Diffusional filtration of polydispersed aerosol particles by fibrous and packed-bed filters

Diffusional filtration efficiencies of polydispersed particles by fibrous a nd granular filters were calculated in two different ways. One was an appro ximation method employing the integration of lognormal function moments and the other utilised direct numerical integration of the penetration equatio n. The results show that the filtration efficiency for a polydisperse aeros ol along the length of the filter bed column initially increases at a highe r rate than that of a monodisperse aerosol, but later the rate is gradually retarded. It is noted that all the efficiency curves cross one another in the region whew the filtration efficiency is approximately 0.6. Increase in the mean sire and decrease in the geometric standard deviation of the part icle sire distribution due to filtration by Brownian diffusion are also giv en. The results were compared with available experimental data and satisfac tory agreements obtained.