Non-uniform usage of composition nomenclature may result in confusion rather than clarification

By James M. Ccrlm, P.E. Member ASHRAE

U ntil recently, refrigerants were re- ferred to by standardized designa-

tions or trade names. With increasing regulatory and legislative actions to limit production, use, or emission of specified refrigerants, a variety of composition- designating identifiers has come into use. While such nomenclature is intended to distinguish specific attributes, non-uni- form usage may result in confusion rather than clarification. Specific recommenda- tions have been developed to improve understanding.

Take dichlorodifluoromethane as an example. This widely-used fluid is known to the chemist as CC12F,, but is more recognizable to engineers and techni- cians as R-12 or Refrigerant 12. It is also commonly sold under such trade names as Genetron 12, Freon 12, and lsotron 12.' Each of these designations iden- tifies the same chemical compound (ANSIIASHRAE 1989). The history of these designations is covered in a com- panion article by Theodore Atwood (1 989).

R-12 is one of the fully-halogenated refrigerants controlled under the Mon- treal Protocol (United Nations 1987) and for which substitutes are being sought. One chlorine-free candidate is R-134a. Although the chemical compositions are identified by the numbers (in fact, the let- ter a at the end of R-134a even identifies

the specific molecular variation or iso- mer), most individuals are not conversant with the numeric shorthand used to com- municate this information.

Composition-designating prefixes have been introduced to make distinction when the chlorine content is pertinent, as in discussions of stratospheric ozone depletion due to the chlorine compo- nent. These two fluids, therefore, also are referred to as CFC-12 and HFC-134a, respectively, to note that the former is a chlorofluorocarbon and the latter is a hydrofluorocarbon.

In earlier documents, preceding general awareness of chlorine's en- vironmental impact, R-134a was some- times referred to as FC-134a to indicate that it was part of the fluorocarbon family. Similarly, R-22 was and sometimes still is identified as a CFC (chlorofluorocarbon) refrigerant, though the currently-pre- ferred prefix is HCFC-22. The distinction is that the compound contains hydrogen, as contrasted to the perhalogenated CFC-12.

The dual significance is a lower chlorine content and decreased prob- ability of the compound reaching and re- maining in the stratosphere, due to reduced chemical stability resulting from the hydrogen atom in each molecule. The significance is quantitatively re- flected in a relative ozone-depletion potential (ODP) of 0.05 for R-22, as con- trasted to ODPs of 1 .OO for R-11 and R-12. Similarly, the ODP of R-134a, which con- tains no chlorine, is zero.

Other designations also exist. Some individuals have proposed ACFC and CFCA, where the letter A refers to alter- native. These identifiers and similar ref- erences to HFA as hydrofluorocarbon alternatives have led to confusion with the acronymsfor the fluoroalkenes, some of which may be of interest as CFC substitute^.^ Diverse prefixes have been used in languages other than English. For example, R-12, R-22 and R-134a are now widely designated as FCKW 12, H- FCKW 22, and H-FKW 134a in German.3

It should not be surprising that a non-technical regulator or legislator could easily misinterpret the multiple designations of the same fluid (e.g., R-134a, FC-134a, HFC-134a, ACFC-134a, H-FKW 134a, and others) as referring to different refrigerants. Worse yet, these in- dividuals may incorrectly conclude that more candidate substitutes exist than is the case. This inference may lead to the erroneous conclusions that at least one of so many is bound to work out or that not all are being considered. The very purpose for introducing composition- designating prefixes, therefore, may be defeated by lack of a convention.

The need for composition-designa- ting prefixes raises a conflicting concern. If such designation is required, the lay- man must incorrectly assume that the number does not contain the same infor- mation. It therefore appears that the numbers are serially assigned, implying that there may not be a limit to the num- ber of available refrigerants. If hundreds or an unlimited number of options did exist, then restriction of a small number could be mistakenly perceived as incon- sequential.

As the environmental issueschange, new prefixes may be needed to distin- guish the relative merits of refrigerants. What designators will be introduced to classify refrigerants by global-warming potential (GWP) to address the green- house effect? What code will then be

I-Genetron, Freon and lsotron are the trade names of Allied-Signal Inc., E.I. duPont de Nemours and Co., and Pennwalt Corp., respec- tively. 2-The fluoroalkenes are aliphatic (open-chain) fluorocarbons with a double bond between car- bon atoms, as contrasted to the fluoroethanes in which the two carbon atoms are connected by a single bond. These compounds fall in the 1000 series of refrigerant numbering.

3-FCKW refers to Fluor-Chlor-Kohlenwasser- stoffe, the equivalent of CFC for chlorofluoro- carbon.

ASHRAE JOURNAL November 1989

© 1989 ASHRAE