Cryogenic freezing is a type of freezing which requires extremely low temperatures, generally below -2380 F (-1500 C). This process is a part of a branch of science cryogenics, which focuses on the production of very cold temperatures and the study of what happens to objects subjected to these temperatures. By using cryogenic freezing, it is possible in theory to keep an object frozen indefinitely without any "aging" related loss in the object. Generally, cryogenic freezing is used to freeze living objects. It is a process developed to safely freeze and thaw living objects so they can be revived to the exact condition they were in when they entered the freezing process. Research in this field ranges from basic studies on severe cold and also in applied research, in which cryogenics is applied to various issues confronted by humans.
Liquefied gases, such as liquid nitrogen and liquid helium are used to achieve cryogenic freezing. Liquid nitrogen is the most commonly used element in cryogenics and is legally purchasable around the world. Liquid helium is also commonly used and allows for the lowest attainable temperatures to be reached in a laboratory setting. These gaseous liquids are held in either special containers known as Dewar flasks, which are about 6 feet tall and three feet in diameter or giant tanks in large commercial operations. Just generating the extremely cold temperatures required for cryogenic freezing requires a lot of work. It is not as simple as turning up a refrigerator, since refrigeration components can only withstand so much cold before breaking apart.
gases can only exist in a liquid state at extremely high pressures or extremely cold temperatures. When these liquid gases, under high pressure, are allowed to escape from the tanks, they suddenly expand creating a drop in temperature. As the temperatures drop, the rest of the gas will convert to super cold liquid at that temperature. Once the gas is in liquid form, it can be used for cryogenic freezing. Once frozen at such low temperatures, objects can remain frozen with the use of special refrigeration units, including mobile units with liquefied gases which permit cryogenically frozen objects to be shipped. Cryogenic freezing is utilized to temper high end metal products and certain other industrial products. Cryogenic transfer pumps are the pumps used on Liquefied Natural Gas (LNG) piers to transfer Liquefied Natural Gas from LNG carriers to LNG storage tanks, through cryogenic valves.
Many people are confused with the term cryonics and cryogenics. Cryonics is the field of preserving human bodies in freezing conditions with the goal of reviving them at some point in the future. This is totally different from cryogenic freezing which is a freezing process in extremely low temperatures.