Decay of buoyant smoke layer temperature along the longitudinal direction in tunnel fires

A simple model was reported to predict the longitudinal distribution of temperature rise for the smoke layer along a tunnel. The longitudinal decay of excess smoke layer temperature in dimensionless form was studied by including convective and radiative heat transfer to the boundary. An expression was derived to relate to the dimensions of the cross-section of the tunnel, the depth and the velocity of the smoke layer to the temperature. A series of full-scale tests was conducted in three vehicular tunnels to verify the model. There, temperature field and smoke layer traveling velocity were measured downstream the fire source. The decay factors for longitudinal smoke layer excess temperature distributions were predicted from the model based on the smoke layer velocities and the dimensions of the vehicular tunnel. Results are then compared with those deduced directly from the measured temperature data. Good agreement was achieved.