Method for forming a refrigerant system

Abstract

1. A method for forming an improved centralized refrigeration system, comprising: (a) providing an existing high GWP refrigerant to an existing refrigeration circuit; (b) disconnecting a fluid connection between the existing liquid refrigerant from the condenser and an evaporator; (c) disconnecting a fluid connection between the existing refrigerant vapor from the evaporator and a compressor suction; (d) establishing a new first refrigeration circuit comprising a compressor and a condenser; and (e) establishing a new second refrigeration circuit comprising an evaporator by removing the existing refrigerant from the evaporator and the disconnected conduits and replacing the removed refrigerant with a second refrigerant that contains at least 50% R1234ze(E), is Class A1, and has an OEL greater than 400 and a GWP of about 150 or less; and thermally interconnecting the new first refrigeration circuit and the new second refrigeration circuit with an inter-circuit heat exchanger.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) The present invention is related to and claims priority benefit of U.S. Provisional Patent Application No. 63 / 309,214, filed February 11, 2022, which is incorporated by reference in its entirety herein.

[0002] The present invention relates to large centralized refrigeration systems, and in particular to a method for forming an improved decentralized refrigeration system based on a series of steps for modifying existing centralized systems, such as centralized supermarket refrigeration systems that use high global warming refrigerants, such as R404A, chlorodifluoromethane (R-22), etc. [Background technology]

[0003] Distributed refrigeration systems, such as those for refrigerated supermarket display cases, have typically employed air- or water-cooled condensers fed by a rack of compressors. Typically, the compressors are coupled in parallel so that they can be switched on and off in stages to adjust the cooling capacity of the system to the demands of the load, and the condensers are located outdoors, typically on the roof or in a machine room adjacent to the shopping area in which the refrigerated cases are located.

[0004] Within each refrigerated case is an evaporator fed by a line from a condenser through which expanded refrigerant circulates to cool the case. Because the cases are located on the retail floor of the supermarket and the condensers are located remotely on the roof or in machine shops inaccessible to consumers, long lengths of piping, valves and control systems connected by fittings are an essential feature of such existing systems.

[0005] Within supermarkets, it is common to use separate systems to supply different individual refrigeration temperature ranges to various retail cases. For example, low temperature cases contain frozen foods, ice cream, and the like, and are typically operated to maintain the contents at a temperature ranging from about -30°C to about -10°C, while medium temperature refrigeration is for display cases of meat, dairy, and the like, and has a typical goal of maintaining the contents at about -10°C to less than about 5°C. Each of these separate low and medium temperature systems typically constitutes its own centralized refrigeration system, and each usually employs its own compressor or rack of compressors, and its own set of refrigerant conduits leading to and from the compressor and condenser.

[0006] Centralized refrigeration systems, with their conventional configuration as generally described above, are expensive to build and maintain. One important component of this high cost is the long length of the refrigerant lines. Not only are long lines expensive in terms of hardware and installation costs, but the amount of refrigerant required to fill the lines is also a significant factor. The longer the line length, the more refrigerant is required. Environmental factors increase the cost of such systems. It has been common for such systems to use refrigerants that perform well in terms of heat transfer performance and safety (low or non-toxic and low or non-flammable), but are very disadvantageous from an environmental perspective in that they have a high global warming potential. For example, refrigerants (with GWP values ​​indicated according to IPCC AR5), R404A (GWP=3940), R22 (GWP=1760), R407F (GWP=1674), R448A (GWP=1273), R449A (GWP=1283) are frequently used in such systems. The fittings in such systems will eventually leak, allowing these environmentally harmful refrigerants to escape into the atmosphere. Moreover, longer runs contain more plumbing fittings, valves, etc. that can potentially leak, so if a leak does occur, the longer the run, the greater the amount of high GWP refrigerant that will be lost to the atmosphere.

[0007] Efforts to address the environmental deficiencies of such centralized refrigeration systems present significant engineering challenges due to the large costs associated with large-scale replacement of such expensive and large systems. Moreover, conventional roof mounted or machine room condenser / compressor systems provide high levels of efficiency and capacity, and any efforts to modify these systems to be more environmentally attractive should desirably maintain this efficiency and capacity.

[0008] Several thermodynamic and fluid flow challenges arise in connection with efforts to convert traditional centralized refrigeration systems to be more environmentally friendly while maintaining efficiency and capacity. For example, applicants have come to realize that it is very difficult, if not impossible, to identify environmentally friendly refrigerants (e.g., GWP of about 150 or less (as measured by AR5)) that can simply be used in existing centralized refrigeration systems to replace existing high GWP refrigerants. Previously disclosed alternatives to R-22 have been studied and shown to result in reduced cooling capacity and increased power requirements, thus resulting in an overall significant decrease in performance. (See WO 2020 / 223196(A1)). This indicates that it is difficult to develop a viable solution to this problem.

[0009] In addition, the use of compositions that are non-flammable is generally considered either important or essential in many applications, including particularly many central refrigeration systems. As used herein, the term "non-flammable" refers to a compound or composition that is measured to be non-flammable when measured according to ASTM Standard E-681-2009 Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases) under conditions described in ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants and in Appendix B1 of ASHRAE Standard 34-2016, which is incorporated herein by reference. Unfortunately, many HFCs that may be desirable as retrofits for existing central refrigeration systems are not non-flammable as used herein. For example, the fluoroalkane difluoroethane (HFC-152a) and the fluoroalkene 1,1,1-trifluoropropene (HFO-1243zf) are each flammable and therefore not viable for use in many applications.

