Spacecraft thermal control analysis employs modelling programs that can analyze combinations of conduction, convection, and radiation heat transfer in complex structures. An example is Sinda by MCS Software. I have no association with MSC Software but I did work on thermal analysis problems for the Apollo Service Model in the early 1960s using primitive versions of what are now much more advanced (I am sure) software.
Complex structures are analyzed by developing thermal networks and are solved through analogies to electrical networks. Using these programs you can analyze a proposed system structure throughout a mission cycle including transient direct solar, earth emitted and earth reflected radiation as the satellite transits in an orbit in some orientation. The thermal models consider as well internal thermal generation. Conduction/radiation paths between components would be constructed from the proposed geometry. If the proposed component layout shows a thermal problem, i.e. some structure gets too hot or cold, you can examine the need to relocate the component, alter thermal pathways, or provide some means of thermal control. You can then re-analyze your changes.
For the Apollo service module verification of the thermal calculations was so important that a thermal simulator was built that housed a service module and simulated radiant thermal inputs to simulate various attitudes in orbit and lunar transcoast. Comparison between calculations and simulations was not too bad even then. Now I'm sure it would be much better.
I don't know the magnitude of your nano-satellite program but some thermal analysis is likely necessary using Sinda or some other equivalent to provide confidence that components can remain within satisfactory temperature ranges.
As a preliminary step take a look at the proposed layout, heat inputs, heat generation and do some simple analyses to see if there is some obvious likely problems.
