Define refrigerant | Dictionary and Thesaurus

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« DefinerefriesDefinerefrigerate »Go to Dictionary DefinitionGo to User ContributedDictionaryGo to Extensive DefinitionGo to Synonyms, Antonyms and RelatedWordsDictionary Definitionrefrigerant adj : causing cooling or freezing; "arefrigerant substance such as ice or solid carbon dioxide" [syn:refrigerating] n :a substance used to provide cooling (as in a refrigerator)User ContributedDictionaryEnglishA substance used in a heat cycle that undergoes a phase change between gas andliquid to allow the cooling, as in refrigerators, air conditioners,See alsocoolantExtensive DefinitionA refrigerant is a compound used in a heat cyclethat undergoes a phase changefrom a gas to a liquid and back. The two mainuses of refrigerants are refrigerators/freezers and airconditioners. Cf. coolant.Until concerns about depletion of the ozone layerarose in the 1980s, the most widely used refrigerants were thehalomethanesR-12 and R-22,with R-12 being more common in automotive air conditioning andsmall refrigerators, and R-22 being used for residential and lightcommercial air conditioning, refrigerators, and freezers. Some veryearly systems used R-11because its relatively high boiling point allows low-pressuresystems to be constructed, reducing the mechanical strengthrequired for components. New production of R-12 ceased in theUnited States in 1995, and R-22 is to be phased out in 2010.R-134a andcertain blends are now replacing chlorinated compounds. One popular50/50 blend of R-32 and R-125 now being increasingly substitutedfor R-22 is R410a, often marketedunder the trade name Puron. Another popular blend of R-32, R-125,and R-134a with a higher critical temperature, and lower GWP thanR-410a is R-407c. While the R-22 and other ozone depletingrefrigerants are being phased out, they still have value and can beeasily sold.The ideal refrigerant has good thermodynamic properties,is noncorrosive, and safe. The desired thermodynamic properties area boilingpoint somewhat below the target temperature, a high heatof vaporization, a moderate density in liquid form, arelatively high density in gaseous form, and a high criticaltemperature. Since boiling point and gas density are affected bypressure, refrigerantsmay be made more suitable for a particular application by choice ofoperating pressure.Corrosion properties are a matter of materialscompatibility with the components used for the compressor,piping, evaporator, and condenser. Safetyconsiderations include toxicity and flammability.Early mechanical refrigeration systems employedsulfurdioxide gas or anhydrousammonia, with small home refrigerators primarily using theformer. Being toxic, sulfur dioxide rapidly disappeared from themarket with the introduction of Freon. Ammonia isstill used in some large commercial plants, well away fromresidential areas, where a leak will not cause widespreadinjuries.Use of highly purified liquified propane gas as a refrigerant is gaining favor,especially in systems designed for R-12, R-22 or R-134a. Moreover,propane is nontoxic. An odorant, such as ethyl mercaptan, can beadded in trace amounts to alert persons of system leaks.Emissions from automotive air-conditioning are agrowing concern because of their impact on climate change. From2011 on, the European Union will phase out refrigerants with aglobalwarming potential (GWP) of more than 150 in automotive airconditioning (GWP = 100 year warming potential of one kilogram of agas relative to one kilogram of CO2). This will ban potentgreenhouse gases such as the refrigerant HFC-134a—which has a GWPof 1410—to promote safe and energy-efficient refrigerants. One ofthe most promising alternatives is the natural refrigerant CO2(R-744).Carbondioxide is non-flammable, non-ozone depleting, has a globalwarming potential of 1, but is toxic and potentially lethal inconcentrations above 5% by volume. R-744 can be used as a workingfluid in climate control systems for cars, residential airconditioning, hot water pumps, commercial refrigeration, andvending machines.Recycling refrigerantsCFC's or chlorofluorocarbons are used asrefrigerants in some commercial air conditioning and refrigerationsystems. CFC's are considered to be 100% ozone depleting, meaningthat they are the standard for efficiency in the catalyticbreakdown of ozone. In most residential air conditioners and manyrefrigeration systems it is