Editing Cryocooler (section)

== Joule-Thomson cooler ==
[[File:Schematic JT cooler.jpg|class=skin-invert-image|300px|thumb|Fig. 8 Schematic diagram of a JT liquefier. A fraction ''x'' of the compressed gas is removed as liquid. At room temperature it is supplied as gas at 1 bar, so that the system is in the steady state.]]
The Joule-Thomson (JT) cooler was invented by Carl von Linde and William Hampson so it is also called the Linde-Hampson cooler. It is a simple type of cooler which is widely applied as cryocooler or as the (final stage) of coolants. It can easily be miniaturized, but it is also used on a very large scale in the liquefaction of natural gas. A schematic diagram of a JT liquefier is given in Fig.8. It consists of a compressor, a counterflow heat exchanger, a JT valve, and a reservoir.

===Cooling cycle===
In Fig.8 the pressures and temperatures refer to the case of a nitrogen liquefier. At the inlet of the compressor the gas is at room temperature (300 K) and a pressure of 1 bar (point a). The compression heat is removed by cooling water. After compression the gas temperature is ambient temperature (300 K) and the pressure is {{convert|200|bar|psi}} (point b). Next it enters the warm (high-pressure) side of the counterflow heat exchanger where it is precooled. It leaves the exchanger at point c. After the JT expansion, point d, it has a temperature of {{convert|77.36|K|C F}} and a pressure of 1 bar. The liquid fraction is ''x''. The liquid leaves the system at the bottom of the reservoir (point e) and the gas (fraction 1 − ''x'') flows into the cold (low-pressure) side of the counterflow heat exchanger (point f). It leaves the heat exchanger at room temperature (point a). In order to keep the system in the steady state, gas is supplied to compensate for the liquid fraction ''x'' that has been removed.

When used as a cryocooler it is preferable to use gas mixtures instead of pure nitrogen. In this way the efficiency is improved and the high pressure is much lower than 200 bar.

A more detailed description of Joule-Thomson coolers and Joule-Thomson refrigerators can be found in.<ref>{{Cite journal |last=de Waele |first=A. T. A. M. |date=2017-03-01 |title=Basics of Joule–Thomson Liquefaction and JT Cooling |journal=Journal of Low Temperature Physics |language=en |volume=186 |issue=5 |pages=385–403 |doi=10.1007/s10909-016-1733-3 |issn=1573-7357|doi-access=free }}</ref>