A coolant, or heat transfer fluid, 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, is low-cost, and is chemically inert, neither causing nor promoting corrosion of the cooling system. Some applications also require the coolant to be an electrical insulator. Heat capacity (abbreviated Cth or just C, also called thermal capacity) is the ability of matter to store heat. ... Viscosity is a measure of the resistance of a fluid to deform under shear stress. ... See corrosive for the hazard. ... This article or section is in need of attention from an expert on the subject. ...

The coolant can either keep its phase and stay liquid or gaseous, or can undergo a phase change, with the latent heat adding to the cooling efficiency. The latter, when used to achieve low temperatures, is more commonly known as refrigerant. In its most common usage, the term phase change indicates that a substance has changed among the three classical phases of matter: solid, liquid and gas. ... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during evaporation. ... A refrigerant is a compound used in a heat cycle that undergoes a phase change from a gas to a liquid and back. ...

Gases

Air is a common form of a coolant. Air cooling uses either convective airflow (passive cooling), or a forced circulation using fans. Layers of Atmosphere - not to scale (NOAA)[2] Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... See also CPU cooling Watercooling Heat pipe cooling Peltier cooling External links http://www. ... Convection in the most general terms refers to the internal movement of currents within fluids (i. ... It has been suggested that this article be split into multiple articles accessible from a disambiguation page. ...

Inert gases are frequently used as coolants in gas-cooled nuclear reactors. Helium is the most favored coolant due to its low tendency to absorb neutrons and become radioactive. Nitrogen and carbon dioxide are frequently used as well. An inert gas is any gas that is not reactive under normal circumstances. ... Core of a small nuclear reactor used for research. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Standard atomic weight 4. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ...

Sulfur hexafluoride is used for cooling and insulating of some high-voltage power systems (circuit breakers, switches, some transformers, etc.). Sulfur hexafluoride is an inorganic compound with the formula SF6. ... A 2 pole MCB A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. ... Electrical switches. ... Three-phase pole-mounted step-down transformer. ...

Steam can be used where high specific heat capacity is required in gaseous form and the corrosive properties of hot water are accounted for. It has been suggested that this article be split into articles entitled steam and water vapor, accessible from a disambiguation page. ... Specific heat capacity, also known simply as specific heat (Symbol: C or c) is the measure of the heat energy required to raise the temperature of a given amount of a substance by one degree. ...

Liquids

The most common coolant is water. Its high heat capacity and low cost makes it a suitable heat-transfer medium. It is usually used with additives, like corrosion inhibitors and antifreezes. Antifreeze, a solution of a suitable organic chemical (most often ethylene glycol, diethylene glycol, or propylene glycol) 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. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Corrosion inhibitor - Wikipedia /**/ @import /w/skins-1. ... Antifreeze is a water-based liquid coolant used in gasoline and diesel engines. ... Ethylene glycol (monoethylene glycol (MEG), IUPAC name: ethane-1,2-diol) is an alcohol with two -OH groups (a diol), a chemical compound widely used as an automotive antifreeze. ... Diethylene glycol (DEG) is a diol, an alcohol with two -OH groups, a dimer of ethylene glycol, which has caused several mass poisonings. ... Propylene glycol, also known as 1,2-propanediol, is an organic compound (a diol alcohol), usually a tasteless, odorless, and colorless clear oily liquid that is hygroscopic and miscible with water, acetone, and chloroform. ...

Very pure deionized water, due to its relatively low electrical conductivity, is used to cool some electrical equipment, often high-power transmitters. Deionized water (DI water or de-ionized water; also spelled deionised water, see spelling differences) is water that lacks ions, such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide. ... Electrical conductivity or specific conductivity is a measure of a materials ability to conduct an electric current. ...

Heavy water is used in some nuclear reactors; it also serves as a neutron moderator. Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ... This does not adequately cite its references or sources. ...

Oils are used for applications where water is unsuitable. Natural olive oil Synthetic motor oil An oil is any substance that is in a viscous liquid state (oily) at ambient temperatures or slightly warmer, and is both hydrophobic (immiscible with water, literally water fearing) and lipophilic (miscible with other oils, literally fat loving). This general definition includes compound classes...

• Mineral oils serve as both coolants and lubricants in many mechanical gears. Castor oil is also used.
• Silicone oils are favored for their wide range of operating temperatures. However their high cost limits their applications.
• Fluorocarbon oils are used for the same reasons.
• High-power electric transformers use transformer oil for cooling and additional electric insulation.

Cutting fluid is a coolant that also serves as a lubricant for metal-shaping machine tools. Mineral oil or liquid petrolatum is a by-product in the distillation of petroleum to produce gasoline. ... Castor oil is a vegetable oil obtained from the castor bean (technically castor seed as the castor plant, Ricinus communis, is not a member of the bean family). ... Silicones (more accurately called polymerized siloxanes or polysiloxanes) are inorganic-organic polymers with the chemical formula [R2SiO]n, where R = organic groups such as methyl, ethyl, and phenyl. ... Some important fluorocarbons. ... Three-phase pole-mounted step-down transformer. ... Transformer oil is usually a highly-refined mineral oil that is stable at high temperatures and has excellent electrical insulating properties. ... Cutting fluid or coolant is liquid used to cool and lubricate the cutting edges of machine tools and the pieces they are shaping. ... A lubricant (colloquially, lube, although this may also refer to personal lubricants) is a substance (usually a liquid) introduced between two moving surfaces to reduce the friction and wear between them. ... A machine tool is a powered mechanical device, typically used to fabricate metal components of machines by the selective removal of metal. ...