R-22 or Freon which is ahydrochlorofluorocarbon or HCFC. HCFC's are considered to be 5%ozone depleting and are less of a danger to the Earth's vital ozonelayer. However, non-ozone layer depleting refrigerants aredesired.As of July 1, 1992 it is illegal to release Freonor other refrigerants into the atmosphere because they can causesevere damage to the ozone layer. When CFCs are removed they shouldbe recycled to clean out any contaminants and return it to a usablecondition. Refrigerants should never be mixed together. Some CFCsmust be managed as hazardous waste, even if recycled and specialprecautions are required for their transport.Refrigerants by classRefrigerants may be divided intothree classes according to their manner of absorption or extractionof heat from the substances to be refrigerated:Class 1: This class includes refrigerants thatcool by phase change (typically boiling), using the refrigerant'slatentheat.Class 2: These refrigerants cool by temperaturechange or 'sensibleheat', the quantity of heat being the specific heat capacity xthe temperature change. They are air, calcium chloride brine,sodium chloride brine, alcohol, and similar nonfreezing solutions.The purpose of Class 2 refrigerants is to receive a reduction oftemperature from Class 1 refrigerants and convey this lowertemperature to the area to be air-conditioned.Class 3: This group consists of solutions thatcontain absorbed vapors of liquefiable agents or refrigeratingmedia. These solutions function by nature of their ability to carryliquefiable vapors, which produce a cooling effect by theabsorption of their heat of solution.NumberingThe R-# numbering system was developed byDuPont andsystematically identifies the molecular structure of refrigerantsmade with a single halogenated hydrocarbon. The meaning of thecodes is as follows:Rightmost digit: Number of fluorine atoms per molecule.Tens digit: One plus the number of hydrogen atoms per molecule.Hundreds digit: The number of carbon atoms minus one. Omittedfor methyl halides, which have only one carbon atom.Thousands digit" Number of double bondsin the molecule. This is omitted when zero, and in practice israrely used, since most candidate compounds are unstable.A suffix with a capital B and a number indicates the number ofbromine atoms, whenpresent. This is rarely used.Remaining bonds not accounted for are occupied by chlorine atoms.A suffix of a lower-case letter a, b, or c indicatesincreasingly unbalanced isomers.As a special case, the R-400 series is made up of zeotropicblends (those where the boiling point of constituent compoundsdiffers enough to lead to changes in relative concentration becauseof fractionaldistillation) and the R-500 series is made up of so-calledazeotropic blends. Therightmost digit is assigned arbitrarily by ASHRAE, an industryorganization.For example, R-134ahas 4 fluorine atoms, 2 hydrogen atoms, 2 carbon atoms, with anempirical formula of tetrafluoroethane. The "a" suffix indicatesthat the isomer is unbalanced by one atom, giving 1,1,1,2-Tetrafluoroethane.R-134 without the "a" suffix would have a molecular structure of1,1,2,2-Tetrafluoroethane—a compound not especially effective as arefrigerant.The same numbers are used with an R- prefix forgeneric refrigerants, with a "Propellant" prefix (e.g., "Propellant12") for the same chemical used as a propellant for an aerosolspray, and with trade names for the compounds, such as "Freon12". Recently, a practice of using HFC- for hydrofluorocarbons,CFC- for chlorofluorocarbons,and HCFC- for hydrochlorofluorocarbonshas arisen, because of the regulatory differences among thesegroups.See alsoListof refrigerantsReferenceshttp://www.fluorocarbons.org/en/applications/refrigeration.htmlFluorocarbons as RefrigerantsExternal linksUSEnvironmental Protection Agency page on the GWPs of varioussubstancesrefrigerant in German: Kältemittelrefrigerant in Spanish: Líquidorefrigeranterefrigerant in Italian: Fluidorefrigeranterefrigerant in Japanese: 冷媒refrigerant in Russian: Холодильный агентrefrigerant in Ukrainian:ХолодоагентSynonyms, Antonyms and RelatedWordsDry Ice, Freon, algific, ammonia, blast-freezing, carbondioxide, chilling,congealing, coolant, cooling, ether, ethyl chloride, freezable, freezing, freezing mixture,frigorific, glaciable, ice, ice cubes, liquid air, liquidhelium, liquid oxygen, quick-freezing, refrigerative, refrigeratory,sharp-freezing

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