Computational fluid dynamic simulation for hydrodynamic shear enhanced filtration in multiple shaft disk filtration system

Multiple shaft disk (MSD) filtration system, in which 12 ceramic membrane disks were inserted for creating multiple hydrodynamic shear enhanced filtration, is a promising dynamic filtration technology for water purification. In order to reveal the complex flow pattern and hydrodynamics in the internals as well as key influencing factors, the commercial CFD package FLUENT with the finite-volume method was applied to simulate the fluid flow and calculate the shear stress. Via CFD simulations, the quantitative and qualitative properties of fluid dynamics could be obtained, which was benefited to understand the multiple flow field and hydrodynamic shear performance. The higher rotating speed of ceramic membrane disk clearly improved the velocity magnitude, shear stress and turbulence, thus significantly enhancing the filtration performance. A modified mathematical model was proposed to compute the velocity entrainment factor k, which could be used to evaluate the influence of the ceramic membrane disk on fluid. The rightmost region of MSD possessed the most intense velocity magnitude, shear stress and static pressure, thus the corresponding ceramic membrane disks (disks 6 and 11) own the highest permeate flux and biggest self-cleaning ability for membrane fouling. As for the inlet flow rate, it had limited effect on the shear stress. Besides, the energy consumption and mechanical efficiency rose with the rotating speed. The pressure values in experiments were in good agreement with those of CFD simulations. The understanding of the hydrodynamic shear enhanced filtration in MSD based on CFD analysis can facilitate the design of dynamic filtration membrane system to improve the module performance and promote the water purification and fouling control.