Modelling of Feed Flow in Ultrafiltration Channels Using Computational Fluids Dynamics – Effect of Spacer Geometry Design

In this study a laminar crossflow filtration in a rectangular channel was simulated using the computational fluid dynamics (CFD) software ANSYSFLUENT. CFD was used to solve Reynolds-averaged Navier-Stokes equations and to assess the impact of change in the surface shear, boundaries, and shear strain, thus effectively studying their influence on the membrane fouling phenomenon. A three-dimensional numerical solution of the Navier–Stokes equations were developed using the Finite volume method. Varied ultrafiltration channel spacer sizes of 0.1, 0.2, 0.4 micrometers were simulated. SAMPLE of solution control was used as a pressure-velocity coupling and QUICK for momentum discretization. Scaled residual monitors were decreased up to 10^-5 for convergence satisfaction conditions. The larger spacers of 0.4 microns led to increased pressure drop across the membrane, as well as, increasing the hydrodynamics shear stress. However, the larger spacers of 0.4 microns led to the formation of localized stagnation or dead zones, where the membrane fouling phenomena may be increased. The influence of the feed spacer size on flow patterns inside the unltrafiltration unit will be discussed for each geometry at different feed flow rates in the range of 1 LPM to 7 LPM. The study demonstrated that the thickness of the ultrafiltration channel of 0.2 microns had the optimum results for the velocity and pressure profiles at different flow rates.