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United States Patent |
6,254,798
|
Minor
,   et al.
|
July 3, 2001
|
Nitrous oxide compositions
Abstract
This invention relates to compositions that include nitrous oxide and at
least one of trifluoromethane, difluoromethane, tetrafluoroethane,
pentafluoroethane, perfluoroethane or ethane. These compositions are
useful as refrigerants, cleaning agents, expansion agents for polyolefins
and polyurethanes, refrigerants, aerosol propellants, heat transfer media,
electronic gases, plasma etchants, gaseous dielectrics, fire extinguishing
agents, power cycle working fluids, polymerization media, particulate
removal fluids, carrier fluids, buffing abrasive agents, and displacement
drying agents.
Inventors:
|
Minor; Barbara Haviland (Elkton, MD);
Bivens; Donald Bernard (Kennett Square, PA);
Rice; Clifford Keith (Clinton, TN);
Sand; James Richard (Oak Ridge, TN)
|
Assignee:
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E. I. du Pont de Nemours and Company. (Wilmington, DE)
|
Appl. No.:
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044303 |
Filed:
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March 19, 1998 |
Intern'l Class: |
C09K 005/04 |
Field of Search: |
252/67
510/415,409
|
References Cited
U.S. Patent Documents
3723318 | Mar., 1973 | Butler | 252/67.
|
3812040 | May., 1974 | Borchardt | 252/68.
|
5340490 | Aug., 1994 | Decaire et al. | 252/67.
|
5766503 | Jun., 1998 | Shiflett et al. | 252/67.
|
Foreign Patent Documents |
3-303 240 | Nov., 1991 | JP.
| |
5-259128 | Oct., 1993 | JP.
| |
94/01512 | Jan., 1994 | WO.
| |
Other References
Chemical Abstracts, 77:50685, "Predicting critical temperature of
azeotropes", Li, 1972.
David A. Didion and Donald B. Bivens, Role of Refrigerant Mixtures As
Alternatives to CFCs, ASHRAE CFC Technology Conference, Gaithersburg, MD
in 1989, May, 1990.
R. L. Powell, Extending the Range, International Conference Proceedings,
CFCs, The Day After, Joint Meeting of IIR Commissions B1, B2, E1 and E2,
Padova, Italy, 11-19, Sep. 21-23, 1994.
|
Primary Examiner: Skane; Christine
Attorney, Agent or Firm: Edwards; Mark A.
Parent Case Text
This application claims the benefit of U.S. Provisional Application No.
60/043,109, filed Apr. 17, 1997.
Claims
It is claimed that:
1. An azeotrope-like composition consisting essentially of from 40 to about
99 weight percent nitrous oxide and from about 1 to 60 weight percent
trifluoromethane (HFC-23), said composition having a vapor pressure of
from about 762 psia (5254 kPa) to about 791.5 psia (5457 kPa) at a
temperature of about 25.degree. C.
2. An azeotropic composition consisting essentially of about 84.7 weight
percent nitrous oxide and about 15.3 weight percent trifluoromethane
(HFC-23), wherein when the temperature has been adjusted to about
-30.degree. C., said composition has a vapor pressure of about 192.8 psia
(1329 kPa).
3. An azeotropic composition consisting essentially of about 75.9 weight
percent nitrous oxide and about 24.1 weight percent trifluoromethane
(HFC-23) wherein when the temperature has been adjusted to about
25.degree. C., said composition has a vapor pressure of about 791.5 psia
(5457 kPa).
4. A process for cooling a body, comprising evaporating the composition of
claims 1, 2, or 3 in the vicinity of the body to be cooled.
5. A process for producing refrigeration, comprising condensing a
composition of any of claims 3 and thereafter evaporating said composition
in the vicinity of the body to be cooled.
Description
FIELD OF THE INVENTION
This invention relates to compositions that contain nitrous oxide and at
least one compound selected from the group consisting of trifluoromethane,
difluoromethane, tetrafluoroethane, pentafluoroethane, perfluoroethane and
ethane. These compositions are useful as refrigerants, cleaning agents,
expansion agents for polyolefins and polyurethanes, refrigerants, aerosol
propellants, heat transfer media, electronic gases, plasma etchants,
gaseous dielectrics, fire extinguishing agents, power cycle working
fluids, polymerization media, particulate removal fluids, carrier fluids,
buffing abrasive agents, and displacement drying agents.
BACKGROUND OF THE INVENTION
Fluorinated hydrocarbons have many uses, one of which is as a refrigerant.
Such refrigerants include dichlorodifluoromethane (CFC-12) and
chlorodifluoromethane (HCFC-22).
