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A refrigerant is a compound used in a heat cycle
Heat engine

A heat engine is a physical or theoretical device that converts thermal energy to mechanical output. The mechanical output is called Mechanical work, and the thermal energy input is called heat....
 that undergoes a phase change from a gas
Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
 to a liquid
Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
 and back. The two main uses of refrigerants are refrigerator
Refrigerator

A refrigerator is a cooling appliance comprising a thermal insulation compartment and a heat pump - a mechanism to transfer heat from it to the external environment, cooling the contents to a temperature below ambient....
s/freezers and air conditioners (cf. coolant
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....
). Since it was discovered in the 1980s that the most widely used refrigerants were major causes of ozone depletion
Ozone depletion

Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total volume of ozone in Earth stratosphere since the late 1970s, and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period....
, a worldwide phaseout of ozone-depleting refrigerants has been undertaken. These are being replaced with "ozone-friendly" refrigerants.
Physical properties
The ideal refrigerant has good thermodynamic properties, is noncorrosive, and safe.






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Encyclopedia


A refrigerant is a compound used in a heat cycle
Heat engine

A heat engine is a physical or theoretical device that converts thermal energy to mechanical output. The mechanical output is called Mechanical work, and the thermal energy input is called heat....
 that undergoes a phase change from a gas
Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
 to a liquid
Liquid

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
 and back. The two main uses of refrigerants are refrigerator
Refrigerator

A refrigerator is a cooling appliance comprising a thermal insulation compartment and a heat pump - a mechanism to transfer heat from it to the external environment, cooling the contents to a temperature below ambient....
s/freezers and air conditioners (cf. coolant
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....
). Since it was discovered in the 1980s that the most widely used refrigerants were major causes of ozone depletion
Ozone depletion

Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total volume of ozone in Earth stratosphere since the late 1970s, and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period....
, a worldwide phaseout of ozone-depleting refrigerants has been undertaken. These are being replaced with "ozone-friendly" refrigerants.

Physical properties


The ideal refrigerant has good thermodynamic properties, is noncorrosive, and safe. The desired thermodynamic properties are a boiling point
Boiling point

The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
 somewhat below the target temperature, a high heat of vaporization, a moderate density
Density

The density of a material is defined as its mass per unit volume. The symbol of density is ....
 in liquid form, a relatively high density in gaseous form, and a high critical temperature. Since boiling point and gas density are affected by pressure
Pressure

Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
, refrigerants may be made more suitable for a particular application by choice of operating pressure.

Corrosion properties are a matter of materials compatibility with the components used for the compressor
Gas compressor

A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe ....
, piping
Piping

Within industry, piping is a system of pipe used to convey fluids from one location to another. The engineering discipline of piping design studies the efficient transport of fluid....
, evaporator
Evaporator

Within a downstream processing system, several stages are used to further isolate and purify the desired product. The overall structure of the process includes pre-treatment, solid-liquid separation, concentration, and purification and formulation....
, and condenser
Condenser

Condenser may refer to:*Condenser , a device or unit used to Condensation vapor into liquid. More specific articles on some types include:*Condenser microphone, a device that converts sound waves into an electrical signal....
. Safety considerations include toxicity
Toxicity

Toxicity is the degree to which a substance is able to damage an exposed organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver ....
 and flammability.

History


Until concerns about depletion of the ozone layer
Ozone layer

The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 93-99% of the sun's high frequency ultraviolet light, which is potentially damaging to life on earth....
 arose in the 1980s, the most widely used refrigerants were the 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 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....
, with R-12 being more common in automotive air conditioning and small refrigerators, and R-22 being used for residential and light commercial air conditioning, refrigerators, and freezers. Some very early systems used R-11
Trichlorofluoromethane

Trichlorofluoromethane, also called freon-11, CFC-11, or R-11, is a chlorofluorocarbon. It is a colorless, nearly odorless liquid that boils at about room temperature....
 because its relatively high boiling point allows low-pressure systems to be constructed, reducing the mechanical strength required for components. New production of R-12 ceased in the United States in 1995, and R-22 is to be phased out by 2020. R-134a and certain blends are now replacing chlorinated compounds. One popular 50/50 blend of R-32 and R-125 now being increasingly substituted for R-22 is R410A, often marketed under the trade name Puron. Another popular blend of R-32, R-125, and R-134a with a higher critical temperature, and lower GWP than R-410A is R-407C. While the R-22 and other ozone depleting refrigerants are being phased out, they still have value and can be easily sold.

