Effects of shape, size, and air velocity on entry loss factors of suction hoods.
McLoone-HE; Guffey-SE; Curran-JP
Am Ind Hyg Assoc J 1993 Mar; 54(3):87-94
The effects of air velocity, aspect ratio, and area ratio on entry loss factors of suction hoods were examined. Entry loss factors were measured for 20 square and rectangular hoods with a major included angle of 90 degrees. All hoods had a major taper angle of 45 degrees. The hoods were connected to a ventilation test system; mean air velocities in the duct ranged from 320 to 1770 meters/minute. Pitot tubes connected to piezoresistive pressure transducers and inclined tube monometers were used to measure static and velocity pressures. The entry loss factors, the ratio of hood total pressure loss to mean velocity pressure, ranged in value from 0.17 to 1.85 and were not dependent on aspect ratio but were dependent on area ratio. With increasing air velocity the entry loss factors decreased. This decrease ranged from 1 to 2% for each 100 meters/minute increase in air velocity. This may have been due to the hood's effect on pressure loss due to friction along straight ducts beyond the hood throat.
NIOSH-Publication; NIOSH-Grant; Training; Ventilation-systems; Ventilation-equipment; Exhaust-hoods; Air-flow
Environmental Health University of Washington Environmental Health Dept Seattle, Wash 98195
American Industrial Hygiene Association Journal
University of Washington, Seattle, Washington