A general analysis of moisture migration caused by temperature differences in an unsaturated porous medium

Abstract An analysis was performed which describes the moisture migration in a slab of an unsaturated porous material for the condition that the temperature of one surface is suddenly increased to a higher value whereas the temperature of the other surface is maintained constant. The two surfaces are assumed impermeable to mass flow. The thermodynamic and transport properties occurring in the equations describing the temperature and moisture transport are assumed constant. In this way, very general relations are obtained for the moisture field as it changes in time. Before dry-out, a dimensionless parameter describing the moisture field is a function of equivalent Luikov and Fourier numbers only. The dependence on the Luikov number becomes noticeable solely for the early periods and for small values of the Luikov number. After the onset of dry-out, the moisture ratio depends in addition on the thermal mass diffusion coefficient. The results of the analysis presented in the Figs 1–7, should describe the actual moisture migration with good accuracy where the variation of the properties is small in the range of the independent variables occurring in a specific situation and they should be useful as a first approximation for other situations as well.