Cryogenics

Study of the production and behaviour of materials at very low temperatures

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For cryopreservation of humans, see Cryonics . For the band, see Cryogenic (band)

This is a diagram of an infrared space telescope, that needs a cold mirror and instruments. One instrument needs to be even colder, and it has a cryocooler. The instrument is in region 1 and its cryocooler is in region 3 in a warmer region of the spacecraft (see MIRI (Mid-Infrared Instrument) or James Webb Space Telescope). A medium-sized dewar is being filled with liquid nitrogen by a larger cryogenic storage tank.

In physics, cryogenics is the production and behaviour of materials at very low temperatures.

The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of "cryogenics" and "cryogenic" by accepting a threshold of 120 K (−153 °C) to distinguish these terms from the conventional refrigeration.[1][2][3][4] 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 normal air) lie below 120 K, while the Freon refrigerants, hydrocarbons, and other common refrigerants have boiling points above 120 K.[5][6]

Discovery of superconducting materials with critical temperatures significantly above the boiling point of nitrogen has provided new interest in reliable, low cost methods of producing high temperature cryogenic refrigeration. The term "high temperature cryogenic" describes temperatures ranging from above the boiling point of liquid nitrogen, −195.79 °C (77.36 K; −320.42 °F), up to −50 °C (223 K; −58 °F).[7] The discovery of superconductive properties is first attributed to Heike Kamerlingh Onnes on July 10, 1908. The discovery came after the ability to reach a temperature of 2 K. These first superconductive properties were observed in mercury at a temperature of 4.2 K.[8]

Cryogenicists use the Kelvin or Rankine temperature scale, both of which measure from absolute zero, rather than more usual scales such as Celsius which measures from the freezing point of water at sea level[9][10] or Fahrenheit which measures from the freezing point of a particular brine solution at sea level.[11][12]

Definitions and distinctions

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Cryogenics

The branches of engineering that involve the study of very low temperatures (ultra low temperature i.e. below 123 K), how to produce them, and how materials behave at those temperatures.

Cryobiology

The branch of biology involving the study of the effects of low temperatures on organisms (most often for the purpose of achieving cryopreservation). Other applications include Lyophilization (freeze-drying) of pharmaceutical[13] components and medicine.

Cryoconservation of animal genetic resources

The conservation of genetic material with the intention of conserving a breed. The conservation of genetic material is not limited to non-humans. Many services provide genetic storage or the preservation of stem cells at birth. They may be used to study the generation of cell lines or for stem-cell therapy.[14]

Cryosurgery

The branch of surgery applying cryogenic temperatures to destroy and kill tissue, e.g. cancer cells. Commonly referred to as Cryoablation.[15]

Cryoelectronics

The study of electronic phenomena at cryogenic temperatures. Examples include superconductivity and variable-range hopping.

Cryonics

Cryopreserving humans and animals with the intention of future revival. "Cryogenics" is sometimes erroneously used to mean "Cryonics" in popular culture and the press.[16]

Etymology

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The word cryogenics stems from Greek κρύος (cryos) – "cold" + γενής (genis) – "generating".

Cryogenic fluids

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Cryogenic fluids with their boiling point in Kelvin[17] and degree Celsius.

Fluid Boiling point (K) Boiling point (°C) Helium-3 3.19 -269.96 Helium-4 4.214 -268.936 Hydrogen 20.27 -252.88 Neon 27.09 -246.06 Nitrogen 77.09 -196.06 Air 78.8 -194.35 Fluorine 85.24 -187.91 Argon 87.24 -185.91 Oxygen 90.18 -182.97 Methane 111.7 -161.45

Industrial applications

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Catalogue image of a cryogenic valve

Cryogenic valves in situ, with condensed atmospheric humidity

Liquefied gases, such as liquid nitrogen and liquid helium, are used in many cryogenic applications. 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.

These liquids may be stored in Dewar flasks, which are double-walled containers with a high vacuum between the walls to reduce heat transfer into the liquid. Typical laboratory Dewar flasks are spherical, made of glass and protected in a metal outer container. Dewar flasks for extremely cold liquids such as liquid helium have another double-walled container filled with liquid nitrogen. Dewar flasks are named after their inventor, James Dewar, the man who first liquefied hydrogen. Thermos bottles are smaller vacuum flasks fitted in a protective casing.

