Experimental Investigation of Local Efé ciency Variation in Fibrous Filters

Classicale ltrationmodelsconsidere ltermediaashomogeneous and use an arbitrary inhomogeneity factor to account for the differencesbetweentheoryandexperiments.Thevariations inmediapacking density have been experimentally observed and seen to be signie cant.Thereisminimalexperimentalinformationontheeffect of these variations on e lter performance. In this paper, local efe ciency variations in commercial e brous e lters have been obtained for varying operating conditions. A e lter scanner was developed to measure local e lter efe ciencies, and the features of the scanner are described in detail. The variations in local efe ciencies are seen to have a Gaussian distribution, and the operating conditions and media behavior ine uence the variability in the local efe ciency data. Theoretical modeling can be used to obtain two-dimensional packingdensitydistributiondatafromthelocalefe ciencymeasurements.