Ansys Icepak Tutorials

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ANSYS Icepak Tutorials

Release 14.0 ANSYS, Inc. November 2011 Southpointe 275 Technology Drive

Canonsburg, PA 15317 ANSYS, Inc. is

certified to ISO 9001:2008. [email protected] http://www.ansys.com (T) 724-746-3304 (F) 724-514-9494

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1. Using This Manual ... 1

1.1. What's In This Manual ... 1

1.2. How To Use This Manual ... 1

1.2.1. For the Beginner ... 1

1.2.2. For the Experienced User ... 1

1.3. Typographical Conventions Used In This Manual ... 1

1.4. Mouse Conventions Used In This Manual ... 2

1.5. When To Call Your ANSYS Icepak Support Engineer ... 2

2. Finned Heat Sink ... 3

2.1. Introduction ... 3

2.2. Prerequisites ... 3

2.3. Problem Description ... 3

2.4. Step 1: Create a New Project ... 4

2.5. Step 2: Build the Model ... 5

2.6. Step 3: Generate a Mesh ... 18

2.7. Step 4: Physical and Numerical Settings ... 23

2.8. Step 5: Save the Model ... 25

2.9. Step 6: Calculate a Solution ... 25

2.10. Step 7: Examine the Results ... 27

2.11. Step 8: Summary ... 35

2.12. Step 9: Additional Exercise ... 36

3. RF Amplifier ... 37

3.6. Step 3: Create Assemblies ... 53

3.12. Step 9: Summary ... 70

4. Use of Parameterization to Optimize Fan Location ... 71

4.6. Step 3: Creating Separately Meshed Assemblies ... 83

4.8. Step 5: Setting up the Multiple Trials ... 84

4.9. Step 6: Creating Monitor Points ... 86

4.10. Step 7: Physical and Numerical Setting ... 87

4.14. Step 11: Reports ... 93

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4.16. Step 13: Additional Exercise to Model Higher Altitude Effect ... 93

5. Cold-Plate Model with Non-Conformal Meshing ... 97

5.6. Step 3: Create a Separately Meshed Assembly ... 101

5.12. Step 9: Summary ... 106

6. Heat-Pipe Modeling and Nested Non-Conformal Meshing ... 107

6.6. Step 3: Create Nested Non-conformal Mesh Using Assemblies ... 113

6.12. Step 9: Summary ... 119

7. Non-Conformal Mesh ... 121

7.6. Step 3: Generate a Conformal Mesh ... 124

7.11. Step 8: Add an Assembly to the Model ... 127

7.12. Step 9: Generate a Non-conformal Mesh ... 129

7.16. Step 13: Summary ... 131

8. Mesh and Model Enhancement Exercise ... 133

8.1. Objective ... 133

8.3. Skills Covered ... 133

8.4. Training Method Used ... 133

8.5. Loading the Model ... 133

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8.7. Step-by-Step Approach ... 134

8.8. Modification 1: Non-Conformal Mesh of the Heat Sink and Components ... 135

8.9. Modification 2: Resolution of Thin Conducting Plate Intersecting Non-Conformal Region ... 137

8.10. Modification 3: Non-Conformal Mesh for the hi-flux-comps Cluster ... 137

8.11. Modification 4: A Super Assembly... ... 138

8.12. Modification 5: A Simplification Based on Magnitudes of Resistances... ... 140

8.13. Modification 6: A Classic Case for Thin Conducting Plate... ... 140

8.14. Conclusion ... 141

9. Loss Coefficient for a Hexa-Grille ... 143

9.6. Step 3: Define Parameters and Trials ... 146

9.12. Step 9: Summary ... 156

10. Inline or Staggered Heat Sink ... 157

10.6. Step 3: Define Design Variables ... 160

10.7. Step 4: Define Parametric Runs and Assign Primary Functions ... 162

10.11. Step 8: Define Monitor Points ... 166

10.14. Step 11: Summary ... 172

11. Minimizing Thermal Resistance ... 173

11.6. Step 3: Define Design Variables ... 175

11.10. Step 7: Define Primary, Compound, and Objective Functions ... 178

11.13. Step 10: Summary ... 182

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12.8. Step 5: Solving the Model Without Radiation ... 193

12.10. Step 7: Calculate a Solution- No Radiation ... 196

12.11. Step 8: Surface to Surface (S2S) Radiation Model ... 196

12.12. Step 9: Discrete Ordinates (DO) Radiation Model ... 197

12.13. Step 10: Ray Tracing Radiation Model ... 197

12.15. Step 12: Summary ... 200

13. Transient Simulation ... 201

13.10. Step 8: Generate a Summary Report ... 207

13.12. Step 10: Examine Transient Results in CFD Post ... 210

13.13. Step 10: Summary ... 215

14. Zoom-In Modeling in ANSYS Workbench ... 217

14.11. Step 8: Create a Zoom-In Model ... 224

14.12. Step 9: Edit the Zoom-in Model ... 226

14.13. Step 10: Mesh the Zoom-In Model ... 228

14.14. Step 11: Zoom-In Physical and Numerical Settings ... 229

14.15. Step 12: Examine the Zoom-in Results ... 229

14.16. Step 13: Summary ... 231

14.17. Step 14: Additional Exercise 1 ... 231

14.18. Step 15: Additional Exercise 2 ... 232

15. IDF Import ... 235

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15.6. Step 3: Component Filtration Alternatives ... 240

15.7. Step 4: Component Models Alternatives ... 241

15.8. Step 5: Summary ... 242

16. Modeling CAD Geometry ... 245

16.4. Step 1: Creating a New Project ... 246

16.11. Step 8: Summary ... 265

17. Trace Layer Import for Printed Circuit Boards ... 267

17.6. Conduction Only Model (PCB Without the Components) ... 276

17.8. Step 2: Set Physical and Numerical Values ... 277

17.12. PCB With the Actual Components Under Forced Convection ... 279

17.14. Step 2: Set Physical and Numerical Values ... 280

17.17. Using the Model Layers Separately Option ... 281

17.18. Summary ... 282 17.19. Additional Exercise 1 ... 282 17.20. Additional Exercise 2 ... 282 18. Joule/Trace Heating ... 283 18.1. Introduction ... 283 18.2. Prerequisites ... 283 18.3. Problem Description ... 283

