Critical Aerosol Velocity in Nonwoven Filtration, 1991 Nonwovens Conference Proceedings

In dust filtration using nonwovens, aerosol velocity significantly affects both collision and collection efficiencies. Furthermore, because of limited adhesive forces between solid particles and fibers, retention efficiency is also affected. Collision efficiency is dependent on aerodynamic forces and particle inertia, which are functions of aerosol velocity. Collection efficiency decreases when inertial forces are high enough to cause particle rebound. Collection efficiency decreases further with dust loading if aerodynamic forces overcome adhesive forces, causing redispersion of collected particles.

Aerosol velocity is considered a major factor influencing filter design. Because of shrinking space limitations in modem filter applications, filters are designed in smaller packages and, there fore, perform at higher aerosol velocities. In many cases, filter efficiency decreases because of dust reentrainment as a result of excessive aerosol velocity.

This paper focuses on the optimum aerosol velocity in nonwoven filtration. Experimental filter performance in both surface and depth type nonwovens as a function of aerosol velocity and type of dust are evaluated. Discussion of filter efficiency based on filtration theory and experimental results leads to guidelines for selection of nonwovens in air filter and prefilter applications.