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The effect of temperature differences in a room on contanimant dispersion.

Lee-E; Feigley-C; Lakshman-K; Khan-J; Ahmed-M; Tamanna-S
American Industrial Hygiene Conference and Exposition, May 8-13, 2004, Atlanta, Georgia. Fairfax, VA: American Industrial Hygiene Association, 2004 May; :14
The contaminant dispersion patterns in an enclosed space predominantly depend on airflow rate, emission rate, room configuration, and temperature differences. However, most mathematical methods for estimating room concentration only consider the airflow rate and emission rate. Here the impact of temperature difference between a wall and room air was studied in an experimental room (2.86 m(L) x 2.35 m(H) x 2.86 m(W)). Tracer gas (99.5% propylene) concentrations were monitored automatically at 144 sampling points with a photoionization detector. The north wall was chosen to represent a building's external wall and could be heated or cooled. The desired temperature was obtained by circulating heated or chilled water throllgh the copper tubes attached to tae north wall. To promote uniform wall temperature, the inside of the wall was covered by 1/16"-thick aluminum sheets. A total of 12 factorial combinations were investigated: two flow rates (5.5 and 3.3 m3/min) and six thermal conditions (one isothermal condition, three summer conditions, and two winter conditions). For the lower flow rate, winter conditions produced greater variability of concentration with location in the room (coefficient of variation (CV) = 0.99 and 1.35) than isothermal or summer conditions (CV = 0.29 to 0.35). For the higher flow rate, the CVs (CV = 0.36 to 0.43) and the room average concentrations (36.8 to 42.8 ppm) were similar for all thermal conditions. However, the dispersion patterns for isothermal and non-isothermal conditions were substantially different. This study indicates that contaminant dispersion patterns depend upon both flowrate and temperature difference. The effect of temperature difference, especially for simulated winter conditions, was much more pronounced at the lower flow rate, causing more spatial variability of concentration within the room. Thus, mathematical methods for estimating room concentrations are expected to be less precise at lower flow rates.
Air-flow; Air-contamination; Air-quality; Emission-sources; Temperature-effects; Sampling; Air-sampling
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American Industrial Hygiene Conference and Exposition, May 8-13, 2004, Atlanta, Georgia
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University of South Carolina at Columbia, Columbia, South Carolina