When is cryogenics used

The word originates from the Greek words 'kryos' meaning "frost" and 'genic' meaning "to produce. However, Prof. Kamerlingh Onnes of the University of Leiden in the Netherlands first used the word in to describe the art and science of producing much lower temperatures.

He used the word in reference to the liquefaction of permanent gases such as oxygen, nitrogen, hydrogen, and helium. Oxygen had been liquefied at C a few years earlier in , and a race was in progress to liquefy the remaining permanent gases at even lower temperatures.

The techniques employed in producing such low temperatures were quite different from those used somewhat earlier in the production of artificial ice. In particular, efficient heat exchangers are required to reach very low temperatures.

Over the years the term cryogenics has generally been used to refer to temperatures below approximately C.

According to the laws of thermodynamics, there exists a limit to the lowest temperature that can be achieved, which is known as absolute zero. Molecules are in their lowest, but finite, energy state at absolute zero. Such a temperature is impossible to reach because the input power required approaches infinity.

However, temperatures within a few billionths of a degree above absolute zero have been achieved. Absolute zero is the zero of the absolute or thermodynamic temperature scale.

It is equal to The metric or SI International System absolute scale is known as the Kelvin scale whose unit is the kelvin not Kelvin which has the same magnitude as the degree Celsius. Thus, 0 C equals The English absolute scale, known as the Rankine scale, uses the symbol R and has an increment the same as that of the Fahrenheit scale.

Cryogenic liquids and their associated cold vapours and gases can produce effects on the skin similar to a thermal burn. Brief exposures that would not affect skin on the face or hands can damage delicate tissues such as the eyes. Prolonged exposure of the skin or contact with cold surfaces can cause frostbite.

The skin appears waxy yellow. There is no initial pain, but there is intense pain when frozen tissue thaws. Unprotected skin can stick to metal that is cooled by cryogenic liquids. The skin can then tear when pulled away. Even non-metallic materials are dangerous to touch at low temperatures. Prolonged breathing of extremely cold air may damage the lungs. When cryogenic liquids form a gas, the gas is very cold and usually heavier than air. This cold, heavy gas does not disperse very well and can accumulate near the floor.

Even if the gas is non-toxic, it displaces air. When there is not enough air or oxygen, asphyxiation and death can occur. Oxygen deficiency is a serious hazard in enclosed or confined spaces. Small amounts of liquid can evaporate into very large volumes of gas. Each gas can cause specific health effects. For example, liquid carbon monoxide can release large quantities of carbon monoxide gas, which can cause death almost immediately. Refer to the material safety data sheet for information about the toxic hazards of a particular cryogen.

Several types of situations exist that may result in a flammability hazard including: fire, oxygen-enriched air, liquid oxygen, and explosion due to rapid expansion. Flammable gases such as hydrogen, methane, liquefied natural gas and carbon monoxide can burn or explode. Hydrogen is particularly hazardous. The idea of vacuum insulation had been used by Dewar and others as early as and he went on to show how he could obtain significant reduction up to 6 times in heat influx by introducing into the vacuum space powders such as charcoal, lamp black, silica, alumina and bismuth oxide — the first vacuum insulated powder insulations.

He also found that three turns of aluminum sheet was not as good as silvered surfaces. Had he gone on to apply further turns of aluminum, he would have discovered the principle of multi-layer insulation, which is superior to silvering. Nevertheless, his discovery of silvering as an effective means of reducing the radiated heat flux component was a breakthrough.

From , the glass dewar flask quickly became the standard container for cryogenic liquids, leading to the successful liquefaction of hydrogen and helium in later years. Dewar had considerable difficulty in finding competent glass blowers willing to undertake the construction of his double-walled vessels, and was forced to get them made in Germany.

By , a ready supply became available. The discovery by German glassblower Muller of Coburn that a silvered vacuum flask could also be used for keeping milk hot overnight for feeding his baby, led to a major commercial development, the Thermos Flasche, for keeping liquids hot.

Dewar never patented his silvered vacuum flask and never benefited financially from his invention. This simple device enables the majority of ambient temperature radiation funneling down the neck to be absorbed by heating the cold vapor rather than by evaporating the liquid, thereby reducing the evaporation rate in a liquid helium cryostat or dewar by a factor of three or more.

This device is also applicable to the large-scale storage of cryogenic liquids, for example via the use of a suspended deck in LNG storage tanks. Vapor-cooled necks, USA and UK Further study of the convection in dewar necks led to the discovery of boundary layer flows with high heat transfer capability to the neck wall, together with reverse flow in the core of the vapor column. Quantifying these studies led to design criteria for the geometry of vapor-cooled neck walls to achieve minimum helium evaporation rate.

These criteria are now in standard use for the design of containers for all cryogenic liquids. Since then, MLI has become the standard insulation in most cryogenic liquid storage vessels and tanks. LNG tankers; trials by UK team While the improvement in performance of insulations has led to many applications, the scale of operation has increased dramatically, particularly with liquid hydrocarbons.

The breakthrough in LNG technology came in with the conversion in the U. These led directly to the development of the ,m 3 LNG tankers operating around the world today. Refrigeration breakthroughs Cold engines are the enablers of low temperatures, and there have been many breakthroughs including:. Research on cryotherapy is still very new, and benefits have not been fully researched or understood.

The cryo-preservation of animals and humans is called cryonics. Researchers in this field give their subjects hope that by freezing their body they may be able to resuscitate them in the future. Hundreds of people and their pets! The science of cryonics is not proven and most scientists are dubious of the claims.

As technology rapidly evolves areas of cryogenics will continue to develop and eventually expand to more applications. It is important that all applications handling, studying and using cryogenic liquids use the proper safety precautions and gas level monitors and are able to ensure accurate monitoring of gas concentrations.

Learn more about cryogenic safety here. Close menu. What is Cryogenics? What Is Cryogenics Used For? Applications and uses: Cryosurgery Cryosurgery is a type of surgery that uses cryogenic temperatures to eliminate unwanted tissue or tumors. Cryoelectronics The ultra-frozen temperatures that cryogenic fluids can provide offer the ability for electrons in materials to move freely with little resistance.

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 falls under this category Supercooling as applied to biological systems Food Preservation To preserve packaged foods such as produce, the food items can be sprayed with liquid nitrogen to absorb the heat within the produce.

Transportation of Gases Cryogenics is also used to transport gases that are not typically cryogenic.