Shortcut design method for reverse osmosis tubular module

the effect of varying transmembrane pressure and concentration polarization

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

A good shortcut design method of tubular membrane modules provides a more accurate estimate of the size or area of the module required for a given separation duty and hence its cost. A previous shortcut design method based on the cross-flow nature of the membrane developed by the author considered only a constant trans-membrane pressure and a constant polarization. The pressure drop along the tube due to friction decreases the transmembrane pressure along the tube that is available to drive the flux resulting in a decrease in the flux across the membrane further down the tube. Concentration polarization along the tube would also lead to a decrease in flux. Both tends to decrease the overall size of the membrane area. This paper proposes to extend the cross-flow design method to include the effect of trans-membrane pressure drop and concentration polarization along the tube. The number of transfer unit (NTU) for reverse osmosis is found to depend on four parameters: the rejection, R, the recovery, S, the dimensionless applied transmembrane pressure, ψ, the polarization represented by Peclet number, Pe, and the pressure drop ratio, ΔPf/ΔPT. It was found that the pressure drop along the membrane tubes does not generally affect the NTU and hence the area of the membrane required for the separation. It only increases slightly the NTU and hence the area at lower transmembrane pressure, low recovery and high rejection. At high rejection, the NTU and hence the area increase slightly with higher polarization but decrease slightly at low rejection.

Original languageEnglish
Pages (from-to)297-305
Number of pages9
JournalDesalination
Volume201
Issue number1-3
DOIs
Publication statusPublished - 30 Nov 2006

Fingerprint

Reverse osmosis
design method
polarization
Polarization
membrane
Membranes
pressure drop
Pressure drop
Fluxes
Recovery
Peclet number
effect
reverse osmosis
low pressure
friction
Friction
cost

Keywords

  • Height of a transfer unit
  • Membrane area
  • Number of transfer unit
  • Polarization
  • Pressure drop

ASJC Scopus subject areas

  • Filtration and Separation

Cite this

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abstract = "A good shortcut design method of tubular membrane modules provides a more accurate estimate of the size or area of the module required for a given separation duty and hence its cost. A previous shortcut design method based on the cross-flow nature of the membrane developed by the author considered only a constant trans-membrane pressure and a constant polarization. The pressure drop along the tube due to friction decreases the transmembrane pressure along the tube that is available to drive the flux resulting in a decrease in the flux across the membrane further down the tube. Concentration polarization along the tube would also lead to a decrease in flux. Both tends to decrease the overall size of the membrane area. This paper proposes to extend the cross-flow design method to include the effect of trans-membrane pressure drop and concentration polarization along the tube. The number of transfer unit (NTU) for reverse osmosis is found to depend on four parameters: the rejection, R, the recovery, S, the dimensionless applied transmembrane pressure, ψ, the polarization represented by Peclet number, Pe, and the pressure drop ratio, ΔPf/ΔPT. It was found that the pressure drop along the membrane tubes does not generally affect the NTU and hence the area of the membrane required for the separation. It only increases slightly the NTU and hence the area at lower transmembrane pressure, low recovery and high rejection. At high rejection, the NTU and hence the area increase slightly with higher polarization but decrease slightly at low rejection.",
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AB - A good shortcut design method of tubular membrane modules provides a more accurate estimate of the size or area of the module required for a given separation duty and hence its cost. A previous shortcut design method based on the cross-flow nature of the membrane developed by the author considered only a constant trans-membrane pressure and a constant polarization. The pressure drop along the tube due to friction decreases the transmembrane pressure along the tube that is available to drive the flux resulting in a decrease in the flux across the membrane further down the tube. Concentration polarization along the tube would also lead to a decrease in flux. Both tends to decrease the overall size of the membrane area. This paper proposes to extend the cross-flow design method to include the effect of trans-membrane pressure drop and concentration polarization along the tube. The number of transfer unit (NTU) for reverse osmosis is found to depend on four parameters: the rejection, R, the recovery, S, the dimensionless applied transmembrane pressure, ψ, the polarization represented by Peclet number, Pe, and the pressure drop ratio, ΔPf/ΔPT. It was found that the pressure drop along the membrane tubes does not generally affect the NTU and hence the area of the membrane required for the separation. It only increases slightly the NTU and hence the area at lower transmembrane pressure, low recovery and high rejection. At high rejection, the NTU and hence the area increase slightly with higher polarization but decrease slightly at low rejection.

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