Cryogenic barcode labels are used to mark Dewar flasks containing these liquids, and will not frost over down to −195 degrees Celsius.[18]

Cryogenic transfer pumps are the pumps used on LNG piers to transfer liquefied natural gas from LNG carriers to LNG storage tanks, as are cryogenic valves.

Cryogenic processing

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The field of cryogenics advanced during World War II when 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 1966 by Bill and Ed Busch. With a background in the heat treating industry, the Busch brothers founded a company in Detroit called CryoTech in 1966.[19] Busch originally experimented with the possibility of increasing the life of metal tools to anywhere between 200% and 400% of the original life expectancy using cryogenic tempering instead of heat treating.[citation needed] This evolved in the late 1990s into the treatment of other parts.

Cryogens, such as 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 −100 °C (−148 °F). 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. Certain soft or elastic materials become hard and brittle at very low temperatures, which makes cryogenic milling (cryomilling) an option for some materials that cannot easily be milled at higher temperatures.

Cryogenic processing is not a substitute for heat treatment, but rather an extension of the heating–quenching–tempering cycle. Normally, when an item is quenched, the final temperature is ambient. The only reason for this is that most heat treaters do not have cooling equipment. There is nothing metallurgically significant about ambient temperature. The cryogenic process continues this action from ambient temperature down to −320 °F (140 °R; 78 K; −196 °C). In most instances the cryogenic cycle is followed by a heat tempering procedure. As all alloys do not have the same chemical constituents, the tempering procedure varies according to the material's chemical composition, thermal history and/or a tool's particular service application.

The entire process takes 3–4 days.

Fuels

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Another use of cryogenics is cryogenic fuels for rockets with liquid hydrogen as the most widely used example. Liquid oxygen (LOX) is even more widely used but as an oxidizer, not a fuel. NASA's workhorse Space Shuttle used cryogenic hydrogen/oxygen propellant as its primary means of getting into orbit. LOX is also widely used with RP-1 kerosene, a non-cryogenic hydrocarbon, such as in the rockets built for the Soviet space program by Sergei Korolev.

Russian aircraft manufacturer Tupolev developed a version of its popular design Tu-154 with a cryogenic fuel system, known as the Tu-155. The plane uses a fuel referred to as liquefied natural gas or LNG, and made its first flight in 1989.[20]

Other applications

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Astronomical instruments on the Very Large Telescope are equipped with continuous-flow cooling systems.[21]

Some applications of cryogenics:

• Nuclear magnetic resonance (NMR) is one of the most common methods to determine the physical and chemical properties of atoms by detecting the radio frequency absorbed and subsequent relaxation of nuclei in a magnetic field. This is one of the most commonly used characterization techniques and has applications in numerous fields. Primarily, the strong magnetic fields are generated by supercooling electromagnets, although there are spectrometers that do not require cryogens. In traditional superconducting solenoids, liquid helium is used to cool the inner coils because it has a boiling point of around 4 K at ambient pressure. Cheap metallic superconductors can be used for the coil wiring. So-called high-temperature superconducting compounds can be made to super conduct with the use of liquid nitrogen, which boils at around 77 K.
• Magnetic resonance imaging (MRI) is a complex application of NMR where the geometry of the resonances is deconvoluted and used to image objects by detecting the relaxation of protons that have been perturbed by a radio-frequency pulse in the strong magnetic field. This is most commonly used in health applications.
• In large cities, it is difficult to transmit power by overhead cables, so underground cables are used. But underground cables get heated and the resistance of the wire increases, leading to waste of power. Superconductors could be used to increase power throughput, although they would require cryogenic liquids such as nitrogen or helium to cool special alloy-containing cables to increase power transmission. Several feasibility studies have been performed and the field is the subject of an agreement within the International Energy Agency.

