Direction of Fluid Flow and the Properties of Fibrous Filters

Abstract

The influence of the fluid flow direction (downflow and upflow) on the filtration properties of filters that have a fibrous structure is investigated. It is concluded that selectivity of these filters (dependence of the filter efficiency on the particle size) in the case of upflow is changed—in comparison with the case of down-flow—in three ways: the position of the minimum of this dependence is shifted to larger particle sizes, and the whole selectivity is decreased and simultaneously deformed. Corresponding equations for this shift and changes are derived and analyzed. Theoretical predictions are compared with available experimental data. In all cases qualitative agreement and in some cases quantitative agreement is found.