HVAC_Refrigerant.ppt

Sanjivani Rural Education Society’s
Sanjivani College of Engineering, Kopargaon-423 603
(An Autonomous Institute, Affiliated to Savitribai Phule Pune University, Pune)
NAAC ‘A’ Grade Accredited, ISO 9001:2015 Certified
Department of Mechanical Engineering
Subject:- Heating, Ventilation and Air
Conditioning (ME 402)
B.Tech.Mechanical
UNIT 1 :- Refrigerants
Purushottam W. Ingle
Assistant Professor

1
• Refrigerant: - Survey of Refrigerants, types of refrigerant, Designation
of Refrigerants, Thermodynamic, Chemical, Physical, properties of
refrigerant. Secondary Refrigerants, Ozone depletion, Global
warming, greenhouse effect, Environment friendly refrigerant R134a,
R410a, R600a, R290, R32. (Theoretical only)
• 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.
P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
9/4/2023

• The thermodynamic efficiency of a refrigeration system
depends mainly on its operating temperatures. However,
important practical issues such as the system design, size,
initial and operating costs, safety, reliability, and serviceability
etc. depend very much on the type of refrigerant selected for a
given application.
• Due to several environmental issues such as ozone layer
depletion and global warming and their relation to the various
refrigerants used, the selection of suitable refrigerant has
become one of the most important issues in recent times.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

• Replacement of an existing refrigerant by a completely new
refrigerant, for whatever reason, is an expensive proposition as
it may call for several changes in the design and manufacturing
of refrigeration systems.
• Hence it is very important to understand the issues related to
the selection and use of refrigerants. In principle, any fluid can
be used as a refrigerant.
• Air used in an air cycle refrigeration system can also be
considered as a refrigerant. However, here the attention is
mainly focused on those fluids that can be used as refrigerants
in vapour compression refrigeration systems only.

Designation of refrigerants:
• Since a large number of refrigerants have been developed over
the years for a wide variety of applications, a numbering system
has been adopted to designate various refrigerants.
• From the number , one can get some useful information about
the type of refrigerant, its chemical composition, molecular
weight etc.
• All the refrigerants are designated by R followed by a unique
number.

• 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)
• 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 refrigerants such as bromine derivative of HC are in
use.
• 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.

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
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. ...
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.
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.

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.

• 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.

Types of Refrigerant
• 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
• 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
• 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

• Mixtures: Azeotropic mixtures are designated by 500 series,
where as zeotropic refrigerants (e.g. non-azeotropic mixtures)
are designated by 400 series.
• Azeotropic mixtures:
• R 500: Mixture of R 12 (73.8 %) and R 152a (26.2%)
• R 502: Mixture of R 22 (48.8 %) and R 115 (51.2%)
• R503: Mixture of R 23 (40.1 %) and R 13 (59.9%)
• R507A: Mixture of R 125 (50%) and R 143a (50%)

• Zeotropic mixtures:
• R404A : Mixture of R 125 (44%), R 143a (52%) and R 134a
(4%)
• R407A : Mixture of R 32 (20%), R 125 (40%) and R 134a (40%)
• R407B : Mixture of R 32 (10%), R 125 (70%) and R 134a (20%)
• R410A : Mixture of R 32 (50%) and R 125 (50%)

• 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

• 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

• Inorganic refrigerants: These are designated by number 7
followed by the molecular weight of the refrigerant (rounded-
off).
• Ex.: Ammonia: Molecular weight is 17, ∴ the designation is R
717
• Carbon dioxide: Molecular weight is 44, ∴ the designation is R
744
• Water: Molecular weight is 18, ∴ the designation is R 718

• 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

• 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

Properties of refrigerant
• Thermodynamic properties
• 1. Critical temperature and pressure:- It is the temperature above which there will
not be any phase change. The critical temperature of the refrigerant should be well
above the condensing temperature for easy condensation of vapour.The critical
pressure is the extreme pressure at which refrigerant can be condensed.

Boiling temperature:- The refrigerants should have low boiling point
temperature at atmospheric pressure. During operation, low temperature can
be achieved with positive pressure of the refrigerant in evaporator coil. If the
pressure inside the evaporator coil is less than the atmospheric pressure,
then moisture may enter into the system through leakages.

• Freezing temperature:- The freezing temperature should be below the
evaporator temperature to prevent the refrigerant from freezing during
operation.

• 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.

• Evaporating pressure should be just above the atmospheric pressure.
If too low, it would result in a large volume of suction vapour. If high,
the condenser pressure and the overall pressure will be greater.
• A positive evaporator pressure is required in order to eliminate the
possibility of the entry of air and moisture into the system.
• The normal boiling point of the refrigerant should be lower than the
refrigeration temperature. A small difference between suction
pressure and discharge pressure or a low pressure ratio (the ratio of
condenser pressure to evaporator pressure) is desirable for good
efficiency.

• Condensing pressure
• It depends on the temperature of the condenser cooling medium
which is usually water or atmospheric air.
• A refrigerant should have low condensing pressure to avoid robust
constructions and to reduce the tendency of leakages.

• 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.

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

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

• 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

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 lack 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

• 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

• 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

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.

Ozone Depletion
• There is a layer of ozone
(O3) gas in stratosphere up
to 50 km from the earth's
surface (see Figure ). The
ozone layer filters the
ultraviolet radiations from
sun entering the earth
atmosphere and allows
only the beneficial heat
and light rays to reach the
earth's surface.

• Therefore, the ozone layer protects us against the harmful effects of
such radiations like skin cancer.
• 1. Ozone is a form of oxygen. Each ozone molecule is made of three
oxygen atoms.
• 2. Ozone, unlike oxygen, is poisonous and an increase in its
concentration at ground level is not desirable.
• 3. In the stratosphere, ozone occurs naturally and blocks out the sun's
UV-B rays, so ozone is a life-saver. Some of the gases including CFC
given out by different processes on earth reach this layer and react
with ozone gas to form different compounds. This causes the
depletion of ozone at particular places which are called ozone holes.

Formation and destruction of ozone
• The major reasons for ozone depletion are chlorine and bromine. The chemical
reactions during the formation and destruction of ozone are consolidated here in
a stepwise manner.

• Ozone depletion potential ( ODP)
• ODP is the ratio of the impact of a chemical compared to the impact
of a similar mass of CFC-11. Thus, ODP of CFC is 1.0.
• ODPs of other CFCs and HCFCs fall in the range of 0.01 to 1.0.
• The ODP of carbon tetrachloride is 1.2.
• HFCs have zero ODP as they do not contain chlorine.

• Ozone depletion potential (ODP) and Global Warming Potential (GWP)
are the indexes of how damaging a refrigerant is to the environment

• It can be clearly seen that the refrigerant like R123 which have low
ODP and GWP are desirable
a need is now felt to develop alternative refrigerants to replace freons.
They should be environment friendly and effective as well. There are
three type of refrigerant which are being considered as suitable
refrigerants like natural refrigerants i.e. air water and ammonia,
hydrocarbons and synthetic refrigerants.

• Ozone Depletion potential:- it is defined as the capacity of a
compound to destroy ozone molecules in the atmosphere, as compared
to R11.Usually CFCs have the highest ODP and natural refrigerants
have the lowest ODP. ODP depends on the chemical composition of
the refrigerant. This is because certain elements like chlorine reacts
with ozone and destroy it. Thus refrigerants containing chlorine are
the high destructors of ozone and have high ODP. Lower the ODP,
better the refrigerant.

• Global warming Potential (GWP):- It is defined as the capacity of
refrigerant to increase the temperature of atmosphere similar to
greenhouse gas like CO2. The GWP of green house gas is defined as
the ratio of time integrated temperature increases from the
instantaneous release of 1 kg trace substances relative to that of 1 kg
of reference gas. Lesser the value of GWP better is the refrigerant.

• New refrigerants like R134a which replaces R12, and R123 which
replaces R11 are already commercially available. A comparison of the
properties of these refrigerants is given in table.

• As expected, R134a, which contains no chlorine, is readily compatible with
sealing materials.
• R134a is almost completely immiscible with conventional mineral oil-based
refrigeration oils and also with a number of synthetic lubricants such as
alkylbenzenes. The synthetic compound oils are found miscible with R134a and
others include polyalkylene glycols (PAGs).
• R134a does not form flammable mixtures with air under normal conditions, i.e.
atmospheric pressure. Flammable mixtures would form at pressures above
atmospheric if the air components in the mixture exceed 60%.
• In leakage checks or pressure tests these refrigerants must never be used
together with air or oxygen. R134a is also safe toxicologically like Rl2. The results
indicate that the product can be used safely in domestic, commercial and
industrial refrigeration.

OIL AND REFRIGERANT RELATIONSHIP
• The oil required for lubrication of the compressor is
contained in the crankcase of the compressor where it
comes in contact with the refrigerant.
• Therefore, the refrigerant must be chemically and physically
stable with oil at the operating conditions.
• When contaminants such as air and moisture are present in
the system in an appreciable amount, chemical reactions
often take place between these contaminants, oil and
refrigerant, resulting into the decomposition of oil.