Early mechanical refrigeration systems employed 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....
 gas or 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....
, with small home refrigerators primarily using the former. Being toxic, sulfur dioxide rapidly disappeared from the market with the introduction of 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....
. Ammonia is still used in some large commercial plants.

Use of highly purified liquefied 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
Ethanethiol

Ethanethiol is the organic compound with the formula CH3CH2SH. It consists of an ethyl group, CH3CH2, attached to a thiol group, SH....
, can be added in trace amounts to alert persons of system leaks.

Uses


CFC's or chlorofluorocarbons are used as refrigerants in some commercial air conditioning and refrigeration systems. CFC's are considered to be 100% ozone depleting, meaning that they are the standard for efficiency in the catalytic breakdown of ozone. In most residential air conditioners and many refrigeration systems it is R-22 or Freon which is a hydrochlorofluorocarbon or HCFC. HCFC's are considered to be 5% ozone depleting and are less of a danger to the Earth's vital ozone layer. However, non-ozone layer depleting refrigerants are the most desirable.

Emissions from automotive air-conditioning are a growing concern because of their impact on climate change. From 2011 on, the European Union will phase out refrigerants with a global warming potential
Global warming potential

Global warming potential is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. It is a relative scale which compares the gas in question to that of the same mass of carbon dioxide ....
 (GWP) of more than 150 in automotive air conditioning (GWP = 100 year warming potential of one kilogram of a gas relative to one kilogram of CO2). This will ban potent greenhouse gases such as the refrigerant HFC-134a—which has a GWP of 1410—to promote safe and energy-efficient refrigerants. One of the most promising alternatives is the natural refrigerant CO2 (R-744). 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....
 is non-flammable, non-ozone depleting, has a global warming potential of 1, but is toxic and potentially lethal in concentrations above 5% by volume. R-744 can be used as a working fluid in climate control systems for cars, residential air conditioning, hot water pumps, commercial refrigeration, and vending machines.

Disposal


As of July 1, 1992 it is illegal to release refrigerants into the atmosphere (intentional or accidental) because they can cause severe damage to the ozone layer. When CFCs are removed they should be recycled to clean out any contaminants and return it to a usable condition. Refrigerants should never be mixed together. Some CFCs must be managed as hazardous waste even if recycled, and special precautions are required for their transport, depending on the legislation of the country's government.

Refrigerants by class


Refrigerants may be divided into three classes according to their manner of absorption or extraction of heat from the substances to be refrigerated:

Class 1: This class includes refrigerants that cool by phase change (typically boiling), using the refrigerant's 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....
.

Class 2: These refrigerants cool by temperature change or 'sensible heat
Sensible heat

Sensible heat is potential energy in the form of thermal energy or heat. The thermal body must have a temperature higher than its surroundings ....
', the quantity of heat being the specific heat capacity x the 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 of temperature from Class 1 refrigerants and convey this lower temperature to the area to be air-conditioned.

Class 3: This group consists of solutions that contain absorbed vapors of liquefiable agents or refrigerating media. These solutions function by nature of their ability to carry liquefiable vapors, which produce a cooling effect by the absorption of their heat of solution.thay can also be classified into many categories

Numbering

The R-# numbering system was developed by DuPont
DuPont

E. I. du Pont de Nemours and Company is an United States chemical industry that was founded in July 1802 as a gunpowder mill by Eleuth?re Ir?n?e du Pont....
 and systematically identifies the molecular structure of refrigerants made with a single halogenated hydrocarbon. The meaning of the codes is as follows:

  • Remaining bonds not accounted for are occupied by chlorine
    Chlorine

    Chlorine...
     atoms.
  • A suffix of a lower-case letter a, b, or c indicates increasingly unbalanced isomers.
  • As a special case, the R-400 series is made up of zeotropic blends (those where the boiling point of constituent compounds differs enough to lead to changes in relative concentration because of fractional distillation
    Fractional distillation

    Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compound by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate....
    ) and the R-500 series is made up of so-called azeotropic blends
    Azeotrope

    An azeotrope is a mixture of two or more liquids in such a ratio that its composition cannot be changed by simple distillation. This occurs because, when an azeotrope is boiled, the resulting vapor has the same ratio of constituents as the original mixture....
    . The rightmost digit is assigned arbitrarily by ASHRAE, an industry organization.


