Influence of the spacer filament on the flow and mass transfer in reverse osmosis seawater desalination membrane

Abstract

The influence of the spacer filament on the flow and mass transfer in reverse osmosis seawater desalination membrane is studied by the lattice Boltzmann method. The effects of Reynolds number ( Re), blockage ratio ( β), and osmotic pressure (Δ P) on the concentration polarization, permeate flux, the drag and lift forces on the spacer, and the shear stress on the membrane surface are studied, respectively. The results show that the spacer near the membrane surface at large Re can effectively prevent the formation of the concentration boundary layer. The vortices near the membrane surface bring the solutes into the bulk flow, then reducing the concentration polarization and improving the mass transfer efficiency. In addition, the changes of the flow pattern, the mean value of the drag coefficient ( Cd), the lift coefficient ( Cl), and the skin friction coefficient ( fskin) are explored, respectively. The drag coefficient ( Cd) increases with the increase in β and decreases with Re, the permeate flux across the membrane and the increasing of the osmotic pressure will slightly reduce the drag and lift coefficients.