Thermal Desktop requires "thermal" surfaces and solids. These can be meshes or Finite Difference surfaces/solids. Geometry can be imported as you did, but it needs to be used for either scaffolding to create the thermal model, or it needs to be meshed into finite elements.
Using TD Direct is a great way to go from the design geometry to a thermal model, but it will take a lot more than repairing. It is important to simplify the geometry first. There is often far too much detail in the geometry that will have no effect on the thermal analysis. It will take some judgment and experience to get a sense of what features you can remove. Unfortunately, a common problem for newer thermal engineers who do not have that experience yet is to attempt to model every detail with the idea they can remove it later. If it will even mesh, then it tends to make a large, cumbersome model. Thermal analysis is at the system-level, which in your case will likely mean the entire satellite through many different orbits and scenarios. A slow model with unnecessary detail can cause major problems.
Finite Difference objects are regular shapes where we can use basic conduction equations as you would by hand. For example, KA/L, or you might remember ln(r1/r2) for a thick cylinder. When you have regular shapes such as rectangles, bricks, cylinders, cones, discs, and so on, these can be created in Thermal Desktop and are typically much faster that Finite Element.
Specifically in terms of your project, I would recommend starting with a bit of simplification and separation. I assume with over 6000 parts, many of them are screws, for example. You may need the information to calculate the conduction coefficient from one part to another, but you typically do not model screws. I would use external reference in SpaceClaim to get the parts into managable segments. Simplify, repair, and mesh. In many situations you might find that it is easier to recreate the geometry using SpaceClaim's push/pull rather than simplifying and repairing. Sometimes I copy some key edges from the detailed geometry and put them into a new drawing, and then build a simplified version from that. This is because SpaceClaim can have a hard time with sorting out exactly how you want something simplified, particularly if it was imported from another program.
We have not yet fully integrated our support into the Ansys system. It's in work. For now, you can find training material on our website, crtech.com. Here is a link to our videos about TD Direct. You will find our full TD Direct training in 2 parts. https://www.crtech.com/training/videos?f%5B0%5D=product%3A1748 There are also videos about specific topics. We have tutorials as well. If you don't have an account, go ahead and register. Thermal Desktop users can get an account. And perhaps most importantly, you will find links to our support team. Sending an email is the best way to get help.
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