GREEN GUIDE PART ONE A brief history...
Richard Parvin, technical manager at Pacair walks us through the development of refrigerants since the First World War.
O
n January 31 2020, the United Kingdom’s migration from the European Union was confirmed.
The event was met with emotions that
ranged from delight to despair but a lot of apathy too. We all knew that the word of the year would once again be the annoying but effective ‘Brexit’, invented by Peter Wilding in 2012. It felt as though its position in every political debate and news bulletin was already rubber-stamped.
But that was before Covid-19. A century ago, the world was recovering from the First World War and the even more deadly, 1918 (Spanish) flu pandemic, considered to be the consequence of poor food hygiene. As a result, the United States introduced a series of laws that required meat and dairy products to be refrigerated while in commercial storage.
Blocks of ice extracted from the Arctic Circle were still commonly used – one ton of ice melting in one day would extract heat at a rate of 3.5 kW. Mechanical refrigeration was being developed, but then – as now – the useful ingredients in the refrigerant technician’s chemistry set were hydrogen, carbon, nitrogen, oxygen, fluorine, sulphur, chlorine and bromine. Early refrigerants included sulphur dioxide, methyl chloride and ammonia. While effective, they’re all toxic, flammable or explosive and in addition, ammonia is extremely corrosive to copper. In the late 1920s, General Motors’ Frigidaire division assembled a team that included Thomas Midgley Jr. – who had previously been credited with adding lead to petrol – to create a refrigerant that was neither
38 June 2020 toxic, nor flammable. The result was the
first chlorofluorocarbon (CFC), which would be designated as R12. Not only did it meet its original objectives but it was easy to produce and compatible with all materials convenient to use (copper, brass and steel). No longer requiring the refrigerant to be isolated from the conditioned space, direct expansion ‘fridges’ became available for the first time.
Further developments of the ‘Freon’ series of refrigerants continued and in 1946 a hydro chlorofluorocarbon (R22) was found to require smaller heat exchangers and compressors. These features were to make it the refrigerant of choice most types of air conditioners for the next fifty years. In 1985, Joe Farman, Brian Gardiner and Jonathan Shanklin announced the discovery of the annual depletion of ozone above the Antarctic. Chlorinated compounds were considered to be the problem and this led to CFCs being phased out through the
Montreal Protocol in 1996 – R22 would be phased by 2015.
So it was back to the drawing board. The chemistry set still only had eight ingredients but chlorine was no longer available. This was to become the era of hydrofluorocarbons (HFCs); R12 was replaced by R134a, possessing similar pressure and temperature properties. Replacing R22 didn’t prove easy – the
original contender was R32 but was discounted as its flammability put it in the A2 safety group. Diluting it with an equal proportion of the fluorine-heavy R125 reduced its efficiency slightly, but more importantly, this blend (R410A) was non-flammable in the A1 safety group. Air conditioning products now had a safe,
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