A refrigerant is a
working fluid
For fluid power, a working fluid is a gas or liquid that primarily transfers force, motion, or mechanical energy. In hydraulics, water or hydraulic fluid transfers force between hydraulic components such as hydraulic pumps, hydraulic cylinders, a ...
used in the
refrigeration cycle of
air conditioning systems and
heat pumps where in most cases they undergo a repeated
phase transition from a
liquid
A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...
to a
gas and back again. Refrigerants are heavily regulated due to their
toxicity,
flammability and the contribution of CFC and HCFC refrigerants to
ozone depletion
Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone l ...
and that of HFC refrigerants to
climate change.
Refrigerants are used in a Direct Expansion (DX) system to transfer energy from one environment to another, typically from inside a building to outside (or vice versa) commonly known as an "air conditioner" or "heat pump". Refrigerants can carry per kg 10 times more energy than water and 50 times more than air.
Refrigerants are controlled substances due to 1) High Pressures (100-145 psi), 2) Extreme temperatures (-50°C to 145°C), 3) Flammability A1 class non-flammable, A2/A2L class flammable & A3 class extremely flammable/explosive and 4) Toxicity B1-low, B2-medium & B3-high, as classified by ISO 817 & ASHRAE 34.
Refrigerants must only be handled by qualified/certified engineers to the relevant classes of refrigerant eg in the UK C&G 2079 if A1 class PLUS C&G 6187-2 if A2/A2L & A3 class refrigerants.
History
The first air conditioners and
refrigerator
A refrigerator, colloquially fridge, is a commercial and home appliance consisting of a thermally insulated compartment and a heat pump (mechanical, electronic or chemical) that transfers heat from its inside to its external environment so th ...
s employed toxic or flammable gases, such as
ammonia,
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
,
methyl chloride, or
propane
Propane () is a three-carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used a ...
, that could result in fatal accidents when they leaked.
In 1928
Thomas Midgley Jr.
Thomas Midgley Jr. (May 18, 1889 – November 2, 1944) was an American mechanical and chemical engineer. He played a major role in developing leaded gasoline (tetraethyl lead) and some of the first chlorofluorocarbons (CFCs), better known i ...
created the first non-flammable, non-toxic chlorofluorocarbon gas, ''
Freon'' (R-12). The name is a
trademark name owned by
DuPont
DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in ...
(now
Chemours) for any
chlorofluorocarbon (CFC),
hydrochlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propan ...
(HCFC), or
hydrofluorocarbon (HFC) refrigerant. Following the discovery of better synthesis methods, CFCs such as
R-11,
R-12, R-123
and R-502
dominated the market.
Phasing out of CFCs
In the early 1980s, scientists discovered that CFCs were causing major damage to the
ozone layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in rela ...
that protects the earth from ultra-violet radiation, and to the
ozone holes over polar regions. This led to the signing of the
Montreal Protocol in 1987 which aimed to phase-out CFCs and HCFC but did not address the contributions that HFCs made to climate change. The adoption of HCFCs such as
R-22, and R-123
was accelerated and so were used in most U.S. homes in air conditioners and in
chillers from the 1980s as they have a dramatically lower Ozone Depletion Potential (ODP) than CFCs, but their ODP was still not zero which led to their eventual phase-out.
Hydrofluorocarbons (HFCs) such as
R-134a
1,1,1,2-Tetrafluoroethane (also known as norflurane (INN), R-134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with thermodynamic properties si ...
,
R-143a,
R-407a R-407A is a mixture of gasses used as a refrigerant. It is a zeotropic blend of difluoromethane (HFC-32), pentafluoroethane (HFC-125) and 1,1,1,2-tetrafluoroethane (HFC-134a). R-407A was developed as a close match to R-22's capacities and flow ra ...
,
R-407c,
R-404a and
R-410a (a 50/50 blend of
R-125
Pentafluoroethane is a fluorocarbon with the formula CF3CHF2. Pentafluoroethane is currently used as a refrigerant (known as R-125) and also used as a fire suppression agent in fire suppression systems.
