The present invention relates to quaternary refrigerant compositions,
particularly for use as replacements in air conditioning and refrigeration equipment
currently employing, or designed to employ, chlorodifluoromethane (R22).
BACKGROUND OF THE INVENTION
Refrigerant is the substance which is used as working fluid in a
thermodynamic cycle, undergoes a phase change from liquid to vapour and produces
cooling. These are used in refrigeration, air conditioning, and heat pumping systems.
They absorb heat from one area, such as an air conditioned space, and reject it into
another, such as outdoors, usually through evaporation and condensation,
respectively. These phase changes occur both in absorption and mechanical vapour
compression refrigeration systems, but they do not occur in systems operating on a
gas cycle using a fluid such as air.
Before the discovery of ozone hole in early 1970s, the refrigeration and airconditioning industry was relying heavily on chlorofluorocarbons (CFCs),
hydrochlorofluorocarbons (HCFCs) and their azeotropes.
HCFC refrigerant namely chlorodifluoromethane (R22) is widely used for
residential and commercial air conditioning, as well as commercial refrigeration and
has been commonly used with a mineral oil lubricant. R22 is the subject of a phaseout schedule under the Montreal Protocol as its chlorine content make it the largest
ozone depleting substance in volumetric terms. R22 is prohibited from use in new
equipment in some countries. After the discovery of ozone hole, the era for
alternative refrigerants has started.
Refrigerant mixtures may be used as the alternative refrigerants. Refrigerant
mixtures/blends can be classified based on the number of pure components, that is,
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binary/ternary/quaternary. A number of patents have suggested quaternary
refrigerant compositions as replacements for R22.
U.S. Patent no. 6,526,764 discloses a refrigerant composition comprising
from about 80 to about 99. 9 weight percent of a hydrofluorocarbon refrigerant and
from about 20 to about 0.1 weight percent of a solubilizing agent selected from the
group consisting of butane, isobutane, pentane, dimethyl ether and mixtures thereof.
U.S. Patent no. 6,363,741 discloses a refrigerant composition comprising
from 20 to 30 weight percent, preferably 25 weight percent, of R-32
(difluoromethane), 10 to 20 weight percent, preferably 15 weight percent, of R-125
(pentafluoromethane), 40 to 60 weight percent, preferably 50 weight percent, of R134a (tetrafluoroethane), and 0.itive1 to 14 weight percent, preferably 10 weight
percent, of n-pentane.
U.S. Patent no. 9,765,250 discloses a non-azeotropic fluid mixture for air
conditioning devices, comprising a mixture of 0.5-5% 2-methylpropane (isobutane,
R-600a); 1-3% pentafluoroethane (R-125), 93-95% 1,1,1,2-tetrafluoroethane, (R134a), and 2-3% difluoromethane (R-32).
U.S. Patent no. 6,783,691 discloses a nonflammable, azeotrope-like
composition consisting essentially of from about 1 to about 19 weight percent
difluoromethane, from about 25 to about 60 weight percent pentafluoroethane, from
about 24 to about 60 weight percent 1,1,1,2-tetrafluoroethane and from about 0.5 to
about 5 weight percent of a hydrocarbon selected from the group consisting of: nbutane; isobutane; n-butane and 2-methylbutane; n-butane and n-pentane; isobutane
and 2-methylbutane; and isobutane and n-pentane.
U.S. Patent no. 7,837,894 discloses a nonflammable refrigerant composition
based on the weight of the composition consisting of pentafluoroethane in an amount
of 83-90%; 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane or a mixture thereof
in an amount of 7.5-15% by weight based on the weight of the composition; and
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isobutane in an amount of from 1-4% by weight based on the weight of the
composition.
U.S. Patent Appl. Pub. no. 2004/0061091 discloses a refrigerant composition
comprising 45-50 weight percent R-134a, 45-50 weight percent R-125, 3-5 weight
percent R-32, and 1-4 weight percent of the hydrocarbon component, the
hydrocarbon component comprising one or more hydrocarbons selected from Group
A and one or more hydrocarbons selected from Group B, wherein the Group A
hydrocarbon comprises R-290 and the Group B hydrocarbon comprises R-600a.
