Futuristic working fluids for Refrigeration and Air conditioning

International Journal of Latest Trends in Engineering and Technology (IJLTET)
Futuristic working fluids for Refrigeration and
Air conditioning Systems - A Review and
Outlook
P. Elumalai
Assistant Professor, Department of Mechanical Engineering
Paavai Engineering College, Namakkal, Tamilnadu, India.
R..Vijayan
Professor, Department of Mechanical Engineering
Government College of Engineering, Salem, Tamilnadu, India.
M. Premkumar
Professor, Department of Mechanical Engineering
Paavai Engineering College, Namakkal, Tamilnadu, India.
Abstract: A refrigerant is a working fluid used in a heat cycle for enhancing energy efficiency, by a reversible phase
conversion from a liquid to a vapor. It comprises the main property of vapor to liquid and liquid to vapor. Coventionally,
fluorocarbons, especially chlorofluorocarbons were used as refrigerants, but they are being forbidden because of their
effects on ozone depletion. In this paper, a review of available alternative refrigerants and their physical, chemical
properties vast literature survey have been carried out. Selection of efficient, eco-friendly and safe refrigerant for future
has been attempted in this paper through discussions.
Keywords – Refrigeration, Refrigerants, Global warming, zero Ozone Depleting Potential, Air conditioning
I. INTRODUCTION
Refrigerants have been extensively used in several areas in the industry for a long time. After finding the harmful
effects of CFC based refrigerants on the ozone layer, the search to find alternatives to these working fluids gained
more interest in the recent few years. Finding drop-in replacements for Chlorofluorocarbons based working fluids is
important due to their harmful effects on the ozone layer and international conventions are requesting to reduce their
usage.
B.O. Baoji et al [1] experimentally investigated the performances of three ozone friendly Hydro fluorocarbon (HFC)
refrigerants R12, R152a and R134a. R152a refrigerant found as a drop in replacement for R134a in compression
system. the process of selecting environmental-friendly refrigerants that have zero ozone depletion potential and low
global warming potential. R23 and R32 from methane derivatives and R152a, R143a, R134a and R125 from ethane
derivatives are the emerging refrigerants which have non toxicity, low flammability and environmental-friendly. In
these refrigerants need theoretical and experimental analysis to calculate their performance in the system. S. Wong
wises et al [3,5] found that 6/4 mixture of R290 and R600 is the most refrigerant to replace HFC134a in a domestic
refrigerator. Bagola [4] investigated the exergy performance of R12 and its substitute (R134a and R 152a) in the
domestic refrigerator. R152a successes better than R134a in terms of COP and exegetic efficiency
Miguel Padilla et al [2] found that R413A (mixture of 88% R134a, 9%R218, 3%R600a) can replace R12 and R134a
in domestic refrigerator. Molina et al (1974) have been expanded into a comprehensive and very complex theory
emphasis about 200 reactions that CFCs are significantly destroyed by UV radiation in the stratosphere. In the year
1987 Hoffman predicted 3 % global ozone depletion with contact of CFCs emissions of 700 thousand tone /year [4,
5,].Studied the performance analysis of alternative new refrigerant mixtures as substitute for R12, R134a and R 22.
Refrigerant blend of R290/R 600a (40/60 by wt. %) and R 290/R1270 (20/80 by wt. %) are found to be the most
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447
ISSN: 2278-621X
International Journal of Latest Trends in Engineering and Technology (IJLTET)
suitable alternative among refrigerants tested for R12 and R22. Abishiek Tiwari et al [7] published a review paper
on recent development on domestic refrigeration. Alkali Bane Agrawal et al (10) worked on eco-friendly refrigerant
as a substitute for CFC (Chlorofluorocarbon). The binary mixture in the ration of 64% and 36% of R290 and R600a
found to be a retrofit or drop in substitute of R12 for use in the compression refrigeration trainer. A performance
comparison of vapor compression refrigeration system using various alternative refrigerants. A theoretical
performance study on a conventional compression refrigeration system with refrigerant mixtures based on
HFC134a, HFC152a, HFC32, HC290, HC1270, HC600, and HC600a was done for various ratios and their results
are compared with CFC12, CFC22, and HFC134a as useful alternative replacements [17]. The activities of HCFC
and HC-290 refrigerant mixture computationally as well as experimentally and found that refrigerant mixture 7/3 as
a promising alternative to R12 system. R. Cabello et al [16] studied the influence of the evaporating pressure,
condensing pressure and superheating degree of the on the performance of a refrigeration plant using three different
working fluids R134a, R407C, R22.
Fig.1 Vapor compression refrigeration cycle
Jacob Perkins, an American citizen, obtained a patent in 1834 on a compression refrigerating system using ethyl
ether in a closed circuit. The patent covers all the elements of the modern compression system, the compressor, the
condenser, the expansion valve and the evaporator. From this time there began a search for the ideal refrigerant,
which has not yet been, and which perhaps never will be discovered. Perkins used ethyl ether, in his early
experiments but later graduated to an organic material produced by the heating of Indian rubber. Ethyl ether is not a
good refrigerant because it is both anesthetic and flammable as well as requiring a large swept volume per unit of
refrigerating effect. Ethyl ether is denser than air and has no strong smell, thus making it particularly dangerous in
an age when illumination was by lamp or candle. It is not comprehensible what components were contained in
Perkins’ quintessence from India rubber, but all who came in contact with it, which has been reported that it had an
ineffably bad adore.
II. HISTORY
The traditional refrigerants like ammonia, SO2 and CO2 had been secluded and they were available for use, but
complex compressors and prime movers were required to use them and for a while, the original refrigerants, air and
water, competed with the water/ammonia absorption machine in the production of artificial cold. None of these
refrigerants can fight with the compression system in terms of efficiency. Air, which is used in the Brayton cycle,
produces a very low thermodynamic efficiency because of the large temperature range through which the cycle.
Water is difficult to use efficiently because of the very low pressure and enormous pumped volumes which are
involved. Absorption systems are notoriously inefficient but require a minimum of high-grade energy. However, it is
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ISSN: 2278-621X
International Journal of Latest Trends in Engineering and Technology (IJLTET)
impossible to imagine more compassionate substances than air or water. Ammonia, being part of the natural
nitrogen cycle, is also completely benevolent in environmental terms. Compression refrigeration continued to use
the highly flammable ethyl ether, though in 1863 Charles Teller took out a patent on the use of methyl ether, which
operated at higher pressure and thus reduced the risk of drawing air into the system and forming an explosive
mixture within the machine. Compression systems were improved by James Harrison in Australia but continued to
use methyl ether, which was also used by Carl von Linden in 1875.
Linden is generally considered to have pioneered the use of ammonia, but the first ammonia compressor for
refrigerating purposes was designed and constructed by David Boyle in 1872, 4 years before the first Linden
ammonia machine. Boyle produced up to 200 ammonia compressors prior to 1884, mostly for the shipping of beef
from Texas. Ammonia is in many respects the ideal refrigerant but it has always had competition from less toxic
substances. As early as 1862, Thaddeus Lowe developed a carbon-dioxide refrigerating system using a compressor
he had developed for compressing hydrogen for observation balloons during the Civil War. Carbon dioxide has very
low toxicity but requires high-pressure machinery and is difficult to use because of its low critical temperature
(31.6 o C). Before the end of the 19th century, a fourth practical refrigerant, methyl chloride, had appeared in
France, being used for the first time as a refrigerant in 1878. Methyl chloride was the forerunner of the wide range of
halocarbon refrigerants, which came to prominence later. However, methyl chloride is odorless, but both are
flammable and toxic, which gave the several serious accidents. In practice, methyl chloride proved to be much more
dangerous to use than either SO2 or ammonia. SO2 is highly toxic but has a strong smell, which provided warning of
any leak. Ammonia is also highly toxic and can be smelled at even lower concentrations than SO2.
III. PRESENT REFRIGERANTS
All HFCs, HFOs and HCFCs refrigerants brings us to the present day. The only single-component HFC in
common use as a refrigerant is R-134a, which is a good match for R-12. Replacements for R-22 and R-502 have
been creating by blending components to produce the required properties. In general, blends of volatile substances
will evaporate to dryness through a temperature range known as ‘‘glide’’. Some blends however evaporate at a
constant temperature; these blends are known as zoetrope. Glide is considered to be inconvenient so blends are
generally selected to have zero, or minimal, glide. Such blends are zoetrope or near-zoetrope. Zoetrope are given
refrigerant numbers in the 500 range. The actual numbers have no significance beyond indicating the order in which
the blends were accepted by ASHRAE.
Current requirements for a successful blend are that it should have an Ozone Depleting Potential (ODP) of
zero, that it should be efficient to use in conventional refrigeration machinery, which should be non-toxic, nonflammable, and that it should have low global warming potential (GWP). It is very difficult to meet all these
requirements. The only methane derivative which comes anywhere near is R-23, and it has a very high GWP. The
only acceptable ethane derivatives are R-134a and R-125. It becomes observable that flammable substances have to
be pressed into service, provided they can be included in blends which are non-flammable and do not fractionate to
flammable. The flammable substances R-32, R-161, R-152a and R-143a can be added to the list of possible blend
components. This still provides only seven substances from which to permutated halocarbon refrigerants for today
and for tomorrow. Attention turns to derivate of propane but, out of 45 such compounds, only R-227, R-236 and R245 are apparently suitable. None of these substances has a normal boiling point which makes it very suitable for
commercial refrigeration. Another problem which arises when considering substances which are derivatives of
propane, butane, or even heavier hydrocarbons, is that the critical temperature, and therefore the latent heat, of such
substances tends to decrease as the molecular weight increases. It is a serious disadvantage for a refrigerant to have a
low critical temperature and a low latent heat. A major disadvantage of all the HFC refrigerants is that they have
relatively high GWPs compared to the natural refrigerants.
IV. ALTERNATIVE REFRIGERANTS
A.CO2 CO2 is substance that it has virtually no impact on global warming or ozone depletion. CO2 is also nontoxic
in small doses but concentrations over 5% can be lethal. It is also cheap and nonflammable, but when used as a
refrigerant, CO2 (which is called R-744) requires extremely high operating pressures compared to R-134a.
B. HFC-152a -
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International Journal of Latest Trends in Engineering and Technology (IJLTET)
HFC-152a is almost a straight drop-in replacement for R134a. The molecule is similar to R-134a except
that two hydrogen atoms are substituted for two fluorine atoms. It has similar operating characteristics to R-134a but
cools even better. An environmental benefit of HFC-152a is a working fluid which has a global warming rating of
120, which is 10 times less than R-134a, but still a lot higher than CO2. That is why HFC-152a is currently used in
many aerosol products as a propellant. Its main drawback is that it is slightly flammable.
C.HFO-1234yf Another new refrigerant which is being considered is HFO1234yf and developed jointly by Honeywell and
DuPont; it is being promoted as a possible drop-in replacement for R134a in both new vehicles and older vehicles,
should that become necessary in the future. HFO-1234yf has thermal characteristics that are very close match to R134a, there is no major modifications to the A/C system. Better yet, HFO-1234yf has a global warming potential of
only 4, compared to 1200 for R-134a, allowing it to meet the European requirements for a GWP of less than 150.
D. Ammonia Ammonia is produced in a natural way by human beings and animals; 17 grams/day for humans. Its ODP
and GWP both are zero and posses excellent thermodynamic characteristics: small molecular mass, large latent
heat, large density and excellent heat transfer characteristics .Its smell causes leaks to be detected and fixed before
reaching dangerous concentration also available at relatively low price. The only drawback of NH3 is that it is toxic,
flammable and not compatible with copper.
E.134a R 134a is a HC-based refrigerant and which is a blend of environmentally harmless hydrocarbon fluids
designed as a direct replacement and retrofit with refrigerant option for replacing R123a and R12 refrigerants in
automotive air conditioning and refrigeration systems outside of the US.. Super-freeze 134a operates at lower head
pressures and offers improved cooling properties and performance.
V. APPLICATIONS OF REFRIGERANTS
F. Domestic refrigeration The vast majority of domestic refrigerators use R134a, which is a relatively close match for R-12.
Disadvantages of R-134a include relatively poor performance at low evaporating temperatures compared to R-12
and a requirement to use synthetic lubricants like Polyol ester. Hydrocarbons took over from R-134a for domestic
refrigerators in certain parts of the world. The most commonly used hydrocarbon is butane (R600) and isobutene
(R-600a) are, at first sight, a astonishing choice because of the large volumetric flow required but the high critical
temperature, 135 oC, and low cycle pressures combine to produce a very quiet and efficient system. The safety
testimony has been excellent.
G. Automotive air conditioning The dominant refrigerant for car air conditioning is R-134a. Emissions to atmosphere from this source are
causing concern.
H. Commercial refrigeration The dominant refrigerants in this field were R-22 and R-502. Zero ODP replacements for these substances
tend to be blends of several HFC refrigerants, including R-32, R-125, R-143a, R152a, R-134a, sometimes with the
addition of a hydrocarbon to improve transport of lubricant within the system. Replacement blends in the 400 and
500 series have performed relatively well in filling the gap left by R-22 and R-502 but serious concern is being
expressed about their high global warming potentials and their low critical temperatures. More efficient substitutes
are being sought but the availability of substances to replace the methane and ethane type HFCs is limited. They
have been some use of hydrocarbons in the commercial refrigeration industry but the practice is not widespread.
I. Air conditioning Air conditioning has come to be almost completely carried out using halocarbon refrigerants. R-134a is
used for small, fully sealed, systems and for centrifugal systems. R-404A and R-407C are the most commonly used
refrigerants for larger systems. R-404A has very little glide but operates at higher pressures than R-22 and has
lower theoretical efficiency at extreme pressure ratios.
