Tutorial for Assignment #3 Heat Transfer Analysis By ANSYS (Mechanical APDL) V.13.0

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1 Tutorial for Assignment #3 Heat Transfer Analysis By ANSYS (Mechanical APDL) V Problem Description This exercise consists of an analysis of an electronics component cooling design using fins: All electronic components generate heat during the course of their operation. To ensure optimal working of the component, the generated heat needs to be removed. This is done by attaching fins to the device which aid in rapid heat removal to the surroundings. For the sake of simplicity, we ll assume that the electronic circuit is made of copper with thermal conductivity of 386 W/mºK and that it generates heat at the rate of 1 W. The enclosing container is made of a steel with thermal conductivity of 17 W/mºK. The fins are made of aluminum with thermal conductivity of 180 W/mºK. There is convection along all the boundaries except the bottom, which is insulated. The film (convection) coefficient is h=50 W/m2ºK and the ambient temperature is 20ºC. Figure 1: Problem geometry 1.1 OBJECTIVE: Determine an optimal number of fins to use on the component. Cases considered should all use an odd number of fins (3, 5, 7, ). By: Majid Soleimaninia Page 1

2 1.2 Deliverables: A hardcopy submission that includes: 1. A plot of the temperature distribution in the component for the baseline case of 3 cooling fins and for your recommended number of fins. 2. A plot generated using Matlab that shows the reduction of the maximum temperature in the component as a function of the number of fins. Students are encouraged to collaborate with each other by distributing the tasks of modeling the specific cases (each case differing in only the number of fins used). Submissions must be prepared individually. 2 Start ANSYS (Mechanical APDL) V.13.0 Begin ANSYS (Mechanical APDL) with Start All Programs ANSYS 13.0 Mechanical APDL (ANSYS). That will bring you to the main ANSYS Utility Menu as seen in Figure 2. Figure 2: Opening ANSYS to the Utility Menu and graphics window. By: Majid Soleimaninia Page 2

3 3 Preprocessing: Defining the Problem 3.1 Select job name and analysis type The various menus below will sometimes get moved to a back (hidden) window. If you think that has occurred hit the Raise Hidden button,. You will always need a job name: 1. Utility Menu File Change Jobname. 2. Change_Jobname, type in the new name, OK (as seen in Figure 3). Figure 3: Setting the new job name. The ANSYS file sizes for real engineering problems get to be quite large, so have a directory dedicated to ANSYS: 1. Utility Menu File Change Directory. 2. Browse for Folder Change Working Directory, pick your directory (ANSYS Tutorial_P5-70 in Figure 4), OK. By: Majid Soleimaninia Page 3

4 Figure 4: Establish a directory for the analysis files. To keep up with your analysis studies over time create descriptive titles: 1. Utility Menu File Change Title. 2. Change Title, enter a descriptive title, OK (see Figure 5). Figure 5: Provide a descriptive title. By: Majid Soleimaninia Page 4

5 3.2 Element type data As in the conduction example, we will use PLANE55 (Thermal Solid, Quad 4node 55). This element can be used as a plane element or as an axisymmetric ring element with a 2-D thermal conduction capability. The element has four nodes with a single degree of freedom, temperature, at each node. The element is applicable to a 2-D, steady-state or transient thermal analysis. The element can also compensate for mass transport heat flow from a constant velocity field. 1. Main Menu Preferences Preferences for GUI Filtering. 2. Check Thermal, accept default h-method, OK, as in Figure 6. (This is a thermal Problem) Figure 6: Declare the selection of a thermal analysis. 3. Main Menu Preprocessor Element Type Add/Edit/Delete, as in Figure In Element Types, seen in Figure 7, pick Add Library of Element Types. 5. Select (Thermal Mass) Solid and Quad 4 node 55 (that is, PLANE55), OK. 6. In Element Types window, select PLANE55 element and then pick Options to modify your PLANE55 element type options, as in Figure In Element Types pick Close. By: Majid Soleimaninia Page 5

6 Figure 7: Select Thermal Solid, Quad 4node 55 (PLANE55) element type. Figure 8: Modify PLANE55 element type options. 3.3 Define member material properties Here you will use the simplest thermal, isotropic, 1D material description. ANSYS has full anisotropic (completely directionally dependent), as well as non-linear material constitutive laws. We need to define three different materials (Copper, Aluminum and Steel). At first we are defining Copper then Aluminum and at the end, Steel. Activate the material properties with: By: Majid Soleimaninia Page 6

