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A study of the influence of the position of a chimney terminal on the vertical walls of a building on the air quality of the ventilation air supply.

Combustion appliances are used in many buildings to provide space heating and domestic hot water. These appliances emit smoke that contains pollutants that must be kept away from the ventilation air supply of the building, to limit their impact on the indoor air quality (IAQ). An efficient way to prevent those pollutants from entering the ventilation circuit is to place the chimney terminal above the top of the roof, as far as possible from the air supply openings. However, to reduce the installation costs, the chimney is often as short as possible and the terminal is mounted in a vertical wall, right next to the appliance. In this case, a minimal distance between the terminal and the ventilation openings must be determined. Methods to determine such distances can be found in several European and national standards. But most of these methods are overly simplistic and do not reflect the complexity of the physical phenomena at stake, namely the wind flow pattern around the building. The aim of this paper is to present a method, based on computational fluid dynamics simulations, that is able to determine the zones on the vertical walls of a building, with respect to the position of the chimney terminal, where the concentration of the pollutants is sufficiently low so that the air can be used for ventilation. Preliminary results show that these zones are strongly dependant on the shape of the building and on the wind direction with respect to the building. A yearly analysis of the effect of the changing wind direction on the flue gas plume on the vertical walls of the building is also presented.