Theoretical and experimental study on longitudinal smoke temperature distribution in tunnel fires

Abstract

In order to study the hazard of the hot smoke which is toxic and in high temperature, a new heat balance equation is established to study the heat and mass transfer during smoke propagation process. The heat balance equation can be converted into an inhomogeneous linear differential equation of first order in the end, where the thermal radiation, air entrainment and heat convection are considered. The solution to this differential equation is proposed and the parameters are discussed. Furthermore, the factors that influence the smoke temperature distribution are discussed according to the equation we established. Additionally, in order to examine the solution of smoke temperature distribution in longitudinal direction, a set of small scale experiments are carried out where the variables are the ventilation velocity and heat release rate. Otherwise, a comparison with other tests' data both from small scale and real tunnels is conducted. Results show that the smoke temperature distribution correlates in good agreement with the solution we assumed both in our experiments and other tests, confirming that the theoretical analysis and the application of this formula in determining the smoke temperature distribution in tunnel fires in longitudinal direction and assessing the hazard the hot smoke. The investigation presented here considers only the cases when the ratio of the length to the width of the tunnel is large so that the smoke movement can be considered as One-dimensional Horizontal Spread.