Concentration distribution in a ventilated room under isothermal conditions.

The work in this paper contributes to the work in the IEA - Annex 20 "Air Flow Patterns within Buildings" and presents a series of full-scale measurements of the concentration distribution in a room with isothermal mixing ventilation. Vertical profiles of the concentration in the middle of the room have been measured under different conditions. With the contamination source in the middle of the room the vertical profiles were changed radically with an increase of the air change rate from n= 1.5h^-1 to n=6h^-1 due to a change in the flow structure in the room. With a constant air change rate the location of the contamination source in the room showed a great idluence on the vertical profile. A high velocity around the contamination source resulted in a uniform contaminant distribution in the room, while a low velocity resulted in considerable differences. Contours of concentration in the centre plane of the room have been measured using different contaminant densities. The densities were low, neutral and high in relation to the density of air. The results showed that the contaminant distribution in the room with the chosen flow conditions depended strongly on the contaminant density, and that the high density case gave the highest concentrations in the occupied zone.