Published by ASHRAE | Written by Dr. Andy Pearson
We have thought about various refrigerant choices, and now we turn to the hydrocarbon
family, the most common of which, as a refrigerant, is propane. It has often been said that choosing a refrigerant is an exercise in compromise because there are so many competing factors to consider, and they are sometimes contradictory. Hence, there is no perfect refrigerant.
Propane scores very highly in all criteria bar one. It has a suitable pressure-temperature relationship (very similar to R-22); it has a relatively high latent heat but a low index of compression; it is cheap and readily available, and it is compatible with mineral oils—not a surprise as it is a kind of mineral oil itself! Environmentally, it also performs well, having no effect on the ozone layer and a low global warming potential - even lower than the HFOs.
Hydrocarbons are very widely used in the domestic refrigerator market, particularly in Europe where more than 85% of all refrigerators use one or other of the family.
This was not always the case, but in the early 1990s when the Berlin Wall had recently fallen and the two halves of Germany were figuring out how to live together again after a 45-year separation, a small, struggling East German refrigerator manufacturer hooked up with Greenpeace to develop a “climate-friendly” refrigerator.
Their timing was excellent; the concept of CFC-free refrigeration was quickly adopted by the German government and translated soon after into a European regulation, and all of the major European manufacturers quickly followed suit. Early systems used a mixture of propane and isobutane to match the performance of R-12, but as the technology matured equipment was developed to use isobutane.
Andy Pearson, Ph.D., C.Eng., is Group Managing Director of the Star Refrigeration Group and President of group subsidiary Azane Inc, the leading US manufacturer of low charge ammonia chillers and freezers.
This article was published in ASHRAE Journal, July 2016. Copyright 2016 ASHRAE. Reprinted here by permission from ASHRAE at www.azane-inc.com. This article may not be copied nor distributed in either paper or digital form by other parties without ASHRAE's permission. For more information about ASHRAE, visit www.ashrae.org.