Liquefaction of Gases
The conversion of a gas into a liquid by cooling below its critical temperature and applying pressure.
Unit
K
In depth
Cooling must come first, since compression alone cannot liquefy a gas above its critical temperature. Industrially, gases are liquefied by repeated compression and Joule–Thomson expansion in a regenerative Linde cycle, or by expansion against a piston that extracts work.
Examples in the real world
Liquid nitrogen at −196 °C for cryogenic storage; LPG cylinders holding propane liquefied under modest pressure.