Numerical analysis of permeate flux in reverse osmosis by varying strand geometry

Abstract

In regions with limited potable water availability, membrane desalination is being employed to filter water using a pressure-driven approach. Because of the high energy consumption required to produce the pressure differential needed for this method, researchers have been trying different geometric designs of spacer filaments to enhance the amount of permeate flux in terms of energy utilization. The purpose of spacer filaments is to support membranes structurally and induce turbulent mixing in spiral wound membrane desalination. In this paper, the improvement of mass transfer in desalination driven by reverse osmosis has been studied using Computational Fluid Dynamics (CFD) with the introduction of spiral wound membranes that are lined with spacer filaments in a zig-zag formation having alternating diameters for strands. The fluid flow characteristics for a 2-dimensional geometric model were resolved using the open-source program OpenFOAM by changing the Reynolds number to just before the inception of instabilities. Ratios of alternate strand diameters were also varied between one and two. Based on a detailed analysis of velocity contours, pressure distribution, wall shear stresses, and steady-state vortex systems, the research findings offer guidance for employing alternating strand design in zig-zag formation for optimum mass transfer and minimal pressure drop when accounting for concentration polarization.

Techno-Economic Analysis of Vacuum Membrane Distillation for Seawater Desalination

“…According to a survey by Water Aid Organization, almost 663 million people on earth are lacking clean water [ 1 ]. Numerous desalination techniques are used to remove salts from sea water, such as Reverse Osmosis (RO) [ 2 ], multi-effect distillation (MED) [ 3 ], Multistage Flash Distillation (MFD) [ 4 ], and Membrane Distillation (MD). Another desalination technique is the use of a vacuum heat pump, explored by Bin et al [ 5 ].…”

Airfoil-shaped filament feed spacer for improved filtration performance in water treatment

“…The feed spacer in SWM supports mechanically the membrane leaves and promotes fluid unsteadiness associated with local shear rate, which improves the mass transfer and ultimately tackles bacterial growth 7 – 9 . However, there is a limiting value of the shear rate, above which bacterial attachment over the membrane is favored, which tarnishes the filtration efficiency and increases the pressure drop in the feed channel 5 .…”