Behavior of Tunisian Aleppo Pine (Pinus halepensis Mill) wood during convective drying: Identification of the diffusion coefficient taking into account shrinkage velocity

This study proposed to identify the water diffusion coefficient in tunisian aleppo pine (pinus halepensis mill.) wood through convective drying,and to predict the activation energy. a diffusive model was developed based on numerical resolution of both the solid phase conservation equation and the water transfer equation (diffusion/convection). it also took into consideration the contraction speed of the solid matrix due to hydrous shrinkage. the model was developed by minimizing the difference between the experimental and the estimated moisture content. the desorption isotherm was measured by the experiment and then modeled by dent's equation. it provided precise information about the hygroscopic wood equilibrium. dent's equation was used to represent the relationship between water activity and the equilibrium moisture content. the volumetric shrinkage curve provided information about the different types of water in the wood as well as the water content value at the fiber saturation point. hydrous diffusivity values varied between 1,7 1011 m2 s-1 and 3,4 10-11 m2 s-1 as a function of temperature and water content. the activation energy was 137,031 (kj/mol). at a critical point,there was an abrupt change in the hydrous diffusivity slope around the water content at the fiber saturation point,which could slow down the process of numerical resolution in the hygroscopic field.