Determination of moisture diffusivity in porous media using moisture concentration profiles

A procedure is presented to determine the moisture diffusivity for drying from measured moisture concentration profiles. From error analysis iris shown that the applied space grid for scanning and the one-dimensional resolution of the NMR (nuclear magnetic resonance) method used for the measurements had a minor influence on the accuracy of the determination of the moisture diffusivity. The inaccuracy was dominated by experimental noise and inhomogeneities in the porosity of the materials under investigation. A receding drying front method is presented to determine the moisture diffusivity at low moisture contents: here the moisture transport is dominated by vapour transport, which limits the overall drying rate. The method uses the velocity of the receding drying front to approximate the moisture diffusivity.