U.S. patent application number 16/404246 was filed with the patent office on 2019-10-31 for low gwp cascade refrigeration system.
The applicant listed for this patent is Honeywell International Inc.. Invention is credited to Michael Petersen, Gustavo Pottker, Ankit Sethi, Elizabet Del Carmen Vera Becerra, Samuel F. Yana Motta.
Application Number | 20190331366 16/404246 |
Document ID | / |
Family ID | 68291182 |
Filed Date | 2019-10-31 |
United States Patent
Application |
20190331366 |
Kind Code |
A1 |
Yana Motta; Samuel F. ; et
al. |
October 31, 2019 |
LOW GWP CASCADE REFRIGERATION SYSTEM
Abstract
Disclosed are cascade refrigerant systems for providing cooling
of air located in an enclosure that is occupied by or which will be
exposed to humans or other animals during normal use, wherein
systems includes; (1) a first, relatively low temperature heat
transfer circuit having a first evaporator located within the
enclosure and a first heat transfer fluid in the low temperature
heat transfer circuit; (2) a second heat transfer circuit located
substantially outside the enclosure comprising a second heat
transfer fluid; (3) a heat exchanger which serves as the condenser
in the low temperature circuit thermally coupled with the high
temperature circuit by virtue of rejecting heat into the second
heat transfer fluid; and (4) in the high temperature loop of a heat
exchanger which transfers heat from the second heat transfer fluid
exiting from a high temperature condenser to the portion of the
second heat transfer fluid which is traveling to the suction side
of the compressor.
Inventors: |
Yana Motta; Samuel F.; (East
Amherst, NY) ; Petersen; Michael; (Clarence Center,
NY) ; Sethi; Ankit; (Tonawanda, NY) ; Pottker;
Gustavo; (Amherst, NY) ; Vera Becerra; Elizabet Del
Carmen; (Amherst, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Honeywell International Inc. |
Morris Plains |
NJ |
US |
|
|
Family ID: |
68291182 |
Appl. No.: |
16/404246 |
Filed: |
May 6, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15468292 |
Mar 24, 2017 |
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16404246 |
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15400891 |
Jan 6, 2017 |
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15468292 |
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15434400 |
Feb 16, 2017 |
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15468292 |
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62313177 |
Mar 25, 2016 |
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62275382 |
Jan 6, 2016 |
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62295731 |
Feb 16, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09K 5/041 20130101;
F25B 2400/121 20130101; C09K 2205/126 20130101; C09K 5/045
20130101; F25B 7/00 20130101; F25B 40/00 20130101; C09K 2205/22
20130101; C09K 2205/106 20130101; F25B 9/008 20130101; F25B 9/10
20130101; C09K 5/042 20130101 |
International
Class: |
F25B 9/10 20060101
F25B009/10; F25B 7/00 20060101 F25B007/00; F25B 9/00 20060101
F25B009/00; F25B 40/00 20060101 F25B040/00 |
Claims
1. A heat transfer system for cooling the contents of an enclosure
comprising: (a) a relatively low temperature vapor compression loop
comprising a compressor, an expander and an evaporator in fluid
communication in said loop, and a first heat transfer composition
in said loop comprising a first refrigerant and lubricant for the
compressor, said evaporator being located in said enclosure and
being capable of absorbing heat from fluid in said enclosure at
about said relatively low temperature; (b) a relatively high
temperature vapor compression loop comprising a compressor, a
condenser, an expander, and a suction line heat exchanger in fluid
communication in said loop, and a second heat transfer composition
in said loop comprising a second refrigerant and preferably
lubricant for the compressor, said condenser being capable of
transferring heat to a heat sink located outside said enclosure;
and (c) a cascade heat exchanger for condensing said first
refrigerant and evaporating said second refrigerant by heat
exchange between said first and second refrigerant, wherein said
suction line heat exchanger is in fluid communication with said
cascade heat exchanger for receiving at least a portion of said
second heat transfer composition exiting said cascade heat
exchanger and increases the temperature thereof by absorbing heat
from said first heat transfer composition exiting said condenser
and thereby reducing the temperature of said first heat transfer
composition prior to said first heat transfer composition entering
said first loop expander.
2. The system of claim 1 wherein the first refrigerant has a
flammability that is substantially less than the flammability of
the second refrigerant.
3. The system of claim 1 wherein the first refrigerant has a
flammability classified as A1 under ASHRAE 34 (as measured by ASTM
E681) and the second refrigerant has a flammability that is
classified as A2L under ASHRAE 34 (as measured by ASTM E681) or a
higher flammability than A2L.
4. The system of claim 1 wherein the first and the second
refrigerant each have a Global Warming Potential (GWP) that is less
than about 150.
5. The system of claim 1 wherein each of said compressors and said
expanders and said condenser are not located in the enclosure.
6. The system of claim 5 wherein the suction line heat exchanger is
not located in the enclosure.
7. The system of claim 1 wherein said second refrigerant comprises
one or more of trans1,3,3,3-tetrafluoropropene (HFO-1234ze(E)),
2,3,3,3-tetrafluoropropene (HFO-1234yf), R-227ea, R-32 and
combinations of two or more of these.
8. The system of claim 1 wherein said second refrigerant comprises
at least about 80% by weight of 2, 3,3,3-tetrafluoropropene
(HFO-1234yf).
9. The system of claim 1 wherein said second refrigerant consists
essentially of HFO-1234ze(E), HFO-1234yf or combinations of
these.
10. The system of claim 1 wherein said second refrigerant comprises
from about 70% by weight to about 90% by weight of HFO-1234yf and
from about 10% by weight to about 30% by weight of R32.
11. The system of claim 10 wherein said second refrigerant
comprises from about 80% by weight of HFO-1234yf and about 20% by
weight of R32.
12. The system of claim 1 wherein said second refrigerant comprises
from about 70% by weight to about 90% by weight of HFO-1234yze(E)
and from about 10% by weight to about 30% by weight of R32.
13. The system of claim 1 wherein said second refrigerant comprises
about 80% by weight of HFO-1234ze(E) and about 20% by weight of
R32.
14. The system of claim 1 wherein said second refrigerant comprises
from about 85% to about 90% by weight of
trans1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) and from about 10%
by weight to about 15% by weight of
1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea).
15. The system of claim 1 wherein said second refrigerant comprises
from about 88% by weight of trans1,3,3,3-tetrafluoropropene
(HFO-1234ze(E)) and from about 10% by weight to about 12% by weight
of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea).
16. The system of claim 1 wherein the evaporating temperature of
said first refrigerant in said relatively low temperature vapor
compression loop is from about -45.degree. C. to about -25.degree.
C.
17. The system of claim 16 wherein the evaporating temperature of
said second refrigerant in said relatively high temperature vapor
compression loop is from about -15.degree. C. to about 5.degree.
C.
18. The system of claim 17 wherein the condensing temperature of
said first refrigerant in said relatively low temperature vapor
compression loop is from about -5.degree. C. to about -5.degree.
C.
19. The system of claim 18 wherein the condensing temperature of
said second refrigerant in said relatively high temperature vapor
compression loop is from about 40.degree. C. to about 50.degree.
C.
20. The system of claim 19 wherein said first refrigerant comprises
carbon dioxide and said second refrigerant comprises one or more of
trans1,3,3,3-tetrafluoropropene (HFO-1234ze(E)),
2,3,3,3-tetrafluoropropene (HFO-1234yf), R-227ea, R-32 and
combinations of two or more of these.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S.
application Ser. No. 15/468,292, filed Mar. 24, 2017, which claims
priority to Provisional Application 62/313,177, filed Mar. 25,
2016, which is incorporated herein by reference in its
entirety.
[0002] U.S. application Ser. No. 15/468,292 is also a
continuation-in-part of U.S. application Ser. No. 15/400,891, filed
Jan. 6, 2017, now pending, which in turn claims the priority
benefit of Provisional application 62/275,382, filed Jan. 6, 2016,
each of which is incorporated herein by reference in its
entirety.
[0003] U.S. application Ser. No. 15/468,292 is also a
continuation-in-part of U.S. application Ser. No. 15/434,400, filed
Feb. 16, 2017, now pending, which in turn claims the priority
benefit of 62/295,731, filed Feb. 16, 2016, the entire contents of
each of which is hereby incorporated by reference.
