Sealed System
5-17
R-134a Physical Properties:
R-134a - Tetrafluoroethane
Refrigerant of choice in automotive industry. Genetron134a replaces CFC12 for air conditioning and refrigeration
systems in commercial residential and industrial applications.
R-12 - Dichlorodifluoromethane
A versatile and widely used refrigerant. Common in reciprocating and rotary type equipment. For all types of appli-
cations, household to industrial. Also employed in some centrifugal designs and in several special
applications.
Chemical formula ................................................ CF
3
CH
2
F
Molecular weight ................................................. 102.03
Boiling point at 1 atm. .......................................... -15.1°F (-26.2°C)
Critical temperature ............................................. 214.0°F (101.1°C)
Critical pressure, psia. ......................................... 589.9
Critical density. Ib./cu. tt. ..................................... 31.97
Liquid density at 80°F (26.7°C). Ib./cu. ft. ........... 75.0
Heat of vaporization at boiling point,
Btu/lb.°F ............................................................... 92.4
Specific heat of liquid at 80°F (26.7°C).
Btu/lb.°F ............................................................... 0.341
Specific heat of vapor at constant pressure
(1 atm.) and 80°F (26.7°C), (Btu/lb.°F) ............... 0.204
*Flammable range, %volume in air. .................... None
Ozone depletion potential .................................... 0
Greenhouse warming potential (estimate) .......... 0.285
* Flame limits measured using ASTM E681 with electrically activated kitchen match ignition source per ASHRAE
Standard 34.
Comparative Cycle Performance:
Evaporator temperature = 20°F
Condenser temperature = 110°F
Suction superheat = 30°F
sub-cooling = 10°F
Compressor isentropic efficiency = 65%
12 22 134a
Evaporator pressure, psi ............................... 21.0 43.0 18.5
Condenser pressure, psi ............................... 136.4 226.3 146.4
Compression ratio ........................................ 4.23 4.17 4.86
Compressor discharge temperature, °F ........ 188.1 227.0 178.3
Coefficient of performance ............................ 2.90 2.79 2.83
Refrigerant circulation per ton, Ib./min. ......... 3.80 2.78 3.00
Compressor displacement per ton, cfm. ....... 4.51 2.82 4.55
Liquid flow per ton, cu. in. /min. .................... 83.2 67.4 71.7
Latent heat at evaporator temp., Btu/lb ......... 66.5 90.6 86.9
Net refrigeration effect. Btu/lb ....................... 52.7 72.0 66.7
Refrigerant
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