The above compositions have significant amount of R125 which contributes
to the higher GWP of these compositions and defeats the purpose of using them as
replacement for R22. There is an urgent need to develop nonflammable refrigerant
compositions with lower GWP that can replace R22 and are compatible with the
systems already in use for R22.
The present invention discloses quaternary refrigerant compositions as
replacement for R22 comprising non chlorine containing refrigerants having low
GWP and no deleterious effect on ozone layer.
OBJECT OF THE INVENTION
The object of the present invention is to provide a refrigerant composition
having low GWP that can be used as a drop-in replacement for R22.
SUMMARY OF THE INVENTION
A first aspect of the present invention provides a refrigerant composition
comprising about 15% to 30% by weight of R32; about 0.1% to 10% by weight of
R125; about 60% to 75% by weight of R134a and about 0.1% to 15% by weight of
R600a as a drop-in replacement for R22.
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A second aspect of the present invention provides a refrigerant composition
comprising about 15% to 30% by weight of R32; about 0.1% to 10% by weight of
R125; about 60% to 75% by weight of R134a and about 0.1% to 5% by weight of
R600a as a drop-in replacement for R22.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, the term about refers to 10% variation from the specified
parameter.
As used herein, a refrigerant is defined as a heat transfer fluid that undergoes
a phase change from liquid to gas and back again during a cycle used to transfer of
heat.
The refrigerant compositions of the present invention are enlisted in Table 1.
Table 1
Compositions R32* R134a* R125* R600a*
Composition 1 25 65 4 6
Composition 2 16 72 4 8
Composition 3 20 70 4 6
Composition 4 22 68 4 6
Composition 5 22 72.4 5 0.6
Composition 6 23 72.2 4 0.8
Comparative
Composition
2.5 93.5 1.5 2.5
*all quantities are calculated as % by weight
Drop-in refrigerant is a refrigerant which can replace the other refrigerant
without any change in the existing system.
As used herein, non-absorbable gases are the gases which cannot be
compressed predominately include air.
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Non-azeotropic composition is a mixture of two or more substances that
behaves as a simple mixture rather than a single substance. One way to characterize
a non-azeotropic composition is that the vapor produced by partial evaporation or
distillation of the liquid has a substantially different composition as the liquid from
which it was evaporated or distilled, that is, the admixture distills/refluxes with
substantial composition change.
The quaternary blend composition has lower molecular weight thus has large
enthalpy of evaporation. The comparative data for enthalpy of evaporation is given
below:
Refrigerant Temperature Liquid
Phase (°C)
Liquid Phase Molar
Mass (kg/kmol)
Vapour phase
Enthalpy (Kj/Kg)
R-22 25 86.468 413.03
Composition 1 25 79.735 452.3
Composition 2 25 84.447 441.85
Composition 3 25 81.439 449.96
Composition 4 25 81.573 448.90
Composition 5 25 84.428 432.89
Composition 6 25 83.555 434.64
R-22 -25 86.468 394.9
Composition 1 -25 79.735 439.46
Composition 2 -25 84.447 426.06
Composition 3 -25 81.439 436.83
Composition 4 -25 81.573 435.36
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Composition 5 -25 84.428 407.61
Composition 6 -25 83.555 409.46
The refrigeration capacity is a measure of the ability of a refrigerant or heat
transfer composition to produce cooling. Therefore, the higher the capacity, the
greater the cooling that is produced. Cooling rate refers to the heat removed by the
refrigerant in the evaporator per unit time.
Coefficient of performance (COP) is the amount of heat removed divided by
the required energy input to operate the cycle. The higher the COP, the higher is the
energy efficiency. COP is directly related to the energy efficiency ratio (EER) that is
the efficiency rating for refrigeration or air conditioning equipment at a specific set
of internal and external temperatures.
The quaternary blend composition of the present invention has higher latent
heat of vaporization which helps to achieve higher COP.
Discharge temperature is a temperature of the refrigerant gas at the discharge
of the compression.
