Synergies between pulsatile flow and spacer filaments in reverse osmosis modules

Abstract

This work uses 2D fluid dynamics and mass transfer simulations to evaluate the use of pulsatile flow in spiral wound reverse osmosis modules. The aim of pulsatile flow is to enhance mass transfer and increase the performance of the membrane modules, without significantly affecting pressure drop and energy losses. The synergies that exist between pulsatile flow and spacer filament-induced oscillations are explored. The results indicate that there is an optimal frequency that amplifies the perturbations. Flow pulsations at the optimal frequency (which is related to the natural oscillating frequency of the channel) cause vortex shedding at Reynolds numbers below 350, compared to values above 500 that would be necessary without pulsatile flow. This leads to an increase in mass transfer and permeate flux of the order of 12 % at those conditions.