The problem is equivalent to the previous tutorial. The new concern is 3 dimensional modeling.

The enclosing container is made of steel with thermal conductivity of 20 W/m K.

The fins are made of aluminum with thermal conductivity of 180 W/m K.

Units: Use S.I. units … centimeters ONLY

Geometry: See figure.

Boundary conditions: There is convection along all the boundaries of the fin assembly except the bottom, which is attached to the steel block. The Film Coefficient is 50 W/m²K and the Bulk (ambient) Temperature is 293 K. The block contains a copper rod that generates heat, totaling 27.2 W. The sides of the steel block are insulated. The bottom area of the block loses heat totaling 5.44 W. Remember to use units of W/m³ for heat generation and W/m² for heat flux.

Objective:

	To determine the nodal temperature distribution.
	To determine the maximum value of temperature in the component.

You are required to hand in print outs for the above.

Figure:

Go to the ANSYS Main Menu

The following window comes up:

Enter the following data values to create the full steel base of the heat generating volume.

Next, we want to create the fins that will constitute the assembly. If you had hit APPLY instead of OK, then the window will still be usable. Otherwise, use Create Volume by 2 Corner and Z again to create the first fin.

Now we want to copy the fin volume and paste it offset so that it is correctly positioned along the bottom of the fin assembly.

Preprocessor>Modeling>Copy>Volumes Select the volume to be copied. Next, the following window appears:

Enter the value for the offset, which is 0.009m and then click Apply. Note that the copy volumes dialog box on the left is still open. Simply pick the new volume and hit apply again. Hit apply in the window that appears because the offset is still 0.009. Continue until all the fins are there. If you didn’t hit apply just start from Modeling>Copy>Volumes.

The model should appear as below so far.

Next choose Preprocessor>Modeling>Operate>Booleans>Add>Volumes.  Choose the fins and bottom of the fin assembly (the thin layer that extends across the model) Hit OK. You can also hit PICK ALL

Next, create the base (the electronic component):

Enter the values as shown.

Next, glue the new completed fin assembly to the base, by using Preprocessor>Modeling>Operate>Booleans>Glue>Volumes. Choose the base, and click once on the fin assembly (it should all be selected as one now, if not try repeating the last step). Hit OK

Now, create the volume for the copper heat generating element. Preprocessor>Modeling>Create>Volumes>Cylinder>Solid Cylinder

The last step is to use Preprocessor>Modeling>Operate>Booleans>Overlap and select the copper volume and the steel, click OK.

Also, reuse the glue command, ...>Operate>Booleans>Glue>Volumes to glue the cylinder to the base.

The modeling is now finished.

We need to define material properties separately for steel, aluminum, and copper.   

Go to the ANSYS Main Menu

Click Preprocessor>Material Props>Material Models.  In the window that comes up choose Thermal>Conductivity>Isotropic. 

Enter 1 for the Material Property Number and click OK. The following window comes up.

Fill in 20 for Thermal conductivity. Click OK.

Now the material 1 has the properties defined in the above table. This represents the material properties for steel. Repeat the above steps to create material properties for aluminum (k=180, Material number 2), and copper (k=386, Material number 3).  Do this by selecting Material>New Model in the “Define Material Model Behavior” window. Once finished, exit the material model window.

SELECTING ELEMENT TYPE:

Click Preprocessor>Element Type>Add/Edit/Delete... In the 'Element Types' window that opens click on Add... The following window opens.

Type 1 in the Element type reference number.

Click on Thermal Mass Solid and select Brick 8node 70. Click OK. Close the 'Element types' window.

So now we have selected Element type 1 to be a thermal solid 8node element. The component will now be modeled with thermal solid 8node elements. This finishes the selection of element type.

DIVIDING THE TOWER INTO ELEMENTS:

Go to Preprocessor>Meshing>Size Controls>Manual Size>Lines>All Lines. In the menu that comes up type 10 in the field for 'No. of element divisions'.

Click on OK. Now when you mesh the figure ANSYS will automatically create meshes that have at least ten elements along each line regardless of how long each line is!

First we will mesh the steel volume. Go to Preprocessor>Meshing>Mesh Attributes>Default Attributes. Make sure the window indicates "Material Ref.#1". The window is shown below.

Now go to Preprocessor>Meshing>Mesh>Volumes>Free. Pick the steel area and click OK.

After you mesh the first section, the plot function of ANSYS may only display that meshed solid. To reveal the other solids, use Utility Menu>Plot>Volumes. Even though the already meshed area appears like it did originally, it is STILL meshed! Continue to the next steps.

Repeat the same process for the aluminum and copper areas. However, change two things:

For the Aluminum fin assembly, change the mess size on the lines to .01 cm per element:

Go to Preprocessor>Loads>Define Loads>Apply>Thermal>Heat Generate>On Volume.

Select the copper rod volume. Click OK.

Since the volume of the rod is 9.19e-6 and the total Q = 27.2 W, heat generation is 2.96MW/m³

The following window comes up. Enter this datum.

Next, we apply the convective boundary conditions.

Go to Preprocessor>Loads>Define Loads>Apply>Thermal>Convection>On Areas.

In ISO viewing mode, pick the areas that are clearly visible and don’t try to pick them all at once. Make notes in a text file or use a piece of scrap paper if you want to keep track of what you have selected already (such as fins, front, iso or fins, top iso and so on) Click OK. The following window comes up.

Just remember that you want to select the aluminum assembly areas, which mean the fins sticking out and the thin bottom of the aluminum assembly. Remember not to pick the bottom side of it too.. because that section is exposed to heat, not convection. And do NOT select the sides of the steel block! They are insulated.

For each convection … apply the following values:

Enter 50 for "Film Coefficient" and 293 for "Bulk Temperature" and click OK.

Now the Modeling of the problem is done.

Now add heat loss through the bottom of the model, which has a surface area of .007224m²

Given that the heat lost from the base is 5.44 W, the heat flux will be -753.045 W/m²

Do this by Preprocessor>Loads>Define Loads>Apply>Thermal>Heat Flux>On Areas

Choose the bottom area (try pan zoom rotate again) and then enter the value of flux as shown below.

Go to ANSYS Main Menu>Solution>Analysis Type>New Analysis.

Select Steady State and click on OK.

Go to Solution>Solve>Current LS.

An error window may appear. Click OK on that window and ignore it.

Wait for ANSYS to solve the problem.

Click on OK and close the 'Information' window.

Listing the results.

Go to ANSYS Main Menu General Postprocessing>List Results>Nodal Solution. The following window will come up.

Select DOF solution and Temperature. Click on OK. The nodal displacements will be listed as follows.

You will find the maximum value of temperature at the end of the above table.

You can also plot the displacements and stress.

Go to General Postprocessing>Plot Results>Contour Plot>Nodal Solution. The following window will come up:

Select DOF solution and Temperature to be plotted and click OK.  The output will be like this: (playing with Pan Zoom Rotate)