Information about Coolant
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.
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.
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.
Sulfur hexafluoride is used for cooling and insulating of some high-voltage power systems (circuit breakers, switches, some transformers, etc.).
Steam can be used where high specific heat capacity is required in gaseous form and the corrosive properties of hot water are accounted for.
Very pure deionized water, due to its relatively low electrical conductivity, is used to cool some electrical equipment, often high-power transmitters.
Heavy water is used in some nuclear reactors; it also serves as a neutron moderator.
Oils are used for applications where water is unsuitable.
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; in special cases lithium can be employed. 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.
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).
Freons were frequently used for immersive cooling of eg. electronics.
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.
Heat pipes are a special application of refrigerants.
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.
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.
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.
Gases
Air is a common form of a coolant. Air cooling uses either convective airflow (passive cooling), or a forced circulation using fans.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.
Sulfur hexafluoride is used for cooling and insulating of some high-voltage power systems (circuit breakers, switches, some transformers, etc.).
Steam can be used where high specific heat capacity is required in gaseous form and the corrosive properties of hot water are accounted for.
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.Very pure deionized water, due to its relatively low electrical conductivity, is used to cool some electrical equipment, often high-power transmitters.
Heavy water is used in some nuclear reactors; it also serves as a neutron moderator.
Oils are used for applications where water is unsuitable.
- 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.
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; in special cases lithium can be employed. 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.
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).
Freons were frequently used for immersive cooling of eg. electronics.
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.
Heat pipes are a special application of refrigerants.
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.
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.
See also
- Loss of coolant — a type of a nuclear reactor failure
External links
Viscosity is a measure of the resistance of a fluid to deform under either shear stress or extensional stress. It is commonly perceived as "thickness", or resistance to flow.
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Corrosion is breaking down of essential properties in a material due to reactions with its surroundings. In the most common use of the word, this means a loss of an electron of metals reacting with water and oxygen.
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Electrical insulator is a material or object that resists the flow of electric current. When a voltage is placed across an insulator, very little current flows. An object intended to support or separate electrical conductors without passing current through itself is called an
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phase transition or phase change is the transformation of a thermodynamic system from one phase to another. The distinguishing characteristic of a phase transition is an abrupt change in one or more physical properties, in particular the heat capacity, with a small change in
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In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase (i.e. solid, liquid, or gas), - also called a phase transition.
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A refrigerant is a compound used in a heat cycle 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. Cf. coolant.
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Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly (by molar content/volume) 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.
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Air cooling is one method of dissipating heat. It works by making the object to be cooled have a larger surface area or have an increased flow of air over its surface, or both.
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Convection in the most general terms refers to the movement of currents within fluids (i.e. liquids, gases and rheids).
Convection is one of the major modes of heat and mass transfer.
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Convection is one of the major modes of heat and mass transfer.
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mechanical fan is a device used to produce an airflow for the purpose of creature comfort, ventilation, exhaust, or any other gaseous transport.
Mechanically, a fan can be any revolving vane or vanes used for producing currents of air.
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Mechanically, a fan can be any revolving vane or vanes used for producing currents of air.
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inert gas is any gas that is not reactive under normal circumstances. Unlike the noble gases an inert gas is not necessarily elemental and are often molecular gases. Like the noble gases the tendency for non-reactivity is due to the valence, the outermost electron shell, being
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UO2 pellets in zircaloy cladding.]]
The key components common to most types of nuclear power plants
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The key components common to most types of nuclear power plants
- Neutron moderator
- Coolant
- Control rods
- Pressure vessel
- Emergency Core Cooling Systems (ECCS)
- Reactor Protective System (RPS)
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Helium (He) is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas series in the periodic table and whose atomic number is 2.
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3, 5, 4, 2
(strongly acidic oxide)
Electronegativity 3.04 (Pauling scale)
Ionization energies
(more) 1st: 1402.3 kJmol−1
2nd: 2856 kJmol−1
3rd: 4578.1 kJmol−1
Atomic radius 65 pm
Atomic radius (calc.
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(strongly acidic oxide)
Electronegativity 3.04 (Pauling scale)
Ionization energies
(more) 1st: 1402.3 kJmol−1
2nd: 2856 kJmol−1
3rd: 4578.1 kJmol−1
Atomic radius 65 pm
Atomic radius (calc.
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Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.
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Sulfur hexafluoride is an inorganic compound with the formula SF6. It is a colorless, odorless, non-toxic and non-flammable gas (at standard conditions). SF6 has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom.
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A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or
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switch is a device for changing the course (or flow) of a circuit. The prototypical model is a mechanical device (for example a railroad switch) which can be disconnected from one course and connected to another.
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transformer is a device that transfers electrical energy from one circuit to another through inductively coupled wires. A changing current in the first circuit (the primary
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In physical chemistry, and in engineering, steam refers to vaporized water. It is a pure, completely invisible gas (for mist see below). At standard atmospheric pressure, pure steam (unmixed with air, but in equilibrium with liquid water) occupies about 1,600 times the
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Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval.
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Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.
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A corrosion inhibitor is a chemical compound that, when added in small concentration, stops or slows down corrosion of metals and alloys.
A typical good corrosion inhibitor will give 95% inhibition at concentration of 80 ppm, and 90% at 40 ppm.
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A typical good corrosion inhibitor will give 95% inhibition at concentration of 80 ppm, and 90% at 40 ppm.
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Antifreeze is used in internal combustion engines, and for many other heat transfer applications, such as electronics cooling and chillers for HVAC. Compounds are added to water to reduce the freezing point of the mixture to below the lowest temperature that the system is likely to
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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.
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Diethylene glycol (DEG) is an organic compound described by the structural formula HO-CH2-CH2-O-CH2-CH2-OH. It is a clear, hygroscopic, odorless liquid. It is miscible with water and polar organic solvents such as alcohols and ethers.
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Propylene glycol, known also by the systematic name propane-1,2-diol, 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.
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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.
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Electrical conductivity or specific conductivity is a measure of a material's ability to conduct an electric current. When an electrical potential difference is placed across a conductor, its movable charges flow, giving rise to an electric current.
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Heavy water is water which contains a higher proportion than normal of the isotope deuterium, as deuterium oxide, D2O or 2H2O, or as deuterium protium oxide, HDO or 1H2HO.
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