Prediction and measurement of velocity into flanged slot hoods.
Conroy-LM; Ellenbecker-MJ; Flynn-MR
Am Ind Hyg Assoc J 1988 May; 49(5):226-234
A model for the design of slot hoods used for area sources located in cross draft was described using potential flow theory for determination of the velocity components in front of the flanged slot hood. The application of potential flow to a rectangular slot was discussed on the basis of the solution for an elliptical aperture with a constant potential across the hood face. Examples of computer programs that use the potential flow solution to generate streamlines of velocity in front of a hood with an elliptical aperature in the presence and absence of cross draft were presented. The velocities predicted by an equal area ellipse with the same length to width ratio as the slot and by an ellipse inscribed within the slot were compared to experimental values determined using flanged slot hoods of 7.5 and 15 inches and aspect ratios of 15:1, 10:1, and 5:1. Each hood was tested at average face velocities of 5.1, 10.2, and 15.2 meters per second in an unventilated chamber. A least squares performance index and a bias index were determined for each case. The values predicted by an inscribed ellipse provided the best fit for velocity in the x-direction, and those predicted by an equal area ellipse provided the best fit for velocity in the z- direction. A correction factor for determination of the z-velocity using the first model was calculated.
NIOSH-Publication; NIOSH-Grant; Exhaust-systems; Environmental-control-equipment; Industrial-engineering; Equipment-design; Exhaust-hoods; Exhaust-ventilation
Physiology Department, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115
American Industrial Hygiene Association Journal
Harvard University, Boston, Massachusetts