CRYOGENICS

CRYOGENICS

ABSTRACT

Cryogenics is the study of how to get to low temperatures and of how materials behave when they get there. Besides the familiar temperature scales of Fahrenheit and Celsius (Centigrade), cryogenicists use other temperature scales, the Kelvin and Rankine temperature scales.
    The word cryogenics means, literally, the production of icy cold; however, the term is used today as a synonym for low temperatures. The point on the temperature scale at which refrigeration in the ordinary sense of the term ends and cryogenics begains is not shortly defined. The workers at the National Burea of standards at Boulder, Colorado, have chosen to consider the field of cryogenics at that involving temperature below -150 C, while the Freon refrigerants, hydrogen sulfide, ammonia, and other conventional refrigerant all boil at temperature above -150 C.       
        In the field of cryogenic engineering, one is concerned with developing and improving low temperature technique, processes, and equipment. As contracted to low temperature physics, cryogenic engineering primarily involves the practical utilization of low temperature phenomena, rather than the basic research, although the dividing line between the two fields is not always clear cut.
In general we shall use the term cryogenic system to refer to an interacting group of components involving low temperatures. Air liquefaction plants, helium refrigerators, and storage vessels with the associated controls are some examples of cryogenic systems.