Cryogenic gases delivery truck at a supermarket, Ypsilanti, Michigan

• Cryogenic gases are used in transportation and storage of large masses of frozen food. When very large quantities of food must be transported to regions like war zones, earthquake hit regions, etc., they must be stored for a long time, so cryogenic food freezing is used. Cryogenic food freezing is also helpful for large scale food processing industries.
• Many infrared (forward looking infrared) cameras require their detectors to be cryogenically cooled.
• Certain rare blood groups are stored at low temperatures, such as −165 °C, at blood banks.
• Cryogenics technology using liquid nitrogen and CO2 has been built into nightclub effect systems to create a chilling effect and white fog that can be illuminated with colored lights.
• Cryogenic cooling is used to cool the tool tip at the time of machining in manufacturing process. It increases the tool life. Oxygen is used to perform several important functions in the steel manufacturing process.
• Many rockets and lunar landers use cryogenic gases as propellants. These include liquid oxygen, liquid hydrogen, and liquid methane.
• By freezing the automobile or truck tire in liquid nitrogen, the rubber is made brittle and can be crushed into small particles. These particles can be used again for other items.
• Experimental research on certain physics phenomena, such as spintronics and magnetotransport properties, requires cryogenic temperatures for the effects to be observed.
• Certain vaccines must be stored at cryogenic temperatures. For example, the Pfizer–BioNTech COVID-19 vaccine must be stored at temperatures of −90 to −60 °C (−130 to −76 °F). (See cold chain.)[22]

Production

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Cryogenic cooling of devices and material is usually achieved via the use of liquid nitrogen, liquid helium, or a mechanical cryocooler (which uses high-pressure helium lines). Gifford-McMahon cryocoolers, pulse tube cryocoolers and Stirling cryocoolers are in wide use with selection based on required base temperature and cooling capacity. The most recent development in cryogenics is the use of magnets as regenerators as well as refrigerators. These devices work on the principle known as the magnetocaloric effect.

Detectors

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There are various cryogenic detectors which are used to detect particles.

For cryogenic temperature measurement down to 30 K, Pt100 sensors, a resistance temperature detector (RTD), are used. For temperatures lower than 30 K, it is necessary to use a silicon diode for accuracy.

See also

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References

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Further reading

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• Haselden, G. G. (1971), Cryogenic fundamentals, Academic Press, New York, ISBN 0-12-330550-0.

Cryogenics produces and studies materials in extremely cold temperatures. Ultra-cold temperatures change the chemical properties of materials. This has become an area of study for researchers who examine different materials as they transition from a gas to a liquid to a solid state. These studies have led to advances in not only our understanding of different materials but the creation of entirely new technologies and industries.

The temperature of any material is the measure of the energy that it contains. Rapidly moving molecules have a higher temperature than slower-moving molecules.

For example, while water transforms from a liquid to a solid at 32° F (0° C), cryogenic temperatures range much lower; from -150°C to -273° C. The temperature -273° C is the absolute lowest that can be achieved. At this temperature, the actions of all molecules stop, causing the molecules to be at the lowest possible state of energy.

Liquid gases at or below -150° C are also used to freeze other materials. Once a gas begins to liquefy, the environment is considered a cryogenic one. The most common gases that are turned into liquid for cryogenics are oxygen, nitrogen, hydrogen and helium.

History of Cryogenics

The word cryogenics comes from the Greek word “Kryos,” which means cold. This combined with the abbreviated English word “to generate” make the word we know as cryogenics.

Temperatures that are very cold are not measured in degrees Fahrenheit or Celsius but in Kelvins. Kelvins use the unit symbol K. It is named after Baron Kelvin who believed that at very low temperatures a new scale was needed that was not measured by the material state change of water like Fahrenheit or Celsius. Zero degrees Kelvin (0 K) is the theoretically coldest possible temperature.

In 1877 Rasul Pictet and Louis Cailletet liquefied oxygen for the first time, both using different methods for the process. Eventually, a third method of liquefying oxygen was discovered, and at this point in history oxygen was able to be liquefied at 90 K. Soon after, liquid nitrogen was achieved at 77 K. Scientists all over the world began competing to lower the temperature of matter to absolute zero.

The next breakthrough came in 1898 when James DeWar liquefied hydrogen at 20 K. This presented a new problem to researchers, as 20 K is also at a boiling temperature. However, this presented a further issue on how to handle and store gases at such temperatures. Hence the creation of DeWar flasks, which are used to store gases today.

