ACU-T: 3204 Radiation Heat Transfer in a Simple Headlamp using the Discrete Ordinate Model

Prerequisites

This tutorial introduces you to setting up a radiation heat transfer problem using the Discrete Ordinate radiation model in HyperMesh and solving using AcuSolve. Prior to starting this tutorial, you should have already run through the introductory tutorial, ACU-T: 1000 HyperWorks UI Introduction, and have a basic understanding of HyperMesh, AcuSolve, and HyperView. To run this simulation, you will need access to a licensed version of HyperMesh and AcuSolve.

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

Since the HyperMesh database (.hm file) contains meshed geometry, this tutorial does not include steps related to geometry import and mesh generation.

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 to the air and lens volume. The outer surfaces of the headlamp are assumed to be at a constant temperature of 300 K.
The air and the lens are modeled as participating media for radiation heat transfer. For the purpose of this tutorial, the absorption coefficient of air is considered to be zero. The following radiation material properties are used for the air and the lens volumes.
Table 1.
Absorption Coefficient Refractive Index
Air 0 1.0
Lens 900 1.57
For simulations involving participating media, the following radiation surface types must be defined at the boundaries of each participating medium.
Table 2.
Participating medium - Participating medium Interface Radiation Interface - Internal
Participating medium - (Non- Participating) medium Interface Wall
External boundaries of Participating medium Radiation Interface - External or Wall
The discrete ordinate radiation model implementation in AcuSolve allows for modeling specular, diffuse, and partially specular interfaces. This can be done by specifying the appropriate value of diffused fraction while defining the radiation surfaces. For the diffused fraction, a value of 1 means the surface is purely diffuse, a value of 0 means it is purely specular. Any value between 0 and 1 means the surface is partially specular. In this tutorial, since both the air and lens are modeled as participating media, the lens-air interface and the lens-outer surfaces will be modeled as internal and external radiation interface respectively. The internal interface will be defined as a specular interface whereas the external interface will be defined as a diffuse interface.

Open the HyperMesh Model Database

1. Start HyperMesh Desktop and load the AcuSolve user profile.
Refer to the HM introductory tutorial, ACU-T: 1000 HyperWorks UI Introduction, to learn how to select AcuSolve from User Profiles.
2. Click the Open Model icon located on the standard toolbar.
The Open Model dialog opens.
3. Browse to the directory where you saved the model file. Select the HyperMesh file ACU-T3204_HeadlampDO.hm and click Open.
4. Click File > Save As.
The Save Model As dialog opens.
5. Create a new directory named Headlamp_DO and navigate into this directory.
This will be the working directory and all the files related to the simulation will be stored in this location.
6. Enter Headlamp_DO as the file name for the database, or choose any name of your preference.
7. Click Save to create the database.

Set the General Simulation Parameters

Set the Analysis Parameters

1. Go to the Solver Browser, expand 01.Global, then click PROBLEM_DESCRIPTION.
2. In the Entity Editor, verify that the Analysis type is set to Steady State.
3. Set the Temperature equation to Advective Diffusive.
4. Set the Radiation equation to Discrete Ordinate.
6. Set the Turbulence model to Laminar (if not set already).

Specify the Solver Settings

1. In the Solver Browser, click 02.SOLVER_SETTINGS under 01.Global.
2. In the Entity Editor, change the Relaxation factor to 0.4.
3. Turn On Temperature flow.
4. Leave the remaining options unchanged.

Define the Material Models and the Body Force

Define the Material Models

1. In the Solver Browser, expand 02.Materials > Fluid then click on Air_HM.
2. In the Entity Editor, change the Density type to Boussinesq.
4. Set the Absorption coefficient to 0 and Refractive index to 1.
5. In the Solver Browser, under 02.Materials, right-click on SOLID and select Create.
6. In the Entity Editor, name it Arnite.
7. Set the Density to 1670 kg/m3.
8. Set the Specific heat to 2050 J/kg-K.
9. Set the Conductivity to 1.65 W/m-K.
11. Set the Absorption coefficient to 900 and the Refractive index to 1.57.
12. Repeat steps 5-9 and create two more solid material models, Plastic and LED, with the following material properties:
Radiation properties do not need to be defined for these two materials.
1. Plastic:
1. Density - 1270 kg/m3
2. Specific heat - 1900 J/kg-K
3. Conductivity to 0.22 W/m-K
2. LED:
1. Density - 5500 kg/m3
2. Specific heat - 0.3 J/kg-K
3. Conductivity to 5.0 W/m-K
13. Save the database.

Define the Body Force

1. In the Solver Browser, expand 03.Body_Force > BODY_FORCE then click on Gravity_HM.
2. In the Entity Editor, set the Y-Gravity to -9.81 m/sec2 and change to Z-Gravity to 0.

Define the Heat Source

1. In the Solver Browser, right-click on 03.Body_Force and select Create.
2. In the Entity Editor, name it LED Heat Source.
3. Change the Medium to Solid.
4. Set the Heat source unit type to Per unit volume.
5. Set the Heat Source type to Constant and set the Volumetric heat source to 2049180 W/m3.

Set the Boundary Conditions

Create the Emissivity Model

1. In the Solver Browser, right-click on 07.Emissivity_Model and select Create.
2. In the Entity Editor, name it Inner.
3. Set the Emissivity to 0.05.

