| This study evaluates the influence of extractives on moisture diffusivity, and thereby the drying behavior of wood. Extractives are minor chemical components of wood, and their effect on moisture diffusion is sensitive to experimental and calculation errors. A series of studies designed to accurately determine the proper solutions of a diffusion model was done; then studies to determine the effect of extractives in a wood drying system were undertaken. The drying curves derived from the optimum diffusion coefficients gave better prediction of experimental drying data than those derived from traditional approximate methods; therefore, optimum methods were applied in the study on natural extractives as well as artificial extractives. Depending on treatment times, both hot-water soaking and steaming treatments increased the diffusion coefficients. This phenomenon suggested that both the amount of extractives and their locations in wood influenced the moisture movement during drying. When green wood samples were impregnated with polyethylene glycol or tannin, the drying rate decreased significantly. The contributing effect of extractives during drying is due to blockage of the moisture passages in the void spaces. |
