Center-line Velocity Models for Flanged Local Exhaust Openings

Abstract

Abstract Local exhaust systems are important in controlling exposures. Recently, there has been a great deal of interest in predicting hood flow patterns in order to determine effectiveness. This article presents a generalized approach, based in potential flow theory, to develop the hood center-line air velocity models directly for flanged openings of practical geometries. These were the rectangle, the square, the circle, and the slot. Measurements of the center-line velocities for a flanged circular opening were conducted to determine the validity of the potential flow assumption. Agreement of the theoretical model with experimental data indicates that the potential flow approximation applies to flow into unobstructed exhaust hoods. The theoretical models for the circle, the rectangle, and the slot were also compared to the empirically based equations found in the Industrial Ventilation Manual. Good agreement between the empirical and theoretical models was noted in the case of circular openings and in t...