Refrigerant

A refrigerant is a chemical substance that is found in an air conditioner, a refrigerator, and in other refrigeration equipment. ^[1][2] Air conditioners work by circulating refrigerant through coils, absorbing heat from the air and releasing it outside, cooling the space with chilling efficiency. ^[3]Refrigerants are chosen for the ease of converting them from liquid to vapor or vice versa, depending on their temperature and pressure. Most refrigerants in their liquid state will evaporate very fast if at atmospheric pressure. They can be classed as CFC, HCFC, HFC, HC, or HFO along with less common types.

Refrigeration cycle

A can of R407c refrigerant.

A basic diagram of a HVAC system

In refrigeration equipment, a refrigerant vapor is compressed by a compressor. Compression makes it hot. It enters a condenser, where it condenses into a liquid. The refrigerant then passes through a part called a metering device, or an expansion device (there are several types of this part) where the pressure is reduced to a point where the liquid begins to boil. At this point, the refrigerant is very cold and it enters an evaporator, where it absorbs heat from the air passing over it. By the time the refrigerant leaves the evaporator, it is all a vapor again, and it goes back to the compressor where the cycle begins again. This is called the refrigeration cycle. This is one example of the use of a refrigerant, in a residential air conditioning system.

Phase out of chlorine-based refrigerants

Older chlorine and carbon based refrigerants such as Freon R22 have been phased out due to ozone depletion. The chlorine molecule in them was found to be depleting the ozone molecules in the atmosphere. ^{[4] [5]} As a result, the Montreal Protocol has been adopted. The treaty bans the production of CFCs, halons and other ozone-depleting chemicals such as carbon tetrachloride and trichloroethane.

Types of Refrigerants ^[6]

Type	Meaning	Atoms in the Molecule
CFC	Chlorofluorocarbon	Cl, F, C
CFO	Chlorofluoroolefin
HCFC	Hydrochlorofluorocarbon	H, Cl, F, C
HCFO	Hydrochlorofluoroolefin
HFC	Hydrofluorocarbon	H, F, C
HFO	Hydrofluoroolefin
HCC	Hydrochlorocarbon	H, Cl, C
HCO	Hydrochloroolefin
HC	Hydrocarbon	H, C
HO	Hydroolefin (Alkene)
PFC	Perfluorocarbon	F, C
PFO	Perfluoroolefin
PCC	Perchlorocarbon	Cl, C
PCO	Perchloroolefin
H	Halon/Haloalkane	Br, Cl (in some but not all), F, H (in some but not all), C