18.11. Step 8: Summary ... 294

19. Microelectronics Packages - Compact models ... 295

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19.11. Step 8: Summary ... 310

20. Multi-Level Meshing ... 311

20.1. Objective ... 311

20.3. Skills Covered ... 311

20.4. Training Method Used ... 311

20.5. Loading the Model ... 311

20.6. Step-by-Step Approach ... 311

20.7. Modification 1: Multi-Level Meshing of the Fan_Guide ... 314

20.8. Modification 2: Multi-Level Mesh of the Sheetmetal_hs_assy.1 ... 315

20.9. Generate a Mesh ... 316

20.10. Conclusion ... 319

21. Characterizing a BGA-package by Utilizing ECAD Files ... 321

21.11. Step 8: Summary ... 329

22. Zero Slack with Non-Conformal Meshing ... 331

22.5. Step 2: Default Units ... 333

22.7. Step 4: Import Traces ... 333

22.8. Step 5: Add Slack Values ... 334

22.9. Step 6: Generate Mesh (with Slack Values) ... 335

22.10. Step 7: Zero Slack ... 336

22.11. Step 8: Generate Mesh (with Zero Slack) ... 337

22.16. Step 13: Summary ... 338

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23.10. Step 7: Examine the Results with CFD-Post ... 347

23.11. Step 8: Thermo-Mechanical Structural Analysis ... 349

23.12. Step 9: Summary ... 349

24. Postprocessing Using ANSYS CFD-Post ... 351

24.5. Step 2: Parametric Trials and Solver Settings ... 354

24.7. Step 4: Postprocessing Using ANSYS CFD-Post ... 355

24.8. Step 5: Comparison Study ... 378

24.9. Step 6: Summary ... 383

25. High Density Datacenter Cooling ... 385

25.5. Step 2: Set Preferences ... 387

25.8. Step 5: Create Monitor Points ... 413

25.13. Step 10: Additional Exercise: Visualize and analyze the results in ANSYS CFD-Post ... 424

25.14. Step 11: Summary ... 424

26. Design Modeler - Electronics ... 425

26.6. Step 3: Add Shortcuts to the Toolbar ... 427

26.7. Step 4: Edit the Model for ANSYS Icepak ... 428

26.8. Step 5: Opening the Model in ANSYS Icepak ... 445

26.9. Step 6: Summary ... 447

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1.1. What's In This Manual

This manual contains tutorials that teach you how to use ANSYS Icepak to solve different types of problems. In each tutorial, features related to problem setup and postprocessing are demonstrated.

The tutorial "Finned Heat Sink" provides detailed instructions designed to introduce the beginner to ANSYS Icepak. This tutorial provides explicit instructions for all steps in the problem setup, solution, and postprocessing. The remaining tutorials assume that you have read or solved the tutorial "Finned Heat Sink", or that you are already familiar with ANSYS Icepak and its interface. In these tutorials, some steps will not be shown explicitly. The input files are available in the installation area and available for download on the ANSYS Customer Portal.

1.2. How To Use This Manual

Depending on your familiarity with computational fluid dynamics and ANSYS Icepak, you can use this tutorial guide in a variety of ways:

1.2.1. For the Beginner

1.2.2. For the Experienced User

1.2.1. For the Beginner

If you are a beginning user of ANSYS Icepak, you should first read and solve the tutorial "Finned Heat Sink", in order to familiarize yourself with the interface and with basic setup and solution procedures. You may then want to try a tutorial that demonstrates features that you are going to use in your applic-ation. For example, if you are planning to solve a problem involving radiation, you should look at the tutorial "Radiation Modeling".

You may want to refer to other tutorials for instructions on using specific features, such as grouping objects, even if the problem solved in the tutorial is not of particular interest to you.

1.2.2. For the Experienced User

If you are an experienced ANSYS Icepak user, you can read and/or solve the tutorial(s) that demonstrate features that you are going to use in your application. For example, if you are planning to solve a problem involving radiation, you should look at the tutorial "Radiation Modeling".

You may want to refer to other tutorials for instructions on using specific features, such as grouping objects, even if the problem solved in the tutorial is not of particular interest to you.

1.3. Typographical Conventions Used In This Manual

Several typographical conventions are used in this manual's text to facilitate your learning process.

• Different type styles are used to indicate graphical user interface menu items and text inputs that you enter (e.g., Open project panel, enter the name projectname).

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• A mini flow chart is used to indicate the menu selections that lead you to a specific panel. For example,

Model

→

Generate mesh

indicates that the Generate mesh option can be selected from the Model menu at the top of the ANSYS Icepak main window.

The arrow points from a specific menu toward the item you should select from that menu.

• A mini flow chart is also used to indicate the list tree selections that lead you to a specific panel or operation. For example,

Problem setup

→

Basic parameters

indicates that the Basic parameters item can be selected from the Problem setup node in the Model manager window

• Pictures of toolbar buttons are also used to indicate the button that will lead you to a specific panel. For example, indicates that you will need to click on this button (in this case, to open the Walls panel) in the toolbar.

1.4. Mouse Conventions Used In This Manual

The default mouse buttons used to manipulate your model in the graphics window are described in Manipulating Graphics With the Mouse in the Icepak User's Guide. Although you can change the mouse controls in ANSYS Icepak to suit your preferences, this manual assumes that you are using the default settings for the mouse controls. If you change the default mouse controls, you will need to use the mouse buttons you have specified instead of the mouse buttons that the manual tells you to use.

1.5. When To Call Your ANSYS Icepak Support Engineer

The ANSYS Icepak support engineers can help you to plan your modeling projects and to overcome any difficulties you encounter while using ANSYS Icepak. If you encounter difficulties we invite you to call your support engineer for assistance. However, there are a few things that we encourage you to do before calling:

1. Read the section(s) of the manual containing information on the options you are trying to use. 2. Recall the exact steps you were following that led up to and caused the problem.