In recent years it has been pointed out that certain kinds of fluorinated
hydrocarbon refrigerants released into the atmosphere may adversely affect
the stratospheric ozone layer. Although this proposition has not yet been
completely established, there is a movement toward the control of the use
and the production of certain chlorofluorocarbons (CFCs) and
hydrochlorofluorocarbons (HCFCs) under an international agreement.
Accordingly, there is a demand for the development of refrigerants that
have a lower ozone depletion potential than existing refrigerants while
still achieving an acceptable performance in refrigeration applications.
Hydrofluorocarbons (HFCs) have been suggested as replacements for CFCs and
HCFCs since HFCs have no chlorine and therefore have zero ozone depletion
potential.
In refrigeration applications, a refrigerant is often lost during operation
through leaks in shaft seals, hose connections, soldered joints and broken
lines. In addition, the refrigerant may be released to the atmosphere
during maintenance procedures on refrigeration equipment. If the
refrigerant is not a pure component or an azeotropic or azeotrope-like
composition, the refrigerant composition may change when leaked or
discharged to the atmosphere from the refrigeration equipment, which may
cause the refrigerant to become flammable or to have poor refrigeration
performance.
Accordingly, it is desirable to use as a refrigerant a single fluorinated
hydrocarbon or an azeotropic or azeotrope-like composition that includes
at least one fluorinated hydrocarbon.
Refrigerant compositions of the invention which are non-azeotropic, i.e.,
zeotropic may also be useful in vapor compression systems. See Didion, The
Role of Refrigerant Mixtures as Alternatives, Proceedings of ASHRAE CFC
Technology Conference, Gaithersburg, Md., 1989. Non-azeotropic mixtures
can boil over a wide temperature range under constant pressure conditions
and create a temperature glide in the evaporator and in the condenser.
This temperature glide can reduce the energy required to operate the
system by taking advantage of the Lorenz cycle. The preferred method
involves the use of counter current flow evaporator and/or condenser heat
exchangers in which the refrigerant and the heat transfer fluid flow
countercurrently. This method decreases the temperature difference between
the evaporating and condensing refrigerant but maintains a high enough
temperature difference between the refrigerant and external heat transfer
fluid to effectively transfer heat. Another benefit of this type of system
is that pressure differences are also minimized. This can result in an
improvement in energy efficiency and/or capacity versus conventional
systems.
Azeotropic, azeotrope-like, or zeotropic compositions that include a
fluorinated hydrocarbon are also useful as blowing agents in the
manufacture of closed-cell polyurethane, phenolic and thermoplastic foams,
as propellants in aerosols, as heat transfer media, electronic gases,
plasma etchants, gaseous dielectrics, fire extinguishing agents, power
cycle working fluids such as for heat pumps, inert media for
polymerization reactions, fluids for removing particulates from metal
surfaces, as carrier fluids that may be used, for example, to place a fine
film of lubricant on metal parts, as buffing abrasive agents to remove
buffing abrasive compounds from polished surfaces such as metal, as
displacement drying agents for removing water, such as from jewelry or
metal parts, as resist developers in conventional circuit manufacturing
techniques including chlorine-type developing agents, or as strippers for
photoresists when used with, for example, a chlorohydrocarbon such as
1,1,1-trichloroethane or trichloroethylene.
A farther utility for the nitrous oxide compositions of the present
invention is a process for etching a thin film device comprising the steps
of:
a) contacting said device with at least one nitrous oxide composition; and
b) forming a plasma from said composition during said contacting whereby
said device is etched.
At least one oxygen-containing additive gas such as O.sub.2, O.sub.3, CO,
CO.sub.2, NO, and NO.sub.2 is optionally employed in concert with the
nitrous oxide compositions of the present invention for plasma etching of
thin film devices. Of the oxygen-containing additive gases, O.sub.2 is the
most preferred.
At least one secondary additive gas is optionally employed in concert with
the nitrous oxide compositions of the present invention for plasma etching
of thin film devices. These secondary additive gases include fluorinated
gases such as CF.sub.4, CH.sub.2 F.sub.2, CH.sub.3 F, CF.sub.3 --CF.sub.3,
CF.sub.3 --CF.sub.2 H, CF.sub.3 --CH.sub.2 F, CF.sub.2 H--CF.sub.2 H,
CF.sub.2 H--CFH.sub.2, CH.sub.3 --CF.sub.2 H, CH.sub.2 F--CH.sub.2 F,
C.sub.3 F.sub.8, NF.sub.3, SF.sub.6, and well as ion-producing inert gases
such as helium, neon, and argon.
