Previous full scale experiments gave us a global and qualitative understanding of the gas circulation in a ventilated room in case of fire. In order to go thoroughly in the knowledge of these phenomena, we have built a scale model to perform more precise temperature measurements and more complete tracer gas experiments. The results show the existence of two zones when the air inlet is near the floor. At the opposite, when it is near the ceiling the room can be considered as a one single zone.
Ventilating a fire compartment during operational fire fighting procedures may have unpredictable consequences. In some cases the ventilation is advantageous: the hot gases are removed from the fire enclosure, the visibility improves and the enclosure cools down. In some cases the opposite happens: with the accelerated burning rate, more smoke is spread around, and the temperatures rise. The most dramatic consequence is the initiation of a backdraft, where the pyrolyzed gases ignite instantaneously, in the worst case causing a severe explosion.
This paper reports on the analysis of historical wind data from 239 stations in the United States and 146 stations in Canada to derive design wind speeds (95%, 97.5%, and 99%) for the design of smoke control systems. As part of the analysis, the data were thoroughly checked for missing observations, internal consistency, and uniformity of location and measurement height.
A time constant has been proposed to characterize the time it takes to fill an atrium space with smoke for design purposes. This was defined through the use of the empirical equation expressing the mass entrainment rate to the 312 power of the clear height. However, the equation holds only when the flame tip touches the smoke layer, and the flame temperature was taken to be 1100 K (827°C 1521°F).
This paper presents results of a project initiated by ASHRAE and the National Research Council of Canada. The project applies both physical and numerical modeling techniques to atrium smoke exhaust systems to investigate the effectiveness of such systems and to develop guidelines for their design. This paper compares experimental results obtained from testing a physical model of a mechanically exhausted atrium space with results of two sets of numerical predictions of the same space.
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