Effect of the fibre diameter polydispersity on the permeability of nonwoven filter media

Abstract

AbstractThis paper studies the permeability values of air filter media obtained by 3‐D simulations using the GeoDict® code. 3‐D fibrous structures with different specific characteristics that can be encountered in air filtration (0.03 ≤ solid volume fraction [α] ≤ 0.25, monodisperse fibres [1 μm ≤ df ≤8 μm], or polydisperse fibres) were generated. For monodisperse fibres, the permeability values obtained were compared with various correlations identified in the literature. After confirming that Davies' or Jackson and James' relations allowed a good estimate of the permeability, it is shown that the modified Happel's correlation provides a better prediction. In the case of normal (standard deviation: σ ≤ 1.5) or lognormal fibre size distribution (geometric standard deviation: σG ≤ 2), this modified Happel's correlation, in which the fibre diameter is replaced by an equivalent fibre diameter, leads to a relative deviation of less than ±8% and ±4% for lognormal and normal fibre distributions, respectively. The comparison with experimental permeability values obtained on real media provides quite encouraging results.