Critical evaluation of an integral model for the pyrolysis of charring materials

When field models are used to predict fires and flame spread, a solid model is required to calculate the amount of released pyrolysis gases. Here, the integral model for the pyrolysis of charring materials of Moghtaderi et al., extended with a cooling stage is considered. When an incident heat flux measured during a flame spread experiment, is imposed to the solid, the cooling stage is shown to be indispensable to solve the pyrolysis process. Next, the integral model is compared with a moving grid model. The latter uses the same physical model but does not make any assumption on the temperature profile and thus gives the true solution of the physical model. Comparison of both models reveals that the integral model has problems with suddenly varying boundary conditions and produces erroneous results for parameter studies on thickness and rear boundary condition variations. However, when compared to inert pyrolysis experiments, the integral and the moving grid model are comparable in quality. An automatic optimisation technique is described to obtain material fire properties.