Misplaced Pages

This is an old revision of this page, as edited by 205.238.224.190 (talk) at 19:02, 12 October 2005 (Additional Information on Uses of Cryogenics). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Cryogenics is the study of very low temperatures or the production of the same, and is often confused with cryobiology, the study of the effect of low temperatures on organisms, or the study of cryopreservation. Likewise, cryonics is the nascent study of the cryopreservation of the human body. Unlike cryogenics, cryonics is not an established science and is viewed with skepticism by most scientists and doctors today.

Liquefied gases, such as liquid nitrogen and liquid helium, are used in many cryogenic applications. These gases are held in either special containers known as Dewar flasks, which are generally about six feet tall and three feet in diameter, or giant tanks in larger commercial operations. Dewar flasks are named after their inventor, James Dewar, the man who first liquefied hydrogen. Smaller vacuum flasks typically used at museums for demonstration are a Dewar flask fitted in a protective casing. Liquid nitrogen is the most commonly used element in cryogenics and is legally purchaseable around the world. Liquid helium is also commonly used and allows for the lowest attainable temperatures to be reached.

Leiden, Netherlands is sometimes called "The Coldest Place on Earth", because of the revolutions in cryogenics that happened there. Some of these advances in science were the discovery of superconductivity by Heike Kamerlingh Onnes, the liquefaction of helium by Kamerlingh Onnes, and the solidification of helium by Kamerlingh Onnes' pupil, Willem Hendrik Keesom. The word "cryogenics" does not get its name from the Netherlands though. The word "cryogenics" comes from two greek words; "kryos", which means cold or freezing, and "genes" meaning born or produced.

The field of Cryogenics advanced when, during World War II, scientists found that metals frozen to low temperatures showed more resistance to wear. Based on this theory of cryogenic hardening, the commercial cryogenic processing industry was founded in the sixties by Ed Busch who passed away in December 2003. With a background in the heat treating industry, Mr. Busch founded a company in Detroit, MI called CryoTech during 1966 and experimented with the possibility of increasing the life of metal tools to anywhere between 200%-400% of the original life expectancy using cryogenic tempering instead of heat treating. The theory was based on how heat treating metal works (the temperatures are lowered to room temperature from a high degree causing certain strength increases in the molecular structure to occur) and supposed that continuing the descent would allow for further strength increases. Using liquid nitrogen, CryoTech formulated the first early version of the cryogenic processor. Unfortunately for the newly-born industry, the results were unstable, as components sometimes experienced thermal shock when they were cooled too fast. (Some components in early tests even shattered because of the ultra-low temperatures.) Luckily, with the use of applied research, the field has improved significantly since the invention of the modern computer, which was coupled to the cryogenic processor in order to create more stable results.

Another use of cryogenics is cryogenic fuels. Cryogenic fuels, mainly oxygen and hydrogen, have been used as rocket fuels. For example, NASA's workhorse space shuttle uses cryogenic oxygen and hydrogen fuels as its primary means of getting into orbit.

Also, recent research regarding superconductivity at low temperatures has been called cryoelectronics by some research firms. They term the utilization of these sciences as cryotronics.

Cryogens, like liquid nitrogen, are further used for specialty chilling and freezing applications. Some chemical reactions, like those used to produce the active ingredients for the popular statin drugs, must occur at low temperatures of approximately -100C. Special cryogenic chemical reactors are used to remove reaction heat and provide a low temperature environment. The freezing of foods and biotechnology products, like vaccines, requires nitrogen in blast freezing or immersion freezing systems.

Introduction

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 begins is not well defined. The workers at the National Bureau of Standards at Boulder, colorado, have chosen to consider the field of cryogenics as that involving temperatures below –150.0C (123.0K). This is a logical dividing line, since the normal boiling points of the so-called permanent gases, such as helium, hydrogen, neon, nitrogen, oxygen, and air, lie below -150.0C while the Freon refrigerants, hydrogen sulfide, and other common refrigerants all boil at temperatures above –150.0C.

See also

• cryogenic processor
• cryogenic tempering
• 300 Below
• absolute zero
• coldest temperature achieved on earth
• refrigeration
• superfluidity
• superconductivity
• quantum hydrodynamics
• cryocoolers
• important publications in cryogenics

External links

• Cryogenics