Experimental investigation of local efficiency variation in fibrous filters

Classical filtration models consider filter media as homogeneous and use an arbitrary inhomogeneity factor to account for the differences between theo ry and experiments, The variations in media-packing density have been exper imentally observed and seen to be significant. There is minimal experimenta l information on the effect of these variations on filter performance, In t his paper, local efficiency variations in commercial fibrous filters have b een obtained for varying operating conditions. A filter scanner was develop ed to measure local filter efficiencies, and the features of the scanner ar e described in detail. The variations in local efficiencies are seen to hav e a Gaussian distribution, and the operating conditions and media behavior Influence the variability in the local efficiency data. Theoretical modelin g can he used to obtain two-dimensional packing density distribution data f rom the local efficiency measurements.