Influence of the rates of gas flows through the smoke-removal and input-ventilation systems on the height of the smoke-free zone in a fire within a building

Integral, zonal, and empirical methods of calculating the mass rate of the gas flow through the smoke-removal system in the case of fire in a building were considered. Numerical experiments on investigation of the influence of the flow rates of the smoke removed and the cold air supplied by the input-ventilation system on the height of the smoke-free zone in a model fire within a building have been carried out. It is shown that, in the case where cold air is blown into the near-ceiling layer zone, to prevent the propagation of smoke to the adjacent rooms it is necessary to substantially increase the rate of gas flow through the smoke-removal system. It has been established that the simulation of a combustion region in the form of a point heat source positioned lower relative to the combustion surface gives incorrect results. It is shown that, in the integral and zonal models, account must be taken of the fact that air is entrained from the cold-air zone through the lower boundary of the near-ceiling layer by the smoke-removal system.