Conjugate Heat Transfer (CHT) Modeling in Ansys Discovery - Pt. 2
Hello, welcome to an Ozen Engineering video. In this session, we will continue our discussion on the conjugate heat transfer model. Previously, we constructed a simple model for an electronics cooling problem featuring a heat source with cooling air flowing through the enclosure. We obtained initial results using the explore mode, which allows for a quick setup without extensive mesh control.
Exploring Results
Let's delve into how to analyze these results:
- Contour Model: Visualize temperature distribution.
- Isosurfaces: Examine surfaces at specific temperatures, such as 98°C.
- Streamlines: Observe flow paths, colored by temperature or velocity magnitude.
- Particle Flow: Track the movement of particles within the flow.
- Direction Field: Create cuts to visualize flow direction and velocity magnitude.
To enhance the view, you can expand the bounds of the cut to include more of the flow region. This visualization can be colored by temperature to observe how the flow heats up through the heat sink.
Refining the Model
Once satisfied with the explore mode solution, you may opt for a more detailed analysis using the refine mode. This mode offers additional controls and mesh refinement options:
- Local Mesh Sizing:
- Set a predefined mesh size, such as 0.5 mm, on the die and heat sink.
- Global Mesh Control:
- Choose automatic determination, curvature, or proximity options.
- Simulation Options:
- Select static or steady-state simulation.
- Choose between tet mesh or poly mesh; poly mesh is recommended.
- Decide on using the live GPU solver or CPU, specifying the number of processors.
For instance, on a machine with 24 cores, you might allocate 20 cores for the simulation. This setup will use a polyhedral mesh and 20 processors to solve the model efficiently.
Simulation Progress and Results
As the simulation progresses, a progress bar will indicate the status. The process involves:
- Mesh generation
- Notification of the number of elements, providing insight into model size
- Visualization of the generated poly mesh and fluid volume
Upon completion, the results will show a peak temperature of 155°C, slightly lower than the 170°C observed in explore mode. The temperature contours and flow fields appear similar, validating the explore mode results. This refined run was completed in under 10 minutes.
Further Steps
You can choose to further refine the mesh or export the model to Fluent for additional analysis. To do this:
- Click the export button to save a Fluent version of the model.
- Open Fluent to continue with more advanced options available in Ansys Discovery.
Thank you for watching this video. I hope you found it useful, and I look forward to seeing you in the next video. Goodbye!
Hello, welcome to an Ozen Engineering video. We're going to continue discussing the conjugate heat transfer model. So far, we've built a simple model for an electronics cooling problem with a heat source and cooling air coming through the enclosure.
We've obtained these results in explore mode, which is a quick and dirty way to run the model without much mesh control. I'd like to go over how to interpret the results. The first option is the contour model, and another is isosurfaces. For example, here are some isosurfaces around 98 degrees C.
We can also look at streamlines, colored by temperature. One could color them by velocity magnitude as well. Another option is to look at particle flow, and the last one, which can be tricky, is the direction field. This shows a cut we create. Let's try creating a cut. So, let's hide these.
You can see there's already a cut for us. Let's try expanding the bounds on this. So, pull on the white lines to get more of the flow region. This shows velocity magnitude and what the flow is doing. We can color this by temperature, which is more interesting.
You can see how the flow heats up as it goes through the heat sink. Once satisfied with the solution in explore mode, if the design is complete, you'll likely want a more resolved, higher quality solution. To achieve this, move on to the refine option.
Here, we have additional controls and more power over the mesh. I'll talk about these, set up the case with more meshing and solution controls, and see what the solution looks like. Is it much different than the one we got in explore mode? In refine mode, we have local mesh sizing.
We can assign sizes to a body, face, or edge. Another way to control mesh size is globally. Here, we have options like curvature and proximity. Let's let it do it automatically and then see what else we can do. Simulation options: We don't necessarily have to specify calculation type.
I'll choose a static or steady-state simulation. We can use the live GX solver or not. We can use processors. We'll keep the default turbulence model and not play with convergence settings. We can have tet mesh or poly mesh. I'm a fan of poly mesh, so I'll turn it on.
We can use the live GPU solver or let it use the CPU. We can control the number of CPUs under settings. I have 24 cores, so I'll ask for 20. Let's see what else we can do. We'll solve using 20 cores. Let's pick our refine level. We'll try to stay here so it's not a very fine mesh.
We can see the added local refinement, poly mesh, and polyhedral mesh. Let's start our solution and see what happens. As the solution proceeds, we'll have a progress window. First, it generates the mesh, then comes up with a notification giving us the number of elements.
This helps us understand the model size. Once the solution is complete, we'll get a figure like this. We can turn off the direction field and turn back on the contours. We see the peak temperature of 155, slightly under the 170 degrees C we had in the explore option.
The results seem similar, and this run was fast, taking under 10 minutes. We can export this to Fluent for further options. That's all for this video. I hope you enjoyed it. Thank you for watching. I hope you find it useful, and I'll see you again on my next video. Goodbye.