For example, R-134a
1,1,1,2-Tetrafluoroethane

1,1,1,2-Tetrafluoroethane, also called simply tetrafluoroethane, R-134a, Genetron 134a, Suva 134a or HFC-134a, is a haloalkane refrigerant with thermodynamic properties similar to dichlorodifluoromethane , but without its ozone depletion potential....
 has 4 fluorine atoms, 2 hydrogen atoms, 2 carbon atoms, with an empirical formula of tetrafluoroethane. The "a" suffix indicates that the isomer is unbalanced by one atom, giving 1,1,1,2-Tetrafluoroethane
1,1,1,2-Tetrafluoroethane

1,1,1,2-Tetrafluoroethane, also called simply tetrafluoroethane, R-134a, Genetron 134a, Suva 134a or HFC-134a, is a haloalkane refrigerant with thermodynamic properties similar to dichlorodifluoromethane , but without its ozone depletion potential....
. R-134 without the "a" suffix would have a molecular structure of 1,1,2,2-Tetrafluoroethane—a compound not especially effective as a refrigerant.

The same numbers are used with an R- prefix for generic refrigerants, with a "Propellant" prefix (e.g., "Propellant 12") for the same chemical used as a propellant for an aerosol spray
Aerosol spray

Aerosol spray is a type of dispensing system which creates an Particulate mist of liquid particles. This is used with a spray can or bottle that contains a liquid under pressure....
, and with trade names for the compounds, such as "Freon 12". Recently, a practice of using HFC- for hydrofluorocarbons, CFC- for chlorofluorocarbons, and HCFC- for hydrochlorofluorocarbons has arisen, because of the regulatory differences among these groups.

Blends

  • R-401A is a HCFC zeotropic blend of R-32
    Difluoromethane

    Difluoromethane, also called HFC-32 or R-32, is an organic compound of the Haloalkane variety. It is based on methane, except that two of the four hydrogen atoms have been replaced by fluorine atoms....
    , R-152a, and R-124. It is designed as a replacement for 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....
    .
  • R-404A is a HCFC "nearly azeotropic" blend of 52 wt.% R-143a
    1,1,1-Trifluoroethane

    1,1,1-Trifluoroethane, or R-143a or simply trifluoroethane, is a fluorocarbon compound that is a clear, colorless gas. It should not be confused with the isomeric compound 1,1,2-trifluoroethane....
    , 44 wt.% R-125
    Pentafluoroethane

    Pentafluoroethane, also called 1,1,1,2,2-pentafluoroethane, HFC-125, or R-125, is a refrigerant that has zero ozone depletion potential....
    , and 4 wt.% R-134a
    1,1,1,2-Tetrafluoroethane

    1,1,1,2-Tetrafluoroethane, also called simply tetrafluoroethane, R-134a, Genetron 134a, Suva 134a or HFC-134a, is a haloalkane refrigerant with thermodynamic properties similar to dichlorodifluoromethane , but without its ozone depletion potential....
    . It is designed as a replacement of R-22 and R-502 CFC. Its boiling point at normal pressure is -46.5 °C, its liquid density is 0.485 g/cm3.
  • R-406A
    R-406A

    R-406A is a refrigerant invented by George H Goble. It is a mixture of three components chlorodifluoromethane , isobutane and chlorodifluoroethane in the ratio 55/4/41....
     is a zeotropic blend of 55 wt.% 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....
    , 4 wt.% R-600a
    Isobutane

    Isobutane, also known as methylpropane or 2-methylpropane, is an alkane, isomeric with butane. Recent concerns with depletion of the ozone layer by freon gases have led to increased use of isobutane as a gas for refrigeration systems, especially in domestic refrigerators and freezers, and as a propellant in aerosol sprays....
    , and 41 wt.% R-142b.
  • R-407A is a HCFC zeotropic blend of 20 wt.% R-32
    Difluoromethane

