考虑表观热工参数的木材热传导模型

To study the thermal responses of wood exposed to fire (high temperature), the wood was considered as the mix of materials under three states: before moisture evaporation, after evaporation but before thermal decomposition and after decomposition. The thermal gravimetric analysis (TGA) of Paulownia wood was conducted at 5, 10 and 20 K/min. The apparent kinetic parameters were determined by Ozawa method using TGA data. The apparent density and thermal conductivity were obtained from parallel and series models,respectively. The apparent specific heat capacity formula was proposed by considering latent and decomposition heat, which can be directly determined by differential scanning calorimetry (DSC) experiment. The one-dimensional nonlinear heat transfer model with apparent thermo-physical properties was developed and solved by one-dimensional implicit deference method. The thermal responses, such as temperature, degree of evaporation, degree of decomposition, apparent density, specific heat capacity and thermal conductivity etc. were obtained. The one-sided heating experiment of Paulownia wood was carried out to measure the temperature field. The results show that all the kinetic-based Arrhenius equations can well describe the moisture evaporation and thermal decomposition of the wood. Apparent specific heat capacity increases during the process of moisture evaporation and thermal decomposition.Good agreements are found between the analytical and experimental results. The proposed model can be used to predict the thermal responses of timber structures subjected to fire and high temperatures.