Temperature stratification in tunnels

Abstract

An investigation of previously established correlations between gas temperature distribution and smoke stratification in mines has been carried out for tunnel applications. The investigated correlations are based on excess gas temperature ratios and Froude number scaling. This paper describes a comparison between two large scale tests carried out in a road tunnel and two well defined model scale tests. In each of the tests, a longitudinal flow was maintained. The temperature data obtained at different locations and different heights have been used for the comparison. A good correspondence between the experimental data and the correlations has been found when the gas temperature data were used. However, the correspondence between the previously established correlation of gas temperature stratification and Froude number, was not reliable. It is postulated that the main reason for this may be the way the experiments were carried out. New correlations between the temperature stratification and the Froude number are also explored.

Experimental study on the effect of lateral concentrated smoke extraction on smoke stratification in the longitudinal ventilated tunnel

“…Some previous works 8‐14 investigated the characteristics of smoke thermal stratification in tunnel fires, which are related to the safe evacuation of people in the tunnel. Newman 8 carried out experiments in the mine and classified the longitudinal smoke layer (layered form) into three different areas according to the Froude (Fr) number.…”

“…Yang et al 9 studied the smoke stratification behavior in a horizontal channel induced by ceiling extraction system; the three different regimes were found for smoke stratification behavior. Nyman and Ingason 10 studied and estimated the temperature stratification in a tunnel fire based on an average temperature and an average velocity in tunnel fires. Du et al 12 conducted many experiments to study the mixing and stratification of buoyancy‐driven flows in a narrow‐inclined tank, and the effect of reduced gravity along the longitudinal direction was also analyzed.…”

Fire Model Test on Temperature Field in the Rescue Station of an Extralong Railway Tunnel

“…Reduced-scale model experiment has been another popular method in the study of tunnel fires owing to its convenience, ease of control, low cost, and other advantages. Nyman and Ingason [23] performed two reduced-scale tests to explore new correlations between temperature stratification and the Froude number in a tunnel. Fumiaki et al [24] used a 1/12 scale model tunnel to obtain the temperature characteristics of natural ventilation during smoke extraction in a road tunnel with roof openings.…”

Effects of fire location on the capacity of smoke exhaust from natural ventilation shafts in urban tunnels

“…Although mechanical ventilation is less affected by the outside environment, its system layout is complicated, the economic investment is large, and the maintenance is difficult. In addition, the mechanical ventilation is easy to destroy the smoke layer stratification under the tunnel ceiling, which is very unfavorable to the evacuation of stranded persons in the early stage of tunnel fire. Compared with mechanical ventilation, natural ventilation not only causes less disturbance to the smoke layer stratification, but also is a simple and economical mode.…”

“…[23][24][25][26][27][28] Although mechanical ventilation is less affected by the outside environment, its system layout is complicated, the economic investment is large, and the maintenance is difficult. In addition, the mechanical ventilation is easy to destroy the smoke layer stratification [29][30][31][32] under the tunnel ceiling, which is very unfavorable to the evacuation of stranded persons in the early stage of tunnel fire.…”