A common reactor for carrying out the plasma etching utility of the nitrous
oxide compositions of the present invention is a capacitively-coupled
parallel-plate plasma processing reactor. Such reactors are widely used
and well known in the semiconductor industry. A representative example of
such a reactor system is described by Hargis, et. al., in a paper titled
"The Gaseous Electronics Conference Radio-Frequency Reference Cell: A
Defined Parallel-Plate Radio-Frequency System For Experimental and
Theoretical Studies of Plasma-Processing Discharges" in the Review of
Scientific Instruments, volume 65, 1994, page 140. Such a reactor is
useful for precision etching of thin films of silicon; dielectric
materials such as silicon dioxide, silicon nitride, silicon oxynitride,
and doped dielectric oxides such as phosphosilicate glass,
borophosphosilicate glass and other dielectric materials; conductive
materials such as tungsten, molybdenum, titanium, tantalum and suicides of
these materials as found on thin film devices, such as semiconductor
wafers and flat panel displays; micro-mechanical devices; and similar
structures employing semiconductor fabrication technology.
The plasma etching utility of the nitrous oxide compositions of the present
invention is not restricted to the aforementioned reactor configuration,
and can be employed in other systems useful for plasma activation of
gaseous reactant species. Such systems include diode parallel-plate
systems using either radio-frequency power (commonly at 13.56 MHz) or
audio-frequency power (commonly in the range 100-400 Hz), or a combination
of the previous two in systems commonly referred to as triode systems. In
addition, the power can be alternatively applied by inductive rather than
capacitive means, using a variety of planar and loop antennas known in the
art; some such systems include helicon or helical resonator
configurations, with other types of coupling also applicable.
Additionally, microwave frequency excitation (commonly at 2.45 GHz) can
also be used. A variety of configurations may be used, including but not
limited to the configurations commonly referred to as electron cyclotron
resonance (ECR) systems.
SUMMARY OF THE INVENTION
The present invention relates to the discovery of compositions that
containing nitrous oxide and at least one compound selected from the group
consisting of trifluoromethane, difluoromethane, tetrafluoroethane,
pentafluoroethane, perfluoroethane or ethane.
Specifically, the present invention relates to the discovery of
compositions of trifluoromethane (HFC-23) and nitrous oxide (N.sub.2 O);
N.sub.2 O and ethane; HFC-23, perfluoroethane (FC-116) and N.sub.2 O;
difluoromethane (HFC-32), pentafluoroethane (HFC-125) and N.sub.2 O;
HFC-32, HFC-125, N.sub.2 O and ethane; HFC-32, HFC-125,
1,1,1,2-tetrafluoroethane (HFC-134a) and N.sub.2 O. These compositions are
useful as refrigerants, cleaning agents, expansion agents for polyolefins
and polyurethanes, refrigerants, aerosol propellants, heat transfer media,
electronic gases, plasma etchants, gaseous dielectrics, fire extinguishing
agents, power cycle working fluids, polymerization media, particulate
removal fluids, carrier fluids, buffing abrasive agents, and displacement
drying agents.
Further, the invention relates to the discovery of binary and ternary
azeotropic or azeotrope-like compositions comprising effective amounts of
HFC-23 and N.sub.2 O; N.sub.2 O and ethane; HFC-23, FC-116 and N.sub.2 O;
HFC-32, HFC-125 and N.sub.2 O to form an azeotropic or azeotrope-like
composition.
Further, the invention relates to the discovery of quarternary zeotropic
compositions comprising effective amounts of HFC-32, HFC-125, N.sub.2 O
and ethane; and HFC-32, HFC-125, HFC-134a and N.sub.2 O to form a
non-azeotrope or zeotropic composition.
DETAILED DESCRIPTION
The present invention relates to the discovery of compositions that include
nitrous oxide and at least one of trifluoromethane, difluoromethane,
tetrafluoroethane, pentafluoroethane, perfluoroethane or ethane.
Specifically, the present invention relates to compositions of HFC-23 and
N.sub.2 O; N.sub.2 O and ethane; HFC-23, FC-116 and N.sub.2 O; HFC-32,
HFC-125 and N.sub.2 O; HFC-32, HFC-125, N.sub.2 O and ethane; HFC-32,
HFC-125, HFC-134a and N.sub.2 O.
The present invention also relates to the discovery of azeotropic or
azeotrope-like compositions of effective amounts of HFC-23 and N.sub.2 O;
N.sub.2 O and ethane; HFC-23, FC-116 and N.sub.2 O; HFC-32, HFC-125 and
N.sub.2 O to form an azeotropic or azeotrope-like composition.
The present invention also relates to the discovery of zeotropic
compositions of effective amounts of HFC-32, HFC-125, N.sub.2 O and
ethane; and HFC-32, HFC-125, HFC-134a and N.sub.2 O.
