The maximum ceiling gas temperature in a large tunnel fire

Effects of different ventilation systems, ventilation velocities, heat release rates, tunnel geometries and fire sources on the maximum excess gas temperature beneath the ceiling in large tunnel fires are analyzed. Data from numerous model scale tests and most of the large scale tunnel fire tests that have been performed worldwide are used and analyzed. Correlations for the maximum ceiling excess gas temperature in the vicinity of the fire source are proposed for low and high ventilation flows. The temperature data indicate two regions, depending on the dimensionless ventilation velocity. Each can be divided into two sub-regions. The first sub-region exhibits linear increase which transits into a constant period, depending on the fire size, ventilation and the effective tunnel height. The maximum excess gas temperature is found to be 1350 °C.

► Maximum excess gas temperature beneath ceiling in large tunnel fires is analyzed.
► Model scale and large scale tunnel fire tests performed worldwide are used in analysis.
► A robust equation is proposed.