3. Write down the exact error message that appeared, if any.

4. For particularly difficult problems, package up the project in which the problem occurred (see Packing and Unpacking Model Files in the Icepak User's Guide for instructions) and send it to your support en-gineer. This is the best source that we can use to reproduce the problem and thereby help to identify the cause.

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2.1. Introduction

This tutorial demonstrates how to model a finned heat sink using ANSYS Icepak.

In this tutorial you will learn how to:

• Create a new project.

• Create blocks, openings, fans, sources, and plates. • Include effects of turbulence in the simulation. • Calculate a solution.

• Examine contours and vectors on object faces and on cross-sections of the model.

2.2. Prerequisites

This tutorial assumes that you have little to no experience with ANSYS Icepak and so each step will be explicitly described.

2.3. Problem Description

The cabinet contains an array of five high-power devices, a backing plate, ten fins, three fans, and a free opening, as shown in Figure 2.1 (p. 4). The fins and backing plate are constructed of extruded aluminum. Each fan has a total volume flow rate of 18 cfm and each source dissipates power at the rate of 33 W. According to the design objective, the base of the devices should not exceed 65°C when the fins are swept with air at an ambient temperature of 20°C.

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Figure 2.1 Problem Specification

2.4. Step 1: Create a New Project

1. Start ANSYS Icepak, as described in Starting ANSYS Icepak in the Icepak User's Guide.

When ANSYS Icepak starts, the Welcome to Icepak panel opens automatically.

2. Click New in the Welcome to Icepak panel to start a new ANSYS Icepak project.

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3. Specify a name for your project and click Create.

ANSYS Icepak creates a default cabinet with the dimensions 1 m

×

1 m

×

1 m, and displays the cabinet in the graphics window.

Note

You can rotate the cabinet around a central point using the left mouse button, or you can translate it to any point on the screen using the middle mouse button. You can zoom into and out from the cabinet using the right mouse button. To restore the cabinet to its default orientation, select Home position in the Orient menu.

2.5. Step 2: Build the Model

To build the model, you will first resize the cabinet to its proper size. Then you will create the backing plate and opening, followed by the elements that will be duplicated (i.e., the fans, fins, and devices).

1. Resize the default cabinet in the Cabinet panel.

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Extra

You can also open the Cabinet panel by selecting the Cabinet item in the Model manager window and then clicking the Edit object button ( ) in the Object modi-fication toolbar. Resizing of the cabinet object can also be done in the geometry window in the lower right hand corner of the GUI.

a. In the Cabinet panel, click the Geometry tab. b. Under Location, enter the following coordinates:

0.075 xE 0 xS 0.25 yE 0 yS 0.356 zE 0 zS

c. Click Done to resize the cabinet and close the panel.

d. In the Orient menu, select Scale to fit to scale the view of the cabinet to fit the graphics window.

Extra

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Extra

After selecting the object to be edited in the model tree, there are several ways you can open the Edit panel:

• Double-click on the object in the model tree, or – Type Ctrl+e, or

– Right-click the object in the model tree and scroll to Edit object, or – Click the Edit button in the object geometry window, or

– Click the Edit icon ( ) in the model toolbar.

2. Create the backing plate.

The backing plate is 0.006 m thick and divides the cabinet into two regions: the device side (where the high-power devices are contained in a housing) and the fin side (where the fins dissipate heat generated by the devices). The backing plate is represented in the model by a solid prism block.

Extra

Blocks allow six-sided control for meshing and thermal specifications, whereas plates allow for only two-sided control.

a. Click the Create blocks button ( ) to create a new block.

ANSYS Icepak creates a new solid prism block in the center of the cabinet. You need to change the size of the block.

b. Click the Edit object button ( ) to open the Blocks panel. c. Click the Geometry tab.

d. Enter the following coordinates for the block:

0.006 xE 0 xS 0.25 yE 0 yS 0.356 zE 0 zS

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e. Click Done to modify the block and close the panel. 3. Create the free opening on the fin side of the backing plate.

a. Click the Create openings button ( ) to create a new opening.

ANSYS Icepak creates a free rectangular opening lying in the x-y plane in the center of the cabinet. You need to change the size of the opening.

b. Click the Edit object button ( ) to open the Openings panel. c. Click the Geometry tab.

d. Enter the following coordinates for the opening:

0.075 xE 0.006 xS 0.25 yE 0 yS — zE 0.356 zS

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e. Click Done to modify the opening and close the panel. 4. Create the first fan.

Each fan is physically identical to the others, except with respect to its location on the cabinet wall. To create the set of three fans, you will build a single fan as a template, and then create two copies, each with a specified offset in the y direction.

a. Click the Create fans button ( ) to create a new fan.

ANSYS Icepak creates a free circular fan lying in the x - y plane in the center of the cabinet. You need to change the size of the fan and specify its mass flow rate.

b. Click the Edit object ( ) to open the Fans panel. c. Click the Geometry tab.

d. Enter the following coordinates for the fan:

0.04 xC 0.0475 yC 0 zC

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f. Click the Properties tab.

g. Keep the default Fan type of intake.

h. Under the Fan flow tab, select Fixed and Volumetric. Enter a volume flow rate of 18 cfm.

Note

Make sure to update the units to cfm by clicking on the triangle button and select-ing cfm from the drop-down list.

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i. Click Done to modify the fan and close the panel.

5. Copy the first fan (fan.1) to create the second and third fans (fan.1.1 and fan.1.2).

a. In the graphics display window, select fan.1 using the Shift key and right mouse button. b. In the object context menu, select Copy and the Copy fan fan.1 panel opens.

c. Enter 2 as the Number of copies.

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e. Click Apply.

ANSYS Icepak makes two copies of the original fan, each offset by 0.0775 m in the y direction from the previous one.

