Coolant

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Coolant

A coolant is a fluid which flows through a device in order to prevent its overheating, transferring the heat produced by the device to other devices that utilize or dissipate it. An ideal coolant has high thermal capacity, low viscosity

Viscosity

Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness"....
, is low-cost, and is chemically inert, neither causing nor promoting corrosion

Corrosion

Corrosion means the breaking down of essential properties in a material due to chemical reactions with its surroundings. In the most common use of the word, this means a loss of electrons of metals reacting with water and oxygen....
of the cooling system. Some applications also require the coolant to be an electrical insulator

Electrical insulation

An insulator, also called a dielectric, is a material that resists the flow of electric current. An insulating material has atoms with tightly bonded valence electrons....
.

While the term coolant is commonly used in automotive, residential and commercial temperature-control applications, in industrial processing, heat transfer fluid is one technical term more often used, in high temperature as well as low temperature manufacturing applications.

The coolant can either keep its phase and stay liquid or gaseous, or can undergo a phase change, with the latent heat

Latent heat

In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a chemical substance during a change of state of matter , or a phase transition....
adding to the cooling efficiency.

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Encyclopedia

Viscosity

Corrosion

Electrical insulation

Latent heat

Refrigerant

Gases

Air

Earth's atmosphere

The Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by the Earth's gravity. Dry air contains roughly 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% Carbon dioxide in the Earth's atmosphere, and trace amounts of other gases....
is a common form of a coolant. Air cooling uses either convective

Convection

Convection in the most general terms refers to the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer....
airflow (passive cooling), or a forced circulation using fans

Fan (mechanical)

A mechanical fan is an electricity powered device used to produce an airflow for the purpose of creature comfort , Ventilation , exhaust, or any other gaseous transport....
.

Hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
, the first hydrogen-cooled turbogenerator

Hydrogen-cooled turbogenerator

A hydrogen-cooled turbo generator is a turbo generator with gaseous hydrogen as a coolant. Hydrogen-cooled turbo generators are designed to provide a low-drag atmosphere and cooling for single-shaft and combined-cycle applications in combination with steam turbines, because of the thermal conductivity of hydrogen gas this is the most common...
went into service with gaseous hydrogen as a coolant in the rotor and the stator in 1937 at Dayton

Dayton, Ohio

Dayton is a city in and the county seat of Montgomery County, Ohio, Ohio, United States, in the southwestern part of the state. The population was 166,179 at the United States Census, 2000....
, Ohio,by the Dayton Power & Light Co, because of the thermal conductivity of hydrogen gas this is the most common type in its field today.

Inert gas

Inert gas

An inert gas is any gas that is not reactive with elements.Like the noble gases an inert gas is not necessarily elemental and are often compound gases....
es are frequently used as coolants in gas-cooled nuclear reactor

Nuclear reactor

A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate, as opposed to a nuclear bomb, in which the chain reaction occurs in a fraction of a second and is uncontrolled causing an explosion....
s. Helium

Helium

Helium is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas group in the periodic table and whose atomic number is 2....
is the most favored coolant due to its low tendency to absorb neutrons and become radioactive. Nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
and carbon dioxide

Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
are frequently used as well.

Sulfur hexafluoride

Sulfur hexafluoride

Sulfur hexafluoride is an inorganic compound with the formula . It is a colorless, odorless, non-toxicity and non-flammable gas . has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom....
is used for cooling and insulating of some high-voltage power systems (circuit breaker

Circuit breaker

A circuit breaker is an automatically-operated Electricity switch designed to protect an Electrical network from damage caused by Overcurrent or short circuit....
s, switch

Switch

In electronics, a switch is an electrical component which can break an electrical circuit, interrupting the Electric current or diverting it from one conductor to another....
es, some transformer

Transformer

A transformer is a device that transfers electrical energy from one electrical network to another through inductive coupling conductors — the transformer's coils or "windings"....
s, etc.).

Steam

Steam

In physical chemistry, and in engineering, steam refers to vaporized water. It is a pure, completely invisible gaseous phase . At standard temperature and pressure, pure steam occupies about 1,600 times the volume of an equal mass of liquid water....
can be used where high specific heat capacity

Specific heat capacity

Specific heat capacity, also known simply as specific heat, is the measure of the energy required to increase the temperature of a of a substance by a certain Celsius#Temperatures_and_intervals....
is required in gaseous form and the corrosive properties of hot water are accounted for.