By "azeotropic" composition is meant a constant boiling liquid admixture of
two or more substances that behaves as a single substance. One way to
characterize an azeotropic composition is that the vapor produced by
partial evaporation or distillation of the liquid has the same composition
as the liquid from which it was evaporated or distilled, that is, the
admixture distills/refluxes without compositional change. Constant boiling
compositions are characterized as azeotropic because they exhibit either a
maximum or minimum boiling point, as compared with that of the
non-azeotropic mixtures of the same components.
By "azeotrope-like" composition is meant a constant boiling, or
substantially constant boiling, liquid admixture of two or more substances
that behaves as a single substance. One way to characterize an
azeotrope-like composition is that the vapor produced by partial
evaporation or distillation of the liquid has substantially the same
composition as the liquid from which it was evaporated or distilled, that
is, the admixture distills/refluxes without substantial composition
change.
It is recognized in the art that a composition is azeotrope-like if, after
50 weight percent of the composition is removed such as by evaporation or
boiling off, the difference in vapor pressure between the original
composition and the composition remaining after 50 weight percent of the
original composition has been removed is about 10 percent or less, when
measured in absolute units. By absolute units, it is meant measurements of
pressure and, for example, psia, atmospheres, bars, torr, dynes per square
centimeter, millimeters of mercury, inches of water and other equivalent
terms well known in the art. If an azeotrope is present, there is no
difference in vapor pressure between the original composition and the
composition remaining after 50 weight percent of the original composition
has been removed.
Therefore, included in this invention are compositions of effective amounts
of HFC-23 and N.sub.2 O; N.sub.2 O and ethane; HFC-23, FC-116 and N.sub.2
O; HFC-32, HFC-125 and N.sub.2 O such that after 50 weight percent of an
original composition is evaporated or boiled off to produce a remaining
composition, the difference in the vapor pressure between the original
composition and the remaining composition is 10 percent or less.
For compositions that are azeotropic, there is usually some range of
compositions around the azeotrope that, for a maximum boiling azeotrope,
have boiling points at a particular pressure higher than the pure
components of the composition at that pressure and have vapor pressures
lower at a particular temperature than the pure components of the
composition at that temperature, and that, for a minimum boiling
azeotrope, have boiling points at a particular pressure lower than the
pure components of the composition at that pressure and have vapor
pressures higher at a particular temperature than the pure components of
the composition at that temperature. Boiling temperatures and vapor
pressures above or below that of the pure components are caused by
unexpected intermolecular forces between and among the molecules of the
compositions, which can be a combination of repulsive and attractive
forces such as van der Waals forces and hydrogen bonding.
The range of compositions that have a maximum or minimum boiling point at a
particular pressure, or a maximum or minimum vapor pressure at a
particular temperature, may or may not be coextensive with the range of
compositions that are substantially constant boiling. In those cases where
the range of compositions that have maximum or minimum boiling
temperatures at a particular pressure, or maximum or minimum vapor
pressures at a particular temperature, are broader than the range of
compositions that are substantially constant boiling according to the
change in vapor pressure of the composition when 50 weight percent is
evaporated, the unexpected intermolecular forces are nonetheless believed
important in that the refrigerant compositions having those forces that
are not substantially constant boiling may exhibit unexpected increases in
the capacity or efficiency versus the components of the refrigerant
composition.
By "zeotropic" composition is meant a non-constant boiling liquid admixture
of two or more substances. Non-azeotropic mixtures can boil over a wide
temperature range under constant pressure conditions and create a
temperature glide in the evaporator and in the condenser. This temperature
glide can reduce the energy requited to operate the system by taking
advantage of the Lorenz cycle. The preferred method involves the use of
counter current flow evaporator and/or condenser heat exchangers in which
the refrigerant and the heat transfer fluid flow countercurrently. This
method decreases the temperature difference between the evaporating and
condensing refrigerant but maintains a high enough temperature difference
between the refrigerant and external heat transfer fluid to effectively
transfer heat. Another benefit of this type of system is that pressure
differences are also minimized. This can result in an improvement in
energy efficiency and/or capacity versus conventional systems.
It is recognized in the art that a composition is zeotropic if, after 50
weight percent of the composition is removed such as by evaporation or
boiling off, the difference in vapor pressure between the original
composition and the composition remaining after 50 weight percent of the
original composition has been removed is greater than 10 percent, when
measured in absolute units. By absolute units, it is meant measurements of
pressure and, for example, psia, atmospheres, bars, torr, dynes per square
centimeter, millimeters of mercury, inches of water and other equivalent
terms well known in the art.
