Credibility assessment of a new heat, air, and moisture transfer model with hygric non-equilibrium for drying of porous building materials

The paper presents a new model for the drying of porous building materials. The mixture approach was used to model transport phenomena in a porous medium. Therefore, the effective properties of the medium were used instead of modeling the exact microstructure. Three phases were considered, i.e., solid material, liquid moisture, and humid air (i.e., vapor and dry air mixture). The model allowed for capillary water and diffusive vapor transfer and air exchange. Thermal equilibrium was assumed between all phases (i.e., the same temperature of all components). However, the hygric non-equilibrium between the water and vapor was modeled. The model was implemented in the commercial software ANSYS Fluent by using advanced customization user interfaces, i.e., User-Defined Function (UDF), Scalar (UDS), and Memory (UDM), which allowed to extend the software capabilities to moisture transfer phenomena. The model was validated against the experiment. The dedicated test rig was explicitly designed to compare simulations with measurements. The drying tests were performed under forced convection. The validation shows a good agreement between the model predictions and the measurements, especially during the first drying phase. The sensitivity analyses showed that the mass transfer coefficient in the pores and the liquid transport parameters affect the results and the accuracy of the model.