Sinusoidal spacers for mitigating concentration polarization in reverse osmosis
Environmental Engineering and Science
To improve the current mesh feed spacer we developed spacers with a geometry that causes sinusoidal flow patterns. These have two main advantages: unobstructed flow and adaptable geometry. First, this design allows unobstructed flow inside the membrane channel so as to minimize longitudinal pressure drop and dead zones. Second, the frequency and amplitude of the sinusoidal (along with the width and height of the flow channels) can be tuned, thus changing the crossflow velocity independent of the total module flow rate. Faster crossflow velocity is achieved with higher amplitude and frequency of the sinusoids. Analysis of the designs was accomplished using computational fluid dynamics (CFD) modeling via COMSOL Multiphysics software. The influence of spacer geometry (e.g. amplitude and frequency), applied pressure, feed velocity, and concentration were investigated to determine how concentration polarization could be reduced while maintaining low longitudinal pressure drop. Modeling data were compared and verified with experimental data to prove the accuracy of the model. Modeling data matched well with experimental data, suggesting the modeling results were reliable. More tortuous sinusoidal channels induced secondary flow in both longitudinal and cross-sectional directions. The secondary flow increased mass transfer, thus reducing concentration polarization and enhancing flux.
Xie, Peng and Ladner, David A., "Sinusoidal spacers for mitigating concentration polarization in reverse osmosis " (2013). Graduate Research and Discovery Symposium (GRADS). 65.
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