Determination of the material property variations across the growth ring of softwood for use in a heterogeneous drying model part 1. Capillary pressure, tracheid model and absolute permeability

In this work, the extensive knowledge of wood gained at thr Ecole Nationale du Genie Rural des Eaux et Forets by using a combination of microscopic ob servation and experimental work is being used to postulate material propert y correlations for a macroscopic heterogeneous "Cerne" growth ring model of softwood. Mathematical tools such as image analysis and homogenisation are used to develop models that capture the effect of the density variation wi thin the wood sample of important macroscopic physical parameters. This fir st part is devoted to mass transfer in wood due to Darcy's law. Capillary p ressure correlations as a function of local density are deduced from image analysis. Thereafter a tracheid model is proposed for softwood. Its shape e volves from earlywood to latewood according to anatomical observations. Liq uid and gaseous permeability values are calculated from this model accordin g to Poiseuille's flow within cells and assuming a linear flow-pressure los s relationship through the pits.