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43-403: NaK containing 40% to 90% potassium by mass is liquid at room temperature . The eutectic mixture consists of 77% potassium and 23% sodium by mass (NaK-77), and it is a liquid from −12.6 to 785 °C (9.3 to 1,445.0 °F), and has a density of 0.866 g/cm at 21 °C (70 °F) and 0.855 g/cm at 100 °C (212 °F), making it less dense than water. It is highly reactive with water and

86-605: A BES-5 reactor, which was cooled with NaK. In addition to the wide liquid temperature range, NaK has a very low vapor pressure , which is important in the vacuum of space . An unintended consequence of the usage as a coolant on orbiting satellites has been the creation of additional space debris . NaK coolant has leaked from a number of satellites, including Kosmos 1818 and Kosmos 1867 . The coolant self-forms into droplets of sodium–potassium of up to several centimeters in size. These objects are space debris. The Danamics LMX Superleggera CPU cooler uses NaK to transport heat from

129-410: A phase transition , with the latent heat adding to the cooling efficiency. The latter, when used to achieve below- ambient temperature , is more commonly known as refrigerant . Air is a common form of a coolant. Air cooling uses either convective airflow (passive cooling), or a forced circulation using fans . Hydrogen is used as a high-performance gaseous coolant. Its thermal conductivity

172-784: A Si-Si backbone and methyl radicals, primarily dodecamethylcyclohexasilane . 6 ( CH 3 ) 2 SiCl 2 + 12 M ⟶ [ ( CH 3 ) 2 Si ] 6 + 12 MCl   ( M = Na , K ) {\displaystyle {\ce {6 (CH3)2SiCl2 + 12 M -> [(CH3)2Si]6 + 12 MCl}}\ {\ce {(M = Na, K)}}} Further alloys with low melting points are Cs 77 K 23 at −37.5 °C (−35.5 °F), Cs 19 Na at −30 °C (−22 °F) and Na 2 Rb 23 at −5 °C (23 °F). The alloy consisting of 40.8 % caesium, 11.8 % sodium and 47.4 % potassium has

215-486: A comfort band of 26–32.45 °C (79–90 °F) with a mean of 29.23 °C (85 °F). A study conducted in Jaipur, India among healthy young men showed that the neutral thermal comfort temperature was analyzed to be 30.15 °C (86 °F), although a range of 25.9–33.8 °C (79–93 °F) was found. People are highly sensitive to even small differences in environmental temperature. At 24 °C (75 °F),

258-513: A difference of 0.38 °C (0.68 °F) can be detected between the temperature of two rooms. Owing to variations in humidity and (likely) clothing, recommendations for summer and winter may vary; a suggested typical range for summer is 23–25.5 °C (73–78 °F), with that for winter being 20–23.5 °C (68–74 °F). Some studies have suggested that thermal comfort preferences of men and women may differ significantly, with women on average preferring higher ambient temperatures. In

301-409: A melting point of −79.4 °C (−110.9 °F). NaK has been used as the coolant in experimental fast neutron nuclear reactors . Unlike commercial plants, these are frequently shut down and defuelled. Use of lead or pure sodium, the other materials used in practical reactors, would require continual heating to maintain the coolant as a liquid. Use of NaK overcomes this. The Dounreay Fast Reactor

344-491: A minimum of 20 °C (68 °F) was recommended. Temperatures lower than 16 °C (61 °F) with humidity above 65% were associated with respiratory hazards including allergies. The WHO's 2018 guidelines give a strong recommendation that a minimum of 18 °C (64 °F) is a "safe and well-balanced indoor temperature to protect the health of general populations during cold seasons". A higher minimum temperature may be necessary for vulnerable groups including children,

387-471: A particular context, room temperature can mean different agreed-upon ranges. In contrast, ambient temperature is the actual temperature, as measured by a thermometer , of the air (or other medium and surroundings) in any particular place. The ambient temperature (e.g. an unheated room in winter) may be very different from an ideal room temperature . Food and beverages may be served at "room temperature", meaning neither heated nor cooled. Comfort temperature

