Influence of model assumptions on charring polymer decomposition in the cone calorimeter

Abstract

This article addresses the one-dimensional modeling of a charring polymer decomposition in the cone calorimeter used to reproduce at bench scale the radiative heating from a fire. The rate-controlling phenomena are first discussed in a preliminary analysis of dimensionless numbers. Then, the role of three critical assumptions is highlighted by simulations: (1) transport of the gaseous products within the material or instantaneous release of gaseous products, (2) volume variation or constant volume, and (3) absorption of applied heat flux at the exposed face or through the thickness. Their influence in thermally thick regime is shown in particular on mass loss rate and time to extinction. Under the conditions tested, the influence of internal transport by convection on mass loss rate and time to extinction is minor. The assumption of constant volume appears to have a moderate influence on the mass loss rate and time to extinction. Variations of optical properties affect the numerical results by an increase of the maximum peak of mass loss rate and a decrease of time to extinction. Finally, the effects of applied heat flux and initial material thickness on the mass loss rate and time to extinction are important. With a higher heat flux or a smaller thickness, the decomposition is earlier, faster, and more intense.