Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
INFLUENCE OF ASPECT RATIO AND WALL TEMPERATURE ON SMOKE EXHAUSTION IN A PRE-CHAMBER OF A SMOKE-PROOF STAIRCASE.
Submission Author:
Samuel Lima , ES
Co-Authors:
Samuel Lima, Airque Assis, Renato Siqueira, João Paulo Barbosa
Presenter: Airque Assis
doi://10.26678/ABCM.COBEM2021.COB2021-1943
Abstract
In fire events, the major death cause is the intoxication due to inhalation of the released gases. Since there are difficulties related to smoke control in fires, it is essential that the designed structures promote exhaustion and prevent the spread of these harmful gases. This study uses the computational fluid dynamics (CFD) to model the stratified flow in pre-chambers of smoke proof staircases. The combustion in a compartment attached to the pre-chamber was modeled using the Flamelet model so that the smoke could be generated. This study analyzed the influence of the aspect ratio of the environment, for a constant volume, as well as the wall temperature on the exhaust of combustion gases, varying from 25 °C. The results obtained show that the variation of the aspect ratio, ratio between height and width of the pre-chamber, can contribute to a better smoke exhaustion. In pre-chambers with a lower aspect ratio, a short-circuit flow behavior was noted, in which the smoke is directed to the outlet duct just after the entrance, promoting a 10% improvement in the exhaustion of smoke from the pre-chamber as compared to the reference configuration. For pre-chambers with a higher aspect ratio, a 3% improvement in smoke exhaustion was observed, however, a greater volume of smoke was retained in the environment, which impairs the air quality in it. Regarding the variation of the wall temperature, the results show that, for a positive variation of 7 °C, there was a lesser exhaustion of toxic gases, about 7%, as there was a loss of stratification effects and, consequently, a greater diffusion of gases. For higher temperatures, with a positive variation of 17 °C, there was a 2% improvement in smoke exhaustion, the effects analyzed in this situation being similar to the previous case. However, there was a greater concentration of smoke inside the pre-chamber, with regions of the dead zone being observed, which can allow a possible inhalation of toxic gases during the passage of people through the environment.
Keywords
fire control, Computational Fluid Dynamics, Smoke exhaustion, Natural Convection, Smoke-proof staircase
