Clogging of fibrous filters with monodisperse aerosols
The clogging of fibrous air filters by solid aerosol particles in the inertial interception capture range was experimentally and theoretically investigated. Flat filters were loaded to particle filter cake formation at 0.10 m/s filter face velocity with monodisperse aerosols. An evaporator-condenser aerosol generator capable of producing a stable 0.6 kg/hr product of monodisperse, solid aerosols in the range 1 to 5 micrometers aerodynamic diameter was designed, fabricated, and optimized. The output aerosol was introduced into a vertical challenge duct, where the mass concentrations upstream and downstream of the filter sample, and thus the filter penetration, were measured using continuous flow sampling through two light scattering photometers. Simultaneous measurements were made of the filter flow resistance during the particle loading process. A discussion of the possible definitions of clogging is given from descriptions of the plots of the experimental filtration responses with mass challenge. The relationship between the clogging point and effective filter pore diameter for different aerosol challenges is given for medium efficiency fibreglass papers and for filters made with 15.5 micrometer diameter monodisperse fibres.