Analysis on coupled heat and water transfer through porous materials by thermodynamic energy

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 called “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 indicated from the viewpoint of thermodynamics. The way to estimate diffusivities of gaseous and liquid phase water through porous materials is also shown. Furthermore accuracy of the numerical model is clarified through a comparison between calculation and experiment on fluctuation of water content in a porous material.