Lumen mass transfer in hollow-fiber membrane processes with constant external resistances
- Inst. Superior Tecnico, Lisboa (Portugal)
Membrane processes have recently become an accepted unit operation for a wide variety of separations in industry and in environmental applications. Hollow-fiber membrane processes with a constant external resistance having a constant or variable shell concentration resulting from an operational mode of cocurrent or countercurrent are studied. By solving numerically the continuity mass-conservation equation with the corresponding boundary conditions, the lumen laminar mass-transfer coefficients for both cases are correlated. The correlations greatly improve the calculating accuracy of the overall mass-transfer coefficient and can be used to obtain the lumen mixed-cup concentration by an algebraic equation substituting the partial differential equation. A separation factor m{prime} is introduced to characterize the effect of the operational mode. Calculation results demonstrate that the lumen mass-transfer coefficient is independent of the real lumen and shell concentrations, but it is greatly influenced by m{prime}. The countercurrent mode, compared to the cocurrent mode, provides not only a higher mean driving force, but a higher lumen mass-transfer coefficient. This conclusion is novel and valid for the tube-shell heat or mass-transfer processes and is supported by the experimental data in the literature and the authors` gas membrane separation experiments.
- OSTI ID:
- 556727
- Journal Information:
- AIChE Journal, Vol. 43, Issue 8; Other Information: PBD: Aug 1997
- Country of Publication:
- United States
- Language:
- English
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