Liquids

The most common coolant is water

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
. Its high heat capacity and low cost makes it a suitable heat-transfer medium. It is usually used with additives, like corrosion inhibitor

Corrosion inhibitor

A corrosion inhibitor is a chemical compound that, when added to a fluid or gas, decreases the corrosion rate of a metal or an alloy.The effectiveness, or corrosion inhibition efficiency, of a corrosion inhibitor is a function of many factors like: fluid composition, quantity of water, flow regime.......
s and antifreezes. Antifreeze, a solution of a suitable organic chemical (most often ethylene glycol

Ethylene glycol

Ethylene glycol is an alcohol with two -OH groups , a chemical compound widely used as an automobile antifreeze. In its pure form, it is an odorless, colorless, syrupy, sweet tasting, toxic liquid....
, diethylene glycol

Diethylene glycol

Diethylene glycol is an organic compound described by the structural chemical formula HO-CH2-CH2-O-CH2-CH2-OH....
, or propylene glycol

Propylene glycol

Propylene glycol, known also by the systematic name propane-1,2-diol, is an organic compound , usually a faintly sweet, and colorless clear viscous liquid that is hygroscopic and miscible with water, acetone, and chloroform....
) in water, is used when the water-based coolant has to withstand temperatures below 0 °C, or when its boiling point has to be raised.

Very pure deionized water, due to its relatively low electrical conductivity

Electrical conductivity

Electrical conductivity or specific conductance is a measure of a material's ability to electrical conduction an electric current. When an electrical potential difference is placed across a conductor, its movable charges flow, giving rise to an electric current....
, is used to cool some electrical equipment, often high-power transmitters.

Heavy water

Heavy water

Heavy water is water that contains a higher proportion than normal of the isotope deuterium, as deuterium oxide, D2O or ?H2O, or as deuterium protium oxide, HDO or ?H?HO....
is used in some nuclear reactors; it also serves as a neutron moderator

Neutron moderator

In nuclear engineering, a neutron moderator is a medium which reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
.

Polyalkylene Glycol or PAG's are used as high temperature, thermally stable heat transfer fluids exhibiting strong resistance to oxidation. Modern PAG's can also be non-toxic and non-hazardous

Oil

Oil

An oil is a chemical substance that is in a viscosity liquid state at room temperature or slightly warmer, and is both hydrophobic and lipophilic ....
s are used for applications where water is unsuitable. With higher boiling points than water, oils can be raised to considerably higher temperatures (above 100 degrees Celsius) without introducing high pressures within the container or loop system in question.

Mineral oil
Mineral oil

Mineral oil or liquid petroleumis a by-product in the distillation of petroleum to produce gasoline and other petroleum based products from crude oil....
s serve as both coolants and lubricants in many mechanical gears. Castor oil
Castor oil

Castor oil is a vegetable oil obtained from the castor bean . Castor oil is a colorless to very pale yellow liquid with mild or no odor or taste....
is also used. Due to their high boiling points, mineral oils are used in portable electric radiator-style space heaters in residential applications, and in closed-loop systems for industrial process heating and cooling.
Silicone
Silicone

Silicones are largely inert, man-made compounds with a wide variety of forms and uses. Typically heat-resistant, nonstick, and rubberlike, they are commonly used in cookware, medicine, sealants, adhesives, lubricants, and insulation....
oils are favored for their wide range of operating temperatures. However their high cost limits their applications.
Fluorocarbon
Fluorocarbon

Fluorocarbons, sometimes referred to as perfluorocarbons, are organofluorine compounds that contain only carbon and fluorine bonded together in strong carbon?fluorine bonds....
oils are used for the same reasons.
High-power electric transformer
Transformer

A transformer is a device that transfers electrical energy from one electrical network to another through inductive coupling conductors — the transformer's coils or "windings"....
s use transformer oil
Transformer oil

Transformer oil, or insulating oil, is usually a highly-refining mineral oil that is stable at high temperatures and has excellent electrical insulating properties....
for cooling and additional electric insulation.

