U.S. patent application number 09/562154 was filed with the patent office on 2002-01-03 for non-azeotropic refrigerant compositions comprising difluoromethane or 1,1,1,-trifluorethane.
Invention is credited to Nieuwstadt, Michiel Jacques Van, Richard, Robert G, Shankland, Ian Robert, Singh, Rajiv Ratna.
Application Number | 20020000534 09/562154 |
Document ID | / |
Family ID | 21799876 |
Filed Date | 2002-01-03 |
United States Patent
Application |
20020000534 |
Kind Code |
A1 |
Richard, Robert G ; et
al. |
January 3, 2002 |
Non-azeotropic refrigerant compositions comprising difluoromethane
or 1,1,1,-trifluorethane
Abstract
The present invention provides refrigerant blends which are
replacements for chlorodifluoromethane(HCFC-22). The present blends
have refrigeration characteristics which are similar to HCFC-22.
The blends comprise from about 10 to about 90 weight percent of a
first component selected from the group consisting of
1,1,1-trifluoroethane, difluoromethane, propane, and mixtures
thereof; from about 1 to about 50 weight percent of a second
component selected from the group consisting of hydrofluorocarbon
having 1 to 3 carbon atoms, fluorocarbon having 1 to 3 carbon
atoms, inorganic compound, and mixtures thereof having a boiling
point at atmospheric pressure in the range from about -90 degrees
C. to less than -50 degrees C.; and from about 1 to about 50 weight
percent of a third component which is hydrofluorocarbon having 1 to
3 carbon atoms, other than 1,1,1-trifluoroethane, having a boiling
point at atmospheric pressure in the range from about -50 degrees
C. to about -10 degrees C. The refrigerant compositions have a
vapor pressure substantially equal to the vapor pressure of
HCFC-22.
Inventors: |
Richard, Robert G; (Erie
County, NY) ; Shankland, Ian Robert; (Morris County,
NY) ; Singh, Rajiv Ratna; (Erie County, NY) ;
Nieuwstadt, Michiel Jacques Van; (Ann Arbor, MI) |
Correspondence
Address: |
Marie L Collazo
AlliedSignal Inc
P O Box 2245
101 Columbia Road
Morristown
NJ
07962
US
|
Family ID: |
21799876 |
Appl. No.: |
09/562154 |
Filed: |
May 1, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09562154 |
May 1, 2000 |
|
|
|
09020662 |
Feb 9, 1998 |
|
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Current U.S.
Class: |
252/69 ;
252/67 |
Current CPC
Class: |
C09K 5/045 20130101;
C09K 2205/43 20130101; C09K 2205/22 20130101; C09K 2205/34
20130101 |
Class at
Publication: |
252/69 ;
252/67 |
International
Class: |
C09K 005/00; C10M
101/00; F25D 001/00 |
Claims
What is claimed is
1. Refrigerant compositions comprising from about 10 to about 90
weight percent of a first component selected from the group
consisting of 1,1,1-trifluoroethane, difluoromethane, propane, and
mixtures thereof; from about 1 to about 50 weight percent of a
second component selected from the group consisting of
hydrofluorocarbon having 1 to 3 carbon atoms, fluorocarbon having 1
to 3 carbon atoms, inorganic compound, and mixtures thereof having
a boiling point at atmospheric pressure in the range from about -90
degrees C. to less than -50 degrees C.; and from about 1 to about
50 weight percent of a third component which is hydrofluorocarbon
having 1 to 3 carbon atoms, other than 1,1,1-trifluoroethane,
having a boiling point at atmospheric pressure in the range from
about -50 degrees C. to about -10 degrees C. wherein said
refrigerant compositions have a vapor pressure substantially equal
to the vapor pressure of chlorodifluoromethane.
2. The refrigerant compositions of claim 1 wherein said first,
second, and third components and their weight percents are selected
so that the resulting refrigerant compositions are
nonflammable.
3. The refrigerant compositions of claim 1 comprising from about 20
to about 80 weight percent said first component, from about 2 to
about 40 weight percent said second component, and from about 2 to
about 40 weight percent said third component.
4. The refrigerant compositions of claim 1 wherein said first
component is 1,1,1-trifluoroethane.
5. The refrigerant compositions of claim 4 wherein said second
component is selected from the group consisting of
trifluoromethane, hexafluoroethane, carbon dioxide, and sulfur
hexafluoride.
6. The refrigerant compositions of claim 4 wherein said third
component is selected from the group consisting of
pentafluoroethane, 1,1,2,2-tetrafluoroethane,
1,1,1,2-tetrafluoroethane, 1,1,1,2,3,3,3-heptafluoropropane,
1,1,1,2,2,3,3-heptafluoropropane, and
1,1,1,2,2-pentafluoropropane.
7. The refrigerant compositions of claim 1 wherein said first
component is difluoromethane.
8. The refrigerant compositions of claim 7 wherein said second
component is selected from the group consisting of
trifluoromethane, hexafluoroethane, carbon dioxide, and sulfur
hexafluoride.
9. The refrigerant compositions of claim 7 wherein said third
component is selected from the group consisting of
pentafluoroethane, 1,1,2,2-tetrafluoroethane,
1,1,1,2-tetrafluoroethane, 1,1,1,2,3,3,3-heptafluoropropane,
1,1,1,2,2,3,3-heptafluoropropane, and
1,1,1,2,2-pentafluoropropane.
10. The refrigerant compositions of claim 1 wherein said first
component is difluoromethane, said second component is
trifluoromethane, and said third component is
1,1,1,2-tetrafluoroethane.
11. The refrigerant compositions of claim 1 wherein said first
component is propane.
12. The refrigerant compositions of claim 11 wherein said second
component is selected from the group consisting of
trifluoromethane, hexafluoroethane, carbon dioxide, and sulfur
hexafluoride.
13. The refrigerant compositions of claim 11 wherein said third
component is selected from the group consisting of
pentafluoroethane, 1,1,2,2-tetrafluoroethane,
1,1,1,2-tetrafluoroethane, 1,1,1,2,3,3,3-heptafluoropropane,
1,1,1,2,2,3,3-heptafluoropropane, and
1,1,1,2,2-pentafluoropropane.
14. A method for producing refrigeration which comprises condensing
said refrigerant compositions of claim 1 and thereafter evaporating
said refrigerant compositions in the vicinity of the body to be
cooled.
15. A method for producing refrigeration which comprises condensing
said refrigerant compositions of claim 4 and thereafter evaporating
said refrigerant compositions in the vicinity of the body to be
cooled.
16. A method for producing refrigeration which comprises condensing
said refrigerant compositions of claim 7 and thereafter evaporating
said refrigerant compositions in the vicinity of the body to be
cooled.
17. A method for producing refrigeration which comprises condensing
said refrigerant compositions of claim 11 and thereafter
evaporating said refrigerant compositions in the vicinity of the
body to be cooled.
18. A method for producing heating which comprises condensing said
refrigerant compositions of claim 1 in the vicinity of the body to
be heated and thereafter evaporating said refrigerant
compositions.
19. A method for producing heating which comprises condensing said
refrigerant compositions of claim 4 in the vicinity of the body to
be heated and thereafter evaporating said refrigerant
compositions.
20. A method for producing heating which comprises condensing said
refrigerant compositions of claim 7 in the vicinity of the body to
be heated and thereafter evaporating said refrigerant compositions.
Description
FIELD OF THE INVENTION
[0001] This invention relates to novel nonazeotropic compositions
containing difluoromethane; 1,1,1-trifluoroethane; or propane.
These mixtures have improved efficiency and capacity as
refrigerants for heating and cooling.
BACKGROUND OF THE INVENTION
[0002] Fluorocarbon based fluids have found widespread use in
industry for refrigeration, air conditioning and heat pump
applications. Vapor compressions cycles are one form of
refrigeration. In its simplest form, the vapor compression cycle
involves changing the refrigerant from the liquid to the vapor
phase through heat absorption at a low pressure, and then from the
vapor to the liquid phase through heat removal at an elevated
pressure. First, the refrigerant is vaporized in the evaporator
which is in contact with the body to be cooled. The pressure in the
evaporator is such that the boiling point of the refrigerant is
below the temperature of the body to be cooled. Thus, heat flows
from the body to the refrigerant and causes the refrigerant to
vaporize. The formed vapor is then removed by means of a compressor
in order to maintain the low pressure in the evaporator. The
temperature and pressure of the vapor are then raised through the
addition of mechanical energy by the compressor. The high pressure
vapor then passes to the condenser whereupon heat exchange with a
cooler medium, the sensible and latent heats are removed with
subsequent condensation. The hot liquid refrigerant then passes to
the expansion valve and is ready to cycle again.
[0003] While the primary purpose of refrigeration is to remove
energy at low temperature, the primary purpose of a heat pump is to
add energy at higher temperature. Heat pumps are considered reverse
cycle systems because for heating, the operation of the condenser
is interchanged with that of the refrigeration evaporator.
[0004] Certain chlorofluorocarbons have gained widespread use in
refrigeration applications including air conditioning and heat pump
applications owing to their unique combination of chemical and
physical properties. The majority of refrigerants utilized in vapor
compression systems are either single component fluids or
azeotropic mixtures.
[0005] The majority of refrigerants utilized in vapor compression
systems are either single component fluids or azeotropic mixtures.
The latter are binary mixtures, but for all refrigeration purposes
behave as single component fluids. Nonazeotropic mixtures have been
disclosed as refrigerants for example in U.S. Pat. Nos. 4,303,536
and 4,810,403 but have not yet found widespread use in commercial
applications.
[0006] The condensation and evaporation temperatures of single
component fluids are defined clearly. If we ignore the small
pressure drops in the refrigerant lines, the condensation or
evaporation occurs at a single temperature corresponding to the
condenser or evaporation pressure. For mixtures being employed as
refrigerants, there is no single phase change temperature but a
range of temperatures. This range is governed by the vapor-liquid
equilibrium behavior of the mixture. This property of mixtures is
responsible for the fact that when nonazeotropic mixtures are used
in the refrigeration cycle, the temperature in the condenser or the
evaporator has no longer a single uniform value, even if the
pressure drop effect is ignored. Instead, the temperature varies
across the equipment, regardless of the pressure drop. In the art,
this variation in the temperature across an equipment is known as
temperature glide.
[0007] It has been pointed out in the past that for non-isothermal
heat sources and heat sinks, this temperature glide in mixtures can
be utilized to provide better efficiencies. However in order to
benefit from this effect, the conventional refrigeration cycle has
to be redesigned, see for example T. Atwood, "NARBs-The Promise and
the Problem", paper 86-WA/HT-61 American Society of Mechanical
Engineers. In most existing designs of refrigeration equipment, a
temperature glide is a cause of concern. Therefore, nonazeotropic
refrigerant mixtures have not found wide use. An environmentally
acceptable nonazeotropic mixture with a small temperature glide and
with an advantage in refrigeration capacity over other known pure
fluids will have a general commercial interest.
[0008] Chlorodifluoromethane (HCFC-22) is a currently used
refrigerant. Although HCFC-22 is only partially halogenated, it
still contains chlorine and hence has a propensity for ozone
depletion. What is needed in the refrigerant art is a replacement
for HCFC-22 which has similar refrigeration characteristics, is
nonflammable, has low temperature guides, and contains no
ozone-depleting chlorine atoms.
[0009] U.S. Pat. No. 4,810,403 teaches ternary or higher blends of
halocarbon refrigerants which are substitutes for
dichlorodifluoromethane (CFC-12). The blends have a first component
which has a boiling point at atmospheric pressure in the range of
-50 degrees C. to -30 degrees C., a second component which has a
boiling point at atmospheric pressure in the range of -30 degrees
C. to -5 degrees C., and a third component which has a boiling
point at atmospheric pressure in the range of -15 degrees C. to 30
degrees C. The preferred blend contains chlorodifluoromethane
(HCFC-22), 1,1-difluoroethane (HFC-152a), and
1,2-dichloro-1,1,2,2-tetraf- luoroethane (CFC-114). As the
reference lists HCFC-22 as a possible refrigerant component, the
reference is not teaching refrigerant substitutes for HCFC-22.
[0010] As such, the art is seeking new fluorocarbon based mixtures
which offer alternatives for HCFC-22 in refrigeration and heat pump
applications. Currently, of particular interest, are fluorocarbon
based mixtures which are considered to be environmentally
acceptable substitutes for the presently used
hydrochlorofluorocarbons which are suspected of causing
environmental problems in connection with the earth's protective
ozone layer. Mathematical models have substantiated that
hydrofluorocarbons, such as 1,1,1-trifluoroethane (HFC-143a) or
difluoromethane (HFC-32) will not adversely affect atmospheric
chemistry, being negligible contributors to stratospheric ozone
depletion and global warming.
[0011] The substitute materials must also possess those properties
unique to the CFC's including chemical stability, low toxicity,
non-flammability, and efficiency in-use. The latter characteristic
is important, for example, in air conditioning and refrigeration
where a loss in refrigerant thermodynamic performance or energy
efficiency may have secondary environmental impacts through
increased fossil fuel usage arising from an increased demand for
electrical energy.
[0012] The aforementioned environmentally acceptable refrigerants
HFC-32 and HFC-143a are flammable which may limit their general
use. These refrigerants are generally regarded as too low boiling
fluids to directly replace chlorodifluoromethane (HCFC-22).
[0013] In order to overcome the flammability of HFC-32, we blended
HFC-32 with 1,1,1,2-tetrafluoroethane (HFC-134a) and the result was
zero ozone depletion potential compositions which are useful
substitutes for HCFC-22. At high amounts of HFC-32 though,
compositions of HFC-32 and HFC-134a are flammable. In order to
completely eliminate the flammability of such compositions, we
decided to add a third nonflammable component. In adding a third
component, we wanted the resulting ternary composition to have a
zero ozone depletion potential and have a boiling point comparable
to that of HCFC-22. One member from the list of compounds having
zero ozone depletion potential and boiling points at atmospheric
pressure in the range of -90 degrees C. to -60 degrees C. is
trifluoromethane (HFC-23) which has a low critical temperature; as
those skilled in the art know, compounds having low critical
temperatures are not used as refrigerants because they do not
condense at room temperature and in a refrigerant blend, would be
expected to substantially reduce the refrigeration efficiency and
capacity of the blend. We were pleasantly surprised to find that in
addition to being nonflammable, a blend of HFC-32, HFC-134a, and
HFC-23 has refrigeration efficiency and capacity substantially the
same as a blend of HFC-32 and HFC-134a.
SUMMARY OF THE INVENTION
[0014] Thus, we have discovered refrigerant blends which are
substitutes for HCFC-22. These nonazeotropic refrigerant
compositions comprise from about 10 to about 90 weight percent of a
first component selected from the group consisting of
1,1,1-trifluoroethane (HFC-143a), difluoromethane (HFC-32),
propane, and mixtures thereof; from about 1 to about 50 weight
percent of a second component selected from the group consisting of
hydrofluorocarbon having 1 to 3 carbon atoms, fluorocarbon having 1
to 3 carbon atoms, inorganic compound, and mixtures thereof having
a boiling point at atmospheric pressure in the range from about -90
degrees C. to less than -50 degrees C.; and from about 1 to about
50 weight percent of a third component which is hydrofluorocarbon
having 1 to 3 carbon atoms, other than 1,1,1-trifluoroethane,
having a boiling point at atmospheric pressure in the range from
about -50 degrees C. to about -10 degrees C. The refrigerant
compositions have a vapor pressure substantially equal to the vapor
pressure of HCFC-22.
[0015] The term "hydrofluorocarbon" as used herein means a compound
having carbon, hydrogen, and fluorine atoms. The term
"fluorocarbon" as used herein means a compound having carbon and
fluorine atoms. For the second component, any hydrofluorocarbon
having 1 to 3 carbon atoms, fluorocarbon having 1 to 3 carbon
atoms, or inorganic compound having a boiling point at atmospheric
pressure in the range from about -90 degrees C. to less than -50
degrees C. may be used in the present invention. For the third
component, any hydrofluorocarbon having 1 to 3 carbon atoms, other
than 1,1,1-trifluoroethane, having a boiling point at atmospheric
pressure in the range from about -50 degrees C. to about -10
degrees C. may be used in the present invention.
[0016] The preferred first component is difluoromethane.
[0017] Preferably, the second component is selected from the group
consisting of: trifluoromethane (HFC-23), hexafluoroethane
(FC-116), carbon dioxide or sulphur hexafluoride. The preferred
second component is trifluoromethane. All members listed for the
second component are nonflammable and generally boil at a
temperature below that of HFC-32 or HFC-143a.
[0018] Preferably, the third component is selected from the group
consisting of: pentafluoroethane (HFC-125),
1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane
(HFC-134a), 1,1,1,2,3,3,3-heptafluor- opropane (HFC-227ea),
1,1,1,2,2,3,3-heptafluoropropane (HFC-227ca), or
1,1,1,2,2-pentafluoropropane (HFC-245cb). The preferred third
component is 1,1,1,2-tetrafluoroethane. All members listed for the
third component are nonflammable and generally boil at a
temperature above that of HFC-32 or HFC-143a.
[0019] Small quantities of HFC-227ea, HFC-227ca, and HFC-245cb are
available from PCR and Halocarbon Products. All other components of
the present invention are available in commercial quantities. Also,
HFC-227ea, HFC-227ca, and HFC-245cb may be prepared according to
known methods such as those disclosed in International Publication
Number WO 90/08754. For example, HFC-227ca may be prepared by
reacting 1,1,1,3,3-pentachloro-2,2-difluoropropane with niobium
pentachloride at 120 degrees C. HFC-245cb may be prepared by
reacting 1,1,1,2,2-pentachloropropane with tantalum pentafluoride
at 120 degrees C.
[0020] By "vapor pressure substantially equal to the vapor pressure
of chlorodifluoromethane" or "similar refrigeration
characteristics" is meant a vapor pressure which is plus or minus
30 percent of the vapor pressure of HCFC-22 at the same temperature
over the temperature range of about 0 degrees C. to about 100
degrees C.
[0021] Additional components may be added to the mixture to tailor
the properties of the mixture according to the need.
[0022] Other advantages of the invention will become apparent from
the following description.
DESCRIPTION OF THE DRAWING
[0023] The FIGURE illustrates nonflammable compositions of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The properties of the preferred components of the present
invention are listed in Table 1 below. BP in Table 1 stands for
Boiling Point while CT stands for Critical Temperature. The * in
Table 1 means sublimes at one atm pressure and the boiling point is
the triple point.
1TABLE 1 No. Formula BP (degrees C.) CT (degrees C.) HFC-32
CH.sub.2F.sub.2 -51.7 78.4 HFC-143a CF.sub.3CH.sub.3 -47.6 73.1
Propane C.sub.3H.sub.8 -42.1 96.7 HFC-23 CHF.sub.3 -82.1 25.9
FC-116 C.sub.2F.sub.6 -78.1 24.3 -- CO.sub.2* -78.5 31.3 --
SF.sub.6 -64.0 45.5 HFC-125 C.sub.2HF.sub.5 -48.5 66.3 HFC-134
CHF.sub.2CHF.sub.2 -19.7 118.9 HFC-134a CF.sub.3CH.sub.2F -26.5
101.1 HFC-227ea CF.sub.3CFHCF.sub.3 -16.5 102.0 HFC-227ca
CF.sub.3CF.sub.2CHF.sub.2 -15.6 104.7 HFC-245cb
CF.sub.3CF.sub.2CH.sub.3 -17.5 107.0
[0025] The most preferred composition comprises difluoromethane,
trifluoromethane, and 1,1,1,2-tetrafluoroethane.
[0026] In a preferred embodiment of the invention, the compositions
comprise from about 20 to about 80 weight percent of the first
component, from about 2 to about 40 weight percent of the second
component, and from about 2 to about 40 weight percent of the third
component.
[0027] In one process embodiment of the invention, the compositions
of the invention may be used in a method for producing
refrigeration which involves condensing a refrigerant comprising
the compositions and thereafter evaporating the refrigerant in the
vicinity of the body to be cooled.
[0028] In another process embodiment of the invention, the
compositions of the invention may be used in a method for producing
heating which involves condensing a refrigerant comprising the
compositions in the vicinity of the body to be heated and
thereafter evaporating the refrigerant.
[0029] Preferably the components used should be of sufficiently
high purity so as to avoid the introduction of adverse influences
upon the properties of the system.
[0030] As mentioned above, when a refrigerant composition contains
a flammable component like HFC-32, HFC-143a, or propane, the
possibility of either the leaking vapor or the remaining liquid
becoming flammable is a very undesirable hazard. We have discovered
that the claimed compositions of the refrigerant blends containing
either HFC-32, HFC-143a, or propane can be so formulated with the
components from the two nonflammable groups that the original
composition is nonflammable and the leaking vapor as well as the
remaining liquid never become flammable.
[0031] The present invention comprises ternary and higher blends
based either on HFC-32, HFC-143a, or propane that have a vapor
pressure substantially the same as the vapor pressure of HCFC-22
and which retain this relationship even after substantial
evaporation losses, e.g. up to 50 percent by weight. A vapor
pressure temperature relationship similar to HCFC-22 is especially
desirable because it will need minimum amount of modifications in
the present refrigeration equipment which is designed around the
vapor pressure temperature relationship of the HCFC-22.
[0032] It should be understood that the present compositions may
include additional components so as to form new compositions. Any
such compositions are considered to be within the scope of the
present invention as long as the compositions have essentially the
same characteristics and contain all the essential components
described herein.
[0033] The present invention is more fully illustrated by the
following non-limiting Examples.
EXAMPLES 1-72
[0034] The compositions in Table 2 below are made and exhibit
refrigeration characteristics similar to HCFC-22, have low
temperature guides, and contain no chlorine atoms. Comp 1 stands
for the first component, Comp 2 stands for the second component,
and Comp 3 stands for the third component.
2TABLE 2 EX COMP 1 COMP 2 COMP 3 1 HFC-143a HFC-23 HFC-125 2
HFC-143a FC-116 HFC-125 3 HFC-143a CO.sub.2 HFC-125 4 HFC-143a
SF.sub.6 HFC-125 5 HFC-143a HFC-23 HFC-134 6 HFC-143a FC-116
HFC-134 7 HFC-143a CO.sub.2 HFC-134 8 HFC-143a SF.sub.6 HFC-134 9
HFC-143a HFC-23 HFC-134a 10 HFC-143a FC-116 HFC-134a 11 HFC-143a
CO.sub.2 HFC-134a 12 HFC-143a SF.sub.6 HFC-134a 13 HFC-143a HFC-23
HFC-227ea 14 HFC-143a FC-116 HFC-227ea 15 HFC-143a CO.sub.2
HFC-227ea 16 HFC-143a SF.sub.6 HFC-227ea 17 HFC-143a HFC-23
HFC-227ca 18 HFC-143a FC-116 HFC-227ca 19 HFC-143a CO.sub.2
HFC-227ca 20 HFC-143a SF.sub.6 HFC-227ca 21 HFC-143a HFC-23
HFC-245cb 22 HFC-143a FC-116 HFC-245cb 23 HFC-143a CO.sub.2
HFC-245cb 24 HFC-143a SF.sub.6 HFC-245cb 25 HFC-32 HFC-23 HFC-125
26 HFC-32 FC-116 HFC-125 27 HFC-32 CO.sub.2 HFC-125 28 HFC-32
SF.sub.6 HFC-125 29 HFC-32 HFC-23 HFC-134 30 HFC-32 FC-116 HFC-134
31 HFC-32 CO.sub.2 HFC-134 32 HFC-32 SF.sub.6 HFC-134 33 HFC-32
HFC-23 HFC-134a 34 HFC-32 FC-116 HFC-134a 35 HFC-32 CO.sub.2
HFC-134a 36 HFC-32 SF.sub.6 HFC-134a 37 HFC-32 HFC-23 HFC-227ea 38
HFC-32 FC-116 HFC-227ea 39 HFC-32 CO.sub.2 HFC-227ea 40 HFC-32
SF.sub.6 HFC-227ea 41 HFC-32 HFC-23 HFC-227ca 42 HFC-32 FC-116
HFC-227ca 43 HFC-32 CO.sub.2 HFC-227ca 44 HFC-32 SF.sub.6 HFC-227ca
45 HFC-32 HFC-23 HFC-245cb 46 HFC-32 FC-116 HFC-245cb 47 HFC-32
CO.sub.2 HFC-245cb 48 HFC-32 SF.sub.6 HFC-245cb 49 Propane HFC-23
HFC-125 50 Propane FC-116 HFC-125 51 Propane CO.sub.2 HFC-125 52
Propane SF.sub.6 HFC-125 53 Propane HFC-23 HFC-134 54 Propane
FC-116 HFC-134 55 Propane CO.sub.2 HFC-134 56 Propane SF.sub.6
HFC-134 57 Propane HFC-23 HFC-134a 58 Propane FC-116 HFC-134a 59
Propane CO.sub.2 HFC-134a 60 Propane SF.sub.6 HFC-134a 61 Propane
HFC-23 HFC-227ea 62 Propane FC-116 HFC-227ea 63 Propane CO.sub.2
HFC-227ea 64 Propane SF.sub.6 HFC-227ea 65 Propane HFC-23 HFC-227ca
66 Propane FC-116 HFC-227ca 67 Propane CO.sub.2 HFC-227ca 68
Propane SF.sub.6 HFC-227ca 69 Propane HFC-23 HFC-245cb 70 Propane
FC-116 HFC-245cb 71 Propane CO.sub.2 HFC-245cb 72 Propane SF.sub.6
HFC-245cb
EXAMPLE 73
[0035] The example shows that it is possible to calculate the
thermodynamic properties of a ternary mixture from using equation
of state techniques. These are important for estimating theoretical
performance of a refrigerant as discussed in Example 75. The
equation of state package used was based on the NIST Mixture
Properties formalism (DDMIX) available from the National Institute
of Standards and Technology, Gaithersberg, Md. 20899. An example of
measured and calculated bubble pressures of a 48.1 wt % HFC-23,
19.3 wt % HFC-32, and 32.6 wt % HFC-134a ternary nonazeotropic
blend is shown in Table 3. The very good agreement shows the high
degree of confidence that may be placed in the results of the
experiments and the theory.
3TABLE 3 Bubble Pressure Bubble Pressure Temperature/K exptl., psia
calcd., psia 263.54 154.2 151.8 268.49 176.4 174.8 278.38 230.0
228.2 288.09 293.4 290.9 298.08 367.9 366.9 308.09 453.4 455.3
318.12 550.7 556.1
EXAMPLE 74
[0036] By preparing various compositions of HFC-134a/HFC-32/HFC-23
in air and determining their flammability, it is possible to map
out the region of compositions in air that are flammable. See, e.g.
P. A. Sanders, The Handbook of Aerosol Technology at 146 (2d ed.
1979). The maximum amount of HFC-32 that can be blended with
HFC-134a and HFC-23 and remain nonflammable in all proportions in
air, can be determined from such a plot. Table 4 summaries the
maximum or critical composition of HFC-32 attainable with HFC-134a
and a higher pressure component (e.g. HFC-23, HF-116, SF.sub.6, and
CO.sub.2) for the binary mixtures. The CFR is the critical
flammability ratio: which is the maximum amount of HFC-32 that a
mixture of HFC-32/X can contain and still be nonflammable in all
proportions in air. X represents the higher pressure components
listed in Table 4. These binary flammability data can be used to
predict the flammability of the more complex ternary mixture plus
air. This complex mixture of three components and air does not lend
itself to simple ternary diagrams. Therefore, air is not included
so that we are able to show the data graphically. The air
proportion itself is not important just whether or not the mixture
is flammable in some proportion with air. FIG. 1 shows a
composition of HCFC-134a, HFC-32, and HFC-23. Above the line
A-B(more HFC-32), mixtures of those compositions are flammable in
some proportion in air while below line A-B(less HFC-32), mixtures
of those compositions are not flammable in air at any proportion of
air. Further this diagram depicts compositions that will remain
nonflammable in the event of a vapor leak. If the leak is from the
liquid phase, some liquid will vaporize to fill the space vacated
by the leaking liquid. Because the vapor is {fraction (1/25)}th as
dense as the liquid, and very little vaporization occurs,
therefore, very little fractionation occurs. In contrast, when the
vapor phase is removed, all the liquid is eventually vaporized,
producing a dramatic amount of fractionation. Liquid leaks produce
only minor changes in the composition of the mixture. As such, a
liquid leak is not problematic and only the case of a vapor leak
must be considered.
[0037] Shifts in the compositions of the vapor and liquid phases
during leaking were calculated using ideal solution behavior. These
types of calculations were used to determine what starting
compositions would remain nonflammable on evaporation. Line D-C in
FIG. 1 separates those compositions that could have flammable
liquid phase compositions from those compositions that would remain
nonflammable. Compositions rich in HFC-134a (right of the line)
would have liquid phase compositions that remain nonflammable on
evaporation. Line C-E separates composition that would fractionate
given vapors that are flammable from those that would not produce
flammable vapors. Compositions having more, HFC-23 (left of the
line) would remain nonflammable vapors on segregation. Therefore,
compositions below line D-C-E would not fractionate to produce
either liquid or vapor phases that could be flammable.
4TABLE 4 Maximum HFC-32 Compo % air at CFR Gas in HFC-32 (mole or
volume %) (mole or volume %) HFC-134a 72.9 20 HFC-23 75.3 19
HFC-116 88.1 20 SF.sub.6 87.9 21 CO.sub.2 55.2 29
EXAMPLE 75
[0038] This example shows that a HFC-32 containing blend has a
performance similar to HCFC-22, yet is nonflammable even after
substantial vapor leakage.
[0039] The theoretical performance of a refrigerant at specific
operating conditions can be estimated from the thermodynamic
properties of the refrigerant using standard refrigeration cycle
analysis techniques, see for example, "Fluorocarbons Refrigerants
Handbook", Ch. 3, Prentice-Hall, (1988), by R. C. Downing. The
coefficient of performance, COP, is a universally accepted measure,
especially useful in representing the relative thermodynamic
efficiency of a refrigerant in a specific heating or cooling cycle
involving evaporation or condensation of refrigerant. In
refrigeration engineering, this term expresses the ratio of useful
refrigeration to the energy applied by the compressor in
compressing the vapor. The capacity of a refrigerant represents the
volumetric efficiency of the refrigerant. To a compressor engineer,
this value expresses the capability of a compressor to pump
quantities of heat for a given volumetric flow rate of refrigerant.
In other words, given a specific compressor, a refrigerant with a
higher capacity will deliver more cooling or heating power. A
similar calculation can also be performed for nonazeotropic
refrigerant blends.
[0040] We have performed this type of calculation for packaged air
conditioning cycle where the condenser temperature is typically
115.degree. F. and the evaporator temperature is typically
40.degree. F. We have further assumed isentropic compression and a
compressor inlet temperature of 60.degree. F. Such calculations
were performed for a 0.72/28.71/70.57 by weight blend of HFC-23,
HFC-32, and HFC-134a. The temperature glide in typical HCFC-22
application in no case exceeded 15.degree. F. The coefficient of
performance (COP), a measure of energy efficiency of the fluid, was
found to be 5.36 as compared to 5.51 found for HCFC-22 in the same
conditions. According to the known art (D. A. Didion and D. M.
Bivens "The Role of Refrigerant Mixtures as Alternatives" in CFC's:
Today's Options. . . . Tomorrow's Solutions, NIST, 1990), the
temperature glides of the order of 10.degree. F. are minor enough
for the mixture to be termed Near-Azeotropic. Therefore, the
temperature glide of the mixture composition claimed is small
enough and does not pose a problem for conventional refrigeration
units. As can be seen from the attached FIG. 1, which gives the
flammability limits of the three component blend of HFC-23, HFC-32,
and HFC-134a measured by an ASTM 681 apparatus, the blend is
nonflammable. Its vapor pressure is 11.37 bars at 25.degree. C.
within 10 percent of the HCFC-22 vapor pressure. The refrigeration
capacity is about 95% of the HCFC-22. After 50 weight percent of
the refrigerant is lost through the leakage of the vapor, the vapor
pressure of the blend is 9.44 bars, still within 10% of the HCFC-22
value. The refrigeration capacity has decreased to only 83% of the
HCFC-22 value. The COP of the remaining fluid remained
substantially the same at 5.37. Both the vapor at 46 volume percent
HFC-32 and the liquid at 28 volume percent HFC-32 has remained
nonflammable as seen from FIG. 1.
EXAMPLE 76
[0041] We have performed another calculation of the type given in
Example 75 for packaged air conditioning cycle where the condenser
temperature is typically 115.degree. F. and the evaporator
temperature is typically 40.degree. F. We have further assumed
isentropic compression and a compressor inlet temperature of
60.degree. F. This time such calculations were performed for a
77.56 gram blend of 0.0384 moles of HFC-23, 0.4648 moles of HFC-32,
and 0.4968 moles of HFC-134a. The temperature glide in typical
HCFC-22 application in no case exceeded 17.degree. F. As can be
seen from the attached FIG. 1, which gives the flammability limits
of the three component blend of HFC-23, HFC-32, and HFC-134a
measured by an ASTM 681 apparatus, the blend is nonflammable. Its
vapor pressure is 12.43 bars at 25.degree. C. within 25 percent of
the HCFC-22 vapor pressure. The refrigeration capacity is
substantially the same as the HCFC-22. The COP was 5.13. After 50
weight percent of the refrigerant is lost through the leakage of
the vapor, the vapor pressure of the blend is 10.08 bars, within 2%
of the HCFC-22 value. The refrigeration capacity has decreased to
only 87% of the HCFC-22 value. The COP has increased marginally to
5.35. Both the vapor at 51 volume percent HFC-32 and the liquid at
33 volume percent HFC-32 has remained nonflammable as seen from
FIG. 1.
EXAMPLE 77
[0042] We have performed another calculation of the type given in
Examples 75 and 76 under the conditions given earlier. This time
such calculations were performed for a 75.62 gram blend of 0.0651
moles of HFC-23, 0.4865 moles of HFC-32, and 0.4484 moles of
HFC-134a. The temperature glide in typical HCFC-22 application in
no case exceeded 20.degree. F. As can be seen from the attached
FIG. 1, which gives the flammability limits of the three component
blend of HFC-23, HFC-32, and HFC-134a measured by an ASTM 681
apparatus, the blend is nonflammable. Its vapor pressure is 13.38
bars at 25.degree. C. within 30 percent of the HCFC-22 vapor
pressure. The refrigeration capacity is substantially the same as
the HCFC-22. The COP is 5.02. After 50 weight percent of the
refrigerant is lost through the leakage of the vapor, the vapor
pressure of the blend is 10.78 bars, within 4% of the HCFC-22
value. The refrigeration capacity has decreased to only 91% of the
HCFC-22 value. The COP is now 5.31. Both the vapor at 54 volume
percent HFC-32 and the liquid at 37 volume percent HFC-32 has
remained nonflammable as seen from FIG. 1.
[0043] Having described the invention in detail and by reference to
preferred embodiments thereof, it will be apparent that
modifications and variations are possible without departing from
the scope of the invention defined by the claims.
* * * * *