模块化构建的中空纤维膜组件流动特性与热质传递机理研究

The hollow fiber membrane contactor is a key component in membrane-based liquid desiccant air dehumidification technology. Before its industrial application, one of the crucial project need to conduct is to develop the design theory for large contactors with high efficiency and low flow resistance. In this project, a modular membrane contactor is proposed, in which the number of modules scales with the volume of the contactor. In a module, hollow fibers are randomly potted and thus it is easy to achieve automated manufacturing and the production cost can be substantially reduced. Owing to the artificially and uniformly arranged modules, it facilitates the optimization of flow, heat and mass transfer performance of the contactor. The experiment, theoretical analysis and numerical method are used to study the heat and mass transfer mechanism in the contactor, which is consisted of bundles with randomly distributed fibers and regularly arranged modules. Firstly, the momentum, heat and mass transfer models of the module and the contactor are established, respectively. Secondly, the effects of membrane features and module layout on the flow, heat and mass transfer performance of the contactor are studied. The effects of bending, crossing and etc. of fibers on the flow, heat and mass transfer in a module are also disclosed. Afterwards, by analyzing synergy principles between velocity and temperature/velocity and humidity in contactors with various geometrical parameters, the optimization criteria for contactors with high efficiency and low flow resistance are raised. At last, scale-up principles of the contactor are clarified.

膜组件是膜式液体除湿技术的核心部件，完善高效低阻的大型组件设计理论是该技术走向工业应用前的一项关键课题。本项目提出一种新型模块化构建的中空纤维膜组件。其中模块的数量由大组件的容量决定，而每个模块内装填了随机分布的中空纤维膜管束。模块易于机械化装填，从而大幅度降低了制造成本。模块可实现人工规则排列，以利于流动和热质传递性能的优化。本项目拟采用实验、理论分析和数值模拟的方法，针对模块化组件内“随机分布管束-规则分布模块-整体组件”的多层次结构中的流动与传热传质过程展开基础研究。分别建立模块和整体组件内动量、能量和质量传递模型，研究膜的传热传质特性对组件性能的影响，研究模块排列方式对组件内流动不均匀性及传热传质性能的影响，研究纤维管弯曲度、交叉度等特性对管束流动与传热传质的影响。分析不同模块布局方式下组件内流场/温度场/湿度场的协同规律，提出高效低阻膜组件设计准则，阐明组件的性能放大规律。

本项目针对现有中空纤维膜组件在气液膜分离中应用时所表现出的缺陷，提出了一种基于模块化设计的新型中空纤维膜组件。该组件具有可维护性好，组件处理容量易调节的特点。本项目主要研究内容：（1）采用了实验、理论分析和数值模拟的方法，针对这种新型模块化构建的膜组件内“随机分布管束-规则分布模块-整体组件”的多层次结构中的流动与传热传质过程展开了研究。分别建立模块和整体组件内动量、能量和质量传递模型，研究了模块排列方式对组件内流动不均匀性及传热传质性能的影响，研究了纤维管随机排布等特性对模块流动与传热传质的影响；（2）总结了高效低阻膜组件设计准则，研究了组件的性能放大规律。. 本项目取得了以下重要结果：（1） “随机分布纤维管束-规则分布子模块-整体组件”多层次结构中流动与传热传质行为受空气测雷诺数、组件开度等多种因素影响，其中最大的影响来自于模块开度。模型揭示组件的性能放大并非是线性的，组件的性能会随着子通道中模块数量的增加而减小，减小的幅度由模块的开度大小决定；（2）综合利用机器视觉、拓扑学分析技术和CFD技术，对子模块内随机分布的管束拓扑特征和传热传质性能进行了研究，发现子模块的横截面局部孔隙拓扑特征是决定其传热传质性能的关键因素。研究建立了局部孔隙拓扑特征参数与子模块流动与传热传质性能的定量关系，具体呈幂函数关系；（3）研究进一步发现子模块的性能与其横截面孔隙拓扑特征之间的幂函数关系不受组件外壳形状的影响，研究所提出的方法和公式具有一定普适性。