Graphical Approximation Model for Velocity Characteristics of Local Exhaust Inlets

Abstract

The purpose of this study was to prepare a computer design model for approximating velocity characteristics of local exhaust inlets. The model provides approximate constant velocity contours for plain and flanged exhaust inlets having circular, rectangular and narrow slot end shapes. Configurations include single inlets, two identical inlets, a single inlet with a nearby boundary surface, and a single inlet in the presence of a crossdraft. The model is designed for use on a personal computer by individuals having a basic understanding of local exhaust inlet design. The model applies several major approximations to obtain mathematical representations of velocity contours and to utilize and expand the application of existing empirical data for centerline velocity gradients for different shapes of exhaust inlets. A graphical “contour displacement” method is used to minimize and hasten computations for user-specified velocity contours. The model also provides comparisons of the empirical results of different investigators and offers a means for approximating velocities at points in the airflow specified by the user. Despite uncertainties in accuracy of the approximations, the model may serve as a useful design and training aid. It may be developed further as a tool for designing local exhaust inlets.