Dependence of the water vapor diffusion coefficient of aspen (Populus spec.) on moisture content

The dependence of the diffusion coefficient of water in aspen (Populus sp.) on moisture content over the range of 0 to 18 percent moisture content at 43 °C was determined. The method requires a series of adsorption experiments and application of a numerical method for solving the diffusion equation with a moisture-content-dependent diffusion coefficient. The diffusion coefficient was found to increase exponentially with moisture content. The numerical method includes variable boundary conditions, as defined by the surface emission coefficient, so that the effect of surface equilibrium moisture content can be examined. The experimental moisture content-time curves can be predicted by the numerical method and showed an average deviation of 0.2 percent moisture content with the largest deviation being 0.7 percent moisture content. Practical implications and uses of the information derived from the numerical method are also discussed