6. Create the first high-power device.

Like the fans, each device is physically identical to the others, except with respect to its location in the cabinet. To create the set of five devices, you will build a single rectangular planar source as a template, and then create four copies, each with a specified offset in the y direction.

a. Click the Create sources button ( ) to create a source.

ANSYS Icepak creates a free rectangular source in the center of the cabinet. You need to change the geometry and size of the source and specify its heat source parameters.

Note

For planar objects, select the desired plane first, then enter the coordinates.

b. Click the Edit object button ( ) to open the Sources panel. c. Click the Geometry tab.

d. Keep the default selection of Rectangular. e. In the Plane drop-down list, select Y-Z.

f. Enter the following coordinates for the source:

— xE 0 xS 0.0385 yE 0.0315 yS

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0.2005

zE

0.1805

zS

g. Click the Properties tab.

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i. Click Done to modify the source and close the panel.

7. Copy the first device (source.1) to create the other four devices (source.1.1, source.1.2, source.1.3, and source.1.4).

a. In the Model manager window, select the source.1 item under the Model node.

b. Click the Copy object button ( ).

c. Follow the same instructions that you used above to copy the fans, using a Y offset of 0.045 m to create 4 copies.

8. Create the first fin.

Like the fans and devices, each fin is physically identical to the others, except with respect to its location in the cabinet. To create the array of ten fins, you will build a single rectangular plate as a template, and then create nine copies, each with a specified offset in the y direction.

a. Click the Create plates button ( ) to create a plate.

ANSYS Icepak creates a free rectangular plate in the x-y plane in the center of the cabinet. You need to change the orientation and size of the plate and specify its thermal parameters.

b. Click the Edit object button ( ) to open the Plates panel. c. Click the Geometry tab.

d. In the Plane drop-down list, select X-Z. e. Enter the following coordinates for the plate:

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0.075 xE 0.006 xS — yE 0.0125 yS 0.331 zE 0.05 zS

f. Click the Properties tab.

g. Under Thermal model, select Conducting thick from the drop-down menu. h. Set the Thickness to 0.0025 m.

i. Keep default as the Solid material.

Note

Since the default solid material is extruded aluminum, you need not specify the material explicitly here.

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j. Click Done to modify the plate and close the panel.

9. Copy the first fin (plate.1) to create the other nine fins (plate.1.1, plate.1.2, ..., plate.1.9). a. In the Model manager window, select the plate.1 item under the Model node.

b. Click the Copy object button ( ).

c. Follow the same instructions that you used above to copy the fans, using a Y offset of 0.025 m to create 9 copies.

The completed model will look like Figure 2.2 (p. 17), which is shown in the Isometric view (available in the Orient menu or by clicking the Isometric view button ( )).

Note

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Figure 2.2 Completed Model for the Finned Heat Sink

10. Check the model to be sure that there are no problems (e.g., objects that are too close together to allow for proper mesh generation).

Model

→

Check model

Note

You can also click the Check model button ( ) to check the model.

Note

ANSYS Icepak should report in the Message window that 0 problems were found.

11. Check the definition of the modeling objects to ensure that you specified them properly.

View

→

Summary (HTML)

The HTML version of the summary displays in your web browser. The summary displays a list of all the objects in the model and all the parameters that have been set for each object. You can view the detailed version of the summary by clicking the appropriate object names or property specifications. If you notice any incorrect specifications, you can return to the appropriate modeling object panel and change the settings in the same way that you originally entered them.

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2.6. Step 3: Generate a Mesh

You will generate the mesh in two steps. First you will create a coarse mesh and examine it to determine where further mesh refinement is required. Then you will refine the mesh based on your observations of the coarse mesh.

Extra

For more information on how to refine a mesh locally, refer to Refining the Mesh Locally in the Icepak User's Guide.

Model

→

Generate mesh

Extra

You can also generate a mesh by clicking the Generate mesh button ( ), which opens the Mesh control panel.

1. Generate a coarse (minimum-count) mesh.

a. In the Mesh control panel, select Coarse in the Mesh parameters drop-down list.

ANSYS Icepak updates the panel with the default meshing parameters for a coarse (minimum-count) mesh, shown in the panel below.

b. Set the Mesh units and all the Minimum gap units to mm. c. Set the Minimum gap to 1 mm for X, Y, and Z.

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e. Click the Generate button to generate the coarse mesh.

Note

If the Allow minimum gap changes option is unchecked under the Misc tab, ANSYS Icepak will inform you that your minimum object separation is more than 10% of the smallest size object in the model . You can stop the meshing process, ignore the warning, or allow ANSYS Icepak to correct the values.

f. If this warning appears, click Change value and mesh in the Minimum separation in x and Minimum separation in y panels to accept the recommended changes to your model and con-tinue generating the mesh.

2. Examine the coarse mesh on a cross-section of the model. a. Click the Display tab.

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b. Turn on the Cut plane option.

c. In the Set position drop-down list, select X plane through center. d. Turn on the Display mesh option.

The mesh display plane is perpendicular to the fins, and aligned with the devices, as shown in Figure 2.3 (p. 21).

Note

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Figure 2.3 Coarse Mesh on the y-z Plane

e. Use the slider bar to move the plane cut through the model. See Figure 2.4 (p. 22) to examine a close-up view of the coarse mesh.

Note

You can change the mesh color using the Surface mesh color and the Plane mesh color options.

The mesh elements near the fins are too large to sufficiently resolve the problem physics. In the next step, you will generate a finer mesh.

3. Generate a finer mesh. a. Click the Settings tab.

b. Under Global, select Normal in the Mesh parameters drop-down list.

ANSYS Icepak updates the panel with the default meshing parameters and Minimum gap values for a “normal" (i.e., finer than coarse) mesh.

4. Click the Generate button in the Mesh control panel to generate the finer mesh. 5. Examine the new mesh.

The graphics display updates automatically to show the new mesh. Click the Display tab and use slider bar to advance the plane cut and view the mesh throughout the model.

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Figure 2.4 Fine and Coarse Mesh on the y-z Plane

6. Turn off the mesh display.

a. Click the Display tab in the Mesh control panel. b. Deselect the Display mesh option.

