So like refrigerators and freezers and things like that use the Carnot Cycle. And I understand how that cools things down. But I’ve also heard that with conventional methods the biggest temperature difference you can make is about 100⁰C. So how do we get something like liquid nitrogen at -195⁰C? Are we putting a freezer inside a freezer inside a freezer? Or how do we get stuff that cold?
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Liquid nitrogen is made by fractional distillation of air. In general, air is compressed a lot, this heats it up, but it is then allowed to cool back to room temperature while staying compressed. When it’s room temp again it is allowed to expand, which cools it down a lot. Repeat the process til you’ve separated out the different gasses in air and eventually you’ll have liquid nitrogen.
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