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Air Flow Generated by Flanged Suction Hoods with Adjacent Planes.
Ventilation '88 1989:47-54
The results of a theoretical and experimental study of air flow in front of flanged hoods with adjacent planes were discussed. Equations describing the air flows generated by oblong and circular orifice flanged hoods having one or two adjacent planes were derived using a contractal mapping technique. The mapping technique involved superimposing the flow velocity vectors generated by a hood orifice without an adjacent plane onto a space defined by the truncation of the flow field caused by the addition of an adjacent plane. This model predicted that the center line air flow, expressed as the ratio of the flow generated by a hood with planes to that of a hood without planes, would increase with increasing aspect ratio and decrease with decreasing aspect ratio. Experimental measurements of air flow were made with a hood having a circular orifice, radius 5 centimeters (cm), and two adjacent planes. One plane was stationary and oriented 90 degrees (deg) to the hood plane and located 11.4cm from the center of the orifice. The other plane was also oriented perpendicular to the hood plane but its angle of orientation could be varied from 45 to 90deg. Test air flow velocities varied from 0 to about 17 meters per second (m/sec). Air flow velocities generated by the hoods were measured with hot film anemometers. The predicted velocities agreed well with the experimental values for all plane orientations up to about 12 to 13m/sec. Agreement was less satisfactory at higher velocities. The authors conclude that the mapping technique should be useful as a starting point for investigating the effects of obstructions in flow fields generated by hoods.
NIOSH-Grant; Control-technology; Exhaust-hoods; Air-flow; Mathematical-models; Laboratory-testing; Equipment-design; Industrial-hygiene;
Industrial Environ Health Scis University of Pittsburgh 130 Desoto Street Pittsburgh, PA 15261
Control Technology and Personal Protective Equipment; Research Tools and Approaches; Control-technology;
University of Pittsburgh at Pittsburgh, Pittsburgh, Pennsylvania
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division