Dust filtration and loading by fibrous and foam media

The purpose of this study is to investigate the filtration characteristics of low to medium efficiency air filters. In the first part, the pressure drops, particle collection efficiency, and dust loading behavior of 20 to 110 pores per inch foam media were measured. Pressure drop was measured from 25 to 800 cm/s; collection efficiency was measured from 250 to 650 cm/s using sodium chloride particles (0.3 to 10 {dollar}mu{dollar}m diameter and a laser particle counter. Dust loading experiments were performed to determine filter life.; It was found that the filtration characteristics were strongly dependent on the pore count. Particle collection was dominated by inertial impaction. Particle bounce was important at high flow velocity ({dollar}>{dollar}400 cm/s).; A generalized model was developed to predict the performance and life of foam filter based on the pore count and other parameters. The model was used to analyze and optimize multi-layered foam filters.; In the second part, experiments were performed to study the pressure drops, collection efficiencies, and dust loading behavior of low to medium quality fibrous filters. Experimental efficiencies were compared to existing theories and good agreements were found.; In another study, a bimodal test dust was developed to study the effects of particle size on filter life. The test dust was obtained by mixing different mass ratios of Arizona road dust (coarse mode) and submicron alumina particles (fine mode). It was shown that the particle size has a significant effect on filter life, and the specific dust-cake constant varied nonlinearly with the mass ratio.; Finally, the two dimensional Navier-Stokes equations were solved numerically to obtain the steady flow past arrays of cylinders at moderate Reynolds number, Re (1 to 150). Particle trajectories were solved to determine the single fiber efficiency. The interception parameter, R, was varied from 0.1 to 1, and particle Stokes number, Stk, from 0.1 to 50. At Reynolds number between 10 and 50, a recirculation wake was formed behind the cylinders. Interception and impaction efficiencies were enhanced at higher Reynolds number. The increase in interception efficiency was proportional to R{dollar}sp{lcub}1.5{rcub}{dollar}Re.