[0010] With regard to efficiency of use, it is important to note that loss of thermodynamic performance or energy efficiency of the refrigerant can have secondary environmental impacts due to increased use of fossil fuels as a result of increased demand for electrical energy.

[0011] Applicants have therefore come to realise that it is possible to achieve significant advantages in the creation of a much more environmentally friendly centralised refrigeration system that is comparable to older systems in terms of thermodynamic performance, refrigerant safety (toxicity and flammability) and with only a relatively low capital cost outlay in terms of system infrastructure. Summary of the Invention

[0012] Applicants have discovered that the above needs, and other needs, may be met by a method for forming an improved centralized refrigeration system, the method comprising: (a) providing an existing refrigeration circuit comprising: (i) an existing refrigerant having a GWP greater than 1200; (ii) a plurality of evaporators located within or near a refrigerated space containing consumer accessible products; and (iii) at least one compressor or rack of compressors and at least one condenser located away from the consumer accessible area, wherein the existing refrigerant liquid from the condenser is fluidly connected to the evaporator via a conduit and wherein existing refrigerant vapor from the evaporator is returned via a conduit to a suction side of the compressor or compressor rack; (b) severing a fluid connection between the existing liquid refrigerant from the condenser and at least one of the evaporators, preferably substantially all of the evaporators; (c) severing a fluid connection between the existing refrigerant vapor from the at least one of the evaporators in step (b) and the suction of the compressor or compressor rack; (d) establishing a new first refrigeration circuit comprising the compressor or compressor rack and the condenser, wherein the existing refrigerant either remains in the first refrigeration circuit or is removed and replaced; (e)(i) removing the existing refrigerant from at least the portion of the evaporator and the conduit disconnected in steps (b) and (c); and (ii) replacing the removed existing refrigerant with a second refrigerant comprising: (1) at least about 50% by weight R1234ze(E); (2) greater than 0% to about 10% HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more thereof; and (3) about 10% to about 20% by weight HFO-1336mzz(E), HFO-1224yd(Z), and combinations thereof, wherein the second refrigerant (i) has an Occupational Exposure Limit (OEL) greater than 400; and (ii) is in compliance with ASHRAE 101(1)(v)(i)(v)(ii) of at least one of the evaporator and the conduit disconnected in steps (b) and (c). establishing a new second refrigeration circuit comprising at least one of the evaporators disconnected in steps (b) and (c), and preferably all of the evaporators, by steps including replacing the evaporators with refrigerated refrigerants classified as Class A1 by Standard 34 and (iii) having a GWP of about 150 or less; (f) thermally interconnecting the new first refrigeration circuit and the new second refrigeration circuit with an inter-circuit heat exchanger, where at least a portion of the refrigerant in the first circuit is evaporated by absorbing heat from the second circuit refrigerant vapor and at least a portion of the second refrigerant vapor is condensed by transferring heat to a refrigerant liquid in the first circuit. For convenience, the composition according to this paragraph is referred to herein as System Forming Method 1A.

[0013] The present invention also includes a method for forming an improved large capacity centralized refrigeration system, the method comprising: (a) providing an existing refrigeration circuit comprising: (i) an existing refrigerant having a GWP greater than 1200; (ii) a plurality of evaporators located within or near a refrigerated space containing consumer accessible products; and (iii) at least one compressor or rack of compressors and at least one condenser located away from the consumer accessible area, wherein the existing refrigerant liquid from the condenser is fluidly connected to the evaporator via a conduit and wherein existing refrigerant vapor from the evaporator is returned via a conduit to a suction side of the compressor or compressor rack; (b) severing a fluid connection between the existing liquid refrigerant from the condenser and at least one of the evaporators, preferably substantially all of the evaporators; (c) severing a fluid connection between the existing refrigerant vapor from the at least one of the evaporators in step (b) and the suction of the compressor or compressor rack; (d) establishing a new first refrigeration circuit including the compressor or compressor rack and the condenser, wherein the existing refrigerant is removed and replaced with a new first refrigerant different from the existing refrigerant; (e)(i) removing the existing refrigerant from at least a portion of the evaporator and the conduit disconnected in steps (b) and (c); and (ii) replacing the removed existing refrigerant with a second refrigerant comprising: (1) at least about 50% by weight R1234ze(E); (2) greater than 0% to about 10% HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more thereof; and (3) about 10% to about 50% by weight of one or more single component refrigerants having a combined GWP of less than about 150, wherein the second refrigerant (i) has an Occupational Exposure Limit (OEL) greater than 40; and (ii) an ASHRAE replacing said at least one of the evaporators disconnected in steps (b) and (c), preferably all of the evaporators, with a new second refrigeration circuit comprising at least one of the evaporators disconnected in steps (b) and (c), preferably all of the evaporators, classified as Class A1 by Standard 34, (iii) having a GWP of about 150 or less, and (iv) having a normal boiling point in the range of about -40°C to about 20°C; (f) thermally interconnecting the new first refrigeration circuit and the new second refrigeration circuit with a new inter-circuit heat exchanger, where at least a portion of the refrigerant of the first circuit is evaporated by absorbing heat from the second circuit refrigerant vapor and at least a portion of the second refrigerant vapor is condensed by transferring heat to a liquid of the first circuit. For convenience, compositions according to this paragraph are referred to herein as System Formation Method 1B.

