3. Helium liquefaction

3.1 General

We assume that the helium to be liquefied has been purified beforehand.

Helium liquefaction involves transforming a gas at room temperature into a boiling liquid at a pressure slightly higher than the local atmospheric pressure. This transformation is achieved by extracting energy from helium (figure 13 ).

The amount of energy to be extracted to liquefy one liter of helium at 1.2 bar is 189218 J; however, according to Carnot's principle, the theoretical amount of energy to be expended at 300 K to liquefy one liter of helium at 1.2 bar is 808049 J.

The efficiency of a helium liquefier...