Radiation Heat Transfer and Reaction Chemistry Models for Risk Assessment Compatible Fire Simulations

Abstract

Risk assessment studies for hazardous material packages require fire response prediction tools that are both accurate and rapid. This article describes the theoretically based, semiempirical reaction chemistry and radiation heat transfer models for large, optically dense pool fires incorporated in the ISIS-3D CFD software. The chemistry model employs four separate reactions (two produce radiating soot). The heat transfer model divides the computational domain into the diffusely radiative fire and its nonparticipating environment. ISIS-3D simulations are performed on a 6-m square JP8 pool fire experiment in which the soot temperature and volume fraction are measured. The reaction rate and soot formation parameters of the chemistry model are determined based on a comparison of the simulation with the measured data. Simulations are then performed on an experiment that measures the temperature of a pipe calorimeter suspended over the leeside of a 19-m-diameter JP8 fuel pool fire with a 9.5 m/s crosswind. The soot volume fraction that the heat transfer model uses to define the edge of the diffusely radiating fire is determined based on a comparison with the measured average temperature of the calorimeter. That simulation accurately predicts the calorimeter spatial temperature variation without further adjustment. ISIS-3D is not fully predictive, should not be used far outside the range of conditions in which its parameters are determined (JP8 pool fires larger than 2 m), and is not intended to replace the fundamental fire physics software. However, it demonstrates highly accurate results with rapid turnaround times for a range of conditions that are relevant to large hazardous material transport packages in severe fire conditions.

Keywords

risk assessment radiation heat transfer combustion chemistry pool fire fire simulation

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