Specifying Surface Materials and Radiation Properties

You specify the radiation properties—emissivity, reflectivity, and transmissivity—at the boundaries and interfaces in this simulation. You do this by creating and defining a surface material for each boundary and interface.

As the radiation properties are identical either side of the interfaces in this tutorial, you define a surface material for each interface in the material database, and assign these to both the fluid and solid continua. You specify radiation properties for the remaining boundaries by defining surface materials within the specific continuum associated with those boundaries. The radiation models assume Kirchhoff’s Law, that is, for each boundary or interface, emissivity + reflectivity + transmissivity = 1.
To specify surface materials and radiation properties:
  1. Specify the radiation properties for the interface materials using the material database:
    1. Right-click the Tools > Material Databases > Standard > SurfaceMaterials node and select New > New Surface Material….
    2. Select the Surface Material 1 (Surface Material 1) node and set the following properties:
      Property Setting
      Title Interface 2
      Symbol bottom-solid1
    3. Right-click the bottom-solid1 (Interface 2) node and select New Database Properties….
    4. In the Select Material Properties and Methods dialog, select the following material properties:
      • Emissivity > Constant
      • Transmissivity > Constant
    5. Expand the bottom-solid1 (Interface 2) node and set the following properties:
      Node Property Setting
      Emissivity > Constant Value 0.775
      Transmissivity > Constant Value 0.15
    6. Create four additional surface materials within the SurfaceMaterials database.
    7. Edit the SurfaceMaterials node and, following the procedure outlined in Step 1: b–e, set the following properties:
      Node Property Setting
      Surface Material 1 (Surface Material 1) Title Interface 4
      Symbol bottom-solid2
      Emissivity > Constant Value 0.725
      Transmissivity > Constant Value 0.175
      Node Property Setting
      Surface Material 2 (Surface Material 2) Title Interface 1
      Symbol top-solid1
      Emissivity > Constant Value 0.8
      Transmissivity > Constant Value 0.15
      Node Property Setting
      Surface Material 3 (Surface Material 3) Title Interface 3
      Symbol top-solid2
      Emissivity > Constant Value 0.75
      Transmissivity > Constant Value 0.175
  2. Specify the surface materials and radiation properties for the Air continuum:
    1. Right-click the Continua > Air > Models > Surface Materials > Surface Materials node and select Select Surface Materials….
    2. In the Select Surface Materials dialog, select the following surface materials:
      • bottom-solid1 (Interface 2)
      • bottom-solid2 (Interface 4)
      • Cast Iron (Cast Iron)
      • Surface Material 4 (Surface Material 4)
      • top-solid1 (Interface 1)
      • top-solid2 (Interface 3)
    3. Click Apply and Close.


    4. Select the Surface Materials node and rename the following nodes:
      Node Name
      Cast Iron Sides
      Default Collector
      Surface Material 4 Top
    5. Edit the Surface Materials node and set the following properties:
      Node Property Setting
      Sides
      Material Properties
      Emissivity > Constant Value 0.95
      Transmissivity > Constant Value 0.0
      Top
      Material Properties
      Emissivity > Constant Value 0.8
      Transmissivity > Constant Value 0.15
      Collector
      Material Properties
      Emissivity > Constant Value 1.0
      Transmissivity > Constant Value 0.0
      注You do not specify the reflectivity at the boundaries or interfaces since, by Kirchhoff’s Law, Reflectivity = 1 - Emissivity - Transmissivity.
You define the radiation properties for the solid continuum in a similar way to the fluid one.
  1. Specify the surface materials and radiation properties for the Glass continuum:
    1. Expand the Continua > Glass > Models > Surface Materials > Surface Materials node.
    2. Right-click the Surface Materials node and select Select Surface Materials….
    3. In the Select Surface Materials dialog, select the following surface materials:
      • bottom-solid1 (Interface 2)
      • bottom-solid2 (Interface 4)
      • top-solid1 (Interface 1)
      • top-solid2 (Interface 3)
    4. Click Apply, then Close.
    5. Rename the Surface Materials > Default node to side-solid.
    6. Edit the Surface Materials > side-solid1 > Material Properties node and set the following properties:
      Node Property Setting
      Emissivity
      Constant Value 0.0
      Reflectivity Method Constant
      Constant Value 1.0
      Transmissivity
      Constant Value 0.0
  2. Save the simulation.