DETERMINATION OF MOISTURE DIFFUSIVITY IN POROUS-MEDIA USING MOISTURE CONCENTRATION PROFILES

A procedure is presented to determine the moisture diffusivity for dry ing from measured moisture concentration profiles. From error analysis iris shown that the applied space grid for scanning and the one-dimen sional resolution of the NMR (nuclear magnetic resonance) method used for the measurements had a minor influence on the accuracy of the dete rmination of the moisture diffusivity. The inaccuracy was dominated by experimental noise and inhomogeneities in the porosity of the materia ls 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 dry ing front to approximate the moisture diffusivity.