The effect of dust loading on penetration and resistance of glass fiber filters

Abstract

As glass fiber filters become loaded with solid particles, their resistance to airflow increases and penetration at a given flow rate decreases. In the present study, we measured the effect of loading on resistance and penetration for three types of loading dust with Mass Median Aerodynamic Diameter (MMAD) from 0.8 to 7.5 μm, and mass loading up to 2.2 mg/cm2. Penetration as a function of particle size and resistance measurements were made for five loading conditions, seven face velocities (0.04–3.38 cm/s), and 12 particle sizes (0.137–3.65 μm). As expected, loading modified filter performance to give greater resistance and lower penetration. Unit mass loading by the finer loading dust caused a greater increase in resistance and a greater decrease in penetration than did the coarser dusts. A computer model to predict the effect of loading on resistance and penetration was prepared. The model uses modified single-fiber filtration theory to estimate resistance and penetration. It assumes that solid particles deposited on a fiber act like additional short “fibers” having a diameter equal to the diameter of average mass of the loading dust. Loading directly affects only the average fiber diameter and the filter solidity, but these two parameters affect all single-fiber collection mechanisms. For the conditions of these experiments, resistance increased linearly with loading, particle size of maximum penetration changed little with loading, and penetration decreased more rapidly for initial loading than subsequent loading. The change in measured resistance and the change in model predicted resistance were correlated with a correlation coefficient (r) of 0.87. The model correctly predicted the trend in penetration with loading for each of the three loading particle sizes. © 1997 American Association for Aerosol Research.