SECTION 1 1 SECTION 1 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 20110615
2 Training Manual 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
SECTION 1 3 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/m 2 -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/m 2 -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. 20110615
4 Training Manual 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
SECTION 1 5 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 20110615
6 Training Manual 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.
SECTION 1 7 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/m 2 -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). 20110615
8 Training Manual 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.
SECTION 1 9 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. 20110615
10 Training Manual 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.
SECTION 1 11 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. 20110615
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