Pellets (Porous Medium)
This node defines the porosity and material properties of the pellets contained in a packed bed, used in the heat transfer equations of the Porous Medium parent node, when the Packed bed option is selected in the Porous medium type list. The coupling condition between the pellets and the fluid phase of the packed bed can be specified in the Pellet-Fluid Interface (Porous Medium) subnode.
Model Input
This section contains fields and values that are inputs for expressions defining material properties. If such user-defined property groups are added, the model inputs appear here.
Volume Reference Temperature
This section is available when a temperature-dependent density defined in a material is used. On the material frame, the density is evaluated in relation to a reference temperature in order to ensure conservation of the mass in the presence of temperature variations. By default the Common model input is used. This corresponds to the variable minput.Tempref, which is set to 293.15 K by default. To edit it, click the Go to Source button (), and in the Default Model Inputs node under Global Definitions, set a value for the Volume reference temperature in the Expression for remaining selection section.
Other options are User defined and all the temperature variables from the physics interfaces included in the model.
This model input does not override the Reference temperature Tref set in the Physical Model section of the physics interface, which is used to evaluate the reference enthalpy, and a reference density for incompressible nonisothermal flows.
Temperature
This section is available when material properties are temperature-dependent. By default, the temperature of the parent interface is used and the section is not editable. To edit the Temperature field, click Make All Model Inputs Editable (). The available options are User defined (default), Common model input (the minput.T variable, set to 293.15 K by default) and all temperature variables from the physics interfaces included in the model. To edit the minput.T variable, click the Go to Source button (), and in the Default Model Inputs node under Global Definitions, set a value for the Temperature in the Expression for remaining selection section.
Porosities
The default Bed porosity εp of the packed bed is taken From material. In a Porous Material node, the porosity is defined as follows:
where θsi, θpe and θimfi are the volume fractions of the Solid, Pellet, and Immobile Fluid subnodes under the Porous Material node.
For User defined, enter a value or expression.
As porosity can be considered within the pellets, set the Pellet porosity, εpe. By default it is taken From material. Go to the Pellet subnode of the Porous Material node to enter a value or expression.
Heat Conduction, Pellets
Set the thermal conductivity of the porous matrix within the pellets, kpe. It is used to compute the effective thermal conductivity of the pellet filled with fluid, kpe,eff, defined by
The default Thermal conductivity kpe is taken From material. For User defined, enter a value or expression. A scalar value should be set as it is used in the 1D microscale equation.
Thermodynamics, Pellets
This section defines the thermodynamics properties of the porous matrix within the pellets.
The specific heat capacity describes the amount of heat energy required to produce a unit temperature change in a unit of mass of the pellets.
The Density ρpe and the Specific heat capacity Cp, pe should be specified. For From Material option, see Material Density in Features Defined in the Material Frame if a temperature-dependent density should be set.
These properties are used to compute the effective volumetric heat capacity at constant pressure inside the pellet filled with fluid, (ρCp)pe,eff, defined by
Location in User Interface
Context Menus
Heat Transfer in Porous Media>Porous Medium>Pellets
Ribbon
Physics tab with Porous Medium selected in the model tree:
Attributes>Pellets