Flame height and thermal environment of fires in a non-combustible shaft under the stack effect

Shafts are essential, and play a significant role in high-rise buildings. Nevertheless, the adverse effect of the shaft, which increases flames spread rate in high-rise buildings under the stack effect, is accompanied with fire safety. This paper focuses on obtaining the theoretical flame height and thermal environment for fires in the shaft based on experimental information. Bench-scale experiments were carried out in a large, confined space to reveal the motion of the flame in a non-combustible shaft. It shows that flame height increase is due to the increase in co-flowing. Increasing either the aspect ratio or the areas of inlet enhances the co-flowing as well as the flame height. Flame height has been theoretically derived for fires in the shaft. It is a function of the dimensionless heat release rate which is affected by the aspect ratio, areas of inlet, burner diameter, ratio of the areas of the inlet to the areas of the outlet and heat release rate of fire source. Moreover, empirical correlations have been correlated as a function of the dimensionless location for gas temperature rises in the shaft and heat fluxes on the wall. Negligible re-radiation among the symmetry walls is the main reason for high flame spread rates.