Pressure, flow, and concentration profiles in open and spacer-filled membrane channels

A finite element model was developed to study momentum and mass transport in cross flow membrane filtration systems with open and spacer-filled channels. Simulated conditions represented a range of membrane desalination applications and considered both open and spacer-filled straight through channels, as well as a geometry representing lab-scale cross flow membrane filtration cells. The finite element model agreed with classical analytical models for pressure drop, fluid shear, and concentration polarization in straight-through open channels at low flux and high cross flow. In simulations of representative lab-scale cross flow membrane filters, stagnant regions at the entrance and exit regions, as well as developing flow lead to significant deviations between analytic model and finite element model results. In spacer-filled channels, axial pressure drops were substantially higher than in open channels, varying by a factor of 2 for different spacer configurations (cavity < zigzag < submerged), while shear rates were on average enhanced, but appeared to create stagnant zones where the filaments contacted the membrane. On average, feed channel spacers reduced the extent of concentration polarization because of the enhanced wall shear rates. However, the stagnant regions (in front and behind some spacer filaments) led to enhanced concentration polarization, which suggests certain spacer designs could promote local scale and cake formation in spiral wound elements.

[1]  Ashwani Kumar,et al.  Flow visualization through spacer filled channels by computational fluid dynamics-II: improved feed spacer designs☆ , 2005 .

[2]  David F. Fletcher,et al.  Techniques for computational fluid dynamics modelling of flow in membrane channels , 2003 .

[3]  Viriato Semiao,et al.  Concentration polarisation and flow structure within nanofiltration spiral-wound modules with ladder-type spacers , 2004 .

[4]  Vítor Geraldes,et al.  Flow and mass transfer modelling of nanofiltration , 2001 .

[5]  H. Schlichting.  Boundary Layer Theory , 1955 .

[6]  S. Bhattacharjee,et al.  A Model of Membrane Fouling by Salt Precipitation from Multicomponent Ionic Mixtures in Crossflow Nanofiltration , 2002 .

[7]  Anthony G. Fane,et al.  Effect of viscosity on concentration polarization in ultrafiltration , 1988 .

[8]  Alan S. Michaels,et al.  SOLUTE POLARIZATION AND CAKE FORMATION IN MEMBRANE ULTRAFILTRATION: CAUSES, CONSEQUENCES, AND CONTROL TECHNIQUES , 1970 .

[9]  Dianne E. Wiley,et al.  CFD simulations of net-type turbulence promoters in a narrow channel , 2001 .

[10]  Menachem Elimelech,et al.  Theory of concentration polarization in crossflow filtration , 1995 .

[11]  Marc A. Deshusses,et al.  Direct observation of biofouling in cross-flow microfiltration: mechanisms of deposition and release , 2004 .

[12]  Clement Kleinstreuer,et al.  Laminar dilute suspension flows in plate- and frame ultrafiltration units , 1983 .

[13]  A. S. Berman.  Laminar Flow in Channels with Porous Walls , 1953 .

[14]  Eric M.V. Hoek,et al.  Modeling concentration polarization in reverse osmosis processes , 2005 .

[15]  R. I. Kermode,et al.  Prediction of concentration polarization and flux behavior in reverse osmosis by numerical analysis , 1990 .

[16]  M. Elimelech,et al.  Concentration Polarization of Interacting Solute Particles in Cross-Flow Membrane Filtration. , 1999, Journal of colloid and interface science.

[17]  M. C. Porter.  Concentration Polarization with Membrane Ultrafiltration , 1972 .

[18]  Lihan Huang,et al.  Finite element analysis as a tool for crossflow membrane filter simulation , 1999 .

[19]  Sandeep K. Karode,et al.  Laminar flow in channels with porous walls, revisited ☆ , 2001 .

[20]  Sunny Wang,et al.  Direct observation of microbial adhesion to membranes. , 2005, Environmental science & technology.

[21]  Lianfa Song and,et al.  Numerical Studies of the Impact of Spacer Geometry on Concentration Polarization in Spiral Wound Membrane Modules , 2005 .

[22]  Michael K. Stenstrom,et al.  An unsteady-state model to predict concentration polarization in commercial spiral wound membranes , 1999 .

[23]  M. Elimelech,et al.  Cake-enhanced concentration polarization: a new fouling mechanism for salt-rejecting membranes. , 2003, Environmental science & technology.

[24]  Menachem Elimelech,et al.  Influence of Crossflow Membrane Filter Geometry and Shear Rate on Colloidal Fouling in Reverse Osmosis and Nanofiltration Separations , 2002 .

[25]  Dianne E. Wiley,et al.  Spacer characterization and pressure drop modelling in spacer-filled channels for ultrafiltration☆ , 1994 .

[26]  P. L. T. Brian,et al.  Concentration Polar zation in Reverse Osmosis Desalination with Variable Flux and Incomplete Salt Rejection , 1965 .

[27]  G. Schock,et al.  Mass transfer and pressure loss in spiral wound modules , 1987 .

[28]  Sandeep K. Karode,et al.  Flow visualization through spacer filled channels by computational fluid dynamics I. , 2001 .

[29]  Lianfa Song,et al.  Simulations of Full-Scale Reverse Osmosis Membrane Process , 2002 .

[30]  Andrew L. Zydney,et al.  A CONCENTRATION POLARIZATION MODEL FOR THE FILTRATE FLUX IN CROSS-FLOW MICROFILTRATION OF PARTICULATE SUSPENSIONS , 1986 .

[31]  David F. Fletcher,et al.  Computational fluid dynamics modelling of flow and permeation for pressure-driven membrane processes , 2002 .

[32]  Marcel Mulder,et al.  Basic Principles of Membrane Technology , 1991 .

[33]  S. Bhattacharjee,et al.  Coupled model of concentration polarization and pore transport in crossflow nanofiltration , 2001 .

[34]  Lianfa Song,et al.  A 2-D streamline upwind Petrov/Galerkin finite element model for concentration polarization in spiral wound reverse osmosis modules , 2004 .

[35]  Dianne E. Wiley,et al.  Novel spacer design improves observed flux , 2004 .

[36]  Viriato Semiao,et al.  The effect of the ladder-type spacers configuration in NF spiral-wound modules on the concentration boundary layers disruption☆ , 2002 .