Abstract:

The laminar and turbulent flow fields in a rotating membrane filter was investigated based on the computational fluid dynamics method. The porous media model was applied to describe the effect of the membrane permeability on the flow behavior, and validation experiments were performed to determine the membrane resistance correction coefficient and to verify model reliability. On this basis, fluid velocity and pressure distributions in the filter were numerically analyzed, and effects of rotational speed of the membrane on the transmembrane pressure and shear stress over the membrane surface were explored. The results show that the variation of dimensionless angular velocity of the fluid along radial direction over membrane surface exhibits a tendency that it almost keeps constant in the middle region, decreases gradually near the rotation axis, and increases slightly near the edge of the membrane, and that the flow state has a significant influence on the dimensionless angular velocity in the non-viscous core of the interstitial fluid above and below the membrane. It is also found that the transmembrane pressure tends to decrease along the radial direction, while it decreases with the increasing rotational speed of the membrane under the same flow state. Moreover, the shear stress increases linearly along the radial direction at the same rotational speed of the membrane, and increasing the rotational speed of the membrane remarkably increases the shear stress.

Key words: filtration, membranes, porous medium, numerical simulation, transmembrane pressure, shear stress

摘要：

基于计算流体力学方法对旋转膜过滤器内部层流与湍流场进行研究，利用多孔介质模型描述滤膜的渗透性对流动的影响，开展验证实验，确定滤膜阻力修正系数，并验证模型的可靠性。在此基础上，对过滤器内部流体的速度和压力分布进行数值分析，并探究滤膜转速对滤膜表面跨膜压力和剪切应力的影响。结果表明，滤膜表面流体无量纲角速度沿径向呈现中间区域基本保持不变，旋转轴附近有所降低，滤膜边缘附近略有升高的趋势；流动状态对滤膜上、下方间隙流体无黏核心区的无量纲角速度有重要影响。研究还发现，跨膜压力沿径向趋于下降，同种流动状态下，跨膜压力随滤膜转速的增大而减小；同一滤膜转速下，剪切应力沿径向线性增大，提高滤膜转速，剪切应力显著增加。

关键词: 过滤, 膜, 多孔介质, 数值模拟, 跨膜压力, 剪切应力