Flammability is a term used to mean the ability of a composition to ignite
and/or propagate a flame. Determination of whether a refrigerant compound or
mixture is flammable or non-flammable can be done by testing under the conditions
of ASTM-681.
Global warming potential (GWP) is an index for estimating relative global
warming contribution due to atmospheric emission of a kilogram of a particular
greenhouse gas compared to emission of a kilogram of carbon dioxide. GWP can be
calculated for different time horizons showing the effect of atmospheric lifetime for
a given gas. The GWP for the 100-year time horizon is commonly the value
referenced. For mixtures, a weighted average can be calculated based on the
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individual GWPs for each component. The standard GWP values for R22, 32, 125
and 134a has been taken from IIPCC 5th Assessment report 2014 (AR5). The GWP
of the refrigerant mixture has been derived from mass fraction and the corresponding
GWP values.
Ozone depletion potential (ODP) is a number that refers to the amount of
ozone depletion caused by a substance. The ODP is the ratio of the impact on ozone
of a chemical compared to the impact of a similar mass of CFC-11
(fluorotrichloromethane). Thus, the ODP of CFC-11 is defined to be 1.0. Other CFCs
and HCFCs have ODPs that range from 0.01 to 1.0. HFCs have zero ODP because
they do not contain chlorine or other ozone depleting halogens.
A first aspect of the present invention provides a refrigerant composition
comprising about 15% to 30% by weight of R32; about 0.1% to 10% by weight of
R125; about 60% to 75% by weight of R134a and about 0.1% to 15% by weight of
R600a as a drop-in replacement for R22.
A second aspect of the present invention provides a refrigerant composition
comprising about 15% to 30% by weight of R32; about 0.1% to 10% by weight of
R125; about 60% to 75% by weight of R134a and about 0.1% to 5% by weight of
R600a as a drop-in replacement for R22.
A nominal quaternary refrigerant composition 5 comprising about 22% by
weight of R32; about 5% by weight of R125; about 72.4% by weight of R134a and
about 0.6% by weight of R600a as a drop-in replacement for R22.
A nominal quaternary refrigerant composition 6 comprising about 23% by
weight of R32; about 4% by weight of R125; about 72.2% by weight of R134a and
about 0.8% by weight of R600a as a drop-in replacement for R22.
In one embodiment of the present invention, the refrigerant composition
comprises of about 15% to 30% by weight of R32; about 1% to 10% by weight of
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R125; about 60% to 75% by weight of R134a and about 5% to 15% by weight of
R600a.
In one another embodiment of the present invention, the refrigerant
composition comprises of about 15% to 30% by weight of R32; about 0.1% to 5%
by weight of R125; about 60% to 75% by weight of R134a and about 5% to 15% by
weight of R600a.
In one another embodiment of the present invention, refrigerant composition
comprising about 15% to 30% by weight of R32; about 1% to 10% by weight of
R125; about 60% to 75% by weight of R134a and about 0.1% to 15% by weight of
R600a as a drop-in replacement for R22.
In one another embodiment of the present invention, refrigerant composition
comprising about 15% to 30% by weight of R32; about 1% to 10% by weight of
R125; about 60% to 75% by weight of R134a and about 0.1% to 5% by weight of
R600a as a drop-in replacement for R22.
In one another embodiment of the present invention, the nominal quaternary
refrigerant composition comprises of about 15% to 20% by weight of R32; about 1%
to 4% by weight of R125; about 60% to 75% by weight of R134a and about 5% to
10% by weight of R600a.
In one another embodiment of the present invention, the nominal quaternary
refrigerant composition comprises of about 15% to 20% by weight of R32; about 1%
to 4% by weight of R125; about 60% to 75% by weight of R134a and about 1% to
5% by weight of R600a.
In one another embodiment of the present invention, the nominal quaternary
refrigerant composition comprises of about 20% to 25% by weight of R32; about 1%
to 4% by weight of R125; about 60% to 75% by weight of R134a and about 5% to
10% by weight of R600a.
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In one another embodiment of the present invention, the nominal quaternary
refrigerant composition comprises of about 20% to 25% by weight of R32; about 1%
to 4% by weight of R125; about 60% to 75% by weight of R134a and about 1% to
5% by weight of R600a.
Refrigerant compositions in accordance with this invention confer several
advantages. R125 has fire suppressing characteristics. The presence of R125
suppresses the flammability of the refrigerant mixture. The higher HFC content
enables more isobutane to be added to the mixture thereby improving the solubility
properties of the mixture with traditional lubricants, for example mineral and alkyl
benzene oils. This composition does not have HCFC so it is a zero ODP refrigerant.
In another embodiment of the present invention, the refrigerant composition
has GWP of less than 1300.
In another embodiment of the present invention, the refrigerant composition
additionally comprises of about less than 0.5% of non-absorbable gases.
In another embodiment of the present invention, the refrigerant composition
may contain optional components selected from the group consisting of lubricants,
dyes (including Ultra Violet dyes), solubilizing agents, compatibilizers, stabilizers,
tracers, perfluoropolyethers, anti-wear agents, extreme pressure agents, corrosion
and oxidation inhibitors, metal surface energy reducers, metal surface deactivators,
free radical scavengers, foam control agents, viscosity index improvers, pour point
depressants, detergents, viscosity adjusters, and mixtures thereof. Indeed, many of
these optional other components fit into one or more of these categories and may
have qualities that lend themselves to achieve one or more performance
characteristic.
In another embodiment of this aspect of the present invention, the refrigerant
composition is a drop in replacement for R22.
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In another embodiment of this aspect of the present invention, the refrigerant
composition is a non-azeotropic mixture.
In another embodiment of this aspect of the present invention, the refrigerant
composition can be either charged as liquid composition or full vapor composition.
In another embodiment of this aspect of the present invention, the refrigerant
composition is preferably charged in liquid form.
In another embodiment of this aspect of the present invention, the refrigerant
composition has lower discharge temperature compared to R22 thus the use of this
composition increases life of the compressor and can be worked at outdoor
conditions at higher temperatures.
Refrigerant Discharge Temperature
(°C)
Liquid phase specific heat
at constant volume (Cv)
at 25°C (kj/kg-K)
R-22 57.5 0.6908
Composition 1 49.5 0.9657
Composition 2 49.8 0.9765
Composition 3 48.7 0.9571
Composition 4 49.2 0.9642
Composition 5 50.3 0.9231
Composition 6 50.1 0.9255
The refrigerant composition of the present invention has higher specific heat
capacity, lower discharge temperature and increased thermal efficiency.
In another embodiment of this aspect, the present invention provides a
refrigeration process using the refrigerant composition of the present invention
comprising the steps of:
a) Condensing the refrigerant composition;
b) Evaporating the refrigerant composition.
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The quaternary blend composition of the present invention has higher
volumetric refrigerating capacity as compared to R-22, thus need a smaller
compressor, and less power for a given capacity.
In another embodiment of this aspect of the present invention, the refrigerant
composition of present invention has lower value of viscosity that decreases pressure
drop in condenser and evaporators, leading to increase in mass flow of refrigerant,
increase in system capacity and increased Heat transfer coefficient (HTC).
Further, the refrigerant composition of present invention has higher thermal
conductivity, higher rate of evaporation and thus higher HTC.
Refrigerant Liquid phase
Viscosity at 25°C
(μPa-s)
Liquid Phase Thermal
Conductivity at 25°C
(mW/m-K)
R-22 164.39 83.479
Composition 1 146.21 86.936
Composition 2 150.75 82.98
Composition 3 150.11 86.59
Composition 4 148.96 85.82
Composition 5 161.47 87.87
Composition 6 160.20 88.40
The refrigerant composition of present invention has higher vapour pressure,
therefore it has higher volumetric refrigerant capacity (VRC) thus require smaller
compressor displacement.
Refrigerant Vapour pressure at 25°C (bars)
R-22 10.439
Composition 1 11.408
Composition 2 10.351
Composition 3 11.081
Composition 4 11.031
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Composition 5 10.535
Composition 6 10.628
The refrigerant compositions of the present invention may be used in
stationary or mobile air conditioning systems or heat exchanger systems. Preferably,
the refrigerant compositions would be utilized in domestic room air conditioning
systems.
The present invention thus provides an R22 replacement refrigerant
compositions that are compatible with existing mineral oil and alike lubricants and
do not require replacement of the expensive devices in the legacy system.
The AHRI 210/240 standard uses several different temperatures to derive the
“Seasonal” component of the rating. The highest ambient air temperature used in the
AHRI 210/240 standard is 95F (35°C), and this may result in condensing
temperatures for the refrigerant inside the condenser of between 105F and 110F
(40°C to 43°C) because the refrigerant inside the system has to be warmer than the
outside air temperature in order for the heat to move from the refrigerant to the
outside air. Conventional operation conditions for the legacy R22 systems include
these standards and their conditions.
Each of the components of the cooling system is sensitive to the composition
and amount of refrigerant flowing through it, and the legacy R22 systems are no
exception. Large changes in refrigerant flow rate as compared to the designed flow
rates will cause the amount of heat absorbed by the system to change adversely. For
example, if the refrigerant absorbs too much heat from the evaporator because the
expansion device cannot adequately slow down the flow rate of refrigerant, the
compressor will pump too much refrigerant and overload the electric motor which
could either trigger associated electrical protection circuits or permanently damage
the motor. On the other hand, if the refrigerant absorbs too little heat because the
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expansion device cannot pass enough refrigerant, the system will lose the ability to
absorb enough heat to keep the cooled area at the selected temperature.
Fortunately, legacy refrigeration systems were all designed at a time when
there were far fewer refrigerants and lubricant options. This fact caused design
engineers to use substantially the same refrigerant and lubrication performance
criteria when specifying the expansion devices, motors, etc. that were used in these
legacy systems. As a result, those systems tended to be fairly close in terms of the
tolerable range of adjustments that each could employ and still achieve acceptable
performance. The present invention is specifically designed to be a retrofit refrigerant
for R22 systems that can be used in the legacy R22 equipment with the legacy
mineral oil and alike lubricants.
The quaternary blend composition of the present invention has good chemical
miscibility with hydrocarbons/mineral oil, lubricant oil which is blown out of the
compressor will be carried through the system by this refrigerant easily so it can be
used as less expensive drop-in substitute of R-22 without any change in the hardware.
The formulation according to the invention exhibits cooling and condensation
properties that make it well suited as a retrofit for R22 refrigerants without the need
to replace the expansion devices and flow valves of the existing legacy equipment.
Specifically, the inventor has found that the existing flow control devices in legacy
equipment for R22 refrigeration systems has the ability to deliver the correct
refrigerant flow rate without affecting the continuity of the refrigerating cycle. The
refrigerant formulation of the invention exhibits cooling capacities and mass flow
rates that are within the flow adjustment tolerances of such equipment. Thus, the
refrigerant formulation of the present invention can replace the legacy R22
refrigerant using the same lubricant and the same expansion valves with only
adjustments that are within acceptable ranges of such legacy equipment.
R600a (isobutane) is commercially available.
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R32 is commercially available or may be prepared by methods known in the
art, such as by dechlorofluorination of methylene chloride.
R125 is commercially available or may be prepared by methods known in the
art, such as dechlorofluorination of 2,2-dichloro-1,1,1-trifluoroethane as described
in US Patent No. 5,399,549, incorporated herein by reference.
R134a is commercially available or may be prepared by methods know in the
art, such as by the hydrogenation of 1,1-dichloro-1 ,2,2,2-tetrafluoroethane (i.e.,
CCI2FCF3 or CFC-114a) to 1 ,1 ,1 ,2-tetrafluoroethane.
It is against this and other backgrounds, which shall be filed in a detailed
manner in complete specifications, in due course, the present invention is brought
out and explained in following non-limiting examples.
