Refrigerants are divided based f.ex. on halogen molecules
Classification of refrigerants is based on halogen molecules. In legislation the classification is also made according to the same principle, as refrigerants are usually hydrocarbons in which hydrogen atoms have been replaced by processing halogen molecules.
Refrigerants are also categorised based on their vaporisation and condensation behaviour. In addition to this, there are “natural refrigerants,” which occur organically in nature. These are divided into HC refrigerants and inorganic refrigerants.
1. Classification of refrigerants based on evaporation and condensation behaviour
Refrigerants are divided into three separate groups based on the properties listed below:
§ Single component refrigerants; evaporation and condensation occur in the same temperature
§ Refrigerant mixtures, i.e. azeotropic refrigerants; evaporation and condensation occur in a standard temperature, e.g. R507A (identifier always begins with 5)
§ Zeotropic refrigerants with temperature variation during evaporation and condensation, e.g. R404A (identifier always begins with 4)
2. Classification of refrigerants based on halogen molecules
CFC (chlorofluorocarbon) refrigerants are partially halogenated hydrocarbon refrigerants. They contain chlorine (Cl), fluorine (F) and carbon (C), but no hydrogen (H). CFC refrigerants have high ODP and GWP values.
HCFC (hydrochlorofluorocarbon) refrigerants are partially halogenated hydrocarbons. They contain chlorine (Cl), fluorine (F), carbon (C) and hydrogen (H). HCFC refrigerants have low ODP and high GWP values.
HFC refrigerants (hydrofluorocarbons, F-gases)
HFC (hydrofluorocarbon) refrigerants are also partially halogenated hydrocarbons. They contain fluorine (F), carbon (C) and hydrogen (H). The ODP of HFC refrigerants is 0. However, they have a notably high GWP value, which means that they accelerate global warming. Single bond between carbon atoms.
PFC refrigerants (hydrofluorocarbons, F-gases)
PFC (perfluorocarbon) refrigerants are fully halogenated hydrocarbons. They only contain fluorine (F) and carbon (C). The ODP of PFC refrigerants is 0, meaning that they pose no threat to the ozone layer. However, they have a notably high GWP value, which means that they accelerate global warming.
HFO refrigerants (F-gases)
HFO (hydrofluoroolefin) refrigerants are partially halogenated hydrocarbons. They contain fluorine, carbon and hydrogen. The ODP of HFO refrigerants is also 0, and they have a low GWP value. Double bond between two carbon atoms.
3. Natural refrigerants
Natural refrigerants do not contain halogen molecules. They are divided into two groups: HC refrigerants and inorganic refrigerants.
The following are natural refrigerants: 1) various hydrocarbons (HC), 2) carbon dioxide (R744), 3) ammonia (R717), 4) water (R718) and 5) air.
HC refrigerants are clean hydrocarbons, such as R290, i.e. propane, and R600, i.e. butane.
Inorganic refrigerants are clean inorganic compounds, such as R717, i.e. ammonia, and R744, i.e. carbon dioxide. The substances are not harmful to the ozone layer and their global warming potential is also near zero. GWP values: R717 = 0 and R744 = 1.
DO YOU WANT TO KNOW MORE?
Read f.ex. this publication of Natural refrigerant case studies of Australian Government, Department of Environment and Energy