FIELD OF THE INVENTION
[0004] The present invention relates to high efficiency, low-global
warming potential ("low GWP") air conditioning and/or refrigeration
systems and methods for providing cooling that are safe and
effective.
BACKGROUND
[0005] In typical air conditioning and refrigerant systems, a
compressor is used to compress a heat transfer vapor from a lower
to a higher pressure, which in turn adds heat to the vapor. This
added heat is typically rejected in a heat exchanger, commonly
referred to as a condenser. The heat transfer vapor that enters the
condenser is condensed to produce a liquid heat transfer fluid at a
relatively high pressure. Typically the condenser uses a fluid
available in large quantities in the ambient environment, such as
ambient outside air, as the heat sink. Once it has been condensed,
the high-pressure heat transfer fluid undergoes a substantially
isoenthalpic expansion, such would occur by passing the fluid
through an expansion device or valve, where it is expanded to a
lower pressure, which in turn results in the fluid undergoing a
decrease in temperature. The lower pressure, lower temperature heat
transfer fluid from the expansion operation then is typically
routed to an evaporator, where it absorbs heat and in so doing
evaporates. This evaporation process in turn results in cooling of
the fluid or body to that it is intended to cool. In many typical
air conditioning and refrigeration applications, the cooled fluid
is the air which is contained in the region to be cooled, such as
the air in the dwelling being air conditioned or the air inside a
walk-in cooler or a supermarket cooler or freezer. After the heat
transfer fluid is evaporated at low pressure in the evaporator, it
is returned to the compressor where the cycle begins once
again.
[0006] A complex and interrelated combination of factors and
requirements is associated with forming efficient, effective and
safe air conditioning systems that are at the same time
environmentally friendly, that is, have both low GWP impact and low
ozone depletion ("ODP" impact. With respect to efficiency and
effectiveness, it is important for the heat transfer fluid to
operate in air conditioning and refrigeration systems with high
levels of efficiency and high relative capacity. At the same time,
since it is possible that the heat transfer fluid may escape over
time into the atmosphere, it is important for the fluid to have low
values for both GWP and ODP.
[0007] Applicants have come to appreciate that while certain fluids
are able to achieve high levels of both efficiency and
effectiveness, and at the same time low levels of both GWP and ODP,
many fluids which satisfy this combination of requirements
nevertheless suffer from the disadvantage of having deficiencies in
connection with safety. For example, fluids which might otherwise
be acceptable may be disfavored because of flammability properties
and/or toxicity concerns. Applicants have come to appreciate that
the use of fluids having such properties is especially undesirable
in typical air conditioning and in many refrigeration systems since
such flammable and/or toxic fluids may inadvertently be released
into the dwelling, walk-in, cold-box, chiller, freezer or transport
refrigeration box which is being cooled, thus exposing or
potentially exposing the occupants thereof to dangerous conditions.
Applicants have also come to appreciate that this problem is even
of a more intense concern for relatively small systems, e.g.,
systems with a capacity of less than 30 kw since for such systems
the cost of effective safety protection systems, such as fire
protections systems, are frequently not economically viable.
SUMMARY
[0008] According to one aspect of the invention, a cascade
refrigerant system is provided for providing cooling of air,
directly or indirectly but preferably directly, located in an
enclosure that is occupied by or which will be exposed to humans or
other animals during normal use. As used herein, the term
"enclosure" means a space that is at least partially confined
(e.g., the enclosure can be opened on one or more sides, or closed)
and includes air that has been cooled.
[0009] Preferred embodiments of the present systems include at
least a first evaporator which is located within the enclosure and
is part of a first, relatively low temperature heat transfer
circuit. The low temperature heat transfer circuit preferably
comprises a first heat transfer fluid in a vapor compression
circulation loop comprising at least: a compressor for raising the
pressure of the first heat transfer composition; a heat exchanger
for condensing at least a portion of the first heat transfer
composition from the compressor at a relatively high pressure; an
expansion device for lowering the pressure of the heat transfer
composition from the condenser; and an evaporator for absorbing
heat from the enclosure to be cooled into the heat transfer
composition. Preferably one or more of said compressor, condenser
and said expansion valve, and most preferably all of these, are
located outside the enclosure and the evaporator is located within
the enclosure.
[0010] The systems of the present invention also preferably include
a second heat transfer circuit located substantially outside the
enclosure, which is sometimes referred to herein by way of
convenience as the "high temperature" loop. The high temperature
loop preferably comprises a second heat transfer fluid in a vapor
compression circulation loop comprising at least a compressor, a
heat exchanger which serves to condense the heat transfer fluid in
the high temperature loop, preferably by heat exchange with ambient
air outside of the enclosure, and an expansion device for reducing
the pressure of the second heat transfer fluid from the
compressor.
[0011] An important aspect of preferred embodiments of the present
invention is that the heat exchanger which serves as the condenser
in the low temperature circuit is thermally coupled with the high
temperature circuit by virtue of rejecting heat into the second
heat transfer fluid, preferably by causing at least a substantial
portion of said second heat transfer fluid to evaporate. In this
way, the condenser of the low temperature circuit and the
evaporator of the high temperature circuit are thermally coupled in
this heat exchanger, which is sometimes referred to for convenience
as "a cascade heat exchanger" in the systems and methods of the
present invention.
[0012] Another important aspect of the present invention in
preferred embodiments comprises the presence in the high
temperature loop of a heat exchanger which has been found to
advantageously and unexpectedly improve system performance by
transferring heat from the second heat transfer fluid exiting from
the high temperature condenser to the portion of the second heat
transfer fluid which is traveling to the suction side of the
compressor. This heat exchanger is sometimes referred to herein for
convenience as a "suction line heat exchanger."
[0013] Another important aspect of the preferred systems is that
the first heat transfer fluid which is circulating in the low
temperature loop comprises a refrigerant which has a GWP of not
greater than about 500, more preferably not greater than about 400,
and even more preferably not greater than about 150 and furthermore
that the first heat transfer fluid has a flammability that is
substantially less than the flammability of the second heat
transfer fluid. Preferably, the second heat transfer fluid which is
circulating in the high temperature loop also comprises a
refrigerant which has a GWP of not greater than about 500, more
preferably not greater than about 400, and even more preferably not
greater than about 150, but since in normal operation this heat
transfer fluid will never enter the enclosure, applicants have
found that is advantageous to use a fluid in this high temperature
loop that has one or properties that would be considered
disadvantageous if it circulated within the enclosure, for example,
flammability, toxicity and the like. In this way, the present
systems allow additional possible unexpected advantages over
systems that would rely only of the first heat transfer composition
or only the second heat transfer composition, as explained in
detail below.
[0014] In certain preferred embodiments the second refrigerant
comprises, more preferably comprises at least about 50% by weight
and even more preferably at least about 75% by weight, of
trans-1,3,3,3-trifluoropropene (HFO-1234ze(E) and/or HFO-1234yf,
and the second refrigerant has a flammability greater than, and
preferably substantially greater than about, the flammability of
CO2. In another embodiment the second refrigerant comprises, more
preferably comprises at least about 75% by weight and even more
preferably at least about 80% by weight, of
trans-1,3,3,3-trifluoropropene (HFO-1234ze(E) and/or
HFO-1234yf.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a generalized process flow diagram of one
preferred embodiment of an air conditioning system according to the
present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0016] Preferred Heat Transfer Compositions
[0017] In each of the preferred embodiments described herein the
system includes:
[0018] (a) a relatively low temperature vapor compression loop
comprising a compressor, an expander and an evaporator in fluid
communication in said loop, and a first heat transfer composition
in said loop comprising a first refrigerant and preferably
lubricant for the compressor, said evaporator being located in an
enclosure containing air to be cooled and being capable of
absorbing heat from said air at about said relatively low
temperature;
[0019] (b) a relatively high temperature vapor compression loop
comprising a compressor, a condenser, an expander, and a suction
line heat exchanger in fluid communication in said loop, and a
second heat transfer composition in said loop comprising a second
refrigerant and preferably lubricant for the compressor, said
condenser being capable of transferring heat to a heat sink located
outside said enclosure; and
[0020] (c) a cascade heat exchanger for condensing said first
refrigerant and evaporating said second refrigerant by heat
exchange between said first and second refrigerant,
wherein said suction line heat exchanger is in fluid communication
with said cascade heat exchanger for receiving at least a portion
of said second heat transfer composition exiting said cascade heat
exchanger and increases the temperature thereof by absorbing heat
from said first heat transfer composition exiting said condenser
and thereby reducing the temperature of said first heat transfer
composition prior to said first heat transfer composition entering
said first loop expander.
