Correlations for concentration polarisation and pressure drop in spacer-filled RO membrane modules based on CFD simulations
File(s)
Published version
Author(s)
Gu, Boram
Adjiman, Claire
Xu, Xiao
Type
Journal Article
Abstract
Empirical correlations for mass transfer coefficient and friction factor are often used in process models for reverse osmosis (RO) membrane systems. These usually involve four dimensionless groups, namely Reynolds number (Re), Sherwood number (Sh), friction factor (f), and Schmidt number (Sc), with the associated coefficients and exponents being obtained by fitting to experimental data. However, the range of geometric and operating conditions covered by the experiments is often limited. In this study, new dimensionless correlations for concentration polarization (CP) modulus and friction factor are presented, which are obtained by dimensional analysis and using simulation data from computational fluid dynamics (CFD). Two-dimensional CFD simulations are performed on three configurations of spacer-filled channels with 76 combinations of operating and geometric conditions for each configuration, covering a broad range of conditions encountered in RO membrane systems. Results obtained with the new correlations are compared with those from existing correlations in the literature. There is good consistency in the predicted CP with mean discrepancies less than 6%, but larger discrepancies for pressure gradient are found among the various friction factor correlations. Furthermore, the new correlations are implemented in a process model with six spiral wound modules in series and the predicted recovery, pressure drop, and specific energy consumption are compared with a reference case obtained by ROSA (Reverse Osmosis System Analysis, The Dow Chemical Company). Differences in predicted recovery and pressure drop are up to 5% and 83%, respectively, highlighting the need for careful selection of correlations when using predictive models in process design. Compared to existing mass transfer correlations, a distinct advantage of our correlations for CP modulus is that they can be directly used to estimate the impact of permeate flux on CP at a membrane surface without having to resort to the film theory.
Date Issued
2021-05-01
Date Acceptance
2021-04-29
Citation
Membranes, 2021, 11 (5)
ISSN
2077-0375
Publisher
MDPI AG
Journal / Book Title
Membranes
Volume
11
Issue
5
Copyright Statement
© 2021 by the authors.Licensee MDPI, Basel, Switzerland.This article is an open access articledistributed under the terms andconditions of the Creative CommonsAttribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)
License URL
Sponsor
BP International Limited
Grant Number
Order No. 75195/ICAM10 (IC)
Subjects
Science & Technology
Life Sciences & Biomedicine
Physical Sciences
Technology
Biochemistry & Molecular Biology
Chemistry, Physical
Engineering, Chemical
Materials Science, Multidisciplinary
Polymer Science
Chemistry
Engineering
Materials Science
reverse osmosis (RO)
feed spacers
computational fluid dynamics (CFD)
concentration polarization (CP)
pressure drop
correlations
MODEL
computational fluid dynamics (CFD)
concentration polarization (CP)
correlations
feed spacers
pressure drop
reverse osmosis (RO)
0904 Chemical Engineering
0905 Civil Engineering
0907 Environmental Engineering
Publication Status
Published
Article Number
ARTN 338