Containers of high-energy materials exposed to an enveloping fire may eventually undergo a thermally induced reaction that can lead to explosions, and result in losses to human life and property. The time to explosion is greatly influenced by the amount and rate of energy that reaches the explosive. The thermal boundaries at the fire/container and container/explosive interfaces introduce major uncertainties in the prediction of this time. This work focuses on the fire/container interface and the critical issues associated with the specification of the thermal boundary at this interface, which include the deposition mechanism of soot on the container, and the chemical and physical properties of the soot deposit and their subsequent effect on heat transfer to the container.

A laboratory-scale device (metallic plates attached to a water-cooled sampling probe) has been designed for estimation of soot deposition rates and deposit thickness in controlled sooting flames (ethylene-air premixed flames). The metallic plates facilitate evaluation of the deposition rate and deposit characteristics such as bulk density, PAH content, deposit morphology, and thermal & optical properties, under both water-cooled and uncooled conditions. For both types of conditions, deposition rates and deposit thickness increase with height above the burner and with sampling time. Thermophoresis is involved in the soot deposition process and enhances higher deposition rates for the water-cooled experiments. It is also found that the temperature at which the deposits are collected significantly affects the chemical composition of the collected soot samples; in this case, the water-cooled tests produce the largest amount of aromatic and PAH species content. Finally, SEM analysis for the water-cooled samples has indicated different morphologies for the soot samples at different axial locations.