hii i need a cryogenics notes bcz no books available in collage libarery or outside so plz provide the good notes

Cryogenic engineering is a sub stream of mechanical engineering dealing with cryogenics, and related very low temperature processes such as air liquefaction, cryogenic engines (for rocket propulsion), cryosurgery. Generally, temperatures below the boiling point of Nitrogen (77 K) comes under the purview of cryogenic engineering. Cryogenics may be considered as the recent advancement in the field of refrigeration. Though there is no fixed demarcation as to where refrigeration ends and cryogenics begins even then for general reference temperature 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 cryogenics is derived from two Latin words. Cryo - means cold and Genics - means science. Cryogenics is the science of cold.