Radio Frequency (RF) Amplifier Thermal Analysis with Ansys Icepak: Part 2

Radio Frequency (RF) Amplifier Thermal Analysis with Ansys Icepak: Part 2 Welcome to the second part of our video series where we're looking at an RF amplifier model within a classic ice pack. In our previous video, we built all of our components from scratch.

Essentially, within our cabinet, we have a fan to cool down the system. We also have a heat sink that sits on top of our heat-generating amplifier. Heat sources are defined as 2D sources named "device." We also have a PCB. The next step is meshing.

For meshing, we want to do some assembly strategy, which has two benefits: better meshing and a better structure. We currently have individual pieces under the tree, but we're going to start building some assemblies and putting them into groups together so that they look better organizationally.

Before we jump into that, I want to talk about the views. For example, right now, you can see some verbiage on the model, like part names and component names. If you don't want these, you can go under "View" and select "Display Object Names" and then choose "None." This will never show it.

Or, you might prefer "Object Names Selected," which will show only the selected objects. Another way to limit the view is by turning off certain types of objects. For example, if you wanted to see only fans or heat exchangers, you can turn other things off.

Let's say we want to hide heat sinks; we can remove them from the view. We can also remove packages, and so on. Now, I'm going to organize this using two separate assemblies. First, I'll create an assembly for the amplifier part.

I'll switch to the positive X view, press shift, and draw a box around all the amplifier components. Then, I'll go to "Housing," right-click, and select "Create an Assembly." This will contain all the selected objects within that box. Next, I'll create another assembly for the fan.

I'll select a box around these components and name it "Fan Assembly." Now, we have two assemblies within our cabinet. One concept for meshing is "slack" with Icepak meshing.

This is an additional marginal distance from your object that you specify, so that the passage between non-conformal cells is smoother. If you put a very small slack value, it will decrease the number of cells, but it may be difficult for the mesh to generate a quality one.

On the other hand, you don't want too large slack values, because that will cause excessive mesh bleeding. Typically, you want to have slack values so that you get one to two cells across the slack region.

In this particular model, we have two assemblies, and as you can see, the distance between them is pretty high. So, we can easily do non-zero slack values. Let's start defining our slack values.

I'll double-click on "Amplifier" and select "Meshing." I'll select the amplifier, then "Mesh" separately, and define our slack settings for the amplifier. We can have zero slack in the x direction, 20 millimeters as the minimum, and 50 millimeters as the maximum.

Next, we'll define the slack for our fan. We'll follow the same strategy: go to "Meshing," select "Mesh" separately, and set the slack settings. Now that we've defined our assembly-related mesh control, we can go to our general mesh controls.

We'll go to "Model" and then select "Generate Mesh." This will bring up a window where we can select our meshing method and do the generation. We'll also define some maximum element sizes, gaps, etc. Once we've defined our mesh, we can check it.

To do this, we'll go to the "Display" tab and select "Display Mesh." We can look at some selected surfaces or use a cut plane. For example, we can make a plane right across the Z plane at the mid-Z plane. We can switch to an X plane or a Y plane and look at the different sets of mesh.

If we're not happy with the resolution, we can change it. We can change the sizes, improve our mesh, and look at it in different ways. Now, let's regenerate our mesh using the default option. This will quickly generate a finer level of mesh. Next, we'll create a new mesh and set up our solution.

We'll go under "Project," select "Solution Settings," expand it, and double-click on "Basic Settings." Here, we can change the number of iterations, convergence criteria for flow, and energy. In some problems, you might want to add one or two more, making it more restrictive.

Now, we'll solve for flow velocity, pressure, and temperature. We'll select "Buoyancy Driven" for flow, use Boussinesq's approximation, and define the gravitational acceleration and its direction. For this problem, we're going to ignore radiation impacts and not include solar radiation.

We'll do a single-state, steady-state problem where variables are not dependent on time. Once we've set up our solution, we can run it. Before doing that, we'll double-click on our basic parameters and define our ambient conditions. We can also set a temperature limit for specific objects.

Now, we're ready to run our solution. We'll hit the "Calculator" button and then the "Run Solution" button. We can provide a solution ID name, like "Base Solution," and monitor the progress.

Once the solution is complete, Fluent will write out solutions and export them back into Icepak for our viewing pleasure. Now that we have a converged solution, we can examine the results and do some post-processing.

We can look at our maximum temperatures, make section cuts, and create ISO surfaces. We can also look at a summary report, which will give us numerical values for different objects. We can see the heat flow, volumetric flow, and temperature for our heat sink and fan.

Finally, we can create a variation plot to show how the velocity is distributed between different channels of the heat sink. This can help us decide whether to add another fan or make other adjustments. That concludes our presentation for this model.

Thank you for your attention, and have a great day!