Gas characteristics and effectiveness of smoke control systems in elevator lobbies during elevator evacuation in a high-rise building fire

Elevator evacuation has attracted increasing attention as an efficient transport method in high-rise buildings, which is one of the most complex and interesting areas of modern fire research. Through a 3D numerical model built from ANSYS Fluent, this paper studied the influence of elevator motion on the gas characteristics as well as the effectiveness of the smoke control system in the lobby during elevator evacuation in a high-rise building fire. Pressure distribution, temperature distribution and CO concentration distribution in the elevator lobby were analyzed. It was found that the elevator motion decreased the pressure in the elevator lobby while increased the temperature and CO concentration, which indicated that more fire smoke had spread into the lobby when the elevators moved and the effectiveness of the smoke control systems had been weaken. When the elevator velocity was increased from 0m/s to 2m/s, the lowest pressure in the lobby was decreased by 566.7%; the temperature line was mostly above the line representing the still elevator; the CO concentration experienced the most change at the height of 2m: the highest CO concentration was, respectively, increased by 30.4% and 26.7% when the air supply volume (q(s)) was 0m(3)/h and 20000m(3)/h. As the air supply volume in the lobby increased, the pressure was increased while the temperature and the CO concentration was decreased. Changes of temperature lines and CO concentration lines under various air supply volumes were very similar. When q(s) was increased from 0m(3)/h to 20000m(3)/h, the pressure in the lobby was increased from 0Pa to around 8Pa, the highest temperature and CO concentration were decreased by 23.8% and 87.5%, respectively.