EXAMPLES
Example 1
The refrigerant compositions according to the invention having composition
of R125:R134a:R32:R600a were prepared and tested with standard ASHRAE
modeling program maintaining indoor at 27ºC dry bulb temperature (DBT) and 19ºC
wet bulb temperature (WBT) and outdoor at 35 DBT and 24 WBT.
The results are shown below in Table 2, Table 3 and Table 4.
Table 2
Refrigerant
compositions
Cooling
Capacity
Quantity
Charged Power
Consumption COP ODP GWP
R22 100% 100% 100% 100% 0.055 1760
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Composition 1 95.1 100 98.7 96.3 0 1238
Composition 2 95.5 100 101.4 94.3 0 1276
Composition 3 91.2 100 99.1 92.2 0 1276
Composition 4 95.1 100 108.1 95.1 0 1261
Composition 5 99.7 90 99 100.7 0 1254
Composition 6 96.1 90 100.4 95.71 0 1245
Table 3
Refrigerant
Liquid
phase
Vapour
Pressure
Liquid phase
specific heat
at constant
pressure (Cp)
Vapour phase
specific heat at
constant pressure
(Cp)
Liquid phase
thermal
conductivity
at 25 Degree
Celsius
bar
kj/kg-K kj/kg-K mW/m-K
R-22 10.439 1.2568 0.87237 83.479
Comparative
Composition 7.589 1.4665 1.1017 80.724
Composition 1 11.408 1.6243 1.3059 86.936
Composition 2 10.351 1.6022 1.2714 82.98
Composition 3 11.081 1.601 1.279 86.59
Composition 4 11.031 1.6086 1.2866 85.82
Composition 5 10.535 1.5389 1.1233 87.87
Composition 6 10.628 1.5467 1.1296 88.40
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Table 4
Refrigerant
Vapour
phase
thermal
conductivity
Liquid
phase
viscosity
Molar
Mass
Global Warming
Potential
at 25 Degree
Celsius mW/m-K μPa-s kg/kmol
Comparative
Composition 14.365 181.75 98.045 1406
R-22 11.337 164.39 86.468 1810
Composition 1 15.002 146.21
79.735
1238
Composition 2
15.041 150.75
84.447 1276
Composition 3
14.92 150.11
81.439 1276
Composition 4
14.98 148.96
81.573 1261
Composition 5
14.37 161.47 84.428 1254
Composition 6
14.395 160.20 83.555 1245
As depicted in Table 2, 3 and 4, the refrigerant compositions of the present
invention exhibit good cooling capacity and will operate in substantially the same
manner as the legacy R22 refrigerant under the same conditions. The performance
factor is almost close to R22 and having zero ODP.
It will be apparent to those skilled in the art that various modifications and
variations can be made in the present invention and specific examples provided
herein without departing from the spirit and scope of the invention. Thus, it is
intended that the present invention covers the modifications and variations of this
invention that come within the scope of any claims and their equivalents.

We Claim:

1. A refrigerant composition comprising about 15% to 30% by weight of R32;
about 0.1% to 10% by weight of R125; about 60% to 75% by weight of R134a
and about 0.1% to 15% by weight of R600a as a drop-in replacement for R22.
2. A refrigerant composition comprising about 15% to 30% by weight of R32;
about 0.1% to 10% by weight of R125; about 60% to 75% by weight of R134a
and about 0.1% to 5% by weight of R600a as a drop-in replacement for R22.
3. A nominal quaternary refrigerant composition comprising about 22% by
weight of R32; about 5% by weight of R125; about 72.4% by weight of
R134a and about 0.6% by weight of R600a as a drop-in replacement for R22.
4. A nominal quaternary refrigerant composition comprising about 23% by
weight of R32; about 4% by weight of R125; about 72.2% by weight of
R134a and about 0.8% by weight of R600a as a drop-in replacement for R22.
5. The claim as claimed in claim 1 to 4, wherein, the refrigerant composition is
a non-azeotropic mixture.
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6. A refrigeration process using the refrigerant composition comprising the
steps of:
a) condensing the refrigerant composition;
b) evaporating the refrigerant composition.