Mass transfer enhancement in spacer-filled membrane channels by flow oscillation induced vortex shedding: Numerical study of the effect of amplitude

Techniques inducing unsteady flow have shown potential for promoting vortex shedding in membrane channels, affecting the boundary layer and increasing mass transfer. This work reports a CFD study of the effect of the characteristics of an oscillating flow (i.e., frequency and amplitude) on the occurrence of vortex shedding. The implications of imposing an oscillating flow are analysed by comparing mass transfer enhancement and required pumping power. Results show that the resonant frequency for the perpendicular velocity component does not maximise mass transfer, but it yields a significant increase. For Re = 300, a normalised amplitude of 0.01 appears as a balanced trade-off between mass transfer and pressure drop. The location of onset of vortex shedding in the channel moves upstream as the amplitude increases. Mass transfer reaches an upper limit as the amplitude increases, when the onset of vortex shedding reaches the first filament. The phenomena taking place in a 2D spacer-filled membrane channel, and their implications for real-world applications, are discussed. (c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

Automated summary

This study investigates the effect of the characteristics of an oscillating flow (i.e., frequency and amplitude) on the occurrence of vortex shedding in membrane channels using CFD simulations. The results show that the resonant frequency for the perpendicular velocity component does not maximize mass transfer, but it significantly increases it. A normalized amplitude of 0.01 appears as a balanced trade-off between mass transfer and pressure drop. The location of onset of vortex shedding moves upstream as the amplitude increases, and mass transfer reaches an upper limit when the onset reaches the first filament.