IN-91-03-3 -- The Effect of Stack Height, Exhaust Speed, and Wind Direction on Concentrations from a Rooftop Stack ✓ Most Recent

Examines the results of a wind-tunnel study, first reported by Hoydysh and Schulman (1987), that was designed to provide data on the effects of stack height, exhaust speed, and wind incidence angle on the dispersion of rooftop exhausts. A total of 32 tests were conducted for a nonbuoyant tracer gas release from a stack mounted in the centre of a squat building. Tests were performed for two wind directions, four ratios of exhaust speed to wind speed, and four stack heights. Tracer gas concentrations were measured at 31 locations on the building roof, lee wall, near wake, and far wake. The experimental data are analysed and compared to earlier reported work. A simple mathematical model is assembled from the concentration-distance relationships of Wilson and Britter (1982) and the turbulent wake relationships proposed by Wilson (1979) and Fackrell (1982, 1984). The model is compared with a portion of the wind-tunnel observations.

KEYWORDS: stack effect, height, exhaust gases, roofs, flues, comparing, calculating, wind tunnels, testing, steady state, content, speed, winds, tracers, buildings, turbulent flow, pipe stacks