Moisture Flux
Use this node to add moisture flux across exterior boundaries. A positive moisture flux adds moisture to the domain. Also the external moist air pressure is prescribed.
Moisture Flux
Select the Flux type from the list: General moisture flux (the default), Convective moisture flux, concentration difference, or Convective moisture flux, pressure difference.
General Moisture Flux
It adds g0 to the total flux across the selected boundaries. Enter a positive value for g0 to represent a moisture flux that enters the domain.
Convective Moisture Flux, Concentration Difference
Enter a value for the Moisture transfer coefficient hm together with the External temperature, Text, and the External relative humidity, ϕw,ext, to compute the flux across the selected boundaries. For User defined, enter values or expressions. Else, select an Ambient relative humidity and an Ambient temperature defined in an Ambient Properties node under Definitions. The convective moisture flux is defined by
Convective Moisture Flux, Pressure Difference
Enter a value for the Moisture transfer coefficient βp. In addition, two options are available to specify the external conditions:
If Relative humidity is selected (the default), set the External relative humidity, ϕw,ext, and the External temperature, Text (used for the computation of the vapor saturation pressure). For User defined, enter values or expressions. Else, select an Ambient relative humidity and an Ambient temperature defined in an Ambient Properties node under Definitions. Convective moisture flux is defined by
If Partial vapor pressure is selected, enter an External partial vapor pressure, pv,ext. Convective moisture flux is defined by
Constraint Settings
To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog.
In the COMSOL Multiphysics Reference Manual:
Location in User Interface
Context Menus
Ribbon
Physics tab with Moisture Transport in Solids selected: