ACU-T: 3200 Radiation Heat Transfer in a Simple Headlamp using the Enclosure Radiation Model

Prerequisites

This tutorial introduces you to the workflow for setting up a thermal radiation problem in a headlamp using the enclosure radiation model in HyperWorks CFD. Prior to starting this tutorial, you should have already run through the introductory HyperWorks tutorial, ACU-T: 1000 HyperWorks UI Introduction, and have a basic understanding of HyperWorks CFD and AcuSolve. To run this simulation, you will need access to a licensed version of HyperWorks CFD and AcuSolve.

Before you begin, copy the file(s) used in this tutorial to your working directory.

Problem Description

The problem to be solved is shown schematically in Figure 1 and Figure 2. It consists of a simple headlamp with a housing, lens, and a bulb. The inner cavity of the bulb is filled with air and the wattage of the bulb is 1W, which is modeled as a volumetric heat source. The Boussinesq density model is used for the air to consider the natural convection effects in the fluid volume. The heat generated in the bulb is transferred by three means: conduction from the bulb to the housing, natural convection in the air volume, and radiation from the bulb surface to other surfaces. The external reference temperature is 300 K for the outer surfaces of the headlamp. You will use the Enclosure radiation model to simulate the surface to surface radiation.


Figure 1.
The enclosure radiation methodology in AcuSolve involves a two-step process: view factor computation and heat flux addition. View factor is the proportion of radiation incident one surface due to another surface. The view factors are computed, and the radiative heat fluxes are added to the energy equation during the solver run. These radiative heat fluxes are computed based on the view factors using the Stefan-Boltzmann law. The enclosure radiation model is supported only on fluid mediums.


Figure 2.

Start HyperWorks CFD and Create the HyperMesh Model Database

  1. Start HyperWorks CFD from the Windows Start menu by clicking Start > Altair <version> > HyperWorks CFD.
    When HyperWorks CFD is loaded, the Geometry ribbon is open by default.
  2. Create a new .hm database in one of the following ways:
    • From the menu bar, click File > Save.
    • From the Home tools, Files tool group, click the Save As tool.


      Figure 3.
  3. In the Save File As dialog, navigate to the directory where you would like to save the database.
  4. Enter Headlamp_Enclosure as the name for the database then click Save.
    This will be your problem directory and all the files related to the simulation will be stored in this location.

Import and Validate the Geometry

Import the Geometry

  1. From the menu bar, click File > Import > Geometry Model.
  2. In the Import File dialog, browse to your working directory then select ACU-T3200_headlamp.x_t and click Open.
  3. In the Geometry Import Options dialog, leave all the default options unchanged then click Import.


    Figure 4.


    Figure 5.

Validate the Geometry

  1. From the Geometry ribbon, click the Validate tool.


    Figure 6.
    The Validate tool scans through the entire model, performs checks on the surfaces and solids, and flags any defects in the geometry, such as free edges, closed shells, intersections, duplicates, and slivers.
    The surface and solid errors display in the list below the tool.


    Figure 7.
  2. Click SolidChecks.
    The Solid Repair tool opens, which you can use to fix the geometric errors in the model.
    From the SolidChecks legend, you can see the model's solids have five intersections.


    Figure 8.
  3. Click Intersections.
    A guide bar used to fix intersecting solids displays.
  4. Optional: Click and to review each error.
  5. Activate the Keep common interface option then click Combine All.
    The SolidChecks legend should now display zero for all errors.
  6. Click the Validate tool once again.
    Observe that a blue check mark now appears on the top-left corner of the tool icon. This indicates that no issues are detected and you are ready to continue.


    Figure 9.

Set Up Flow

Set the General Simulation Parameters

  1. From the Flow ribbon, click the Physics tool.


    Figure 10.
    The Setup dialog opens.
  2. Under the Physics models setting:
    1. Verify that Time marching is set to Steady.
    2. Select Laminar as the Turbulence model.
    3. Activate the Include gravitational acceleration checkbox and set the gravity in the y direction to -9.81.
    4. Activate the Heat transfer checkbox.


    Figure 11.
  3. Click the Solver controls setting and activate the Thermal flow equation.


    Figure 12.
  4. Close the dialog and save the model.

