WO2014134821A1

WO2014134821A1 - Low gwp heat transfer compositions including co2

Info

Publication number: WO2014134821A1
Application number: PCT/CN2013/072337
Authority: WO
Inventors: Jun Lu; Rajiv Ratna Singh; Zhili Lu; Christopher J. Seeton; Yong Zhou; Ronny WANG; Yun Lin
Original assignee: Honeywell International Inc.
Priority date: 2013-03-08
Filing date: 2013-03-08
Publication date: 2014-09-12
Also published as: CN105164226A

Abstract

Disclosed are heat transfer compositions and methods wherein the compositions include CO2; one or more additional components selected from R-116, R-23, a C1-C5 substituted or unsubstituted, saturated or unsaturated hydrocarbon (other than R-116, R-23), a noble gas or combinations thereof. Such compositions, in certain aspects of the invention, may be used as a replacement refrigerant for R-508B, particularly, though not exclusively, in low or ultralow temperature refrigeration applications.

Description

LOW GWP HEAT TRANSFER COMPOSITIONS INCLUDING CO2

FIELD OF THE INVENTION

[0001] This invention relates to compositions, methods and systems having utility particularly in refrigeration applications, and in certain aspects to refrigerant compositions particularly useful in systems that have heretofore typically utilized the refrigerant R-508B, particularly as a refrigerant in low or ultra low temperature applications.

BACKGROUND

[0002] Mechanical refrigeration systems, and related heat transfer devices such as heat pumps and air conditioners, using refrigerant liquids are well known in the art for industrial, commercial and domestic uses. Fluorocarbon based fluids have found widespread use in many residential, commercial and industrial applications, including as the working fluid in systems such as air conditioning, heat pump and refrigeration systems. Because of certain suspected environmental problems, including the relatively high global warming potentials associated with the use of some of the compositions that have heretofore been used in these applications, it has become increasingly desirable to use fluids having low or even zero ozone depletion potential, such as hydrofluorocarbons ("HFCs"). Furthermore, a number of governments have signed the Kyoto Protocol to protect the global environment setting forth a reduction of CO₂ emissions (global warming). Thus, there is a need for a low- or non-flammable, non-toxic alternative to replace certain of high global warming HFCs.

[0003] One important type of refrigeration system is known as a "low temperature refrigeration system" or "ultralow temperature refrigeration system." Such systems typically require an evaporating temperature of at or below -20°C, in certain instance at or below -40°C, and in further instances at or below -80°C. In such low temperature refrigeration systems a commonly used refrigerant liquid has been R-508B (a

combination of HFC-23 : HFC-1 16 in an approximate ratio of 46:54 weight ratio). This refrigerant, however, has a very high global warming potential (GWP=13,396), which is considerably higher than is desired and/or required. As global warming is more and more a concern, the refrigeration industry is looking for solution with low or reduced GWP for every segment.

[0004] There has, thus, been an increasing need for new compounds and compositions that are attractive alternatives to the compositions heretofore used in these and other applications. It is generally considered important, however, at least with respect to heat transfer fluids, that any potential substitute must also possess those properties present in many of the most widely used fluids, such as excellent heat transfer properties, chemical stability, low- or no- toxicity, low flammability and/or lubricant compatibility, among others.

[0005] With regard to efficiency in use, it is important to note that a loss in refrigerant thermodynamic performance or energy efficiency may have secondary environmental impacts through increased fossil fuel usage arising from an increased demand for electrical energy.

[0006] Furthermore, it is generally considered desirable for refrigerant substitutes to be effective without major engineering changes to conventional vapor compression technology currently used with existing refrigerants.

[0007] Flammability is another important property for many applications. That is, it is considered either important or essential in many applications, including particularly in heat transfer applications, to use compositions which are non-flammable or have only mild flammability. Thus, it is frequently beneficial to use in such compositions compounds which are mildly flammable, or even less flammable than mildly flammable. As used herein, the term "mildly flammable" refers to compounds or compositions which are classified as being 2L in accordance with ASHRAE standard 34 dated 2010, incorporated herein by reference.

[0008] To date, there has been no single molecule which has been shown to meet all the requirements for R-508B replacement, including (but not limited to)

nonflammability, good volumetric cooling capacity, good cooling efficiency, low GWP, and acceptable discharge temperature. Accordingly, Applicants have come to appreciate a need for compositions, and particularly heat transfer compositions that are highly advantageous in vapor compression heating and cooling systems and methods, particularly low and ultra low temperature refrigerant systems, including systems designed for use with R-508B.

SUMMARY OF THE INVENTION

[0009] Applicants have found that the above-noted need, and other needs, can be satisfied according to one aspect of the invention by compositions, methods, uses and systems which comprise or utilize a multi-component mixture comprising: (a) CO2 as a first component; (b) a second component selected from the group consisting of R-1 16, R-23, or combinations thereof; and (c) optionally, a third component selected from the group consisting of a C1 -C5 substituted or unsubstituted, saturated or unsaturated hydrocarbon (other than a compound of component (b)), a noble gas or combinations thereof. Compositions of the present invention, in certain preferred embodiments, have a GWP below that of R-508A. In certain aspects, the GWP is below 10,000, below 7,500, or in certain preferred aspect, below 5,000.

[0010] In certain non-limiting aspects, the third component includes a saturated, unsubstituted, C1 -C5 straight or branched chain alkane (such as, but not limited to, ethane) and/or a C1 -C5 straight or branched chain alkene (such as, but not limited to, vinylidene fluoride). In certain other non-limiting aspect, the third component comprises a noble gas (such as by not limited to xenon).

[001 1 ] Component (a) may be provided in an amount from about 10 wt. % to about 90 wt. %, or in certain embodiments from about 35 wt. % to about 85 wt. %, based on the total weight of components (a)-(c). Unless otherwise indicated herein, the term "% by weight" refers to the weight percent based on the total of the components (a) - (c) in the composition.

[0012] Component (b) may be provided in an amount from about 5 wt. % to about 50 wt. %, or in an amount from about 20 wt. % to about 40 wt. %, or in an amount from about 10 wt. % to about 30 wt. %, based on the total weight of components (a)-(c).

[0013] Component (c) may be provided in an amount from about 5 wt. % to about 35 wt. %, or in an amount from about 5 wt. % to about 30 wt. %, based on the total weight of components (a)-(c).

[0014] In further non-limiting embodiments, the present invention includes compositions, methods, uses and systems which comprise or utilize a multi-component mixture comprising: (a) C02 as a first component; (b) a second component selected from the group consisting of R-1 16, R-23, or combinations thereof; and (c) optionally, a third component selected from the group consisting of ethane, vinylidene fluoride, xenon, and combinations thereof. [0015] In certain aspects of the foregoing, component (b) consists essentially of

R-1 16 and said component (c) comprises ethane. In such embodiments, C02 may be provided in an amount from about 55 wt.% to about 90 wt.%; R-1 16 may be provided in an amount from about 5 wt. % to about 30 wt. %; and ethane may be provided in an amount from about 5 wt. % to about 15 wt. %.

[0016] In further aspects of the foregoing, component (b) consists essentially of

R-1 16 and said component (c) comprises xenon. In such embodiments, C02 may be provided in an amount from about 10 wt.% to about 75 wt.%; R-1 16 may be provided in an amount from about 20 wt. % to about 45 wt. %; and xenon may be provided in an amount from about 5 wt. % to about 65 wt. %.

[0017] In further aspects of the foregoing, component (b) consists essentially of

R-1 16 and said component (c) comprises vinylidene fluoride. In such embodiments, C02 may be provided in an amount from about 30 wt.% to about 70 wt.%; R-1 16 may be provided in an amount from about 20 wt. % to about 40 wt. %; and vinylidene fluoride may be provided in an amount from about 10 wt. % to about 30 wt. %.

[0018] In further aspects of the foregoing, component (b) consists essentially of

R-23 and said component (c) comprises ethane. In such embodiments, C02 may be provided in an amount from about 30 wt.% to about 75 wt.%; R-23 may be provided in an amount from about 10 wt. % to about 40 wt. %; and ethane may be provided in an amount from about 5 wt. % to about 30 wt. %.

[0019] In further aspects of the foregoing, component (b) consists essentially of

R-23 and said component (c) comprises vinylidene fluoride. In such embodiments, C02 may be provided in an amount from about 50 wt.% to about 90 wt.%; R-23 may be provided in an amount from about 5 wt. % to about 25 wt. %; and vinylidene fluoride may be provided in an amount from about 5 wt. % to about 25 wt. %.

[0020] In further non-limiting embodiments, the present invention includes compositions, methods, uses and systems which comprise or utilize a multi-component mixture comprising: (a) C02 as a first component; and (b) a second component selected from the group consisting of R-1 16, R-23, or combinations thereof. In certain aspects of the foregoing, C02 is provided in an amount from about 50 wt.% to about 80 wt.% and R-1 16 is provided in an amount from about 20 wt. % to about 50 wt. %. In further aspects of the foregoing, C02 is provided in an amount from about 70 wt.% to about 90 wt.% and R-23 is provided in an amount from about 10 wt. % to about 30 wt. %.

[0021] In even further non-limiting embodiments, the present invention includes compositions, methods, uses and systems which comprise or utilize a multi-component mixture comprising: (a) C02 as a first component; and (b) a second component selected from the group consisting of R-1 16, R-23, a C1 -C5 substituted or unsubstituted, saturated or unsaturated hydrocarbon (other than R-1 16, R-23), a noble gas or combinations thereof. In certain aspects, component (b) comprises a saturated, unsubstituted, C1 -C5 straight or branched chain alkane (such as, but not limited to, ethane), and/or a C1 -C5 straight or branched chain alkene, which is optionally substituted with one or more substituent groups (such as, but not limited to, VDF). In certain other non-limiting aspect, the second component comprises a noble gas (such as, but not limited to, xenon).

[0022] In such embodiments, component (a) may be present in the composition in an amount from about 10 wt. % to about 90 wt. %, or in an amount from about 35 wt. % to about 85 wt. %, based on the total weight of components (a)-(b). Component (b) may be present in the composition in an amount from about 10 wt. % to about 90 wt. %, or in an amount from about 15 wt. % to about 65 wt. %, based on the total weight of components (a)-(b).

[0023] In even further non-limiting embodiments, the present invention includes compositions, methods, uses and systems which comprise or utilize a multi-component mixture comprising: (a) CO2 as a first component; and (b) a second component selected from the group consisting of R-1 16, R-23, ethane, vinyldiene fluoride, xenon, and combinations thereof.

[0024] In such embodiments, said component (a) may be present in the composition in an amount from about 10 wt. % to about 90 wt. %, or in an amount from about 35 wt. % to about 85 wt. %, based on the total weight of components (a)-(b).

Component (b) may be present in the composition in an amount from about 10 wt. % to about 90 wt. %, based on the total weight of components (a)-(b).

[0025] In embodiments where component (b) comprises R-1 16, it may be present in the composition in an amount from about 15 wt. % to about 65 wt. %, based on the total weight of components (a)-(b).

[0026] In embodiments where component (b) comprises, consists essentially of, or consists of xenon, xenon may be provided in an amount from about 10 wt.% to about 90 wt.%, in an amount from about 15 wt.% to about 85 wt.%, or in an amount from about 25 wt.% to about 70 wt.%, based on the total weight of components (a)-(b).

[0027] In embodiments where component (b) comprises, consists essentially of, or consists of ethane, ethane may be provided in an amount from about 10 wt.% to about 90 wt.%, may be provided in an amount from about 15 wt.% to about 65 wt.%, or in an amount from about 20 wt.% to about 60 wt.%, based on the total weight of components (a)-(b).

[0028] In embodiments where component (b) comprises, consists essentially of, or consists of vinylidene fluoride, vinylidene fluoride may be provided in an amount from about 10 wt.% to about 90 wt.%, in an amount from about 15 wt.% to about 65 wt.%, or in an amount from about 20 wt.% to about 60 wt.%, based on the total weight of components (a)-(b).

[0029] The present invention provides also methods, uses and systems which utilize the compositions of the present invention, including methods, uses and systems for heat transfer and for retrofitting existing heat transfer systems. Certain preferred method aspects of the present invention relate to methods of providing relatively low or ultralow temperature cooling, such as in low or ultralow temperature refrigeration systems. Other method aspects of the present invention provide methods of retrofitting an existing low temperature refrigeration system designed to contain or containing R-508B refrigerant comprising withdrawing R-508B from the system and/or introducing a composition of the present invention into the system without substantial engineering modification of said existing refrigeration system.

BRIEF DESCRIPTION OF THE FIGURES

[0030] FIG. 1 illustrates a phase diagram of CO₂A DF blend.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0031] As noted above, low and ultra low temperature refrigeration systems are important in many applications, such as to the medical industry or other applications where temperatures less than -20°C, -40°C, or -80°C are important. In such low temperature refrigeration systems, one of the refrigerant liquids which has been commonly used has been R-508B. This composition has an estimated Global Warming Potential (GWP) of about 13,000, which is much higher than is desired or required.

[0032] To date, there is no single molecule which can meet all the requirements including non-flammability, good volumetric cooling capacity, good cooling efficiency, low GWP, and acceptable discharge temperature. Potential components which have a suitable boiling point include R-1 16 (hexafluoroethane), R-23 (trifluoromethane), vinylidene fluoride (VDF or R1 132a), xenon, or ethane. However, all of these compounds, individually, have one or more weaknesses. For example, VDF and ethane are highly flammable; R1 16 and R23 have very high GWP; and xenon is expensive and has high discharge temperature.

[0033] CO₂ (carbon dioxide) is not considered as a working fluid, alone, for this low temperature range because its triple point temperature is -56.5 °C. Thus, it forms solid and blocks the evaporator coils when operating at ultralow temperature conditions.

[0034] Applicants have found that the compositions of the present invention satisfy in an exceptional and unexpected way the need for new compositions for low temperature applications having improved performance with respect to environmental impact while at the same time providing other important performance characteristics, such as capacity, efficiency, flammability and toxicity. More specifically, Applicants to the present invention, have surprisingly and unexpectedly discovered several blends, which may include one or more of the foregoing components, that have a GWP of less than 5000 (more than 60% reduced comparing with R508B). In certain preferred embodiments, Applicants have surprisingly and unexpectedly discovered that certain blends of other molecules with CO₂ reduce the freezing point of CO₂ down to lower than those required for an ultralow temperature applications - i.e. below -20 °C, preferably below -40 °C, and even more preferably below about -80 °C. Such blends are further demonstrated herein to surprisingly and expectedly provide low GWP, flammability suppression, high capacity and low cost, and in preferred embodiments of the present compositions provide alternatives and/or replacements for refrigerants currently used in ultralow temperature applications, particularly and preferably R-508B.

HEAT TRANSFER COMPOSITIONS

[0035] The compositions of the present invention are generally adaptable for use in heat transfer applications, that is, as a heating and/or cooling medium, but are particularly well adapted for use, as mentioned above, in low or ultralow temperature refrigeration systems that have heretofor used R-508B.

[0036] Applicants have found that use of the components of the present invention within the stated ranges achieves the important but difficult to obtain combinations of properties exhibited by the present compositions, particularly in the preferred systems and methods, and that use of these same components but substantially outside of the identified ranges can have a deleterious effect on one or more of the important properties of the compositions of the invention.

[0037] In certain preferred embodiments, compositions of the present invention comprise, consist essentially of, or consist of: (a) CO2 as a first component; (b) a second component selected from the group consisting of R-1 16, R-23, a C1 -C5 substituted or unsubstituted, saturated or unsaturated hydrocarbon (other than R-1 16, R-23), a noble gas or combinations thereof. In certain aspects, the hydrocarbon comprises a C1 -C5 straight or branched chain alkane. In certain preferred aspects, the hydrocarbon comprises, consists essentially of, or consists of ethane. In alternative (or additional embodiments), the hydrocarbon comprises a C1 -C5 straight or branched chain alkene, which may be optionally substituted with one or more substituent groups, which in certain embodiments includes one or more halogen atoms. Examples of such compounds include, but are not limited to vinylidene fluoride (VDF), ethylene, or propylene. In certain preferred aspects, the hydrocarbon comprises, consists essentially of, or consists of vinylidene fluoride. Noble gases may include helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). In certain preferred aspects, the noble gas comprises, consists essentially of, or consists of xenon.

[0038] In certain preferred embodiments, such compositions may comprise, consist essentially of, or consist of: (a) CO2 as a first component; (b) a second component selected from the group consisting of R-1 16, R-23, ethane, vinylidene fluoride, ethylene, propylene, xenon, or combinations thereof. In further preferred embodiments, such compositions may comprise, consist essentially of, or consist of: (a) CO2 as a first component; (b) a second component selected from the group consisting of R-1 16, R-23, ethane, vinylidene fluoride, xenon, or combinations thereof.

[0039] CO2 may be provided in an amount of from about 10 wt.% to about 90 wt.% by weight of the compositions, in certain preferred aspects in an amount of from about 35 wt.% to about 85 wt.% by weight of the compositions, and in further preferred aspects in an amount of from about 40 wt.% to about 80 wt.% by weight of the compositions.

[0040] The second component, whether one component, individually, or a combination of components provided herein may be provided in an amount of from about 10 wt.% to about 90 wt.% by weight of the compositions, in certain preferred aspects in an amount of from about 15 wt.% to about 65 wt.% by weight of the compositions or from about 20 wt.% to about 60 wt.% by weight of the compositions.

[0041] R-1 16 individually, R-23 individually, or a combination of both, may be provided in an amount of from about 5 wt.% to about 50 wt.% by weight of the compositions, in certain preferred aspects in an amount of from about 20 wt.% to about 40 wt.% by weight of the compositions or from about 10 wt.% to about 30 wt.% by weight of the compositions.

[0042] In further embodiments, the (b) composition comprises R-1 16 as the majority component - i.e. R-1 16 is provided in an amount of greater than 50 wt.% based on the total weight of any other (b) component. In further of such embodiments, R-1 16 is the sole component (b) and is provided in an amount between about 20 wt.% to about 50 wt.% by weight of the composition, between about 25 wt.% to about 45 wt.% by weight of the composition, or between about 30 wt.% to about 40 wt.% by weight of the composition based on the total amounts of the compounds in (a) and (b).

[0043] In alternative embodiments, R-23 may be provided as majority component

(i.e. R-23 is provided in an amount of greater than 50 wt.% based on the total weight of the other (b) components). In further of such embodiments, R-23 is the sole component (b) and is provided in an amount between about 5 wt.% to about 50 wt.% by weight of the composition, between about 10 wt.% to about 35 wt.% by weight of the composition, or between about 15 wt.% to about 25 wt.% by weight of the composition based on the total amounts of the compounds in (a) and (b).

[0044] In further embodiments, the (b) composition comprises xenon as the majority component - i.e. xenon is provided in an amount of greater than 50 wt.% based on the total weight of any other (b) component. In further of such embodiments, xenon is the sole component (b) and is provided in an amount between about 10 wt.% to about 90 wt.% by weight of the composition, between about 15 wt.% to about 85 wt.% by weight of the composition, or between about 25 wt.% to about 70 wt.% by weight of the composition based on the total amounts of the compounds in (a) and (b).

[0045] In further embodiments, the (b) composition comprises ethane as the majority component - i.e. ethane is provided in an amount of greater than 50 wt.% based on the total weight of any other (b) component. In further of such embodiments, ethane is the sole component (b) and is provided in an amount between about 10 wt.% to about 90 wt.% by weight of the composition, between about 15 wt.% to about 65 wt.% by weight of the composition, or between about 20 wt.% to about 60 wt.% by weight of the composition based on the total amounts of the compounds in (a) and (b).

[0046] In even further embodiments, the (b) composition comprises VDF as the majority component - i.e. VDF is provided in an amount of greater than 50 wt.% based on the total weight of any other (b) component. In further of such embodiments, VDF is the sole component (b) and is provided in an amount between about 10 wt.% to about 90 wt.% by weight of the composition, between about 15 wt.% to about 65 wt.% by weight of the composition, or between about 20 wt.% to about 60 wt.% by weight of the composition based on the total amounts of the compounds in (a) and (b).

[0047] In alternative, but in certain instances preferred, the compositions of the present invention may comprise, consist essentially of, or consist of: (a) C02 as a first component; (b) a second component selected from the group consisting of R-1 16, R-23, or combinations thereof; and (c) optionally a third component selected from the group consisting of a C1 -C5 substituted or unsubstituted, saturated or unsaturated hydrocarbon (other than those of component (b), a noble gas or combinations thereof.

[0048] With regard to the third component, the hydrocarbon, in certain

embodiments, may include a saturated, unsubstituted, C1 -C5 straight or branched chain alkane. In certain preferred aspects, the hydrocarbon comprises, consists essentially of, or consists of ethane. In alternative (or additional embodiments), the hydrocarbon comprises a C1 -C5 straight or branched chain alkene, which may be optionally substituted with one or more substituent groups, which in certain embodiments includes one or more halogen atoms. Examples of such compounds include, but are not limited to vinylidene fluoride (VDF), ethylene, or propylene. In certain preferred aspects, the hydrocarbon comprises, consists essentially of, or consists of vinylidene fluoride.

[0049] Noble gases may include helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). In certain preferred aspects, the noble gas comprises, consists essentially of, or consists of xenon.

[0050] In certain aspects of the invention, the compositions, particularly the refrigerant compositions, comprise, consists essentially of, or consists of components (a) and (b). In such compositions, C02 may be provided in an amount of from about 10 wt.% to about 90 wt.% by weight of the compositions, in certain preferred aspects in an amount of from about 35 wt.% to about 85 wt.% by weight of the compositions, and in further preferred aspects in an amount of from about 40 wt.% to about 70 wt.% by weight of the compositions.

[0051] The second component, whether R-1 16 individually, R-23 individually, or a combination of both, may be provided in an amount of from about 5 wt.% to about 50 wt.% by weight of the compositions, in certain preferred aspects in an amount of from about 20 wt.% to about 40 wt.% by weight of the compositions or from about 10 wt.% to about 30 wt.% by weight of the compositions, and depending upon the composition of component (b) and (c) (if present). In certain preferred embodiments, the total amount of R-1 16 and R-23 is provided in an amount of from about 5 wt.% to about 50 wt.% by weight of the composition, in an amount of from about 20 wt.% to about 40 wt.% by weight, or from about 10 wt.% to about 30 wt.% by weight of the composition, depending upon the composition of component (b) and (c) (if present).

[0052] In certain embodiments where the composition includes (a) and (b), but not

(c), the (b) composition comprises R-1 16 as the majority component - i.e. R-1 16 is provided in an amount of greater than 50 wt.% based on the total weight of R-1 16 and R-23. In further of such embodiments, R-1 16 is the sole component (b) and is provided in an amount between about 20 wt.% to about 50 wt.% by weight of the composition, between about 25 wt.% to about 45 wt.% by weight of the composition, or between about 30 wt.% to about 40 wt.% by weight of the composition based on the total amounts of the compounds in (a) and (b).

[0053] In certain embodiments where the composition includes (a), (b) and (c), the

(b) component may include R-1 16 as the majority component (i.e. R-1 16 is provided in an amount of greater than 50 wt.% based on the total weight of R-1 16 and R-23).

Alternatively, in such compositions, R-23 may be provided as majority component (i.e. R-23 is provided in an amount of greater than 50 wt.% based on the total weight of R-1 16 and R-23) or R-23 and R-1 16 may be provided in approximately equal amounts. In further of such embodiments, R-1 16 or R-32 is the sole component (b).

[0054] In embodiments of the present invention where the composition includes each of components (a)-(c) and component (b) includes only R-1 16, then R-1 16 may be provided in an amount from about 5 wt.% to about 50 wt.% by weight of the compositions, based on the total amounts of the compounds in (a), (b), and (c). In embodiments of the foregoing, where component (c) comprises ethane, R-1 16 may be provided in an amount from about 5 wt. % to about 30 wt. %, based on the total amounts of the compounds in (a), (b), and (c). In embodiments where component (c) is xenon, R-1 16 may be provided in an amount from about 20 wt. % to about 45 wt. %, based on the total amounts of the compounds in (a), (b), and (c). In embodiments, where component (c) is vinylidene fluoride, R-1 16 may be provided in an amount from about 20 wt. % to about 40 wt. %, based on the total amounts of the compounds in (a), (b), and (c).

[0055] In embodiments, where the composition includes each of components

(a)-(c) and component (b) includes only R-23, then R-23 may be provided in an amount from about 5 wt. % to about 50 wt. % by weight of the compositions, based on the total amounts of the compounds in (a), (b), and (c). In embodiments of the foregoing where component (c) comprises ethane, R-23 may be provided in an amount from about 10 wt. % to about 40 wt. %, based on the total amounts of the compounds in (a), (b), and (c). In embodiments, where component (c) is vinylidene fluoride, R-23 may be provided in an amount from about 5 wt. % to about 25 wt. %, based on the total amounts of the compounds in (a), (b), and (c).

[0056] In embodiments where component (c) is included within the compositions of the present invention, in certain aspects, it may be provided in an amount of from about 5% to about 65% by weight of the compositions, and in certain preferred embodiments from about 5% to about 30% by weight of the compositions, based on the total amounts of the compounds in (a), (b), and (c).

[0057] By way of non-limiting example, in embodiments of the present invention where component (c) includes ethane, such compound may be provided in an amount from about 5 wt.% to about 30 wt.% by weight of the compositions, or in certain embodiments from about 5 wt. % to about 15 wt.%, based on the total amounts of the compounds in (a), (b), and (c). For example, in embodiments where component (b) comprises R-1 16, ethane may be provided in an amount from about 5 wt. % to about 15 wt. %, based on the total amounts of the compounds in (a), (b), and (c). In embodiments where component (b) is R-23, ethane may be provided in an amount from about 5 wt. % to about 30 wt. %, based on the total amounts of the compounds in (a), (b), and (c).

[0058] In embodiments of the present invention where component (c) includes xenon, such compound may be provided in an amount from about 5 wt.% to about 65 wt.% by weight of the compositions, or in certain embodiments from about 5 wt. % to about 15 wt.%, based on the total amounts of the compounds in (a), (b), and (c), particularly, though not exclusively, in embodiments where component (b) comprises R-1 16.

[0059] In embodiments of the present invention where component (c) includes vinylidene fluoride, such compound may be provided in an amount from about 5 wt.% to about 35 wt.% by weight of the compositions, based on the total amounts of the compounds in (a), (b), and (c). For example, in embodiments where component (b) comprises R-1 16, vinylidene fluoride may be provided in an amount from about 10 wt. % to about 30 wt. %, based on the total amounts of the compounds in (a), (b), and (c). In embodiments where component (b) is R-23, vinylidene fluoride may be provided in an amount from about 5 wt. % to about 25 wt. %, based on the total amounts of the compounds in (a), (b), and (c).

[0060] As mentioned above, applicants have found that the compositions of the present invention are capable of achieving a difficult combination of properties, including particularly low GWP. By way of non-limiting example, the following Table A illustrates the substantial GWP superiority of certain compositions of the present invention, which are described in parenthesis in terms of weight fraction of each component, in comparison to the GWP of R-508B, which has a GWP of about 13,000. TABLE A

[0061] The compositions of the present invention may include other components for the purpose of enhancing or providing certain functionality to the composition, or in some cases to reduce the cost of the composition. For example, refrigerant compositions according to the present invention, especially those used in vapor compression systems, include a lubricant, generally in amounts of from about 30 to about 50 percent by weight of the composition, and in some case potentially in amount greater than about 50 percent and other cases in amounts as low as about 5 percent.

[0062] Commonly used refrigeration lubricants such as Polyol Esters (POEs) and Poly Alkylene Glycols (PAGs), PAG oils, 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. Commercially available mineral oils include Witco LP 250 (registered trademark) from Witco, Zerol 300 (registered trademark) from Shrieve Chemical, Sunisco 3GS from Witco, and Calumet R015 from Calumet. Commercially available alkyl benzene lubricants include Zerol 150 (registered trademark). Commercially available esters include neopentyl glycol dipelargonate, which is available as Emery 2917 (registered trademark) and Hatcol 2370 (registered trademark). Other useful esters include phosphate esters, dibasic acid esters, and fluoroesters. Preferred lubricants include polyalkylene glycols and esters. Of course, different mixtures of different types of lubricants may be used.

HEAT TRANSFER METHODS AND SYSTEMS

[0063] The present methods, systems and compositions are thus adaptable for use in connection with a wide variety of heat transfer systems in general and refrigeration systems in particular, such as air-conditioning, refrigeration, heat-pump systems, food freeze drying, cold storage of good in transit and the like. In certain preferred

embodiments, the compositions of the present invention are used in refrigeration systems originally designed for use with an HFC refrigerant, such as, for example, R-508B. The preferred compositions of the present invention tend to exhibit many of the desirable characteristics of R-508B but have a GWP that is substantially lower than that of R-508B while at the same time having a capacity that is substantially similar to or substantially matches, and preferably is as high as or higher than R-508B. In particular, applicants have recognized that certain preferred embodiments of the present compositions tend to exhibit relatively low global warming potentials ("GWPs"), preferably less than about 10,000, and more preferably not greater than about 7,500, and even more preferably not greater than about 5,000.

[0064] In certain other preferred embodiments, the present compositions are used in refrigeration systems originally designed for use with R-508B. Preferred refrigeration compositions of the present invention may be used in refrigeration systems containing a lubricant used conventionally with R-508B, such as polyolester oils, and the like, or may be used with other lubricants traditionally used with HFC refrigerants. As used herein the term "refrigeration system" refers generally to any system or apparatus, or any part or portion of such a system or apparatus, which employs a refrigerant to provide cooling. Such refrigeration systems include, for example, air conditioners, electric refrigerators, chillers, warehousing of cold storage goods, and the like.

[0065] As mentioned above, the present invention achieves exceptional advantage in connection with systems known as low or ultra low temperature refrigeration systems. That is, compositions of the present invention provide surprising and unexpected advantages in connection with systems that utilize one or more compressors and a condenser temperature of from about -40°C to about -20°C. In preferred embodiments of such systems, the systems have an evaporator temperature of from about -90°C to about -70°C, with an evaporator temperature preferably of about -80°C. Moreover, in preferred embodiments of such systems, the systems have a degree of superheat at evaporator outlet of from about 5°C to about 30°C, with a degree of superheat at evaporator outlet preferably of from about 8°C to about 12°C.

EXAMPLES

[0066] The following examples are provided for the purpose of illustrating the present invention but without limiting the scope thereof.

Example 1 - Flammability Studies

[0067] Critical Flammable Ratio for compositions of C02A DF and R-1 16/VDF were measured according to ASTM E681 standard under a temperature of 60 °C. The results showed that the critical flammability ratio/CFR for R1 16/VDF is 81/19 % by weight and for C02/VDF is 76/24 % by weight.

Example 2 - C02 Freezing Studies

[0068] Figure 1 shows that a 50/50 blend of C0₂A DF solidifies at -75 °C. With higher amount of VDF, CO₂ freezing temperature can be further reduced. More specifically, C02 was transferred into a high pressure sample cylinder by freezing the cylinder with liquid nitrogen. Then, VDF was transferred into the same sample cylinder while keep freezing. The cylinder was warmed up to room temperature to thaw the mixture of C02 and VDF. The mixture was then transferred into a glass tube while it is being cooled by liquid nitrogen. A thermocouple is placed into the tube to measure temperature. The glass tube was then lifted out of the liquid nitrogen to let the solid mixture thaw. It was then placed back into the liquid nitrogen to cool until it frozen. During the cooling process, the temperature of the mixture was recorded by a computer. The melting point can be read when solid starts to appear.

Example 3 - Performance Studies

[0069] The coefficient of performance (COP) is a universally accepted measure of refrigerant performance, especially useful in representing the relative thermodynamic efficiency of a refrigerant in a specific heating or cooling cycle involving evaporation or condensation of the refrigerant. In refrigeration engineering, this term expresses the ratio of useful refrigeration to the energy applied by the compressor in compressing the vapor. The capacity of a refrigerant represents the amount of cooling or heating it provides and provides some measure of the capability of a compressor to pump quantities of heat for a given volumetric flow rate of refrigerant. In other words, given a specific compressor, a refrigerant with a higher capacity will deliver more cooling or heating power. One means for estimating COP of a refrigerant at specific operating conditions is from the thermodynamic properties of the refrigerant using standard refrigeration cycle analysis techniques (see for example, R.C. Downing, FLUOROCARBON REFRIGERANTS HANDBOOK, Chapter 3, Prentice-Hall, 1988).

[0070] Below, an example ultralow temperature refrigeration system is provided having the condenser temperature is set to -30°C. The degree of sub-cooling at the expansion device inlet is set to ~2°C to ~ 10°C. The evaporating temperature is set to -80°C. The degree of superheat at evaporator outlet is set to ~5°C. The degree of superheat in the suction line is set to ~10°C to ~ 30°C, and the compressor efficiency is set to 60%. The pressure drop and heat transfer in the connecting lines (suction and liquid lines) are considered negligible, and heat leakage through the compressor shell is ignored. Several operating parameters are determined for the compositions identified below in Table 1 in accordance with the present invention, and these operating parameters are reported in Table 2 below, based upon R-508B having a COP value of 1.00, a capacity value of 1.00 and a discharge temperature of 33.1 °C.

[0071] In certain preferred embodiments the replacement should not require substantial redesign of the system and no major item of equipment needs to be replaced in order to accommodate the refrigerant of the present invention. For that purpose the replacement preferably fulfills one or more of, and preferably all, of the following requirements:

• High-Side Pressure that is within about 1 15%, and even more preferably within about 1 10% of the high side pressure of the same system using R-508B. This parameter can be important in such embodiments because it can enhance the ability to use existing pressure components in such systems.

• Efficiency (COP) that is similar to R-508B (±5%) without incurring in excess

capacity as noted above.

• The blend is a 2L class refrigerant with a BV less than 10 cm/s

• The GWP is lower than 10,000, preferably less than 7,500, and even less than 5,000 for some of the proposed blends.

• The blend is nonflammable by ASHRAE 34.

• Discharge Temperature is not higher than 110 °C.

Table 1 shows the thermodynamic cycle performance of 14 blends comparing with R-508B in accordance with the parameters above. All the blends has a GWP of <5000, which is >60% reduced than R508B. All the blends have similar cooling efficiency but higher volumetric capacity.

Table 1 : Thermodynamic cycle performance of potential blends No. Components Composition GWP Flamm- C02 Other ability freeze concern concern concern

@ -80°C

B1 C02/R1 16 60/40 4880 Abs. No ^; Yes

B2 C02/R23 80/20 2960 Abs. No ^; Yes

B3 C02/Xenon 40/60 0 Abs. No : Yes T dis

B4 C02/ethane 69/31 0 Yes Yes

B G02/VDF Ω/ Ω n Υρς Vpc

B6 C02/R1 16/Ethane 65/25/10 3050 might Yes

B7 C02/R1 16/Ethane 80/10/10 1220 might Yes

B8 C02/R23/Ethane 61/30/9 4992 might Yes

B9 C02/Xenon/R1 16 50/10/40 4880 Abs. No : Yes

B10 C02/Xenon/R1 16 40/30/30 3660 Abs. No : Yes

B1 1 C02/Xenon/R1 16 15/60/25 3050 Abs. No No Cost

B12 C02/VDF/R23 70/20/10 1480 might Yes

B13 C02/VDF/R23 70/10/20 2960 No Yes

B14 C02/VDF/R1 16 50/20/30 3660 No Yes

Table 2: Feasibility analysis of blends

Claims

CLAIMS What is Claimed is:

1. A heat transfer composition, comprising:

(a) C02;

(b) at least one of R-1 16 and R-23;

(c) optionally, at least one C1 -C5 substituted or unsubstituted, saturated or unsaturated hydrocarbon different than R-116 and than R-23; and

(d) optionally a noble gas.

2. The heat transfer composition of claim 1 , wherein said component (c) is present and is selected from the group consisting of ethane, vinylidene fluoride, and combinations thereof.

3. The heat transfer composition of claim 1 , wherein said component (d)

comprises xenon.

4. The heat transfer composition of claim 1 , wherein said C02 is present in the composition in an amount from about 10 wt. % to about 90 wt. %, based on the total weight of components (a)-(d).

5. The heat transfer composition of claim 1 , wherein said component (b) is present in the composition in an amount from about 5 wt. % to about 50 wt. %, based on the total weight of components (a)-(d).

6. The heat transfer composition of claim 1 , wherein said component (b) comprises R-23 present in the composition in an amount from about 10 wt. % to about 30 wt. %, based on the total weight of components (a)-(d).

7. The heat transfer composition of claim 1 , wherein the total amount of said component (c) and (d) in the composition is from about 5 wt. % to about 35 wt. %, based on the total weight of components (a)-(d).

8. The heat transfer composition of claim 1 , wherein said component (c) is present in the composition in an amount from about 5 wt. % to about 30 wt. %, based on the total weight of components (a)-(d).

9. The heat transfer composition of claim 1 , wherein said component (b) consists essentially of R-1 16 and said component (c) comprises ethane, wherein the composition comprises from about 55 wt.% to about 90 wt.% of CO2, from about 5 wt. % to about 30 wt. % of R-1 16; and from about 5 wt. % to about 15 wt. % of ethane.

10. The heat transfer composition of claim 1 , wherein said component (b) consists essentially of R-1 16 and said component (d) comprises Xenon, wherein CO2 is provided in an amount from about 10 wt.% to about 75 wt.%; R-1 16 is present in an amount from about 20 wt. % to about 45 wt. %; and Xenon is present in an amount from about 5 wt. % to about 65 wt. %.

1 1. The heat transfer composition of claim 1 , wherein said component (b) consists essentially of R-1 16 and said component (c) comprises vinylidene fluoride, wherein said CO2 is present in an amount from about 30 wt.% to about 70 wt.%; R-1 16 is present in an amount from about 20 wt. % to about 40 wt. %; and vinylidene fluoride is present in an amount from about 10 wt. % to about 30 wt. %.

12. The heat transfer composition of claim 1 , wherein said component (b) consists essentially of R-23 and said component (c) comprises ethane, wherein CO2 is present in an amount from about 30 wt.% to about 75 wt.%; R-23 is present in an amount from about 10 wt. % to about 40 wt. %; and ethane is present in an amount from about 5 wt. % to about 30 wt. %.

13. The heat transfer composition of claim 1 , wherein said component (b) consists essentially of R-23 and said component (c) comprises vinylidene fluoride, wherein CO2 is present in an amount from about 50 wt.% to about 90 wt.%; R-23 is provided in an amount from about 5 wt. % to about 25 wt. %; and vinylidene fluoride is present in an amount from about 5 wt. % to about 25 wt. %.

14. The heat transfer composition of claim 1 , wherein said component (d) consists essentially of xenon, which is present in an amount from about 10 wt.% to about 90 wt.%, based on the total weight of components (a)-(d).

15. The heat transfer composition of claim 1 , wherein said component (d) consists essentially of xenon, which is present in an amount from about 25 wt.% to about 70 wt.%, based on the total weight of components (a)-(d).

16. The heat transfer composition of claim 1 , wherein said component (c) consists essentially of ethane, which is present in an amount from about 10 wt.% to about 90 wt.%, based on the total weight of components (a)-(d).

17. The heat transfer composition of claim 1 , wherein said component (c) consists essentially of ethane, which is present in an amount from about 20 wt.% to about 60 wt.%, based on the total weight of components (a)-(d).

18. The heat transfer composition of claim 1 , wherein said component (c) consists essentially of vinylidene fluoride, which is present in an amount from about 10 wt.% to about 90 wt.%, based on the total weight of components (a)-(d).

19. The heat transfer composition of claim 1 , wherein said component (c) consists essentially of vinylidene fluoride, which is present in an amount from about 20 wt.% to about 60 wt.%, based on the total weight of components (a)-(d).