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Note

After deselecting the Display mesh option and closing the Mesh control panel, you can display the mesh on selected objects by using the context menu in the graphics display window. To display the context menu, hold down the Shift key and press the right mouse button anywhere in the graphics window, but not on an object. Select Display mesh and select the object you want it displayed on.

Figure 2.5 Display mesh option

2.7. Step 4: Physical and Numerical Settings

Before starting the solver, you will first review estimates of the Reynolds and Peclet numbers to check that the proper flow regime is being modeled.

1. Check the values of the Reynolds and Peclet numbers.

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a. Click the Reset button. Reset calculates the Reynolds and Peclet numbers. b. Check the values printed to the Message window.

The Reynolds and Peclet numbers are approximately 13,000 and 9,000, respectively, so the flow is turbulent. ANSYS Icepak will recommend setting the flow regime to turbulent.

Note

These values are only estimates, based on the current model setup. Actual values may vary, and may need to be verified, depending on your design.

c. Click Accept to save the solver settings. 2. Enable turbulence modeling.

Problem setup

→

Basic parameters

a. In the Basic parameters panel, select Turbulent as the Flow regime. b. Keep the default Zero equation turbulence model.

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b. Click Accept to save the new settings.

2.8. Step 5: Save the Model

ANSYS Icepak automatically saves the model for you before it starts the calculation, but it is a good idea to save the model (including the mesh) yourself as well. If you exit ANSYS Icepak before you start the calculation, you will be able to open the job you saved and continue your analysis in a future ANSYS Icepak session. (If you start the calculation in the current ANSYS Icepak session, ANSYS Icepak will simply overwrite your job file when it saves the model.)

File

→

Save project

Note

Alternatively, you can click the button in the File commands toolbar.

2.9. Step 6: Calculate a Solution

1. Start the calculation.

Solve

→

Run solution

Note

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2. Keep the default settings in the Solve panel. 3. Click Start solution to start the solver.

Note

There are no universal metrics for judging convergence, a good indicator is when the solution no longer changes with more iterations and when the residuals have decreased to a certain degree. The default criterion is that each residual will be reduced to a value of less than − except the energy residual, for which the default criterion is −

. It is a good idea to judge convergence not only by examining residuals levels, but also by monitoring relevant integrated quantities.

ANSYS Icepak begins to calculate a solution for the model, and a separate window opens where the solver prints the numerical values of the residuals. ANSYS Icepak also opens the Solution re-siduals graphics display and control window, where it displays the convergence history for the calculation.

Upon completion of the calculation, your residual plot will look something like Figure 2.6 (p. 27). You can zoom in the residual plot by using the left mouse.

Note

The actual values of the residuals may differ slightly on different machines, so your plot may not look exactly the same as Figure 2.6 (p. 27).

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Figure 2.6 Residuals

4. Click Done in the Solution residuals window to close it.

2.10. Step 7: Examine the Results

ANSYS Icepak provides a number of ways to view and examine the solution results, including:

• plane-cut views • object-face views

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Note

The objective of this exercise is to determine whether the air flow and heat transfer associated with the heat sink (fans and fins) are sufficient to maintain device temperatures below 65°C. You can accomplish this by creating different plane cuts and monitoring the velocity vector and temperature on it. Plane-cut views allow you to observe the variation in a solution variable across the surface of a plane.

You will use the Plane cut panel to view the direction and magnitude of velocity across a horizontal plane.

1. To open the Plane cut panel, select Plane cut in the Post menu.

Extra

You can also open the Plane cut panel by clicking the Plane cut button ( ).

2. Display velocity vectors on a plane cut on the fin side of the enclosure.

Post

→

Plane cut

a. In the Name field, enter the name cut-velocity.

b. In the Set position drop-down list, select X plane through center.

Tip

Click the triangle button located next to the Set position text field to open the drop-down list.

c. Turn on the Show vectors option.

d. Click Create.

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This orients the model as shown in Figure 2.7 (p. 29). You can see that the maximum velocity occurs at the fan blades. The lowest velocity occurs between the top fin and the adjacent cabinet wall, and between the bottom fin and the adjacent cabinet wall.

Extra

You can also select the positive orientation by clicking the Orient positive X button ( ).

Figure 2.7 Velocity Vectors on the Fin Side of the Enclosure

f. In the Plane cut panel, turn off the Active option.

This temporarily removes the velocity vector display from the graphics window, so that you can more easily view the next postprocessing object.

Note

You can later open the Inactive folder in the model tree and locate cut_velo-city.cut_velocity can be either deleted or reactivated by dragging it to Trash or to the Post-processing folder, as well as with the right-click dialog.

3. Display contours of temperature on the fin side of the enclosure. a. Click New in the Plane cut panel.

b. In the Name field, enter the name cut-temperature.

c. In the Set position drop-down list, select X plane through center. d. Turn on the Show contours option and click Parameters.

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e. Keep the default selection of Temperature.

f. For Shading options, keep the default selection of Banded.

g. For Color levels, select Calculated and then select This object from the drop-down list. h. Click Apply.

ANSYS Icepak computes the color range for the display based on the range of temperatures on this plane cut.

i. Click Done to save the new settings, close the panel, and update the graphics display.

The graphics display updates to show the temperature contour plot. The actual values of temperature may slightly differ on different systems. You can use the scroll bar to change the x-location of the plane cut. In addition, the plane cut can be dragged through the model when you press the Shift key and hold down the middle mouse button on the plane. Ensure you click the edge of the plane cut so as to not move any objects.

Figure 2.8 (p. 31) shows that heat conducts through the fins from the sources in both direc-tions.

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Figure 2.8 Temperature Contours on the Fin Side of the Enclosure

j. In the Plane cut panel, turn off the Active option.

4. Display velocity vectors superimposed with pressure contours. a. Click New in the Plane cut panel.

b. In the Name field, enter the name cut-prvelocity.

c. In the Set position drop-down list, select X plane through center. d. Specify the display of velocity vectors.

i. Turn on the Show vectors option and click Parameters.

