Study of heat and moisture migration properties in porous building materials

Based on the non-equilibrium thermodynamic theory, the thermal driving forces and the fluxes in heat and moisture migration process for unsaturated porous building materials are analyzed. The mechanisms of heat and moisture migration in unsaturated porous building materials are discussed and the phenomenological equations to describe the immigrating process in unsaturated porous building materials are established. By means of the diffusion law and the equation of state for ideal gas, the expressions of coefficients in the phenomenological equations are deduced. The effects of temperature, water content or partial vapour pressure on the phenomenological coefficients are also discussed.