How does cooling work in industries that use liquid nitrogen or other gases?


I understand that liquid nitrogen & oxygen are the cooled forms of their gas forms. But how do we cool the gases to reach these cold temperatures? Is it done by pressure chambers? or other forms of heat transfer? I was researching how ACs work and became very interested in heat transfer.

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Basically, on a commercial scale, large amounts of air are compressed to high pressures. This adds a lot of heat, so the compressed air is cooled, and then allowed to expand, which causes the temperature to drop significantly (not unlike how an AC works), and the gasses condense as a liquid. The nitrogen, oxygen, and argon are then separated out via distillation.