It is also recognized in the art that a composition is zeotropic if the
temperature glide in the evaporator and/or condenser is greater than about
3.degree. C.
Therefore, included in this invention are compositions of effective amounts
of HFC-32, HFC-125, N.sub.2 O and ethane; HFC-32, HFC-125, HFC-134a and
N.sub.2 O to form a zeotropic mixture. Addition of N.sub.2 O to a ternary
mixture such as HFC-32/HFC-125/HFC-134a results in a more linear
temperature glide profile and thereby provides more effective utilization
of heat transfer surfaces.
The components of the compositions of this invention have the following
vapor pressures at the temperature specified.
25.degree. C. -30.degree. C.
Components Psia kPa Psia kPa
HFC-23 665.5 4588 148.0 1020
HFC-32 246.7 1701 40.4 279
FC-116 453.9 3130 109.8 757
HFC-125 199.1 1373 32.9 227
HFC-134a 98.3 677 12.2 84
N.sub.2 O 769.7 5307 189.4 1306
Ethane 566.3 3905 152.9 1054
Substantially constant boiling, azeotropic or azeotrope-like compositions
of this invention comprise the following at the temperature specified:
Weight Ranges Preferred Ranges
Components T.degree. C. (wt. %/wt. %) (wt. %/wt. %)
23/N.sub.2 O -30 1-99/1-99 10-99/1-90
N.sub.2 O/Ethane -30 1-99/1-99 40-99/1-60
23/116/N.sub.2 O 25 1-98/1-79/1-98 1-70/10-80/1-60
32/125/N.sub.2 O 25 15-84/15-84/1-5 15-60/30-84/1-5
Substantially constant boiling zeotropic compositions of this invention
comprise the following at the temperature specified:
Weight Ranges Preferred Ranges
Components T.degree. C. (wt. %/wt. %) (wt. %/wt. %)
32/125/N.sub.2 O/ethane -30 5-40/30-90/1-20/1-10 10-30/40-80/
1-10/1-5
32/125/134a/N.sub.2 O -30 5-50/10-60/20-70/1-20 20-40/10-30/
30-50/1-15
For purposes of this invention, "effective amount" is defined as the amount
of each component of the inventive compositions which, when combined,
results in the formation of an azeotropic or azeotrope-like composition.
This definition includes the amounts of each component, which amounts may
vary depending on the pressure applied to the composition so long as the
azeotropic or azeotrope-like compositions continue to exist at the
different pressures, but with possible different boiling points.
Therefore, effective amount includes the amounts, such as may be expressed
in weight percentages, of each component of the compositions of the
instant invention which form azeotropic or azeotrope-like compositions at
temperatures or pressures other than as described herein.
For the purposes of this discussion, azeotropic or constant-boiling is
intended to mean also essentially azeotropic or essentially-constant
boiling. In other words, included within the meaning of these terms are
not only the true azeotropes described above, but also other compositions
containing the same components in different proportions, which are true
azeotropes at other temperatures and pressures, as well as those
equivalent compositions which are part of the same azeotropic system and
are azeotrope-like in their properties. As is well recognized in this art,
there is a range of compositions which contain the same components as the
azeotrope, which will not only exhibit essentially equivalent properties
for refrigeration and other applications, but which will also exhibit
essentially equivalent properties to the true azeotropic composition in
terms of constant boiling characteristics or tendency not to segregate or
fractionate on boiling.
It is possible to characterize, in effect, a constant boiling admixture
which may appear under many guises, depending upon the conditions chosen,
by any of several criteria:
The composition can be defined as an azeotrope of A, B, C (and D . . . )
since the very term "azeotrope" is at once both definitive and limitative,
and requires that effective amounts of A, B, C (and D . . . ) for this
unique composition of matter which is a constant boiling composition.
It is well known by those skilled in the art, that, at different pressures,
the composition of a given azeotrope will vary at least to some degree,
and changes in pressure will also change, at least to some degree, the
boiling point temperature. Thus, an azeotrope of A, B, C (and D . . . )
represents a unique type of relationship but with a variable composition
which depends on temperature and/or pressure. Therefore, compositional
ranges, rather than fixed compositions, are often used to define
azeotropes.
The composition can be defined as a particular weight percent relationship
or mole percent relationship of A, B, C (and D . . . ), while recognizing
that such specific values point out only one particular relationship and
that in actuality, a series of such relationships, represented by A, B, C
(and D . . . ) actually exist for a given azeotrope, varied by the
influence of pressure.
An azeotrope of A, B, C (and D . . . ) can be characterized by defining the
compositions as an azeotrope characterized by a boiling point at a given
pressure, thus giving identifying characteristics without unduly limiting
the scope of the invention by a specific numerical composition, which is
limited by and is only as accurate as the analytical equipment available.
The azeotrope or azeotrope-like compositions of the present invention can
be prepared by any convenient method including mixing or combining the
desired amounts. A preferred method is to weigh the desired component
amounts and thereafter combine them in an appropriate container.
For the purposes of this discussion, zeotropic is intended to mean also
essentially non-azeotropic or not constant boiling. The zeotropic
compositions of the present invention can be prepared by any convenient
method including mixing or combining the desired amounts. A preferred
method is to weigh the desired component amounts and thereafter combine
them in an appropriate container.
Specific examples illustrating the invention are given below. Unless
otherwise stated therein, all percentages are by weight. It is to be
understood that these examples are merely illustrative and in no way are
to be interpreted as limiting the scope of the invention.
EXAMPLE 1
Phase Study
A phase study shows the following composition is azeotropic. The
temperature is specified below.
Vapor Pressure
Composition T(.degree. C.) Weight Percents psia kPa
23/N.sub.2 O -30 15.3/84.7 192.8 1329
N.sub.2 O/Ethane -30 75.1/24.9 213.2 1470
23/116/N.sub.2 O 25 15.1/33.9/51.0 826.9 5701
EXAMPLE 2
Impact of Vapor Leakage on Vapor Pressure
A vessel is charged with an initial liquid composition. The liquid, and the
vapor above the liquid, are allowed to come to equilibrium, and the vapor
pressure in the vessel is measured. Vapor is allowed to leak from the
vessel, while the temperature is held constant at the specified
temperature until 50 weight percent of the initial charge is removed, at
which time the vapor pressure of the composition remaining in the vessel
is measured. The results are summarized below.
0% change
Refrigerant 0 wt % evaporated 50 wt % evaporated in vapor
Composition psia kPa psia kPa pressure
23/N.sub.2 O (-30.degree. C.)
1/99 190.0 1310 189.9 1309 0.1
10/90 192.5 1327 192.4 1327 0.0
15.3/84.7 192.8 1329 192.8 1329 0.0
30/70 191.1 1318 190.4 1313 0.4
50/50 184.2 1270 181.7 1253 1.4
70/30 172.8 1280 169.4 1168 2.0
90/10 157.6 1087 155.8 1074 1.1
99/1 149.9 1034 149.7 1032 0.1
N.sub.2 O/ethane (-30.degree. C.)
1/99 156.3 1078 155.6 1073 0.4
20/80 178.7 1232 171.3 1181 4.1
40/60 197.5 1362 191.2 1318 3.2
60/40 209.8 1447 208.1 1435 0.8
75.1/24.9 213.2 1470 213.2 1470 0.0
90/10 207.7 1432 205.6 1418 1.0
99/1 193.9 1337 192.9 1330 0.5
23/116/N.sub.2 O (25.degree. C.)
15.1/33.9/51.0 826.9 5701 826.9 5701 0.0
1/1/98 775.0 5343 772.8 5328 0.3
1/98/1 501.7 3459 466.1 3214 7.1
98/1/1 672.8 4639 669.9 4619 0.4
42/50/8 768.6 5299 763.7 5266 0.6
46/54/1 744.4 5132 741.4 5112 0.4
20/40/40 823.9 5681 822.7 5672 0.1
40/20/40 809.5 5581 802.9 5536 0.8
40/40/20 797.0 5495 793.3 5470 0.5
80/10/10 729.7 5031 713.4 4919 2.2
10/80/10 721.8 4977 647.8 4466 10.3
10/79/11 729.2 5028 658.5 4540 9.7
10/10/80 806.9 5563 800.0 5516 0.9
32/125/N.sub.2 O (25.degree. C.)
27/70/3 260.9 1799 240.8 1660 7.7
29/70/1 242.2 1670 234.3 1615 3.3
26/70/4 270.1 1862 244.2 1684 9.6
50/49/1 249.9 1723 243.5 1679 2.6
50/45/5 284.5 1962 256.7 1770 9.8
15/84/1 232.1 1600 223.3 1540 3.8
15/82/3 253.4 1747 231.7 1598 8.6
80/19/1 253.0 1744 247.5 1706 2.2
80/15/5 283.5 1955 257.8 1777 9.1
84/15/1 253.0 1744 247.6 1707 2.1
32/125/N.sub.2 O/ethane (25.degree. C.)
22/75/2/1 275.6 1900 238.1 1642 13.6
5/80/10/5 416.0 2868 309.5 2134 25.6
40/30/20/10 544.5 3754 435.3 3001 20.1
40/50/9/1 342.0 2358 276.0 1903 19.3
5/90/3/2 296.2 2042 234.1 1614 21.0
14/80/1/5 348.4 2402 255.8 1764 26.6
15/60/20/5 491.6 3389 384.0 2648 21.9
HFC-32/HFC-125/HFC-134a/N.sub.2 O (25.degree. C.)
32/18/42/8 259.9 1792 188.7 1301 37.7
5/30/60/5 193.9 1337 136.0 938 29.9
50/20/22/8 285.1 1966 228.8 1578 19.7
30/10/50/10 267.2 1842 179.9 1240 32.7
10/60/29/1 192.2 1325 172.2 1187 10.4
20/50/20/10 298.2 2056 226.4 1560 24.1
9/20/70/1 148.4 1023 124.4 858 16.2
10/30/40/20 352.5 2430 220.6 1521 37.4
The results of this Example show that these compositions are azeotropic or
azeotrope-like because when 50 wt. % of an original composition is
removed, the vapor pressure of the remaining composition is within about
10% of the vapor pressure of the original composition except for
32/125/N.sub.2 O/ethane and 32/125/134a/N.sub.2 O which are zeotropic.
EXAMPLE 3
Impact of Vapor Leakage at 25.degree. C.
A leak test is performed on compositions of 23 and N.sub.2 O, at the
temperature of 25.degree. C. The results are summarized below.
Refrigerant 0 wt % evaporated 50 wt % evaporated 0% change in
Composition psia kPa psia kPa vapor pressure
23/N.sub.2 O
1/99 772.1 5323 771.4 5319 0.1
10/90 785.5 5416 784.2 5407 0.2
24.1/75.9 791.5 5457 791.5 5457 0.0
4O/60 785.4 5415 783.6 5403 0.2
60/40 762.0 5254 755.8 5211 0.8
80/20 721.6 4975 714.5 4926 1.0
99/1 668.6 4610 668.0 4606 0.1
These results show that compositions of HFC-23 and N.sub.2 O are azeotropic
or azeotrope-like at different temperatures, but that the weight percents
of the components vary as the temperature is changed.
EXAMPLE 4
13B1 Alternative
Refrigerant Performance
The following table shows the performance of various refrigerants in an
ideal vapor compression cycle. The data are based on the following
conditions.
Condenser=100.degree. F. (37.8.degree. C.)
Evaporator=-40.degree. F. (-40.0.degree. C.)
Subcooled=15.degree. F. (8.3.degree. C.)
Return Gas=-10.degree. F. (-23.3.degree. C.)
Clearance Volume=3%
Efficiency=70%
The refrigeration capacity is based on a compressor with a fixed
displacement of 3.5 cubic feet per minute and 70% volumetric efficiency.
Capacity is intended to mean the change in enthalpy of the refrigerant in
the evaporator per pound of refrigerant circulated, i.e. the heat removed
by the refrigerant in the evaporator per time. Coefficient of performance
(COP) is intended to mean the ratio of the capacity to compressor work. It
is a measure of refrigerant energy efficiency.
TABLE 1
Compressor Compressor Capacity
Discharge Discharge Btu/
Temp (.degree. F., .degree. C.) Psia kPa COP min kW
13B1 207 97 314 2165 1.75 70.5 1.2
HFC-32/HFC-125 269 131 335 2310 1.90 72.1 1.3
(50/50 wt %)
HFC-32/HFC- 231 111 349 2406 1.82 67.8 1.2
125/N.sub.2 O
(27/70/3 wt %)
HFC-32/HFC- 223 106 355 2448 1.76 64.1 1.1
125/N.sub.2 O/Ethane
(22/75/2/1 wt %)
The data in Table 1 show that the HFC-32/HFC-125/N.sub.2 O composition and
the HFC-32/HFC-125/N.sub.2 O/ethane composition provide a compressor
discharge temperature closer to 13B1 (bromotrifluoromethane) than
HFC-32/HFC-125. The discharge temperature can be effectively lowered while
improving energy efficiency (COP) versus 13B1.
EXAMPLE 5
R-503 Alternative
Condenser=-26.degree. F. (-32.degree. C.)
Evaporator=-112.degree. F. (-80.degree. C.)
No Subcool
Superheated=54.degree. F. (30.degree. C.)
