An improved numerical scheme to study mass transfer over a separation membrane

The numerical prediction of mass transfer rates in the mass boundary layer over a membrane separation requires the use of a very dense grid. In this w ork, a simple logarithmic variable transformation applied to the solute tra nsport equation improves the well-known finite difference scheme, allowing the use of a larger grid spacing without loss of accuracy. This method is a pplied to solve laminar flow and solute transport equations in a parallel p late device with permeable walls. The concentration profiles along the memb rane surface and in the mass boundary layer are predicted. For high permeat e velocity, the grid spacing can increase four times without loss of accura cy. The method applied has several advantages comparatively to the optimize d grid spacing method that can be used in alternative. (C) 2001 Elsevier Sc ience B.V. All rights reserved.