430-450: A precursor to ibuprofen . Industrially, NaK is produced in a reactive distillation . Room temperature Room temperature , colloquially, denotes the range of air temperatures most people find comfortable indoors while dressed in typical clothing. Comfortable temperatures can be extended beyond this range depending on humidity , air circulation , and other factors. In certain fields, like science and engineering , and within

473-433: 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. Betaine is a similar coolant, with the exception that it is made from pure plant juice, and is not toxic or difficult to dispose of ecologically. Polyalkylene glycol (PAG)

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516-651: Is 2.14 GPa, higher than of a hydraulic oil at room temperature. Its lubricity is poor, so positive-displacement pumps are unsuitable and centrifugal pumps have to be used. Addition of caesium shifts the useful temperature range to −71 to 704 °C (−96 to 1,299 °F). NaK-77 was tested in hydraulic and fluidic systems for the Supersonic Low Altitude Missile . NaK may also be used to transmit forces inside high temperature pressure transducers as an alternative to mercury. NaK can be used as catalyst in some reactions, such as isobutylbenzene ,

559-404: Is 982 J/(kg⋅K), which is roughly one quarter of that for water, but heat transfer is higher over a temperature gradient due to higher thermal conductivity. When stored in air , it forms a yellow potassium superoxide coating and may ignite. This superoxide reacts explosively with water and organics. NaK is not dense enough to sink in most hydrocarbons , but will sink in lighter mineral oil . It

602-402: Is CO 2 ) - is used as a coolant replacement for cutting fluids. CO 2 can provide controlled cooling at the cutting interface such that the cutting tool and the workpiece are held at ambient temperatures. The use of CO 2 greatly extends tool life, and on most materials allows the operation to run faster. This is considered a very environmentally friendly method, especially when compared to

645-477: Is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity , low viscosity , is low-cost, non-toxic , chemically inert and neither causes nor promotes corrosion of the cooling system. Some applications also require the coolant to be an electrical insulator . While the term "coolant" is commonly used in automotive and HVAC applications, in industrial processing heat-transfer fluid

688-508: Is an example. The first nuclear reactor in space, the United States' experimental SNAP-10A satellite, used NaK as coolant. The NaK was circulated through the core and thermoelectric converters by a liquid metal direct current conduction-type pump. The satellite was launched in 1965, and as of 2022 is the only fission reactor power system launched into space by the United States. The Soviet RORSAT radar satellites were powered by

731-522: 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. Many otherwise excellent refrigerants are phased out for environmental reasons (the CFCs due to ozone layer effects, now many of their successors face restrictions due to global warming, e.g.

774-464: Is higher than all other gases, it has high specific heat capacity , low density and therefore low viscosity , which is an advantage for rotary machines susceptible to windage losses. Hydrogen-cooled turbogenerators are currently the most common electrical generators in large power plants. Inert gases are used as coolants in gas-cooled nuclear reactors . Helium has a low tendency to absorb neutrons and become radioactive . Carbon dioxide

817-522: Is interchangeable with neutral temperature in the scientific literature, which can be calculated through regression analysis between thermal sensation votes and indoor temperature. The neutral temperature is the solution of the resulting regression model by setting the thermal sensation vote as zero. The American Heritage Dictionary of the English Language identifies room temperature as around 20–22 °C (68–72 °F; 293–295 K), while

860-446: Is one technical term more often used in high temperature as well as low-temperature manufacturing applications. The term also covers cutting fluids . Industrial cutting fluid has broadly been classified as water-soluble coolant and neat cutting fluid. Water-soluble coolant is oil in water emulsion. It has varying oil content from nil oil (synthetic coolant). This coolant can either keep its phase and stay liquid or gaseous, or can undergo

903-663: Is required, e.g. some fast breeder nuclear reactors . Sodium (in sodium cooled fast reactors ) 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 e.g. lead cooled fast reactors , or a lead- bismuth alloy. Some early fast neutron reactors used mercury . For certain applications the stems of automotive poppet valves may be hollow and filled with sodium to improve heat transport and transfer. For very high temperature applications, e.g. molten salt reactors or very high temperature reactors , molten salts can be used as coolants. One of