[0014] The present invention also includes a method for forming an improved large capacity centralized refrigeration system, the method comprising: (a) providing an existing refrigeration circuit comprising: (i) an existing refrigerant having a GWP greater than 1200; (ii) a plurality of open display cases housing evaporators and located in or near a consumer accessible area; and (iii) at least one compressor or rack of compressors and at least one condenser located away from said consumer accessible area, wherein said existing refrigerant liquid from said condenser is fluidly connected to said evaporator via a conduit and wherein existing refrigerant vapor from said evaporator is returned via a conduit to a suction side of said compressor or compressor rack; (b) severing a fluid connection between the existing liquid refrigerant from the condenser and at least one of the evaporators, preferably substantially all of the evaporators; (c) severing a fluid connection between the existing refrigerant vapor from the at least one of the evaporators in step (b) and the suction of the compressor or compressor rack; (d) establishing a new first refrigeration circuit comprising said compressor or compressor rack and said condenser; and (e) establishing a new second refrigeration circuit with the evaporator in at least one of the open display cases disconnected in steps (b) and (c) by steps including: (i) removing the existing refrigerant from at least a portion of the evaporator and conduit disconnected in steps (b) and (c); (ii) replacing the removed existing refrigerant with a second refrigerant having (1) a GWP of about 150 or less, (2) a normal boiling point or normal boiling point range of about -40°C to about 20°C, (3) an Occupational Exposure Limit (OEL) of greater than 400, and (4) classified as Class 1A by ASHRAE Standard 34; and (iii) adding a retractable closure to the opening of the at least one display case, preferably all of the display cases. (f) thermally interconnecting the new first refrigeration circuit and the new second refrigeration circuit with a new inter-circuit heat exchanger, where at least a portion of the refrigerant in the first circuit is evaporated by absorbing heat from the second circuit refrigerant vapor and at least a portion of the second refrigerant vapor is condensed by transferring heat to a liquid in the first circuit. For convenience, compositions according to this paragraph are referred to herein as System Formation Method 1C.

[0015] The present invention also includes a method for forming an improved large capacity centralized refrigeration system, the method comprising: (a) providing an existing refrigeration circuit comprising: (i) an existing refrigerant having a GWP greater than 1200; (ii) a plurality of open display cases housing evaporators and located in or near a consumer accessible area; and (iii) at least one compressor or rack of compressors and at least one condenser located away from said consumer accessible area, wherein said existing refrigerant liquid from said condenser is fluidly connected to said evaporator via a conduit and wherein existing refrigerant vapor from said evaporator is returned via a conduit to a suction side of said compressor or compressor rack; (b) severing a fluid connection between the existing liquid refrigerant from the condenser and at least one of the evaporators, preferably substantially all of the evaporators; (c) severing a fluid connection between the existing refrigerant vapor from the at least one of the evaporators in step (b) and the suction of the compressor or compressor rack; (d) establishing a new first refrigeration circuit comprising said compressor or compressor rack and said condenser; and (e) establishing a new second refrigeration circuit with the evaporator in at least one of the open display cases disconnected in steps (b) and (c) by steps including: (i) removing the existing refrigerant from at least a portion of the evaporator and conduit disconnected in steps (b) and (c); (ii) replacing the removed existing refrigerant with a second refrigerant that (1) has a GWP of about 150 or less; (2) has a gradient (as defined herein) of less than 5° K; (3) has an Occupational Exposure Limit (OEL) of greater than 400; and (4) is classified as Class A1 by ASHRAE Standard 34; and (iii) adding retractable closures to the openings of the at least one display case, preferably all of the display cases. (f) thermally interconnecting the new first refrigeration circuit and the new second refrigeration circuit with a new inter-circuit heat exchanger, where at least a portion of the refrigerant in the first circuit is evaporated by absorbing heat from the second circuit refrigerant vapor and at least a portion of the second refrigerant vapor is condensed by transferring heat to a liquid in the first circuit. For convenience, the composition according to this paragraph is referred to herein as System Formation Method 1D.

[0016] The present invention also includes a method for forming an improved large capacity centralized refrigeration system, the method comprising: (a) providing an existing refrigeration circuit comprising: (i) an existing refrigerant having a GWP greater than 1200; (ii) a plurality of open display cases housing evaporators and located in or near a consumer accessible area; and (iii) at least one compressor or rack of compressors and at least one condenser located away from said consumer accessible area, wherein said existing refrigerant liquid from said condenser is fluidly connected to said evaporator via a conduit and wherein existing refrigerant vapor from said evaporator is returned via a conduit to a suction side of said compressor or compressor rack; (b) severing a fluid connection between the existing liquid refrigerant from the condenser and at least one of the evaporators, preferably substantially all of the evaporators; (c) severing a fluid connection between the existing refrigerant vapor from the at least one of the evaporators in step (b) and the suction of the compressor or compressor rack; (d) establishing a new first refrigeration circuit comprising the compressor or compressor rack and the condenser by removing the existing refrigerant from the compressor and the condenser and adding a new first refrigerant having a GWP of less than 1200; (e) establishing a new second refrigeration circuit with the evaporator in at least one of the open display cases disconnected in steps (b) and (c) by steps including: (i) removing the existing refrigerant from at least a portion of the evaporator and conduit disconnected in steps (b) and (c); (ii) replacing the removed existing refrigerant with a second refrigerant having (1) a GWP of about 150 or less; (2) a slope (as defined herein) of less than 5° K; (3) a normal boiling point of about -40°C to about 20°C; (4) an Occupational Exposure Limit (OEL) of greater than 400; and (5) a Class A1 classification according to ASHRAE Standard 34; and (iii) adding a retractable closure to the opening of the at least one display case, preferably all of the display cases. (f) thermally interconnecting the new first refrigeration circuit and the new second refrigeration circuit with a new inter-circuit heat exchanger, where at least a portion of the refrigerant in the first circuit is evaporated by absorbing heat from the second circuit refrigerant vapor and at least a portion of the second refrigerant vapor is condensed by transferring heat to a liquid in the first circuit. For convenience, the composition according to this paragraph is referred to herein as System Forming Method 1E.

[0017] The present invention also includes a method for forming an improved large capacity centralized refrigeration system, the method comprising: (a) providing an existing refrigeration circuit comprising: (i) an existing refrigerant having a GWP greater than 1200; (ii) a plurality of evaporators located within or near a refrigerated space containing consumer accessible products; and (ii) at least one compressor or rack of compressors and at least one condenser located away from the consumer accessible area, wherein the existing refrigerant liquid from the condenser is fluidly connected to the evaporator via a conduit and the existing refrigerant vapor from the evaporator is returned via a conduit to the suction side of the compressor or compressor rack; (b) severing a fluid connection between the existing liquid refrigerant from the condenser and at least one of the evaporators, preferably substantially all of the evaporators; (c) severing a fluid connection between the existing refrigerant vapor from the at least one of the evaporators in step (b) and the suction of the compressor rack; (d) establishing a new first refrigeration circuit including the compressor rack and the condenser, wherein the existing refrigerant is removed and replaced with a new first refrigerant different from the existing refrigerant; (e) establishing a new second refrigeration circuit comprising at least one of the evaporators disconnected in steps (b) and (c), and preferably all of the evaporators disconnected in steps (b) and (c), by steps including: (i) removing the existing refrigerant from at least a portion of the evaporators and conduits disconnected in steps (b) and (c); and (ii) replacing the removed existing refrigerant with a second refrigerant that contains at least about 50% by weight R1234ze(E), (1) has a GWP of about 150 or less, (2) has a normal boiling point or a normal boiling range of about -40°C to 20°C, (3) is nonflammable according to ASHRAE Standard 34, and (4) has an occupational exposure limit (OEL) of greater than 400. (f) thermally interconnecting the new first refrigeration circuit and the new second refrigeration circuit with a new inter-circuit heat exchanger, where at least a portion of the refrigerant of the first circuit is evaporated by absorbing heat from the second circuit refrigerant vapor and at least a portion of the second refrigerant vapor is condensed by transferring heat to a liquid of the first circuit. For convenience, compositions according to this paragraph are referred to herein as System Formulation Method 2A.

[0018] The present invention also includes a method for forming an improved large capacity centralized refrigeration system, the method comprising: (a) providing an existing refrigeration circuit comprising: (i) an existing refrigerant having a GWP greater than 1200; (ii) a plurality of open display cases housing evaporators and located in or near a consumer accessible area; and (iii) at least one compressor or rack of compressors and at least one condenser located away from the consumer accessible area, wherein the existing refrigerant liquid from the condenser is fluidly connected to the evaporator via a conduit and the existing refrigerant vapor from the evaporator is returned via a conduit to a suction side of the compressor rack; (b) severing a fluid connection between the existing liquid refrigerant from the condenser and at least one of the evaporators, preferably substantially all of the evaporators; (c) severing a fluid connection between the existing refrigerant vapor from the at least one of the evaporators in step (b) and the suction of the compressor or compressor rack; (d) establishing a new first refrigeration circuit including the compressor rack and the condenser, wherein the existing refrigerant is removed and replaced with a new first refrigerant different from the existing refrigerant; (e) establishing a new second refrigeration circuit comprising at least one of the evaporators disconnected in steps (b) and (c), and preferably all of the evaporators disconnected in steps (b) and (c), by steps including: (i) removing the existing refrigerant from at least a portion of the evaporators and conduits disconnected in steps (b) and (c); and (ii) replacing the removed existing refrigerant with a second refrigerant that contains at least about 50% by weight R1234ze(E) and that (1) has a GWP of less than about 150, (2) has a normal boiling point or normal boiling range of about -40°C to 20°C, (3) has a slope (as defined herein) of less than 5°K, (4) is nonflammable according to ASHRAE Standard 34, and (5) has an occupational exposure limit (OEL) of greater than 400. (f) thermally interconnecting the new first refrigeration circuit and the new second refrigeration circuit with a new inter-circuit heat exchanger, where at least a portion of the refrigerant of the first circuit is evaporated by absorbing heat from the second circuit refrigerant vapor and at least a portion of the second refrigerant vapor is condensed by transferring heat to a liquid of the first circuit. For convenience, compositions according to this paragraph are referred to herein as System Formulation Method 2B. [Brief description of the drawings]

[0019] [Figure 1]FIG. 1 is a semi-schematic process flow diagram illustrating a centralized refrigeration system according to the prior art. [Diagram 2] FIG. 1 is a semi-schematic view of an exemplary start-up centralized refrigeration system for use in the heat transfer system formation method of the present invention. [Figure 3A] FIG. 1 is a schematic diagram of an exemplary start-up centralized refrigeration system illustrating the cut points in the process of forming the heat transfer system of the present invention. [Figure 3B] FIG. 1 is a schematic diagram of an exemplary completed centralized refrigeration system made in accordance with the heat transfer system formation method of the present invention. [Figure 4] FIG. 1 is a schematic diagram of the process flow described in Example 1D. [Diagram 5] FIG. 1 is a schematic diagram of the process flow described in Example 4A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] definition For purposes of the present invention, the term "about" in relation to amounts expressed as weight percent for amounts greater than 2% means that the amount of the component can vary by an amount of ±2% by weight.

[0021] For purposes of the present invention, the term "about" in reference to temperatures in degrees Celsius (°C) means that the stated temperature can vary by an amount of + / - 5°C.

[0022] For purposes of this invention, the term "about" in relation to power usage percentages means that the stated percentage may vary by up to 1%.

[0023] For purposes of this invention, the term "substantial portion" with respect to removing existing refrigerant from a heat transfer system means removing at least about 50% of the existing refrigerant contained in the system.

[0024] The term "capacity" is the amount of cooling (BTU / hr or kW) provided by a refrigerant in a refrigeration system. It is determined experimentally by multiplying the change in enthalpy in BTU / lb or kJ / kg of the refrigerant as it passes through the evaporator by the mass flow rate of the refrigerant. Enthalpy can be determined from measurements of the refrigerant pressure and temperature. The capacity of a refrigeration system is related to its ability to maintain a particular temperature in an area to be cooled. The capacity of a refrigerant represents the amount of cooling or heating it provides and provides a measure of the compressor's ability to pump that amount of heat for a given volumetric flow rate of refrigerant. In other words, given a particular compressor, a refrigerant with a higher capacity will provide more cooling or heating power.

[0025] The phrase "coefficient of performance" (hereinafter "COP") is a widely accepted measure of refrigerant performance that is particularly useful for expressing the relative thermodynamic efficiency of a refrigerant in a particular heating or cooling cycle involving evaporation or condensation of the refrigerant. In refrigeration, the term represents the ratio of the available refrigeration or cooling capacity to the energy applied by the compressor during compression of the vapor, and thus the ability of a given compressor to pump a quantity of heat for a given volumetric flow rate of a heat transfer fluid such as a refrigerant. In other words, given a particular compressor, a refrigerant with a higher COP will deliver more cooling or heating power. One means for estimating the COP of a refrigerant at a particular operating condition 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, which is incorporated herein by reference in its entirety).

[0026] The phrase "discharge temperature" refers to the temperature of the refrigerant at the outlet of the compressor. The advantage of a low discharge temperature is that it preferably allows the use of existing equipment without activating the thermal protection aspects of the system designed to protect the compressor components, and avoids the use of expensive control devices such as liquid injection to reduce the discharge temperature.

[0027] As used herein, the term "centralized refrigeration system" means a refrigeration system that includes one or more centrally located compressors or racks of compressors, one or more centrally located condensers, and a number of evaporators located away from the centralized compressors or racks of compressors and that receive liquid refrigerant from the centrally located condensers.

[0028] As used herein, "direct expansion" refers to a heat transfer system utilizing an evaporator where liquid refrigerant enters the evaporator, flows through a coil (preferably a tubular coil), and evaporates as heat is absorbed from the air circulating within the display case, using a thermostatic expansion valve at the inlet of the evaporator, and controlled to provide enough refrigerant so that substantially all of the refrigerant is evaporated at the evaporator outlet, and optionally have a predetermined amount of superheat at the outlet.

[0029] The phrase "Global Warming Potential" (hereinafter "GWP") was developed to allow for the comparison of the global warming impact of different gases, and as used herein refers to the GWP determined by the AR5 as described above. Specifically, it is a measure of how much energy the emission of one ton of a gas absorbs over a given period of time, relative to the emission of one ton of carbon dioxide. The higher the GWP, the more a given gas will warm the earth over that period, compared to CO2. The period typically used for GWP is 100 years. GWP provides a common measure that allows analysts to add up emission estimates of different gases. See http: / / www.protocolodemontreal.org.br / site / images / publicacoes / setor_manufatura_equipamentos_refrigeracao_arcondicionado / Como_calcular_el_Potencial_de_Calentamiento_Atmosferico_en_las_mezclas_de_refrigerantes.pdf.

[0030] The term "Occupational Exposure Limit (OEL)" is determined in accordance with ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants.

[0031] As used herein, the phrase "acceptably toxic" means that the composition is classified as Class "A" by ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants and is described in Appendix B1 of ASHRAE Standard 34-2016, as such standards exist as of the filing date of this application. A material that is non-flammable and has low toxicity is classified as "A1" by ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants and is described in Appendix B1 of ASHRAE Standard 34-2016, as such standards exist as of the filing date of this application.

[0032] The term "mass flow" is the mass of refrigerant passing through a conduit per unit time.

[0033] As used herein, the term "replacement" refers to the use of the compositions of the present invention in a heat transfer system designed for or suitable for use with another refrigerant. For example, when the refrigerant or heat transfer composition of the present invention is used in a heat transfer system designed for use with R-410A, the refrigerant or heat transfer composition of the present invention is a replacement for R-410A in that system. Thus, the term "replacement" will be understood to include the use of the refrigerant and heat transfer composition of the present invention in both new and existing systems designed for use with R-410A, commonly used with R-410A, or suitable for use with R-410A.

[0034] The term "glide" applies to non-azeotropic refrigerant mixtures that have different temperatures during the phase change process in the evaporator or condenser at constant pressure, and is quantified herein as the difference between the saturated vapor temperature and the saturated liquid temperature at a pressure of 100 kPa.

[0035] The term "low temperature refrigeration system" refers to a heat transfer system that operates at a condensing temperature of about 40° C. to about 70° C., and an evaporating temperature of about -45° C. to -12° C., inclusive.

[0036] The term "medium temperature refrigeration system" refers to a heat transfer system that operates at a condensing temperature of about 40°C to about 70°C, and an evaporating temperature of -12°C to about 0°C.

[0037] As used herein, the term "supermarket refrigeration" refers to commercial refrigeration systems used to keep foods cool or frozen, both in product display cases and in storage refrigerators.

[0038] The term "normal boiling point" refers to the boiling point of a single component measured at one atmosphere and refers to the initial boiling point of a blend of components at one atmosphere.

[0039] The term "R22" means chlorodifluoromethane.

[0040] As used herein, the terms "HFC32" and "R32" each mean difluoromethane.

[0041] The terms "HFC-125" and "R125" mean pentafluoroethane.

[0042] The terms "HFC-134a" and "R134a" mean 1,1,1,2-tetrafluoroethane.

[0043] The terms "HFC-134" and "R134" mean 1,1,2,2-tetrafluoroethane.

[0044] The term "R143a" means 1,1,1-trifluoroethane.

[0045] The term "R290" means propane.

[0046] The term "R404A" refers to a combination of about 44% by weight R-125, about 52% by weight R143a, and about 4% by weight R-134a.

[0047] The term "R407A" refers to a combination of about 20% by weight R-32, about 40% by weight R125, and about 40% by weight R-134a.

[0048] The term "R407B" refers to a combination of about 10% by weight R-32, about 70% by weight R125, and about 20% by weight R-134a.

[0049] The term "R407C" refers to a combination of about 23% by weight R-32, about 25% by weight R125, and about 52% by weight R-134a.

[0050] The term "R407D" refers to a combination of about 15% by weight R-32, about 15% by weight R125, and about 70% by weight R-134a.

[0051] The term "R407F" refers to a combination of about 40% by weight R-32, about 30% by weight R125, and about 30% by weight R-134a.

[0052] The term "R407" means any of R407A, R407B, R407C, R407D, and R407F.

[0053] The term "R448A" refers to a combination of about 26% by weight R-32, about 26% by weight R125, and about 21% by weight R-134a.

[0054] The term "R448A" refers to a combination of about 26% by weight R-32, about 26% by weight R125, and about 21% by weight R-134a.

[0055] The term "R448" refers to the refrigerant designated as R448 with any letter designation, including R448A.

[0056] The term "R449A" refers to a combination of about 24.3% by weight R-32, about 24.7% by weight R125, and about 25.7% by weight R-134a.

[0057] The term "R449" refers to the refrigerant designated as R449 with any letter designation, including R449A.

[0058] The term "R454B" refers to a combination of about 68.9% by weight R-32 and about 31.1% by weight R1234yf.

[0059] The term "R454" refers to the refrigerant designated as R454 with any letter designation, including R454B.

[0060] The term "R513A" refers to a combination of about 44% by weight R-134a and about 56% by weight R1234yf.

[0061] The term "R449" refers to the refrigerant designated as R449 with any letter designation, including R449A.

[0062] As used herein, the terms "HFO1234yf" and "R1234yf" each mean 2,3,3,3-tetrafluoropropene.

[0063] As used herein, the terms "HFO1234ze(E)", "R1234ze(E)", and "1234ze(E)" each mean trans-1,3,3,3-tetrafluoropropene.

[0064] Reference herein to a group of defined terms includes all such defined terms, including all such terms with the suffix designation.

[0065] Systems and methods The method of the present invention generally includes a first step of providing an existing centralized refrigeration system. A schematic example of such a centralized refrigeration system is shown in FIG. 1, which shows a system including a rack of compressors 30, a condenser 32, an accumulator 38, and a series of display cases 34, each housing an evaporator 42. A high GWP refrigerant, such as R-404a, circulates in such a system through a piping network 46 carrying liquid refrigerant and a piping network 48 carrying refrigerant vapor. Although shown diagrammatically in FIG. 1, in reality, each of these piping networks generally represents a wide and long series of conduits for transporting liquid refrigerant from the accumulators 38, which, together with the compressor racks 30 and condensers 32, are generally located away from the display cases. The piping network 46 is therefore large, covering distances, for example, from the roof or machine room of the supermarket to extending over the supermarket floor to reach the numerous display cases located in the supermarket. 1 shows only two display cases, one skilled in the art will recognize that in many situations there will be from one to about 150 display cases per circuit distributed over a large consumer retail area that needs to be reached by liquid piping network 46, and an equally large vapor return piping network 48 required to return refrigerant vapor to the roof or mechanical room in each of these cases. In many applications, the length of piping required for the liquid supply from the compressor and the vapor return to the compressor is at least about 20 meters (65 feet).

[0066] 1 is shown as having four compressors 30, those skilled in the art will also recognize that in practice, the compressor rack may include from one to about five compressors depending on the particular application. In other words, the existing refrigerant system provided in accordance with the present invention may exhibit a compressor work capacity of about 3 kW to about 500 kW. With respect to the type of compressor, it is contemplated that all types of compressors may be present in such systems, but in many such systems, the compressors used are selected from screw compressors, scroll compressors, reciprocating compressors, centrifugal compressors, twin screw compressors, and combinations thereof.

[0067] Existing refrigerants used in the existing centralized refrigeration systems of the present invention generally have a GWP (determined in accordance with AR5) of 1200 or greater and include R404A, R22 and R407 (including each of R407A, R407B, R407C, R407D), R448 (all letter designations), and R449 (all letter designations).

[0068] The present invention includes improving a system of the type disclosed in FIG. 1 to improve the environmental friendliness of the system. A preferred method includes disconnecting the liquid connection between at least one, and preferably all, of the condenser and the evaporator, and also disconnecting the vapor connection between the evaporator and the suction of the compressor. For example, with reference to FIG. 2A, FIG. 2B and FIG. 2C, the liquid line 14 is preferably disconnected immediately downstream of the accumulator 13 to separate the liquid side of the evaporator from the liquid from the condenser 12, and the vapor line 15 is preferably disconnected immediately upstream of the compressor to separate the vapor side of the evaporator from the compressor. This disconnection step thus allows the conversion of an existing single refrigeration circuit into a new first refrigeration circuit and a new second refrigeration circuit (see, for example, 10A and 10B, respectively, in FIG. 3C). It will be appreciated that the term "new" as used herein in this context means only that a circuit as defined by the present invention did not previously exist, but one objective of the present invention is to utilize most of the "old" piping network and the "old" evaporator as part of a new, second refrigeration circuit. In some preferred embodiments, it is also an objective to use the "old" compressor, condenser, and accumulator, and the piping and valves between them, to form a second, new refrigeration circuit.

[0069] Either prior to, simultaneous with, or after the disconnection step, the existing refrigerant is removed from the liquid and vapor piping network that remains connected to the evaporators, the evaporators themselves, and all other piping, valves, etc., that are used to form a new second refrigeration circuit, such as circuit 10B in FIG. 3C. A preferred second circuit, one example of which is shown in FIG. 3C, is formed by including a liquid pump 21, which in a preferred embodiment is supplied with cold liquid refrigerant by an accumulator 22. The pump provides the motive force for transporting the second refrigerant from the compressor to each of the evaporators that have been disconnected. The liquid refrigerant in the second circuit 10B provides cooling to the display case as it evaporates in the evaporators by absorbing heat from the air and / or products in the display case.

[0070] An important aspect of the present invention is that the vapor from the evaporator is not returned to the compressor as in the original system, but instead the present invention includes the step of thermally interconnecting the new first refrigeration circuit 10A and the new second refrigeration circuit 10B with a new intercircuit heat exchanger 20. The vapor from the evaporator travels to this intercircuit heat exchanger where at least a portion of the second refrigerant is condensed by transferring heat to liquid refrigerant exiting a condenser in the new first circuit, thereby evaporating the first refrigerant and producing refrigerant that feeds the compressor 11 of the first circuit. In this configuration the intercircuit heat exchanger functions as an evaporator in the first circuit and as a condenser in the second circuit.

[0071] Importantly, the method involves using in the new second circuit a low GWP refrigerant that has a GWP of 150 or less and is preferably a Class A1 refrigerant with an OEL of greater than 400, and has a normal boiling point between -40° C. and 20° C. Table A below identifies four refrigerant blends A1, A2, A3 and A3′ that meet these criteria and provide substantial unexpected advantages in accordance with the present invention, with it being understood that all amounts in the table are considered to be preceded by "about."

[0072] [Table 1]

[0073] In a preferred embodiment, the refrigerant in the second circuit is selected from within the ranges of components specified in Table B below, with it being understood that all amounts in the table are deemed to be preceded by "about."

[0074] [Table 2]

[0075] In a preferred embodiment, the refrigerant in the second circuit has a normal boiling point within the ranges specified in Table C below, with it being understood that all amounts in the table are deemed to be preceded by "about."

[0076] [Table 3]

[0077] In a preferred embodiment, the refrigerant in the second circuit has a gradient within the ranges specified in Table D below, it being understood that all amounts in the table are deemed to be preceded by "about."

[0078] [Table 4]

[0079] Refrigerant Combination It is contemplated that the existing refrigerant contained in the piping and equipment associated with the condenser and compressor (i.e., the new first refrigeration circuit) can be left and used as the refrigerant for the new first circuit, or it can be removed and replaced in whole or in part with a new refrigerant, preferably with a lower GWP. In those embodiments in which the existing refrigerant in the new first circuit remains, it is contemplated that the existing equipment, including the compressor, condenser, accumulator, connecting piping, etc., does not need to be replaced either. Such an embodiment has the advantage of minimizing the increase in capital equipment costs, but results in a high GWP refrigerant being utilized in the new first refrigeration circuit. While such an arrangement has significant environmental benefits, since the amount of high GWP refrigerant used in the converted system is significantly reduced compared to the original system, in another embodiment, the existing refrigerant is removed from the compressor, condenser, accumulator, connecting piping, etc., and a new low GWP refrigerant is used to replace all or substantially all of the existing refrigerant, or some other portion. In such an embodiment, one or more, or all of those parts of the system will likely need to be replaced and / or modified, which in turn increases capital expenditures. However, proceeding according to an embodiment in which high GWP refrigerants are removed from the first circuit provides the most desirable results from an environmental standpoint, as it provides a conversion system in which only low GWP refrigerants are used. Generally, in such an embodiment, the new refrigerant for the first circuit has a GWP of less than 150, more preferably less than 100, and even more preferably less than about 25. Examples of low GWP refrigerants for use in the new first refrigerant circuit in such an embodiment include 1234ze(E), 1234yf, and blends containing these.

[0080] As will be appreciated by those skilled in the art, the present invention includes methods of forming a heat transfer system that combine a wide range of existing centralized refrigeration systems with existing refrigerants with various specific refrigerants that may be used in the new second circuit and, optionally, as a replacement for the existing refrigerant in the new first circuit. Possible combinations include the methods of the present invention, including each of the methods defined by system formation methods 1-2 set forth in Table C below. As used herein, references to system formation methods defined by numbers, such as system formation method 1, are intended and understood to include each such numbered reference with the suffix. Thus, for example, reference to system formation method 1 includes specific references to each of system formation methods 1A-1E. Additionally, the system formation methods as numbered in the first column of the table below are understood to be definitions of the indicated numbered system formation methods.