Pentafluoroethane does not deplete ozone so ...
/
R-32) were promoted as replacements for CFCs and HCFCs in the 1990s and 2000s. HFCs were not ozone depleting but did have
global warming potentials (GWPs) thousands of times greater than CO
2 with atmospheric lifetimes that can extend for decades. This in turn, starting from the 2010s, led to the adoption in new equipment of Hydrocarbon and HFO (
hydrofluoroolefin) refrigerants R-32, R-290,
R-600a,
R-454b,
R-1234yf
2,3,3,3-Tetrafluoropropene, HFO-1234yf, is a hydrofluoroolefin (HFO) with the formula CH2=CFCF3.
It is also designated R-1234yf as the first of a new class of refrigerants: it is marketed under the name Opteon YF by Chemours and as Solstice YF by ...
, R-514A, R-744 (),
R-1234ze and R-1233zd, which have both an ODP of zero and a lower GWP. Hydrocarbons and are sometimes called natural refrigerants because they can be found in nature.
The environmental organization
Greenpeace
Greenpeace is an independent global campaigning network, founded in Canada in 1971 by Irving Stowe and Dorothy Stowe, immigrant environmental activists from the United States. Greenpeace states its goal is to "ensure the ability of the Earth t ...
provided funding to a former East German refrigerator company to research alternative ozone- and climate-safe refrigerants in 1992. The company developed hydrocarbon mixes such as
isopentane and
isobutane
Isobutane, also known as ''i''-butane, 2-methylpropane or methylpropane, is a chemical compound with molecular formula HC(CH3)3. It is an isomer of butane. Isobutane is a colourless, odourless gas.
It is the simplest alkane with a tertiary carbon a ...
, propane and isobutane, or pure isobutane, called "Greenfreeze", but as a condition of the contract with Greenpeace could not patent the technology, which led to their widespread adoption by other firms.
Policy and political influence by corporate executives resisted change however, citing the flammability and explosive properties of the refrigerants, and DuPont together with other companies blocked them in the U.S. with the U.S. EPA.
Beginning on 14 November 1994, the
U.S. Environmental Protection Agency
A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
restricted the sale, possession and use of refrigerants to only licensed technicians, per rules under sections 608 and 609 of the Clean Air Act. In 1995, Germany made CFC refrigerators illegal.
In 1996
Eurammon
Eurammon (stylised as eurammon) is a European non-profit initiative for natural refrigerants. It was set up in 1996 and comprises European companies, institutions, and industry experts. It is based in Frankfurt (Main), Germany. The initiative's ...
, a European non-profit initiative for
natural refrigerant Natural refrigerants are substances that serve as refrigerants in refrigeration systems (including refrigerators, HVAC, and air conditioning). They are alternatives to synthetic refrigerants such as chlorofluorocarbon (CFC), hydrochlorofluorocarbon ...
s, was established and comprises European companies, institutions, and industry experts.
In 1997, FCs and HFCs were included in the
Kyoto Protocol
The Kyoto Protocol was an international treaty which extended the 1992 United Nations Framework Convention on Climate Change (UNFCCC) that commits state parties to reduce greenhouse gas emissions, based on the scientific consensus that (part ...
to the Framework Convention on Climate Change.
In 2000 in the UK, the Ozone Regulations came into force which banned the use of ozone-depleting HCFC refrigerants such as R22 in new systems. The Regulation banned the use of R22 as a "top-up" fluid for maintenance between 2010 for virgin fluid and from 2015 for recycled fluid.
Addressing greenhouse gases
With growing interest in
natural refrigerant Natural refrigerants are substances that serve as refrigerants in refrigeration systems (including refrigerators, HVAC, and air conditioning). They are alternatives to synthetic refrigerants such as chlorofluorocarbon (CFC), hydrochlorofluorocarbon ...
s as alternatives to synthetic refrigerants such as CFCs, HCFCs and HFCs, in 2004, Greenpeace worked with multinational corporations like
Coca-Cola and
Unilever, and later
Pepsico
PepsiCo, Inc. is an American multinational food, snack, and beverage corporation headquartered in Harrison, New York, in the hamlet of Purchase. PepsiCo's business encompasses all aspects of the food and beverage market. It oversees the manuf ...
and others, to create a corporate coalition called Refrigerants Naturally!.