7 1. Main Menu Preprocessor Material Props Material Models. 2. Material Model Number 1 appears in Define Material Model Behavior. 3. Double click on Thermal, then Conductivity, then Isotropic. 4. In Conductivity for Material Number 1 enter (W/mm o K) for thermal conductivity, KXX, for Copper, as in Figure 9, OK. 5. Close (X) the Define Material Model Behavior window. Figure 9: Define material properties for Copper. Activate the material properties for Aluminum with: 1. Main Menu Preprocessor Material Props Material Models. 2. Click Material New Models in Define Material Model Behavior. 3. In Define Material ID enter 2 for new material, Aluminum, OK, as in Figure Material Model Number 2 appears in Define Material Model Behavior, Select it. 5. Click on Thermal, then Conductivity, then Isotropic. 6. In Conductivity for Material Number 1 enter 0.18 (W/mm o K) for thermal conductivity, KXX, for Aluminum, as in Figure 11, OK. 7. Close (X) the Define Material Model Behavior window. By: Majid Soleimaninia Page 7

8 Figure 10: Define the new material model in list. Figure 11: Define material properties for Aluminum. To activate the material properties for Steel, again: 1. Main Menu Preprocessor Material Props Material Models. 2. Click Material New Models in Define Material Model Behavior. 3. In Define Material ID enter 3 for new material, Steel, OK, as in Figure Material Model Number 3 appears in Define Material Model Behavior, Select it. 5. Click on Thermal, then Conductivity, then Isotropic. 6. In Conductivity for Material Number 1 enter (W/mm o K) for thermal conductivity, KXX, for Steel, as in Figure 11, OK. 7. Close (X) the Define Material Model Behavior window. By: Majid Soleimaninia Page 8

9 Figure 12: Define the new material model in list. Figure 13: Define material properties for Steel. 3.4 Create Geometry Of course, ANSYS has powerful mesh generation capabilities. However, for beginners or small problems with only a few nodes you can type in the coordinates, or make your domain by areas, or use cursor input via the graphics window, or read them from a file. Use the second approach: 1. Main Menu Preprocessor Modeling Create Areas Rectangle By 2 Corners. 2. In Rectangle by 2 Corners of Figure 14 enter coordinates of your main big rectangular area (A1), WP X = 0, WP Y = 0, Width = 50, Height = 50 (mm), OK. 3. If you make a mistake you can return and correct it with Main Menu Preprocessor Modeling Move/Modify Areas Areas, or delete it with Main Menu Preprocessor Modeling Delete Areas Only. By: Majid Soleimaninia Page 9

10 Now, plot the geometry by area number: 1. Utility Menu PlotCtrls Numbering. 2. In Plot Numbering Controls check Area numbers, OK. 3. Utility Menu PlotCtrls Numbers and review the plot that is similar to Figure To get the reverse video white background of that figure use PlotCtrls Style Color Reverse Video. Figure 14: Build the main area To make two other small rectangular areas in top of our domain which we should subtract them from the main domain, you can do the same procedure; 1. Main Menu Preprocessor Modeling Create Areas Rectangle By 2 Corners. 2. In Rectangle by 2 Corners of Figure 15 enter coordinates of small rectangular area (A2), WP X = 10, WP Y = 40, Width = 10, Height = 10 (mm), OK. By: Majid Soleimaninia Page 10

11 Figure 15: Build the small areas. Also for the other one; 1. Main Menu Preprocessor Modeling Create Areas Rectangle By 2 Corners. 2. In Rectangle by 2 Corners of Figure 16 enter coordinates of small rectangular area (A3), WP X = 30, WP Y = 40, Width = 10, Height = 10 (mm), OK. By: Majid Soleimaninia Page 11

12 Figure 16: Build the small areas. Now you can subtract the small rectangular areas (A2 & A3) from the main big rectangular areas (A1): 1. Main Menu Preprocessor Modeling Operate Booleans Subtract Area. 2. In Subtract Areas of Figure 17 select the main area (A1) by clicking on it. Note: The selected area will turn pink once it is selected. Click 'OK' on the 'Subtract Areas' window. Now you should select the areas to be subtracted, select the smaller rectangles (A2 &A3) by clicking on them and then click 'OK'. Now, your model should be like Figure 17 and have the new rectangular area (A4) as you see. By: Majid Soleimaninia Page 12

