Fire Safety Science Digital Archive

In this study, a new zone modeling approach, called a Multi Layer Zone (MLZ) model was extended to adapt to predict smoke movement in a tunnel fire, including vertical distributions of temperature and chemical species concentrations. In this model the volume of a tunnel is divided into multiple of areas and each of then is further divided into multiple horizontal layers as the control volumes. The physical properties, such as temperature and species concentrations, in each layer of each area are assumed to be uniform. The boundary walls are also divided into segments at uniform temperature in accordance with the layer division. Radiation heat transfer between the layers and between the layers and the wall segments is calculated, as well as the convective heat transfer between the layers and the wall segments. Air entrainment into the fire plume and the flame, considering the effect of the horizontal flow around it, is calculated with a simple set of equations. This model still retains the advantage of zone models in terms of computational load, hence it is expected to be useful for practical applications associated with fire safety design of tunnels. For calibration and verification of the model, comparisons of the predictions by the present model are presented against measurements in two cases of experiments using a tunnel facility (Length 28m) and predictions by FDS for the same test conditions. The predicted temperatures and velocities generally show satisfactory agreement with the experimental data.