中空纤维膜外压全量过滤动态过程的数值模拟

摘要

A CFD model was developed based on the filtration in the dead-end outside-in hollow fiber membrane module. Various fiber length, diameter, permeability, packing density, fouling index and transmembrane pressure were chosen during numerical simulation of the dynamic evolution of flux distribution and permeate volumetric flow rate. The simulation revealed that the uniformity of flux distribution improved as the filtration processes. The self-adjustment of the flux distribution was more pronounced with longer, narrower, more permeable fibers, higher packing density, fouling index and trans-membrane pressure. The inverse of the water volumetric flow rate increased linearly with the accumulated volume of the permeate. Due to the non-uniformity of the flux distribution and its dynamic evolution, the linear relationship differed from the one presented in the classic cake filtration model. A correlation equation to characterize the dead-end outside-in cake filtration in the hollow fiber membrane module was obtained through curve fitting of the simulation data. The equation enabled the prediction of the module performance and better design of the module.%建立了中空纤维膜外压式全量过滤的 CFD 模型，模拟膜丝长度、直径、渗透系数、装填密度、污染指数以及跨膜压差不同条件，得到通量分布和产水量的动态演变过程。研究结果表明：通量分布会随着过滤的进行而逐渐变得均匀，这种通量分布的自我调节作用在膜丝较长、较细，渗透性较好，装填密度较高，污染指数较高以及跨膜压差较高时更为明显；产水流量的倒数与累积产水量呈线性关系，但由于通量分布不均匀并且均匀性演变，这种线性关系区别于传统滤饼过滤模型；通过数据拟合得到了适用于中空纤维外压式全量操作的滤饼过滤关联式，可用于预测组件的性能和指导组件的设计。