The last major advance in the cryogenics industry came in 1908 when the physicist Heike Kamerling Onnes liquefied Helium at 4.2 K and then 3.2 K.  The advances in cryogenics following this development have been much smaller because it is thermodynamic law that you can approach absolute zero, but never actually reach it. Technology has advanced much more since this last major discovery, and we can now freeze materials within very small distances from absolute zero, yet scientists still have not been able to break thermodynamic law where every particle has zero energy.

What Is Cryogenics Used For?

Cryogenics is used in a variety of low-temperature physics research and applications. It can be used to produce cryogenic fields for rockets, in MRI machines that use liquid helium and require cryogenic cooling, storing large quantities of food, special effects fog, recycling, freezing blood and tissue samples, and even cooling superconductors.

Applications and uses:

Cryosurgery

Cryosurgery is a minimally invasive surgical technique that involves the use of extreme cold to destroy or remove abnormal tissues, such as tumors or warts. The procedure involves applying a freezing agent, such as liquid nitrogen or argon gas, directly onto the targeted area. This causes the tissue to freeze and ultimately die, allowing the body to naturally eliminate the damaged cells.

The science behind cryosurgery is based on the principle of controlled tissue destruction by rapid freezing and thawing. When the targeted tissue is exposed to extreme cold, the water inside the cells freezes and expands, causing the cell walls to rupture and the cells to die. The body's immune system then works to remove the dead tissue, leaving healthy tissue behind.

Cryosurgery has many advantages over traditional surgical techniques. It is a minimally invasive procedure that can be performed on an outpatient basis, reducing the need for hospitalization and recovery time. It also results in less scarring and pain compared to traditional surgery, and has a lower risk of infection and complications.

Cryosurgery is commonly used in dermatology to treat skin conditions such as warts, actinic keratosis, and skin cancers. It is also used in other medical specialties such as gynecology, urology, and gastroenterology to treat various conditions.

Cryoelectronic Cooling

Cryoelectronic cooling is an innovative technology that has revolutionized the field of superconductivity and spacecraft design. It involves the use of extreme cold temperatures to enable electrons in materials to move freely with little resistance. This technology has many advantages over traditional cooling methods, such as liquid cooling, because it is more efficient, reliable, and cost-effective.

In superconductivity research, cryogenic engineering plays a vital role in maintaining the low temperatures required for superconducting materials to operate at their full potential. These materials have the ability to conduct electricity with zero resistance when they are cooled to near absolute zero (-273.15°C). By using cryoelectronic cooling, scientists are able to achieve and maintain these extremely low temperatures, allowing for the creation of more efficient and powerful superconductors.

In addition to superconductivity research, cryoelectronic cooling is also used in spacecraft design. Spacecraft that travel through outer space are exposed to extreme temperatures, which can cause damage to their electronic systems. Cryoelectronic cooling provides a reliable and efficient way to maintain the temperature of electronic systems in spacecraft, ensuring that they operate at optimal performance levels.

One of the major advantages of cryoelectronic cooling is that it is a highly efficient method of cooling, requiring only a small amount of energy to maintain the required low temperatures. This makes it an ideal choice for space applications, where energy conservation is critical. Additionally, cryoelectronic cooling is a reliable and cost-effective method of cooling, with few moving parts and minimal maintenance requirements.

Cryobiology

Cryobiology is the study of the effects of low temperatures on organisms. There are six major areas of cryobiology:

• The study of cold-adaptation of microorganisms, plants, animals and vertebrates
• Cryopreservation of cell tissues and embryos used in invitro fertilization
• Preservation of organs
• Lyophilization, the freeze-drying of pharmaceuticals
• Cryosurgery
• Supercooling as applied to biological systems

Food Preservation

Cryogenics keeps foods fresh without chemical risk. It is an effective technique for food preservation that is used to maintain the quality and freshness of various food products. 

Cryogenic preservation isn't just about cold - it freezes food products quickly so that it maintains its consistency, texture and taste. This makes cryogenic preservation an excellent option for high-value food items such as seafood, meat, and vegetables. This technique is particularly useful for maintaining the texture and quality of delicate food products that are easily damaged by other preservation methods such as heat treatment or dehydration.

Another benefit of cryogenic preservation is its ability to extend the shelf life of food products. By freezing food products at ultra-low temperatures, the growth of microorganisms that can cause spoilage and decay is inhibited, reducing the risk of foodborne illness and increasing the overall safety of the product. 