Cutting fluid

Cutting fluids are various fluids that are used in machining to cool and lubricate the cutting tool. There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, and mists....
is a coolant that also serves as a lubricant

Lubricant

A lubricant is a substance introduced between two moving surfaces to reduce the friction between them, improving efficiency and reducing wear....
for metal-shaping machine tool

Machine tool

A machine tool is a powered mechanical device, typically used to fabricate metal components of machines by machining, which is the selective removal of metal....
s.

Liquid fusible alloy

Fusible alloy

A fusible alloy, usually eutectic alloy is capable of being heat of fusion, as well as being liquefied by heat.Sometimes the term "fusible alloy" is used to describe alloys with a melting point below ....
s can be used as coolants in applications where high temperature stability is required, eg. some fast breeder nuclear reactor

Nuclear reactor

Sodium

Sodium is an element which has the symbol Na , atomic number 11, atomic mass 23 amu , and a common oxidation number +1. Sodium is a soft, silvery white, highly reactive element and is a member of the alkali metals within "group 1" ....
or sodium-potassium

Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
alloy NaK

NaK

NaK is a sodium - potassium alloy usually liquid at room temperature. Various commercial grades are available. NaK is highly reactive with air or water and must be handled with special precautions....
are frequently used; in special cases lithium

Lithium

Lithium is a chemical element with the symbol Li and atomic number 3. It is a soft alkali metal with a silver-white color. Under standard conditions for temperature and pressure, it is the lightest metal and the least dense solid element....
can be employed. Another liquid metal used as a coolant is lead

Lead

Lead is a main-group Chemical element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metal ....
, in eg. lead cooled fast reactor

Lead cooled fast reactor

The lead-cooled fast reactor is a nuclear power Generation IV reactor that features a fast neutron spectrum, molten lead or lead-bismuth eutectic coolant, and a closed Nuclear fuel cycle....
s, or a lead-bismuth

Bismuth

Bismuth is a chemical element that has the symbol Bi and atomic number 83. This heavy, brittle, white crystalline trivalent poor metal has a pink tinge and chemically resembles arsenic and antimony....
alloy. Some early fast neutron reactor

Fast neutron reactor

A fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons....
s used mercury

Mercury (element)

Mercury , also called quicksilver or hydrargyrum , is a chemical element with the symbol Hg and atomic number 80. A heavy, silvery d-block metal, mercury is one of six elements that are liquid at or near room temperature and pressure....
.

For very high temperature applications, eg. molten salt reactor

Molten salt reactor

A molten salt reactor is a type of nuclear reactor where the primary coolant is a molten salt. There have been many designs put forward for use of this type of reactor as a nuclear power plant and a few prototypes built....
s or very high temperature reactor

Very high temperature reactor

The Very High Temperature Reactor is a Generation IV reactor concept that uses a graphite-neutron moderator nuclear reactor with a once-through uranium fuel cycle....
s, molten salt

Salt

A salt, in chemistry, is defined as the product formed from the neutralisation reaction of acids and base . Salts are ionic compounds composed of cations and anions so that the product is electrically electric charge ....
s can be used as coolants. One of the possible combinations is the mix of sodium fluoride

Sodium fluoride

Sodium fluoride is the chemical compound with the chemical formula NaF. This colourless solid is the main source of the fluoride ion in diverse applications....
and sodium tetrafluoroborate

Sodium tetrafluoroborate

Sodium tetrafluoroborate is a Compound with formula NaBF4.It is a source of tetrafluoroborate anion....
(NaF-NaBF₄).

Freon

Freon

Freon is DuPont's trade name for its odorless, colorless, nonflammable, and noncorrosive chlorofluorocarbon and hydrochlorofluorocarbon refrigerants, which are used in air conditioning, refrigeration and some automatic fire-fighting systems....
s were frequently used for immersive cooling of eg. electronics.

