Modeling unsteady heat and mass transfer with prediction of mechanical stresses in wood drying

Abstract

This work presents a predictive transient two-dimensional model describing the evolution of heat, mass and mechanical stresses during wood dehydration inside an experimental drying chamber. The history of the distributions of moisture content and temperature and the effects produced by its gradients on the stresses were simultaneously modeled. The non-linear coupled differential equations of heat, mass and stresses were integrated by the Control Volume Finite Element method using triangular elements with linear interpolation functions for the dependent variables. Variation of the physical and mechanical properties with the moisture content and temperature in the wet wood were included in the analysis. Experimental results of Pinus radiata being dried inside a conditioned chamber at constant air velocity equal to 1.6 m/s, 44 °C dry-bulb and 36 °C wet-bulb temperatures were used for validation purposes. The mathematical model allows an accurate prediction of the relevant industrial information, such as: drying curves, evolution of temperature distribution, history of moisture content distribution and mass/thermal stresses.