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Empirical validation of theoretical velocity fields into flanged circular hoods.
Flynn MR; Ellenbecker MJ
Am Ind Hyg Assoc J 1987 Apr; 48(4):380-389
Hot film anemometry was used to test theoretical models of the three dimensional velocity field into a flanged circular hood, both with and without a crossdraft perpendicular to the hood center line. Tests were carried out to measure velocities in front of representative flanged circular hoods with no crossdraft, and the predicted results of three models were compared with the measurements. Graphs of the velocity plotted on the ordinate and the corresponding theoretical quantity on the abscissa were used to evaluate the models. With minor empirical changes, one model yielded a straight line graph indicative of the line of exact agreement. The three dimensional velocity field for a flanged circular hood functioning without crossdrafts was defined mathematically according to that model using a simple microcomputer program. The introduction of the crossdraft perpendicular to the center line of the hood was found to add a series of well determined velocity components. Hot film anemometry validated empirically the theoretical findings in the plane parallel to the direction of the crossdraft, where the theoretical velocity vectors were two dimensional. The effects of crossdrafts on hood performance were illustrated by computer generated streamline maps which were used to develop hood capture efficiency predictive models. The authors conclude that such maps can be used to define areas of field that are under control of the hood so that contaminating processes may be located appropriately.
NIOSH-Publication; NIOSH-Grant; Exhaust-hoods; Ventilation-equipment; Mathematical-models; Dust-velocity; Equipment-design; Industrial-equipment; Air-flow; Industrial-hygiene
Issue of Publication
American Industrial Hygiene Association Journal
Environmental Sci & Physiology Harvard Sch of Public Health 665 Huntington Avenue Boston, Mass 02115
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division