Modern Engineering Thermodynamics

14.7 Refrigerant Numbers 549
14.7 REFRIGERANT NUMBERS
Most halogenated hydrocarbons used in refrigeration have a molecular structure of the form C a H b Cl c F d and the
atomic valences require that c = 2(a +1)− b − d. These compounds are given refrigerant R numbers defined by
C a H b Cl c F d is refrigerant number: R-ða − 1Þðb + 1Þd, where c = 2ða + 1Þ − b − d (14.8)
When a = 1, then a − 1 = 0 (the methane series of halogenated hydrocarbons) and the zero is omitted in the R
number. For example, carbon tetrachloride, CCl 4 ,hasa = 1, b = 0, c = 4, and d = 0. Consequently, its R number
is R-(0)(0 + 1)0 = R-010 = R-10.
Bromate compounds are indicated with a B after the R number followed by the number of bromine atoms. For
example, CBrF 3 = R-13B1. Also, ethane and higher hydrocarbon bases can have numerous isomers (compounds
containing the same number of atoms, but assembled in different ways). In these cases, the most symmetrical
atomic arrangement is given the base R number R-(a − 1)(b +1)d, and the remaining arrangements are given
the suffixes a, b, c, and so forth as the refrigerant molecule become less and less symmetrical. For example the
differences between R-134 (CHF 2 -CHF 2 ) and R-134a (CH 2 FCF 3 ) are illustrated next:
F F H F
H C C H F C C F
F F H F
R 134 R 134a
Therefore, Midgley’s CCl 2 F 2 with a = 1, b = 0, c = 2, and d = 2becameRefrigerant-12 (abbreviated R-12), or
Freon-12 if manufactured by DuPont. Similarly, CHClF 2 (a = b = c = 1, d = 2) became Refrigerant-22 or R-22,
CCl 3 F(a = 1, b = 0, c = 3, d = 1) became Refrigerant-11 or R-11, and so forth. Ethane-based refrigerants are the
100 number series, and the ethane-based hexachloroethane C 2 Cl 6 (a = 2, b = 0, c = 6, d = 0) became Refrigerant-110
or R-110, and so forth. Propane-based refrigerants are the 200 number series, and butane-based refrigerants
are assigned the 600 number series. Inorganic (i.e., nonhydrocarbon based) refrigerants are assigned the
700 number series with the last two digits being the molecular mass of the refrigerant. For example, ammonia,
NH 3 ,isRefrigerant-717 and water, H 2 O, is Refrigerant-718. Table 14.1 lists the ASHRAE number, chemical
formula, and boiling point of some common refrigerants. Figure 14.14 presents typical saturation temperaturepressure
curves for some common refrigerants plus a graphical representation of the refrigerant derivatives of
methane, CH 4 , and ethane, C 2 H 6 .
Table 14.1 The American Society of Heating, Refrigerating and Air-Conditioning Engineers
Refrigerant Numbering System for Some Common Refrigerants
Boiling Point at Atmospheric Pressure
Refrigerant Number
Chemical Formula
°F °C
R-10 CCl 4 170.2 76.8
R-11 CCl 3 F 74.9 23.8
R-12 CCl 2 F 2 −21.6 −29.8
R-21 CHCl 2 F 48.1 8.9
R-22 CHClF 2 −41.4 −40.8
R-30 CH 2 Cl 2 105.2 40.7
R-40 CH 3 Cl −14.8 −23.8
R-50 CH 4 (methane) −259.0 −161.7
R-110 C 2 Cl 6 365.0 185.0
R-111 C 2 Cl 5 F 279.0 137.2
R-112 C 2 Cl 4 F 2 199.0 92.8
R-123 CHCl 2 CF 3 81.7 27.6
R-134a CH 2 FCF 3 −15.7 −26.2
R-170 C 2 H 6 (ethane) −127.8 −88.8
R-290 C 3 H 8 (propane) −43.7 −42.1
R-600 C 4 H 10 (butane) 33.1 0.6
R-717 NH 3 (ammonia) −28.0 −33.3
R-718 H 2 O (water) 212.0 100.0
Source: Reprinted by permission from the ASHRAE Handbook—1985 Fundamentals.