5.2.1.6. Enclosure Example

If your problem has non-meshed internal voids and you want to model radiative heat transfer through these voids, you need to define an enclosure.

5.2.1.6.1. Problem Files

The files required for this example can be downloaded here, or found at $TESTS/aria_rtest/example/training/enclrad (where TESTS=/projects/sierra/tests in a CEE environment, or your Sierra test distribution otherwise).

• Input File

• Mesh

5.2.1.6.2. Input Deck Modification

There are a few things that need to be modified in an input deck to include enclosure radiation. These are

1. Ensure that the Global Constants block is present at the sierra level and includes the Stefan Boltzmann constant

# Sierra level
Begin Global Constants
  Stefan Boltzmann Constant = 5.67e-08 # W/m2-K4
End   Global Constants

2. Add a viewfactor calculation block to define which algorithm to use for calculating view factors.

# Aria Region level
Begin Viewfactor Calculation vf_hemicube
  Compute Rule = HEMICUBE
End

3. Add a viewfactor smoothing block to define which method (if any) to use for view factor smoothing.

# Aria Region level
Begin Viewfactor Smoothing vf_smooth
  Method = LEAST-SQUARES
End

4. Add a radiosity solver block to define what linear solver settings to use when solving the enclosure radiosity equation.

# Aria Region level
Begin Radiosity Solver rad_solver
  Coupling = MASON
  Solver = CHAPARRAL CG
  Convergence Tolerance = 1e-06
  Maximum Iterations = 200
End

5. Add the actual enclosure definition block, which defines the surfaces that bound the enclosure, which viewfactor calculation and smoothing models to use (from steps 2 and 3), and which radiosity solver to use (from step 4).

# Aria Region level
Begin Enclosure Definition cavity_1
    Add Surface surface_401 surface_402
    Add Surface surface_403 surface_404

    Use Viewfactor Calculation vf_hemicube
    Use Viewfactor Smoothing vf_smooth
    Use Radiosity Solver rad_solver
End

6. (optional) Ensure that the materials adjacent to an enclosure have a definition for emissivity. Alternately, this can be supplied in the enclosure definition block, but using the material properties is recommended (if you change a block from one material to another, the enclosure will use the correct emissivity for the new material).

Begin Aria Material aluminum
  Emissivity  = Constant value = 0.2
  # ...
End

If you have multiple enclosures and want to use the same settings for all of them, you do not have to repeat steps 2 to 4, just add additional enclosure definition blocks that refer to the same viewfactor calculation, smoothing method, and radiosity solver blocks.