Helium liquefaction and medium and high energy consumption helium refrigeration.

This dossier is part of a series of articles on cryogenics.

All cryogenic activity starts with obtaining low temperatures.

Temperatures above 80 K (– 193 °C), the approximate boiling point of liquid nitrogen, are obtained industrially during the liquefaction of natural gas (methane) [J 3 601] and the separation of gases from air [J 3 600].

Liquid hydrogen, which boils at around 20 K (– 253°C), is also liquefied industrially in much smaller quantities [J 3 603].

Helium, on the other hand, has a boiling point of around 4 K (– 269°C), and is a rarer, more expensive gas, reserved for uses such as superconductivity, which require very low temperatures. Helium liquefaction/refrigeration is currently an industrial activity, but its diffusion is still relatively limited, as it is linked to the development of superconductivity. The two main fields concerned are :

• helium cooling and maintenance of the huge cryogenic structures of large gas pedals and particle storage rings for physics research;

• helium liquefaction at production sites (helium is extracted from natural gas [J 3 605] for transportation and commercial distribution in liquid form, in order to reduce costs).