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Solid Conduction Tutorial
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Solid Conduction Tutorial
The following is a list of files that will be needed for this tutorial. They can be found in the
Solid_Conduction folder.
•
Exhaust-hanger.tdf
•
Exhaust-hanger.ntl
1.0.1
Overview
The purpose of this session is to demonstrate the process of setting up and running a model with
volume element solid conduction. Solid conduction can be used to model parts that can not be
accurately modeled with shell elements.
Some objects for thermal analysis can be represented using planar mesh geometry, such as a single
plane representing a flat wall or one side of a hollow box. The "thickness" of the planar geometry
can be parametrically input. However, other objects with large interior solid volumes and low
relative surface areas are better represented by volume elements (solid conduction). The use of
solid conduction provides an alternative to planar shell conduction, and often better captures the
3-dimensional conductive pathways. Volume element solid conduction requires a 3-dimensional
volume mesh bounded by a shell mesh. Currently, tetrahedral, hexahedral, and pyramid solid
elements are supported. Conduction is calculated through the volume mesh, while the bounding
surface mesh is used for convection and radiation exchange with surrounding parts and the
environment.
A section of a vehicle exhaust pipe and a hanger are modeled in this tutorial. The geometry is
shown below. The exhaust pipe is modeled using shell elements (orange). The hanger (blue) and
connector (green) are modeled with volume elements. The connector and hanger are modeled
with volume elements because it would be difficult to approximate them with shell elements, and
we would like to see the temperature gradient through the volumes. The pipe is modeled with shell
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elements because it is a thin part. It would be impractical and unnecessary to mesh it with volume
elements.
1.0.2
Open the Patran Mesh File
1. From the Main Menu select File > Open or click the Open Icon.
2. Browse to the tutorials directory.
3. Change the ‘Files of type’ pull down to “Patran Neutral Files (*.neu *.ntl)
4. Select the file Exhaust-hanger.ntl
5. Click the [Open] button.
6. Choose ‘Meters’ in the Geometry Units window, click OK. The geometry should appear in the
graphics window
7. Choose File > Save As.
8. Save the model as Exhaust-hanger.tdf.
1.0.3
Assign Materials and Boundary Conditions
A solid model requires two parts in order to accurately produce a solution. The ‘surface’ part
contains shell geometry of the surface of the solid, and provides the surface conditions to the solid
(surface property for radiation, convection type). The ‘solid’ part contains the shell geometry as
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Solid Conduction Tutorial
well as all internal solid geometry, and provides the material type of the solid. All necessary
parameters will be set in this section.
1. Select the Editor > Parts Tab.
2. Select the pipe in the graphics window.
3. Make sure the Front tab is selected. Change the material to ‘Stainless Steel, 304’, and set the
thickness to 3mm.
4. Change the surface property to ‘Steel, As Received 0.74’.
5. Set the convection type to ‘H and Tfluid’. Change the H coefficient to 5 W/m2-K and the Fluid
Temperature to 20°C.
6. Select the Back tab. Change the surface property to ‘Exhaust 1.00’.
7. Set the convection type to ‘H and Tfluid’. Change the H coefficient to 100 W/m2-K and the Fluid
Temperature to 400°C.
8. Select the menu item Window > Clipping Plane.
9. Select the Enable Clipping Plane box at the top of the window and the Update graphics while
parameters are changing box at the bottom of the window. Notice that the solid volume shows
up gray without any mesh displayed.
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10. Translate the clipping plane along the Y axis to replicate the image shown below.
NOTE
You can invert the visible geometry with the Flip Visibility button.
11. Unselect the Draw Indicator box to turn off the display of the read clipping plane indicator.
12. Close the Clipping Plane Parameters window.
13. Select the exhaust hanger in the graphics window. Notice the diagram in the parts tab displaying a surface and a cube. The surface is highlighted green, which indicates that the selected
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geometry is a surface part for a solid. Also note that the front layer is named “Surface”, which
also indicates that the selected geometry is a surface part for a solid.
14. Change the surface condition to ‘Rubber, Hard 0.92’.
15. Set the convection type to ‘H and Tfluid’. Change the H coefficient to 5 W/m2-K and the Fluid
Temperature to 20°C.
16. Select Tools > Hide Selected, or click the Hide icon at the top of the page. Notice the geometry
changes to a dark gray color.
17. Click on the exhaust hanger part in the graphics window. The Editor tab now displays part
number 6, which is the solid portion of the hanger. Notice the figure in the parts tab (surface
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next to a cube). The cube is highlighted green, which indicates that the selected geometry is a
solid part (shown in the figure below).
18. Change the Material to ‘Rubber, Hard’.
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19. Click on the connector part.
20. Change the surface condition to ‘Steel, As Received 0.74’.
21. Set the convection type to ‘H and Tfluid’. Change the H coefficient to 5 W/m2-K and the Fluid
Temperature to 20°C.
22. Select Tools > Hide Selected, or click the Hide icon at the top of the page. Upon doing this the
connector geometry changes color from bright green to dark gray (if ‘Display Parts With Unique
Colors’ is turned off).
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23. Click on the connector part again (you are now selecting the solid part). Notice that the material is set to ‘Steel (mild)’. You do not need to change the material.
1.0.4
Running the Thermal Solution
Once the model setup is complete, the user is ready to complete the thermal solution. The thermal
solution will show the effects of the heat from the exhaust pipe, and how it affects the other parts
by conduction and radiation.
24. Go to the Analyze > Params tab and verify that the simulation is set to run for 0 minutes
(steady state solution).
25. Change {Tolerance Slope} radio button to {Tolerance}. Set the Tolerance value to .0001°C and
the maximum number of iterations to 1500.
NOTE
Volume elements usually require tighter convergence criteria than shell elements (depending on the specific
model). It is important to monitor the convergence plot (Analyze > Convergence tab) during the thermal
solution to ensure that the model is fully converging.
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26. Select the [Advanced] button. Set the Volume Solid Relaxation parameter to 1.95. This will allow
the solution to converge more quickly.
27. Click the [Run] button to begin the thermal solution. The view factor calculation and thermal
solution will only take a few minutes.
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28. If the Convergence Warning window appears when 1500 iterations are complete, click Accept
Solution. The Convergence Warning window may not appear, depending on the settings in the
Edit > Preferences > Convergence menu.
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29. Once the thermal solution has completed, go to the Post Process tab and verify that the Physical Temperature results look similar to the figure below. Change the temperature values on the
color scale, and click on the Smooth button to turn on smooth shading.
30. Click on various spots within the volume. Notice the selected volume element turns white, and
the internal temperatures are updated on the color bar and in the Post Process > Results tab.
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