This document discusses refrigerants, including their classification, properties, environmental impacts, and alternatives. Refrigerants are heat carrying fluids that absorb heat from a low temperature system and release it to a high temperature system. Natural substances like ice were early refrigerants, followed by ether, ammonia, and sulfur dioxide in the 19th century. Chlorofluorocarbons (CFCs) became popular but were later banned due to ozone depletion and global warming. Current alternatives include hydrocarbons, ammonia, carbon dioxide, and hydrofluorocarbons. An ideal refrigerant has desirable properties like high critical temperature, low boiling point, non-toxicity, stability, and being environmentally friendly.

1. Refrigerant
Prof. P.W.Ingle
Sanjivani College of Engineering Kopargaon

2. Refrigerant:- Classification of refrigerants, designation of refrigerant,
desirable properties of refrigerant, environmental issues, ozone
depletion and global warming, ODP, GWP & LCCP, selection of
environment friendly refrigerants, secondary refrigerants, antifreeze
solution, Azeotropes, Refrigerant: recovery, reclaim, recycle and
recharge
Refrigerant is a heat carrying medium which during their cycle
in the refrigeration system absorb heat from a low temperature
system and discard the heat so absorbed to a high temperature
system.
the natural ice and salt were the first refrigerants known to the
man. Subsequently, refrigerants such as ether, ammonia,
Sulphur di oxide and dry ice were developed in the
nineteenth century. Further developments in the field of
refrigeration led to the discovery of freon i.e. chloro-fluoro-
carbons (CFCs)

3. Continue…..
CFCs became extremely popular as they were stable,
non toxic, and had excellent heat transfer
characteristics. They dominated the refrigerant market
till the end of twentieth century.
However due to environmental damage caused
through the ozone depletion and global warming they
were banned in several countries. The Montreal and
Kyoto protocol are some of the international agencies
banning the use of these refrigerants
Currently alternative refrigerants are like
hydrocarbons, natural refrigerants like ammonia,
water or synthetic refrigerents such as bromine
derivative of HC are in use

4. R12, R22 are under replacement however ammonia is still popular
since it has zero ODP and GWP.
Substitute for R12, R22 is R134a, for R11 is R123, CO2 also becomes
an active refrigerant for automobile to replace R12
Again R12, R22 are replaced by HC like propane, R12,R22,R502 are
replaced by propylene
Desirable properties of refrigerant or an ideal refrigerant
An ideal refrigerant is one which would fulfill the following conditions:
1. High critical temperature 2. freezing point as low as possible. 3. low
boiling point. 4. non viscous. 5. miscibility with oil. 6. high latent of
vaporization 7. low specific heat of liquid 8. non toxic 9. Environment
friendly. 10. low cost. 11. easily available. 12. non corrosive to metal 13.
chemically stable. 14. low specific volume of vapor. 15. no flammable.
16. non explosive. 17. easy to liquify at moderate pressure and
temperature. 18. long life. 19. ease of storage and disposal.

5. The most common HFC used in air conditioners is R-410A.
This refrigerant is better than R-22 in terms of “Ozone
Depletion” potential and energy efficiency, but it still causes
global warming. A few more HFCs that are
commonly used are: R-32 in Air Conditioners and R-134A in
refrigerators
HFCs. Hydrofluorocarbons (HFCs) are nonozone-depleting,
nonflammable, recyclable, and energy-efficient refrigerants of
low toxicity that are currently used safely throughout the
world.R-134a.R-404A.R-507.R-407C.R-410A.Carbon
Dioxide. ...

6. There are many kinds of refrigerant and or Refrigerant on the market
today, but only a few that are widely used:
R-134a refrigerant is primarily used in automobile applications. It is
classified as an HFC refrigerant and has been banned in some countries
due to it’s global warming potential.
R-12 was THE refrigerant back in the 20th century for automobile
applications. It was banned in 1994 due to it harming the O-Zone layer. It
was replaced by R-134a. R-12 is an CFC refrigerant.
1234YF is a new type of refrigerant that will be slowly replacing R-134a
applications. Some automobile manufacturers have already switched
over to the new HFO class of refrigerant known as 1234YF.
R-410A is primarily used for home and commercial units made on or
after 2010. It is also an HFC refrigerant.

7. R22, R134a, R407A, R404A, R410A etc are some of the refrigerants currently
in use in India.
For Central Air conditioning systems, R134a and R22 are used in Air cooled
and Water cooled screw chillers. R407C is another refrigerant used in these
type of chillers.
Room air conditioners mainly use R410A,R22 and R32 (recently started). R32
is a Eco friendly refrigerant with very low ODP and GWP but its flammability
is slightly higher as compared to other refrigerants. R32 also leads to slightly
higher discharge temperatures at the compressor exit which increases
condenser load.
Developed countries have already stopped using R22 since R22 is a HCFC but
countries like India are permitted to use HCFC until 2030.

8. Classification of Refrigerants
1. On the basis of safety:- A. safe refrigerant, these are non toxic, non
flammable in nature e.g. CO2, H2O, R11, R12 B. Toxic refrigerant:- harmful
in nature, e.g. NH3, SO2, ethylene chloride etc. C. Flammable refrigerant:-
flammable in nature e.g. Butane, Isopropane
2. On the basis of working principle:- A. Primary refrigerant:- this refrigerant
passes through the refrigerant cycle directly. The refrigerant undergo
compression, cooling, condensation and expansion with change in phase
are known as primary refrigerant, e.g. R12, R22, CO2, NH3 B. Secondary
refrigerants:- this refrigerants does not undergo cyclic process in
refrigeration, but used only as a medium for cooling. Such refrigerant is
termed as secondary refrigerants, e.g. H2O, Brine, Calcium Chloride
solution
3. On the basis of chemical composition:- the refrigerants are classified into
four groups they are 1. halocarbon refrigerants 2. Azeotropes 3.
Hydrocarbon refrigerants 4. inorganic refrigerants.

9. Types of Refrigerant
1. Halocarbon refrigerants:- these were the most commonly used refrigerants until the ban
of these compounds due to environmental reasons. Essentially these refrigerants are
compounds of chlorine, fluorine and carbons
R11- Trichloromonofluoromethane, CCL3F
R12- Dichlorodifluoromethane, CCL2F2
R22- Monochlorodifluoromethane, CHCLF2
R40- Methyl Chloride, CH3CL
R113- Trichloro difluoroethane, CCL2FCCLF2
, all these compounds are commercially available as Freons
R11- Stable, low pressure refrigerant, non flammable, nontoxic, boiling point is 23.77
degree Celsius, high and low pressures are 1.26 bar and 0.202 bar. Used as a flushing agent
for cleaning internal parts of compressors used in refrigeration system. Used in central air
conditioning building and water chilling plant. Its leak can be detected by soap solution,
halide torch or electronic detector

10. CFC 12, R12: Another safe and non toxic refrigerant, odorless liquid with
boiling point of -29 degree Celsius at atmospheric pressure. Extreme
pressures are 0.82 bar and 6.4 bar. It has low latent heat and is useful in
small refrigerant machines. It operates at lower pressure and provides
good volumetric efficiency. It is primarily used in rotary and reciprocating
compressors but also popular for use in domestic refrigerators, freezers,
water cooler. It has good miscibility with oil. It is banned now
HCFC, R22:- Synthetic refrigerant developed for refrigeration applications
that need low evaporation temperatures such as fast freezing units. Also
used in air conditioning units such as chillers and window air conditioners.
Its boiling point is -41 degree Celsius and extreme pressures are 1.92 bar
and 10. 88 bar. This refrigerant is stable, non toxic, non corrosive. Good
miscibility with oil and leak detection is also easy

11. R40:- Methyl Chloride, colorless liquid with faint odour useful in leak
detection. Boiling point is -23.7 degree Celsius, condenser pressure is 5 bar.
It is flammable and explosive. It has a tendency of reacting with certain
metals like aluminum and zinc
R113:- Boiling point is 47.6 degree Celsius at atmospheric pressure. It is safe
refrigerant and used mostly in commercial and industrial refrigeration system
with centrifugal compressor
AZEOTROPES:- this term refers to a stable mixture of refrigerant whose vapor and liquid
phase retain identical composition over a wide range of temperatures.
1. R500, 73.8% R12 and 26.2% R152
2. R502, 48.8% R22 and 51.2% R115
3. R504, 48.2% R32 and 51.8% R115

12. R500:- non flammable, non toxic and non corrosive refrigerant mixture. It is
used in industrial and commercial applications such as large refrigerating units
with reciprocating compressor. The refrigerant has 20% greater refrigerating
capacity than its parent refrigerant R12. boiling point is -33 degree celcius at
atmospheric pressure. Soluble in oil and water.
Its leak can be detected by soap solution, halide torch or electronic detector
R502:- This is good refrigerant to obtain low temperature upto -50 degree
celcius. Non flammable non toxic liquid. Applications are frozen food lockers,
storage units, low condensing pressure and temperature.
R504:- non flammable non toxic, boiling point is -57 used for low temperature
applications. Leak detection with halide torch is easy

13. Hydrocarbon refrigerant:- these refrigerants are nothing but compounds of
hydrogen and carbons. Due to ban on CFCs considerable interest has been
generated in exploration of this refrigerants as an alternative.
These refrigerants have excellent thermodynamic properties but are
flammable and thus unsafe. They have been used in place of CFCs in some
industrial applications and air conditioning systems. R170 ethane, R290
propane, R600 isobutane, R1150 ethylene
Inorganic refrigerants:- these are non hydrocarbon refrigerants
mostly naturally available. They were used before the advent of HC
refrigerants and are still in use. They are being looked upon as an
environment friendly refrigerants for the future

14. Following are the inorganic refrigerant like ammonia, water, air, CO2 and SO2
R717:- Ammonia is the oldest refrigerant used in vapor absorption system
and in application such as ice plant as the primary refrigerant. It is colorless
gas with a pungent odour used in leak detection. It is highly corrosive to
copper and is toxic to humans. Its boiling point is -33.3 and latent heat of
vaporization is 1315 KJ/Kg. It is lighter than oil and can easily be separated.
Used in cold storage plant for ice-cream etc.
R718:- Water essentially is used as ice to cool down hot bodies. The freezing
temperature of water limits its use in vapor compression refrigeration . It is
used as a solvent in vapor absorption system and also in steam jet refrigeration
R729:- Air is a mixture of gases and is treated as an ideal gas. It is safe non
toxic and used as a gaseous refrigerant in air craft air conditioning

15. R 744:- Carbon di oxide is a non toxic non flammable refrigerant. It is used as
a dry ice in solidified form. The boiling point is -73.6 degree Celsius. Due to
its high operating pressure size of compressor is small. It is used in some
industrial applications and in marine application.
R764:- Sulphur di oxide is produced by combustion of Sulphur in air. It is toxic
but non flammable. Its boiling point is -10 degree Celsius at atmospheric
pressure. In earlier time it was used in domestic refrigerator units. It is
chemically stable and immiscible with oil. The condensing pressure varies
between 4.1 bar to 6.2 bar under normal operating conditions. This refrigerant
is not injurious to food and is used commercially as a ripener and perseverative
of food, but extremely injurious to flowers, plants and strawberry. This is in its
pure state not corrosive but when there is moisture present, the mixture forms
sulphurous acid which is corrosive to steel

16. Properties of refrigerant
Thermodynamic properties
1. Critical temperature and pressure:- The critical temperature is the highest temperature at
which it can be condensed. It should be above condensing temperature of application. A
high condensing temperature is not desirable as high power consumption takes place. The
critical pressure is the extreme pressure at which refrigerant can be condensed.

17. Boiling temperature:- It is the temperature at which the phenomenon
of boiling formation of bubble with phase change occurs. It should be
low as possible to reduce the capacity of compressor and overall cost
of the system

18. Freezing temperature:- it is the temperature at which refrigerant loses
its fluidity due to low temperature freezing effect. The freezing
temperature should be below the evaporator temperature to prevent
the refrigerant from freezing during operation

19. Evaporator and condenser pressure:- Both evaporator and condenser pressure should be
slightly above the atmospheric level. The positive pressures are required to prevent
leakage of air and moisture into the refrigeration system. It also helps in detecting
refrigerant leaks. Too high evaporator and condenser pressure results in the requirement
of high strength compressor and condenser and thus increases capital cost

20. Compression ratio:- it should be as small as possible otherwise leakage of refrigerant
occurs across the piston. Also compression ratio affects the volumetric efficiency.
R11- 6.24, R12- 4.08, R22- 4.05, R40- 4.47, R113- 11.72, R717- 6.59
Latent heat of evaporation:- a refrigerant should have high latent heat of evaporation
at the evaporator temperature. Higher latent heat increases amount of heat removed
per unit mass of refrigerant i.e. refrigerant effect. This in turn reduces the mass of
refrigerant required to be circulated.
Specific heat:- It should be as small as possible. This reduces losses during throttling
of refrigerant and improves COP
Specific volume:- specific volume of refrigerant vapor at evaporator temperature
indicate theoretical displacement of the compressor. Refrigerant with low specific
volumes use reciprocating compressor and with high specific volume use rotary
compressor. Thus compressor type and capacity are indicated by specific volume of
the refrigerant vapor

22. COP and power consumption:- for an ideal refrigerant COP should
approach Carnot COP and power consumption should be minimum

23. Chemical properties
Chemical stability and inertness:- Refrigerants should be chemically stable and at the
same time, non reactive to pipe material. It should not undergo any chemical reaction
such as polymerization, disintegration or form corrosive compounds. Refrigerants like
ammonia react with material like copper. Hence non corrosive material such as stainless
steel must be used for piping. Thus refrigerants with high chemical stability and low
reactivity are desirable.
Flammability:- of a refrigerant is its amenability to catch fire. It should be as low as
possible. Hydrocarbon refrigerants have high flammability, which is not desirable. Use of
flame retardants can reduce flammability.
Toxicity:- it is a measure of harmful nature of refrigerant. It should be as low as possible
generally freons are the safest refrigerants with least toxicity

24. Miscibility:- the ability of refrigerant to mix with oil is called miscibility. The degree
of miscibility depends upon the temperature of the oil and pressure of refrigerating
vapor, the freon group are highly miscible while ammonia, carbon dioxide, Sulphur di
oxide, methyl chloride are non miscible. The miscible refrigerants are advantageous
from the heat transfer point of view, they give better lubrication as the refrigerant acts
as a carrier of oil to the moving parts.
Solubility of water:- water is able to dissolve in refrigerants like R11, R12 and R22.
This is undesirable as ice will be formed during operation, choking the expansion
valve or capillary tube used for throttling the refrigerant. Also, contaminants may
enter the refrigerant system through water.
Effects on commodity to be refrigerated:- Perishables like milk, fruits, vegetables
or flowers can be affected by the leakage of certain refrigerants like ammonia. Such
refrigerants are not desirable for preserving perishable commodities

25. Physical properties of refrigerants
Corrosive properties:- it is the ability to corrode metal. Freon group are non corrosive.
Ammonia is a corrosive refrigerant. Corrosion resistant materials are required to prevent
corrosion of valve and pipes .
Viscosity:- should have low viscosity. This reduces the pressure drop of refrigerant when
passing through a liquid and suction lines. Also heat transfer characteristics are better at
lower viscosities.
Thermal conductivity:- the refrigerant in liquid and vapor state should have high thermal
conductivity. Higher the thermal conductivity better the refrigerating effect.
Leakage tendency:- should be low. If there is leakage it should be easily detectable.
Fluorocarbon refrigerant leakage is hard to detect due to lach of odour, whereas leakage of
ammonia is easily detected due to its odour.
Dielectric strength:- the dielectric strength of refrigerant is its ability to resist electrical
charge. This ability is useful in hermetically sealed units, in which electric motor is exposed
to the refrigerant.
Cost and availability

26. Secondary refrigerants:- refrigerant which does not undergo cyclic
process but is used only as a medium for cooling. There are many
applications which forbid the direct use of refrigerant due to safety
concerns. There are applications such as air conditioning of school,
where one cannot use toxic refrigerants. Also in such applications,
refrigerant quantity is very high and cost of refrigerant is even higher
than refrigeration system, thus in such application such as cold
storage it is desirable to use secondary refrigerants like, brine
Advantages are reduce overall cost, improve safety of the
system by avoiding direct contact with primary refrigerant,
size of equipment is reduced and lesser grade materials can
be used for piping and heat exchangers. Some of the
examples are Ammonium chloride, Calcium chloride, Sodium
chloride, Methyl alcohol, Glycerin, Ethylene glycol, sodium
sulphate

27. Brines are secondary refrigerants and are generally used where temperatures are
required to be maintained below the freezing point of water i.e.0 degree Celsius. In case
of temperature involved is above the freezing point of water, then water is commonly
used as a secondary refrigerant.
Brine is a solution of salt in water. It may be noted that when salt is mixed in water, then
the freezing temperature of the solution becomes lower than that of water, due to fact
that the salt while dissolving in water takes off its latent heat from the solution and cools
it below the freezing point of water. as the concentration of the solution increases
freezing point decreases, but if concentration beyond a certain point increases
freezing point increases. Therefore the point at which freezing temperature is
minimum is known as eutectic temperature and concentration is known as eutectic
concentration.
The other water soluble compounds are known as antifreeze are also used for decreasing
the freezing point of water for certain applications, Ethylene and propylene glycol have a
number of good properties, since they are non corrosive in presence of water are most
extensively used as antifreeze elements

29. Environmental effects of refrigerants and need for alternatives
The earth is covered by a layers of ozone known as ozonosphere. It helps
to protect the earth from harmful ultraviolet radiations from the sun.
however, in recent times, it has been observed that there is a hole
created in the ozone layer. This hole in the ozone layer is attributed to
destruction of ozone by CFCs released in the atmosphere. The chlorine
in the CFCs is responsible for chemical reaction with ozone, causing its
destruction in presence of sunlight. It is a chain reaction and self
propagating.
One molecule of CFC can destroy hundreds of ozone molecules.
At the same time, due to release of gases, like carbon dioxide, into the
atmosphere, the temperature of the earths surface is rising due to
greenhouse effects. This is known as global warming. This is affecting
climatic patterns and disturbing life on the planet.
Thus refrigerants affect the environment in two ways 1. Ozone depletion
2. Global warming.