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The paradox of mixing in industrial ventilation.
Feigley C; Lee E; Khan J; Bennett J
American Industrial Hygiene Conference and Exposition, June 1-6, 2002, San Diego, California. Fairfax, VA: American Industrial Hygiene Association, 2002 Jun; :24
Deviations of dilution ventilation equations often assume that a workroom is well-mixed. A flow rate requirement computed using one of these equations is then multiplied by a safety factor, the portion of which accounting for deviations from complete mixing has been called the mixing factor (Km). Here the scale (S) and intensity of mixing (I) were determined for full-scale experiments at 2 Reynolds numbers and 2 Archimedes numbers, and for computational fluid dynamic simulations of workrooms of various configurations and 5 Reynolds numbers under steady, isothermal conditions. The relationships among Km S, and I were explored. In general, the Km required decreased with increased mixing. A cursory consideration of these results suggests increasing mixing to reduce the Km value, and thus the required flow rate. However, this is isadvisable if increasing room air movement might interfere with other exposure control methods that rely on keeping incoming clean air and source emissions segregated.
Industrial-ventilation; Work-environment; Simulation-methods; Air-purification; Exhaust-ventilation; Ventilation-systems; Air-flow; Models
American Industrial Hygiene Conference and Exposition, June 1-6, 2002, San Diego, California
SC; OH; CA
University of South Carolina at Columbia, Columbia, South Carolina
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division