Abstract
In the design of the local exhaust ventilation systems of high performance, it is of importance not only to maintain the center-line velocity as high as possible at a certain distance from the hood opening, but also to widen the high-velocity area in the direction perpendicular to the center-line for the respective contaminant sources. To meet these demands, the effects of hood geometry on the suction performance are studied in the three-dimensional flow field for freestanding circular, square and rectangular hoods. The nondimensional center-line velocity with respect to the opening is a similar distribution irrespective of hood shape and it agrees with Dallavalle's empirical formula. To elucidate the characteristics of the hood geometry, the velocity is normalized by the take-off, In this case, the center-line velocity distributions agree with each other only for the same opening ratio, irrespective of the cross-sectional geometry. The flow fields with respect to the opening in the horizontal and vertical planes including the hood axis show different velocity contours except in the case of hoods with the same flare angle. From the results of velocity contours with respect to the takeoff, the predominant regions are defined for each hood with a different area ratio. From this result, the optimum hood opening ratio can be selected in accordance with the respective sources. The flare angle of the minimum head loss, regardless of the hood geometry, was also found.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call