Refrigerant

Refrigerant

A refrigerant is a compound used in a heat engine that undergoes a phase change from a gas to a liquid and back. The two main uses of refrigerants are refrigerators/freezers and air conditioners ....
s are coolants used for reaching low temperatures by undergoing phase change between liquid and gas. Halomethane

Halomethane

Halomethane compounds are molecules of methane with one or more of the hydrogen atoms replaced with halogen atoms. The halogens are found in group 17 of the periodic table of the Chemical element....
s were frequently used, most often R-12

Dichlorodifluoromethane

Dichlorodifluoromethane , usually sold under the brand name Freon-12, is a chlorofluorocarbon halomethane, commonly known as CFC, used as a refrigerant and aerosol spray#Propellant....
and R-22

Chlorodifluoromethane

Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon . It is better known under its code names of HCFC-22, R-22, Genetron 22 or Freon 22, and is commonly used in air conditioning applications, such as residential split systems in the US, rooftop units and window air conditioners....
, but due to environmental concerns are being phased out, often with liquified propane

Liquified petroleum gas

Liquefied petroleum gas is a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing chlorofluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer....
or other haloalkanes like R-134a. Anhydrous ammonia

Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
is frequently used in large commercial systems, and sulfur dioxide

Sulfur dioxide

Sulfur dioxide is the chemical compound with the formula SO2. It is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide....
was used in early mechanical refrigerators. Carbon dioxide

Carbon dioxide

Heat pipe

A heat pipe is a heat transfer mechanism that can transport large quantities of heat with a very small difference in temperature between the hotter and colder interfaces....
s are a special application of refrigerants.

Liquid gases are used as coolants for cryogenic applications, including cryo-electron microscopy

Cryo-electron microscopy

Electron cryomicroscopy is a form of electron microscopy where the sample is studied at cryogenic temperatures . CryoEM is developing popularity in structural biology....
, overclocking

Overclocking

Overclocking is the process of running a computer hardware at a higher clock rate than it was designed for or was specified by the manufacturer, usually practiced by personal computer enthusiasts seeking an increase in the performance of their computers....
of computer processors, applications using superconductors, or extremely sensitive sensor

Sensor

A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube....
s and very low-noise

Noise

In common use, the word noise means unwanted sound or noise pollution. In electronics noise can refer to the electronic signal corresponding to acoustic noise or the electronic signal corresponding to the noise commonly seen as 'Noise ' on a degraded television or video image....
amplifier

Amplifier

Generally, an amplifier or simply amp, is any machine that changes, usually increases, the amplitude of a Signal . The "signal" is usually voltage or current....
s. The most common and least expensive coolant in use is liquid nitrogen

Liquid nitrogen

Liquid nitrogen is a liquefied atmospheric gas produced industrially in large quantities by fractional distillation of liquid air. It is pure nitrogen in a liquid state at very low temperature....
which boils at about -196 C (77K). Liquid air

Liquid air

Liquid air is air that has been cooled to very low temperatures so that it has condensed to a liquid. At room temperature, it must be kept in a Dewar flask....
is used to lower degree, due to its oxygen content which makes it prone to cause fire or explosions when in contact with combustible materials. Lower temperatures can be reached using liquefied neon

Neon

Neon is the chemical element that has the symbol Ne and atomic number 10. Although a very common element in the universe, it is rare on Earth....
which boils at about -246 C. The lowest temperatures, used for the most powerful superconducting magnet

Superconducting magnet

A superconducting magnet is an electromagnet that is built using superconductivity coils. They must be cooled to cryogenic temperatures during operation....
s, are reached using liquid helium

Liquid helium

Helium exists in liquid form only at very low temperatures. The boiling point and critical point depend on the isotope of the helium; see the table below for values....
.

Fuel

Fuel

Fuel is any material that is burned or altered in order to obtain energy and to heat or to move an object. Fuel releases its energy either through a chemical reaction means, such as combustion, or nuclear means, such as nuclear fission or nuclear fusion....
s are frequently used as coolants for engines. A cold fuel flows over some parts of the engine, absorbing its waste heat and being preheated before combustion. Kerosene

Kerosene

Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin, is a combustible hydrocarbon liquid....
and other jet fuel

Jet fuel

Jet fuel is a type of aviation fuel designed for use in aircraft powered by Aircraft engine#Gas turbine engine configurations. It is clear to straw colored....
s frequently serve in this role in aviation engines and liquid hydrogen

Liquid hydrogen

Liquid hydrogen is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecule H2 form.To exist as a liquid, H2 must be pressurized and cooled to a very low temperature, 20.28 K ....
is used both as a fuel and as a coolant to cool nozzles and chambers of rocket engine

Rocket engine

A rocket engine or simply rocket is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive Jet ....
s.

Coolant

Gases

Liquids

See also

External links