DISTRIBUTION OF SMOKE BACKFLOW TEMPERATURE UNDER CEILING IN LONGITUDINALLY-VENTILATED TUNNEL FIRES

Both experimental and theoretical analysis of the distribution of smoke backflow temperature and the smoke temperature above the fire source are presented. The smoke temperature rise above the fire source under the ceiling linearly increases with the dimensionless heat release rate, and linearly decreases with the square root of a Froude Number. The ratio of smoke backflow temperature rise to smoke temperature above the fire source under tunnel ceiling varies exponentially with the distance from fire source. The exponential function is related with the backlayering length which is characterized as a Richardson Number in the formula. And the temperature of smoke backflow under tunnel ceiling can be predicted using the proposed formula, which is useful to evaluate the environment in tunnel tires using the longitudinal ventilation system and to help persons evacuate more safely.