中空纤维膜组件流动分布机理研究

One of the key challenges in the field of membrane is to achieve industrialization transition from membrane cell with high performance to membrane module with high performance through optimization of hydrodynamics conditions and mass transport process. In the present project, fluid flow in the hollow fiber membrane modules will be classified into three categories: fluid flow in the pore, membrane, and module scales, due to the multiscale channels in the hollow fiber membrane modules. High-tech measurement assisted CFD method will be adopted to investigate numerically the mechanism of multiscale fluid distribution in the hollow fiber membrane modules. With field emission scanning electron microscope and advanced image processing software, porous media model with pore-bone will be developed. The effect of the pore structure and its spatial distribution on the fluid distribution of the membrane scale will be studied through the porous media model. X-ray computed tomography will be utilized to build the CFD model of hollow fiber membrane modules. The effect of the membrane diameter, packing density distribution, and inlet manifold structure on the fluid distribution of the module scale will be revealed through the CFD model. The coupling between fluid flows of neighbor scales will be analyzed from novel viewpoint of how the driving force matches with resistance in the fluid flow. New insight will be put into the study on membrane transport process. The results will serve as the guidance of module structure optimization in both micro- and macro-scales, and will also provide the theoretical basis of the membrane process intensification and module scale-up.

膜领域的一大重要挑战在于：优化流体力学环境和质量传递过程，实现高性能膜单元向高性能膜组件过渡的工业化过程。本项目根据中空纤维膜组件通道的多尺度特点，将流动划分为膜孔、膜丝、膜组件三个层次，采用先进测试辅助建模下的计算流体力学（CFD）方法，模拟研究中空纤维膜组件多尺度流动分布机理。通过场发射扫描电镜结合先进图像处理软件，构建以膜孔道为骨架的多孔介质模型，探讨膜孔道几何形态和分布影响膜丝尺度流动分布的机制；通过X射线计算断层扫描，构建中空纤维膜组件CFD模型，考察膜丝直径、装填密度分布和进口分布器结构影响组件尺度流动分布的机理。从流动的推动力和阻力匹配的独特角度，分析膜组件内相邻尺度间流动的耦合过程。本项目为膜传递过程的研究提供了新思路；研究结果可用于指导膜组件微观和宏观几何结构的优化，为膜过程强化和组件放大奠定理论基础。

本项目着眼于膜领域的一大挑战—从高性能膜单元制备高性能膜组件，将中空纤维膜组件流动划分为膜孔、膜丝、膜组件三个层次，采用计算流体力学（CFD）方法，模拟研究组件的多尺度流动分布机理。本项目构建了膜孔尺度滤饼形成过程中的阻力串联离散化模型，并将其应用于膜丝、膜组件尺度，从而模拟得到了工业级膜组件流动分布随滤饼形成过程中的动态演变规律。考虑到工业应用膜组件的非理想结构特点，分别考察了进口分布器、膜丝非均匀装填，以及膜丝长度方向渗透性不均匀等因素，对膜组件流动分布、滤饼分布，以及产水性能的影响。基于这些研究成果，项目组到结题时已发表学术论文5篇（其中AIChE Journal论文1篇），培养了硕士研究生1名。本项目揭示了膜组件多尺度通道网络内的流动分布机理，有助于指导膜组件在水处理、气体分离，以及人工肾/肺领域的应用。