3304 -- Calculation of Minimum Available Atmospheric Dilution Downwind of Building Exhausts

Examines equations recommended in the ASHRAE Handbook - 1989 Fundamentals, chapter 14, for prediction of minimum atmospheric dilution for use in exhaust system design. States the equations have no terms representing the larger dilutions in the plume below the centreline, and therefore yield overly conservative estimates of dilution at receptors at the lower edges of elevated plumes. Notes that the equations contain empirical constants that could be adjusted to provide more realistic dilution estimates, but no guidelines are offered in the Handbook for such adjustment. Describes an alternative approach using a jet plume model and compares model predictions with dilution observations taken in a wind tunnel model test of a laboratory building.

KEYWORDS: Calculating, buildings, exhaust air, ventilation, designing, air pollution, experiment, wind tunnels, jets, air flow.