The effect of thermal radiation on the dynamics of flashover in a compartment fire

Flashover is a phenomenon describing a room fire changed from the growth stage to the development stage. There is a rapid increase in size and intensity. The radiant heat flux back to the fuel surface and the floor of the room is known to be one of the key parameters leading to flashover. Indeed, a heat flux (largely due to radiation) of 20 kW/m2to the room floor is often taken to be the condition of flashover. To understand the importance of radiation, a zone model is developed to simulate the transient fire growth in a compartment. Heat and mass transfer correlations available in the literature are used to simulate the non-radiative effect. A three-dimensional non-gray soot radiation model is used to simulate the radiative exchange between the fuel surface, the hot gas/particulate layer and the surrounding wall. Results show that the hot layer temperature alone may not be an effective indicator for flashover. Other parameters such as particulate volume fraction in the hot layer, venting area and heat transfer to the surrounding wall are also important in determining the occurrence of flashover.