Removal of elongated particle aggregates on fibrous filters

Abstract

Elongated aerosol particle removal on fibrous filters has been investigated. It was shown that particle agglomerates are removed much more efficiently compared to the regularly shaped single particles with identical electrical mobility diameter at two filtration velocities tested. The experimental results were compared with the classical filtration theory and it was shown that the theoretical predictions, which are based on the assumption that the particles are spherical, are significantly different compared to an agglomerate filtration efficiency value. In order to account for a particle shape non-regularity, dominating nanoparticle removal mechanisms were firstly evaluated for a regular particle of certain size and then adjusted by fitting coefficients k1 (for diffusion component) and k2 (for interception). These coefficients were determined by fitting the theoretical values that gives the best coincidence with the measured data points. As was further demonstrated theoretically, the coefficient k1 is identical to the ratio of the actual particle surface area to the surface area of the spherical particle of the equivalent diameter. On the other hand, the coefficient k2 was found to be equal to the ratio of the projection of a given particle on a plane perpendicular to a streamline, to that of the spherical particle of the equivalent diameter. The reported findings would allow undertaking more accurate evaluation of the removal efficiency of non-regular aerosol particle, which is especially important for industrial applications where non-regular aerosols are frequently met.