The Plane cut vectors panel opens.

ii. Select Fixed from the Color by drop-down list.

iii. Click on the square next to Fixed color and select black from the color palette. iv. Click Done to close the panel.

e. Specify the display of contours of pressure.

i. Turn on the Show contours option and click Parameters.

The Plane cut contours panel opens.

ii. In the Plane cut contours panel, select Pressure in the Contours of drop-down list. iii. For Shading options, keep the default selection of Banded.

iv. For Color levels, select Calculated and then select This object from the drop-down list. v. Click Done to save the new settings, close the panel, and update the graphics display.

The graphics display updates to show the pressure contour plot superimposed on the velocity vector plot.

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Figure 2.9 (p. 32) shows isolated regions of high pressure immediately downstream of the fans, including local maxima at the upstream tips of the fins.

Figure 2.9 Pressure Contours and Velocity Vectors on the Fin Side of the Enclosure

f. In the Plane cut panel, turn off the Active option.

5. Display contours of temperature on all five high-power devices.

An object-face view allows you to examine the distribution of a solution variable on one or more faces of an object in the model. To generate an object-face view, you must select the object and specify both the variable to be displayed (e.g., temperature) and the attributes of the view (e.g., shading type).

You will use the Object face panel to create a solid-band object-face view of temperature on all five high-power devices and on the backing plate.

a. To open the Object face panel, select Object face in the Post menu.

Post

→

Object face

Extra

You can also open the Object face panel by clicking the Object face button ( ).

b. In the Name field, enter the name face-tempsource.

c. In the Object drop-down list, click source.1, hold down the Shift key, and click source.1.4 to select all the sources, and click the Accept button.

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e. Click Parameters next to the Show contours option.

The Object face contours panel opens.

f. In the Object face contours panel, keep the default selection of Temperature in the Contours of drop-down list.

g. For Shading options, keep the default selection of Banded.

h. For Color levels, select Calculated and then select This object from the drop-down list.

The graphics display updates to show the temperature contours on the sources. j. Use your right mouse button to zoom in and look more closely at each source.

Figure 2.10 (p. 34) shows a view with the temperature contours on all five sources. The perature distributions are similar for all sources: warm in the center and decreasing in

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tem-perature toward the edges of the source. Temtem-perature distributions on the top and bottom sources are similar to each other, as are distributions on the two remaining sources.

Note

To view the temperature contours on an individual source, hold down the Shift key and drag a box around a source object using the left mouse button. The source object will show as highlighted in the Model manager window. Right click the source object to display the context menu and select Create>Object

face(s)>Separate. The Object face panel is displayed for that particular object. Change the settings to match the ones used above for all source objects and click Create.

Figure 2.10 Temperature Contours on the Five Devices

k. In the Object face panel, turn off the Active option. 6. Display line contours of temperature on the backing plate.

a. Click New in the Object face panel.

b. In the Name field, enter the name face-tempblock. c. In the Object drop-down list, select block.1 and click Accept. d. Turn on the Show contours option and click Parameters.

The Object face contours panel opens.

e. In the Object face contours panel, keep the default selection of Temperature in the Contours of drop-down list.

f. For Contour options, deselect Solid fill and select Line.

g. For Level spacing, select Fixed and set the Number of contour lines to 200.

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The graphics display updates to show the temperature contours on the block.Figure 2.11 (p. 35) shows that most of the heat is confined to the region near the sources. The maximum temperature occurs near the middle three sources.

Figure 2.11 Temperature Contours on the Backing Plate

j. Click Done in the Object face panel to close the panel. 7. Save the post-processing objects created.

a. Select Save post objects to file in the Post menu. b. Click on Save in the File selection window that opens.

Upon saving the project, all objects created during post-processing are saved within a post_objects file for future retrieval.

Note

ANSYS Icepak does not automatically save the post-processing objects created in the current session. When you exit ANSYS Icepak, they are deleted unless they are saved using the above steps.

2.11. Step 8: Summary

In this tutorial, you set up and solved a model in order to determine the ability of the specified heat sink to maintain source temperatures below 65 °C. Postprocessing results show that the maximum source temperature is about 60 °C, indicating that the heat sink provides adequate cooling for the sources.

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2.12. Step 9: Additional Exercise

To determine the effectiveness of the heat sink under conditions involving the failure of the middle fan, deactivate or edit fan.1.1, go to the Properties tab and turn on Failed under the Options tab, assign a free-area ratio of 0.3, and click Done. Next, remesh the model, solve it again using a different solution ID, and examine the new results.

Note

When you are finished examining the results, you can end the ANSYS Icepak session by clicking Quit in the File menu.

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3.1. Introduction

This tutorial demonstrates how to model an RF Amplifier using ANSYS Icepak.

In this tutorial you will learn how to:

• Create a new project.

• Create openings, fans, sources, enclosure, PCB, heat sink and walls. • Use non-conformal meshing.

• Include effects of gravity and turbulence in the simulation. • Calculate a solution.

• Examine contours and vectors on object faces and on cross-sections of the model.

3.2. Prerequisites

This tutorial assumes that you have little experience with ANSYS Icepak, but that you are generally fa-miliar with the interface. If you are not, please review Sample Session in the Icepak User's Guide.

3.3. Problem Description

RF Amplifiers are typically sealed enclosures that are placed within larger systems. They present a challenge from the thermal management perspective because no direct exchange of air exists between the interior of the amplifier and the ambient. The common method of cooling such subsystems is to mount a large heat sink on the amplifier housing that cools all the devices within the enclosure. A simplified version of an RF amplifier (Figure 3.1 (p. 38)) will serve as the model for this tutorial. There will be free convection inside the amplifier and forced convection in the external domain.

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Figure 3.1 Schematic of the RF Amplifier

3.4. Step 1: Create a New Project

1. Start ANSYS Icepak, as described in Chapter 1 of the User's Guide.

When ANSYS Icepak starts, the Welcome to Icepak panel opens automatically.

