DISCONTINUOUS VACUUM DRYING OF OAK WOOD: MODELLING AND EXPERIMENTAL INVESTIGATIONS

Abstract

Vacuum drying and especially discontinuous vacuum drying is a very attractive process for such a wood as oak, because of a reduced drying time and a high quality of the final product. In this paper, a model describing heat, mass and momentum transfer in a capillary porous and hygroscopic medium under vacuum drying with no external heating agent (the material is pre-heated during a convective phase), is presented. The choice of the following three independent unknowns, moisture content, enthalpy and dry air density, leads to a fully well described problem where the effect of gaseous pressure inside the material is taken into account. A new formulation of the boundary conditions and its numerical resolution are validated by experimental results.