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Associations
no chlorine and therefore had no effect on the stratospheric ozone layer . These were predominantly HFCs such as R-134a but the development of the UN Framework Convention on Climate Change through the 1990s leading up to the Kyoto Protocol in 1997 highlighted the fact that some of these fluids had a very high global warming potential . It took almost 20 years , from 1997 to 2016 , to formulate an acceptable mechanism within the UN framework for regulating the HFCs with high GWP but this has now been enacted in various jurisdictions around the world including the f-gas regulations in Europe and the AIM Act in the US . This prompted the third transition wave , from HFCs to HFOs – the so-called hydrofluoroolefins . This labelling is something of a marketing triumph since the HFOs are all HFCs ( hydrofluorocarbons ). Their key feature is that the carbon backbone of the molecule includes a double bond , which makes the molecule less stable and more likely to react with an external influence to break down into some other compound . The short atmospheric life of the HFOs means that they cannot have a strong influence on global warming because they don ’ t exist for long enough , but this has brought a new set of environmental concerns based on fears about what the HFOs turn into when they are no longer HFOs .
Moving from CFCs to HCFCs only required an adjustment of the existing technologies , needing greater care in designing oil management systems to cope with slightly reduced miscibility and designing for slightly higher operating pressures . The introduction of HFCs needed development of a new range of lubricants , the polyesters , because the absence of chlorine in the refrigerants reduced the lubricity of bearing surfaces and led to premature bearing failures when traditional mineral or synthetic oils were used . A spin-off benefit of the change of lubricant was that the new oils had less adverse effect in evaporators on the low temperature side of the system and so system efficiency could be improved as well . Operating pressures with some HFCs , for example R-32 and blends containing R-32 , are higher than required for R-22 so some system and component redesign was required . Moving from HFCs to HFOs has introduced additional difficulties , for example safe design of systems to avoid problems with the flammability of the new substances such as R-1234yf . It is fair to say that at each step of this development process the technical challenges have become more difficult and the margin for error in the process has diminished . With hindsight those early development steps look quite simple now , although they felt quite challenging at the time . RACA
Continued in Part 2 …
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RACA Journal I January 2025 www . refrigerationandaircon . co . za