Quick assessment of the hot gas layer temperature and potential fire spread between combustible items in a confined space

The effective management of fire safety requires understanding in advance the resulting conditions of a fire in a confined space. This task is usually achieved by considering several quantitative indicators, establishing threshold limits for each one corresponding to specific hazardous situations and then calculating if such threshold limits are reached. In such a way, it is possible to assess whether or not management conditions are satisfactory. In this work, two main indicators are considered: the hot gas layer temperature and the thermal radiation from the fire. Indeed, the hot gas layer temperature is related with the occurrence of hazardous conditions for people, the spread of the fire to combustible items far from the fire source and hence with the occurrence of flashover and critical conditions for stability of structural elements. On the other hand, thermal radiation from a fire source can be considered as the primary cause of fire spread in pre-flashover conditions, when there is not direct flame impingement and outside the plume, where convective heat transfer is not a principal factor in fire heat transfer. Therefore, in order to estimate if a remote object from the fire will ignite; one must be able to quantify the radiative heat flux received by the target. Both the hot gas layer temperature and the thermal radiation to a target can be assessed by using either analytical equations or fire simulation models. Due to their simplicity and quick use, analytical equations could be suitable for preliminary, rapid hazard assessment. In this work, a comparison between two simple analytical equations and the results obtained using CFD simulations (FDS) for a set of scenarios are presented with the aim of assessing capabilities of the analytical models in foreseen hot gas layer temperature and the thermal radiation from the fire.