Note: Descriptions are shown in the official language in which they were submitted.
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REFRIGERANT COMPOSITION
This invention relates to refrigerant compositions, particularly to
refrigerant
compositions which have minimal adverse effect on stratospheric ozone. The
invention particularly relates to compositions which are for use in new and
existing
refrigeration, air conditioning and heat pumping equipment. These refrigerant
compositions are compatible with the new synthetic lubricants, including but
not
restricted to polyol ester oils and polyalkylene glycol oils.
It is well known that chlorofluorocarbons (CFCs) such as CFC12 and CFC502
and hydrochlorofluorocarbons such as HCFC22 while being energy efficient, non
flammable and of low toxicity, migrate to the stratosphere where they are
broken
down by ultra violet light to attack the ozone layer. It is desirable to
replace these
Ozone Depleting Substances (ODS) by non ozone depleting alternatives such as
hydrofluorocarbons (HFCs) which are also non flammable, efficient and of low
toxicity. There are six main HFCs, namely HFC 134a, HFC32, HFC 125, HFC 143a,
HFC227ea and HFC 152a, which either individually' or when blended into
mixtures
can replace CFCs and HCFCs. While HFC134a, HFC227ea and HFC152a can be
used to replace ODS directly, HFC32, HFC143a and HFC125 are generally found in
blends as replacements for ODS. HFCs do not have adequate solubility in
traditional
lubricants such as mineral and alkylbenzene oils so that synthetic oxygen
containing
lubricants have been introduced specifically in order that HFCs can be used in
new
equipment.
Refrigerant blends such as R404A, R507A and others have been
commercialised as replacements for CFCs and HCFCs at low temperature,
typically
operating at around -35 C in the evaporator but their performance declines as
the
temperature rises so that they are not effective, for example, as replacements
for ODS
in air conditioning applications. R404A and R507A have been formulated
primarily to
replace CFC502 at low temperatures,
Refrigerant blends such as R407C, R410A and others have been
commercialised as replacements for CFCs and HCFCs at medium to high
temperatures, typically operating at around +5 C in the evaporator and
condensing at
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around +35 C but their performance declines as the temperature decreases so
that they
are not effective, for example, as replacements for ODS in refrigeration
applications
such as are used in supermarkets. R407C and R410A have been formulated
primarily
to replace HCFC22 for air conditioning applications. R407C is a zeotrope, not
an
azeotrope or near azeotrope, so its application is further restricted by
having a
comparatively high temperature glide in the evaporator which can cause icing
at the
entry of the evaporator thus reducing the energy efficiency and the capacity
of the
system. Furthermore, R407C, being a zeotrope, is unacceptable for flooded
systems
where large composition shifts would occur resulting in large compression
ratios and
potential over-pressurisation of the condenser.
An object of this invention is to provide a refrigerant blend that can be
readily
used to replace R22 in new & existing equipment. It is especially important
that such
a blend should have an adequate refrigeration capacity. The capacity should be
at least
90% of that of the fluid it is replacing, more preferably at least 95% of that
of the fluid
it is replacing and most preferably equal to or greater than that of the fluid
it is
replacing under similar operating conditions. It is an object of this
invention to
provide refrigerant compositions which have capacities similar to R22 across
the
range of applications for air conditioning & refrigeration from high to low
temperatures where R22 is commonly found.
There is no HFC refrigerant blend which has been commercialised which has a
safety classification of A1 according to ASHRAE Standard 34, being of low
toxicity
and non flammable, which can match the capacity, performance and pressures of
HFCF22 across the range of applications where HCFC22 is found including
refrigeration and air conditioning applications including centrifugal
chillers. An object
of this invention is to provide refrigerant compositions with low temperature
glides of
less than 2 C that match the thermodynamic performance of HCFC22 across the
temperature range of applications where HCFC22 is commonly found including
refrigeration and air conditioning applications operating at evaporator
temperatures
ranging from +5 C to -40 C.
It is known in the art that high compression ratios can result in increased
energy usage and the potential for compressor damage. This invention relates
to
refrigerant compositions which have compression ratios which should be at
least no
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more than 10% of that of the fluid it is replacing, more preferably no more
than 5% of
that of the fluid it is replacing and most preferably equal to or lower than
that of the
fluid it is replacing under similar operating conditions. Preferred aspects of
this
invention relate to refrigerant compositions which have compression ratios
which are
similar to R22 across the range of applications for air conditioning &
refrigeration
from high to low temperatures where R22 is commonly found.
Various terms have been used in patent literature to describe refrigerant
mixtures. The following definitions are taken from Standard 34 of the American
Society of Heating, Refrigerating & Air Conditioning Engineers (ASHRAE);
Azeotrope: an azeotropic blend is one containing two or more refrigerants
whose equilibrium vapour and liquid phase compositions are the same at a given
pressure. Azeotropic blends exhibit some segregation of components at other
conditions. The extent of the segregation depends on the particular azeotrope
and the
application.
Azeotropic temperature: the temperature at which the liquid and vapour phases
of a blend have the same mole fractionation of each component at equilibrium
for a
specified pressure.
Near azeotrope: a zeotropic blend with a temperature glide sufficiently small
that it may be disregarded without consequential error in analysis for a
specific
application.
Zeotrope: blends comprising multiple components of different volatilities
that,
when used in refrigeration cycles, change volumetric composition and
saturation
temperatures as they evaporate (boil) or condense at constant pressure.
Temperature glide: the absolute value of the difference between the starting
and ending temperatures of a phase-change process by a refrigerant within a
component of a refrigerating system, exclusive of any subcooling or
superheating.
This term usually describes condensation or evaporation of a zeotrope.
According to the present invention, a refrigerant composition consists of:
a refrigerant composition suitable for air conditioning, refrigeration and
heat pumping
applications consisting essentially of:
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R134a 10 to 20%
R125 40 to 65%
R143a 50 to 15%
wherein the percentages above are selected to total 100%.
A preferred composition consists essentially of:
R134a 10 to 20%
R125 40 to 60%
R143a 50 to 20%.
A further preferred composition consists essentially of:
R134a 10 to 20%
R125 40 to 55%
R143a 50 to 25%.
A further preferred composition consists essentially of:
R134a 10 to 20%
R125 40 to 50%
R143a 50 to 30%
A further preferred composition consists essentially of:
R134a 10 to 20%
R125 40 to 45%
R143a 50 to 35%
A further preferred composition consists essentially of:
R134a 15 to 20%
R125 40 to 65%
R143a 45 to 15%
A further preferred composition consists essentially of:
R134a 15 to 20%
R125 40 to 60%
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R143a 45 to 20%
A further preferred composition consists essentially of:
R134a 15 to 20%
R125 40 to 55%
5 R143a 45 to 25%
A further preferred composition consists essentially of:
R134a 15 to 20%
R125 40 to 50%
R143a 45 to 30%
An especially preferred composition consists essentially of:
R134a 15%
R125 65%
R143a 20%
A further especially preferred composition consists essentially of:
R134a 15%
R125 60%
R143a 25%
A further especially preferred composition consists essentially of:
R134a 15%
R125 55%
R143a 30%
A further especially preferred composition consists essentially of:
R134a 15%
R125 50%
R143a 35%
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A further especially preferred composition consists essentially of:
R134a 15%
R125 45%
R143a 40%
A further especially preferred composition consists essentially of:
R134a 20%
R125 65%
R143a 15%
A further especially preferred composition consists essentially of:
R134a 20%
R125 60%
R143a 20%
A further especially preferred composition consists essentially of:
R134a 20%
R125 55%
R143a 25%
A further especially preferred composition consists essentially of:
R134a 20%
R125 50%
R143a 30%
A further especially preferred composition consists essentially of:
R134a 20%
R125 45%
R143a 35%
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A further especially preferred composition consists essentially of:
R134a 20%
R125 40%
R143a 40%
A further especially preferred composition consists essentially of:
R134a 16%
R125 42%
R143a 42%
A further especially preferred composition consists essentially of:
R134a 17%
R125 42%
R143a 41%
A further especially preferred composition consists essentially of:
R134a 19%
R125 41%
R143a 41%
A further especially preferred composition consists essentially of:
R134a 18%
R125 41%
R143a 40%
The compositions of this iinvention consist of the components mentioned
above, optionally with small amounts of impurities or additives in an amount
which is
not sufficient to affect the essential properties of the composition.
Preferably no
additives are used.
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Preferred compositions meet the criteria for safety classifications A 1 and A2
of ASHRAE Standard 34 or meet the criteria for safety classification Al of
ASHRAE
Standard 34
The compositions may be used in an air conditioning unit with a synthetic
oxygen- containing lubricant or may be used in a refrigeration unit with a
synthetic
oxygen containing lubricant.
The lubricant may be a polyol ester, a polyether or a mixture of oxygen-
containing lubricants.
The compositions may be used in a hermetic or semi-hermetic refrigeration
unit providing cold temperatures in a range between about 0 C and about -45
C, or
may be used in an open refrigeration unit driven by an external power source
providing cold temperatures in a range between about 0 C and about -45 C. The
compositionsr may be used in an hermetic or semi-hermetic air conditioning
unit
providing cold temperatures in a range between about 0 C and about 20 C, or
may
be used in an hermetic or semi-hermetic heat pump unit providing warm
temperatures
in a range between about 15 C and about 50 C.
The composition may also be used in an open air conditioning unit driven by
an external power source providing cold temperatures in a range between about
0 C
and about 20 C.
The composition may be used in an open heat pump unit driven by an external
power source providing warm temperatures in a range between about 15 C and
about
50 C.
These compositions preferably meet the criteria for safety classification A2
of
ASHRAE Standard 34 and more preferably meet the stricter Al classification.
Preferred compositions comprise near azeotropic and zeotropic refrigerant
compositions, which are non flammable under all conditions of fractionation as
defined under ASHRAE Standard 34, and which can be used to replace HCFC22 in
new & existing equipment across the application ranges including refrigeration
and air
conditioning and centrifugal chillers. These refrigerant applications are
compatible
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with the oxygen containing synthetic lubricants including but not restricted
to polyol
ester, polalkylbenzene & polether oils.
Not all HFCs are non flanunable as defined under ASHRAE Standard 34.
HFC143a and HFC32 have not received a non flammable rating by ASHRAE.
Preferred embodiments of this invention relate to compositions of refrigerants
which
cover blends of non flammable HFCs with flammable HFCs selected so that all
such
compositions are non flammable during fractionation while providing similar
refrigerating effects and thermodynamic performances to HCFC22.
To avoid flammability in the blend, or in a fraction generated by a leak, for
example as defined by ASHRAE Standard 34, the ratio of flammable HFC to non
flammable HFC should be minimised but without adversely affecting the
thermodynamic performance of the composition. One of the HFC components of
this invention, namely HFC 143a, has an ASHRAE safety classification of A2
which
makes limitation of the amount of HFC143a used relative to the amounts of non-
flammable components important to obtaining a non flammable rating of A1 for
the
blend.
Preferred compositions in accordance with this invention may not contain any
hydrocarbon compound.
Preferred compositions provide very similar performance to HCFC22 across
the evaporating temperature range commonly associated with HCFC22.
Percentages and other proportions referred to in this specification are by
weight unless indicated otherwise and are selected to total 100% from within
the
ranges disclosed.
The invention is further described by means of examples but not in a
limitative
sense.
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Example 1
Blends of R125, R143a and R134a were evaluated in a typical hermetic or semi-
hermetic air conditioner using NIST's CYCLE D program.
COOLING DUTY DELIVERED 10 kW
5 EVAPORATOR
Midpoint evaporating temperature 7 C
Superheating 5.0 C
Suction line pressure drop (in saturated temperature) 1.5 C
CONDENSER
10 Midpoint fluid condensing temperature 45.0 C
Subcooling 5.0 C
Discharge line pressure drop (in saturated temperature) 1.5 C
LIQUID LINE/SUCTION LINE HEAT EXCHANGER
Efficiency 0.3
COMPRESSOR
Compressor isentropic efficiency 0.7
Compressor volumetric efficiency 0.82
Motor efficiency 0.85
PARASITIC POWER
Evaporator fan 0.3 kW
Condenser fan 0.4 kW
Controls 0.1 kW
The results of analysing the performances in an air conditioning unit using
these
operating parameters are shown in Table 1, plus R22 for comparison.
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Example 2
Blends of R125, R143a and R134a were evaluated in a typical open compressor
refrigeration unit using NIST's CYCLE D program.
COOLING DUTY DELIVERED 10 kW
EVAPORATOR
Midpoint evaporating temperature -35 C
Superheating 5.0 C
Suction line pressure drop (in saturated temperature) 1.5 C
CONDENSER
Midpoint fluid condensing temperature 35.0 C
Subcooling 5.0 C
Discharge=line pressure drop (in saturated temperature) 1.5 C
LIQUID LINE/SUCTION LINE HEAT EXCHANGER
Efficiency 0.3
COMPRESSOR
Compressor isentropic efficiency 0.7
Compressor volumetric efficiency 0.82
Motor efficiency 0.85
PARASITIC POWER
Evaporator fan 0.3 kW
Condenser fan 0.4 kW
Controls 0.1 kW
The results of analysing the performances in a refrigerator unit using these
operating parameters are shown in Table 2, plus R22 for comparison.
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