A computational fluid dynamics approach to predict the scale-up dimension of a water filter column

Abstract

A bench-scale filter consisting of sand media was tested for hydrodynamic parameters (velocity and pressure) using ANSYS-CFX (computational fluid dynamics or CFD software) to further determine the ‘subjective minimum scale-up’ (SMS) filter dimension. The purpose of this study is to relate the hydrodynamics property of the bench scale column and the scale-up column for a porous fluid flow using CFD to understand the scale-up limitations. The poor flow regime in bench-scale filter was observed because of a high variance in the pressure gradient as obtained for a plane perpendicular to the direction of fluid flow (orthogonal plane). The flow regime pattern was analyzed by structural modelling and in-built programming using the concept of CFD. Using CFD, a SMS filter dimension was obtained that was found free of high-pressure gradient (on orthogonal plane near the column exit) that might have incurred due to a ‘bad’ flow regime in case of the bench-scale filter. This could sort operational issues caused due to pressure-velocity parameters and would help researchers to step-up with scale-up dimension (from bench-scale) more confidently and credibly. The simulation was obtained for the scale-up reactor using the intrinsic properties to validate the model. An error of 4.1% was reported between the experimental velocity of the bench-scale filter vs simulated value from ANSYS-CFX. Also, a better plug flow condition was obtained for the scale-up column using CFD (Morill dispersion index or MDI = 3) as compared to that of bench-scale filter (MDI = 2.2).