Effect of Outdoor Wind on the Efficiency of Mechanical Smoke Exhaust in High-rise Building Fires

Abstract

In this paper, in order to analyze the effect of the outdoor wind on the efficiency of the mechanical exhaust system in high-rise building fires, a 15-floor high-rise building with a long corridor in Nanjing was studied. FDS (Fire Dynamic Simulation) was used to analyze the effect of different smoke exhaust models under the influence of outdoor wind. Without the outdoor wind, the CO2 concentration in the corridor was 3080ppm, natural smoke exhaust model could meet the need for evacuation. When the outdoor wind speed was 2.4m/s, the CO2 concentration in the corridor was 5042ppm, which was unable to meet the need for evacuation. Thus additional mechanical exhaust system was necessary to add for reducing the CO2 concentration in the corridor. Because the outdoor wind speed showed exponential growth with height increased, the CO2 concentration in the corridor increased with height of fire floor under the same mechanical exhaust system. The smoke exhausting volume should be redesigned, because the traditional mechanical exhaust system was unable to guarantee the people to escape safely when the fire floor was on the 12th floor or above.