Refrigeration

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CFCs were invented in the late 1920s specifically in the search for a refrigerant which was thermally effective, odourless and harmless, to replace toxic gases like sulfur dioxide and ammonia. In a way, with hindsight, this was not a good move because refrigerators, freezers, chillers, air conditioners and, especially, mobile air conditioners have been responsible for a large proportion of the ozone layer depletion. If we still used ammonia and sulfur dioxide, even small leaks would have been detected very rapidly.

When the Montreal Protocol was signed in 1987, the search began for substitutes. The first candidate was HCFC-22. This was also ozone-depleting, but only about 1/20th as bad as CFC-11 or CFC-12. It was therefore considered acceptable as a temporary palliative and is scheduled for phase-out in some places as early as 2010. Another HCFC, with the same provisos, was HCFC-123. This was followed by HFC-134a, which is non-ozone-depleting but a tremendously bad greenhouse gas. Several new blends of HFC gases were also developed.

There were two gases which are eminently suitable for refrigeration, butane and propane. The problem is that they are very flammable. The refrigeration industry bitterly opposed their use on safety grounds, even though the quantity of butane in a domestic fridge would be much less than the contents of one of the popular blue camping gas reservoirs. It resulted in a ding-dong battle between the proponents and opponents, lasting several years. In 1992, Greenpeace, with the support of the Swiss government and some German companies, introduced the Greenfreeze™ refrigerator, using butane. Most domestic refrigerators for sale in Europe, China, India and Japan now use this technology - without all the dreaded doomsday forecasts of the conservative refrigeration industry. LPGs have also experimentally been used for mobile air conditioners (MACs), although most of these still use HFC-134a.

MACs have a particular problem: they leak! Not only does a crash often cause the release of all the gas, but the flexible pipework is always slightly porous, causing a very slow release over years. No matter which gas is used, occasional top-ups are inevitable. It is interesting to note that many of the cases involving criminal proceedings against companies and individuals for breaches of the US laws concerning the import and use of CFCs have been directly involved with the MAC business; it appeared lucrative to continue servicing MACs with illegally imported CFCs - until they got caught!

The majority of new split unit air conditioners for individual rooms or offices employ HFC-134a, at the time of writing. Butane would be unsuitable for this because there can be no guarantee that incompetent installers would evacuate all the air when joining the two units and the possibility of a small explosion could not be ruled out. The use of a non-flammable gas is therefore imperative for this application.

Large refrigeration plants and chillers often still use ammonia.

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