• A high discharge temperature greatly accelerates the decomposition
of oil and formation of carbonaceous deposits on discharge valves,
pistons and in the compressor head and discharge line.
• This condition is aggravated by the use of poorly refined lubricating
oils containing a high percentage of unsaturated hydrocarbons, the
latter being very unstable chemically.
• With all this information, one can say that use the oil recommended
by the manufacturer of the compressor, never mix two oils with
different characteristics. Further, make sure that the oil stays in the
compressor.

• Oil causes problems in heat exchangers, where the oil film decreases
the value of heat transfer coefficient. In refrigerant liquid pumps, it
creates cavitation and in automatic controls it acts as a lubricant.
• Oil miscibility (ability of the refrigerant to be dissolved into the oil and
vice versa) is one, which characterizes the refrigerant oil relationship.
As per miscibility, refrigerants may be divided into three groups:
• 1. Miscible
• 2. Immiscible
• 3. Partially miscible.

• Refrigerants such as R134a, R123 and R11, are miscible with oil in all
proportions under all conditions and do not pose problems.
• Oil that reaches the evaporator is returned to the compressor along
with the refrigerant.
• Any oil droplets separated may also be returned to the compressor by
gravity or by the high velocity return gas.
• The diameter of the suction tube is so designed that the velocity of
the returning gas is sufficient enough to carry away the oil sticking to
the walls of the tube.

• The refrigerant such as ammonia, which is not miscible with oil at all,
also does not pose any problems.
• In such a case, an oil separator is installed in the discharge line but
nearer to the compressor and the separated oil is continuously
returned to the crankcase of the compressor.
• The refrigerants, which are miscible under conditions normally found
in the condensers, but remain separate from oil normally found in the
evaporator are called partially miscible refrigerants and they may
pose some problems.

• Montreal Protocol:- This protocol was established to phase out the
consumption and production of ozone depleting substances within a
specified timeframe. The timeframe for both developed and
developing countries is to be reviewed from time to time. The
protocol was signed in Montreal on 16 September 1987 under
auspices of UN Environment Programme.
• It is still rated as the most successful international agreement on a
technical issue. The original schedule contained 50% reduction in
emission of CFCs by developed countries with a 10 year grace period
for the developing countries. The protocol was modified in Vienna ad
ozone depleting refrigerants were added in 1997.

• The current provisions are as follows:
total phase out of CFCs in developed countries by 1.1.1996 A
grace period of 10 years for developing countries to gradually
reduce and phase out CFCs. Complete phase out of HCFCS by
year 2020 in developed countries and 2030 for developing
countries. The Montreal Protocol does not address the non ozone
depleting refrigerant . India which qualified as a developing
country, is required to ban CFCs at the end of this decade.

• Kyoto Protocol:- This protocol was adopted at the third conference of parties on
the framework convention of the global climate change in Kyoto in 1997. the
protocol has put HFC together with five gases contributing to global warming,
namely CO2, N2O, CH4, SF6 and PFCs. Kyoto Protocol does not address CFC
and HCFC as they are covered under Montreal Protocol.
• The Kyoto Protocol aims at reduction and control of Greenhouse gas emissions.
The developed countries have obligation to cut down on their emission by 5.2 %
below 1990 levels. Kyoto Protocol has not been ratified by all countries. The
Protocol comprises three parts: Clean development mechanism, emission trading,
Joint implementation. Developing countries have no obligation to cut emission
under the protocol and thus the protocol is considered biased by the developed
countries

• Total Equivalent Warming Potential:- TEWI is evaluations
emphasize the combined environmental effect of the direct
emissions of greenhouse gases with indirect effects of C02
emissions from energy use by equipment using refrigerants.
Thus TEWI is a coupled index. It is defined as sum of amount
of refrigerants released into the atmosphere and amount of
CO2 released during energy generation used to drive
refrigeration and air conditioning equipment Thus it is an
index of global warming

Alternatives to CFCs
• CFCs are to be phased out by the Montreal Protocol due to their
environmental impact. Several alternative refrigerant have been selected to
replace them.

HVAC_Refrigerant.ppt

Recommended

Recommended

More Related Content

Similar to HVAC_Refrigerant.ppt

Similar to HVAC_Refrigerant.ppt (20)

More from Purushottam Ingle

More from Purushottam Ingle (20)

Recently uploaded

Recently uploaded (20)

HVAC_Refrigerant.ppt