2019 RETA Breeze Sept-Oct

SERVICE

Carbon Dioxide Refrigerant Why Not? By Peter Lepschat Director of Engineering, Henningsen Cold Storage Co.

to be able to produce a synthetic compound that had the characteristics needed to be a good refrigerant, so the inventors of the time looked to chemicals occurring in nature that might be usable as a working fluid in their systems. Unfortunately, most of them had drawbacks, i.e. ammonia is toxic, and carbon dioxide operates at pressures that were considered very high for the materials available at that time. Nonetheless, they were the only thing available, so workarounds for their drawbacks were contrived and they were used in great quantity. Of course, everything changed during the 1920’s when rapid advances in the field of chemistry lead to the synthesis of chlorofluorocarbon compounds, which at the time were considered a miraculous invention. The original one (R-12) possessed very good physical properties, operated at relatively low pressures and was non toxic to people (but not ozone as we discovered much later!). It was also relatively inexpensive to manufacture, and so the industry

rapidly converted over to it and its “cousins” that came along soon after. Fast forward to recent times. We have discovered that the chlorine in CFC’s harm the earth’s protective layer of ozone, so we replaced them with HCFCs which had less chlorine, and then HFCs which contain no chlorine. Next, we discovered that the HFCs we thought were the answer were very effective insulators, trapping solar heat at the surface of the planet, so we decided they needed to go away as well. Unfortunately, our environmental knowledge has outrun our chemical engineering expertise and the industry has come to the point that they have no safe, non-ozone depleting, non- global warming, non-flammable, non-toxic synthetic chemical compounds available. In the meantime, advances in the fields of metallurgy and engineering allowed for the invention of much stronger ma- terials, and much more efficient ways to compress, condense and evaporate refrigerants. These advancements

You may have recently heard about a “new” refrigerant out there called carbon dioxide or “CO2” and wonder what all the fuss is about. You may have also heard a lot of stories about how it is inefficient, dangerous, and unreliable. This article has been written to help dispel mis- information that seems to sur- round the use of this compound in industrial refrigeration. Firstly, this refrigerant is by no means “new”. In fact, it, and our old friend am- monia are two of the original refriger- ants, and both were widely used from the dawn of mechanical refrigeration in the 1880’s up until the 1940’s for carbon dioxide, while ammonia con- tinues to be a refrigerant of choice for industrial systems to this day. Back in the early days, chemical engi- neering was not sophisticated enough

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