EXPERIMENTAL-VERIFICATION OF THE SHEAR-INDUCED HYDRODYNAMIC DIFFUSION-MODEL OF CROSS-FLOW MICROFILTRATION

Two series of experiments were conducted to determine the validity of the shear-induced diffusion model of crossflow microfiltration (Romero and Davis, 1988,1990). In one series, a rectangular glass-walled crossflow microfilter was used under conditions for which a thick stagnant particle layer formed against the membrane with negligible flux decline. Measurements of the particle layer thickness profiles at steady state agree reasonably well with the predictions of the theory. In particular, the layer thickens with increased particle concentration, increased transmembrane pressure drop, and decreased shear rate. Initial rates of the particle layer buildup in the rectangular microfilter are also in good agreement with theoretical predictions, which are essentially the same as those for dead-end filtration. In the second series of experiments, a commercial tube-bundle was used under conditions for which a moderate flux decline occurred. Computer-aided data collection permitted rapid and accurate measurements of permeate flux. The transient and steady-state flux responses under varying operating conditions agree with the theoretically predicted responses, with application of the Blake-Kozeny correlation for the specific cake resistance as a function of particle size.