Define the Material Models

  1. From the Flow ribbon, click the Material Library tool.


    Figure 13.
    The Material Library dialog opens.
  2. Click the My Materials tab.
  3. Click to add a new fluid material model.
  4. In the material creation dialog, click the name in the top-left corner and rename the material to Air_Boussinesq.
  5. In the Density tab,
    1. Set the Type to Boussinesq.
    2. Set the Density value to 1.225.
    3. Set the Expansivity value to 0.00347222.
    4. Reference temperature value to 288.


    Figure 14.
  6. Click the Specific Heat tab and set the Specific heat value to 1005.


    Figure 15.
  7. Click the Viscosity tab and set the Viscosity value to 1.781e-05.


    Figure 16.
  8. Click the Conductivity tab and set the Conductivity value to 0.02521.


    Figure 17.
  9. Close the material creation dialog to return to the Material Library dialog.
  10. Select Solid in the Settings menu, click the My Materials tab, then click to create a new solid material model.
  11. Name the material Plastic and set the following values.
    The Type should be Constant for each property.
    • Density: 1270
    • Specific Heat: 1900
    • Conductivity: 0.2
  12. Close the material creation dialog to return to the Material Library dialog.
  13. Similarly, create new solid material models named Arnite and LED with the following properties.
    The Type should be Constant for each property.
    Arnite:
    • Density: 1670
    • Specific Heat: 2050
    • Conductivity: 1.6
    LED:
    • Density: 5500
    • Specific Heat: 0.3
    • Conductivity: 5.0


    Figure 18.
  14. Close all dialogs and save the model.

Assign Material Properties

  1. From the Flow ribbon, click the Material tool.


    Figure 19.
  2. Click the lens volume highlighted in the figure below and select Arnite from the Material drop-down menu.


    Figure 20.
  3. On the guide bar, click to execute the command and remain in the tool.
  4. Click the housing volume and assign the Plastic material model.


    Figure 21.
  5. On the guide bar, click to execute the command and remain in the tool.
  6. In the Materials legend, right-click on Air and select Isolate.
  7. Click the air volume and assign the Air_Boussinesq material model.


    Figure 22.
  8. On the guide bar, click to execute the command and remain in the tool.
  9. In the Materials legend, right-click on Air and select Isolate.
  10. Click the bulb volume and assign the LED material model.


    Figure 23.
  11. On the guide bar, click to execute the command and exit the tool.
  12. Save the model.

Define the Heat Source

  1. From the Flow ribbon, click the Sources > Heat tool.


    Figure 24.
  2. In the modeling window, select the bulb volume.
  3. In the Heat Source dialog, set the heat source value to 2049180 W/m3.


    Figure 25.
  4. On the guide bar, click to execute the command and exit the tool.
  5. Press Esc to exit the Sources tool then press the A key to turn on the display of all solids.
  6. Save the model.

Define Flow Boundary Conditions

In this problem, all the surfaces are walls and will therefore be assigned the default wall boundary condition. The outer walls of the headlamp will be given a no-slip wall boundary condition with a convective heat flux boundary condition.

  1. From the Flow ribbon, click the No Slip tool.


    Figure 26.
  2. In the modeling window, select the surfaces highlighted in the figure below.


    Figure 27.
  3. In the microdialog, enter the values shown in the figure below.


    Figure 28.
  4. In the Boundaries legend, double-click Wall, rename it to Outerwalls, then press Enter.
  5. On the guide bar, click to execute the command and exit the tool.
  6. Save the model.

Set Up Radiation

In this step, you will specify the parameters related to the thermal radiation setup.

Define Radiation Model Settings

  1. From the Radiation ribbon, Thermal Radiation tools, click the Physics tool.


    Figure 29.
    The Radiation Settings dialog opens.
  2. Activate Thermal radiation and set the Radiation model to Enclosure (if not set already).


    Figure 30.
  3. Close the dialog.

Define the Emissivity Models

  1. From the Radiation ribbon, click the Surface Finish Library tool.


    Figure 31.
    The Surface finish library opens.
  2. Click to add a new emissivity model.
  3. Set the Name of the model to Walls and the Emissivity value to 0.7 by double-clicking on the entity fields.


    Figure 32.
  4. Close the dialog.

Assign Surface Finish Models

  1. From the Radiation ribbon, click the Surface Finish tool.


    Figure 33.
  2. Using the window selection method, select all the surfaces in the model.