Four years later, Ben & Jerry's of Unilever and General Electric began to take steps to support production and use in the U.S. It is estimated that almost 75 percent of the refrigeration and air conditioning sector has the potential to be converted to natural refrigerants.
In 2006, the EU adopted a Regulation on
fluorinated greenhouse gases (FCs and HFCs) to encourage to transition to natural refrigerants (such as hydrocarbons). It was reported in 2010 and some refrigerants are being used as
recreational drugs, leading to an extremely dangerous phenomenon known as
inhalant abuse.
From 2011 the European Union started to phase out refrigerants with a
global warming potential (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 CO
2) such as the refrigerant
HFC-134a
1,1,1,2-Tetrafluoroethane (also known as norflurane ( INN), R-134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with thermodynamic properties s ...
(known as R-134a in North America) which has a GWP of 1526.
In the same year the EPA decided in favor of the ozone- and climate-safe refrigerant for U.S. manufacture.
A 2018 study by the nonprofit organization "
Drawdown" put proper refrigerant management and disposal at the very top of the list of climate impact solutions, with an impact equivalent to eliminating over 17 years of US carbon dioxide emissions.
In 2019 it was estimated that CFCs, HCFCs, and HFCs were responsible for about 10% of direct
radiative forcing
Radiative forcing (or climate forcing) is the change in energy flux in the atmosphere caused by natural or anthropogenic factors of climate change as measured by watts / metre2. It is a scientific concept used to quantify and compare the external ...
from all long-lived anthropogenic greenhouse gases. and in the same year the
UNEP published new voluntary guidelines, however many countries have not yet ratified the
Kigali Amendment
The Kigali Amendment to the Montreal Protocol is an international agreement to gradually reduce the consumption and production of hydrofluorocarbons (HFCs). It is a legally binding agreement designed to create rights and obligations in internatio ...
.
With the begin of the 2020 HFCs (including R-404a, R-134a and R-410a) are being superseded: Residential air-conditioning systems and heat pumps are increasingly using
R-32. This still has a GWP of more than 600. Progressive devices use refrigerants with a almost no climate impact: R-290 (propane), R-600 (isobutane) or
R-1234yf
2,3,3,3-Tetrafluoropropene, HFO-1234yf, is a hydrofluoroolefin (HFO) with the formula CH2=CFCF3.
It is also designated R-1234yf as the first of a new class of refrigerants: it is marketed under the name Opteon YF by Chemours and as Solstice YF by ...
(less flammable, in cars). In commercial refrigeration also (R-744) can be used.
Desirable properties
The ideal refrigerant would be:
non-corrosive,
non-toxic,
non-flammable, with no
ozone depletion
Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone l ...
and
global warming potential. It should preferably be natural with well-studied and low environmental impact. It also needs to have: a
boiling point
The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.
The boiling point of a liquid varies depending upon the surrounding envir ...
that is somewhat below the target temperature (although boiling point can be adjusted by adjusting the
pressure appropriately), a high
heat of vaporization
The enthalpy of vaporization (symbol ), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas. T ...
, a moderate
density in liquid form, a relatively high density in gaseous form (which can also be adjusted by setting pressure appropriately), and a high
critical temperature
Critical or Critically may refer to:
*Critical, or critical but stable, medical states
**Critical, or intensive care medicine
*Critical juncture, a discontinuous change studied in the social sciences.
*Critical Software, a company specializing in ...
. Extremely high pressures should be avoided. Newer refrigerants address the issue of the damage that CFCs caused to the ozone layer and the contribution that HCFCs make to climate change, but some do raise issues relating to toxicity and / or flammability.
