Drying Model and Moisture Diffusion Coefficient

摘要

Varied values of moisture diffusivity estimated using Crank's equation with different initial moisture content, equilibrium moisture content and sample thickness are often reported. However, a theoretical explanation to this phenomenon is not available to date. To explore the possible reason of this phenomenon, a Fick's second law diffusion equation for drying samples assumed uniform initial moisture distribution and negligible external resistance is solved numerically and the solutions as drying data is used to estimate the moisture diffusion coefficient of the sample through the equation reported by Crank. The result shows the Crank's equation used to estimate moisture diffusion coefficient could not be theoretical solution of the Fick's second law diffusion equation and the estimated value of moisture diffusion changing with initial moisture content, equilibrium moisture content and sample thickness perhaps caused by the Crank's equation itself.