Filter loading with liquid aerosols.
Earnest-G; Chen-D; Pui-D
American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida. Fairfax, VA: American Industrial Hygiene Association, 2000 May; :22-23
Filter pressure drop and collection efficiency have been evaluated for fibrous filters as they were loaded with polydisperse liquid aerosols. This fundamental study relates to the control of worker exposures to metalworking fluid (MWF) mists. Test aerosols included MWFs and simple organic liquids to provide a range of densities, viscosities, and surface tensions. Filters consisting of either synthetic or natural fibers with packing densities from 0.01 to 0.10 were tested. Fiber wetting and liquid-fiber contact angle was evaluated. Face velocities ranged from 10 crnls to 150 crnls. The computer-controlled system operated and maintained the airflow rate, particle counter, and data transfer. A laser particle counter sampled air upstream and downstream of the filter. This counter samples particles in the range of 0.3-25 microm. Pressure drop across the filter and fractional collection efficiency was generally found to increase as the filters were loaded with polydisperse liquid aerosols; however, for conditions of both low-face velocities and low-packing densities, temporary reductions in fractional collection efficiency were observed. The efficiency reductions typically occurred for submicron aerosol diameters; however, they occasionally occurred at larger diameters. Mathematical models were developed to describe changes in pressure drop across the filter and collection efficiency during loading. The pressure drop model was based largely on the theory of flow of fluids through porous media. Filter pressure drop and collection efficiency appeared to be strongly influenced by the face velocity and the revised packing density resulting from collected liquid.
Filters; Fluids; Aerosols; Metalworking-fluids; Oil-mists; Employee-exposure; Work-environment; Control-methods; Control-systems; Control-technology; Viscosity; Tension; Organic-compounds; Surface-properties; Filter-materials; Fibrous-bodies; Testing-equipment; Particle-aerodynamics; Particle-counters; Air-filters; Air-flow; Computers; Air-sampling-equipment; Air-sampling-techniques; Equipment-reliability; Lasers; Mathematical-models
American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida