Refrigerant

A refrigerant is a substance used in cooling systems to transfer heat by undergoing phase changes, typically boiling and condensing at practical temperatures. It must have suitable thermodynamic properties, chemical stability, compatibility with lubricants and materials, and low toxicity for safe handling in consumer and industrial equipment.

In most systems, refrigerants operate within a closed loop in a vapor-compression cycle. A compressor raises the vapor’s pressure and temperature, sending it to a condenser where it releases heat and becomes a high-pressure liquid. The liquid passes through an expansion device, cools, and enters an evaporator where it absorbs heat and boils back into a low-pressure vapor, returning to the compressor. Some systems use absorption technology, where heat drives the circulation of the refrigerant without a mechanical compressor.

Refrigerants are categorized by their chemical classes. Halogenated refrigerants include CFCs, HCFCs, HFCs, and HFOs, while natural refrigerants include ammonia (R-717), carbon dioxide (R-744), and hydrocarbons such as propane (R-290) and isobutane (R-600a). Many halogenated refrigerants have environmental concerns, such as ozone depletion potential or high global warming potential, leading to phase‑downs and regulations. International frameworks like the Montreal Protocol and its amendments, including the Kigali Amendment, guide the reduction of ozone-depleting and high-GWP substances. Natural refrigerants can offer lower GWP but may introduce safety considerations like flammability or toxicity and often require different system designs.

Handling and servicing refrigerants involves leak detection, recovery, and reclamation, with venting typically prohibited. Refrigerants power a wide range of applications, including domestic refrigerators, air conditioning and heat pumps, and industrial cooling systems, where selection balances efficiency, safety, and environmental impact.