Thermal response of balsa wood for fire environments

This study concerns a joint experimental and numerical modeling effort to understand and predict the response of balsa for fire environments. The first part of this study presents thermogravimetric measurements and micrographs of balsa wood undergoing decomposition. A thermogravimetric analysis is used to determine the Arrhenius kinetic rates for one-step global reactions of dehydration and decomposition used in the modeling. Micrographs reveal the structural changes to balsa wood during decomposition characterized by void area and estimated diameters. Also grain diameter histograms of void size are estimated using the micrographs that are then used for estimates of gas permeability. The modeling of the balsa wood is based on a homogenization approach for which virgin wood, char, water, and gas are individually tracked. Gaseous species concentrations are tracked within the structure thereby allowing for the inclusion of homogenous reactions within the gas phase. Equations are derived that employ Darcy's and Fick's laws for the transport of individual gas species within the structure. A sensitivity study is conducted of heat and mass transfer in 1D media. Cases are conducted with varying initial bound water content and imposed surface heat flux.