A numerical study of the effect of channel spacers on the performance of cross-flow forward osmosis membrane modules

Jalali, Alireza; Niknafs, Naeem

doi:10.22059/ees.2020.44657

A numerical study of the effect of channel spacers on the performance of cross-flow forward osmosis membrane modules

Document Type : Research Paper

Authors

School of Mechanical Engineering, College of Engineering, University of Tehran, North Kargar Avenue, Tehran,1439957131, Iran

10.22059/ees.2020.44657

Abstract

In this paper, we perform two-dimensional simulations of cross-flow forward osmosis (FO) membrane modules in the presence of draw and feed channel spacers. For this purpose, the equations corresponding to the conservation of mass, momentum, and convection-diffusion for the mass fraction of solute are solved using a commercial finite volume flow solver. We consider six configurations of channel spacers being constructed by the symmetric and asymmetric placement of cavity, submerged, and zigzag arrangements. We will study the effect of the spacers’ geometrical parameters such as diameter and relative distance in these configurations as well as the solute resistivity of the porous support layer on the performance of the FO membrane modules in terms of water flux, external concentration polarization (ECP) factors, and pressure drop per unit length of the membrane. Our results reveal that increasing the solute resistivity of the porous support layer has an adverse effect on the water flux, whereas the impact on the ECP factors is positive. In addition, it turns out that the submerged configurations, where the spacer filaments are not in direct contact with the membrane surface, produce the highest water flux through the membrane; however, they have an adverse effect on the pressure drop along the membrane surface.

Keywords

References

[1] W. Chan, E. Marand, S.M. Martin, Novel zwitterion functionalized carbon nanotube nanocomposite membranes for improved RO performance and surface anti-biofouling resistance, J. Memb. Sci. 509 (2016) 125–137.

[2] J. Farahbakhsh, M. Delnavaz, V. Vatanpour, Investigation of raw and oxidized multiwalled carbon nanotubes in fabrication of reverse osmosis polyamide membranes for improvement in desalination and antifouling properties, Desalination. 410 (2017) 1–9.

[3] R. Ghidossi, D. Veyret, P. Moulin, Computational fluid dynamics applied to membranes: State of the art and opportunities, Chem. Eng. Process. Process Intensif. 45 (2006) 437–454.

[4] A.L. Ahmad, K.K. Lau, M.Z.A. Bakar, Impact of different spacer filament geometries on concentration polarization control in narrow membrane channel, J. Memb. Sci. 262 (2005) 138–152.

[5] A. Hilgenstock, R. Ernst, Analysis of installation effects by means of computational fluid dynamics—CFD vs experiments?, Flow Meas. Instrum. 7 (1996) 161–171.

[6] M. Park, J.J. Lee, S. Lee, J.H. Kim, Determination of a constant membrane structure parameter in forward osmosis processes, J. Memb. Sci. 375 (2011) 241–248.

[7] A. Sagiv, R. Semiat, Finite element analysis of forward osmosis process using NaCl solutions, J. Memb. Sci. 379 (2011) 86–96.

[8] M.F. Gruber, C.J. Johnson, C.Y. Tang, M.H. Jensen, L. Yde, C. Hélix-Nielsen, Computational fluid dynamics simulations of flow and concentration polarization in forward osmosis membrane systems, J. Memb. Sci. 379 (2011) 488–495.

[9] M. Park, J.H. Kim, Numerical analysis of spacer impacts on forward osmosis membrane process using concentration polarization index, J. Memb. Sci. 427 (2013) 10–20.

[10] A. Sagiv, A. Zhu, P.D. Christofides, Y. Cohen, R. Semiat, Analysis of forward osmosis desalination via two-dimensional FEM model, J. Memb. Sci. 464 (2014) 161–172.

[11] M.F. Gruber, U. Aslak, C. Hélix-Nielsen, Open-source CFD model for optimization of forward osmosis and reverse osmosis membrane modules, Sep. Purif. Technol. 158 (2016) 183–192.

[12] M. Kahrizi, J. Lin, G. Ji, L. Kong, C. Song, L.F. Dumée, S. Sahebi, S. Zhao, Relating forward water and reverse salt fluxes to membrane porosity and tortuosity in forward osmosis: CFD modelling, Sep. Purif. Technol. 241 (2020) 116727.

[13] J. Schwinge, D.E. Wiley, D.F. Fletcher, Simulation of the flow around spacer filaments between narrow channel walls. 1. Hydrodynamics, Ind. Eng. Chem. Res. 41 (2002) 2977–2987.

[14] J. Schwinge, D.E. Wiley, A.G. Fane, Novel spacer design improves observed flux, J. Memb. Sci. 229 (2004) 53–61.

[15] O. Kavianipour, G.D. Ingram, H.B. Vuthaluru, Investigation into the effectiveness of feed spacer configurations for reverse osmosis membrane modules using Computational Fluid Dynamics, J. Memb. Sci. 526 (2017) 156–171.

[16] V. Geraldes, V. Semião, M.N. de Pinho, Flow and mass transfer modelling of nanofiltration, J. Memb. Sci. 191 (2001) 109–128.

[17] S. Loeb, L. Titelman, E. Korngold, J. Freiman, Effect of porous support fabric on osmosis through a Loeb-Sourirajan type asymmetric membrane, J. Memb. Sci. 129 (1997) 243–249.

[18] W.H. Press, S.A. Teukolsky, W.T. Vetterling, B.P. Flannery, Numerical recipes 3rd edition: The art of scientific computing, Cambridge university press, 2007.