To preserve packaged foods such as produce, the food items are typically sprayed with liquid nitrogen to absorb the heat within the produce. The nitrogen quickly evaporates before the food is packaged. 

Transportation of Gases

Cryogenics is also used to transport gases that are not typically cryogenic. For example, using cryotechnology, gases can be transformed into liquids to make them easier to transport from one place to another. Take natural gas (LNG) which is a combination of ethane, methane and other gases. When these gases become liquefied, they take up far less space than if they remained gaseous. Therefore, transportation expenses become lower and the process becomes much easier.

Cryotherapy

Cryotherapy is a medical treatment that involves exposing the body to extremely cold temperatures. This can be achieved through various methods, including cryosaunas and cryospas, which allow individuals to stand in a chamber filled with cryogenic fluids for several minutes.

Proponents of cryotherapy claim that it offers numerous benefits to the body, including reducing inflammation, increasing energy, managing pain, and boosting metabolism. While research on cryotherapy is still relatively new, several studies have shown that it can be effective in reducing inflammation and pain in certain conditions, such as rheumatoid arthritis and fibromyalgia.

However, there are also potential risks associated with cryotherapy. Excessive exposure to cold temperatures can lead to hypothermia, which can be life-threatening. Additionally, cryotherapy can cause skin damage, particularly if the skin is wet or has open wounds.

Furthermore, while some individuals may experience immediate relief from pain and inflammation following cryotherapy, the long-term benefits of the treatment are still unclear. Some studies have suggested that cryotherapy may not be effective for all individuals and may even be harmful in some cases.

Cryonics

Cryonics is the process of cryo-preservation of humans or animals in the hope of reviving them at a later time when medical technology is advanced enough to cure the underlying cause of their death. Cryonics involves cooling the body to very low temperatures in a cryonic container filled with liquid nitrogen.

The cryopreservation process is performed immediately after death or sometimes even before if the individual is terminally ill and has chosen to undergo cryonic preservation. The goal of cryonics is to preserve the brain and other vital organs to enable future medical professionals to revive the person with their memories, consciousness, and personality intact.

While cryonics is a controversial topic, proponents argue that it offers hope for individuals who have been diagnosed with terminal illnesses or who may die from other causes. They argue that the advances in medical technology may one day make it possible to revive and cure the underlying cause of death, allowing individuals to continue living. Critics, however, argue that cryonics is a pseudoscience and that the chances of successfully reviving an individual are extremely slim. They also argue that the process of cryopreservation can cause significant damage to the body, and that it is unethical to offer false hope to individuals and their families.

What are the cryogenic fluids?

 Fluid Boiling Point (K) Boiling Point (°C) Helium-3 3.19 -269.96 Helium-4 4.214 -268.936 Hydrogen 20.27 -252.88 Neon 27.09 -246.06 Nitrogen 77.09 -196.06 Air 78.8 -194.35 Fluorine 85.24 -187.91 Argon 87.24 -185.91 Oxygen 90.18 -182.97 Methane 111.7 -161.45

What's Next for Cryogenics?

As technology rapidly evolves areas of cryogenics will continue to develop and eventually expand to more applications. While we can’t predict what developments will come next, what we do know is that safety around cryogenic fluids is a must, no matter which direction the research will progress.

It is important that all applications handling, studying and using cryogenic liquids use the proper safety precautions and cryogenic oxygen depletion monitors to ensure both safe and accurate monitoring of gas concentrations.

References

https://academickids.com/encyclopedia/index.php/Cryogenics

https://schoolworkhelper.net/cryogenics-history-overview/

https://www.encyclopedia.com/science-and-technology/physics/physics/cryogenics

https://www.azonano.com/article.aspx?ArticleID=5091

https://science.jrank.org/pages/1893/Cryogenics.html

https://www.thoughtco.com/cryogenics-definition-4142815

https://www.healthline.com/health/cryotherapy-benefits#benefits  

https://www.chilledcryospa.com/what-is-cryo

https://en.wikipedia.org/wiki/Cryosurgery

https://en.wikipedia.org/wiki/Cryoelectronics

https://en.wikipedia.org/wiki/Cryobiology

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