2. Click New in the Welcome to Icepak panel to start a new ANSYS Icepak project.

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3. Specify the name amplifier for your project and click Create.

ANSYS Icepak creates a default cabinet with the dimensions 1 m

×

1 m

×

1 m, and displays the cabinet in the graphics window.

Note

You can rotate the cabinet around a central point using the left mouse button, or you can translate it to any point on the screen using the middle mouse button. You can zoom into and out from the cabinet using the right mouse button. To restore the cabinet to its default orientation, select Home position in the Orient menu.

3.5. Step 2: Build the Model

To build the model, you will first resize the cabinet to its proper size. Then you will create the amplifier housing, devices (heat sources), PCB, heatsink, fan and other geometrical objects.

1. Resize the default cabinet and create an opening on one side of the cabinet.

Model

→

Cabinet

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Extra

After selecting the object to be edited in the model tree, there are several ways you can open the Edit panel:

• Double-click on the object in the model tree, or – Type Ctrl+e, or

– Right-click the object in the model tree and scroll to Edit object, or – Click the Edit button in the object geometry window, or

– Click the Edit object icon ( ) in the model toolbar

Figure 3.2 The Cabinet Geometry Tab Panel

One side of this cabinet has an opening. Assign Properties on this boundary, in the Properties tab of the Cabinet object panel (Figure 3.3 (p. 41)):

a. Change the Max y Wall type to be an Opening. b. Click Done to accept the inputs and close the panel.

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Figure 3.3 The Cabinet Boundary Panel

2. Create the Y and Z faces of the amplifier housing as an enclosure using the enclosure object.

Click on the Create enclosures icon ( ) in the model toolbar, then specify the following Name and dimensions:

In the Properties tab specify the followings:

a. Change the Boundary type to Open for Min X and Max X. For others, retain the boundary type as Thin.

b. Specify the Solid material as Polystyrene-rigid-R12.

Tip

You have to scroll down the list to find this material.

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Figure 3.4 The Enclosure Panel

3. Create the Xmin face of the amplifier housing as a wall.

The wall covers the Xmin side of the enclosure.

4. Click on the Create walls icon ( ) in the model toolbar to create a new wall.

In the object edit window, name the wall Xmin and change the plane to Y-Z.

Note

While we will use the align tools to place the wall at the desired locations, we could also specify the dimensions/locations of the wall in the Geometry tab and achieve the same result. However, the align tools are faster, and thus are the recommended

method.

To start the process, left-click Morph Edges icon ( ) in the model toolbar. Now, follow the step-by-step procedure described below:

a. Select the Zmax edge of the wall (Figure 3.5 (p. 43)) by left mouse clicking it in the graphical window. Notice that it turns red to indicate that it has been selected.

b. Click the middle mouse button to accept this edge.

c. Select the lower Zmax edge of the enclosure (Figure 3.5 (p. 43)) with the left mouse button. Notice that it turns yellow to indicate that it has been selected.

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Figure 3.5 Schematic Showing Edge Identities for Alignment

d. Click the middle mouse button to accept the transformation. The wall Xmin should have now been moved and resized. Now the wall should extend to the entire Xmin side of the enclosure.

To specify the remaining wall dimension, stay in the match edge mode and complete the following steps:

a. Click the Zmin edge of the wall with the left mouse button. Be sure that it (and not the enclosure edge) is highlighted in red. By repeatedly clicking the left mouse button, ANSYS Icepak cycles through all possible edges.

b. Click the middle mouse button to accept.

c. Using the left mouse button, click the lower Zmin edge of the enclosure.

d. Click the middle mouse button to accept. The wall should now form the Xmin face of the enclosure. e. Click the right mouse button to exit the Match edge mode.

The resulting model is shown in Figure 3.6 (p. 44) with shading to highlight new definitions. Shading is available under the Info tab in most panels.

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Figure 3.6 Geometry with Wall

Double-click on the newly created wall object (Xmin) in the model tree to open the Walls panel. Now specify the following properties to the wall in the Properties tab.

a. Specify a Wall thickness of 1 mm (0.001 m).

b. Specify the Solid material as Polystyrene-rigid-R12 under Plastics.

c. Specify the External conditions as Heat transfer coefficient and click the Edit button.

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i. Select Heat transfer coefficient in the External conditions drop-down list and press Edit. The Wall external thermal conditions panel opens.

ii. Set the Heat transfer coeff to 5 W/K- .

iii. Click Done to close the Wall external thermal conditions panel. iv. Click Done to close Walls panel (Figure 3.7 (p. 45))

Figure 3.7 The Walls Panel

5. Create the PCB.

The PCB will cover the Xmax side of the enclosure.

a. Click on the Create printed circuit boards icon ( ) in the Model toolbar to create a PCB and double click on the PCB object in the Model tree.

b. Specify the following in the geometry window:

c. Specify the Trace layer type as Detailed and input the parameters under Trace layer parameters (make sure that you enter both columns) in the Properties tab as shown in Figure 3.8 (p. 46). There are four internal layers.

Please notice that the Effective conductivity in plane and normal directions are updated when you click on the Update button (Figure 3.8 (p. 46)).

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Figure 3.8 The Printed circuit boards Panel

d. Click Done to close the Printed circuit boards panel. 6. Create the devices as 2D sources.

There are 12 devices on the bottom side of the PCB. Theses devices are created as 2D sources. The following steps show you how to create one and then use the copy utility to create the re-maining 11 sources.

a. Click on the Create sources icon ( ) in the model toolbar to create a source and double click on the source object in the model tree.

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c. In the Properties tab, specify the Total power as 7 W (Figure 3.9 (p. 47)) and click Done.

Figure 3.9 The Sources Panel

d. Create the other devices (sources) object by creating two copies of the device and translating it to z= 0.055 m. Please follow the steps below for copying the source object.

i. Right mouse click on the source object and choose the Copy option. ii. Specify the Number of copies as 2.

iii. Turn on the Translate option. iv. Specify the Z offset to 0.055 m. v. Click Apply to copy the object.

