Use the Pellets node to define intraparticle transport and reactions in a packed bed.
The pellets in use are listed in the domain selection. This corresponds to all Pellet nodes added to the
Porous Material on the domains defining the packed bed.
This section is only available in a Transport of Concentrated Species interface, where the intraparticle flow velocity and pressure is solved for.
Use this section to specify the temperature in the pellets. Select From fluid to use the temperature in the fluid surrounding the pellets. When the pellet temperature is solved for, for example using a
Heat Transfer in Pellets interface, the corresponding temperature is also available.
When surface reactions are defined in a Chemistry interface, these surface species should be coupled to those defined in the
Pellets node. This is achieved in the
Settings window of said
Chemistry interface. First, select the
Define variables for porous pellets check box in the
Pellet Chemistry section. Then choose the relevant packed bed interface in the
Species solved for list in the
Species Matching section. Finally, type in the dependent variable name in the
Surface species table. The dependent variable is found in the
Shape Functions section in the
Equation View for
Pellets.
When the check box in the Pellet Chemistry section is used, the
Chemistry interface describes the chemistry in the interior of the pellets. To also study the chemistry in the bulk fluid surrounding the pellets in the
Packed Bed, add an additional
Chemistry interface and keep said check box cleared.
When using the Transport of Concentrated Species interface, the molar mass of each surface species is required to convert between molar and mass basis. For a surface species already defined in a
Chemistry interface, say O2(ads), select
Molar mass for O2(ads) for the corresponding surface species (using the column
Molar mass from). Select
User defined to instead enter a constant value or an expression in the column
Molar mass (kg/mol).
The Pellet density specifies the density of unreacted core. The default selection is
User defined. It can also be
From material.
Select or enter the molar mass and mass fraction for solid species in Solid core species table. The molar mass can be picked up from Chemistry (with
Define variables for porous pellets being checked under
Pellet Chemistry section) from column
Molar mass from. If
User defined is selected from
Molar mass from column, then the corresponding cell under column
Molar mass (kg/mol) is enabled, where you can enter the expression for the molar mass. Finally, enter the mass fraction for each solid species under the column
Solid mass fraction (1). The mass fractions in the table will be normalized 1, then multiplied by (1-w
matrix).