Common refrigerants
Refrigerants with very low climate impact
With increasing regulations, refrigerants with a very low
global warming potential are expected to play a dominant role in the 21st century,
in particular R-290 and R-1234yf. Starting from almost no market share in 2018,
low GWPO devices are gaining market share in 2022.
Most used
Banned / Phased out
Other
Refrigerant reclamation and disposal
Coolant and refrigerants are found throughout the industrialized world, in homes, offices, and factories, in devices such as refrigerators, air conditioners, central air conditioning systems (HVAC), freezers, and dehumidifiers. When these units are serviced, there is a risk that refrigerant gas will be vented into the atmosphere either accidentally or intentionally, hence the creation of technician training and certification programs in order to ensure that the material is conserved and managed safely. Mistreatment of these gases has been shown to deplete the ozone layer and is suspected to contribute to
global warming.
With the exception of isobutane and propane (R600a, R441a and R290), ammonia and CO
2 under
Section 608 of the United States'
Clean Air Act it is illegal to knowingly release any refrigerants into the atmosphere.
Refrigerant reclamation is the act of processing used refrigerant gas which has previously been used in some type of
refrigeration loop such that it meets specifications for new refrigerant gas. In the
United States, the
Clean Air Act of 1990 requires that used refrigerant be processed by a certified reclaimer, which must be licensed by the
United States Environmental Protection Agency (EPA), and the material must be recovered and delivered to the reclaimer by EPA-certified technicians.
Classification of refrigerants
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.
* Class 2: These refrigerants cool by temperature change or '
sensible heat', 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 cooled.
* 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. They can also be classified into many categories.
The R-# numbering system was developed by
DuPont
DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in ...
(which owned the
Freon trademark), and systematically identifies the molecular structure of refrigerants made with a single halogenated hydrocarbon. The meaning of the codes is as follows:
* For saturated hydrocarbons, subtracting 90 from the concatenated numbers of
carbon,
hydrogen and
fluorine
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reacti ...
atoms, respectively gives the assigned R#.
* If
bromine is present, the number is followed by a capital B and then the number of bromine atoms.
* Remaining bonds not accounted for are occupied by
chlorine atoms.
* ''A suffix of a lower-case letter a, b, or c'' indicates increasingly unsymmetrical
isomers.
For example,
R-134a
1,1,1,2-Tetrafluoroethane (also known as norflurane (INN), R-134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with thermodynamic properties si ...
has 2 carbon atoms, 2 hydrogen atoms, and 4 fluorine atoms, 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 (also known as norflurane (INN), R-134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with thermodynamic properties s ...
. R-134 (without the "a" suffix) would have a molecular structure of 1,1,2,2-Tetrafluoroethane.
* 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 is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation to ...
) and the R-500 series is made up of so-called
azeotropic blends. The rightmost digit is assigned arbitrarily by
ASHRAE, an industry standards organization.
* The R-700 series is made up of non-organic refrigerants, also designated by ASHRAE.
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, and with trade names for the compounds, such as "Freon 12". Recently, a practice of using abbreviations HFC- for
hydrofluorocarbons, CFC- for
chlorofluorocarbons, and HCFC- for
hydrochlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propan ...
s has arisen, because of the regulatory differences among these groups.
Refrigerant safety
ASHRAE Standard 34, ''Designation and Safety Classification of Refrigerants'', assigns safety classifications to refrigerants based upon
toxicity and
flammability.
Using safety information provided by producers, ASHRAE assigns a capital letter to indicate toxicity and a number to indicate flammability. The letter "A" is the least toxic and the number 1 is the least flammable.
See also
*
Brine (Refrigerant)
*
Section 608
References
Sources
IPCC reports
* (pb: ). https://archive.ipcc.ch/report/ar5/wg1/
**
*
*
Other
*
*
*
External links
US Environmental Protection Agency page on the GWPs of various substancesGreen Cooling Initiative on alternative natural refrigerants cooling technologiesInternational Institute of Refrigeration
{{Authority control
Heating, ventilation, and air conditioning
Industrial gases