Set the Boundary Conditions

By default, all components are assigned to the wall boundary condition. In this step, you will change them to the appropriate boundary conditions and assign material properties to the fluid volumes.
1. In the Solver Browser, expand 12.Surfaces > WALL.
2. Click Air. In the Entity Editor,
1. Change the Type to FLUID.
2. Set the Material to Air_HM.
3. Set the Body force to Gravity_HM.
3. Click Housing. In the Entity Editor,
1. Change the Type to SOLID.
2. Set the Material to Plastic.
4. Click Bulb. In the Entity Editor,
1. Change the Type to SOLID.
2. Set the Material to LED.
3. Set the Body force to LED Heat Source.
5. Click Lens. In the Entity Editor,
1. Change the Type to SOLID.
2. Set the Material to Arnite.
6. Click Lens-inner. In the Entity Editor, verify that the Type is set to WALL. Under the Radiation Surface tab,
1. Activate the Display checkbox and set the Active radiation surface field to On.
2. Set the Type to Radiation Interface and the Radiation interface type to Internal.
3. Set the Diffused fraction to 0.
7. Click Lens-outer. In the Entity Editor, verify that the Type is set to WALL. Set the Temperature BC type to Value and set the Temperature to 300 K. Under the Radiation Surface tab,
1. Activate the Display checkbox and set the Active radiation surface field to On.
2. Set the Type to Radiation Interface and the Radiation interface type to External.
3. Set the External emissivity model to Black Body.
4. Set the External refractive index to 1 and the External temperature to 300 K.
5. Set the Diffused fraction to 1.
8. Click Housing-Lens-interface. In the Entity Editor, verify that the Type is set to WALL. Under the Radiation Surface tab,
1. Activate the Display checkbox and set the Active radiation surface field to On.
2. Set the Type to Wall and the Emissivity model to Black Body.
3. Set the Diffused fraction to 1.
9. Click Housing-inner. In the Entity Editor, verify that the Type is set to WALL. Under the Radiation Surface tab,
1. Activate the Display checkbox and set the Active radiation surface field to On.
2. Set the Type to Wall and the Emissivity model to Inner.
3. Set the Diffused fraction to 1.
10. Click Housing-outer. In the Entity Editor,
1. Verify that the Type is set to WALL.
2. Set the Temperature BC type to Value.
3. Set the Temperature to 300 K.
11. Click Bulb_walls. In the Entity Editor, verify that the Type is set to WALL. Under the Radiation Surface tab,
1. Activate the Display checkbox and set the Active radiation surface field to On.
2. Set the Type to Wall and the Emissivity model to Black Body.
3. Set the Diffused fraction to 1.
12. Save the model.

Run AcuSolve

In this step, you will launch AcuSolve to compute a solution for this case.

1. Turn on the visibility of all mesh components.
For the analysis to run, the mesh for all active components must be visible.
2. Click on the ACU toolbar.
The Solver job Launcher dialog opens.
3. Optional: For a faster solution time, set the number of processors to a higher number (4 or 8) based on availability.
4. Leave the remaining options as default and click Launch to start the solution process.

Post-Process the Results with HyperView

In this step, you will visualize the results using HyperView. While doing so, you will create contour plots of temperature and incident radiation on a section cut. Once the solver run is complete, close the AcuProbe and AcuTail windows. In the HyperMesh Desktop window, close the AcuSolve Control tab and save the model.

Switch to the HyperView Interface and Load the AcuSolve Model and Results

1. In the HyperMesh Desktop window, click the ClientSelector drop-down in the bottom-left corner of the graphics window.
2. Select HyperView from the list.
3. In the pop-up dialog that appears, click Yes.
The interface is changed to HyperView.

Once HyperView is loaded, the Load model and results panel should be open by default. If you do not see the panel, click File > Open > Model.

4. In the Load model and results panel, click next to Load model.
5. In the Load Model File dialog, navigate to your working directory and select the AcuSolve .Log file for the solution run that you want to post-process. In this example, the file to be selected is Headlamp_DO.1.Log.
6. Click Open.
7. Click Apply in the panel area to load the model and results.

Create Temperature and Incident Radiation Contours on a Section Cut

1. Orient the display to the xy-plane by clicking on the Standard Views toolbar.
2. On the 3DViewControls toolbar, right-click on multiple times until the orientation of the model is as shown in the figure below.
3. Click the Section cut icon on the HV-Display toolbar.
4. In the panel area, click Add to create a new section cut named Section 1.
5. In the Define plane section, set the axis to X Axis then click Apply.
6. Change the Display options from Clipping plane to Cross section.
7. Click Gridline. In the Gridline Options dialog, deactivate the Show check box under Grid line then click OK.
8. Click on the Results toolbar to open the Contour panel.
9. In the panel area, set the Result type to Temperature (s).
10. Click the Components entity selector. In the Extended Entity Selection dialog, select All.
11. Click Apply.
12. In the panel area, under the Display tab, turn off the Discrete color option.
13. Click the Legend tab then click Edit Legend. In the dialog, change the Numeric precision to 2 then click OK.
The contour plot should look like the one shown in the figure below.
14. In the panel area, change the Result type to Incident_radiation then click Apply.

As seen in the figure above, the rays travel from the bulb through the air and lens before getting radiated to the atmosphere.

Summary

In this tutorial, you learned how to set up and solve a radiation heat transfer problem in a headlamp using the discrete ordinate radiation model in AcuSolve. You started by importing the HyperMesh database with the mesh and basic model organization, and then set up the simulation parameters and boundary conditions. Once the solution was computed, you processed the results using HyperView, where you created contour plots of temperature and incident radiation.