开展了泡沫金属内固液相变传热的可视化实验，观测了泡沫金属微观孔隙结构下固液相变传热与流动特征，考察了开孔泡沫金属对相变材料相变过冷度的影响，揭示了微观孔隙结构下相变材料固液相变特性。在数值模拟研究方面，构建了多孔介质内固液相变传热及流体流动过程的二维及三维孔隙尺度格子Boltzmann方程模型并进行数值模拟研究，重点探讨了泡沫金属的孔隙结构参数及典型结构缺陷对固液相变传热的影响。此外，应用源强化概念及场协同理论对相变材料固液相变过程的自然对流效应进行了理论分析。