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946-403: Is stored usually under hexane or other hydrocarbons, or under an inert gas (usually dry nitrogen or argon ) if high purity and low levels of oxidation are required. A solid compound, Na 2 K , exists at low temperatures, containing 46 percent potassium by mass. NaK has a very high surface tension , which makes large amounts of it pull into a bun -like shape. Its specific heat capacity

989-417: Is the best known example encountered in laboratories. The phase change may not occur at the cooled interface, but on the surface of the liquid, to where the heat is transferred by convective or forced flow. Water is the most common coolant. Its high heat capacity and low cost make it a suitable heat-transfer medium. It is usually used with additives, like corrosion inhibitors and antifreeze . Antifreeze,

1032-467: Is unsafe to store in this manner if the superoxide has formed. A large explosion took place at the Oak Ridge Y-12 facility on December 8, 1999 , when NaK cleaned up after an accidental spill and inappropriately treated with mineral oil was scratched with a metal tool. The liquid alloy also attacks PTFE ("Teflon"). Sodium–potassium alloy polymerizes dimethyldichlorosilane into polysilanes with

1075-495: Is used as high temperature, thermally stable heat transfer fluids exhibiting strong resistance to oxidation. Modern PAGs can also be non-toxic and non-hazardous. Cutting fluid is a coolant that also serves as a lubricant for metal-shaping machine tools . Oils are often 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

1118-487: Is used in Magnox and AGR reactors. 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. Some coolants are used in both liquid and gas form in the same circuit, taking advantage of

1161-459: Is used to cool nozzles of rocket engines . Waterless coolant is used as an alternative to conventional water and ethylene glycol coolants. With higher boiling points than water (around 370F), the cooling technology resists boil over. The liquid also prevents corrosion . Freons were frequently used for immersive cooling of e.g. electronics. Liquid fusible alloys can be used as coolants in applications where high temperature stability

1204-713: The Oxford English Dictionary states that it is "conventionally taken as about 20 °C (68 °F; 293 K)". Ideal room temperature varies vastly depending on the surrounding climate. Studies from Indonesia have shown that the range of comfortable temperature is 24–29 °C (75–84 °F) for local residents. Studies from Nigeria show a comfortable temperature range of 26–28 °C (79–82 °F), comfortably cool 24–26 °C (75–79 °F) and comfortably warm 28–30 °C (82–86 °F). A field study conducted in Hyderabad, India returned

1247-659: The Japanese Pharmacopeia defines "ordinary temperature" as 15 to 25 °C (59 to 77 °F), with room temperature being 1 to 30 °C (34 to 86 °F). Merriam-Webster gives as a medical definition a range of 15 to 25 °C (59 to 77 °F) as being suitable for human occupancy, and at which laboratory experiments are usually performed. World Health Organization (2018). WHO Housing and Health Guidelines . ISBN   978-92-4-155037-6 . PMID   30566314 . Wikidata   Q95379102 . Retrieved 2022-11-22 . Coolant A coolant

1290-507: The CPU to its cooling fins. In contact with water, hydrogen is created. Hence, sodium–potassium alloys are used as desiccants in drying solvents prior to distillation . Eutectic NaK (NaK-77, an alloy of 77% potassium and 23% sodium by mass) can be used as a hydraulic fluid in high-temperature and high-radiation environments, for temperature ranges of −12 to 760 °C (10 to 1,400 °F). Its bulk modulus at 538 °C (1,000 °F)

1333-478: The R134a). Heat pipes are a special application of refrigerants. Water is sometimes employed this way, e.g. in boiling water reactors . The phase change effect can be intentionally used, or can be detrimental. Phase-change materials use the other phase transition between solid and liquid. Liquid gases may fall here, or into refrigerants, as their temperature is often maintained by evaporation. Liquid nitrogen

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1376-551: The UK, the Offices, Shops and Railway Premises Act 1963 provides for a minimum temperature in commercial premises, but not for a maximum temperature. The World Health Organization in 1987 found that comfortable indoor temperatures of 18–24 °C (64–75 °F) were not associated with health risks for healthy adults with appropriate clothing, humidity, and other factors. For infants, elderly, and those with significant health problems,

