Properties of cryogenic fluids

The easiest way to cool and maintain an object or experiment at low temperature is to use cryogenic fluids, derived from gases liquefied by industrial processes.

Despite the special requirements, this process offers numerous advantages.

The enthalpy of formation (latent heat) generally provides the reserve of frigories contained in the cryogen enclosed in the cryostat.

Steam also has a cooling capacity that can be used in temperature ranges between bath temperature and ambient temperature. The notion of sensible enthalpy (sensible heat) between the boiling temperature under atmospheric pressure and ambient temperature is often used.

The most frequently used cryogenic fluids, such as liquid nitrogen between 100 and 65 K, liquid hydrogen between 30 and 15 K and liquid helium 4 between 5 and 1 K, are described, as well as liquid neon, xenon and helium 3, fluids with interesting properties for certain specific applications.