Transient numerical simulations of a fire in an enclosure (1/3 the ISO room size) were performed to develop and to validate a transient semi-analytical treatment of the heat transfer in the walls. The setup closely followed one of the experiments performed by Tofilo et al [1]. As in the experiments, methanol was used as a fuel. The fuel source at the back left corner of the enclosure was represented by a time dependent mass inflow.
To model the flow turbulent behaviour, the Shear-Stress Transport (SST) model was selected. Thermal radiation was modelled with the Discrete Transfer model. In our case 24 rays were used in radial and in azimuthal direction. A multigrey gas model was used to take into account the temperature and pressure dependencies of radiative absorption and emission from gases. For combustion modelling, the Eddy-Dissipation combustion model was selected. An additional effort was invested to develop a semi-analytical model of the wall thermal response. A detail description of the modelling approach can be found in [2].

Temperatures and heat fluxes were recorded at the multiple locations on the wall opposite the fire. Matching these values with the experimental data over the whole period of the experiment was the main challenge of the modelling validation exercise.

The comparison shows a good agreement between both sets of results over the whole period of fire development. The CFD model predicts well thermal conditions in the upper (hot) and in the lower (cold) layer. Nevertheless, it is important to mention that the thickness of the hot layer is slightly underpredicted.