Experimental and Three-Dimensional Numerical Investigations of Dehydration and Pyrolysis in Wood under Elevated and High Temperatures

Abstract

Thermal responses of wood significantly depend on the dehydration and pyrolysis processes. However, the dehydration and pyrolysis of wood are not well understood. In this study, the thermal model of wood, considering the temperature-dependent thermo-physical parameters, was presented. Differential scanning calorimetry (DSC) experiments were conducted on the Douglas fir wood with different moisture contents to validate the apparent specific heat capacity submodel. Subsequently, the thermal model was, respectively, implemented in the finite element software Abaqus 6.14 and finite volume software OpenFOAM 5.0 to simulate the three-dimensional temperature profiles within the wood. Dehydration experiment was conducted on the Douglas fir wood to verify the thermal model from room temperature to 200 °C. The thermal model was further validated by the full-scale fire experiment of the cross-laminated timber panel made of Spruce wood. It was found that both latent heat and pyrolysis heat have significant influence on the apparent specific heat capacity which further affected the thermal responses of wood. Moreover, the temperature is more sensitive to the latent heat than to the pyrolysis heat. The gas velocity is rather low in the dehydration and pyrolysis stages due to the low gas pressure. As a result, the gas convection seems to have very limited influence on the temperature progressions.