    Difluoromethane, also called HFC-32 or R-32, is an organic compound of the Haloalkane variety. It is based on methane, except that two of the four hydrogen atoms have been replaced by fluorine atoms....
    , 40 wt.% R-125
    Pentafluoroethane

    Pentafluoroethane, also called 1,1,1,2,2-pentafluoroethane, HFC-125, or R-125, is a refrigerant that has zero ozone depletion potential....
    , and 40 wt.% R-134a
    1,1,1,2-Tetrafluoroethane

    1,1,1,2-Tetrafluoroethane, also called simply tetrafluoroethane, R-134a, Genetron 134a, Suva 134a or HFC-134a, is a haloalkane refrigerant with thermodynamic properties similar to dichlorodifluoromethane , but without its ozone depletion potential....
    .
  • R-407C is a zeotropic hydrofluorocarbon blend of R-32
    Difluoromethane

    Difluoromethane, also called HFC-32 or R-32, is an organic compound of the Haloalkane variety. It is based on methane, except that two of the four hydrogen atoms have been replaced by fluorine atoms....
    , R-125
    Pentafluoroethane

    Pentafluoroethane, also called 1,1,1,2,2-pentafluoroethane, HFC-125, or R-125, is a refrigerant that has zero ozone depletion potential....
    , and R-134a
    1,1,1,2-Tetrafluoroethane

    1,1,1,2-Tetrafluoroethane, also called simply tetrafluoroethane, R-134a, Genetron 134a, Suva 134a or HFC-134a, is a haloalkane refrigerant with thermodynamic properties similar to dichlorodifluoromethane , but without its ozone depletion potential....
    . The R-32 serves to provide the heat capacity, R-125 improves flammability, R-134a reduces pressure.
  • R-408A is a zeotropic HCFC blend of 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....
    , R-125
    Pentafluoroethane

    Pentafluoroethane, also called 1,1,1,2,2-pentafluoroethane, HFC-125, or R-125, is a refrigerant that has zero ozone depletion potential....
    , and R-143a
    1,1,1-Trifluoroethane

    1,1,1-Trifluoroethane, or R-143a or simply trifluoroethane, is a fluorocarbon compound that is a clear, colorless gas. It should not be confused with the isomeric compound 1,1,2-trifluoroethane....
    . It is a substitute for R-502. Its boiling point is -44.4 °C.
  • R-409A is a zeotropic HCFC blend of 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....
    , R-124, and R-142b. Its boiling point is -35.3 °C. Its critical temperatiure is 109.4 °C.
  • R-410A
    R-410A

    R-410A, sold under the trademarked names Puron, Genetron R410A, and AZ-20, is a near-azeotrope mixture of difluoromethane and pentafluoroethane which is used as a refrigerant in air conditioning applications....
     is a near-azeotropic blend of R-32
    Difluoromethane

    Difluoromethane, also called HFC-32 or R-32, is an organic compound of the Haloalkane variety. It is based on methane, except that two of the four hydrogen atoms have been replaced by fluorine atoms....
     and R-125
    Pentafluoroethane

    Pentafluoroethane, also called 1,1,1,2,2-pentafluoroethane, HFC-125, or R-125, is a refrigerant that has zero ozone depletion potential....
    . It's common in air conditioning systems.
  • R-500 is an azeotropic blend of 73.8 wt.% 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 26.2 wt.% of R-152a.
  • R-502 is an azeotropic blend of 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....
     and R-115
    Chloropentafluoroethane

    Chloropentafluoroethane is a chlorofluorocarbon once used as a refrigerant. Its production and consumption has been banned since 1 January 1996 under the Montreal Protocol because of its ozone-depleting potential....
    .
They also can be classified in to many other ways

See also

  • List of refrigerants
    List of refrigerants

    Chemical refrigerants are assigned an R number which is determined systematically according to molecular structure. The following is a list of refrigerants with their ASHRAE designated numbers, chemical nomenclature, molecular formula, and CAS number....
  • Refrigerant reclamation
    Refrigerant reclamation

    Refrigerant reclamation is the act of processing used refrigerant gas which has previously been used in some type of cooling loop such that it meets specifications for new refrigerant gas....


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