Moist Air (Hygroscopic Porous Medium)
This subnode defines the properties for the transport of the moist air phase in a porous medium filled with two phases in equilibrium: liquid water and moist air. The moisture transport occurs through vapor diffusion and convection in moist air, and convection and capillary flow in the liquid phase.
Moist Air Properties
This section contains settings for the definition of convective and diffusive vapor transport in the moist air phase.
First, set the Diffusion Coefficient, D (SI unit: m2/s), for the binary diffusion of vapor in air in a free medium. The default value 2.6·105 m²/s is valid at T = 298 K and pA = 1 atm. You may set a temperature or pressure-dependent diffusion coefficient through the use of the variables mt.T and mt.pA.
Specify the Effective diffusivity model used to account for the porosity and the tortuosity of the porous medium in the diffusion coefficient, Deff (SI unit: m2/s). The available options are Millington and Quirk model (the default), Bruggeman model, Tortuosity model, and No correction.
For the Tortuosity model option, enter a value for the Tortuosity factor, τ (dimensionless). The default is 1.
Then, set the Moist air velocity field, ug, that should be interpreted as the Darcy velocity, that is, the volume flow rate per unit cross sectional area. For User defined enter values or expressions for the components based on space dimensions. Or select an existing velocity field in the component (for example, Velocity field (br) from a Brinkman Equations interface).
Location in User Interface
Context Menus
Ribbon
Physics Tab with Hygroscopic Porous Medium selected in the model tree: