Spectral aspects of bench-scale flammability testing: Application to hardwood pyrolysis

Abstract

The anaerobic pyrolysis of wood material used to palletize commodities is studied in a Fire Propagation Apparatus (FPA) for a range of heating conditions relevant to fires. The data collected, consisting of mass loss rate, cumulative mass loss, and surface temperature, are used to determine model-specific material properties using inverse modeling and optimization methodologies previously developed in our laboratory. However, in this study, considerable effort is placed on determining the radiation environment that characterizes the FPA tests as well as how the radiation interacts with the samples. This is done on the basis of the recognition that boundary conditions have a pronounced effect on the output of a given pyrolysis model and, thus, the optimization results. The spectral radiance from the FPA heaters as well as the absorptivity/emissivity of the material surface are measured herein. The spectral features of the surface indicate that markedly different effective emissivities and absorptivities can be exhibited by the material depending on the spectral distribution of incident radiation. These effects are included in the pyrolysis model used to extract model-specific material properties so that the optimization process can, in a sense, be decoupled from boundary conditions. Therefore, it is expected that the approach described in this study can ensure that the derived model-specific properties can be applied to practical scenarios that are characterized by radiation environments that differ from those in bench-scale test apparatuses such as the FPA.