Pellet

Right-click a node to add a subnode (

) to define properties of a pellet phase in the porous medium.. The subnode provides the properties for a certain type of pellets that the solid part of the porous material consists of. A porous material can include pellets of different types. For example, the pellets might be a mix of 30% spherical pellets with a certain diameter, 20% spherical pellets with another diameter, and 50% of a third type of pellet that is cylindrical instead of spherical. Those 100% together form the solid phase in the “pellet bed”.

A node provides the geometrical properties for pellets and material properties for the solid phase in the pellet, such as density and heat capacity. The material properties for the fluid phase should be defined in a Fluid subnode.

When a node is used in the physics, then all pellet types will exist at each point in the geometry. Therefore, the plural form, as a subnode to the node, used in the Chemical Reaction Engineering Module to model packed bed reactors with catalytic pellets. Also, as a subnode to the node can be used to model the local temperature field within pellets when using a Heat Transfer in Porous Media interface.

From the list, choose the material to represent the pellet: (the default), or select any other material that you have added. Click the button (

) to move to the selected material’s node. Click the button (

to add a material from the window. You can also click the downward arrow next to the button and choose to add a new blank material. In both cases, the added material becomes selected in the list.

From the list, define the shape of the pellet: (the default), , , or . For and , further specify a dpe (SI unit: m), where the default value is 1 mm. For , define a dpe (SI unit: m) in a similar way. For , specify the Ape (SI unit: m2) and Vpe (SI unit: m3).

Also specify a εpe as a relative number between 0 and 1 (default: 0.1). This is the microscale porosity of the inside of an individual pellet.

If you define a second subnode, the section below is not available. Instead, specify a , a relative number between 0 and 1. Only the first subnode can define the pellet bed porosity. For additional subnodes, you instead specify the volume fraction relative to the other pellet types.

In this section you specify the porosity of the pellet bed. From the list, choose (the default) or . With , add a value for the porosity εp as a relative number between 0 and 1 (default: 0.26, representing perfectly packed spheres). With , the porosity is defined as 1 − ρb/ρpe, where you define the density of the packed bed, ρb, in the field (default: 800 kg/m3).

In this section you specify the properties of the mesh for the extra dimension that each subnode defines so that both the species concentration and the temperature can be computed locally in the pellet.

For the mesh distribution, choose , (the default), or from the list. Also, specify the (default: 6).

Click the button (

) in the section toolbar to get a plot of the extra dimension mesh in a separate plot window, showing the mesh distribution and direction.

This section is only available if you have selected from the list in the section. You can then choose material properties that you want to add for the pellet from the list and then click the button (

) to add those properties to the table in the section below.

The table in this section contains the material properties for the pellet material. When the in the section is , enter values or expressions for the properties in the column. You can also click the button (

) below the table to enter the property values.