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Transient multiphase model for the high-temperature thermal treatment of wood



The hygrothermal behavior of wood at high temperature is analyzed, taking into account all the phases present such as wood, liquid water in free and bound forms, and water vapor. The moisture transport phenomenon includes water vapor convection and diffusion along with capillary water convection in the pores of the particle as well as bound water diffusion in the solid wood. Local thermodynamic equilibrium is assumed, which is represented by a sorption isotherm that relates the moisture contents in the solid and gas phases. The equations of the model were solved numerically using the commercial software Femlab® for the temperature and the moisture content profiles. The mathematical model predictions were compared with the experimental data and a reasonably good agreement was obtained. A parametric study was also carried out to determine the effects of several parameters such as heating rate, initial moisture content, and the sample thickness on the temperature and moisture content distributions within the samples during heat treatment. © 2006 American Institute of Chemical Engineers AIChE J, 2006