Fuel Mass-Loss Rate Determination in a Confined and Mechanically Ventilated Compartment Fire Using a Global Approach

Abstract

Fire development is generally characterized in terms of evolution of heat release with time, and its determination thus represents an essential aspect of a fire hazard analysis. Since it is not a fundamental property of a fuel, heat release cannot be calculated from the basic material properties, and one generally resorts to experiments to determine it. In this article, we present a theoretical formulation that allows the determination of the burning rate of fuels for pool fires in a closed compartment. It is based on an energy balance at the pool fire surface and includes radiative and convective heat components from the flame to the pool surface by relating them to the ambient oxygen mass fraction at the flame base. Fuel response to vitiated air as well as burning enhancement due to hot gases and confinement are taken into account. The formulation was first compared with the empirical correlation determined by Peatross and Beyler before being implemented in a computational fluid dynamics (CFD) code and validated against two experiments involving a hydrogenated tetra-propylene pool fire test enclosed in a confined and mechanically ventilated compartment. These experiments were conducted in conditions for which external heat fluxes were either negligible or significant. It is shown that this approach is able to correctly predict the fuel mass loss rate and provides a reasonable assessment of the heat flux from the flame to the pool surface.