Impact of Large-Scale Effects on Mass Transfer and Concentration Polarization in Reverse Osmosis Membrane Systems

Hariswaran Sitaraman, Ilenia Battiato

Research output: Contribution to journalArticlepeer-review

7 Scopus Citations


We present well-resolved computational fluid dynamics simulations of a large-scale reverse osmosis membrane-spacer configuration (∼ 1 m). Our computational model solves the flow and transport equations with variable solute-dependent properties. We utilize a high resolution computational mesh to resolve all relevant length scales associated with spacer-induced mixing and thin concentration boundary layers. An important contribution of this work is the development of a modified mass-transfer correlation that accounts for the development of the concentration boundary layer along the channel. A set of 2D axisymmetric simulations were performed for a spiral wound module layer with varying cross-flow conditions and spacer diameters which indicate a significant entrance length effect for concentration profile development at lower flow rates while mixing effects dominate at higher flow rates. The mass-transfer correlations at higher flow rates compare well with published correlations while a surrogate model for Sherwood number was obtained that depends on an additional similarity variable that accounted for entrance length effects at lower flow rates. Finally, a large-scale membrane-spacer design relevant to high-pressure reverse osmosis is studied with a non-uniform arrangement of spacers, which indicate a substantial saving in pressure drop (∼ 40%) compared to traditional uniformly spaced pattern with minor variations (∼ 2%) in concentration polarization, product water quality (∼ 1%) and water recovery (∼ 7%) compared to a uniform spacer pattern.

Original languageAmerican English
Article numberArticle No. 122121
Number of pages13
JournalSeparation and Purification Technology
StatePublished - 15 Dec 2022

Bibliographical note

Publisher Copyright:
© 2022

NREL Publication Number

  • NREL/JA-2C00-82030


  • Computational fluid dynamics
  • Concentration polarization
  • Mass transfer
  • Reverse osmosis


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