Abstract
A theoretical approach of a macroscopic model for describing the water transport in unsaturated porous media leads to develop a phenomenological relation of non-equilibrium phase change. The thermodynamic response to an imposed liquid/vapour non-equilibrium is modelled close and far from equilibrium conditions. Various phenomena of liquid/gas phase change are investigated, such as evaporation, condensation of water and dissolution of CO2. Whatever the mechanism involved in the phase change, large times are observed for the return to equilibrium. This work focuses on the influence of texture, total gas pressure and temperature on the phase change rate. It shows that the kinetics of this phenomenon highly depends on the water thermodynamic state in soil, and that the hygroscopic property of material plays a major role. Some phenomenological interpretations of these results are proposed based on a microscopic description of the return to equilibrium.