    Figure 34.
  3. In the microdialog, assign the Walls emissivity model.
  4. On the guide bar, click to execute the command and exit the tool.
  5. Save the model.

Generate the Mesh

In this step, you will define the mesh controls and then generate the mesh.

Define the Surface Mesh Controls

  1. From the Mesh ribbon, click the Surface tool.


    Figure 35.
  2. Using the window selection method, select all the surfaces in the model.
  3. In the microdialog, set the Average element size to 0.002.


    Figure 36.
  4. On the guide bar, click to execute the command and exit the tool.

Define the Boundary Layer Controls

  1. From the Mesh ribbon, click the Boundary Layer tool.


    Figure 37.
  2. Right-click in the modeling window and go to Select > Advanced Select > By Material > Air_Boussinesq.
    All the fluid wall surfaces should be selected and a microdialog for BL specification appears.
  3. Enter the following values in the microdialog:
    • First layer thickness definition: Constant
    • First layer thickness: 0.0005
    • Total number of layers: 4
    • Growth method: Constant
    • Initial growth rate: 1.3
    • Termination policy: Truncate
    • Activate the Enable surface mesh modification option


    Figure 38.
  4. On the guide bar, click to execute the command and exit the tool.

Define the Volume Mesh Controls

Since the thickness of the housing and the lens solids are small, you will use the thin layer meshing tool so that when the volume mesh is generated, there will be two layers across the thickness of those solids.

  1. From the Mesh ribbon, click the Volume Mesh tool.


    Figure 39.
  2. Select the housing and the lens solids.
  3. In the microdialog,
    1. Set the Average size to 0.001.
    2. Set the Growth rate to 1.0.
    3. Activate the Thin layer meshing option and set the Number of layers to 2.


    Figure 40.
  4. On the guide bar, click to execute the command and exit the tool.

Generate the Mesh

  1. From the Mesh ribbon, click the Volume tool.


    Figure 41.
    The Meshing Operations dialog opens.
  2. Set the Mesh growth rate to 1.
  3. Click Mesh.
    The Run Status dialog opens. Once the run is complete, the status is updated and you can close the dialog.
    Tip: Right-click on the mesh job and select View log file to view a summary of the meshing process.
  4. Save the model.

Run AcuSolve

  1. From the Solution ribbon, click the Run tool.


    Figure 42.
    The Launch AcuSolve dialog opens.
  2. Set the Parallel processing option to Intel MPI.
  3. Optional: Set the number of processors to 4 or 8 based on availability.
  4. Expand the Default initial conditions menu and deactivate the Pre-compute flow option.
  5. Set the x-velocity to 0 and the Temperature to 300.
  6. Leave the remaining options as default and click Run to launch AcuSolve.


    Figure 43.
    The Run Status dialog opens. Once the run is complete, the status is updated and you can close the dialog.
    Tip: While AcuSolve is running, right-click on the AcuSolve job in the Run Status dialog and select View Log File to monitor the solution process.

Post-Process the Results with HW-CFD Post

  1. Once the solution is completed, navigate to the Post ribbon.
  2. From the menu bar, click File > Open > Results.
  3. Select the AcuSolve log file in your problem directory to load the results for post-processing.
    The solid and all the surfaces are loaded in the Post Browser.
  4. Hide the Outerwalls boundary surface in the Post Browser.


    Figure 44.
  5. Select the inner surface of the lens in the modeling window, right-click, and select Hide.


    Figure 45.
  6. Similarly, hide the outer fluid surface.
    You should end up with a view as shown below.


    Figure 46.
  7. Click the Boundary Groups tool.


    Figure 47.
  8. Select all visible surfaces in the modeling window.
    Rotate the model if needed to select the rear surfaces.
  9. In the display properties microdialog, set the display to temperature.
  10. Activate the Legend toggle and click to reset the range.
  11. Click , set the Legend location to Upper Right Corner, and the Colormap Name to Rainbow Uniform.


    Figure 48.
  12. Click on the guide bar.
  13. Click the Top face on the View Cube to align the model.


    Figure 49.


    Figure 50.

Summary

In this tutorial, you learned how to set up and solve a radiation heat transfer problem in a headlamp using the enclosure radiation model in AcuSolve using HyperWorks CFD. You started by importing the headlamp geometry file, then you set up the simulation parameters and boundary conditions. Once the solution was computed, you processed the results using the Post ribbon where you created contour plots of temperature.