Hi @Patrysie, very interesting!
If you know volume flow rate and heat generated you could model the miner. That is, have an inlet and outlet appropriately placed at the corresponding positions for the miner inlet and outlet. So the atmosphere boundaries could be inlet-outlets and the miner could have a velocity outlet at its inlet (if that makes sense) and a custom velocity inlet at its outlet with a custom temperature definition set to flux heat. This is entirely untested but to me, it makes the most simple setup without actually putting a fan in there.
Let me know what you think,
Darren