Cryogenic operation

Jotile-Thomson Valves The principal function of a J-T valve is to obtain isenthalpic coohng of the gas flowing through the valve. These valves generally are needle-type valves modified for cryogenic operation. They are an important component in most refrigeration systems, particularly in the last stage of the liquefac tion process. Joule-Thomson valves also offer an attractive alternative to turboexpanders for small-scale gas-recovery applications. 

Use fully killed or fine grain steel, controlled rolling temperatures high Mn/C ratios eliminate sharp corners in design, remove defects from steel heat treat steel. For cryogenic operations use high nickel alloy steels or austenitic stainless steels, depending on temperature. 

Separation by distillation requires cryogenic operation or pressures above about 20 atmospheres ... 

There have been several recent bolometer designs which have succeeded in making the internal noise sources very small. Thus Drew and Sievers [3.39] have shown that with an element cooled to about 0.5 K in a He cryostat the NEP associated with the temperature and Johnson noise is about 10" " while Draine and Sievers [3.40] have shown that using He dilution cooling to 0.1 K this NEP falls to 3 x 10 WHz However this very low value could probably only be exploited in an experiment conducted entirely at cryogenic temperatures, and would certainly require a cryogenically operated low noise amplifier. 

Question by C. B, Barnes, Jr., North American Aviation Have you investigated the use of any cryogenic operating materials other than nitrogen ... 

The move to the West Coast for this past Cryogenic Engineering Conference was prompted in part by the large concentration of missile activities which are to be found there. Recognition of cryogenic operations and techniques in the missile field is given in many of the included papers. 

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