The impact of fire source location on hot gas layer temperature in multi-compartment pre-flashover fires: Analysis and semi-empirical model development

A numerical study of a two-room structure (multi-compartment) subjected to fire in the inner room was carried out, employing the CFD (Computational Fluid Dynamics) software called FDS (Fire Dynamics Simulator), to (i) analyze the influence of the fire source position on the hot gas layer temperature, $T_u$, and its behavior in a multi-compartment fire, and (ii) develop a semi-empirical engineering calculation model to predict $T_u$ in the adjacent room to a pre-flashover well-ventilated fire room, taking into account the fire source position. The results showed that when the fire origin occurs close to walls or elevated above the floor level, a reduced air entrainment is observed in the fire plume and flame, causing an increase in the $T_u$ and a reduction of the smoke production in the fire room. This reduction in the smoke production led to a lower increase in the $T_u$ of the adjacent room in relation to the case when the fire source was at the center of the fire room. It was also observed that the $T_u$ in both rooms was inversely proportional to the ventilation factor ($A.H^{0.5}$), with a significant increase observed as the ventilation factor decreases, depending on the fire source position. Furthermore, a semi-empirical engineering calculation model was developed to predict the $T_u$ in the adjacent room, considering different fire source locations at ground level and elevated. The model was validated against experimental data from the literature, showing a good agreement (deviation of ≈20 %), thus demonstrating its applicability to other cases.