Transient Simulation of Coupled Heat, Moisture and Air Distribution in Wood during Drying

An approach to the numerical simulation of wood drying based on the finite element method is presented. Wood, as a hygroscopic, strongly anisotropic porous material, must be dried before being used for a practical purpose. Wood drying leads to a combination of vapor, bound water, and free water movement. A numerical simulation of the drying process of wood involves three fundamental phenomena: heat transfer, movement of moisture, and mechanical deformation. Liquid flow due to capillarity, water vapor and air (diffusing and convection in bulk gas flow), and bound liquid diffusion are basic mechanisms of mass transfer in wood. The aim of the paper is to present a numerical model of coupled heat, moisture and air transfer in pores of wood subjected to high temperature drying conditions. Heat and moisture exchange take place between wood and drying medium, and coupled problems can be described from a macroscopic viewpoint of continuum mechanics. Benchmark tests of a 3-D model under Dirichlet and mixed type of boundary conditions are used to account for the coupling among temperature, moisture content and gas pressure.