Cryogenic temperatures between 459.7T (absolute zero) (-273C) and -250F (-157C). Many of the substances that are completely different in character at those temperatures. For example, a steel plate in -350F (212C)when the fell on the floor will shatter like glass. Gases such as oxygen, nitrogen, argon, hydrogen and helium can be liquefied and separated at such temperatures.
Three methods were used to create these low temperatures:
The process of expansion of the heat exchangers (Joule-Thompson process).
The process of expansion of the heat exchangers and gas for the job.
Several cascade system.
Science cryogenics has produced a lot of useful instant freezing and refrigeration equipment. Nitrogen in 35CPF (212C) is used to instantly freeze plant and animal tissues or other rapidly dividing elements, hi thus, they are preserved for future study of Liquid oxygen is a convenient way to store millions of tons of rocket fuel. It is also used as negative cooler for steel, making it less prone to distortion.
Liquid nitrogen is poured into more General ambient temperatures immediately into steam.
The temperature of this pair-320F ( 196C). This process is used in some freight cars, requiring deep freezing conditions. It is used in immersion freezing. It is also used to "freeze " dry" food". Freeze drxjing is a cryogenic process where the food instantly frozen. A strong vacuum is used to delete all of the ice crystals. The resulting food, if kept dry, does not require any cooling.
Particular caution should be observed in the operation and maintenance of cryogenic equipment. Liquid and ultracold will be severely injure those who come into contact with them. Warning: You should always wear protective glasses and gloves when servicing any part of cryogenic equipment. Cryogenic temperatures are very low. The liquid refrigerant will instantly freeze any part of your body touch.
In the presence of such a low temperatures, special materials must be used in construction. They include Nickel (stainless) steel, copper alloys, aluminium and metals. Electrical devices must be of special design and construction.
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