Liquid fusible alloys can be used as coolants in applications where high temperature stability is required, eg. some fast breeder nuclear reactors. Sodium or sodium-potassium alloy NaK are frequently used. Another liquid metal used as a coolant is lead, in eg. lead cooled fast reactors, or a lead-bismuth alloy.. Some early fast neutron reactors used mercury. A fusible alloy, usually eutectic alloy is capable of being fused, as well as being liquefied by heat. ... The fast breeder or fast breeder reactor (FBR) is a type of fast neutron reactor that produces more fissile material than it consumes. ... Core of a small nuclear reactor used for research. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Standard atomic weight 22. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Standard atomic weight 39. ... NaK (often pronounced as such, rhyming with sack) is an alloy of sodium and potassium, and particularly one that is liquid at room temperatures. ... For Pb as an abbreviation, see PB. General Name, Symbol, Number lead, Pb, 82 Chemical series poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ... The Lead-cooled Fast Reactor is a Generation IV reactor that features a fast-spectrum lead or lead/bismuth eutectic liquid metal-cooled reactor with a closed fuel cycle. ... General Name, Symbol, Number bismuth, Bi, 83 Chemical series poor metals Group, Period, Block 15, 6, p Appearance lustrous reddish white Atomic mass 208. ... 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. ... General Name, Symbol, Number mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12, 6, d Appearance silvery Standard atomic weight 200. ...

For very high temperature applications, eg. molten salt reactors or very high temperature reactors, molten salts can be used as coolants. One of the possible combinations is the mix of sodium fluoride and sodium tetrafluoroborate (NaF-NaBF₄). A molten salt reactor is a type of nuclear reactor where the working fluid is a molten salt. ... Very high temperature reactor scheme. ... A magnified crystal of a salt (halite/sodium chloride) Salt covering the floor of Bad Water in Death Valley, CA, the lowest point in the US. A salt, in chemistry, is defined as the product formed from the neutralisation reaction of acids and bases. ... Sodium fluoride is an ionic compound with the formula NaF. This colourless solid is the main source of the fluoride ion in diverse applications. ...

Freons were frequently used for immersive cooling of eg. electronics. Freon is a trade name for a group of chlorofluorocarbons used primarily as a refrigerant. ...

Refrigerants are coolants used for reaching low temperatures by undergoing phase change between liquid and gas. Halomethanes were frequently used, most often R-12 and R-22, but due to environmental concerns are being phased out, often with liquified propane or other haloalkanes like R-134a. Anhydrous ammonia is frequently used in large commercial systems, and sulfur dioxide was used in early mechanical refrigerators. Carbon dioxide (R-744) is used as a working fluid in climate control systems for cars, residential air conditioning, commercial refrigeration, and vending machines. A refrigerant is a compound used in a heat cycle that undergoes a phase change from a gas to a liquid and back. ... Halomethane compounds are molecules of methane (CH4) with one or more of the hydrogen atoms replaced with halogen atoms. ... // Overview The R-12 was an intercontinental ballistic missile designed in the Soviet Union, operated by the Strategic Rocket Forces. ... The haloalkanes are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic halide. ... 45 kg LPG cylinders Spherical Gas Container typically found in Refineries. ... 1,1,1,2-Tetrafluoroethane, also called simply tetrafluoroethane or R-134a, is a refrigerant that has zero ozone depletion potential and thermodynamic properties similar to R-12. ... Ammonia is a compound with the formula NH3. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ...

Heat pipes are a special application of refrigerants. The heat sink (aluminium) with heat pipe (copper) A heat pipe is a heat transfer mechanism that can transport large quantities of heat with a very small difference in temperature between the hot and cold interfaces. ...

Liquid gases are used as coolants for cryogenic applications, namely applications using superconductors, or extremely sensitive sensors and very low-noise amplifiers. The most common and least expensive coolant in use is liquid nitrogen. Liquid air is used to lower degree, due to its oxygen content which makes it prone to exploding in contact with combustible materials. Lower temperatures can be reached using liquefied neon. The lowest temperatures, used for the most powerful superconducting magnets, are reached using liquid helium. 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. ... Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of electrical resistance and the damping of the interior magnetic field (the Meissner effect. ... // Distinguish from censure and censer and censor. ... For the Irish mythological figure, see Naoise. ... Generally, an amplifier is any device that uses a small amount of energy to control a larger amount of energy. ... General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1. ... Liquid air is air that has been liquified by compression and cooled to very low temperatures. ... General Name, Symbol, Number neon, Ne, 10 Chemical series noble gases Group, Period, Block 18, 2, p Appearance colorless Standard atomic weight 20. ... Superconducting magnets are electromagnets that are built using superconducting coils. ... Helium exists in liquid form only at very low temperatures. ...

Fuels 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 and other jet fuels frequently serve in this role in aviation engines, liquid hydrogen is used to cool nozzles and chambers of rocket engines. Fuel is any material that is capable of releasing energy when its chemical or physical structure is changed or converted. ... Kerosene or paraffin oil (British English, not to be confused with the waxy solid also called paraffin wax or just paraffin) is a colorless flammable hydrocarbon liquid. ... Jet fuel is a type of aviation fuel designed for use in jet-engined aircraft. ... This article does not adequately cite its references or sources. ... A cold (un-ignited) rocket engine test at NASA A rocket engine is a reaction engine that can be used for spacecraft propulsion as well as terrestrial uses, such as missiles. ...

See also

• Loss of coolant - a type of a nuclear reactor failure

A Loss of Coolant Accident (LOCA) is a mode of failure for a nuclear reactor; in a nuclear reactor, the results of a LOCA could be catastrophic to the reactor, the facility that houses it, and the immediate vicinity around the reactor. ... Core of a small nuclear reactor used for research. ...

External links

• CO₂ as a natural coolant - CO₂ technology