Modeling Instructions: Monolith Reactor Model
First, rename the Component node.
1
In the Model Builder click Component 2.
2
Type Monolith Reactor Model in the Label text field.
Geometry
Now import a file with the reactor geometry. Symmetry reduces the modeling domain.
1
In the Model Builder window, expand the Monolith Reactor Model node.
2
Right-click Monolith Reactor Model > Geometry 1(2Daxi) and choose Insert Sequence .
3
Browse to the model’s Application Libraries folder and double-click the file monolith_reactor_geom_sequence.mph.
Note: The location of a file is based on the installation. For example, if the installation is on your hard drive, the file path might be similar to C:\Program Files\COMSOL\COMSOL64\Multiphysics\applications\.
4
In the Geometry toolbar, click  Build All.
Note: In this step-by-step, focusing on the Chemical Reaction Engineering Module, all geometry settings are already done. For information, a central part of the model setup consists of assigning features to domains and boundaries of the model geometry. The use of Explicit Selections features added to the geometry makes this process more efficient. The imported geometry sequence contains eight predefined Explicit Selection nodes. The names and the selected entities of these selections are seen in the table below.
Node Name
Domains or Boundaries Selected
SCR Catalyst
domain 5
ASC Catalyst
domain 3
Mat Domain
domain 14
Metal Shell Domain
domain 7, 15
Flow Inlet
boundary 12
Flow Outlet
boundary 6
Free Flow Domain
domain 4
Insulating Gas
domain 8-13,16-18
Domains or boundaries can be assigned to the Explicit nodes by clicking in the geometry. This adds the identification number of the domain or boundary to the Input Entities list. To remove a selection, click again to toggle.
Apart from Explicit Selections , it is also possible to add Union Selection . Such selections combine one or more Explicit Selections. This is shown later in section Union Selections in this modeling instructions.
Explicit Selections, Union Selections, and a range of other Selection nodes are available from the Selections  menu in the Geometry toolbar.
Parameters
Parameters: Temperature and Monolith Parameters
1
In the Model Builder window, under Global Definitions click Parameters: Temperature and Monolith Parameters.
2
In the Settings window for Parameters, locate the Parameters section.
3
Click Click  Load from File.
4
Browse to the model’s Application Libraries folder and double-click the file monolith_reactor_temperature_monolith_parameters.txt.
Variables
Moving on by loading variables from file. The variables in the variable expressions have not yet been created and this is indicated with yellow text in the expression fields. We load the variables from file for convenience, but the variables can also be added manually.
Variables: SCR Kinetics
1
In the Home toolbar, click Variables  and choose Local variables. Optionally, go to the Model Builder window, expand the Monolith Reactor Model, right-click Definitions , and choose Variables .
2
In the Settings window for Variables, locate the Geometric Entity Selection section.
3
From the Geometric entity level list, choose Domain.
4
From the Selection list, choose SCR Catalyst.
5
Locate the Variables section. Click  Load from File.
6
Browse to the model’s Application Libraries folder and double-click the file monolith_reactor_SCR_kinetics_variables.txt.
7
In the Label text field, type Variables: SCR Kinetics.
Variables: ASC Kinetics
1
Right-click Definitions and choose Variables.
2
In the Settings window for Variables, type Variables: ASC Kinetics in the Label text field.
3
Locate the Geometric Entity Selection section. From the Geometric entity level list, choose Domain.
4
From the Selection list, choose ASC Catalyst.
5
Locate the Variables section. Click  Load from File.
6
Browse to the model’s Application Libraries folder and double-click the file monolith_reactor_ASC_kinetics_variables.txt.
Variables: Postprocessing
1
Right-click Definitions and choose Variables.
2
In the Settings window for Variables, type Variables: Postprocessing in the Label text field.
3
Locate the Variables section. Click  Load from File.
4
Browse to the model’s Application Libraries folder and double-click the file monolith_reactor_postprocessing_variables.txt.
Generate Space-Dependent Model for the Ammonia Slip Catalyst
The Chemistry interface in the 2Daxi component contains the SCR chemistry. Generate a Chemistry interface for the ammonia slip catalyst by using the Generate Space-Dependent Model functionality.
In the Model Builder window, under Single Channel Model click Ammonia Slip Catalyst (ASC).
1
In the Reaction Engineering toolbar, click  Generate Space-Dependent Model.
2
In the Settings window for Generate Space-Dependent Model, locate the Component Settings section.
3
From the Component to use list, choose Monolith Reactor Model.
4
Locate the Physics Interfaces section. Find the Chemical species transport subsection. From the list, choose None.
5
Find the Fluid flow subsection. From the list, choose None.
6
Find the Heat transfer subsection. From the list, choose None.
7
Locate the Study Type section. From the Study type list, choose None.
8
Locate the Space-Dependent Model Generation section. Click Create/Refresh.
9
In the Model Builder window, under Monolith Reactor Model click Chemistry 2.
10
In the Settings window for Chemistry, type Chemistry: ASC in the Label text field.