Refrigerant

Recycling refrigerants

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 and are very dangerous to the environment. 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 also a danger to the Earth's vital ozone layer.

As of July 1, 1992 it is illegal to release Freon or other refrigerants into the atmosphere 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.

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 the absorption or extraction of latent heat from the substances to be refrigerated.

Class 2: These refrigerants cool substances by absorbing their sensible heats. 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 latent heat.

Numbering

The R-# numbering system was developed by DuPont and systematically identifies the molecular structure of refrigerants made with a single halogenated hydrocarbon. The meaning of the codes is as follows:

• Rightmost digit: Number of fluorine molecule.
• Tens digit: One plus the number of hydrogen atoms per molecule.
• Hundreds digit: The number of carbon atoms minus one. Omitted for methyl halides, which have only one carbon atom.
• Thousands digit" Number of double bonds in the molecule. This is omitted when zero, and in practice is rarely used, since most candidate compounds are unstable.
• A suffix with a capital B and a number indicates the number of bromine atoms, when present. 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 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 azeotropic blends. The rightmost digit is assigned arbitrarily by ASHRAE, an industry organization.

For example, R-134a 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. 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, 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.

See also

• List of refrigerants

References