Maximizing the capacity and life of depth‐type filters

摘要

AbstractAn analytical expression has been derived for the variation of the filtration coefficient of depth‐type filters with fractional depth from the downstream to the upstream face of the medium which satisfies the condition of identical retention in every cross‐section of the medium. A numerical example has been worked out for a fibrous filter where the porosity of the medium was varied to comply with the required variation of the filtration coefficient. It has been shown also that a filter consisting of three uniform layers of different porosities may adequately approximate the required continuous variation of the filtration coefficient. After a retention of 10 pore volume of dust the permeability of the three‐layer medium is about 4 times greater than that of a medium of uniform initial porosity characterized by identical initial collection efficiency, thickness and fiber dia