A numerical methodology to predict the gas/solid interaction in fire resistance test

The present study investigates different simulation approaches to predict the temperature of fire exposed structures and building materials with the main emphasis on fire resistance tests. In many cases (e.g. steel structures) the consideration of the heat transfer between the gas phase combustion (fire) and the solid test specimen in the numerical model is sufficient. However, chemical reactions can occur in the solid test specimen, leading to the release of volatile gaseous components into the gas phase. These components can affect the gas phase and heat transfer in a significant way by increasing (combustibles from wood parts) or decreasing (water vapour from gypsum) the gas temperature. To test the simulation models a fire resistance test of gypsum blocks was used and predicted temperatures were compared to measured data. It was found that the simulation approaches, neglecting the release of water vapour by the gypsum clearly over-predict the gas temperature as well as the temperature of the gypsum. Using the concept of the “Adiabatic Surface Temperature” the temperatures were 167 K (gas) and 19.8 K (gypsum) higher than observed in the experiment. A numerical model was also proposed, which considers the “two-way” coupling (heat transfer and release of water vapour). The prediction of the temperature was significantly improved and showed a deviation of 3.3 K for the gypsum. Thus, the release of volatile components is a crucial part in fire modelling and heat transfer.