Pollutant flushing with natural displacement ventilation |
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Authors: | G.R. Hunt N.B. Kaye |
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Affiliation: | Department of Civil and Environmental Engineering, Imperial College London, Imperial College Road, London SW7 2AZ, UK |
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Abstract: | We examine the time taken to flush pollutants from a naturally ventilated room. A simple theoretical model is developed to predict the time taken for neutrally-buoyant pollutants to be removed from a room by a flow driven by localised heat inputs; both line and point heat sources are considered. We show that the rate of flushing is a function of the room volume, vent areas (A*) and the distribution, number (n) and strength (B ) of the heat sources. We also show that the entire problem can be reduced to a single parameter (μ) that is a measure of the vent areas, and a dimensionless time (τ) that is a function of B, V and μ. Small-scale salt-bath experiments were conducted to measure the flushing rates in order to validate our modelling assumptions and predictions. The predicted flushing times show good agreement with the experiments over a wide range of μ. We apply our model to a typical open plan office and lecture theatre and discuss some of the implications of our results. |
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Keywords: | Natural ventilation Transient flows Pollutant flushing |
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