13 Figure 17: Building geometry. To make the Copper section (Heat Generator) and we could: 1. Main Menu Preprocessor Modeling Create Keypoints In Active CS 2. In Create Keypoints in Active Coordinate System of Figure 18, enter number and coordinates of Copper rectangular section keypoints, i. NPT= 100, X = 20, Y = 10, Z = 0, Apply. ii. NPT= 200, X = 30, Y = 10, Z = 0, Apply. iii. NPT= 300, X = 30, Y = 20, Z = 0, Apply. iv. NPT= 400, X = 20, Y = 20, Z = 0, Apply. By: Majid Soleimaninia Page 13

14 Figure 18: Defining the Keypoints to build Copper rectangular section. 3. Main Menu Preprocessor Modeling Create Lines In Active Coord 4. Now in Lines in Active Coord of Figure 19, create lines by picking the exciting keypoints: i. Picking the Keypoints Number= 100 (a square symbol appears), then pick Keypoints Number= 200. ii. Picking the Keypoints Number= 200 (a square symbol appears), then pick Keypoints Number= 300. iii. Picking the Keypoints Number= 300 (a square symbol appears), then pick Keypoints Number= 400. iv. Picking the Keypoints Number= 400 (a square symbol appears), then pick Keypoints Number= 100. By: Majid Soleimaninia Page 14

15 Figure 19: Defining the Lines to build Copper rectangular section. 5. Main Menu Preprocessor Modeling Operate Booleans Divide Area by Line. 6. In Divide Areas by Line of Figure 20 select the main area (A4) by clicking on it. Note: The selected area will turn pink once it is selected. Click 'OK' on the 'Subtract Areas' window. Now you should select the lines to be divided, select the lines which we just made by keyponits by clicking on them and then click 'OK'. Now, your model should be like Figure 21 and have two new areas (A1&A2) as you see. By: Majid Soleimaninia Page 15

16 Figure 20: Dividing the main Area to two areas. Figure 21: Divided Areas ( A1 & A2). By: Majid Soleimaninia Page 16

17 To make the Aluminum section (Fins) and we could: 7. Main Menu Preprocessor Modeling Create Keypoints In Active CS 8. In Create Keypoints in Active Coordinate System of Figure 22, enter number and coordinates of Aluminum section keypoints, v. NPT= 500, X = 0, Y = 30, Z = 0, Apply. vi. NPT= 600, X = 50, Y = 30, Z = 0, Apply. Figure 22: Defining the Keypoints to build Aluminum section. 9. Main Menu Preprocessor Modeling Create Lines In Active Coord 10. Now in Lines in Active Coord of Figure 23, create lines by picking the exciting keypoints: v. Picking the Keypoints Number= 500 (a square symbol appears), then pick Keypoints Number= 600. By: Majid Soleimaninia Page 17

18 Figure 23: Defining the Lines to build Aluminum section. 11. Main Menu Preprocessor Modeling Operate Booleans Divide Area by Line. 12. In Divide Areas by Line select the main area (A2) by clicking on it. Note: The selected area will turn pink once it is selected. Click 'OK' on the 'Subtract Areas' window. Now you should select the lines to be divided, select the lines which we just made by keyponits by clicking on them and then click 'OK'. Now, the final model should be like Figure 24 and have three new areas (A1, A3 & A4) as you see. By: Majid Soleimaninia Page 18

19 Figure 24: Divided Areas (A1, A3 & A4). You also can see the list of all areas to distinguish them easily, Figure 25. Here the A1 is the Copper section, A3 is the Aluminum section and the A4 is the Steel section. Figure 25: List of Areas. By: Majid Soleimaninia Page 19

20 3.5 Define material & element attributes Next you have to associate each of the areas with your previous material numbers and element. 1. Main Menu Preprocessor Meshing Mesh Attribute Picked Areas. 2. In Area Attributes, seen in Figure 26, pick the small rectangle Copper area (A1). Note: there will be a Multiple-Entities window appears to select the correct area, OK. 3. In Area Attributes, seen in Figure 27, select (Material number = 1, Real constant set = None, Element type number = 1 PLANE55, Element coordinate sys = 0, Element section = None), OK. Define the Material attribute for other areas (A3 & A4) in the same way, just change Material number =2 for A3 and Material number =3 for A4. Figure 26: Define material & element attributes. By: Majid Soleimaninia Page 20

