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Explain ASHRAE numbering system for refrigerants with example.

Subject:- Refrigeration and Air Conditioning

Topic:- Introduction to Refrigeration

Difficulty:- Low

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The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has developed certain conventions for use in naming different types of refrigerants. These naming conventions differ according to the type of refrigerant. Each refrigerant type is denoted by a different series. Thus, we have separate series for halogenated refrigerants and other types. The naming conventions are simple and easy to follow. These conventions are now accepted worldwide and help to name the large variety of refrigerants available commercially nowadays.

Halocarbon Compounds

These are represented by a three digit nomenclature. Here, the first digit represents the number of carbon atoms in the compound minus one, the second digit stands for the number of hydrogen atoms plus one while the third digit stands for the number of fluorine atoms. The remaining atoms are chlorine.

As an example, let us consider the refrigerant having R22 as its three digit nomenclature. According to the above mentioned convention,

No. of C atoms in R22: C – 1 = 0 => C = 1

No. of H atoms in R22: H + 1 = 2 => H = 1

No. of F atoms in R22: F = 2

Since there is only one carbon atom in the compound, this compound has originated from the methane series (CH4). From the calculation, we can see there is one hydrogen atom and two fluorine atoms. The remaining valence bond of carbon will be balanced by chlorine. Thus, the substance is

Therefore, chemical formula of R22 is CHClF2 and has the name Monochloro-difluoro-methane.

Taking again the example of R134, we can calculate its chemical formula as above which gives us

No. of C atoms: C – 1 = 1 => C = 2

No. of H atoms: H + 1 = 3 => H = 2

No. of F atoms: F = 4

Therefore, no. of Cl atoms: Cl = 0

The compound is C2H2F2 and its name is Tetrafluoroethane (Figure. 4.2). The non-halogenated refrigerants follow a different naming convention which is dependant upon the series of the refrigerant.