1. Chapter 14C: REFRIGERANTS
Agami Reddy (rev- May 2017)
Contents
Background
Classification
Designation systems
Desirable thermodynamic properties
Desirable physical and, chemical properties
Health safety
Ozone depletion potential
Global warming potential
International protocols for refrigerant phaseout
HCB 3- Chap 14D: Refrigerants

2. HCB 3- Chap 14D: Refrigerants
Background
Choice of suitable refrigerants is influenced by:
- their thermodynamic properties which impact the energy efficient operation of the vapor compression system
their physical and chemical properties which impact safety, toxicity, stability, reliability, material compatibility
their environmental impact:
- ozone depleting potential (ODP),
- global warming potential (GWP),
- life cycle climate performance (LCCP).
This has resulted in international efforts to phase out certain well-established refrigerants, and to develop more benign ones.
HCB 3- Chap 14D: Refrigerants

3. HCB 3- Chap 14D: Refrigerants
Classification
There is no single set of optimum characteristics for refrigerants (especially for thermodynamic properties), and so tradeoffs are to be made among desirable characteristics. Thus, a variety of refrigerants having a range of properties have been developed to meet the requirements of various applications.
Azeotropes are mixtures of different substances whose composition and saturation temperature do not vary when boiled and have properties different from each constituent. They behave like simple pure substances
Zeotropic blends, which change composition when boiled at constant pressure, and so can be separated into their components by distillation. These are used extensively in absorption systems, and also in VC systems
HCB 3- Chap 14D: Refrigerants

4. HCB 3- Chap 14D: Refrigerants
Table Classification of Common Refrigerants
Refrigerant class
Numerical
Designation
Chemical Name
Chemical Formula
Safety+
ODP+
GWP+
(100 yr)
Inorganic
(naturally occurring)
717
744
718
Ammonia
Carbon dioxide
Water
NH3
CO2
H2O B2 A1
<1 1
Halocarbon
(contain chlorine, fluorine or bromine)- largest market share 11 12 22
134a
502*
Trichloromonofluoro-
methane
Dichlorodifluoro-
Monochlorodifluoro-
Tetrafluoroethane -
CCl3F
CCl2F2
CHClF2
CH2FCF3
CClF2CF3
0.82
0.034
0.221
4600
10600
1700
~ 1400
4500
Hydro-
carbon
(not used) 50
170
290
Methane
Ethane
Propane
CH4
C2H6
C3H8 A3 23
~20
Organic (naturally occurring)
600
630
Butane
Methylamine
C4H10
CH3NH2
HCB 3- Chap 14D: Refrigerants
ODP is the ozone depletion potential and
GWP is a global warming potential indictor relative to carbon dioxide.

5. HCB 3- Chap 14D: Refrigerants
Designation System
HCB 3- Chap 14D: Refrigerants

6. HCB 3- Chap 14D: Refrigerants
Inorganic compounds are numbered by adding 700 to their molecular weight, a rather arbitrary methodology.
Therefore, ammonia (molecular weight = 17) is numbered R-717.
Azeotropic mixtures use a serial numbering system beginning with 500 are not related to the chemical composition.
As an example, a mixture of R-22 and R-115 on a mass basis of 48.8% and 51.2% respectively is designated by R-502.
Zeotropic blends are also arbitrarily designated by the 400 series followed by the weight proportion of the components.
For example, a mixture of 92% R-502 (azeotrope of R-22 and R-115) with 8% propane (R-290) will be designated by R-290/22/115(8/45/47).
HCB 3- Chap 14D: Refrigerants

7. HCB 3- Chap 14D: Refrigerants
Common Refrigerants
Substitute
R-12 Car A/C, household refrigerators HFC-134a
R-11 large centrifugal chillers R123
R-22 Window A/C R407c
R410a
HCB 3- Chap 14D: Refrigerants

8. Thermodynamic Properties
Desirable characteristics are:
High latent enthalpy of vaporization i.e., a large refrigeration effect per unit mass,
High critical pressure which results in reduced compressor power,
Positive evaporating pressures will prevent atmospheric air leaking into refrigerant piping during operation,
Low but positive condensing pressures will allow lightweight equipment and piping to be used, and
Low temperature of vapor leaving compressor.
HCB 3- Chap 14D: Refrigerants

