MODELING CONVENTIONAL TWO-DIMENSIONAL DRYING OF RADIATA PINE BASED ON TRANSVERSAL EFFECTIVE DIFFUSION COEFFICIENT

摘要

We modeled conventional two-dimensional drying of radiata pine (Pinus radiatd) wood using the concept of effective diffusion extended to overall drying process. Effective diffusion coefficients were determined experimentally on the transversal plane and depended exponentially on the moisture content. These coefficients were characterized by two parameters determined through optimization within the context of an inverse problem. Spatially variable convection coefficients were determined in the same manner. Experiments using constant drying 44/36 (°C/°C) were carried out in order to determine transitory spatial distributions of moisture and drying curves, which were then used to determine and validate the model parameters. The mathematical model consisted of a partial, non-lineal, differential equation of the second order, was characterized by coefficients that varied exponentially with moisture content, integrated numerically through the finite volume method. Results of two-dimensional simulations for isothermal drying of radiata pine timber, correlated with experimental data, are shown: a) Transitory distribution of moisture gradients, b) drying curves and c) parameter of mathematical model (effective diffusion and mass convection coefficients).