中空纤维超滤膜组件通量分布的数值模拟

Numerical simulation of flux distribution in the hollow fiber ultrafiltration membrane module

为了研究中空纤维超滤膜组件通量分布,建立了基于膜丝实体为骨架的三维多孔介质模型,通过商用有限体积法软件求解管壳程以及膜丝多孔区纯水渗透过程的控制方程,得到管壳程的流场信息和多孔区的通量分布.研究表明,任意膜丝和膜丝束均存在通量分布的三维不均匀性,局部高通量增大了设备能耗,降低了组件效率;增大进出口压差降低了通量分布的均匀性,由于考虑了进口效应而更接近实际;膜丝渗透性的提高降低了通量分布的均匀性,在本文研究范围内,相同的进出口压差,膜丝渗透性提高5倍,产水量仅提高10%.本文计算流体力学模型适用于膜丝单元和膜组件研究,与实验偏差均在10%以内,可用于指导组件设计和优化.

In order to investigate the flux distribution in the hollow fiber membrane module,a three dimensional porous media model was built based on the skeleton of the porous support.The conservation equations of the shell and lumen space and the porous zone were solved by adopting the finite-volume based commercial code to describe the water ultrafiltration process.The flux distribution in the porous zone as well as the flow field in the shell and lumen space were obtained.Conclusions can be drawn from the simulation results：For arbitrary hollow fiber and fiber bundle,three dimensional non-uniformity of the flux distribution existed.The high local flux raised the energy consumption and decreased the efficiency of the module.An increase in the trans-membrane pressure caused a decrease in the uniformity of the flux distribution.Considering the effect of the inlet pattern made the simulation results more applicable.Decreasing the permeability of the membrane improved the uniformity of the flux distribution.In the scope of this article,with constant trans-membrane pressure,the water flow-rate increased only by 10% when the permeability increased by 500%.The CFD（computational fluid dynamics）model is suitable for research of single fiber and hollow fiber membrane module.The numerical results agreed well with the experimental data.Therefore,the model contributes to designing and optimizing the module structure.