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.

This section is only available in a Transport of Diluted Species interface with Pellet Type selected as Porous Catalyst and a Transport of Concentrated Species interface.

Add species to this table to account for surface reactions occurring inside the pellets. The surface species added are dependent variables and their concentrations (amount per area) will be solved for together with that of the other (bulk) species inside the pellets. The surface reaction rate for each surface species is defined in the Reactions subnode.

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).

This section is only available in a Transport of Diluted Species interface with Pellet Type selected as Shrinking Core model.

The Pellet density specifies the density of unreacted core. The default selection is User defined. It can also be From material.

There could be some solid substances (supporting material, for example) inside pellet core which don’t participate in the core consuming reactions. These substances are classified as matrix. Enter the mass fraction for Mass fraction of inert matrix. Its default value is 0.

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-wmatrix).

This section is only available in a Transport of Diluted Species interface with Pellet Type selected as Shrinking Core model.

Enter a porosity for the porous reacted layer. The default selection is User defined. It can also be From material.