Fluid Dynamics and Mass Transfer in Spacer-Filled Membrane Channels: Effect of Uniform Channel-Gap Reduction Due to Fouling

Koutsou, C.P.; Karabelas, A.J.; Kostoglou, Margaritis

doi:10.3390/fluids3010012

Cited by 15 publications

(18 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22. It is obvious from the graph that the pressure drop is directly proportional to Reynolds number as was proven in previous studies [7,[17][18][19].…”

Section: Pressure Dropsupporting

confidence: 67%

A 3D CFD comparative study between torsioned and non-torsioned net-type feed spacer in reverse osmosis

Abdelbaky

El–Refaee

2019

SN Appl. Sci.

View full text Add to dashboard Cite

Spacer-filled channels are incorporated in membrane modules in reverse osmosis applications where the role of feed spacer is to promote turbulence, improve mass transport and mitigate concentration polarization. The objective of this study is to emulate a realistic spacer, due to manufacturing conditions, spacers tend to have a special complex geometry (deformations) which is usually not adopted in computational fluid dynamics (CFD) studies, this deformation tends to be of a torsioned shape. A total of 18 simulations were conducted for torsioned and non-torsioned spacers evaluating concentration polarization and mass transfer across membrane walls at different inlet salinities (c o = 400, 500 and 600 mol/m 3) and different Reynolds number (Re = 100, 192 and 384) based on the inlet velocity using fully-coupled three dimensional CFD, where the solution-diffusion model was incorporated for the calculations of water and solute fluxes across reverse osmosis membrane. The current comparison illustrates that the torsioned spacers have an overall enhanced performance compared to non-torsioned spacers. It is found that concentration polarization is mitigated in torsioned spacers which is the contrary with non-torsioned spacers having a tendency to concentration polarization, consequently, the water flux in torsioned spacers was found higher than those in non-torsioned spacers. Generally speaking, all membrane modules are found to have a higher performance at higher Reynolds number and at lower inlet salinity. This study proves that spacer geometric details are critical to predict accurately the RO membrane performance. Keywords Reverse osmosis (RO) • Computational fluid dynamics (CFD) • Feed channel • Concentration polarization • Mass transfer List of symbols A Water permeability [m/(Pa s)] B Solute permeability [mol/(m 2 s)] c Concentration (mol/m 3) d h Hydraulic diameter (m) D s Diffusion coefficient (m 2 /s) J w Water flux (m 3 /m 2 s) J s Solute flux (mol/m 2 s) k Osmotic factor (m 3 Pa/mol) n Normal vector (dimensionless) p Pressure (Pa) R Gas constant [J/(mol K)] T Temperature (K) u Velocity vector (m/s) x Cartesian coordinate y Cartesian coordinate z Cartesian coordinate Greek letters Density (kg/m 3) Dynamic viscosity (Pa s) Osmotic pressure (Pa) Subscripts ave Average b Bulk f Feed low Lower membrane surface o Inlet condition

show abstract

“…22. It is obvious from the graph that the pressure drop is directly proportional to Reynolds number as was proven in previous studies [7,[17][18][19].…”

Section: Pressure Dropsupporting

confidence: 67%

A 3D CFD comparative study between torsioned and non-torsioned net-type feed spacer in reverse osmosis

Abdelbaky

El–Refaee

2019

SN Appl. Sci.

View full text Add to dashboard Cite

show abstract

“…For flow in narrow empty channels, laminar flows are assumed for Reynolds number, Re, less than 2000 [37]. It is reported in the literature that there is departure from the laminar flow regime at very low Reynolds numbers for spacer filled channels [38][39]. This modified Reynolds number, Rem, is defined on the basis of superficial velocity and spacer filament diameter.…”

Section: Fluid and Solute Flow In The Feed And Permeate Channelsmentioning

confidence: 99%

“…This modified Reynolds number, Rem, is defined on the basis of superficial velocity and spacer filament diameter. Laminar regime persists for Rem < 200 [38][39]. Manufacturers prescribe that the average velocity and pressure drop for spacer filled channels do not exceed 0.34 ms -1 and 0.6bar/m; this corresponds to Reynolds number, defined on a similar basis, of less than 200 [38].…”

Section: Fluid and Solute Flow In The Feed And Permeate Channelsmentioning

confidence: 99%

“…Various authors have and continue to publish on the effects of feed spacers on solute and solvent flows through the membrane [31]. Broadly speaking, spacer models typically exclude permeation as this has little effect on wall shear stress [32], though examples are found in the literature [39][40]. Calculation of local permeate flows can increase computational load.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

TWO-DIMENSIONAL Mathematical Model of Flows In Thin film composite Membranes

Maharajh¹,

Persad²,

Cheddie³

et al. 2020

Proceedings of the International Conference on Emerging Trends in Engineering &Amp; Technology (IConETech-2020)

View full text Add to dashboard Cite

Mathematical modelling of reverse osmosis membranes has evolved from simplified one-dimensional simulations to complex three-dimensional simulations using CFD based techniques. These models have been useful in simulating solute and solvent flows across the membrane, the development of the concentration polarisation layer and the effects of spacer and spacer geometry as some examples. Various simplifying assumptions are, however, made in the modelling process that limit their extension to the specific application of directly-coupled wave powered desalination. These include the treatment of the membrane and use of rejection coefficients for solute transport. The model presented in this paper addresses some of the limitations imposed currently on available models. Fully coupled mass-momentum equations are specified for the hydrodynamics within the feed, membrane and permeate channels. Semi-empirical relationships are developed to account for the effects of inlet pressure, cross-flow velocity and inlet concentration on solvent and solute flows across the membrane. The model is validated against published experimental data and the predicted errors for simulations of solvent and solute flows were found to be 0.6% and 0.7% respectively. The effects of three feed spacer types, submerged, cavity and zigzag, on solvent and solute flows are then considered. Larger wall shear stress was seen for the submerged type spacer than for either cavity or zigzag types.

show abstract

“…The third paper with direct industrial relevance is a detailed analysis of the behavior of the spiral-wound membrane-a separation method used in reverse osmosis and desalination processes for water treatment. Koutsou et al [6] used three-dimensional (3D) direct numerical simulations to show how flow and mass transfer are affected by the membrane fouling process. Correlations between the friction factor and the mass transfer coefficient obtained through this study have practical use and can also be employed to develop realistic dynamic models for the operation of spiral-wound membranes in water treatment plants.…”

mentioning

confidence: 99%