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Figure 3.10 The Copy source device Panel

e. Similarly, create the other devices (sources) object by copying the sources created in the previous steps.

i. Left mouse click and select device, then while holding down the Ctrl key, select device.1, and device.2. Right mouse click and choose the Copy option.

ii. Specify the Number of copies as 3. iii. Turn on the Translate option. iv. Specify the Y offset to 0.064 m. v. Click Apply to copy the object.

Note

Following these two copy actions, you should now have 12 sources (Figure 3.11 (p. 49)) in a four rows by three columns pattern.

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Figure 3.11 Geometry with Devices

7. Create the heat sink.

The extruded fin heat sink with the flow in the y direction will be created to remove the heat from the PCB.

a. Click on the Create heat sinks icon ( ) in the Model toolbar to create a heat sink and double click on the heat sink object in the model tree. Specify the following dimensions in the geometry window.

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b. In the heat sink object panel, select the Geometry tab, and specify a Base height of 0.004 m and an Overall height of 0.04 m.

c. Specify the properties of the heat sink as shown in Figure 3.12 (p. 50) below. Note that we are not changing parameters in the Flow/thermal data, Pressure loss, or Interface tabs.

Figure 3.12 The Heat sinks Panel

d. Click Done to close the Heat sinks panel. 8. Create the fan.

For this model, we will make use of ANSYS Icepak's fan library and search tool. a. Select the Library tab in the model manager window(Figure 3.13 (p. 51)). b. Right-click on Libraries in the model tree and choose Search fans.

The Search fan library dialog appears.

i. In the Physical tab, deactivate the Min fan size and enter 80 mm for the Max fan size. ii. Select the Thermal/flow tab, enable the Min flow rate option and specify a Min flow rate

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Note

The minimum flow rate used in the search criteria implies the minimum free flow of the fans.

iii. Click on the Search button.

Note

ANSYS Icepak lists all the fans in its libraries that satisfy these conditions.

c. Select the fan called delta.FFB0812_24EHE in the Name column by clicking on it with the left mouse button.

d. Click Create to load the fan into the model.

Figure 3.13 Search Fan library Panel

e. Now, we need to specify the location of the fan created in the previous steps. Resize the fan geometry based on the Figure 3.14 (p. 52) (note X-Z plane).

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Figure 3.14 The Fans Panel

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Figure 3.15 The Final Geometry

f. Check the definition of the modeling objects to ensure that you specified them properly.

View

→

Summary (HTML)

Note

The HTML version of the summary displays in your web browser. The summary displays a list of all the objects in the model and all the parameters that have been set for each object. You can view the detailed version of the summary by clicking the appropriate object names or property specifications. If you notice any incorrect specifications, you can return to the appropriate modeling object panel and change the settings in the same way that you originally entered them.

3.6. Step 3: Create Assemblies

For both organizational purposes and to have a finer mesh in the fan and enclosure, we will create two assemblies. The first assembly will consist of the RF amplifier and heat sink; the second assembly will consist only of the fan.

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1. To create the amplifier assembly:

a. Select the positive X view by either using the icon in the shortcut menu or simply press Shift+X and then Shift+S to fit to scale the view in the graphics window.

b. While pressing Shift, drag a bounding box around the amplifier using the left mouse button. Re-lease the mouse button and notice that all of the objects forming the amplifier and heat sink have been selected in the model tree.

c. Right-click on the highlighted enclosure (Housing) in the model tree and select Create and then Assembly from the list. All of the selected objects have now been added to the assembly. d. In the Object geometry window, rename the assembly “assembly.1" to amplifier and click

Apply.

2. Create a new assembly for the fan object:

a. Click on the Create assemblies icon ( ) in the model toolbar to create a new assembly.

b. In the Model tree, use the left mouse button to drag the fan,delta.FFB0812_24EHE, into the new assembly to add it to this assembly.

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Figure 3.16 Two Assemblies

3.7. Step 4: Generate a Mesh

Before generating a mesh, we will specify the slack values for the assemblies. Slack values represent a finite offset from an object to a non-conformal mesh boundary and are required when meshing assem-blies separately.

1. Edit both assemblies (right-click the assembly name in the model toolbar and select Edit), then select the Meshing tab.

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2. Toggle on Mesh separately and then specify the slack values indicated in the following table. Make sure you remember to add slack values to both assemblies.

Table 3.1 Slack Values for the Amplifier and Fan

Max Z Max Y Max X Min Z Min Y Min X Name 0.01 0.05 0 0.01 0.02 0 Amplifier 0.01 0.05 0.01 0.01 0 0.01 Fan

Figure 3.17 Fan Assemblies Panel

3. To create the mesh, go to Model

→

Generate Mesh. The Mesh control panel (Figure 3.18 (p. 57)) appears. The Mesh control panel can also be opened by clicking on the Generate mesh icon ( ) in the shortcut menu.

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Figure 3.18 The Mesh control Panel

4. As a first step, generate a coarse mesh by choosing Coarse in the Mesh parameters drop-down list in the Global tab, as shown in Figure 3.18 (p. 57). Click Generate to create a mesh.

Note

If you have unchecked Allow minimum gap changes in the Misc tab, the Minimum separation warning will appear. This warning message appears when the minimum gap specified is more than 10% of the smallest sized object in the model. Please select Change value and mesh if the warning message pops up.

5. To view the mesh, display a plane-cut view through the center of the cabinet, perpendicular to the fins (y-z plane).

6. To create a plane-cut, follow these steps:

a. Click on the Display tab at the top of the Mesh control panel. b. Toggle on Display mesh and Cut plane.

c. Under Plane location, set position to X plane through center in the drop-down list. d. Press Shift+X to orient to the positive X direction and view the newly created plane cut. e. Move the plane using the slider bar to see different views.

Make sure that the amplifier assembly is expanded and inspect the cells adjacent to the heat sink fins. Notice that the resolution is coarse (Figure 3.19 (p. 58)), with only a couple of cells between fins. As flow passes between the fins, boundary layers will grow and their degree of resolution