21 Figure 27: Define material 1 to picked Area (A1). 3.6 Mesh Size 1. Main Menu Preprocessor Meshing Size Cntrls Areas All Areas. 2. In Element Size on All Selected Area, seen in Figure 28, enter Size Element edge length = 1, OK. Figure 28: Define mesh size. By: Majid Soleimaninia Page 21

22 3.7 Meshing 1. Main Menu Preprocessor Meshing Mesh Areas Free. 2. In Mesh Areas, seen in Figure 29, click on Pick All, OK. Figure 29: Meshing the geometry. 3.8 Define Analysis Type 1. Main Menu Preprocessor Loads Analysis Type New Analysis. 2. In New Analysis, seen in Figure 29, pick Steady-State, OK. Figure 30: Define Analysis type. By: Majid Soleimaninia Page 22

23 3.9 Apply Constraints In this problem all sides of block have convection type of boundary condition except the bottom side which is isolated. In order to apply convection Boundary Conditions: 1. Main Menu Preprocessor Loads Define Loads Apply Thermal Convection On lines. 2. In Apply CONV on Lines, seen in Figure 31, select all the lines which are on the left, right and top sides except the bottom line, OK. Figure 31: Define the Boundary conditions to apply Convection. 3. The new window, Apply CONV on Lines, will appear, Fill in the window as shown in Figure 32. This will specify a convection of W/mm2.K and an ambient temperature of 293 Kelvin. Note that VALJ and VAL2J have been left blank. This is because we have uniform convection across the line, OK. By: Majid Soleimaninia Page 23

24 Figure 32: Applying the Convection Boundary condition. In order to apply insulated BC: 1. Main Menu Preprocessor Loads Define Loads Apply Thermal Heat Flux On lines. 2. In Apply HFLUX on Lines, select the bottom line, OK. 3. The new window, Apply HFLUX on Lines, will appear, Fill in the window as shown in Figure 33. This will specify insulated wall condition for the bottom wall, zero heat flux for bottom side. Note that VALJ has been left blank. This is because we have uniform heat flux across the wall, OK. By: Majid Soleimaninia Page 24

25 Figure 33: Applying the Insulated Boundary condition for the bottom wall. In order to apply heat source on the small rectangle (Copper section): 1. Main Menu Preprocessor Loads Define Loads Apply Thermal Heat Generate On Areas. 2. In Apply HGEN on ARs, seen in Figure 34, select the small copper area (A1), OK. Figure 34: Defining the heat generation BC for Copper section. By: Majid Soleimaninia Page 25

26 3. The new window, Apply HGEN on areas, will appear, Fill in the window as shown in Figure 35. This will specify 0.01 W/mm 2 heat generation rate on area section, OK. Figure 35: Applying the heat source on Copper section. 4 Solve the model To use the current (and only) load system (LS) enter: 1. Main Menu Solution Solve Current LS, review the listed summary, OK. 2. When the solution of the simultaneous equations is complete you will be alerted that the solution is done. By: Majid Soleimaninia Page 26

27 Figure 36: Solving for the current load set. 5 Post-processing 5.1 Plot Temperature It is always wise to visually check the computed displacements: 1. Main Menu General Postproc Plot Results Contour Plot Nodal Solu. 2. In Contour Nodal Solution Data, seen in Figure 37, DOF Solution Nodal Temperature, OK. Figure 37: plotting the nodal temperature results. By: Majid Soleimaninia Page 27

28 Now you will have nodal temperature contour plot of your model, as you can see in Figure 38. Figure 38: Nodal temperature contour plot. 5.2 Plot Temperature It is always wise to visually check the computed displacements: 3. Main Menu General Postproc List Results Nodal Solu. 4. In List Nodal Solution, seen in Figure 39, DOF Solution Nodal Temperature, OK. By: Majid Soleimaninia Page 28

29 Figure 39: Listing Nodal temperature result. By: Majid Soleimaninia Page 29