I think you're right in this case, but sometimes thermodynamically sound machines can seem like cheating at first glance. Heat pumps[1], for example, can have g

I think you're right in this case, but sometimes thermodynamically sound machines can seem like cheating at first glance. Heat pumps[1], for example, can have greater than 100% thermal efficiency (although they do rely on reservoirs of heat to do it). Another example is the vortex tube[2], which can separate a compressed gas into hot and cold streams with no moving parts (and relies on pressure to do it). [1] https://en.wikipedia.org/wiki/Heat_pump https://en.wikipedia.org/wiki/Heat_pump [2] https://en.wikipedia.org/wiki/Vortex_tube https://en.wikipedia.org/wiki/Vortex_tube