Cryogenic engineering is a sub stream of

mechanical engineering Mechanical engineering is the study of physical machines and mechanism (engineering), mechanisms that may involve force and movement. It is an engineering branch that combines engineering physics and engineering mathematics, mathematics principl ...

dealing with

cryogenics In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a universa ...

, and related very low temperature processes such as air liquefaction, cryogenic engines (for rocket propulsion),

cryosurgery Cryosurgery (with ''cryo'' from the Ancient Greek ) is the use of extreme cold in surgery to destroy abnormal or diseased tissue; thus, it is the surgical application of cryoablation. Cryosurgery has been historically used to treat a number o ...

. Generally, temperatures below cold come under the purview of cryogenic engineering. Cryogenics may be considered as the recent advancement in the field of

refrigeration Refrigeration is any of various types of cooling of a space, substance, or system to lower and/or maintain its temperature below the ambient one (while the removed heat is ejected to a place of higher temperature).IIR International Dictionary of ...

. Though there is no fixed demarcation as to where refrigeration ends and cryogenics begins, for general reference, temperatures below –150c(120k) are considered as cryogenic temperature. The four gases which mainly contribute for cryogenic application and research are (O2-B.P.90K), (N2-B.P.77K), (Helium-B.P.4.2k) & (H2-B.P.20K). The word "cryogenic" is derived from Greek κρύο (cryo) - "icy cold" + γονική (genic) – "having to do with production".

References

{{Thermodynamics-stub Cryogenics Mechanical engineering