Editing Joule–Thomson effect (section)

==Applications==

In practice, the Joule–Thomson effect is achieved by allowing the gas to expand through a [[throttle|throttling device]] (usually a [[valve]]) which must be very well insulated to prevent any heat transfer to or from the gas. No external work is extracted from the gas during the expansion (the gas must not be expanded through a [[turbine]], for example).

The cooling produced in the Joule–Thomson expansion makes it a valuable tool in [[refrigeration]].<ref name="Basics of Joule–Thomson Liquefactio"/><ref>Keenan, J.H. (1970). ''Thermodynamics'', Chapter 15. M.I.T. Press, Cambridge, Massachusetts.</ref> The effect is applied in the [[Hampson–Linde cycle|Linde technique]] as a standard process in the [[petrochemical industry]], where the cooling effect is used to [[liquefaction of gases|liquefy gases]], and in many [[cryogenic]] applications (e.g. for the production of liquid oxygen, nitrogen, and [[argon]]). A gas must be below its inversion temperature to be liquefied by the Linde cycle. For this reason, simple Linde cycle liquefiers, starting from ambient temperature, cannot be used to liquefy helium, hydrogen, or [[neon]]. They must first be cooled to their inversion temperatures, which are −233&nbsp;°C (helium), −71&nbsp;°C (hydrogen), and −42&nbsp;°C (neon).<ref name=":Atkins1"/>