JP7292367B2 - Low GWP cascade cooling system - Google Patents

Description

This application claims priority to provisional application 62/313,177, filed March 25, 2016, which is incorporated herein by reference in its entirety.
This application is also a continuation of, and claims priority benefit to, U.S. Application No. 15/468,292, filed March 24, 2017, which is incorporated herein by reference in its entirety.

This application also claims the priority benefit of provisional application 62/275,382, filed January 6, 2016, to co-pending U.S. application Ser. each of which is also incorporated herein by reference in its entirety).

This application also claims the priority benefit of 62/295,731, filed February 16, 2016, to co-pending U.S. application Ser. It is also a continuation-in-part application of the present invention, the entire contents of which are hereby incorporated by reference.

The present invention relates to high efficiency, low global warming potential (low GWP) air conditioning and/or cooling systems and methods of providing safe and effective cooling.

In typical air conditioning and refrigerant systems, a compressor is used to compress heat transfer vapor from a lower pressure to a higher pressure, thereby adding heat to the vapor. This added heat is generally discharged into a heat exchanger, commonly called a condenser. The heat transfer vapor introduced into the condenser is condensed to produce a relatively high pressure liquid heat transfer fluid. Condensers typically use a fluid that is available in large quantities in the ambient environment, such as ambient air, as a heat sink. Once condensed, the high pressure heat transfer fluid is subjected to a substantially isenthalpic expansion caused by passing the fluid through an expansion device or valve where it expands to a lower pressure, thereby causing a temperature drop in the fluid. The lower pressure, lower temperature heat transfer fluid from the expansion operation is then typically sent to an evaporator where it absorbs heat and evaporates in the process. This evaporation process provides cooling of the fluid or object intended to be cooled. In many conventional air conditioning and cooling applications, the fluid to be cooled is contained within a cooling area, such as the air within a conditioned living space, or the air inside a walk-in cooler or supermarket cooler or freezer. Air. After the heat transfer fluid is vaporized at low pressure in the evaporator, it is returned to the compressor where the cycle begins again.

Forming an efficient, effective and safe air conditioning system that is simultaneously environmentally friendly, i.e. has both a low GWP effect and a low ozone depletion (ODP) effect, involves a complex and interrelated set of factors and requirements. Combinations are involved. With regard to efficiency and effectiveness, it is important to operate heat transfer fluids within air conditioning and refrigeration systems with high levels of efficiency and high relative capacity. At the same time, it is important that the fluid has low values for both GWP and ODP, as the heat transfer fluid can leak into the atmosphere over time.

Applicants believe that some fluids can achieve both high levels of efficiency and effectiveness, and at the same time low levels of both GWP and ODP, but the combination of these requirements It has been found that many satisfactory fluids have the drawback of having safety deficiencies. For example, fluids that may otherwise be acceptable may be undesirable due to combustion characteristics and/or toxicity issues. Applicants have found that such flammable and/or toxic fluids are inadvertently released into cooling living spaces, walk-in coolers, cold containers, chillers, freezers, or shipping cooling containers, thereby It has been recognized that the use of fluids with such properties is particularly undesirable in conventional air conditioning systems and many refrigeration systems, as they expose or potentially expose occupants to hazardous conditions. Applicants have also come to realize that this problem is even more significant for relatively small systems, eg systems with a capacity of less than 30 kW. This is because the cost of effective security systems, such as fire suppression systems, is often not economically feasible for such systems.

According to one aspect of the invention, direct or indirect, but preferably A cascade refrigerant system is provided for providing direct refrigeration. As used herein, the term "enclosure" is at least partially defined (eg, an enclosure may be open or closed on one or more sides) and contains cooling air. means space.

A preferred aspect of the system includes at least a first evaporator located within the enclosure and being part of a first relatively low temperature heat transfer circuit. The low temperature heat transfer circuit preferably includes at least a compressor for increasing the pressure of the first heat transfer composition; a heat exchanger for condensing; an expansion device for reducing the pressure of the heat transfer composition from the condenser; and an evaporator for absorbing heat from the cooled enclosure into the heat transfer composition. A first heat transfer fluid is included in the vapor compression circulation loop. Preferably one or more, and most preferably all of such compressors, condensers and expansion valves are located outside the enclosure and the evaporator is located within the enclosure.

The system of the present invention also preferably includes a second heat transfer circuit (sometimes referred to herein for convenience as the "hot" loop) located substantially outside the enclosure. The hot loop preferably comprises at least a compressor, a heat exchanger operable to condense the heat transfer fluid in the hot loop, preferably by heat exchange with ambient air outside the enclosure, and a second compressor from the compressor. A second heat transfer fluid is included in a vapor compression circulation loop that includes an expansion device for reducing the pressure of the heat transfer fluid.

