A two-dimensional mechanistic model for scaling in spiral wound membrane systems

The effect of feed spacer geometry on membrane performance and concentration polarisation based on 3D CFD simulations

“…This can be attributed to differences in boundary conditions and spacer geometries. The assumption of a constant solute rejection by the membrane, as was done in the aforementioned study [14,21] and in others [6,12,15,18,26,30,31], may need to be revisited since membrane rejection is not an intrinsic property of membranes but an output of an RO process. It would be desirable if this could be predicted as part of a CFD simulation.…”

“…The fully woven configuration, consisting of curved strands being woven together, has a highly complex geometry. In the partially woven configuration, one set of filaments remains straight, with each strand being in contact with the top and bottom plane alternatingly, while the other set is woven through the gaps between the first set of filaments [30]. The middle layer configuration is built based on the 'Parallel spacer' [2,40] and 'Middle layer spacer' [31] in the literature.…”

“…As such, spacers of different types and geometries have been compared in terms of local shear stress and mass transfer coefficient [1-2, 5, 7, 9, 38-40]. A commonly used approach to account for solute permeation is to specify a constant membrane rejection combined with water flux and wall concentration [6,12,15,18,21,26,30,31]. This can be expressed as: J s = J w c m (1−R s ) where J s is the solute flux, J w the water flux (or flow velocity on the membrane wall), c m the solute concentration on the membrane wall and R s the membrane rejection.…”

A review of efforts to reduce membrane fouling by control of feed spacer characteristics

“…The feed spacer geometry determines the power necessary to overcome the fouling-derived resistance to fluid-flow. The dissipation of the yield flow pattern is associated with the shear stress distribution on the feed spacer filaments and membranes [5], which has effects on the permeate flux [65,66], scaling [67], biofouling and operation [68]. Thus, these phenomena should all be considered in any proposed new designs intended to optimise feed spacer geometry to reduce fouling [69].…”

“…The majority of the modelling in two-dimensions have been performed using a ladder spacer strand pattern, where the feed spacer strands are aligned transversally and axially to the bulk flow direction. The impacts of strand size and alignment on scaling and (bio)fouling in reverse osmosis for desalination have been subject of study [67]. Even though cylindrical strands have most commonly been taken into inconsideration, other cross-sectional forms, for instance triangular, saw-tooth [73], square [74], and elliptical [75] have also been assessed.…”