Numerical simulation of brackish water desalination by a reverse osmosis membrane

The brackish water desalination by reverse osmosis membranes has been widely used to purify water. This study focuses on how the momentum mixing in the feed flow affects the membrane performance. Steady and transient two dimensional flows in a channel containing circular shaped spacers are investigated. Different arrangements and the spacing of cylinders are considered for the Reynolds number of 400, 800, and 4000. The feed channel is bounded by membranes. The velocity, the pressure, and the concentration fields are obtained by solving the Navier-Stokes and the mass transport equations. Laminar and turbulent flow models are employed in this study. The Shear Stress Transport (SST) k-ω turbulence model is utilized when the flow is turbulent. The membrane is treated as a permeable wall, and it is modeled as a functional surface. The water permeate is calculated based on the local osmotic pressure and the concentration at the membrane surface. Momentum mixing promoted by spacers enhances the membrane performance significantly.