CFD Investigation of Near-Membrane Slippery Condition Effects on Water/Salt Transport in a Reverse Osmosis Feed Channel

Abstract

In many membrane-based water treatment methods, because of consistent salt fouling on the membranes of the narrow feed channel, studying methods of improving the fluid flow and mass transfer of the membrane element is vitally important. Providing a slippery situation for the fluid adjacent to the membrane can result in concentrated fluid movement and system operation improvement. In this research, the effects of various magnitude of slip velocities on the important parameters of membrane feed channel operation at the wide range of Reynolds numbers have been investigated. To this end, CFD has been implemented and the continuity, Navier–Stokes, and mass transfer equations in a 2D narrow channel have been solved. Two cases with and without slip velocity have been compared comprehensively in the wide range of Reynolds numbers from 100 to 2100. Also, the influence of fluid properties variations with the salt concentration on output results has been studied. Due to the induced slip velocity, the results demonstrate a decline of about 5–12% in concentration polarization, an increase of 20–60% in Sherwood number, a decrease of 5–13% in friction factor, and an increase of 0.5–1.5% in permeation flux.