Mathematical Modeling of Wood Drying from Heat and Mass Transfer Fundamentals

Abstract

A mathematical model is developed to simulate the drying of wood. In this approach, mathematical formulations for the transport rates are incorporated into one-dimensional partial differential material and energy balance equations which are coupled with algebraic relations for local phase equilibria. Spatial derivatives are approximated in finite difference form with variable spacing between mesh points in order to maintain accuracy. The resulting ordinary differential equations are solved numerically using a special solver for systems of stiff equations, with the solution constrained locally to satisfy the phase equilibria relations. The model simulation provides spatial distributions of each moisture phase (vapor, liquid, and bound) and of temperature and pressure as functions of time. Because this model is based on fundamental transport theory, it provides a tool to investigate the impacts on drying behavior both of process variables and of the material properties of wood.