Analytical theory on coupled heat and water transfer through porous materials.

New thermodynamic energy "water potential" based on the chemical potential of a component of mixture gases is defined as the driving force of gaseous phase water flux. Adhesive power, which is a kind of stress call "capillary attraction" and a part of the water potential, is proved as the driving force of liquid phase water flux. Then numerical model of coupled heat and water transfer using the water potential is introduced and influences of stress such as gravity and stationary pressure on water flux are clarified from the viewpoint of thermodynamics. The way to estimate diffusivities of gaseous and liquid phase water through porous materials is also proposed. Furthermore accuracy of the numerical model is shown through a comparison between calculation and experiment on behaviour of water content in a porous material.