Nomenclature for Refrigerants

The refrigerant code is specified in the standard (ASHRAE Standard 34-67) formulated by the American Society of Heating and Refrigeration Engineering in 1967. The numbering method of this standard is to associate the code of the refrigerant with its species and chemical composition. As long as you know its chemical formula, you can write its code. The code name is made up of the letter “R” followed by a number. R stands for refrigerant (refrigeration medium) “Refrigerant” (previously F stands for Freon, and currently the internationally recognized R is used to name the refrigerant).

1. Inorganic Compound Refrigerants

Such as ammonia named: R717 (molecular formula NH3)

“7” represents inorganic compounds, and 17 is an integer part of its molecular weight.

2. Freon Refrigerant

Freon is a general term for derivatives of halogen elements of saturated hydrocarbons (alkanes).

The molecular formula of saturated hydrocarbons is CmH2m+2. When H2m+2 is partially or fully substituted by fluorine, chlorine, or bromine, the resulting derivative is CmHnFxClyBrz, which is the general molecular formula of Freon, and n+x+ y+z=2m+2.

For the methane system, since m=1, so n+x+y+z=4

For the ethane system, since m=2, so n+x+y+z=6

The code name of Freon is composed of R(m-1)(n+1)(x)B(z). If z=0, B can be omitted, for example:

Difluoro-chloromethane, the molecular formula is CHF2Cl, m-1=0, n+1=2, x=2, z=0, so the code is R22.

Difluorodichloromethane, the molecular formula is CF2Cl2, m-1=0, n+1=1, x=2, z=0, so the code is R12.

3. Saturated Hydrocarbons

The code numbering rules are the same as Freon, such as:
Methane is R50
Ethane as R170
Propane as R290
But butane is not written according to the above rules and is written as R600.
In addition, if it is an allotrope, add the letter “a” after the code or add a number to the single digit, such as isodifluoroethane is R152a, isobutane is R600a, etc.

4. Cyclic Compounds

Cyclic organic compounds are written by adding a letter “C” after R and then writing according to the Freon numbering rules, such as:

Hexafluorodichlorocyclobutane writing RC316

Octafluorocyclobutane writing RC318

5. Unsaturated Hydrocarbons and Their Halogen Derivatives

For this type of refrigerant, write a “1” after R, and then write it according to the numbering rules of Freon. like:

Ethylene is R1150

Propylene as R1270

Difluorodichloroethylene is R1112a.

6. Azeotropic Refrigerant

It is formed by mixing two or more single refrigerants that are mutually soluble in a certain proportion at room temperature. The components are the same.

For azeotropic refrigerants, the standard stipulates that the first number after R is “5”, and the two digits after it is numbered in the practical order. Such as R500, R501, R502… R507.

7. Non-azeotropic Refrigerants

A solution composed of two or more single refrigerants that do not form an azeotropic solution with each other. When the solution is heated, under a certain evaporation pressure, the more volatile components evaporate in a large proportion, and the less volatile components evaporate. Therefore, the composition of the gas and liquid phases is not the same, and the temperature of the refrigerant changes during the evaporation process, and it also has similar characteristics during the condensation process.

The non-azeotropic refrigerant has not been numbered in the refrigerant numbering standard, but the numbering sequence of No. 400 after R is reserved for supplementary numberings, such as R400, R401, R402, …R411.