Abstract

This paper presents results from a wind tunnel study of near-field pollutant dispersion from rooftop emissions of two multiple building configurations. The configurations mainly consisted of an emitting building in the presence of an upstream and a downstream building. The various parameters that were varied include: stack height (hs), stack location (Xs), spacing between upstream and emitting building (S1), spacing between downstream and emitting building (S2) and exhaust momentum ratio (M). Gas concentrations were measured at various building surfaces using a gas chromatograph. The wind tunnel dilutions were also compared to ASHRAE, 2007 and 2011 models. Results show that a taller upstream and a taller downstream building inhibit the plume from dispersing, thereby increasing the pollutant concentrations on the roof of the emitting building and leeward wall of the upstream building. In general, the spacing between the upstream and emitting buildings, besides the heights of each building were found to be critical parameters influencing the plume characteristics. ASHRAE, 2007 predictions were found to be overly conservative for the isolated building, while ASHRAE, 2011 estimates compared well with experimental data for a few cases. Safe placement of stack and intake on various building surfaces to avoid plume re-ingestion are suggested based on this study.