An important feature of the preferred embodiment of the present invention is that it acts as a condenser in the cryogenic circuit to expel heat into the second heat transfer fluid, preferably by evaporating at least a substantial portion of the second heat transfer fluid. The heat exchanger is thermally coupled with the high temperature circuit. Thus, the condenser of the cold circuit and the evaporator of the hot circuit are thermally coupled within this heat exchanger, sometimes referred to for convenience in the system and method of the present invention as a "cascade heat exchanger."

Another important feature of the invention in its preferred form is the transfer of heat from the second heat transfer fluid discharged from the high temperature condenser to the portion of the second heat transfer fluid that is routed to the suction side of the compressor. including the presence of a heat exchanger in the high temperature loop which has been found to advantageously and unexpectedly improve system performance by. This heat exchanger is sometimes referred to herein for convenience as the "suction line heat exchanger".

Another important feature of preferred systems is that the first heat transfer fluid circulating in the cryogenic loop comprises a refrigerant having a GWP of about 500 or less, more preferably about 400 or less, even more preferably about 150 or less. and also that the first heat transfer fluid has a significantly lower flammability than the flammability of the second heat transfer fluid. Preferably, the second heat transfer fluid circulating in the high temperature loop also comprises a refrigerant having a GWP of about 500 or less, more preferably about 400 or less, even more preferably about 150 or less, although in normal operation this heat Since the transfer fluid is never introduced into the enclosure, Applicants do not use fluids in this high temperature loop that have one or more properties that would be considered disadvantageous when circulated within the enclosure, such as flammability, toxicity, etc. It has been found to be advantageous to use in Thus, as described in detail below, the present system provides additional possible unexpected advantages over systems that rely on either the first heat transfer composition alone or the second heat transfer composition alone. becomes possible.

In some preferred embodiments, the second refrigerant is at least about 50 wt%, even more preferably at least about 75 wt% trans-1,3,3,3-trifluoropropene (HFO-1234ze(E) ) and/or HFO-1234yf, more preferably HFO-1234yf, wherein the second refrigerant has a flammability approximately greater than that of CO ₂ , preferably substantially greater. In another aspect, the second refrigerant comprises at least about 75 wt%, even more preferably at least about 80 wt% trans-1,3,3,3-trifluoropropene (HFO-1234ze(E)) and / or HFO-1234yf, more preferably these.

FIG. 1 is a generalized process flow diagram of one preferred embodiment of an air conditioning system according to the present invention.

Preferred heat transfer composition:
In each of the preferred embodiments described herein, the system comprises:
(a) a compressor, an expander, and an evaporator in fluid communication in the loop, and a first heat transfer composition in the loop comprising a first refrigerant and preferably a lubricant for the compressor; a relatively low temperature vapor compression loop (the evaporator can be placed in an enclosure containing cooling air to absorb heat from the air at approximately such relatively low temperature);
(b) a compressor, condenser, expander, and suction line heat exchanger in fluid communication in a loop, and a second refrigerant in the loop and preferably a lubricant for the compressor; (c) a relatively high temperature vapor compression loop containing a heat transfer composition (the condenser can transfer heat to a heat sink located outside the enclosure); a cascade heat exchanger for condensing the first refrigerant and evaporating the second refrigerant by heat exchange between;
includes;
A suction line heat exchanger is in fluid communication with the cascade heat exchanger for receiving at least a portion of the second heat transfer composition discharged from the cascade heat exchanger and the first heat transfer composition discharged from the condenser. of the heat transfer composition by absorbing heat from it, thereby lowering the temperature of the first heat transfer composition before it is introduced into the first loop expander. Let

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, unless otherwise indicated. are used in a relative sense to indicate the relative temperatures of the heat transfer compositions being used (here the difference between them is at least about 5°C).

Preferably, the first refrigerant has a significantly lower flammability than the second refrigerant. In a preferred embodiment, the first refrigerant has a flammability classified as A1 according to ASHRAE Standard 34 (which defines the method of measurement according to ASTM-E681) and the second refrigerant has a flammability classified as A1 according to ASHRAE Standard 34, or have a higher flammability than A2L, although the A2L classification is preferred for the second refrigerant. It is also preferred that the first and second refrigerants each have a global warming potential (GWP) of less than about 150.

In preferred embodiments, the first refrigerant circulating in the cryogenic loop comprises, preferably consists essentially of carbon dioxide, and more preferably consists of carbon dioxide in some embodiments.

The second refrigerant is trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)), 2,3,3,3-tetrafluoropropene (HFO-1234yf), R-227ea, and It is preferred to include one or more of R-32, as well as combinations of two or more thereof. In a preferred embodiment, the second refrigerant comprises at least about 50 wt%, more preferably at least about 80 wt% 2,3,3,3-tetrafluoropropene (HFO-1234yf). In other preferred embodiments, the second refrigerant is at least about 50 wt%, more preferably at least about 80 wt% or at least about 75 wt%, more preferably at least about 80 wt% trans-1,3,3 , 3-tetrafluoropropene (HFO-1234ze(E)). In highly preferred embodiments, the second refrigerant comprises at least about 95% by weight of HFO-1234ze(E), HFO-1234yf, or a combination of two or more thereof, and in some embodiments substantially from constructed or to be constructed.

In another highly preferred embodiment, the second refrigerant is about 70 wt% to about 90 wt% HFO-1234yf, preferably about 80 wt% HFO-1234yf, and about 10 wt% to about 30 wt% of R32, preferably about 20% by weight of R-32.

In another highly preferred embodiment, the second refrigerant is about 70 wt% to about 90 wt% HFO-1234ze(E), preferably about 80 wt% HFO-1234ze(E), and about 10 wt% % to about 30% by weight R-32, preferably about 20% by weight R-32.

In another highly preferred embodiment, the second refrigerant comprises from about 85% to about 90% by weight trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) and about 10% by weight % to about 15% by weight 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), even more preferably in some embodiments about 88% by weight trans-1,3 ,3,3-tetrafluoropropene (HFO-1234ze(E)) and about 12% by weight of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea).

Those of ordinary skill in the art will appreciate, in view of the disclosure contained herein, that the preferred embodiment of the present invention uses only safe (relatively low toxicity and low flammability) low GWP refrigerants in the cooling enclosure, It will be appreciated that there are advantages to using a relatively less safe but preferably low GWP refrigerant in the high temperature loop located entirely outside the enclosure.

As used herein, the terms "safe" and "relatively less safe" when used together with respect to the first and second heat transfer loops are indicated unless otherwise indicated. used in a relative sense to indicate the relative safety of heat transfer compositions. With such a configuration, the system and method of the present invention can occupy or avoid enclosures commonly encountered in walk-in freezers, supermarket coolers, etc., especially if the high temperature system includes the preferred suction line heat exchanger. It is highly preferred for use in close proximity to the human or other animal used.

Preferred embodiments of the second refrigerant are disclosed in the table below.

The first heat transfer composition and the second heat transfer composition each also generally include a lubricant in an amount generally from about 30 to about 50% by weight of the heat transfer composition, with the remainder being refrigerant and optionally present. other optional ingredients that can be used. Also, as disclosed by U.S. Pat. No. 6,516,837 (the disclosure of which is incorporated herein by reference), a combination of surfactants and solubilizers is presently used to promote oil solubility. It can also be added to the composition. Commonly used in chillers with hydrofluorocarbon (HFC) refrigerants such as polyol esters (POE) and polyalkylene glycols (PAG), silicone oils, mineral oils, alkylbenzenes (AB), and poly(α-olefins) (PAO) Any cooling lubricant that is used can be used with the refrigerant composition of the present invention. A preferred lubricant is POE.

Preferred combinations of first refrigerant, second refrigerant, and lubricant according to one aspect of the invention are provided below.

System operating conditions:
In general, it is contemplated that the operating conditions used in the present systems and methods can vary widely depending on the particular application in light of the disclosure contained herein. However, in many preferred applications operating parameters within the ranges shown in the table below are advantageously used. All these amounts are understood to be modified by "about."

When operated within the process conditions according to the present invention, use of the suction line heat exchangers described herein preferably results in at least A 2% COP improvement is obtained, more preferably at least about a 3% COP improvement, and even more preferably a 4% COP improvement.

In the following description, system components or members that are generally the same, similar, or potentially the same in different aspects are indicated using the same numerals or symbols.
One preferred cooling system is shown in FIG. This cooling system is indicated generally at 10 . A boundary, indicated generally as 100, diagrammatically shows the enclosure. The cryogenic loop includes compressor 11 , condensing side 12 A of cascade heat exchanger 12 , expansion valve 14 and evaporator 15 . As shown, evaporator 15 is disposed within enclosure 100 along with any associated conduits and other connecting devices and related equipment that transport the first heat transfer composition to and from the enclosure boundaries. . Although the evaporator 14 is preferably located inside the enclosure and is disclosed as being located inside the enclosure 100 in the drawings shown, in some embodiments the inflator 14 is located outside the enclosure. It is recognized that it may be desirable and/or necessary to provide The hot loop includes the compressor 21, the evaporating side 12B of the cascade heat exchanger 12, the expansion valve 24, and the condenser 25, all of which along with any associated conduits and other connecting devices and associated equipment are located within the enclosure 100. placed outside the The high temperature circuit also exchanges heat between a second heat transfer composition stream 30 exiting the condenser 25 and a second heat transfer composition stream 31 exiting the evaporating side 12B of the cascade heat exchanger 12. It also includes a suction line heat exchanger 50 that allows for

Although it is contemplated that the relative dimensions of the first and second cooling loops according to the present invention may vary widely within that range, Applicants have found that very advantageous results have been achieved in some aspects. We have found that this can be achieved by careful selection of the relative dimensions of the cooling loops. More specifically, it is contemplated and understood that under normal operating conditions the heat transfer compositions contained within the first and second cooling loops will never mix or intermingle. However, Applicants have come to appreciate that the potential for such intermingling of the first and second refrigerants may occur, for example, in the case of leaks in cascade heat exchangers. This mixed refrigerant flow can then become exposed to humans or other animals in or near the enclosure in the event of a leak within the enclosure being cooled. Therefore, in order to ensure continued safe operation in the event of such a leak, Applicants have determined that by carefully and judiciously selecting the relative cooling loop dimensions, a safe I've come to realize that I can get a system.

Applicants believe that the systems and compositions of the present invention will be useful in many cooling applications, but preferred applications include in enclosures such as residential living spaces, office spaces, warehouses, etc., and in walkways. Applications such as treatment of air such as cooling and/or heating associated with enclosures used to keep items cool by cooling the air within the enclosures such as in-containers, cold storage containers, shipping cooling containers, etc. cooling systems and methods for use in As used herein, the term "transport cooling vessel" is used to denote a cryogenic/insulated vessel that is located on or constitutes part or substantially all of a cargo trailer. Moreover, in preferred applications, the capacity of the system according to the invention is less than about 30 kW. In preferred applications the capacity of the system according to the invention is less than about 15 kW, and in further applications the capacity of the system according to the invention is less than about 10 kW.

Examples of some preferred systems, methods, and compositions are described below.
A. The first refrigerant is _CO2 and the second refrigerant is R-1234ze(E):
As an example, Applicants have considered a cascade cooling system according to the invention in which the first refrigerant consists of _CO2 and the second refrigerant consists of R01234ze(E). In order to achieve a refrigeration system according to the invention which is safe even in the event of mixing between the first and second refrigerants, the Applicants use various mixtures of these components (vapor and (including liquid) was determined as follows.

Based on the above discussion and analysis, and the preferred form of the present invention in which the first refrigerant consists essentially of _CO2 and the second refrigerant consists essentially of R-1234ze(E), the cryogenic loop Preferably, the weight ratio of the charge of the first refrigerant (eg, CO ₂ ) to the second refrigerant (eg, R-1234ze(E)) in the refrigerant is greater than or equal to about 1.2. In such embodiments, the system of the present invention remains safe, i.e., contains only non-flammable refrigerants, even in the event of complete mixing between the first and second refrigerant compositions. .

B. The first refrigerant is _CO2 and the second refrigerant is SR26:
As a further example, Applicants have found that the first refrigerant consists of _CO2 and the second refrigerant consists of SR26 (a combination of R-1234ze(E):R-32 in a weight ratio of 80:20). A cascade cooling system according to the present invention was considered. In order to achieve a refrigeration system according to the invention which is safe even in the event of mixing between the first and second refrigerants, the Applicants use various mixtures of these components (vapor and (including liquid) was determined as follows.

Based on the above considerations and analysis, and a preferred form of the invention in which the first refrigerant consists essentially of _CO2 and the second refrigerant consists essentially of SR26, the first Preferably, the weight ratio of the charge of refrigerant (eg, _CO2 ) to the second refrigerant (eg, SR26) is about 1.0 or greater. In such embodiments, the system of the present invention remains safe, i.e., contains only non-flammable refrigerants, even in the event of complete mixing between the first and second refrigerant compositions. .

C. The first refrigerant is _CO2 and the second refrigerant is R-32:
As a further example, Applicants have considered a cascade cooling system according to the invention in which the first refrigerant consists of CO ₂ and the second refrigerant consists of R-32. In order to achieve a refrigeration system according to the invention which is safe even in the event of mixing between the first and second refrigerants, the Applicants use various mixtures of these components (vapor and (including liquid) was determined as follows.

Based on the above considerations and analysis, and a preferred form of the invention in which the first refrigerant consists essentially of _CO2 and the second refrigerant consists essentially of SR26, the first Preferably, the weight ratio of the charge of refrigerant (eg, _CO2 ) to the second refrigerant (eg, SR26) is about 0.9 or greater. In such embodiments, the system of the present invention remains safe, i.e., contains only non-flammable refrigerants, even in the event of complete mixing between the first and second refrigerant compositions. .

D. The first refrigerant is _CO2 and the second refrigerant is ethane:
As a further example, applicants considered a cascade cooling system according to the invention in which the first refrigerant consisted of _CO2 and the second refrigerant consisted of ethane. In order to achieve a refrigeration system according to the invention which is safe even in the event of mixing between the first and second refrigerants, the Applicants use various mixtures of these components (vapor and (including liquid) was determined as follows.

Based on the above considerations and analysis, and a preferred form of the invention in which the first refrigerant consists essentially of _CO2 and the second refrigerant consists essentially of ethane, the first Preferably, the weight ratio of the charge of refrigerant (eg, _CO2 ) to the second refrigerant (eg, SR26) is about 1.7 or greater. In such embodiments, the system of the present invention remains safe, i.e., contains only non-flammable refrigerants, even in the event of complete mixing between the first and second refrigerant compositions. .

E. The first refrigerant is _CO2 and the second is propane:
As a further example, Applicants have considered a cascade cooling system according to the invention in which the first refrigerant consists of _CO2 and the second refrigerant consists of propane. In order to achieve a refrigeration system according to the invention which is safe even in the event of mixing between the first and second refrigerants, the Applicants use various mixtures of these components (vapor and (including liquid) was determined as follows.

Based on the above discussion and analysis, and a preferred form of the invention in which the first refrigerant consists essentially of _CO2 and the second refrigerant consists essentially of propane, the first Preferably, the weight ratio of the charge of refrigerant (eg CO ₂ ) to the second refrigerant (eg propane) is greater than four. In such embodiments, the system of the present invention remains safe, i.e., contains only non-flammable refrigerants, even in the event of complete mixing between the first and second refrigerant compositions. .

Comparative Example C1:
Comparative Example C1, described below, is based on a conventional walk-in cooler cooling system shown in the following figures.

In the above figures, the boundaries of the cooler are diagrammatically indicated by a rectangle 100 . An evaporator 15 and an expander 14 are accommodated in the cooler container. A compressor 11 and a condenser 20 are arranged outside the cooler vessel 100 . The refrigerant circulating in this refrigeration loop is refrigerant R-404A (52% by weight R-143a, 44% by weight R-125, and 4% by weight R-134a).

The following operating parameters were used.
Evaporation temperature of evaporator 15 = -35°C;
Condensation temperature of condenser 200 = 45°C;
the isentropic efficiency of the expander 14 = 63%;
Evaporator superheat = 5°C;
- temperature rise in the compressor suction line = 20°C;
• Expansion unit subcooling = 0°C.

This normal system operation produced a compressor discharge temperature of 108.3°C.
Composite Examples H1A-H1D:
Based on the conventional cooling system shown in Example 1, but inserting a suction line heat exchanger to absorb heat in the R-404A exiting the evaporator, thereby introducing flow to the expander. A combined system was formed to raise the temperature of the R-404A entering the compressor by absorbing heat from the R-404A previously discharged from the condenser. Operation with suction line heat exchangers with Effectiveness values varying from 35% to 85% was evaluated. The results are reported in Table H1 below along with the results of Comparative Example C1 for comparison.

As can be seen from the results reported above, modifying a conventional system to include a suction line heat exchanger will, in all cases, result in a substantial reduction in compressor discharge temperature and Not feasible due to undesirable rise.

Examples 1A-1E, 2A-2E, 3A-3E, 4A-4E, and 5A-5E:
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), respectively (second refrigerant), to achieve the suction line heat shown in FIG. A cascade cooling system with exchangers was operated. The refrigerant in the hot loop was _CO2 . Using these refrigerants, the cascade system of the present invention was operated according to the following parameters.

Evaporation temperature of low temperature stage (evaporator 15) = -35°C;
Cold stage condensation temperature = (cascade condenser 12A) = 0°C;
Evaporation temperature of the hot stage (evaporator 25) = -5°C;
High temperature stage condensation temperature (cascade condenser 12B) = 45°C;
the isentropic efficiency of the cold stage expander (expander 14) = 65%;
the isentropic efficiency of the hot stage expander (expander 24) = 63%;
Evaporator superheat (both evaporators) = 5°C;
- temperature rise in the intake line of the cold phase = 15°C;
- Temperature rise in suction line for hot phase = 5°C;
- Subcooling in expansion device for both hot and cold stages = 0°C;
• Suction line liquid line heat exchanger efficiency = variable from 0% to 85%.

Table 1/5-DT below shows the results in terms of discharge temperature for each example, with the results from Comparative Example 1 shown for comparison.

As shown by the above table, all embodiments of the present invention meet the preferred compressor discharge temperatures of the present invention, and in all cases the discharge temperature is substantially below normal and even combined system performance. was excellent.

Table 1/5-COP below shows the results in terms of COP for each example, with the results from Comparative Example 1 shown for comparison.

As shown by the table above, all examples of the present invention provided an improved COP of at least 121% compared to the Comparative Example 1 system. Additionally, all systems of the invention that include a suction line heat exchanger show at least an additional 2% improvement over systems of the invention without a heat exchanger, and over 55% more heat with respect to the suction line heat exchanger. Systems with exchanger efficiency showed at least an additional 3% improvement over systems without heat exchangers.

Examples 6A-6E, 7A-7E, 8A-8E, 9A-9E:
Cascade refrigeration system without and with suction line heat exchanger shown in FIG. 1 with each of the following refrigerants (second refrigerant) in the cold loop and _CO2 in the hot loop: were operated (indicating the GWP of each refrigerant).

Using the same operating conditions as shown in Examples 1-5, the system of FIG. Perspective results are shown and the results from Comparative Example 1 are shown for comparison.

As shown by the table above, refrigerants EX6-EX9 produced acceptable discharge temperatures (within the preferred discharge temperature range) for a cascade system without a suction line heat exchanger (efficiency = 0). . However, none of the refrigerants produced acceptable discharge temperatures (within the preferred discharge temperature range) for the cascade system for any efficiency value between 35% and 85%.

Examples 10A-10E, 11A-11E, 12A-12E, 13A-13E, 14A-14E, 15A-15E:
Cascade refrigeration system without and with suction line heat exchanger shown in FIG. 1 with each of the following refrigerants (second refrigerant) in the cold loop and _CO2 in the hot loop: drove the

Using the same operating conditions as shown in Examples 1-5, the system of FIG. Perspective results are shown and the results from Comparative Example 1 are shown for comparison.

As shown by the table above, using refrigerants EX10-EX15 resulted in a second refrigerant with a GWP value lower than 500, but each refrigerant had an acceptable discharge temperature (i.e., within the preferred discharge temperature range). within range). For the cascade system with no suction line heat exchanger (efficiency=0), the discharge temperature was acceptable. However, for systems with suction line heat exchangers, each of the EX10-EX13 refrigerants produced unacceptable discharge temperatures for desirable efficiency values of 85% or greater. Only the EX14 and EX15 refrigerants gave acceptable discharge temperatures for suction line heat exchangers with any of the efficiency values tested. These findings are summarized below.

• At 35% efficiency, more than 30% of R1234ze(E) was required.
• At 55% efficiency: more than 50% of R1234ze(E) was required.
• At 75% efficiency: more than 60% of R1234ze(E) was required.

• At 85% efficiency: more than 70% of R1234ze(E) was required.
• Compositions containing at least about 78% R-1234ze(E) were acceptable for all suction line heat exchanger efficiency values, producing GWP values of about 150 or less.

Table 11/15-COP below shows the results in terms of COP for each example, with the results from Comparative Example 1 shown for comparison.

As shown by the above table, all of the inventive examples provided a COP of at least 121% compared to the Comparative Example 1 system. Moreover, in all of the tested systems of the present invention that included a suction line heat exchanger, using the refrigerant of Example 15 provided at least an additional 2% improvement over systems of the present invention that did not have a suction line heat exchanger. shown. Using the refrigerant of Example 14 in a tested system of the present invention containing a suction line heat exchanger with an efficiency of at least 55%, the At least an additional 2% improvement was shown over the system of the present invention which did not have acceptable discharge temperatures. Using the refrigerant of Example 13 in a tested system of the present invention comprising a suction line heat exchanger having an efficiency of at least 55% but less than about 85% (as shown in Table 11/15-DT) At least an additional 2% improvement was shown over the system of the present invention without the suction line heat exchanger and had acceptable discharge temperatures.

In contrast, using the refrigerant of Example 12 in a tested system of the present invention comprising a suction line heat exchanger with an efficiency of at least 75%, the suction This refrigerant did not provide acceptable discharge temperatures for this condition, although an improvement of at least an additional 2% was shown over the system of the present invention without the line heat exchanger.

Examples 16A-16E, 17A-17E, 18A-18E, 19A-19E:
Cascade refrigeration systems without and with suction line heat exchangers shown in Figure 1 with each of the following refrigerants (second refrigerant) in the hot loop and _CO2 in the cold loop: were operated (indicating the GWP of each refrigerant).

Using the same operating conditions as shown in Examples 1-5, the system of FIG. Perspective results are shown and the results from Comparative Example 1 are shown for comparison.

As shown by the table above, using refrigerants EX16-EX19 produced acceptable discharge temperatures (within the preferred discharge temperature range) for a cascade system without a suction line heat exchanger (efficiency = 0). bottom. However, none of the refrigerants produced acceptable discharge temperatures (within the preferred discharge temperature range) for the cascade system for any efficiency value between 35% and 85%.

Examples 20A-20E, 21A-21E, 22A-22E, 23A-23E, 24A-24E, 25A-25E:
Cascade refrigeration system without and with suction line heat exchanger shown in FIG. 1 with each of the following refrigerants (second refrigerant) in the cold loop and _CO2 in the hot loop: drove the

Using the same operating conditions as shown in Examples 1-5, the system of FIG. Perspective results are shown and the results from Comparative Example 1 are shown for comparison.

As shown by the table above, using refrigerants EX21-EX25 resulted in a second refrigerant with a GWP value lower than 500, but each refrigerant had an acceptable discharge temperature (i.e., within the preferred discharge temperature range). within range). For the cascade system with no suction line heat exchanger (efficiency=0), the discharge temperature was acceptable. However, for systems with suction line heat exchangers, refrigerants EX20-EX22 each produced unacceptable discharge temperatures for desirable efficiency values of 85% or greater. Only EX23, EX24, and EX25 gave acceptable discharge temperatures for the suction line heat exchangers for all efficiency values tested. These findings are summarized below.

• At 35% efficiency, more than 30% of R1234yf was required.
• At 55% efficiency: more than 40% of R1234yf was required.
• At 75% and 85% efficiency: more than 60% of R1234yf was required.

Table 20/25-COP below shows the results in terms of COP for each example, with the results from Comparative Example 1 shown for comparison.

As shown by the above table, all of the inventive examples provided a COP of at least 121% compared to the Comparative Example 1 system. Additionally, in all of the tested systems of the present invention that included a suction line heat exchanger, using the refrigerants of Examples 24 and 25 resulted in at least an additional 2% reduction over systems of the present invention that did not have a suction line heat exchanger. An improvement was shown, with the refrigerants of Examples 22 and 23 showing at least an additional 2% improvement over the system of the invention without the suction line heat exchanger for heat exchangers with efficiencies of 55% or greater. . Using the refrigerant of Example 22 in a tested system of the present invention containing a suction line heat exchanger with an efficiency of at least 75% yields an efficiency of at least 2% more than a system of the present invention without a suction line heat exchanger. showed improvement.

Importantly, using the refrigerants of Examples 24 and 25 in all of the tested systems of the invention that included a suction line heat exchanger resulted in at least an additional % improvement, such refrigerants gave acceptable discharge temperatures for all levels of suction line heat exchanger efficiency tested (as shown in Table 21/25-DT). Using the refrigerants of Examples 22 and 23 in a tested system of the invention containing a suction line heat exchanger with an efficiency of 55% yields at least an additional 2% improvement over a system of the invention without a suction line heat exchanger. not only did it show an improvement in , but it also gave an acceptable jetting temperature (as shown in Table 21/25-DT).

In contrast, using the refrigerant of Example 20 showed no improvement of at least 2% for any value of heat exchanger efficiency, and Examples 21 and 22 showed heat exchanger efficiencies of 75% and 85%. Although showing an improvement of at least 2% with respect to the value of , these heat exchanger efficiency values did not give acceptable discharge as shown in Table 20/25-DT and this refrigerant was satisfactory with respect to this condition. didn't.
The present invention includes the following embodiments.
(1) (a) a compressor, an expander, and an evaporator in fluid communication within the loop, and a first heat transfer composition in the loop comprising a lubricant for the first refrigerant and the compressor; a relatively low temperature vapor compression loop comprising an evaporator disposed within the enclosure capable of absorbing heat from the fluid within the enclosure at approximately such relatively low temperature;
(b) a compressor, condenser, expander, and suction line heat exchanger in fluid communication in a loop, and a second refrigerant in the loop and preferably a lubricant for the compressor; a relatively high temperature vapor compression loop containing a heat transfer composition (the condenser can transfer heat to a heat sink located outside the enclosure); and
(c) a cascade heat exchanger for condensing the first refrigerant and evaporating the second refrigerant by heat exchange between the first and second refrigerants;
includes;
A suction line heat exchanger is in fluid communication with the cascade heat exchanger for receiving at least a portion of the second heat transfer composition discharged from the cascade heat exchanger and the first heat transfer composition discharged from the condenser. of the heat transfer composition by absorbing heat from it, thereby lowering the temperature of the first heat transfer composition before it is introduced into the first loop expander. A heat transfer system for cooling the contents of the enclosure to allow
(2) the first refrigerant has a flammability classified as A1 under ASHRAE-34 (as measured by ASTM-E681) and the second refrigerant has a flammability classified as A1 under ASHRAE-34 (as measured by ASTM-E681); th) The system of (1) having a flammability classified as A2L or higher than A2L.
(3) The system of (1), wherein each of the compressor and expander and condenser is not located within an enclosure.
(4) The system of (5), wherein the suction line heat exchanger is not located within the enclosure.
(5) the second refrigerant is trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)), 2,3,3,3-tetrafluoropropene (HFO-1234yf), R- 227ea, R-32, and combinations of two or more thereof.
(6) The system of (1), wherein the second refrigerant comprises at least about 80% by weight of 2,3,3,3-tetrafluoropropene (HFO-12304yf).
(7) The system of (1), wherein the second refrigerant consists essentially of HFO-1234ze(E), HFO-1234yf, or combinations thereof.
(8) The system of (1), wherein the second refrigerant comprises about 70 wt% to about 90 wt% HFO-1234yf and about 10 wt% to about 30 wt% R32.
(9) The system of (1), wherein the second refrigerant comprises about 70% to about 90% by weight HFO-1234yze (E) and about 10% to about 30% by weight R32.
(10) the second refrigerant comprises from about 85% to about 90% by weight trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)) and from about 10% to about 15% by weight; % 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea).

Claims (10)

A heat transfer system comprising an enclosure for cooling the contents of the enclosure, said system further comprising:
(a) a compressor, an expander, and an evaporator in fluid communication in a loop and a first heat transfer composition in a loop comprising a first refrigerant and a lubricant for the compressor; a low temperature vapor compression loop, wherein the evaporator is located within the enclosure and is capable of absorbing heat from the fluid within the enclosure at such relatively low temperature, the first refrigerant substantially consisting of carbon;
(b) a compressor, condenser, expander, and suction line heat exchanger in fluid communication in a loop and a second heat transfer composition in a loop comprising a second refrigerant ; A high temperature vapor compression loop, where the condenser can transfer heat to a heat sink located outside the enclosure, and the second refrigerant has a flammability greater than that of _CO2 ; c) a cascade heat exchanger for condensing the first refrigerant and evaporating the second refrigerant by heat exchange between the first and second refrigerants;
includes;
A suction line heat exchanger is in fluid communication with the cascade heat exchanger for receiving at least a portion of a second heat transfer composition discharged from the cascade heat exchanger and a second heat transfer composition discharged from the condenser. of the second heat transfer composition by absorbing heat from the heat transfer composition of the second heat transfer composition, thereby raising its temperature, before the second heat transfer composition is introduced into the relatively high temperature vapor compression loop expander. lowering the temperature of the composition,
the capacity of the system is less than 30 kW, and
The second refrigerant consists essentially of R-1234ze(E) and the weight ratio of the charge of the first refrigerant to the second refrigerant in the cryogenic loop is 1.5 . is 2 or more; or
The second refrigerant consists essentially of R-1234ze(E) and R-32, and the weight ratio of the loading of the first refrigerant to the second refrigerant in the cryogenic loop is 1.5 . is 0 or more; or
The second refrigerant consists essentially of R-32 and the weight ratio of the charge of the first refrigerant to the second refrigerant in the cryogenic loop is 0.5 . is 9 or more; or
A heat transfer system wherein the second refrigerant comprises 70 wt% to 90 wt% HFO-1234yf and 10 wt% to 30 wt% R32. 2. The system of claim 1, wherein each of the compressor and expander and condenser are not located within an enclosure. 3. The system of claim 1, wherein the enclosure is used to keep items cool by cooling the air within the enclosure and is selected from walk-in containers, cold storage containers, and shipping cold containers. 4. A system according to any preceding claim, wherein the capacity of the system is less than 15 kW. 5. A system according to any preceding claim, wherein the capacity of the system is less than 10 kW. The second refrigerant consists essentially of R-1234ze(E) and the weight ratio of the charge of the first refrigerant to the second refrigerant in the cryogenic loop is 1.5 . 6. A system according to any preceding claim, wherein there are two or more. The second refrigerant consists essentially of R-1234ze(E) and R-32, and the weight ratio of the loading of the first refrigerant to the second refrigerant in the cryogenic loop is 1.5 . 6. The system according to any one of claims 1 to 5, which is 0 or more. The second refrigerant consists essentially of R-32, and the weight ratio of the charge of the first refrigerant to the second refrigerant in the cryogenic loop is 0.5 . 6. The system of any of claims 1-5, wherein there are 9 or more. A system according to any preceding claim, wherein the second refrigerant comprises 70 wt% to 90 wt% HFO-1234yf and 10 wt% to 30 wt% R32. 10. A system according to any preceding claim, wherein the second heat transfer composition further comprises a lubricant for the compressor.

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