1419-488: The carrier liquid enhance the heat transfer capabilities of the resulting coolant compared to the carrier liquid alone. The enhancement can be theoretically as high as 350%. The experiments however did not prove so high thermal conductivity improvements, but found significant increase of the critical heat flux of the coolants. Some significant improvements are achievable; e.g. silver nanorods of 55±12 nm diameter and 12.8 μm average length at 0.5 vol.% increased

1462-468: The container or loop system in question. Many oils have uses encompassing heat transfer, lubrication, pressure transfer (hydraulic fluids), sometimes even fuel, or several such functions at once. 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

1505-545: The elderly, and people with cardiorespiratory disease and other chronic illnesses. However, the recommendation regarding risk of exposure to high indoor temperatures is only "conditional". Minimal-risk high temperatures range from about 21 to 30 °C (70 to 86 °F) depending on the region, with maximum acceptable temperatures between 25 and 32 °C (77 and 90 °F). Temperature ranges are defined as room temperature for certain products and processes in industry, science, standards, and consumer goods. For instance, for

1548-427: The formation of the steam layer. Nanofluid with the concentration more than 5% acts like non-Newtonian fluids . In some applications, solid materials are used as coolants. The materials require high energy to vaporize; this energy is then carried away by the vaporized gases. This approach is common in spaceflight , for ablative atmospheric reentry shields and for cooling of rocket engine nozzles . The same approach

1591-431: The high specific latent heat of boiling/condensing phase change , the enthalpy of vaporization , in addition to the fluid's non-phase-change heat capacity . 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 , often with liquified propane or other haloalkanes like R-134a . Anhydrous ammonia

1634-615: The most powerful superconducting magnets , are reached using liquid helium . Liquid hydrogen at -250 to -265 °C can also be used as a coolant. Liquid hydrogen is also used both as a fuel and as a coolant to cool nozzles and combustion chambers of rocket engines . A new class of coolants are nanofluids which consist of a carrier liquid, such as water, dispersed with tiny nano-scale particles known as nanoparticles . Purpose-designed nanoparticles of e.g. CuO , alumina , titanium dioxide , carbon nanotubes , silica , or metals (e.g. copper , or silver nanorods ) dispersed into

1677-436: The possible combinations is the mix of sodium fluoride and sodium tetrafluoroborate (NaF-NaBF 4 ). Other choices are FLiBe and FLiNaK . Liquified gases are used as coolants for cryogenic applications, including cryo-electron microscopy , overclocking of computer processors, applications using superconductors , or extremely sensitive sensors and very low- noise amplifiers . Carbon Dioxide (chemical formula

1720-541: The recent past, it was common for house temperatures to be kept below the comfort level; a 1978 UK study found average indoor home temperatures to be 15.8 °C (60.4 °F) while Japan in 1980 had median home temperatures of 13 °C (55 °F) to 15 °C (59 °F). Rooms may be maintained at an ambient temperature above the comfort temperature in hot weather, or below it in cold weather, if required by cost considerations or practical issues (e.g. lack of air conditioning or relatively high expense of heating.) In

1763-524: The shipping and storage of pharmaceuticals , the United States Pharmacopeia -National Formulary (USP-NF) defines controlled room temperature as between 20 and 25 °C (68 and 77 °F), with excursions between 15 and 30 °C (59 and 86 °F) allowed, provided the mean kinetic temperature does not exceed 25 °C (77 °F). The European Pharmacopoeia defines it as being simply 15 to 25 °C (59 to 77 °F), and

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1806-422: The thermal conductivity of water by 68%, and 0.5 vol.% of silver nanorods increased thermal conductivity of ethylene glycol based coolant by 98%. Alumina nanoparticles at 0.1% can increase the critical heat flux of water by as much as 70%; the particles form rough porous surface on the cooled object, which encourages formation of new bubbles, and their hydrophilic nature then helps pushing them away, hindering

1849-557: The use of petroleum oils as lubricants; parts remain clean and dry which often can eliminate secondary cleaning operations. Liquid nitrogen , which boils at about -196 °C (77K), is the most common and least expensive coolant in use. Liquid air is used to a lesser extent, due to its liquid oxygen content which makes it prone to cause fire or explosions when in contact with combustible materials (see oxyliquits ). Lower temperatures can be reached using liquified neon which boils at about -246 °C. The lowest temperatures, used for

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