Why were fluorinated refrigerants adopted, and what are the options for the future?

Understanding the historical success of F-gases

 

A recent review ^[1] by Mark O. McLinden, researcher at the US National Institute of Standards and Technology (NIST), published in the International Journal of Refrigeration, examines the evolution of refrigerants and the thermodynamic properties that have contributed to the widespread use of fluorinated gases (F-gases) in refrigeration and air-conditioning systems.

 

The development of halogenated refrigerants in the 1930s represented a major advancement in refrigeration safety, providing alternatives to the flammable or toxic working fluids commonly used at the time. Their adoption was further supported by favourable thermodynamic characteristics, which made them particularly suitable for conventional vapour-compression refrigeration cycles.

 

The review highlights that fluorine plays a dual role in refrigerant performance. Beyond its ability to reduce flammability, varying the fluorine content of a molecule allows its thermodynamic properties to be adjusted to meet the requirements of different applications. This flexibility has contributed to the development of a broad range of refrigerants offering different combinations of operating pressures, refrigeration capacities and efficiencies.

 

The technical challenges of moving away from fluorinated refrigerants

 

Environmental concerns, including the high global warming potential (GWP) of hydrofluorocarbons (HFCs) and the formation of persistent atmospheric degradation products such as trifluoroacetic acid (TFA) from some low-GWP hydrofluoroolefins (HFOs), are driving increasingly stringent restrictions on the use of F-gases. These developments are accelerating the transition towards alternatives such as ammonia (R717), carbon dioxide (R744) and hydrocarbons, including propane (R290).

 

However, the review emphasises that alternative refrigerants also present specific technical challenges. Hydrocarbons are highly flammable, requiring appropriate safety measures and refrigerant charge limitations, while ammonia presents toxicity concerns. Carbon dioxide, although non-flammable and of low toxicity, operates at high pressures and often requires transcritical cycles and more sophisticated control strategies.

 

According to the author, the upcoming restrictions to the range of available refrigerants will increasingly require refrigeration systems to be designed around the properties of the selected working fluid, rather than selecting a refrigerant that best matches an existing system. This transition may involve modified refrigeration cycles, advanced heat exchanger designs and adapted compressors to maintain efficiency and ensure safe operation.

 

The review concludes that moving away from F-gases is technically feasible, but will require continued innovation in refrigeration system design to accommodate the thermodynamic and safety characteristics of alternative refrigerants.

 

For more information, the scientific paper is available in open access in the International Journal of Refrigeration.

 

 

Sources:

[1] McLinden, M. O. (2026) Thermodynamic of refrigerants: Or why did we ever go with the F-gases? International Journal of Refrigeration 190 (2026) 107033. https://doi.org/10.1016/j.ijrefrig.2026.107033