Materials
The next step is to specify material properties for the model. Ready-to-use materials can be selected from the available libraries or generated from Thermodynamics. In this model, first generate a material node for nitrogen (solvent) from our Gas System, under Thermodynamics. After that, generate the solid monolith material. Both these materials are then used to create a Porous Material.
The created materials are assigned to the relevant selections in the geometry. This allows the physics interfaces in these selections to access the material properties.
Generate Material
1
In the Model Builder, under Global Definitions , locate Thermodynamics  > Gas System .
2
Right-click on Gas System and choose Generate Material .
This opens the Generate Material wizard which consists of several steps to create a Material node from our property package.
3
In Select Phase window, choose Gas (default) and click Next .
4
All species in the system has been added to the Select species table by default.
5
In the Material composition section, click the mass fraction button
6
Use the table to set mass fraction of nitrogen as 1 and 0 for others.
7
Click Next  in the wizard.
8
In the Select Properties window, choose Diffusion coefficient at infinite dilution, and click Add Selected .
9
In the Select solvent subsection, choose nitrogen in the list of species. Click Next .
10
In the Define Material window, choose Global from the Component list. This adds the material to the global Material node and thus makes it accessible in any component in the model.
11
From the Function type list, choose Interpolation. This creates fast to evaluate interpolation functions for the material properties.
12
Set the Temperature upper bound (High) to 733.
13
Click Finish  to create the material.
Gas: Nitrogen Solvent
1
In the Model Builder, expand the Global Definitions > Materials node, and select the created material node where the composition is indicated:
Gas: ammonia(0)-nitrogen(1)-nitrogen oxide(0)-oxygen(0)- water(0) .
2
In the Settings window, change the Label to Gas: Nitrogen Solvent, to use a simpler name.
Next, create a user-defined material and associate it with the solid monolith material.
Solid: Monolith Material
1
In the Materials toolbar, click Blank Material .
2
In the Model Builder window, expand the Material 1 node, then click Basic.
3
In the Settings window, locate the Output Properties section. Click Select Quantity below the table.
4
In the Physical Quantity dialog, type density in the text field and click Filter . Select Density (kg/m^3). Click OK.
5
Perform the same action for the properties heat capacity (choose Heat capacity at constant pressure (J/(kg·K)) and thermal conductivity (choose Thermal conductivity (W/(m·K)).
6
Add expressions to the Output Properties section. Type 2970[kg/m^3] for the density, 975[J/kg/K] for the heat capacity, and 35[W/m/K] for the thermal conductivity.
7
In the Model Builder window, select the Material 1 and type Solid: Monolith Material in the Label field to name it accordingly.
In the next stage of the modeling process, add a Porous Material that consists of the two materials that were just defined.
Porous Material
1
In the Materials toolbar, click More Materials and choose Local > Porous Material .
2
In the Settings window for Porous Material, locate the Geometric Entity Selection section. From the Selection list, choose Domains 3, 5, and 14.
Fluid
3
Right-click Porous Material and choose Fluid from the context menu. Notice that the generated global material Gas: Nitrogen Solvent is predefined for this node.
4
Right-click Porous Material and choose Solid from the context menu.
5
In the Solid Properties section, choose Solid: Monolith Material in the Material list.
6
In the Volume fraction θs text field, type 1-por.
Add a material for the metal parts of the reactor.
Metal
1
In the Home toolbar, click  Windows and choose Add Material from Library.
2
Go to the Add Material window.
3
In the tree, select Built-in > Structural steel.
4
Click the Add to Component button in the window toolbar.
5
In the Settings window for Material, locate the Geometric Entity Selection section.
6
From the Selection list, choose Metal Shell Domain.
Note: A description of how to set up these selections can be found in Geometry.
Add a material for the insulating air in the reactor wall.
Air
1
In the Home toolbar, click  Windows and choose Add Material from Library.
2
Go to the Add Material window.
3
In the tree, select Built-in > Air.
4
Click the Add to Component button in the window toolbar.
5
In the Home toolbar, click  Add Material to close the Add Material window.
6
In the Settings window for Material, locate the Geometric Entity Selection section.
7
From the Selection list, choose Insulating Gas.
Add a Material Link to the nitrogen gas to create a material for the free flowing gas between the two catalysts.
Free Flow Domain Material
1
In the Model Builder window, right-click Materials and choose More Materials > Material Link.
2
In the Settings window for Material Link, locate the Geometric Entity Selection section.
3
From the Selection list, choose Free Flow Domain.
4
In the Label text field, type Free Flow Domain Material.
Complete the settings for the two Chemistry interfaces by setting the concentration of nitrogen and coupling the ammonia slip catalyst chemistry to the mass transfer interface.