Clearance Volume=3%
Efficiency=70%
TABLE 2
Compressor Compressor
Discharge Discharge Capacity
Temp (.degree. F., .degree. C.) Psia kPa COP
Btu/min kW
R-503 139 59.4 159 1096 2.62 75 1.3
HFC-23/HFC-116 107 41.7 161 1110 2.53 70 1.2
(46/54 wt %)
HFC-23/HFC-116/N.sub.2 O
(38/52/10 wt %) 118 47.8 183 1262 2.55 82 1.4
(42/50/8 wt %) 120 48.9 178 1227 2.54 79 1.4
HFC-23/N.sub.2 O 244 118 177 1220 2.67 91 1.6
(15.3/84/7 wt %)
N.sub.2 O/Ethane 202 94.4 119 1373 2.65 107 1.9
(75.1/24.9 wt %)
The data in Table 2 show that addition of N.sub.2 O to HFC-23/HFC-116
compositions significantly increases capacity and provides better
efficiency than HFC-23 and HFC-116 while maintaining compressor discharge
temperature below R-503. R-503 is an azeotropic mix of 40 wt % HFC-23 and
60 wt % R-13 (chlorotrifluoromethane).
EXAMPLE 6
High Pressure HCFC-22 Alternative
Refrigerant Performance
The following table shows the performance of refrigerants of the present
invention in a high efficiency vapor compression system. The data show
system performance using cross-flow and countercurrent-flow heat
exchangers with a zeotropic mixture of the present invention containing 32
weight percent HFC-32, 18 weight percent HFC-125, 42 weight percent
HFC-134a and 8 weight percent nitrous oxide (N.sub.2 O). The N.sub.2 O
containing zeotropic mixture is compared to a leading high pressure
HCFC-22 alternative, an azeotropic mixture of 50 weight percent HFC-32 and
50 weight percent HFC-125.
For the test conditions, all heat exchangers have equal UA, equal air
flows, and 5 psia pressure drop. Initial conditions for the condenser and
evaporator are 47.8.degree. C. (118.degree. F.) and 8.9.degree. C.
(48.degree. F.) respectively. For a countercurrent flow system, the
condenser temperature is effectively reduced by 0.5.degree. C. and the
evaporator temperature is effectively increased by 1.6.degree. C. when
operating with the zeotropic mixture. Other system conditions include no
subcool, no superheat, and a fixed compressor displacement of 0.1 m.sup.3
/min.
Results for HFC-32/HFC-125 using typical cross-flow heat exchangers and
HFC-32/HFC-125/HFC-134a/N.sub.2 O using cross-flow and counter-flow heat
exchangers are shown in Table 3.
TABLE 3
HFC-32/ HFC-32/HFC-125/
HFC-125 HFC-134a/N.sub.2 O
(50/50 wt %) (32/18/42/8 wt %)
Cross-flow Cross-flow Counter-flow
Discharge temperature (.degree. C.) 77.3 85.6 83.5
Condenser average 47.8 47.8 47.3
temperature (.degree. C.)
Condenser pressure (kPa) 2925 2700 2670
Liquid temperature (.degree. C.) 47.8 42.8 42.3
Evaporator average temp. 8.9 8.9 10.5
(.degree. C.)
Evaporator pressure (kPa) 1065 879 926
Suction temperature 8.9 12.9 14.6
Condenser delta T (.degree. C.) 0.10 10.7 10.8
Evaporator delta T (.degree. C.) 0.04 9.1 9.3
Cooling Load, W 8770 8033 8607
Isentropic COP 4.99 5.03 5.40
The data in Table 3 show that taking advantage of the increased temperature
glide (Delta T) of the zeotropic N.sub.2 O mixture with
countercurrent-flow heat exchangers significantly increases system
efficiency (COP) while providing equivalent capacity (within 2%) versus
HFC-32/HFC-125. Evaporator and condenser pressures are also significantly
reduced versus HFC-32/HFC-125.
ADDITIONAL COMPOUNDS
Other components, such as aliphatic hydrocarbons having a boiling point of
-100 to +60.degree. C., hydrofluorocarbonalkanes having a boiling point of
-100 to +60.degree. C., hydrofluoropropanes having aboiling point of
between -100 to +60.degree. C., hydrocarbon ethers having a boiling point
between -100 to +60.degree. C., hydrochlorofluorocarbons having a boiling
point between -100 to +60.degree. C., hydrofluorocarbons having a boiling
point of -100 to +60.degree. C., hydrochlorocarbons having a boiling point
between -100 to +60.degree. C., chlorocarbons, inorganics and
perfluorinated compounds, can be added to the azeotropic, azeotrope-like,
zeotropic compositions described above without substantially changing the
properties thereof.
Additives such as lubricants, surfactants, corrosion inhibitors,
stabilizers, dyes and other appropriate materials may be added to the
novel compositions of the invention for a variety of purposes provides
they do not have an adverse influence on the composition for its intended
application. Preferred lubricants include esters having a molecular weight
greater than 250.
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