9. Operational Comparison
Table Comparison of different refrigerants in terms of performance
between the operating temperatures of Tevap= -15o C and Tcond = 30o C
Refrigerant
Evaporation pressure
(MPa)
Condens. pressure
Comp.
ratio
(-)
Compressor exit temp.
(o C)
Refrigerating effect
(kJ/kg)
Refrigerant flow rate
(kg/s.kW)
COPstd
Refrigerating efficiency
R-12
0.183
0.745
4.07 38
116.58
4.69
0.818
R-22
0.296
1.192
4.03 53
162.46
4.75
0.829
R-114
0.047
0.252
5.41 30
99.19
4.44
0.774
R-134a
0.160
0.770
4.81 43
150.71
4.42
0.771
R-502
0.349
1.319
3.78 37
104.39
4.43
0.773
R-717
0.236
1.164
4.94 98
4.84
0.844
HCB 3- Chap 14D: Refrigerants

10. HCB 3- Chap 14A: Refrigeration Cycles and Systems
Fig
HCB 3- Chap 14A: Refrigeration Cycles and Systems

11. HCB 3- Chap 14A: Refrigeration Cycles and Systems
Another important practical consideration
HCB 3- Chap 14A: Refrigeration Cycles and Systems

12. Desirable Physical and Chemical Characteristics
Good thermodynamic properties such as density and specific heat,
Good transport characteristics, i.e., properties conducive to high heat transfer such as thermal conductivity and viscosity,
Noncorrosive in the presence of water and inert in terms of material used in the piping and components,
High dielectric strength of vapor (a factor in hermetically sealed compressors where vapor comes in contact with motor windings),
Low oil solubility (to maintain lubrication and prevent oil logging in the evaporator),
Low water solubility (so as to avoid freezing the expansion device),
Inert (non-reacting with piping materials), and
Stable over time.
HCB 3- Chap 14D: Refrigerants

13. HCB 3- Chap 14D: Refrigerants
Health Safety
HCB 3- Chap 14D: Refrigerants

14. HCB 3- Chap 14D: Refrigerants
Ozone Depletion
CFCs are very stable and persist in the atmosphere for many years
Once in the upper atmosphere, CFC molecules break down and Cl is released which destroys the ozone layer
In the lower atmosphere, the molecules absorb infrared radiation which contributes to global warming
Ozone Depletion Potential (ODP) is a normalized index of the ozone destruction potential with 1.0 assigned to R-11.
See Table 14.5
HCB 3- Chap 14D: Refrigerants

15. International Protocols
Original 1987 Montreal protocol
- limited the 1998 production of certain CFCs to 50% of their 1986 levels
- Starting in 1991, the production of certain CFCs was frozen at their 1986 levels
Copenhagen Amendment, 1994
- production of all CFC-based refrigerants stopped by 1995 (R-11, R-12, R-502)
- existing stock can be used
HCB 3- Chap 14D: Refrigerants

16. Global Warming Potential (GWP)
The major environmental concern currently is not ozone, but rather the impact of refrigerants on climate change.
Released refrigerants in the lower atmosphere trap the infrared radiation from the earth thereby contributing to the greenhouse effect.
GWP is used to characterize this effect with that of carbon dioxide over a time duration of 100 years taken as the reference value of unity.
Notice the very large GWP values for the halocarbon family of compounds (Table 14.15).
HCB 3- Chap 14D: Refrigerants

17. HCB 3- Chap 14D: Refrigerants
Fig Map of refrigerant evolution showing routes being taken in the phase-out of CFCs and HCFCs. Refrigerants in the future are likely to be the natural refrigerants, HFCs, unsaturated HFCs (also known as HFOs), and possibly blends of these refrigerants (©ASHRAE, (2012)
HCB 3- Chap 14D: Refrigerants

18. HCB 3- Chap 14D: Refrigerants
The refrigerants of primary concerns for ozone depletion are the CFCs which include R-11, R-12 and R-502; these were the most destructive to the ozone layer and are first to be phased out.
Regulations are in place to phase out HCFCs as well:
- R-123 is now being used to temporarily replace R-11 but is causing efficiency reduction and certain operational problems, and is likely to be phased out in 10 years.
- R-134a appears to be a satisfactory substitute for R-12.
The HFC compounds are the least harmful to the ozone layer since they do not contain any chlorine, but their use is also being restricted due to global warming potential. Some of these “drop-in” replacements, in turn, are likely to be replaced by more benign compounds in the future such as natural refrigerants (Fig )
HCB 3- Chap 14D: Refrigerants

19. HCB 3- Chap 14D: Refrigerants
Outcomes
Understanding of the different types of considerations involved in selecting refrigerants
Understanding of how refrigerants are classified
Understanding of the designation system of refrigerants
Knowledge of the desirable thermodynamic properties of various refrigerants and use of relevant tables
Knowledge of the desirable physical and chemical properties of various refrigerants and use of relevant tables
Understanding of the health safety categories
Knowledge of the ozone depletion potential of refrigerants
Knowledge of the global warming potential of refrigerants
Understanding of the various international refrigerant phase-out efforts to mitigate environmental concerns
HCB 3- Chap 14D: Refrigerants