Cool thing I discovered in a book the other day: the Ranque-Hilsch vortex tube, usually just called a vortex tube (for obvious reasons). It's a simple tube, with no moving parts, that has an airflow looking like this:
It works by creating a vortex of air. The outside vortex is fast-moving with lots of kinetic energy, which creates a high temperature. The high-temperature air escapes out the sides of the cone, while the cooler, slower air inside is forced into the inner vortex and out the other end. Middle-temperature air cannot go out either the inside or outside holes, and hence must go to one extreme or the other before it leaves the tube.
It's less efficient that normal AC equipment, and it needs a lot of heatsinking for constant use, but it's good for spot cooling when a supply of compressed air is available.
It may work with some liquids as well.
It's also been used for uranium enrichment, in a process called Helikon vortex separation. It's been used by South Africa to produce both reactor-grade (3-5% 235U) and bomb-grade (~90% 235U) uranium. It requires huge amounts of electricity and cooling devices, but it does work, and it's easier to hide than centrifuges.
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