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The application of gas sparging during filtration is now a common strategy used forfouling control in membrane processes. This strategy is especially popular in processesusing submerged hollow fiber membranes. Although the benefits of gas sparging arewell known in terms of permeate flux enhancement, an understanding of how fluxenhancement is achieved via gas sparging is currently lacking. This knowledge gappresents an impediment in designing optimized submerged membrane processes froman energy perspective.The main reason for the knowledge gap discussed above is due to the fact that thehydrodynamic conditions inside an unconfined, gas-sparged submerged hollow fibermodule are not well understood. In confined systems such as tubular membranes,favorable fouling control and flux enhancement is linked to specific hydrodynamicconditions (i.e. shear profile) induced by dual-phase flow near membrane surfaces. Forunconfined submerged hollow fiber modules, however, very little information is availablein terms of the flow dynamics induced by gas-sparged two-phase flow, and the resultingshear profiles that exist near membrane surfaces. An understanding of the mechanismsof flux enhancement, and the subsequent design of optimized submerged membraneprocesses, therefore depends on acquiring a good understanding of the hydrodynamicconditions that exist inside gas-sparged submerged hollow fiber membrane modules.The results presented in the present paper are part of a larger effort currently underwayto investigate the hydrodynamic conditions in a gas-sparged submerged hollow fibermembrane module, and its relationship to flux enhancement. This paper is anextension of the study undertaken earlier by Chan et al., in which typical shearprofiles in a submerged hollow fiber membrane module were studied. In the presentstudy, the directional shear stress acting on different radial sections of a fiber resultingfrom dual-phase (gas-liquid) flow, was measured for different gas flow rates, and for gasdelivered through different gas nozzle sizes. Shear stress measurement was based onthe electrochemical method. The effect of physical contact between fibers on the fibersurface shear profile was also investigated. Includes 6 references, figures.

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Edition: Vol. - No. Published: 03/01/2007 Number of Pages: 11File Size: 1 file , 560 KB