Dilution of toxic gases and smoke emissions from residential chimneys using a low-cost cap

Dilution of toxic gases and smoke emissions from residential chimneys using a low-cost cap

Smoke and toxic gases emitted from chimneys present health hazard. Their concentration should be minimised before reaching the ground. The wind lowers the concentration before it reaches the surface. However, heavier than air toxic gases flow downward which is particularly problematic in the case of low wind speeds in high-density populated areas. Two effective solutions are to extend the height of the chimney or to employ a filter but generally these solutions are not practical or economical for residential applications. An innovative low-cost chimney cap is proposed to dilute toxic gases within the chimney before ejection. The configuration of the cap is inspired from chambers which are currently used to generate fire-whirl in the laboratory. The cap consists of two identical half cylinders which are placed off-centre at the top of the chimney. The previous experiments indicate that the entrained air swirls around the central vertical axis of the chamber and generates a whirling motion. The chimney discharge and the exhaust concentration are computed by modelling the cap. The computational results indicate that such a configuration not only is able to reduce the concentration of the discharge, but also is able to increase the discharge at low wind speeds.

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