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International Journal of Latest Trends in Engineering and Technology (IJLTET)
J. Industrial refrigeration Ammonia continued to be used in the more traditional sections of the industrial refrigeration industry,
though its use declined significantly with the advent of the non-toxic, non-flammable halocarbons. Two unrelated
events reversed the tendency away from ammonia. The first was the emergence of the oil-cooled screw compressor,
which overcomes the high discharge temperature problems which have to be countered when using reciprocating
compressors with ammonia. The second was the publication of their ozone depletion theory by Roland and Molina.
Use of ammonia has been increasing in recent years and the use of ammonia is extending back down into regions
which, in the past, would have been served by reciprocating compressors using halocarbon refrigerants.
K. Halocarbons Halocarbons are so convenient to use that a strong case can be made for their continuing use. However,
better methods of containment are essential and more efficient refrigerants with higher critical temperatures and
lower GWPs should be sought. It is clear that most losses of refrigerant come from "serviceable" systems, such as
car air conditioning, and from distributed and serviceable systems, such as supermarket installations. By contrast,
refrigerant loss from fully sealed, factory-constructed systems, such as domestic refrigerators and window air
conditioners, is much less. The charge of such systems is also small. As previously indicated, there are few possible
compounds available which are not halocarbons.SF6 would have some potential as a refrigerant but it has a very
high GWP of 22,200.HFE are theoretically possible but they too have high GWPs. E-125 (CHF2-O-CF3) has an
ideal boiling point of –42oC but is prohibitively expensive to produce and has a GWP of 15 300. I’ve long been an
advocate of the use of R-218 (C3F8) because it forms a zoetrope with a large number of halocarbons and therefore
allows the production of a wide variety of potentially efficient blends. The GWP of R-218 is 7000 but, as far as I am
aware, it has not been detected in the atmosphere despite being used in some industrial processes for many years.
Table 1. Currently used Zero ODP Refrigerants
Refrigerant
Formula
NBP0C
Glide K
T c (0C)
GWP
R-134a
R-413A
R-404A
R-507A
R-407C
R-417A
R-410A
R-508
R-717
R-600a
R-290
R-1270
CH2F.CF3
R- 134a.218/600a
R-143a/125/134a
R-143a/125
R-32/125/134a
R-125/134a/600
R-32/125
R-23/116
NH3
CH (CH3)3
C3H6
C3H6
-26
-35
-47
-47
-44
-43
-51
-86
-33
-12
-42
-48
0.0
6.9
0.7
0.0
7.4
5.6
0.2
0.0
0.0
0.0
0.0
0.0
101
101
73
72
87
90
72
13
133
135
97
92
1300
1900
3800
3900
1700
2200
2000
12000
0
20
20
20
Safety
Group
A1
A1/A2
A1/A1
A1
A1/A1
A1/A1
A1/A1
A1
B2
A3
A3
A3
Table 2. Possible Future Blend Components
Refrigerant
Formula
NBP (oC)
CT (o C)
ODP
GWP
R-23
R-32
R143a
R-161
R-218
R-134a
R-227ea
R-236fa
R-143
R-245fa
R125
CHF3
CH2F2
CH3.CF3
CH3.CHF2
C3F8
CH2F.CF3
CF3.CHF.CF3
CF3.CH2.CF3
CH2F.CHF2
CHF2.CHF.CHF2
CHF2.CF3
-81.2
-51.7
-47.2
-37.2
-36.6
-36.6
-15.6
-1.4
5.0
15.1
-48.1
25.9
78.2
72.9
102.2
71.9
101.1
102.8
124.9
156.6
154.1
66.2
0
0
0
0
0
0
0
0
0
0
0
12000
550
4300
12
8600
1300
3500
9400
300
950
3400
Vol. 5 Issue 2 March 2015
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ISSN: 2278-621X
International Journal of Latest Trends in Engineering and Technology (IJLTET)
V. CONCLUSION
People are at a time of transition in refrigeration. Such times are always interesting but some accasion
painful and dangerous. It is a time of challenge the changes of refrigerants .and opportunity for professional young
researchers. Ammonia, Hydrocarbons and Carbon dioxide that may lead to zero ODP and minimal GWP. For
making the refrigerant more efficient system need to have low TEWI factor. In the future, the development agents
will further develop more refrigerants which will not only be making the work system more efficient but also having
the eco-friendly nature, leading to the accomplishment of the refrigeration goals and enhancing the wellbeing and
safety of the worker.
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