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Sponsored by REFRIGERANTS


A common sense approach


Dick Powell of Refrigerant Solutions takes a look at the pros and cons of natural refrigerants.


T 4 “Those


who cannot remember the past are condemned to repeat it.”


George Santayana, The Life of Reason 1905


his article is a plea for common sense in deciding how the refrigeration industry should develop as it seeks to minimise its environmental impact. We are concerned that arguments, especially promulgated by green activists, are dangerously distorting what should be a predominantly technical discussion.


Ninety years ago, the hitherto steady growth of refrigeration hit a barrier – the hazardous nature of the refrigerants then available.


Customers vomiting outside an American diner was not a comment on the food, but a sign that the establishment’s refrigerator had leaked sulphur dioxide. General Motors, owner of Frigidaire, tasked a senior engineer, Thomas Midgley to find safe refrigerants. Working with chemists Albert Henne and Robert Nary, he identified CFCs and HCFCs as non-toxic, non-flammable and efficient fluids, which enabled the industry to grow rapidly, bringing the undisputed benefits of refrigeration and air conditioning to millions, especially after the second world war. Atmospheric knowledge was insufficiently advanced when CFCs and HCFCs were introduced to anticipate their environmentally adverse effects.


Concern was first expressed only in the early 1970s following Lovelock’s measurements of atmospheric CFC-11 levels, leading to Rowland and Molina’s 1974 hypothesis of Stratospheric ozone depletion, subsequently confirmed in 1984 by the discovery of the Antarctic ‘Ozone Hole’.


In searching for replacements, the refrigeration industry wanted the same inherent safety at point of use, long provided by CFCs/HCFCs, but without troublesome ozone depletion. HFCs offered a solution, yet around the time of their introduction concern about global warming was increasing and it was realised that they might be contributors. Greenpeace promoted its ‘GreenFreeze’ technology as the environmentally friendly alternative to the HFCs, using hydrocarbons both as refrigerant and foam blowing agent. But the London Fire Brigade was by now expressing considerable concern about fatal fires linked to flammable fridges. Yet, in contrast to CFC-related ozone depletion in the 1930s, the high flammability of HCs was already well known and was an original reason for preferring CFCs.


Hydrocarbons are not the only ‘natural’ refrigerants causing problems. We also note regular reports of ammonia leaks causing injuries and fatalities, even in countries with high standards and despite 150 years of accumulated industrial experience. ‘Natural’ most certainly does not necessarily mean low hazard.


Can the refrigerant industry have what it really wants, namely refrigerants that have both low environmental impact and low hazard at point of use?


The best natural bets are water, air and carbon dioxide, which avoid the toxicity/flammability hazards of ammonia and hydrocarbons and the high GWP of the HFCs. But they also have problems.


Water used in cooling towers can be regarded as a consumable refrigerant that significantly improves efficiency, but unless treated regularly with a biocide can result in legionnaire disease fatalities.


Liquid nitrogen derived from air is being mooted for transport refrigeration, a fascinating development that both reduces vehicle derived pollution and incorporates coolth storage. But nitrogen is an asphyxiant.


Liquid air is a safer alternative in this respect, but it can fractionate during evaporation resulting in oxygen enrichment increasing flammability hazards.


Carbon dioxide is an asphyxiant, although its acidic smell and induction of panting gives warning of a leak. High engineering integrity is required to avoid potentially dangerous mechanical failure. Reluctantly, we must conclude that as far as ‘natural’ refrigerants are concerned there is no free lunch, so to speak.


The great advantage of CFCs/HCFCs and HFCs was that they minimised risk of injury at point of use, even if people using them were careless and did not follow correct procedures. While accepting that the risks presented by hazardous, natural refrigerants can be minimised by proper training, they are not as forgiving as the HFCs of sloppy practice. The refrigeration industry needs to learn from the best practice in the chemical industry, which has long experience in handling dangerous substances, such as ammonia and hydrocarbons, and has needed to absorb some difficult lessons.


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