Select an option in the Coupling condition list to couple the macroscale heat equation solved in the fluid phase and the microscale equation solved in the pellets to account for radial thermal conduction.
With the Continuous temperature option (default), the temperature at the outer surface of the pellets and the fluid temperature are enforced to be equal, and the resulting heat flux is applied in the fluid and pellets equations. See the
Constraint Settings section below for advanced settings relative to the continuity constraint.
With the Convective heat flux option, a heat transfer term, proportional to the temperature difference between the fluid phase and the outer surface of the pellets, is applied in the equations of both phases. The heat transfer term is applied in an averaged way in the fluid equation, by multiplying it by the
Specific surface area,
Sb. Either use the
Automatic expression for
Sb, defined as a function of the average pellet diameter
dpe, or set a
User defined value or expression. Either use the
Automatic option for the
Interstitial heat transfer coefficient,
hpe,f, defined as a function of the average pellets diameter
dpe and the fluid-to-solid Nusselt number for which the fluid dynamic viscosity
μ is needed (and should be set in the
Fluid (Porous Medium) subnode). Or set a
User defined value or expression for
hpe,f.
To display this section, click the Show More Options button (
) and select
Advanced Physics Options in the
Show More Options dialog box. The settings of this section have no effect when the
Coupling condition is
Convective heat flux in the
Pellet-Fluid Interface section.
The Constraint settings can be set to
Pointwise constraints (default) or
Weak constraints. Select
Weak constraints to replace the standard constraints with a weak implementation.
Physics tab with Porous Medium selected in the model tree:
