CASCADE REFRIGERATION SYSTEM WITH FLUOROOLEFIN REFRIGERANT
The present invention relates to a cascade refrigeration system which circulates a refrigerant comprising a fluoroolefin therethrough. The cascade refrigeration system includes a low temperature refrigeration loop and a medium temperature refrigeration loop. The fluoroolefin circulates through either loop, or both. In a particular embodiment, the fluoroolefin circulates through the medium temperature loop. In a particular embodiment, where the cascade refrigeration system includes a first and a second cascade heat exchanger, and a secondary heat transfer loop which extends between the first and second cascade heat exchangers, either the first and/or second refrigerant may be, but need not necessarily be, a fluoroolefin.
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1. Field of the Disclosure
The present disclosure relates to a cascade refrigeration system which circulates a refrigerant comprising a fluoroolefin therethrough. In particular, such a cascade system includes a medium temperature loop and a low temperature loop, and a fluoroolefin refrigerant may be used in either loop, or both.
2. Description of Related Art
Cascade refrigeration systems are known in the art, see for example, ICR07-B2-358, “CO2-DX Systems for Medium-and Low-Temperature Refrigeration in Supermarket Applications”, T. Sienel, O. Finckh, International Congress of Refrigeration, 2007, Beijing. Such a system typically uses a refrigerant such as 1,1,1,2-tetrafluoroethane (R134a) or blends thereof with HFC-125 and HFC-143a (i.e., R404A) in the medium temperature loop and carbon dioxide (CO2) in the low temperature loop to provide cooling to display cases, for instance, in supermarkets.
The refrigeration industry has been working for the past few decades to find replacement refrigerants for the ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) being phased out as a result of the Montreal Protocol. The solution for most refrigerant producers has been the commercialization of hydrofluorocarbon (HFC) refrigerants. The new HFC refrigerants, HFC-134a being the most widely used at this time, have zero ozone depletion potential and thus are not affected by the current regulatory phase out as a result of the Montreal Protocol.
Further environmental regulations may ultimately cause global phase out of certain HFC refrigerants. Currently, the automobile industry is facing regulations relating to global warming potential for refrigerants used in mobile air-conditioning. Therefore, there is a great current need to identify new refrigerants with reduced global warming potential for the mobile air-conditioning market. Should the regulations be more broadly applied in the future, for instance for stationary air conditioning and refrigeration systems, an even greater need will be felt for refrigerants that can be used in all areas of the refrigeration and air-conditioning industry.
Currently proposed replacement refrigerants for HFC-134a include HFC-152a, pure hydrocarbons such as butane or propane, or “natural” refrigerants such as CO2. Many of these suggested replacements are toxic, flammable, and/or have low energy efficiency. New replacements are also being proposed for HCFC-22, R404A, R407C and R410A, among others. As these replacements are found, new uses of such alternative refrigerants are being sought in order to take advantage of their low or zero ozone depletion potential and lower global warming potential.
SUMMARY OF THE INVENTIONThe object of the present disclosure is to provide cascade refrigeration systems which use refrigerant compositions which have unique characteristics to meet the demands of low or zero ozone depletion potential and lower global warming potential as compared to current refrigerants.
In addition to lower global warming potential advantages, the cascade refrigeration systems of the present invention may have higher energy efficiency and capacity than currently used cascade refrigeration systems.
Therefore, in accordance with the present invention there is provided a cascade refrigeration system having at least two refrigeration loops, each circulating a refrigerant therethrough, comprising:
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- (a) a first expansion device for reducing the pressure and temperature of a first refrigerant liquid;
- (b) an evaporator having an inlet and an outlet, wherein the first refrigerant liquid from the first expansion device enters the evaporator through the evaporator inlet and is evaporated in the evaporator to form a first refrigerant vapor, thereby producing cooling, and circulates to the outlet;
- (c) a first compressor having an inlet and an outlet, wherein the first refrigerant vapor from the evaporator circulates to the inlet of the first compressor and is compressed, thereby increasing the pressure and the temperature of the first refrigerant vapor, and the compressed first refrigerant vapor circulates to the outlet of the first compressor;
- (d) a cascade heat exchanger system having:
- (i) a first inlet and a first outlet, wherein the first refrigerant vapor circulates from the first inlet to the first outlet and is condensed in the heat exchanger system to form a first refrigerant liquid, thereby rejecting heat, and
- (ii) a second inlet and a second outlet, wherein a second refrigerant liquid circulates from the second inlet to the second outlet and absorbs the heat rejected by the first refrigerant and forms a second refrigerant vapor;
- (e) a second compressor having an inlet and an outlet, wherein the second refrigerant vapor from the cascade heat exchanger system is drawn into the compressor and is compressed, thereby increasing the pressure and temperature of the second refrigerant vapor;
- (f) a condenser having an inlet and an outlet for circulating the second refrigerant vapor therethrough and for condensing the second refrigerant vapor from the compressor to form a second refrigerant liquid, wherein the second refrigerant liquid exits the condenser through the condenser outlet; and
- (g) a second expansion device which reduces the pressure and temperature of the second refrigerant liquid exiting the condenser and entering the second inlet of the cascade heat exchanger system.
Either the first refrigerant or the second refrigerant, or both, may comprise a fluoroolefin.
In a particular embodiment, the cascade heat exchanger system may include a first and a second cascade heat exchanger, and a secondary heat transfer loop which extends between the first and the second cascade heat exchanger. In this embodiment, the second refrigerant liquid indirectly absorbs the heat rejected by the first refrigerant vapor through a heat transfer fluid which circulates between the first cascade heat exchanger and the second cascade heat exchanger through the secondary heat transfer loop. The first cascade heat exchanger has a first inlet and a first outlet, and a second inlet and a second outlet, wherein the first refrigerant vapor circulates from the first inlet to the first outlet and rejects heat and is condensed, and a secondary heat transfer fluid circulates from the second inlet to the second outlet and absorbs the heat rejected from the first refrigerant vapor and circulates to the second cascade heat exchanger. The second cascade heat exchanger has a first inlet and a first outlet, and a second inlet and a second outlet, wherein the heat transfer fluid circulates from the second outlet of the first cascade heat exchanger to the first inlet of the second cascade heat exchanger and to the first outlet of the second cascade heat exchanger and rejects the heat absorbed from the first refrigerant. The second refrigerant liquid circulates from the second inlet to the second outlet of the second cascade heat exchanger and absorbs the heat rejected by the heat transfer fluid and forms a second refrigerant vapor. In this embodiment, either the first and/or second refrigerant may be, but need not necessarily be, a fluoroolefin.
Further in accordance with the present invention, there is provided a method of exchanging heat between at least two refrigeration loops, comprising:
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- (a) absorbing heat from a body to be cooled in a first refrigeration loop and rejecting this heat to a second refrigeration loop; and
- (b) absorbing the heat from the first refrigeration loop in the second refrigeration loop and rejecting this heat to ambient, wherein the refrigerant in at least one of the refrigeration loops comprises a fluoroolefin.
The present invention may be better understood with reference to the following Figures, wherein:
Before addressing details of embodiments described below, some terms are defined or clarified.
Refrigeration capacity (also referred to as cooling capacity) is a term to define the change in enthalpy of a refrigerant in an evaporator per unit mass of refrigerant circulated, or the heat removed by the refrigerant in the evaporator per unit volume of refrigerant vapor exiting the evaporator (volumetric capacity). The refrigeration capacity is a measure of the ability of a refrigerant or heat transfer composition to produce cooling. Therefore, the higher the capacity, the greater the cooling that is produced for a given refrigerant circulation rate. Cooling rate refers to the heat removed by the refrigerant in the evaporator per unit time.
Coefficient of performance (COP) is the amount of heat removed from a body to be cooled divided by the required energy input to operate the cycle over a given time interval. The higher the COP, the higher is the energy efficiency. COP is directly related to the energy efficiency ratio (EER) that is the efficiency rating for refrigeration or air conditioning equipment at a specific set of internal and external temperatures.
Global warming potential (GWP) is an index for estimating relative global warming contribution due to atmospheric emission of a kilogram of a particular greenhouse gas compared to emission of a kilogram of carbon dioxide. GWP can be calculated for different time horizons showing the effect of atmospheric lifetime for a given gas. The GWP for the 100 year time horizon is commonly the value referenced. For mixtures, a mass-fraction weighted average can be calculated based on the individual GWPs for each component.
Ozone depletion potential (ODP) is a number that refers to the amount of stratospheric ozone depletion caused by a substance. The ODP is the ratio of the impact on stratospheric ozone of a chemical compared to the impact of a similar mass of CFC-11 (fluorotrichloromethane). Thus, the ODP of CFC-11 is defined to be 1.0. Other CFCs and HCFCs have ODPs that range from 0.01 to 1.0. HFCs have zero ODP because they do not contain chlorine.
As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).
The transitional phrase “consisting of” excludes any element, step, or ingredient not specified. If in the claim such would close the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase “consists of” appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.
The transitional phrase “consisting essentially of” is used to define a composition, method or apparatus that includes materials, steps, features, components, or elements, in addition to those literally disclosed provided that these additional included materials, steps, features, components, or elements do materially affect the basic and novel characteristic(s) of the claimed invention. The term ‘consisting essentially of’ occupies a middle ground between “comprising” and ‘consisting of’.
Where applicants have defined an invention or a portion thereof with an open-ended term such as “comprising,” it should be readily understood that (unless otherwise stated) the description should be interpreted to also describe such an invention using the terms “consisting essentially of” or “consisting of.”
Also, use of “a” or “an” are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the disclosed compositions, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety, unless a particular passage is cited. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
In accordance with the present invention, there is provided a cascade refrigeration system having at least two refrigeration loops for circulating a refrigerant through each loop. Such a cascade system is shown generally at 10 in
As shown in
The cascade refrigeration system of the present invention also includes an evaporator 18 as shown in
The cascade refrigeration system of the present invention also includes a first compressor 20. The first compressor has an inlet 20a and an outlet 20b. The first refrigerant vapor from the evaporator circulates to the inlet of the first compressor and is compressed, thereby increasing the pressure and the temperature of the first refrigerant vapor. The compressed first refrigerant vapor then circulates to the outlet of the first compressor.
The cascade refrigeration system of the present invention also includes a cascade heat exchanger system 22. The heat exchanger has a first inlet 22a and a first outlet 22b. The first refrigerant vapor from the first compressor enters the first inlet of the heat exchanger and is condensed in the heat exchanger to form a first refrigerant liquid, thereby rejecting heat. The first refrigerant liquid then circulates to the first outlet of the heat exchanger. The heat exchanger also includes a second inlet 22c and a second outlet 22d. A second refrigerant liquid circulates from the second inlet to the second outlet of the heat exchanger and is evaporated to form a second refrigerant vapor, thereby absorbing the heat rejected by the first refrigerant (as it is condensed). This heat is rejected to ambient. The second refrigerant vapor then circulates to the second outlet of the heat exchanger. Thus, in the embodiment of
The cascade refrigeration system of the present invention also includes a second compressor 24 as shown in
The cascade refrigeration system of the present invention also includes a condenser 26 having an inlet 26a and an outlet 26b. The second refrigerant from the second compressor circulates from the inlet and is condensed in the condenser to form a second refrigerant liquid. The second refrigerant liquid exits the condenser through the outlet.
The cascade refrigeration system of the present invention also includes a second expansion device 28 having an inlet 28a and an outlet 28b. The second refrigerant liquid passes through the second expansion device, which reduces the pressure and temperature of the second refrigerant liquid exiting the condenser. This liquid may be partially vaporized during this expansion. The reduced pressure and temperature second refrigerant liquid circulates to the second inlet of the cascade heat exchanger system from the expansion device.
It should be noted that various modifications to the embodiment as shown in
In accordance with the present invention, either the first refrigerant or the second refrigerant in the cascade system of the embodiment of
Such fluoroolefins may be selected from the group consisting of:
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- (i) fluoroolefins of the formula E- or Z—R1CH═CHR2, wherein R1 and R2 are, independently, C1 to C6 perfluoroalkyl groups;
- (ii) cyclic fluoroolefins of the formula cyclo-[CX═CY(CZW)n—], wherein X, Y, Z, and W, independently, are H or F, and n is an integer from 2 to 5; and
- (iii) fluoroolefins selected from the group consisting of: tetrafluoroethylene (CF2═CF2); hexafluoropropene (CF3CF═CF2);1,2,3,3,3-pentafluoro-1-propene (CHF═CFCF3), 1,1,3,3,3-pentafluoro-1-propene (CF2═CHCF3), 1,1,2,3,3-pentafluoro-1-propene (CF2═CFCHF2), 1,2,3,3-tetrafluoro-1-propene (CHF═CFCHF2), 2,3,3,3-tetrafluoro-1-propene (CH2═CFCF3), 1,3,3,3-tetrafluoro-1-propene (CHF═CHCF3), 1,1,2,3-tetrafluoro-1-propene (CF2═CFCH2F), 1,1,3,3-tetrafluoro-1-propene (CF2═CHCHF2), 1,2,3,3-tetrafluoro-1-propene (CHF═CFCHF2), 3,3,3-trifluoro-1-propene (CH2═CHCF3), 2,3,3-trifluoro-1-propene (CHF2CF═CH2); 1,1,2-trifluoro-1-propene (CH3CF═CF2); 1,2,3-trifluoro-1-propene (CH2FCF═CF2); 1,1,3-trifluoro-1-propene (CH2FCH═CF2); 1,3,3-trifluoro-1-propene (CHF2CH═CHF); 1,1,1,2,3,4,4,4-octafluoro-2-butene (CF3CF═CFCF3); 1,1,2,3,3,4,4,4-octafluoro-1-butene (CF3CF2CF═CF2); 1,1,1,2,4,4,4-heptafluoro-2-butene (CF3CF═CHCF3); 1,2,3,3,4,4,4-heptafluoro-1-butene (CHF═CFCF2CF3); 1,1,1,2,3,4,4-heptafluoro-2-butene (CHF2CF═CFCF3); 1,3,3,3-tetrafluoro-2-(trifluoromethyl)-1-propene ((CF3)2C═CHF); 1,1,3,3,4,4,4-heptafluoro-1-butene (CF2═CHCF2CF3); 1,1,2,3,4,4,4-heptafluoro-1-butene (CF2═CFCHFCF3); 1,1,2,3,3,4,4-heptafluoro-1-butene (CF2═CFCF2CHF2); 2,3,3,4,4,4-hexafluoro-1-butene (CF3CF2CF═CH2); 1,3,3,4,4,4-hexafluoro-1-butene (CHF═CHCF2CF3); 1,2,3,4,4,4-hexafluoro-1-butene (CHF═CFCHFCF3); 1,2,3,3,4,4-hexafluoro-1-butene (CHF═CFCF2CHF2); 1,1,2,3,4,4-hexafluoro-2-butene (CHF2CF═CFCHF2); 1,1,1,2,3,4-hexafluoro-2-butene (CH2FCF═CFCF3); 1,1,1,2,4,4-hexafluoro-2-butene (CHF2CH═CFCF3); 1,1,1,3,4,4-hexafluoro-2-butene (CF3CH═CFCHF2); 1,1,2,3,3,4-hexafluoro-1-butene (CF2═CFCF2CH2F); 1,1,2,3,4,4-hexafluoro-1-butene (CF2═CFCHFCHF2); 3,3,3-trifluoro-2-(trifluoromethyl)-1-propene (CH2═C(CF3)2); 1,1,1,2,4-pentafluoro-2-butene (CH2FCH═CFCF3); 1,1,1,3,4-pentafluoro-2-butene (CF3CH═CFCH2F); 3,3,4,4,4-pentafluoro-1-butene (CF3CF2CH═CH2); 1,1,1,4,4-pentafluoro-2-butene (CHF2CH═CHCF3); 1,1,1,2,3-pentafluoro-2-butene (CH3CF═CFCF3); 2,3,3,4,4-pentafluoro-1-butene (CH2═CFCF2CHF2); 1,1,2,4,4-pentafluoro-2-butene (CHF2CF═CHCHF2); 1,1,2,3,3-pentafluoro-1-butene (CH3CF2CF═CF2); 1,1,2,3,4-pentafluoro-2-butene (CH2FCF═CFCHF2); 1,1,3,3,3-pentafluoro-2-methyl-1-propene (CF2═C(CF3)(CH3)); 2-(difluoromethyl)-3,3,3-trifluoro-1-propene (CH2═C(CHF2)(CF3)); 2,3,4,4,4-pentafluoro-1-butene (CH2═CFCHFCF3); 1,2,4,4,4-pentafluoro-1-butene (CHF═CFCH2CF3); 1,3,4,4,4-pentafluoro-1-butene (CHF═CHCHFCF3); 1,3,3,4,4-pentafluoro-1-butene (CHF═CHCF2CHF2); 1,2,3,4,4-pentafluoro-1-butene (CHF═CFCHFCHF2); 3,3,4,4-tetrafluoro-1-butene (CH2═CHCF2CHF2); 1,1-difluoro-2-(difluoromethyl)-1-propene (CF2═C(CHF2)(CH3)); 1,3,3,3-tetrafluoro-2-methyl-1-propene (CHF═C(CF3)(CH3)); 3,3-difluoro-2-(difluoromethyl)-1-propene (CH2═C(CHF2)2); 1,1,1,2-tetrafluoro-2-butene (CF3CF═CHCH3); 1,1,1,3-tetrafluoro-2-butene (CH3CF═CHCF3); 1,1,1,2,3,4,4,5,5,5-decafluoro-2-pentene (CF3CF═CFCF2CF3); 1,1,2,3,3,4,4,5,5,5-decafluoro-1-pentene (CF2═CFCF2CF2CF3); 1,1,1,4,4,4-hexafluoro-2-(trifluoromethyl)-2-butene ((CF3)2C═CHCF3); 1,1,1,2,4,4,5,5,5-nonafluoro-2-pentene (CF3CF═CHCF2CF3); 1,1,1,3,4,4,5,5,5-nonafluoro-2-pentene (CF3CH═CFCF2CF3); 1,2,3,3,4,4,5,5,5-nonafluoro-1-pentene (CHF═CFCF2CF2CF3); 1,1,3,3,4,4,5,5,5-nonafluoro-1-pentene (CF2═CHCF2CF2CF3); 1,1,2,3,3,4,4,5,5-nonafluoro-1-pentene (CF2═CFCF2CF2CHF2); 1,1,2,3,4,4,5,5,5-nonafluoro-2-pentene (CHF2CF═CFCF2CF3); 1,1,1,2,3,4,4,5,5-nonafluoro-2-pentene (CF3CF═CFCF2CHF2); 1,1,1,2,3,4,5,5,5-nonafluoro-2-pentene (CF3CF═CFCHFCF3); 1,2,3,4,4,4-hexafluoro-3-(trifluoromethyl)-1-butene (CHF═CFCF(CF3)2); 1,1,2,4,4,4-hexafluoro-3-(trifluoromethyl)-1-butene (CF2═CFCH(CF3)2); 1,1,1,4,4,4-hexafluoro-2-(trifluoromethyl)-2-butene (CF3CH═C(CF3)2); 1,1,3,4,4,4-hexafluoro-3-(trifluoromethyl)-1-butene (CF2═CHCF(CF3)2); 2,3,3,4,4,5,5,5-octafluoro-1-pentene (CH2═CFCF2CF2CF3); 1,2,3,3,4,4,5,5-octafluoro-1-pentene (CHF═CFCF2CF2CHF2); 3,3,4,4,4-pentafluoro-2-(trifluoromethyl)-1-butene (CH2═C(CF3)CF2CF3); 1,1,4,4,4-pentafluoro-3-(trifluoromethyl)-1-butene (CF2═CHCH(CF3)2); 1,3,4,4,4-pentafluoro-3-(trifluoromethyl)-1-butene (CHF═CHCF(CF3)2); 1,1,4,4,4-pentafluoro-2-(trifluoromethyl)-1-butene (CF2═C(CF3)CH2CF3); 3,4,4,4-tetrafluoro-3-(trifluoromethyl)-1-butene ((CF3)2CFCH═CH2); 3,3,4,4,5,5,5-heptafluoro-1-pentene (CF3CF2CF2CH═CH2); 2,3,3,4,4,5,5-heptafluoro-1-pentene (CH2═CFCF2CF2CHF2); 1,1,3,3,5,5,5-heptafluoro-1-butene (CF2═CHCF2CH2CF3); 1,1,1,2,4,4,4-heptafluoro-3-methyl-2-butene (CF3CF═C(CF3)(CH3)); 2,4,4,4-tetrafluoro-3-(trifluoromethyl)-1-butene (CH2═CFCH(CF3)2); 1,4,4,4-tetrafluoro-3-(trifluoromethyl)-1-butene (CHF═CHCH(CF3)2); 1,1,1,4-tetrafluoro-2-(trifluoromethyl)-2-butene (CH2FCH═C(CF3)2); 1,1,1,3-tetrafluoro-2-(trifluoromethyl)-2-butene (CH3CF═C(CF3)2); 1,1,1-trifluoro-2-(trifluoromethyl)-2-butene ((CF3)2C═CHCH3); 3,4,4,5,5,5-hexafluoro-2-pentene (CF3CF2CF═CHCH3); 1,1,1,4,4,4-hexafluoro-2-methyl-2-butene (CF3C(CH3)═CHCF3); 3,3,4,5,5,5-hexafluoro-1-pentene (CH2═CHCF2CHFCF3); 4,4,4-trifluoro-2-(trifluoromethyl)-1-butene (CH2═C(CF3)CH2CF3); 1,1,2,3,3,4,4,5,5,6,6,6-dodecafluoro-1-hexene (CF3(CF2)3CF═CF2); 1,1,1,2,2,3,4,5,5,6,6,6-dodecafluoro-3-hexene (CF3CF2CF═CFCF2CF3); 1,1,1,4,4,4-hexafluoro-2,3-bis(trifluoromethyl)-2-butene ((CF3)2C═C(CF3)2); 1,1,1,2,3,4,5,5,5-nonafluoro-4-(trifluoromethyl)-2-pentene ((CF3)2CFCF═CFCF3); 1,1,1,4,4,5,5,5-octafluoro-2-(trifluoromethyl)-2-pentene ((CF3)2C═CHC2F5); 1,1,1,3,4,5,5,5-octafluoro-4-(trifluoromethyl)-2-pentene ((CF3)2CFCF═CHCF3); 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene (CF3CF2CF2CF2CH═CH2); 4,4,4-trifluoro-3,3-bis(trifluoromethyl)-1-butene (CH2═CHC(CF3)3); 1,1,1,4,4,4-hexafluoro-3-methyl-2-(trifluoromethyl)-2-butene ((CF3)2C═C(CH3)(CF3)); 2,3,3,5,5,5-hexafluoro-4-(trifluoromethyl)-1-pentene (CH2═CFCF2CH(CF3)2); 1,1,1,2,4,4,5,5,5-nonafluoro-3-methyl-2-pentene (CF3CF═C(CH3)CF2CF3); 1,1,1,5,5,5-hexafluoro-4-(trifluoromethyl)-2-pentene (CF3CH═CHCH(CF3)2); 3,4,4,5,5,6,6,6-octafluoro-2-hexene (CF3CF2CF2CF═CHCH3); 3,3,4,4,5,5,6,6-octafluoro1-hexene (CH2═CHCF2CF2CF2CHF2); 1,1,1,4,4-pentafluoro-2-(trifluoromethyl)-2-pentene ((CF3)2C═CHCF2CH3); 4,4,5,5,5-pentafluoro-2-(trifluoromethyl)-1-pentene (CH2═C(CF3)CH2C2F5); 3,3,4,4,5,5,5-heptafluoro-2-methyl-1-pentene (CF3CF2CF2C(CH3)═CH2); 4,4,5,5,6,6,6-heptafluoro-2-hexene (CF3CF2CF2CH═CHCH3); 4,4,5,5,6,6,6-heptafluoro-1-hexene (CH2═CHCH2CF2C2F5); 1,1,1,2,2,3,4-heptafluoro-3-hexene (CF3CF2CF═CFC2H5); 4,5,5,5-tetrafluoro-4-(trifluoromethyl)-1-pentene (CH2═CHCH2CF(CF3)2); 1,1,1,2,5,5,5-heptafluoro-4-methyl-2-pentene (CF3CF═CHCH(CF3)(CH3)); 1,1,1,3-tetrafluoro-2-(trifluoromethyl)-2-pentene ((CF3)2C═CFC2H5); 1,1,1,2,3,4,4,5,5,6,6,7,7,7-tetradecafluoro-2-heptene (CF3CF═CFCF2CF2C2F5); 1,1,1,2,2,3,4,5,5,6,6,7,7,7-tetradecafluoro-3-heptene (CF3CF2CF═CFCF2C2F5); 1,1,1,3,4,4,5,5,6,6,7,7,7-tridecafluoro-2-heptene (CF3CH═CFCF2CF2C2F5); 1,1,1,2,4,4,5,5,6,6,7,7,7-tridecafluoro-2-heptene (CF3CF═CHCF2CF2C2F5); 1,1,1,2,2,4,5,5,6,6,7,7,7-tridecafluoro-3-heptene (CF3CF2CH═CFCF2C2F5); and 1,1,1,2,2,3,5,5,6,6,7,7,7-tridecafluoro-3-heptene (CF3CF2CF═CHCF2C2F5).
In some embodiments, fluoroolefins are compounds, which comprise carbon atoms, fluorine atoms and optionally hydrogen or chlorine atoms. In one embodiment, the fluoroolefins used in the compositions of the present invention comprise compounds with 2 to 12 carbon atoms. In another embodiment the fluoroolefins comprise compounds with 3 to 10 carbon atoms, and in yet another embodiment the fluoroolefins comprise compounds with 3 to 7 carbon atoms. Representative fluoroolefins include but are not limited to all compounds as listed in Table 1, Table 2, and Table 3.
In one embodiment of the present invention the first refrigerant is selected from fluoroolefins having the formula E- or Z—R1CH═CHR2 (Formula (i)), wherein R1 and R2 are, independently, C1 to C6 perfluoroalkyl groups. Examples of R1 and R2 groups include, but are not limited to, CF3, C2F5, CF2CF2CF3, CF(CF3)2, CF2CF2CF2CF3, CF(CF3)CF2CF3, CF2CF(CF3)2, C(CF3)3, CF2CF2CF2CF2CF3, CF2CF2CF(CF3)2, C(CF3)2C2F5, CF2CF2CF2CF2CF2CF3, CF(CF3)CF2CF2C2F5, and C(CF3)2CF2C2F5. In one embodiment the fluoroolefins of Formula (i) have at least 4 carbon atoms in the molecule. In another embodiment, the first refrigerant is selected from fluoroolefins of Formula (i) having at least 5 carbon atoms in the molecule. In yet another embodiment, the first refrigerant is selected from fluoroolefins of Formula (i) having at least 6 carbon atoms in the molecule. Exemplary, non-limiting Formula (i) compounds are presented in Table 1.
Compounds of Formula (i) may be prepared by contacting a perfluoroalkyl iodide of the formula R1I with a perfluoroalkyltrihydroolefin of the formula R2CH═CH2 to form a trihydroiodoperfluoroalkane of the formula R1CH2CHIR2. This trihydroiodoperfluoroalkane can then be dehydroiodinated to form R1CH═CHR2. Alternatively, the olefin R1CH═CHR2 may be prepared by dehydroiodination of a trihydroiodoperfluoroalkane of the formula R1CHICH2R2 formed in turn by reacting a perfluoroalkyl iodide of the formula R2I with a perfluoroalkyltrihydroolefin of the formula R1CH═CH2.
The contacting of a perfluoroalkyl iodide with a perfluoroalkyltrihydroolefin may take place in batch mode by combining the reactants in a suitable reaction vessel capable of operating under the autogenous pressure of the reactants and products at reaction temperature. Suitable reaction vessels include fabricated from stainless steels, in particular of the austenitic type, and the well-known high nickel alloys such as Monel® nickel-copper alloys, Hastelloy® nickel based alloys and Inconel® nickel-chromium alloys.
Alternatively, the reaction may be conducted in semi-batch mode in which the perfluoroalkyltrihydroolefin reactant is added to the perfluoroalkyl iodide reactant by means of a suitable addition apparatus such as a pump at the reaction temperature.
The ratio of perfluoroalkyl iodide to perfluoroalkyltrihydroolefin should be between about 1:1 to about 4:1, preferably from about 1.5:1 to 2.5:1. Ratios less than 1.5:1 tend to result in large amounts of the 2:1 adduct as reported by Jeanneaux, et. al. in Journal of Fluorine Chemistry, Vol. 4, pages 261-270 (1974).
Preferred temperatures for contacting of said perfluoroalkyl iodide with said perfluoroalkyltrihydroolefin are preferably within the range of about 150° C. to 300° C., preferably from about 170° C. to about 250° C., and most preferably from about 180° C. to about 230° C.
Suitable contact times for the reaction of the perfluoroalkyl iodide with the perfluoroalkyltrihydroolefin are from about 0.5 hour to 18 hours, preferably from about 4 to about 12 hours.
The trihydroiodoperfluoroalkane prepared by reaction of the perfluoroalkyl iodide with the perfluoroalkyltrihydroolefin may be used directly in the dehydroiodination step or may preferably be recovered and purified by distillation prior to the dehydroiodination step.
The dehydroiodination step is carried out by contacting the trihydroiodoperfluoroalkane with a basic substance. Suitable basic substances include alkali metal hydroxides (e.g., sodium hydroxide or potassium hydroxide), alkali metal oxide (for example, sodium oxide), alkaline earth metal hydroxides (e.g., calcium hydroxide), alkaline earth metal oxides (e.g., calcium oxide), alkali metal alkoxides (e.g., sodium methoxide or sodium ethoxide), aqueous ammonia, sodium amide, or mixtures of basic substances such as soda lime. Preferred basic substances are sodium hydroxide and potassium hydroxide.
Said contacting of the trihydroiodoperfluoroalkane with a basic substance may take place in the liquid phase preferably in the presence of a solvent capable of dissolving at least a portion of both reactants. Solvents suitable for the dehydroiodination step include one or more polar organic solvents such as alcohols (e.g., methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tertiary butanol), nitriles (e.g., acetonitrile, propionitrile, butyronitrile, benzonitrile, or adiponitrile), dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, or sulfolane. The choice of solvent may depend on the boiling point product and the ease of separation of traces of the solvent from the product during purification. Typically, ethanol or isopropanol are good solvents for the reaction.
Typically, the dehydroiodination reaction may be carried out by addition of one of the reactants (either the basic substance or the trihydroiodoperfluoroalkane) to the other reactant in a suitable reaction vessel. Said reaction may be fabricated from glass, ceramic, or metal and is preferably agitated with an impeller or stirring mechanism.
Temperatures suitable for the dehydroiodination reaction are from about 10° C. to about 100° C., preferably from about 20° C. to about 70° C. The dehydroiodination reaction may be carried out at ambient pressure or at reduced or elevated pressure. Of note are dehydroiodination reactions in which the compound of Formula (i) is distilled out of the reaction vessel as it is formed.
Alternatively, the dehydroiodination reaction may be conducted by contacting an aqueous solution of said basic substance with a solution of the trihydroiodoperfluoroalkane in one or more organic solvents of lower polarity such as an alkane (e.g., hexane, heptane, or octane), aromatic hydrocarbon (e.g., toluene), halogenated hydrocarbon (e.g., methylene chloride, chloroform, carbon tetrachloride, or perchloroethylene), or ether (e.g., diethyl ether, methyl tert-butyl ether, tetrahydrofuran, 2-methyl tetrahydrofuran, dioxane, dimethoxyethane, diglyme, or tetraglyme) in the presence of a phase transfer catalyst. Suitable phase transfer catalysts include quaternary ammonium halides (e.g., tetrabutylammonium bromide, tetrabutylammonium hydrosulfate, triethylbenzylammonium chloride, dodecyltrimethylammonium chloride, and tricaprylylmethylammonium chloride), quaternary phosphonium halides (e.g., triphenylmethylphosphonium bromide and tetraphenylphosphonium chloride), or cyclic polyether compounds known in the art as crown ethers (e.g., 18-crown-6 and 15-crown-5).
Alternatively, the dehydroiodination reaction may be conducted in the absence of solvent by adding the trihydroiodoperfluoroalkane to a solid or liquid basic substance.
Suitable reaction times for the dehydroiodination reactions are from about 15 minutes to about six hours or more depending on the solubility of the reactants. Typically the dehydroiodination reaction is rapid and requires about 30 minutes to about three hours for completion. The compound of Formula (i) may be recovered from the dehydroiodination reaction mixture by phase separation after addition of water, by distillation, or by a combination thereof.
In another embodiment of the present invention, the first refrigerant is selected from fluoroolefins comprising cyclic fluoroolefins (cyclo-[CX═CY(CZW)n—] (Formula (ii)), wherein X, Y, Z, and W are independently selected from H and F, and n is an integer from 2 to 5). In one embodiment the fluoroolefins of Formula (ii), have at least about 3 carbon atoms in the molecule. In another embodiment, the fluoroolefins of Formula (ii) have at least about 4 carbon atoms in the molecule. In another embodiment, the fluoroolefins of Formula (ii) have at least about 5 carbon atoms in the molecule. In yet another embodiment, the fluoroolefins of Formula (ii) have at least about 6 carbon atoms in the molecule. Representative cyclic fluoroolefins of Formula (ii) are listed in Table 2.
The first refrigerant of the present invention may comprise a single compound of Formula (i) or Formula (ii), for example, one of the compounds in Table 1 or Table 2, or may comprise a combination of compounds of Formula (i) or Formula (ii).
In another embodiment, the first refrigerant is selected from fluoroolefins comprising those compounds listed in Table 3.
The compounds listed in Table 2 and Table 3 are available commercially or may be prepared by processes known in the art or as described herein.
1,1,1,4,4-pentafluoro-2-butene may be prepared from 1,1,1,2,4,4-hexafluorobutane (CHF2CH2CHFCF3) by dehydrofluorination over solid KOH in the vapor phase at room temperature. The synthesis of 1,1,1,2,4,4-hexafluorobutane is described in U.S. Pat. No. 6,066,768. 1,1,1,4,4,4-hexafluoro-2-butene may be prepared from 1,1,1,4,4,4-hexafluoro-2-iodobutane (CF3CHICH2CF3) by reaction with KOH using a phase transfer catalyst at about 60° C. The synthesis of 1,1,1,4,4,4-hexafluoro-2-iodobutane may be carried out by reaction of perfluoromethyl iodide (CF3I) and 3,3,3-trifluoropropene (CF3CH═CH2) at about 200° C. under autogenous pressure for about 8 hours.
3,4,4,5,5,5-hexafluoro-2-pentene may be prepared by dehydrofluorination of 1,1,1,2,2,3,3-heptafluoropentane (CF3CF2CF2CH2CH3) using solid KOH or over a carbon catalyst at 200-300° C. 1,1,1,2,2,3,3-heptafluoropentane may be prepared by hydrogenation of 3,3,4,4,5,5,5-heptafluoro-1-pentene (CF3CF2CF2CH═CH2).
1,1,1,2,3,4-hexafluoro-2-butene may be prepared by dehydrofluorination of 1,1,1,2,3,3,4-heptafluorobutane (CH2FCF2CHFCF3) using solid KOH.
1,1,1,2,4,4-hexafluoro-2-butene may be prepared by dehydrofluorination of 1,1,1,2,2,4,4-heptafluorobutane (CHF2CH2CF2CF3) using solid KOH.
1,1,1,3,4,4-hexafluoro2-butene may be prepared by dehydrofluorination of 1,1,1,3,3,4,4-heptafluorobutane (CF3CH2CF2CHF2) using solid KOH. 1,1,1,2,4-pentafluoro-2-butene may be prepared by dehydrofluorination of 1,1,1,2,2,3-hexafluorobutane (CH2FCH2CF2CF3) using solid KOH.
1,1,1,3,4-pentafluoro-2-butene may be prepared by dehydrofluorination of 1,1,1,3,3,4-hexafluorobutane (CF3CH2CF2CH2F) using solid KOH.
1,1,1,3-tetrafluoro-2-butene may be prepared by reacting 1,1,1,3,3-pentafluorobutane (CF3CH2CF2CH3) with aqueous KOH at 120° C.
1,1,1,4,4,5,5,5-octafluoro-2-pentene may be prepared from (CF3CHICH2CF2CF3) by reaction with KOH using a phase transfer catalyst at about 60° C. The synthesis of 4-iodo-1,1,1,2,2,5,5,5-octafluoropentane may be carried out by reaction of perfluoroethyliodide (CF3CF2I) and 3,3,3-trifluoropropene at about 200° C. under autogenous pressure for about 8 hours.
1,1,1,2,2,5,5,6,6,6-decafluoro-3-hexene may be prepared from 1,1,1,2,2,5,5,6,6,6-decafluoro-3-iodohexane (CF3CF2CHICH2CF2CF3) by reaction with KOH using a phase transfer catalyst at about 60° C. The synthesis of 1,1,1,2,2,5,5,6,6,6-decafluoro-3-iodohexane may be carried out by reaction of perfluoroethyliodide (CF3CF2I) and 3,3,4,4,4-pentafluoro-1-butene (CF3CF2CH═CH2) at about 200° C. under autogenous pressure for about 8 hours.
1,1,1,4,5,5,5-heptafluoro-4-(trifluoromethyl)-2-pentene may be prepared by the dehydrofluorination of 1,1,1,2,5,5,5-heptafluoro-4-iodo-2-(trifluoromethyl)-pentane (CF3CHICH2CF(CF3)2) with KOH in isopropanol. CF3CHICH2CF(CF3)2 is made from reaction of (CF3)2CFI with CF3CH═CH2 at high temperature, such as about 200° C.
1,1,1,4,4,5,5,6,6,6-decafluoro-2-hexene may be prepared by the reaction of 1,1,1,4,4,4-hexafluoro-2-butene (CF3CH═CHCF3) with tetrafluoroethylene (CF2═CF2) and antimony pentafluoride (SbF5).
2,3,3,4,4-pentafluoro-1-butene may be prepared by dehydrofluorination of 1,1,2,2,3,3-hexafluorobutane over fluorided alumina at elevated temperature.
2,3,3,4,4,5,5,5-ocatafluoro-1-pentene may be prepared by dehydrofluorination of 2,2,3,3,4,4,5,5,5-nonafluoropentane over solid KOH.
1,2,3,3,4,4,5,5-octafluoro-1-pentene may be prepared by dehydrofluorination of 2,2,3,3,4,4,5,5,5-nonafluoropentane over fluorided alumina at elevated temperature.
Many of the compounds of Formula 1, Formula 2, Table 1, Table 2 and Table 3 exist as different configurational isomers or stereoisomers. When the specific isomer is not designated, the present invention is intended to include all single configurational isomers, single stereoisomers, or any combination thereof. For instance, F11E is meant to represent the E-isomer, Z-isomer, or any combination or mixture of both isomers in any ratio. As another example, HFO-1225ye is meant to represent the E-isomer, Z-isomer, or any combination or mixture of both isomers in any ratio.
Additionally, the first refrigerant may be any of the single fluoroolefins of Formula (i), Formula (ii), Table 1, Table 2 and Table 3, or may be any combination of the different fluoroolefins from Formula (i), Formula (ii), Table 1, Table 2 and Table 3.
In some embodiments, the first refrigerant may be any combination of a single fluoroolefin or multiple fluoroolefins selected from Formula (i), Formula (ii), Table 1, Table 2 and Table 3 with at least one additional refrigerant selected from hydrofluorocarbons, fluoroethers, hydrocarbons, CF3I, ammonia (NH3), carbon dioxide (CO2), nitrous oxide (N2O), and mixtures thereof, meaning mixtures of any of the foregoing compounds.
In some embodiments, the first refrigerant may contain hydrofluorocarbons comprising at least one saturated compound containing carbon, hydrogen, and fluorine. Of particular utility are hydrofluorocarbons having 1-7 carbon atoms and having a normal boiling point of from about −90° C. to about 80° C. Hydrofluorocarbons are commercial products available from a number of sources or may be prepared by methods known in the art. Representative hydrofluorocarbon compounds include but are not limited to fluoromethane (CH3F, HFC-41), difluoromethane (CH2F2, HFC-32), trifluoromethane (CHF3, HFC-23), pentafluoroethane (CF3CHF2, HFC-125), 1,1,2,2-tetrafluoroethane (CHF2CHF2, HFC-134), 1,1,1,2-tetrafluoroethane (CF3CH2F, HFC-134a), 1,1,1-trifluoroethane (CF3CH3, HFC-143a), 1,1-difluoroethane (CHF2CH3, HFC-152a), fluoroethane (CH3CH2F, HFC-161), 1,1,1,2,2,3,3-heptafluoropropane (CF3CF2CHF2, HFC-227ca), 1,1,1,2,3,3,3-heptafluoropropane (CF3CHFCF3, HFC-227ea), 1,1,2,2,3,3,-hexafluoropropane (CHF2CF2CH F2, HFC-236ca), 1,1,1,2,2,3-hexafluoropropane (CF3CF3CH2F, HFC-236cb), 1,1,1,2,3,3-hexafluoropropane (CF3CHFCHF2, HFC-236ea), 1,1,1,3,3,3-hexafluoropropane (CF3CH2CF3, HFC-236fa), 1,1,2,2,3-pentafluoropropane (CHF2CF2CH2F, HFC-245ca), 1,1,1,2,2-pentafluoropropane (CF3CF2CH3, HFC-245cb), 1,1,2,3,3-pentafluoropropane (CHF2CHFCHF2, HFC-245ea), 1,1,1,2,3-pentafluoropropane (CF3CHFCH2F, HFC-245eb), 1,1,1,3,3-pentafluoropropane (CF3CH2CHF2, HFC-245fa), 1,2,2,3-tetrafluoropropane (CH2FCF2CH2F, HFC-254ca), 1,1,2,2-tetrafluoropropane (CHF2CF2CH3, HFC-254cb), 1,1,2,3-tetrafluoropropane (CHF2CHFCH2F, HFC-254ea), 1,1,1,2-tetrafluoropropane (CF3CHFCH3, HFC-254eb), 1,1,3,3-tetrafluoropropane (CHF2CH2CHF2, HFC-254fa), 1,1,1,3-tetrafluoropropane (CF3CH2CH2F, HFC-254fb), 1,1,1-trifluoropropane (CF3CH2CH3, HFC-263fb), 2,2-difluoropropane (CH3CF2CH3, HFC-272ca), 1,2-difluoropropane (CH2FCHFCH3, HFC-272ea), 1,3-difluoropropane (CH2FCH2CH2F, HFC-272fa), 1,1-difluoropropane (CHF2CH2CH3, HFC-272fb), 2-fluoropropane (CH3CHFCH3, HFC-281ea), 1-fluoropropane (CH2FCH2CH3, HFC-281fa), 1,1,2,2,3,3,4,4-octafluorobutane (CHF2CF2CF2CHF2, HFC-338pcc), 1,1,1,2,2,4,4,4-octafluorobutane (CF3CH2CF2CF3, HFC-338mf), 1,1,1,3,3-pentafluorobutane (CF3CH2CHF2, HFC-365mfc), 1,1,1,2,3,4,4,5,5,5-decafluoropentane (CF3CHFCHFCF2CF3, HFC-43-10mee), and 1,1,1,2,2,3,4,5,5,6,6,7,7,7-tetradecafluoroheptane (CF3CF2CHFCHFCF2CF2CF3, HFC-63-14mee).
In some embodiments, the first refrigerant may further comprise fluoroethers. Fluoroethers comprise at least one compound having carbon, fluorine, oxygen and optionally hydrogen, chlorine, bromine or iodine. Fluoroethers are commercially available or may be produced by methods known in the art. Representative fluoroethers include but are not limited to nonafluoromethoxybutane (C4F9OCH3, any or all possible isomers or mixtures thereof); nonafluoroethoxybutane (C4F9OC2H5, any or all possible isomers or mixtures thereof); 2-difluoromethoxy-1,1,1,2-tetrafluoroethane (HFOC-236eaβγ, or CHF2OCHFCF3); 1,1-difluoro-2-methoxyethane (HFOC-272fbEβγ,CH3OCH2CHF2); 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane (HFOC-347mmzEβγ, or CH2FOCH(CF3)2); 1,1,1,3,3,3-hexafluoro-2-methoxypropane (HFOC-356mmzEβγ, or CH3OCH(CH3)2); 1,1,1,2,2-pentafluoro-3-methoxypropane (HFOC-365mcEγδ, or CF3CF2CH2OCH3); 2-ethoxy-1,1,1,2,3,3,3-heptafluoropropane (HFOC-467mmyEβγ, or CH3CH2OCF(CF3)2; and mixtures thereof.
In some embodiments, the first refrigerant may further comprise at least one hydrocarbon. Hydrocarbons are compounds having only carbon and hydrogen. Of particular utility are compounds having 3-7 carbon atoms. Hydrocarbons are commercially available through numerous chemical suppliers. Representative hydrocarbons include but are not-limited to propane, n-butane, isobutane, cyclobutane, n-pentane, 2-methylbutane, 2,2-dimethylpropane, cyclopentane, n-hexane, 2-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, 3-methylpentane, cyclohexane, n-heptane, cycloheptane, and mixtures thereof. In some embodiments, the disclosed compositions may comprise hydrocarbons containing heteroatoms, such as dimethylether (DME, CH3OCH3). DME is commercially available.
In some embodiments, the first refrigerant may further comprise carbon dioxide (CO2), which is commercially available from various sources or may be prepared by methods known in the art.
In some embodiments, the first refrigerant may further comprise ammonia (NH3), which is commercially available from various sources or may be prepared by methods known in the art.
In some embodiments, the first refrigerant may further comprise iodotrifluoromethane (CF3I), which is commercially available from various sources or may be prepared by methods known in the art.
In particular embodiments, the first and the second refrigerants may be as shown in the Table 4 below.
In certain embodiments, the second refrigerant may consist essentially of HFO-1234yf. In other embodiments, the second refrigerant may comprise HFO-1234yf and R134a. In yet other embodiments, the second refrigerant may comprise HFO-1234yf and R32, or it may comprise trans HFO-1234ze and HFC-32, or trans HFO-1234ze and HFC-134a or trans HFO-1234ze and HFC-125.
In the embodiment where the second refrigerant consists essentially of HFO-1234yf, the first refrigerant may comprise carbon dioxide (CO2) or nitrous oxide (N2O). Alternatively, in the embodiment where the second refrigerant consists essentially of HFO-1234yf, the first refrigerant may comprise HFO-1234yf and HFC-32. In another embodiment, where the second refrigerant consists essentially of HFO-1234yf, the first refrigerant may comprise trans HFO-1234ze and HFC-32.
In the embodiment where the second refrigerant comprises HFO-1234yf and HFC-134a, or when the second refrigerant comprises HFO-1234yf and HFC-32, the first refrigerant may comprise either carbon dioxide or nitrous oxide. Alternatively, in the embodiment where the second refrigerant comprises HFO-1234yf and HFC-134a, or HFO-1234yf and HFC-32, the first refrigerant may comprise HFO-1234yf and HFC-32. In another embodiment, where the second refrigerant comprises HFO-1234yf and HFC-134a, or HFO-1234yf and HFC-32, the first refrigerant may comprise trans HFO-1234ze and HFC-32.
In the particular embodiment where the second refrigerant comprises HFO-1234yf and R134a, and the first refrigerant comprises HFO-1234yf and HFC-32, the second refrigerant may comprise 1-99% HFO-1234yf and 99-1% HFC-134a. In one embodiment, the second refrigerant comprises 1-53.1% HFO-1234yf and 46.9-99% HFC-134a. In particular, the second refrigerant comprises 53% HFO-1234yf and 47% HFC-134a. In one embodiment, the second refrigerant comprises 1-59% HFO-1234yf and 41-99% HFC-134a. In this embodiment, the second refrigerant is non-flammable at 100° C. or 60° C. This composition is non-flammable and has maximum capacity in the range of 40-59% 1234yf and 41-60% 134a. In particular, the second refrigerant may comprise 53% HFO-1234yf and 47% HFC-134a.
In the particular embodiment where the second refrigerant comprises HFO-1234yf and HFC-32, the ranges for these components may be 1-99% HFO-1234yf and 99-1% HFC-32. In a particular embodiment, the second refrigerant may comprise 20-99% HFO-1234yf and 80-99% HFC-32. More particularly, the second refrigerant may comprise 50-99% HFO-1234yf and 50-99% HFC-32, and even more particularly, the second refrigerant may comprise 63% HFO-1234yf and 37% HFC-32. In this embodiment, the second refrigerant may be used as a replacement for R404A. In another embodiment, the second refrigerant may comprise 27.5% HFO-1234yf and 72.5% HFC-32. In this embodiment, the second refrigerant may be used as a replacement for R410A. In any of the embodiments of the foregoing embodiments where the second refrigerant comprises a particular range of HFO-1234yf and HFC-32, the first refrigerant may comprise either CO2 or N2O, a blend of HFO-1234yf/HFC-32, or a blend of trans HFO-1234ze/HFC-32.
In the embodiment where the second refrigerant comprises trans HFO-1234ze and HFC-32, the first refrigerant may comprise either carbon dioxide or nitrous oxide. Alternatively, in the embodiment where the second refrigerant comprises trans-HFO-1234ze and HFC-32, the first refrigerant may comprise HFO-1234yf and HFC-32. In another embodiment, where the second refrigerant comprises trans-HFO-1234ze and HFC-32, the first refrigerant may comprise trans HFO-1234ze and HFC-32.
In the particular embodiment where the second refrigerant comprises trans HFO-1234ze and HFC-32, the second refrigerant comprises 1-99% HFO-1234ze and 99-1% HFC-32. The 1234ze may be either trans-1234ze or cis-1234ze. In any of the embodiments of the foregoing embodiments where the second refrigerant comprises a particular range of trans HFO-1234ze and HFC-32, the first refrigerant may comprise the first refrigerant may comprise either CO2 or N2O, a blend of HFO-1234yf/HFC-32, or a blend of trans HFO-1234ze/HFC-32.
In the embodiment where the second refrigerant comprises trans HFO-1234ze and HFC-134a, the first refrigerant may comprise either CO2 or N2O. Alternatively, in the embodiment where the second refrigerant comprises trans-HFO-1234ze and HFC-134a, the first refrigerant may comprise HFO-1234yf and HFC-32. In another embodiment, where the second refrigerant comprises trans-HFO-1234ze and HFC-134a, the first refrigerant may comprise trans HFO-1234ze and HFC-32.
In the embodiment where the second refrigerant comprises trans HFO-1234ze and HFC-125, the first refrigerant may comprise either carbon dioxide or nitrous oxide. Alternatively, in the embodiment where the second refrigerant comprises trans-HFO-1234ze and HFC-125, the first refrigerant may comprise HFC-32 and HFO-1234yf. In another embodiment, where the second refrigerant comprises trans-HFO-1234ze and HFC-125, the first refrigerant may comprise trans HFO-1234ze and HFC-32.
Various configurations of cascade systems also come within the scope of the present invention. For instance, reference is made to
The cascade refrigeration system of
Referring specifically to
A portion of the reduced pressure and temperature second refrigerant liquid which exits condenser 26′ enters the cascade heat exchanger 22′ at inlet 22c′. In cascade heat exchanger 22′, as in the first embodiment of
Another embodiment of the cascade refrigeration system of the present invention is shown in
The embodiment of
Referring to
A further embodiment of the cascade refrigeration system of the present invention is shown in
In the embodiment of
It should be noted that it is within the scope of the present invention that the embodiment of
In the system of the embodiment of
Further in accordance with the present invention, there is provided a method of exchanging heat between at least two refrigeration loops, comprising: (a) absorbing heat from a body to be cooled in a first refrigeration loop and rejecting this heat to a second refrigeration loop; and (b) absorbing the heat from the first refrigeration loop in the second refrigeration loop and rejecting this heat to ambient. The refrigerant in either loop, i.e., the loop in which heat is absorbed or the loop in which heat is rejected, or both, may comprise a fluoroolefin. The heat from the first refrigeration loop may be absorbed directly in the second refrigeration loop, such as in the embodiments of
Table 5 shows the performance of some exemplary compositions as compared to HFC-134a. In Table 5, Evap Pres is evaporator pressure, Cond Pres is condenser pressure, Comp Disch T is compressor discharge temperature, COP is coefficient of performance (analogous to energy efficiency), CAP is capacity, Avg. Temp. glide is the average of the temperature glide in the evaporator and condenser, and GWP is global warming potential. The data are based on the following conditions.
Note that the evaporator superheat enthalpy is not included in cooling capacity and energy efficiency determinations.
The data in Table 5 indicate that the 1234yf/134a compositions are a close match to 134a, in terms of COP, capacity, pressures and temperatures in the system, with lower GWP values. In addition, all the compositions have low temperature glide and a specific composition could be selected based on regulatory requirements for GWP, which have not at this time been determined. The composition containing 53 wt % HFO-1234yf and 47 wt % HFC-134a has the particular benefit of providing a low GWP and a peak in the cooling capacity. This is shown graphically in
Flammable compositions may be identified by testing under ASTM (American Society of Testing and Materials) E681-2004, with an electronic ignition source. Such tests of flammability were conducted on compositions containing HFO-1234yf and HFC-134a at 101 kPa (14.7 psia), 50 percent relative humidity, and about 23° C. (room temperature), 60° C. and 100° C. at various concentrations in air in order to determine if flammable and if so, to find the lower flammability limit (LFL) and the upper flammability limit (UFL). The results are given in Table 6.
At room temperature conditions (about 23° C.), compositions with 66.25 weight percent or less HFO-1234yf in HFC-134a would be considered non-flammable. At 60° C., compositions with 60.00 weight percent or less HFO-1234yf in HFC-134a would be considered non-flammable. At 100° C., compositions containing 53.10 weight percent or less HFO-1234yf in HFC-134a would be considered non-flammable.
Example 3 Cooling Performance for Low Temperature Circuit of a Cascade SystemTable 7 shows the performance of certain compositions as compared to CO2, R404A (ASHRAE designation for a mixture containing HFC-125, HFC-134a, and HFC-143a), R410A (ASHRAE designation for a mixture containing HFC-32 and HFC-125) and HFC-32. In Table 7, Evap Pres is evaporator pressure, Cond Pres is condenser pressure, Comp Disch T is compressor discharge temperature, COP is coefficient of performance (analogous to energy efficiency), CAP is capacity, Avg. Temp. glide is the average of the temperature glide in the evaporator and condenser, and GWP is global warming potential. The data are based on the following conditions.
Note that the evaporator superheat enthalpy is not included in cooling capacity and energy efficiency determinations.
The composition containing 63 wt % HFO-1234yf and 37 wt % HFC-32 actually shows improved COP and capacity relative to R404A and also has significantly lower GWP. The composition containing 27.5 wt % HFO-1234yf and 72.5 wt % HFC-32 matches the COP and capacity of R410A, has very low temperature glide indicating azeotrope-like behavior and also has significantly lower GWP.
Note that all compositions comprising mixtures of HFO-1234yf and HFC-32 have improved COP (energy efficiency) as compared to CO2.
