Evaluation of material properties determining the moisture transfer

KEZ, TU Liberec, Studentská 2,461, 17 Liberec 1, Czech Republic

Abstract

Due to solution the problems of moisture transfer is necessary to deal with two mechanisms of transfer: the molecular mass transfer and mass transfer by convection. Transfer driving force is the difference of concentrations of moisture, respectively the difference of partial vapour pressure. For molecular transfer is deciding value the coefficient of diffusivity, i.e. the property of the material. For mass transfer by convection is deciding the convection mass transfer coefficient, which depends on many parameters, but for one particular arrangement of the experiment will be influenced primarily velocity of the flow. Experimentally detectable is the overall moisture transfer caused by both mechanisms, i.e. the overall moisture transfer coefficient. Our goal was to attempt to evaluate the value of coefficient of diffusivity of some materials from the set of measured date. The date was obtained in different modes on different samples of materials. The next goal was to evaluate the dependence of the convection mass transfer coefficient on the speed of flow for the experiment alignment.