[0021] As used herein, the terms "relatively low temperature" and
"relatively high temperature," when used together with respect to
the first and second heat transfer loops, and unless otherwise
indicated, are used in a relative sense to designate the relative
temperature of the indicated heat transfer compositions, where
those differences are least about 5.degree. C.
[0022] Preferably the first refrigerant has a flammability that is
substantially less than the flammability of the second refrigerant.
In preferred embodiments, the first refrigerant has a flammability
according to ASHRAE Standard 34 (which specifies measurement
according to ASTM E681) that is classified as A1 and the second
refrigerant has a flammability according to ASHRAE Standard 34 that
is classified as A2L or a higher flammability than A2L, although
A2L classification for the second refrigerant is preferred. It is
also preferred that the first and the second refrigerant each have
a Global Warming Potential (GWP) that is less than about 150.
[0023] In preferred embodiments the first refrigerant circulating
in the low temperature loop comprises carbon dioxide, preferably
consists essentially of carbon dioxide and more preferably in some
embodiments consists of carbon dioxide.
[0024] It is preferred that the second refrigerant comprises one or
more of trans1,3,3,3-tetrafluoropropene (HFO-1234ze(E)),
2,3,3,3-tetrafluoropropene (HFO-1234yf), R-227ea, and R-32 and
combinations of two or more of these. In preferred embodiments, the
second refrigerant comprises at least about 50%, more preferably at
least about 80% by weight of 2, 3,3,3-tetrafluoropropene
(HFO-1234yf). In other preferred embodiments, the second
refrigerant comprises at least about 50%, more preferably at least
about 80% by weight of or at least about 75% by weight, more
preferably at least about 80% by weight of
trans1,3,3,3-tetrafluoropropene (HFO-1234ze(E)). In highly
preferred embodiments, the second refrigerant comprises at least
about 95% by weight, and in some embodiments consists essentially
of or consists of HFO-1234ze(E), HFO-1234yf or combinations of two
or more of these.
[0025] In other highly preferred embodiments, the second
refrigerant comprises from about 70% by weight to about 90% of
HFO-1234yf, preferably about 80% by weight of HFO-1234yf and from
about 10% by weight to about 30% by weight of R32, preferably about
20% by weight of R-32.
[0026] In other highly preferred embodiments, the second
refrigerant comprises from about 70% by weight to about 90% of
HFO-1234ze(E), preferably about 80% by weight of HFO-1234ze(E) and
from about 10% by weight to about 30% by weight of R32, preferably
about 20% by weight of R-32.
[0027] In other highly preferred embodiments, the second
refrigerant comprises from about 85% to about 90% by weight of by
weight of trans1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) and from
about 10% by weight to about 15% by weight of
1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), and even more
preferably in some embodiments about 88% of
trans1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) and about 12% by
weight of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea).
[0028] Those skilled in the art will appreciate in view of the
disclosures contained herein that the preferred embodiments of the
present invention provide the advantage of utilizing only the safe
(relatively low toxicity and low flammability) low GWP refrigerants
within the enclosure to be cooled and a relatively less safe, but
preferably low GWP refrigerant in the high temperature loop which
is located entirely outside of the enclosure.
[0029] As used herein, the terms "safe" and "relatively less safe,"
when used together with respect to the first and second heat
transfer loops, and unless otherwise indicated, are used in a
relative sense to designate the relative safety of the indicated
heat transfer compositions. Such configuration, especially when the
high temperature system includes the preferred suction line heat
exchanger, makes the systems and methods of the invention highly
preferred for use in a location proximate to the humans or other
animals occupying or using the enclosure, as is commonly
encountered in walk-in freezers, supermarket coolers and the
like.
[0030] Preferred embodiments of the second refrigerant are
disclosed in the following table:
TABLE-US-00001 Component Second Refrigerant R-1234yf, R-1234ze(E),
Designation wt % wt % R-32 R227ea SR1 5 95 0 0 SR2 10 90 0 0 SR3 15
85 0 0 SR4 20 80 0 0 SR4 25 75 0 0 SR5 30 70 0 0 SR6 35 65 0 0 SR7
40 95 0 0 SR8 45 50 0 0 SR9 50 50 0 0 SR10 55 45 0 0 SR11 60 40 0 0
SR12 65 35 0 0 SR13 70 30 0 0 SR14 75 25 0 0 SR15 80 20 0 0 SR16 85
15 0 0 SR17 90 10 0 0 SR18 95 5 0 0 SR19 70 0 30 0 SR20 75 0 25 0
SR21 80 0 20 0 SR22 85 0 15 0 SR23 90 0 10 0 SR24 0 70 30 0 SR25 0
75 25 0 SR26 0 80 20 0 SR27 0 85 15 0 SR28 0 90 10 0 SR29 0 80 0 20
SR30 0 85 0 15 SR31 0 88 0 12 SR32 0 90 0 10 SR33 0 95 0 5
[0031] The first heat transfer composition and the second heat
transfer compositions also each generally include a lubricant,
generally in amounts of from about 30 to about 50 percent by weight
of the heat transfer composition, with the balance comprising
refrigerant and other optional components that may be present.
Combinations of surfactants and solubilizing agents may also be
added to the present compositions to aid oil solubility, as
disclosed by U.S. Pat. No. 6,516,837, the disclosure of which is
incorporated by reference. Commonly used refrigeration lubricants
such as Polyol Esters (POEs) and Poly Alkylene Glycols (PAGs),
silicone oil, mineral oil, alkyl benzenes (ABs) and
poly(alpha-olefin) (PAO) that are used in refrigeration machinery
with hydrofluorocarbon (HFC) refrigerants may be used with the
refrigerant compositions of the present invention. The preferred
lubricants are POEs.
[0032] Preferred combinations of first refrigerant, second
refrigerant and lubricant according to one aspect of the invention
are provided below.
TABLE-US-00002 SECOND HEAT TRANSFER FIRST HEAT TRANSFER COMPOSITION
COMPOSITION Regrig., Lub, Regrig., Lub, EMBODIMENT Refrig. wt % Lub
wt % Refrig. wt % Lub wt % 1 1234yf 90-99 PAG 1-10 CO.sub.2 90-99
POE 1-10 2 1234yf 80-89 PAG 11-20 CO2 80-90 POE 11-20 4 1234yf
90-99 POE 1-10 CO2 90-99 POE 1-10 5 1234yf 80-89 POE 11-20 CO2
80-90 POE 11-20 6 1234ze(E) 90-99 PAG 1-10 CO2 90-99 POE 1-10 7
1234ze(E) 80-89 PAG 11-20 CO2 80-90 POE 11-20 8 1234ze(E) 90-99 POE
1-10 CO2 90-99 POE 1-10 9 1234ze(E) 80-89 POE 11-20 CO2 80-90 POE
11-20 10 SR1 90-99 PAG 1-10 CO2 90-99 POE 1-10 11 SR1 80-89 PAG
11-20 CO2 80-90 POE 11-20 12 SR1 90-99 POE 1-10 CO2 90-99 POE 1-10
13 SR1 80-89 POE 11-20 CO2 80-90 POE 11-20 14 SR2 90-99 PAG 1-10
CO2 90-99 POE 1-10 15 SR2 80-89 PAG 11-20 CO2 80-90 POE 11-20 16
SR2 90-99 POE 1-10 CO2 90-99 POE 1-10 17 SR2 80-89 POE 11-20 CO2
80-90 POE 11-20 18 SR3 90-99 PAG 1-10 CO2 90-99 POE 1-10 19 SR3
80-89 PAG 11-20 CO2 80-90 POE 11-20 20 SR3 90-99 POE 1-10 CO2 90-99
POE 1-10 21 SR3 80-89 POE 11-20 CO2 80-90 POE 11-20 22 SR4 90-99
PAG 1-10 CO2 90-99 POE 1-10 23 SR4 80-89 PAG 11-20 CO2 80-90 POE
11-20 24 SR4 90-99 POE 1-10 CO2 90-99 POE 1-10 25 SR4 80-89 POE
11-20 CO2 80-90 POE 11-20 26 SR5 90-99 PAG 1-10 CO2 90-99 POE 1-10
27 SR5 80-89 PAG 11-20 CO2 80-90 POE 11-20 28 SR5 90-99 POE 1-10
CO2 90-99 POE 1-10 29 SR5 80-89 POE 11-20 CO2 80-90 POE 11-20 30
SR6 90-99 PAG 1-10 CO2 90-99 POE 1-10 31 SR6 80-89 PAG 11-20 CO2
80-90 POE 11-20 32 SR6 90-99 POE 1-10 CO2 90-99 POE 1-10 33 SR6
80-89 POE 11-20 CO2 80-90 POE 11-20 34 SR7 90-99 PAG 1-10 CO2 90-99
POE 1-10 35 SR7 80-89 PAG 11-20 CO2 80-90 POE 11-20 36 SR7 90-99
POE 1-10 CO2 90-99 POE 1-10 37 SR7 80-89 POE 11-20 CO2 80-90 POE
11-20 38 SR8 90-99 PAG 1-10 CO2 90-99 POE 1-10 39 SR8 80-89 PAG
11-20 CO2 80-90 POE 11-20 40 SR8 90-99 POE 1-10 CO2 90-99 POE 1-10
41 SR8 80-89 POE 11-20 CO2 80-90 POE 11-20 41 SR9 90-99 PAG 1-10
CO2 90-99 POE 1-10 42 SR9 80-89 PAG 11-20 CO2 80-90 POE 11-20 43
SR9 90-99 POE 1-10 CO2 90-99 POE 1-10 44 SR10 90-99 PAG 1-10 CO2
90-99 POE 1-10 45 SR10 80-89 PAG 11-20 CO2 80-90 POE 11-20 46 SR10
90-99 POE 1-10 CO2 90-99 POE 1-10 47 SR10 80-89 POE 11-20 CO2 80-90
POE 11-20 48 SR11 90-99 PAG 1-10 CO2 90-99 POE 1-10 49 SR11 80-89
PAG 11-20 CO2 80-90 POE 11-20 50 SR11 90-99 POE 1-10 CO2 90-99 POE
1-10 51 SR11 80-89 POE 11-20 CO2 80-90 POE 11-20 52 SR12 90-99 PAG
1-10 CO2 90-99 POE 1-10 53 SR12 80-89 PAG 11-20 CO2 80-90 POE 11-20
54 SR12 90-99 POE 1-10 CO2 90-99 POE 1-10 55 SR12 80-89 POE 11-20
CO2 80-90 POE 11-20 56 SR13 90-99 PAG 1-10 CO2 90-99 POE 1-10 57
SR13 80-89 PAG 11-20 CO2 80-90 POE 11-20 58 SR13 90-99 POE 1-10 CO2
90-99 POE 1-10 59 SR13 80-89 POE 11-20 CO2 80-90 POE 11-20 60 SR14
90-99 PAG 1-10 CO2 90-99 POE 1-10 61 SR14 80-89 PAG 11-20 CO2 80-90
POE 11-20 62 SR14 90-99 POE 1-10 CO2 90-99 POE 1-10 63 SR14 80-89
POE 11-20 CO2 80-90 POE 11-20 64 SR15 90-99 PAG 1-10 CO2 90-99 POE
1-10 65 SR15 80-89 PAG 11-20 CO2 80-90 POE 11-20 66 SR15 90-99 POE
1-10 CO2 90-99 POE 1-10 67 SR15 80-89 POE 11-20 CO2 80-90 POE 11-20
68 SR16 90-99 PAG 1-10 CO2 90-99 POE 1-10 69 SR16 80-89 PAG 11-20
CO2 80-90 POE 11-20 70 SR16 90-99 POE 1-10 CO2 90-99 POE 1-10 71
SR16 80-89 POE 11-20 CO2 80-90 POE 11-20 72 SR17 90-99 PAG 1-10 CO2
90-99 POE 1-10 73 SR17 80-89 PAG 11-20 CO2 80-90 POE 11-20 74 SR17
90-99 POE 1-10 CO2 90-99 POE 1-10 75 SR17 80-89 POE 11-20 CO2 80-90
POE 11-20 76 SR18 90-99 PAG 1-10 CO2 90-99 POE 1-10 77 SR18 80-89
PAG 11-20 CO2 80-90 POE 11-20 78 SR18 90-99 POE 1-10 CO2 90-99 POE
1-10 79 SR18 80-89 POE 11-20 CO2 80-90 POE 11-20 80 SR19 90-99 PAG
1-10 CO2 90-99 POE 1-10 81 SR19 80-89 PAG 11-20 CO2 80-90 POE 11-20
82 SR19 90-99 POE 1-10 CO2 90-99 POE 1-10 83 SR19 80-89 POE 11-20
CO2 80-90 POE 11-20 84 SR20 90-99 PAG 1-10 CO2 90-99 POE 1-10 85
SR20 80-89 PAG 11-20 CO2 80-90 POE 11-20 86 SR20 90-99 POE 1-10 CO2
90-99 POE 1-10 87 SR20 80-89 POE 11-20 CO2 80-90 POE 11-20 88 SR21
90-99 PAG 1-10 CO2 90-99 POE 1-10 89 SR21 80-89 PAG 11-20 CO2 80-90
POE 11-20 90 SR21 90-99 POE 1-10 CO2 90-99 POE 1-10 91 SR21 80-89
POE 11-20 CO2 80-90 POE 11-20 92 SR22 90-99 PAG 1-10 CO2 90-99 POE
1-10 93 SR22 80-89 PAG 11-20 CO2 80-90 POE 11-20 94 SR22 90-99 POE
1-10 CO2 90-99 POE 1-10 95 SR22 80-89 POE 11-20 CO2 80-90 POE 11-20
96 SR23 90-99 PAG 1-10 CO2 90-99 POE 1-10 97 SR23 80-89 PAG 11-20
CO2 80-90 POE 11-20 98 SR23 90-99 POE 1-10 CO2 90-99 POE 1-10 99
SR23 80-89 POE 11-20 CO2 80-90 POE 11-20 100 SR24 90-99 PAG 1-10
CO2 90-99 POE 1-10 101 SR24 80-89 PAG 11-20 CO2 80-90 POE 11-20 102
SR24 90-99 POE 1-10 CO2 90-99 POE 1-10 103 SR24 80-89 POE 11-20 CO2
80-90 POE 11-20 104 SR25 90-99 PAG 1-10 CO2 90-99 POE 1-10 105 SR25
80-89 PAG 11-20 CO2 80-90 POE 11-20 106 SR25 90-99 POE 1-10 CO2
90-99 POE 1-10 107 SR25 80-89 POE 11-20 CO2 80-90 POE 11-20 108
SR26 90-99 PAG 1-10 CO2 90-99 POE 1-10 109 SR26 80-89 PAG 11-20 CO2
80-90 POE 11-20 110 SR26 90-99 POE 1-10 CO2 90-99 POE 1-10 111 SR26
80-89 POE 11-20 CO2 80-90 POE 11-20 112 SR27 90-99 PAG 1-10 CO2
90-99 POE 1-10 113 SR27 80-89 PAG 11-20 CO2 80-90 POE 11-20 114
SR27 90-99 POE 1-10 CO2 90-99 POE 1-10 115 SR27 80-89 POE 11-20 CO2
80-90 POE 11-20 116 SR28 90-99 PAG 1-10 CO2 90-99 POE 1-10 117 SR28
80-89 PAG 11-20 CO2 80-90 POE 11-20 118 SR28 90-99 POE 1-10 CO2
90-99 POE 1-10 119 SR28 80-89 POE 11-20 CO2 80-90 POE 11-20 120
SR29 90-99 PAG 1-10 CO2 90-99 POE 1-10 121 SR29 80-89 PAG 11-20 CO2
80-90 POE 11-20 122 SR29 90-99 POE 1-10 CO2 90-99 POE 1-10 123 SR29
80-89 POE 11-20 CO2 80-90 POE 11-20 124 SR30 90-99 PAG 1-10 CO2
90-99 POE 1-10 125 SR30 80-89 PAG 11-20 CO2 80-90 POE 11-20 126
SR30 90-99 POE 1-10 CO2 90-99 POE 1-10 127 SR30 80-89 POE 11-20 CO2
80-90 POE 11-20 128 SR31 90-99 PAG 1-10 CO2 90-99 POE 1-10 129 SR31
80-89 PAG 11-20 CO2 80-90 POE 11-20 130 SR31 90-99 POE 1-10 CO2
90-99 POE 1-10 131 SR31 80-89 POE 11-20 CO2 80-90 POE 11-20 132
SR32 90-99 PAG 1-10 CO2 90-99 POE 1-10 133 SR32 80-89 PAG 11-20 CO2
80-90 POE 11-20 134 SR32 90-99 POE 1-10 CO2 90-99 POE 1-10 135 SR32
80-89 POE 11-20 CO2 80-90 POE 11-20 136 SR33 90-99 PAG 1-10 CO2
90-99 POE 1-10 137 SR33 80-89 PAG 11-20 CO2 80-90 POE 11-20 138
SR33 90-99 POE 1-10 CO2 90-99 POE 1-10 139 SR33 80-89 POE 11-20 CO2
80-90 POE 11-20
[0033] System Operating Conditions
[0034] It is generally contemplated that operating conditions used
in the present systems and methods can be varied widely in view of
the disclosure contained herein depending upon the specific
applications. However, many preferred applications will
advantageously use operating parameters within the ranges indicated
in the table below, with all amounts understood to be modified by
"about":
TABLE-US-00003 BROAD INTERMEDIATE NARROW Evaporating -45 to -25 -40
to -30 -35 temperature of the low stage evaporator, .degree. C.
Condensing temperature -10 to 10 -5 to 5 0 of the low-stage,
.degree. C. Evaporating -15 to 5 -10 to 0 -5 temperature of the
high- stage, .degree. C. Condensing 35 to 55 40 to 50 45 C.
Temperature of the high-stage, .degree. C. Evaporator Superheat 0
to 15 0 to 10 5 (each stage) , .degree. C. Temperature rise in the
5 to 25 10 to 20 15 suction line of the low- stage, .degree. C.
Temperature rise in the 0 to 15 0 to 10 5 suction line of the high-
stage, .degree. C. Subcooling at both 0 to 10 0 to 5 0 expansion
devices of high and low stages, .degree. C. Compressor discharge
from about from about not greater temperature (low and 120 to about
125 to about than 125 high stage), .degree. C. 130 130
[0035] When operating within the process conditions according to
the present invention, the use of the suction line heat exchanger
as described herein preferably produces at least a 2% COP
improvement, more preferably at least about 3% COP improvement, and
even more preferably a 4% COP improvement compared to the same
system but without a suction-line heat exchanger according to the
present invention.
[0036] In the following descriptions, components or elements of the
system which are or can be generally the same or similar in
different embodiments are designated with the same number or
symbol.
[0037] One preferred refrigeration system is illustrated in FIG. 1.
The refrigeration system is designated generally as 10. The
boundaries designates generally as 100 represent schematically the
enclosure. The low temperature loop comprises compressor 11,
condensing side 12A of the cascade exchange 12, expansion valve 14
and evaporator 15. As illustrated, evaporator 15 is located within
enclosure 100, together with any of the associated conduits and
other connecting and related equipment to transport the first heat
transfer composition to and from the enclosure boundary. Although
the evaporator 14 is preferably located inside the enclosure, and
is disclosed in the illustrated FIGURE as being located inside of
the enclosure 100, it will be appreciated that in certain
embodiments it may be desirable and/or necessary to provide the
expander 14 outside of the enclosure. The high temperature loop
comprises compressor 21, evaporating side 12B of the cascade
exchange 12, expansion valve 24 and condenser 25, all located
outside of enclosure 100, together with any of the associated
conduits and other connecting and related equipment. The high
temperature circuit also includes suction line heat exchanger 50
which enables the exchange of heat between the second heat transfer
composition stream 30 exiting condenser 25 and the second heat
transfer composition stream 31 exiting the evaporating side 12B of
the cascade heat exchanger 12.
[0038] Although it is contemplated that the relative size of the
first and second refrigeration loops according to the present
invention maybe vary widely within the scope hereof, applicants
have found that highly advantageous results can be achieved in
certain embodiments by judicious selection of the relative sizes of
the refrigeration loops. More specifically, it is contemplated and
understood that under normal operating conditions the heat transfer
composition contained in the first refrigeration loop and in the
second refrigeration loop will never mix or intermingle. However,
applicants have come to appreciate that the possibility of such
intermixing of first and second refrigerants might occur for
example, in the case of leakage in the cascade heat exchanger. This
mixed refrigerant stream may then, in the event of a leak within
the enclosure being cold, become exposed to humans or other animals
located in or near the enclosure. Accordingly, in order to ensure
continued safe operation even in the case of such leakage,
applicants have come to appreciate that careful and judicious
selection of the relative refrigeration loop sizes can result in a
safe system even in the event of such a leakage.
[0039] While applicants contemplate that the systems and
compositions of the present invention will be useful in many
refrigeration applications, preferred applications include
refrigeration systems and methods used in applications such as
treating the air, including cooling and/or heating, in enclosures
such as residential dwellings, office space, warehouses and the
like, and in connection with enclosures used to keep items cool by
cooling the air in the enclosure, such as walk-in boxes,
cold-boxes, transport refrigeration boxes and the like. As used
herein, the term "transport refrigeration box" is used to designate
cold/insulated boxes which are located on or comprise a portion or
substantially all of a truck trailer. Furthermore, in preferred
applications the capacity of the system according to the present
invention is less than about 30 kW. In preferred applications the
capacity of the system according to the present invention is less
than about 15 kW, and in yet further applications the capacity of
the system according to the present invention is less than about 10
kW.
[0040] Examples of several preferred systems, methods and
compositions are described below:
[0041] A. First Refrigerant is CO2 and Second Refrigerant is
R-1234ze(E)
[0042] By way of example, applicants have considered a cascade
refrigeration system according to the present invention in which
the first refrigerant consists of CO2 in the second refrigerant
consists of R01234ze(E). In order to arrive at a refrigeration
system according to the present invention which is safe, even in
the event of intermixing between the first and second refrigerants,
applicants have determined the flammability of various mixtures
(including vapor and liquid) of these components as follows:
TABLE-US-00004 Ratio Composition CO.sub.2 to Number R1234ze
CO.sub.2 R1234ze Flammability 1 99% 1% 0.01 Vapor and liquid
flammable 2 90% 10% 0.11 Liquid flammable 3 70% 30% 0.43 Liquid
flammable 4 50% 50% 1.00 Liquid flammable 5 46% 54% 1.17
Non-Flammable 6 40% 60% 1.50 Non-Flammable 7 30% 70% 2.33
Non-Flammable 8 5% 95% 19.00 Non-Flammable
[0043] Based upon the above considerations and analysis, and
preferred aspects of the present invention in which the first
refrigerant consists essentially of CO2 and a second refrigerant
consists essentially of R-1234ze(E), it is preferred that the
weight ratio of the loading of the first refrigerant (e.g. CO2) in
the low temperature loop to the second refrigerant (e.g.
R-1234ze(E)) is not less than about 1.2. In such embodiments, the
system of the present invention will remain safe, i.e., contain
only nonflammable refrigerant, even in the event of complete
intermixing between the first and the second refrigerant
compositions.
[0044] B. First Refrigerant is CO2 and Second Refrigerant is
SR26
[0045] By way of further example, applicants have considered a
cascade refrigeration system according to the present invention in
which the first refrigerant consists of CO2 and the second
refrigerant consists of a SR26 (80:20 weight ratio combination of
R-1234ze(E); R-32). In order to arrive at a refrigeration system
according to the present invention which is safe, even in the event
of intermixing between the first and second refrigerants,
applicants have determined the flammability of various mixtures
(including vapor and liquid) of these components as follows:
TABLE-US-00005 Composition Ratio R1234ze + CO.sub.2 to R32 R1234ze
+ Number (0.8/0.2) CO.sub.2 R32 Flammability 1 100% 0% 0 Vapor and
liquid flammable 2 99% 1% 0.01 Vapor and liquid flammable 3 90% 10%
0.11 Liquid flammable 5 70% 30% 0.43 Liquid flammable 6 50% 50%
1.00 Liquid flammable 7 49% 51% 1.04 Non-Flammable 8 40% 60% 1.50
Non-Flammable 9 30% 70% 2.33 Non-Flammable 10 5% 95% 19.00
Non-Flammable
Based upon the above considerations and analysis, and preferred
aspects of the present invention in which the first refrigerant
consists essentially of CO2 and a second refrigerant consists
essentially of SR26, it is preferred that the weight ratio of the
loading of the first refrigerant (e.g. CO2) in the low temperature
loop to the second refrigerant (e.g. SR26) is not less than about
1.0. In such embodiments, the system of the present invention will
remain safe, i.e., contain only nonflammable refrigerant, even in
the event of complete intermixing between the first and the second
refrigerant compositions.
[0046] C. First Refrigerant is CO2 and Second Refrigerant is
R-32
[0047] By way of additional example, applicants have considered a
cascade refrigeration system according to the present invention in
which the first refrigerant consists of CO2 and the second
refrigerant consists of a R-32. In order to arrive at a
refrigeration system according to the present invention which is
safe, even in the event of intermixing between the first and second
refrigerants, applicants have determined the flammability of
various mixtures (including vapor and liquid) of these components
as follows:
TABLE-US-00006 Composition Ratio Number R32 CO.sub.2 CO.sub.2 to
R32 Flammability 1 100% 0% 0 Vapor and liquid flammable 2 99% 1%
0.01 Vapor and liquid flammable 3 90% 10% 0.11 Vapor and liquid
flammable 4 80% 20% 0.25 Liquid flammable 5 70% 30% 0.43 Liquid
flammable 6 60% 40% 0.67 Liquid flammable 7 53% 47% 0.89
Non-Flammable 8 50% 50% 1.00 Non-Flammable 9 40% 60% 1.50
Non-Flammable 10 10% 90% 9.00 Non-Flammable 11 5% 95% 19.00
Non-Flammable
Based upon the above considerations and analysis, and preferred
aspects of the present invention in which the first refrigerant
consists essentially of CO2 and a second refrigerant consists
essentially of SR26, it is preferred that the weight ratio of the
loading of the first refrigerant (e.g. CO2) in the low temperature
loop to the second refrigerant (e.g. SR26) is not less than about
0.9. In such embodiments, the system of the present invention will
remain safe, i.e., contain only nonflammable refrigerant, even in
the event of complete intermixing between the first and the second
refrigerant compositions.
[0048] D. First Refrigerant is CO2 and Second Refrigerant is
Ethane
[0049] By way of additional example, applicants have considered a
cascade refrigeration system according to the present invention in
which the first refrigerant consists of CO2 and the second
refrigerant consists of ethane. In order to arrive at a
refrigeration system according to the present invention which is
safe, even in the event of intermixing between the first and second
refrigerants, applicants have determined the flammability of
various mixtures (including vapor and liquid) of these components
as follows:
TABLE-US-00007 Composition Ratio Number Ethane CO.sub.2 CO.sub.2 to
Ethane Flammability 1 100% 0% 0 Vapor and liquid flammable 2 90%
10% 0.11 Vapor and liquid flammable 3 80% 20% 0.25 Vapor and liquid
flammable 4 70% 30% 0.43 Liquid flammable 5 60% 40% 0.67 Liquid
flammable 6 50% 50% 1.00 Liquid flammable 7 40% 60% 1.50 Liquid
flammable 8 37% 63% 1.70 Non-Flammable 9 30% 70% 2.33 Non-Flammable
10 20% 80% 4.00 Non-Flammable 11 10% 90% 9.00 Non-Flammable 12 5%
95% 19.00 Non-Flammable
Based upon the above considerations and analysis, and preferred
aspects of the present invention in which the first refrigerant
consists essentially of CO2 and a second refrigerant consists
essentially of ethane, it is preferred that the weight ratio of the
loading of the first refrigerant (e.g. CO2) in the low temperature
loop to the second refrigerant (e.g. SR26) is not less than about
1.7. In such embodiments, the system of the present invention will
remain safe, i.e., contain only nonflammable refrigerant, even in
the event of complete intermixing between the first and the second
refrigerant compositions.
[0050] E. First Refrigerant is CO2 and Second Refrigerant is
Propane
[0051] By way of additional example, applicants have considered a
cascade refrigeration system according to the present invention in
which the first refrigerant consists of CO2 and the second
refrigerant consists of propone. In order to arrive at a
refrigeration system according to the present invention which is
safe, even in the event of intermixing between the first and second
refrigerants, applicants have determined the flammability of
various mixtures (including vapor and liquid) of these components
as follows:
TABLE-US-00008 Composition Ratio Number Propane CO.sub.2 CO.sub.2
to Propane Flammability 1 100% 0% 0 Vapor and liquid flammable 2
90% 10% 0.11 Liquid flammable 3 80% 20% 0.25 Liquid flammable 4 70%
30% 0.43 Liquid flammable 5 60% 40% 0.67 Liquid flammable 6 50% 50%
1.00 Liquid flammable 7 40% 60% 1.50 Liquid flammable 8 30% 70%
1.70 Liquid flammable 9 20% 80% 1.50 Liquid flammable 10 10% 90%
9.00 Non-Flammable 11 5% 95% 19.00 Non-Flammable
Based upon the above considerations and analysis, and preferred
aspects of the present invention in which the first refrigerant
consists essentially of CO2 and a second refrigerant consists
essentially of propane, it is preferred that the weight ratio of
the loading of the first refrigerant (e.g. CO2) in the low
temperature loop to the second refrigerant (e.g. propane) is
greater than 4. In such embodiments, the system of the present
invention will remain safe, i.e., contain only nonflammable
refrigerant, even in the event of complete intermixing between the
first and the second refrigerant compositions.
EXAMPLES
Comparative Example C1
[0052] Comparative Example C1 as described below is based on a
typical walk-in cooler refrigeration system as illustrated in FIG.
1.
[0053] In FIG. 1, the boundaries of the cooler are represented
schematically by the box 100. Enclosed within the cooler box is the
evaporator 15 and expander 14. Compressor 11 and condenser 20 are
located outside the cooler box 100. The refrigerant circulating
within this refrigeration loop is refrigerant R-404A (52 wt. %
R-143a, 44 wt. % R-125 and 4 wt. % R-134a).
[0054] The following operating parameters are used: [0055]
Evaporating temperature of evaporator 15=-35.degree. C. [0056]
Condensing temperature of condenser 200=45.degree. C. [0057]
Isentropic efficiency of expander 14=63% [0058] Evaporator
Superheat=5.degree. C. [0059] Temperature rise in the compressor
suction line=20.degree. C. [0060] Expansion device
subcooling=0.degree. C. The operation of this typical system
produces a compressor discharge temperature of 108.3.degree. C.
Hybrid Examples H1A-H1D
[0061] A hybrid system based on the typical refrigeration system as
illustrated in Example 1 is formed but a suction line heat
exchanger is inserted so as to absorb heat into the R-404A exiting
the evaporator and thereby increasing the temperature of R-404A
entering the compressor by absorbing heat from R-404A exiting the
condenser prior to that stream entering expander. Operation using a
suction line heat exchanger with Effectiveness values varying from
35% to 85% are evaluated. The results are reported in the following
Table H1, together with the result of comparative Example C1 for
comparison:
TABLE-US-00009 TABLE H1 C1 H1A H1B H1C H1D Effectiveness, 0 (no
heat 35 55 75 85 %* exchanger) Compressor 108.3 133.1 150.0 166.5
174.7 Discharge Temperature, .degree. C. *Effectiveness % of the
suction line heat exchanger as used herein refers to the percentage
of ideal operation with no heat loss
[0062] As can be seen from the results reported above, modifying a
typical system to include a suction line heat exchanger is not
viable since in every case there is a substantial, and unwanted and
undesirable, increase in the compressor discharge temperature as a
result of operating such a hybrid system.
Examples 1A-1E, 2A-2E, 3A-3E, 4A-4E and 5A-5E
[0063] A cascade refrigeration system having a suction line heat
exchanger as illustrated in FIG. 1 is operated using each of the
following refrigerants in the low temperature loop (the second
refrigerant): HFO-1234ze(E); HFO-1234yf; SR21 (80 wt % HFO-1234yf
and 20 wt % R-32); SR26 (80 wt % HFO-1234ze(E) and 20 wt % R-32);
and SR31 (88 wt % HFO-1234ze(E) and 12 wt % R-32). The refrigerant
in the high temperature loop is CO.sub.2. Using these refrigerants,
the cascade system of the present invention is operated according
to the following parameters: [0064] Evaporating temperature of the
low stage (evaporator 15)=-35.degree. C. [0065] Condensing
temperature of the low-stage=(cascade condenser 12A)=0.degree. C.
[0066] Evaporating temperature of the high-stage (evaporator
25)=-5.degree. C. [0067] Condensing Temperature of the high-stage
(cascade condenser 12B)=45.degree. C. [0068] Isentropic efficiency
of the low-stage expander (expander 14)=65% [0069] Isentropic
efficiency of the high-stage expander (expander 24)=63% [0070]
Evaporator Superheat (both evaporators)=5.degree. C. [0071]
Temperature rise in the suction line of the low-stage=15.degree. C.
[0072] Temperature rise in the suction line of the
high-stage=5.degree. C. [0073] Subcooling at both expansion devices
of high and low stages=0.degree. C. [0074] Suction-line Liquid-line
heat exchanger Effectiveness=vary from 0% to 85%. Table 1/5--DT
below shows the results in terms of discharge temperature for each
example, with result from Comparative Example 1 being shown for
comparison:
TABLE-US-00010 [0074] TABLE 1/5 DT C1 and 1A-5A 1B-5B 1C-5C 1D-5D
1E-5E Effectiveness, %* 0 (no heat exchanger) 35 55 75 85
Refrigerant Compressor Discharge Temperature, .degree. C. R-404A
108.3 133.1 150.0 166.5 174.7 HFO-1234ze(E) 70 87 97 106 111
(Examples 1A-1E) HFO-1234yf 65 81 91 100 105 (Examples 2A-2E) SR21
68 85 95 104 109 (Examples 3A-3E) SR26 88 102 110 117 121 (Examples
4A-4E) SR31 81 96 104 112 116 (Examples 5A-5E)
As revealed by the table above, all Examples of the present
invention satisfy the preferred compressor discharge temperatures
of the present invention, and in all cases the discharge
temperature is substantially superior to the performance of the
typical system and even the hybrid system.
[0075] Table 1/5--COP below shows the results in terms of COP for
each example, with result from Comparative Example 1 being shown
for comparison:
TABLE-US-00011 TABLE 1/5 COP C1 and 1A-5A 1B-5B 1C-5C 1D-5D 1E-5E
Effectiveness, %* 0 (no heat exchanger) 35 55 75 85 Refrigerant COP
(COP/% COP compared to Comparative Example 1) R-404A 0.89/100
HFO-1234ze(E) 1.12/125 1.14/128 1.16/130 1.17/131 1.18/132
(Examples 1A-1E) HFO-1234yf 1.07/121 1.11/125 1.13/127 1.15/129
1.16/130 (Examples 2A-2E) SR21 1.11/125 1.39/128 1.15/130 1.17/131
1.18/132 (Examples 3A-3E) SR26 1.11/125 1.13/127 1.14/128 1.15/129
1.16/130 (Examples 4A-4E) SR31 1.08/121 1.1/123 1.11/125 1.12/126
1.13/127 (Examples 5A-5E)
As revealed by the table above, all Examples of the present
invention result in improved COP of at least 121% compared to the
system of Comparative Example 1. In addition all systems of the
present invention which include a suction-line heat exchanger show
at least an additional 2% improvement versus the system of the
present invention without heat exchanger, and a systems with 55% or
higher heat exchanger effectiveness for the suction line heat
exchanger show at least an additional 3% improvement versus the
system without heat exchanger.
Examples 6A-6E, 7A-7E, 8A-8E, 9A-9E
[0076] A cascade refrigeration system having no suction line heat
exchanger and a suction line heat exchanger as illustrated in FIG.
1 is operated using each of the following refrigerants in the low
temperature loop (the second refrigerant) and CO.sub.2 in the high
temperature loop (showing the GWP of each refrigerant):
TABLE-US-00012 Component Second Refrigerant R-1234ze(E), R-32,
Designation wt % wt % GWP EX6 0 100 677 EX7 10 90 609 EX8 20 80 542
EX9 30 70 474
[0077] Using the same operating conditions identified in Examples
1-5, the system of FIG. 1 is operated with each of the refrigerants
EX6-EX9, and Table 6/9--DT below shows the results in terms of
discharge temperature for each example, with result from
Comparative Example 1 being shown for comparison:
TABLE-US-00013 TABLE 6/9 DT C1 and 6A-9A 6B-9B 6C-9C 6D-9D 6E-9E
Effectiveness, %* 0 (no heat exchanger) 35 55 75 85 Refrigerant
Compressor Discharge Temperature, .degree. C. R-404A 108 133 150
167.5 175 Examples 6A-6E) 125 145 157 168 174 Examples7A-7E) 121
140 151 162 167 Examples 7A-7E 117 136 146 156 161 Examples 7A-7E
113 130 140 150 154
[0078] As revealed by the table above, using the refrigerants
EX6-EX9 produce acceptable discharge temperatures (within the scope
of preferred discharge temperature range) for cascade systems
without a suction line heat exchanger (effectiveness=0). However,
none of the refrigerants produce acceptable discharge temperatures
(within the scope of preferred discharge temperature range) for
cascade systems for any of the values of effectiveness from 35% to
85%.
Examples 10A-10E, 11A-11E, 12A-12E, 13A-13E, 14A-14E, 15A-15E
[0079] A cascade refrigeration system having no suction line heat
exchanger and a suction line heat exchanger as illustrated in FIG.
1 is operated using each of the following refrigerants in the low
temperature loop (the second refrigerant) and CO2 in the high
temperature loop:
TABLE-US-00014 Component Second Refrigerant R-1234ze(E), R-32,
Designation wt % wt % GWP EX10 40 60 407 EX11 50 50 339 EX12 60 40
271 EX13 70 30 204 EX14 80 20 136 EX15 90 10 69
Using the same operating conditions identified in Examples 1-5, the
system of FIG. 1 is operated with each of the refrigerants
EX10-EX15, and Table 10/15--DT below shows the results in terms of
discharge temperature for each example, with result from
Comparative Example 1 being shown for comparison:
TABLE-US-00015 TABLE 10/15 DT C1 and 10B- 10C- 10D- 10E- 10A-15 15B
15C 15D 15E Effectiveness, %* 0 (no heat exchanger) 35 55 75 85
Refrigerant Compressor Discharge Temperature, .degree. C. R-404A
108 133 150 167.5 175 Examples 10A-10E 109 125 134 143 148 Examples
11-11E 104 120 128 137 141 Examples 12A-12E 100 114 122 130 134
Examples 13A-13E 94 108 116 124 128 Examples 14A-14E 88 102 110 117
121 Examples 15A-15E 81 95 103 111 115
[0080] As revealed by the table above, using the refrigerants
EX10-EX15 results in a second refrigerant with a GWP value below
500, but not each refrigerant produces an acceptable discharge
temperature (i.e., within the scope of preferred discharge
temperature range). For cascade systems without a suction line heat
exchanger (effectiveness=0), the discharge temperature is
acceptable. However, for systems with a suction line heat
exchanger, each of EX10-EX13 refrigerants produce unacceptable
discharge temperatures for the desired effectiveness values of 85%
or above. Only EX 14 and EX 15 provide acceptable discharge
temperatures for suction line heat exchangers having any of the
tested effectiveness values. These finding are summarized below:
[0081] At 35% effectiveness, greater than 30% of R1234ze(E) is
required [0082] At 55% effectiveness: greater than 50% of
R1234ze(E) is required [0083] At 75% effectiveness: greater than
60% of R1234ze(E) is required [0084] At 85% effectiveness: greater
than 70% of R1234ze(E) is required [0085] Compositions containing
at least about 78% of R-1234ze(E) are acceptable for all
effectiveness values of the suction line heat exchanger and produce
a GWP value of about 150 or less.
[0086] Table 10/15--COP below shows the results in terms of COP for
each example, with result from Comparative Example 1 being shown
for comparison:
TABLE-US-00016 TABLE 10/15 COP C1 and 10A-15A 10B-15B 10C-15C
10D-15D 10E-15E Effectiveness, %* 0 (no heat exchanger) 35 55 75 85
Refrigerant COP (COP/% COP compared to Comparative Example 1)
R-404A 0.89/100 Examples 10A-10E 1.1/123 1.11/124 1.1/124 1.1/124
1.1/124 Examples 11-11E 1.1/124 1.1/124 1.1/125 1.1/125 1.1/125
Examples 12A-12E 1.1/124 1.1/125 1.1/125 1.1/126 1.1/126 Examples
13A-13E 1.1/125 1.1/127 1.1/128 1.2/129 1.2/130 Examples 14A-14E
1.1/125 1.1/127 1.1/129 1.2/130 1.2/131 Examples 15A-15E 1.1/125
1.1/128 1.2/130 1.2/131 1.2/132
As revealed by the table above, all Examples of the present
invention result a COP of at least 121% compared to the system of
Comparative Example 1. In addition the use of the refrigerant of
Example 15 in all tested systems of the present invention which
include a suction-line heat exchanger show at least an additional
2% improvement versus the system of the present invention without
the suction-line heat exchanger, The use of the refrigerant of
Example 14 in tested systems of the present invention which include
a suction-line heat exchanger with and effectiveness of at least
55% show at least an additional 2% improvement versus the system of
the present invention without the suction-line heat exchanger and
(as shown in Table 11/15--DT) have an acceptable discharge
temperature. The use of the refrigerant of Example 13 in tested
systems of the present invention which include a suction-line heat
exchanger with and effectiveness of at least 55% but less than
about 85% show at least an additional 2% improvement versus the
system of the present invention without the suction-line heat
exchanger and (as shown in Table 11/15--DT) have an acceptable
discharge temperature.
[0087] In contrast, while the use of the refrigerant of Example 12
in tested systems of the present invention which include a
suction-line heat exchanger with an effectiveness of at least 75%
show at least an additional 2% improvement versus the system of the
present invention without the suction-line heat exchanger, as shown
in Table 11/15--DT, this refrigerant does not provide an acceptable
discharge temperature for this conditions.
Examples 16A-16E, 17A-17E, 18A-18E, 19A-19E
[0088] A cascade refrigeration system having no suction line heat
exchanger and a suction line heat exchanger as illustrated in FIG.
1 is operated using each of the following refrigerants in the high
temperature loop (the second refrigerant) and CO.sub.2 in the low
temperature loop (showing the GWP of each refrigerant):
TABLE-US-00017 Component Second Refrigerant R-1234yf, R-32,
Designation wt % wt % GWP EX16 0 100 677 EX17 10 90 609 EX18 20 80
542 EX19 30 70 474
Using the same operating conditions identified in Examples 1-5, the
system of FIG. 1 is operated with each of the refrigerants
EX16-EX19, and Table 16/19--DT below shows the results in terms of
discharge temperature for each example, with result from
Comparative Example 1 being shown for comparison:
TABLE-US-00018 TABLE 16/19 DT C1 and 16B- 16C- 16D- 16E- 16A-19A
19B 19C 19D 19E Effectiveness, %* 0 (no heat exchanger) 35 55 75 85
Refrigerant Compressor Discharge Temperature, .degree. C. R-404A
108 133 150 167.5 175 Examples16A-16E) 125 145 157 168 174
Examples17A-17E) 119 138 149 160 166 Examples 18A-18E 113 132 142
153 158 Examples 19A-19E 107 125 136 146 151
[0089] As revealed by the table above, using the refrigerants
EX16-EX19 produce acceptable discharge temperatures (within the
scope of preferred discharge temperature range) for cascade systems
without a suction line heat exchanger (effectiveness=0). However,
none of the refrigerants produce acceptable discharge temperatures
(within the scope of preferred discharge temperature range) for
cascade systems for any of the values of effectiveness from 35% to
85%.
Examples 20A-20E, 21A-21E, 22A-22E, 23A-23E, 24A-24E, 25A-25E
[0090] A cascade refrigeration system having no suction line heat
exchanger and a suction line heat exchanger as illustrated in FIG.
1 is operated using each of the following refrigerants in the low
temperature loop (the second refrigerant) and CO2 in the high
temperature loop:
TABLE-US-00019 Component Second Refrigerant R-1234ze(E), R-32,
Designation wt % wt % GWP EX20 40 60 407 EX21 50 50 339 EX22 60 40
271 EX23 70 30 204 EX24 80 20 136 EX25 90 10 69
Using the same operating conditions identified in Examples 1-5, the
system of FIG. 1 is operated with each of the refrigerants
EX20-EX25, and Tables 20/25--DT below shows the results in terms of
discharge temperature for each example, with result from
Comparative Example 1 being shown for comparison:
TABLE-US-00020 TABLE 20/25 DT C1 and 20B- 20C- 20D- 20E- 20A-25 25B
25C 25D 25E Effectiveness, %* 0 (no heat exchanger) 35 55 75 85
Refrigerant Compressor Discharge Temperature, .degree. C. R-404A
108 133 150 167.5 175 Examples 20A-20E 102 125 134 143 148 Examples
21-21E 97 113 123 132 137 Examples 22A-22E 92 107 116 125 130
Examples 23A-23E 86 102 110 119 123 Examples 24A-24E 81 96 109 112
116 Examples 25A-25E 74 89 97 105 110
[0091] As revealed by the table above, using the refrigerants
EX21-EX25 results in a second refrigerant with a GWP value below
500, but not each refrigerant produces an acceptable discharge
temperature (i.e., within the scope of preferred discharge
temperature range). For cascade systems without a suction line heat
exchanger (effectiveness=0), the discharge temperature is
acceptable. However, for systems with a suction line heat
exchanger, each of refrigerants EX20-EX22 produces unacceptable
discharge temperatures for the desired effectiveness values of 85%
or above. Only EX 23, EX24 and EX 25 provide acceptable discharge
temperatures for suction line heat exchangers for all tested
effectiveness values. These findings are summarized below: [0092]
At 35% effectiveness, greater than 30% of R1234yf is required
[0093] At 55% effectiveness: greater than 40% of R1234yf is
required [0094] At 75% and 85% effectiveness: greater than 60% of
R1234yf is required
[0095] Table 20/25--COP below shows the results in terms of COP for
each example, with result from Comparative Example 1 being shown
for comparison:
TABLE-US-00021 TABLE 20/25 COP C1 and 20A-25A 20B-25B 20C-25C
20D-25D 20E-25E Effectiveness, %* 0 (no heat exchanger) 35 55 75 85
Refrigerant COP (COP/% COP compared to Comparative Example 1)
R-404A 0.89/100 Examples 20A-20E 1.1/122 1.11/122 1.1/122 1.1/122
1.1/122 Examples21-21E 1.1/121 1.1/122 1.1/123 1.1/123 1.1/123
Examples 22A-22E 1.1/121 1.1/122 1.1/123 1.1/124 1.1/124 Examples
23A-23E 1.1/121 1.1/123 1.1/124 1.2/125 1.2/125 Examples 24A-24E
1.1/121 1.1/123 1.1/124 1.1/126 1.1/127 Examples 25A-25E 1.1/121
1.1/124 1.1/126 1.1/128 1.2/129
As revealed by the table above, all Examples of the present
invention result a COP of at least 121% compared to the system of
Comparative Example 1. In addition the use of the refrigerant of
Examples 24 and 25 in all tested systems of the present invention
which include a suction-line heat exchanger show at least an
additional 2% improvement versus the system of the present
invention without the suction-line heat exchanger, and the
refrigerant of Examples 22 and 23 shows at least an additional 2%
improvement versus the system of the present invention without the
suction-line heat exchanger for heat exchangers with effectiveness
of 55% or greater. The use of the refrigerant of Examples 22 in
tested systems of the present invention which include a
suction-line heat exchanger with an effectiveness of at least 75%
show at least an additional 2% improvement versus the system of the
present invention without the suction-line heat exchanger.
[0096] Importantly, the use of the refrigerant of Examples 24 and
25 in all tested systems of the present invention which include a
suction-line heat exchanger not only show at least an additional 2%
improvement versus the system of the present invention without the
suction-line heat exchanger, such refrigerants (as shown in Table
21/25--DT) have an acceptable discharge temperature for all levels
of suction line heat exchanger effectiveness tested. The use of the
refrigerant of Examples 22 and 23 in tested systems of the present
invention which include a suction-line heat exchanger with an
effectiveness of 55% show not only at least an additional 2%
improvement versus the system of the present invention without the
suction-line heat exchanger but (as shown in Table 21/25--DT) also
have an acceptable discharge temperature.
[0097] In contrast, while the use of the refrigerant of Example 20
does not demonstrate at least a 2% improvement for any values of
heat exchanger effectiveness, and while Examples 21 and 22 show at
least a 2% improvement for heat exchanger effectiveness values of
75% and 85%, these values of heat exchanger effectively do not does
not provide an acceptable discharge, as shown in Table 20/25--DT,
this refrigerant does not for this conditions.
* * * * *