Example 4 Total Equivalent Warming ImpactThe total equivalent warming impact (TEWI) is determined for systems as disclosed herein in comparison to conventional uncoupled supermarket refrigeration systems as well as conventional cascade systems. The TEWI takes into consideration the effects of the energy efficiency of the system, the contribution due to the energy source used to provide the electrical power to the equipment, and the amount of refrigerant charged to the system as well as the rate of leakage to quantify a more complete environmental impact of use of different refrigerants.
This Example uses a conventional European direct expansion (DX) supermarket refrigeration system, traditionally using R404A in both medium temperature (MT) and low temperature (LT) refrigeration systems, as the base case for comparison. Certain assumptions were made based on a typical European supermarket system are shown in Table 8. Additionally, the expected equipment life was assumed to be 15 years and the CO2 emitted from electricity generation was estimated to be 0.616 kg CO2/kw-hr.
Table 9 provides the conditions for which the system performance (COP, or coefficient of performance, a measure of energy efficiency) was estimated. In Table 9, temp is temperature, evap is evaporator, cond is condenser, and comp is compressor.
Table 10 lists several different embodiments of the present invention as compared to conventional uncoupled and cascade systems for which the determinations of TEWI are made, as well as the estimated COP values as calculated based on the conditions listed above in Table 9.
The TEWI value includes an indirect contribution, which incorporates energy source and usage, and a direct contribution due to the emissions of refrigerant with a given GWP from a system. Table 11 lists the indirect and direct contributions and the TEWI value calculated for the different systems described above, in terms of equivalent CO2 emissions over equipment life (in million kg) in order from greatest to least environmental impact.
The results in Table 11 demonstrate that the use of HFO-based refrigerants (e.g. in the medium temperature loop of cascade refrigeration systems 3 and 4) can lead to lower TEWI values than those for uncoupled or cascade refrigeration systems using refrigerants known to the prior art.
Claims
1. A cascade refrigeration system having at least two refrigeration loops, each circulating a refrigerant therethrough, comprising:
- (a) a first expansion device for reducing the pressure and temperature of a first refrigerant liquid;
- (b) an evaporator having an inlet and an outlet, wherein the first refrigerant liquid from the first expansion device enters the evaporator through the evaporator inlet and is evaporated in the evaporator to form a first refrigerant vapor, thereby producing cooling, and circulates to the outlet;
- (c) a first compressor having an inlet and an outlet, wherein the first refrigerant vapor from the evaporator circulates to the inlet of the first compressor and is compressed, thereby increasing the pressure and the temperature of the first refrigerant vapor, and the compressed first refrigerant vapor circulates to the outlet of the first compressor;
- (d) a cascade heat exchanger system having: (i) a first inlet and a first outlet, wherein the first refrigerant vapor circulates from the first inlet to the first outlet and is condensed in the heat exchanger system to form a first refrigerant liquid, thereby rejecting heat, and (ii) a second inlet and a second outlet, wherein a second refrigerant liquid circulates from the second inlet to the second outlet and absorbs the heat rejected by the first refrigerant and forms a second refrigerant vapor;
- (e) a second compressor having an inlet and an outlet, wherein the second refrigerant vapor from the cascade heat exchanger system is drawn into the compressor and is compressed, thereby increasing the pressure and temperature of the second refrigerant vapor;
- (f) a condenser having an inlet and an outlet for circulating the second refrigerant vapor therethrough and for condensing the second refrigerant vapor from the compressor to form a second refrigerant liquid, wherein the second refrigerant liquid exits the condenser through the outlet; and
- (g) a second expansion device for reducing the pressure and temperature of the second refrigerant liquid exiting the condenser and entering the second inlet of the cascade heat exchanger system; wherein at least one of the first and the second refrigerant comprises a fluoroolefin.
2. The system of claim 1, wherein the second refrigerant comprises a fluorolefin selected from the group consisting of HFO-1234yf, trans-1234ze and E-1234ze.
3. The system of claim 1, wherein the second refrigerant consists essentially of HFO-1234yf.
4. The system of claim 2, wherein the second refrigerant also comprises R134a.
5. The system of claim 2, wherein the second refrigerant also comprises HFC-32.
6. The system of claim 3, wherein the first refrigerant comprises a composition selected from the group consisting of carbon dioxide and nitrous oxide.
7. The system of claim 3, wherein the first refrigerant comprises HFO-1234yf and HFC-32.
8. The system of claim 4, wherein the first refrigerant comprises a composition selected from the group consisting of carbon dioxide and nitrous oxide.
9. The system of claim 4, wherein the first refrigerant comprises HFO-1234yf and HFC-32.
10. The system of claim 5, wherein the second refrigerant comprises HFO-1234yf.
11. The system of claim 5, wherein the second refrigerant comprises trans-1234ze.
12. The system of claim 5 wherein the first refrigerant comprises carbon dioxide or nitrous oxide.
13. The system of claim 5, wherein the first refrigerant comprises HFO-1234yf and HFC-32.
14. A cascade refrigeration system having at least two refrigeration loops, each circulating a refrigerant therethrough, comprising: a first refrigeration loop, including:
- (a) a first expansion device for reducing the pressure and temperature of a first refrigerant liquid;
- (b) an evaporator having an inlet and an outlet, wherein the first refrigerant liquid from the first expansion device enters the evaporator through the evaporator inlet and is evaporated in the evaporator to form a first refrigerant vapor, thereby producing cooling, and circulates to the outlet;
- (c) a first compressor having an inlet and an outlet, wherein the first refrigerant vapor from the evaporator circulates to the inlet of the first compressor and is compressed, thereby increasing the pressure and the temperature of the first refrigerant vapor, and the compressed first refrigerant vapor circulates to the outlet of the first compressor;
- (d) a cascade heat exchanger system comprising: (i) a first cascade heat exchanger having: (A) a first inlet and a first outlet, wherein the first refrigerant vapor from the evaporator circulates from the first inlet to the first outlet and is condensed in the first heat exchanger to form a first refrigerant liquid, thereby rejecting heat, and (B) a second inlet and a second outlet, wherein a heat transfer fluid circulates from the second inlet to the second outlet, wherein the heat rejected by the first refrigerant vapor as it is condensed is absorbed by the heat transfer fluid, (ii) a second cascade heat exchanger having: (A) a first inlet and a first outlet, wherein the heat transfer fluid from the first cascade heat exchanger circulates from the first inlet to the first outlet and rejects the heat absorbed in the first cascade heat exchanger, and (B) a second inlet and a second outlet, wherein a second refrigerant liquid circulates from the second inlet to the second outlet and absorbs the heat rejected by the heat transfer fluid and forms a second refrigerant vapor;
- (e) a second compressor having an inlet and an outlet, wherein the second refrigerant vapor from the second cascade heat exchanger is drawn into the compressor and is compressed, thereby increasing the pressure and temperature of the second refrigerant vapor;
- (f) a condenser having an inlet and an outlet for circulating the second refrigerant vapor therethrough and for condensing the second refrigerant vapor from the compressor to form a second refrigerant liquid, wherein the second refrigerant liquid exits the condenser through the outlet; and
- (g) a second expansion device for reducing the pressure and temperature of the second refrigerant liquid exiting the condenser and entering the second inlet of the second cascade heat exchanger.
15. A method of exchanging heat between at least two refrigeration loops, comprising:
- (a) absorbing heat from a body to be cooled in a first refrigeration loop and rejecting this heat to a second refrigeration loop; and
- (b) absorbing the heat from the first refrigeration loop in the second refrigeration loop and rejecting this heat to ambient, wherein the refrigerant in at least one of the refrigeration loops comprises a fluoroolefin.
Type: Application
Filed: Nov 3, 2010
Publication Date: Aug 30, 2012
Applicant: E.I. DU PONT DE NEMOURS AND COMPANY (Wilmington, DE)
Inventors: Barbara Haviland Minor (Elkton, MD), Konstantinos Kontomaris (Wilmington, DE), Thomas J. Leck (Hockessin, DE)
Application Number: 13/505,538
International Classification: F25B 7/00 (20060101);