[0081] [Table 5-1]

[0082] [Table 5-2]

[0083] [Table 5-3]

[0084] [Table 5-4]

[0085] [Table 5-5]

[0086] device This method, including each of system formation methods 1-26, includes forming a new second refrigeration circuit, including adding a liquid pump fluidly connected between the liquid second refrigerant exiting the inter-circuit heat exchanger and the inlet of the evaporator of the second circuit.

[0087] The method, including each of system formation methods 1-26, includes forming a new second refrigeration circuit, including including a liquid ejector fluidly connected between vapor exiting the evaporator of the second refrigerant and an inlet to the inter-circuit heat exchanger.

[0088] The method, including each of system formation methods 1-26, includes forming a new second refrigeration circuit including: (a) including a liquid pump fluidly connected between the liquid second refrigerant exiting the inter-circuit heat exchanger and an inlet of an evaporator of the second circuit; and (b) including a liquid ejector fluidly connected between the vapor exiting the evaporator of the second refrigerant and an inlet to the inter-circuit heat exchanger.

[0089] This method, including each of system formation methods 1-26, includes the step of forming a new second refrigeration circuit, including including a thermostatic expansion valve at the inlet of the evaporator.

[0090] The method, including each of system formation methods 1-26, includes forming a new second refrigeration circuit including including (a) a liquid pump fluidly connected between the liquid second refrigerant exiting the inter-circuit heat exchanger and an inlet of an evaporator of the second circuit, and (b) a thermostatic expansion valve at the inlet of the evaporator.

[0091] The method, including each of system formation methods 1-26, includes forming a new second refrigeration circuit including: (a) including a liquid pump fluidly connected between the liquid second refrigerant exiting the inter-circuit heat exchanger and an inlet of an evaporator of the second circuit; (b) including a liquid ejector fluidly connected between the vapor exiting the evaporator of the second refrigerant and an inlet to the inter-circuit heat exchanger and a thermostatic expansion valve at the inlet of the evaporator; and (c) including a thermostatic expansion valve at the inlet of the evaporator.

[0092] The present methods, including each of the system formation methods 1-26, include methods in which an existing centralized refrigeration system includes a compressor rack with at least two compressors.

[0093] The present methods, including each of system formation methods 1-26, include methods in which an existing centralized refrigeration system includes at least about five evaporators.

[0094] The present methods, including each of system formation methods 1-26, include methods in which an existing centralized refrigeration system includes at least about five evaporators that operate to provide medium temperature refrigeration.

[0095] The present methods, including each of system formation methods 1-26, include a method in which an existing centralized refrigeration system includes at least about five evaporators operative to provide mid-temperature refrigeration associated with at least five display cases.

[0096] The present methods, including each of system formation methods 1-26, include a method in which an existing centralized refrigeration system includes at least about five evaporators operative to provide mid-temperature refrigeration associated with at least five open display cases.

[0097] The methods, including each of system formation methods 1-26, include a method in which (1) an existing centralized refrigeration system includes at least about five evaporators operative to provide mid-temperature refrigeration associated with at least five open display cases, and (2) a new second circuit refrigeration system includes at least one of the five open display cases that is converted to a closed display case.

[0098] The methods, including each of System Formation Methods 1-26, include a method in which (1) an existing centralized refrigeration system includes at least one evaporator operative to provide medium temperature refrigeration associated with at least one open display case, and (2) a new second circuit refrigeration system includes the at least one open display case that is converted to a closed display case.

[0099] The methods, including each of system formation methods 1-26, include a method in which (1) an existing centralized refrigeration system includes at least one evaporator operative to provide medium temperature refrigeration associated with at least one open display case, and (2) a new second circuit refrigeration system includes (i) the at least one open display case that is converted to a closed display case, and (ii) a liquid pump fluidly connected between a liquid second refrigerant exiting the inter-circuit heat exchanger and an inlet of the evaporator of the at least one second circuit.

[0100] The methods, including each of system formation methods 1-26, include a method in which (1) an existing centralized refrigeration system includes at least one evaporator operative to provide medium temperature refrigeration associated with at least one open display case, and (2) a new second circuit refrigeration system includes (i) the at least one open display case being converted to a closed display case, (ii) a liquid pump fluidly connected between a liquid second refrigerant exiting the inter-circuit heat exchanger and an inlet of the at least one second circuit evaporator, and (iii) a liquid ejector fluidly connected between vapor exiting the at least one second refrigerant evaporator and an inlet to the inter-circuit heat exchanger.

[0101] The methods, including each of system formation methods 1-26, include a method in which (1) an existing centralized refrigeration system includes at least one evaporator operative to provide medium temperature refrigeration associated with at least one open display case, and (2) a new second circuit refrigeration system includes (i) the at least one open display case that is converted to a closed display case, (ii) a liquid pump fluidly connected between a liquid second refrigerant exiting the inter-circuit heat exchanger and an inlet of an evaporator of the at least one second circuit, and (iii) a thermostatic expansion valve at the inlet of the at least one evaporator.

[0102] The present methods, including each of system formation methods 1-26, include a method in which (1) an existing centralized refrigeration system includes at least one evaporator operative to provide medium temperature refrigeration associated with at least one open display case, and (2) a new second circuit refrigeration system includes (i) the at least one open display case being converted to a closed display case, (ii) a liquid pump fluidly connected between a liquid second refrigerant exiting the inter-circuit heat exchanger and an inlet of the at least one second circuit evaporator, (iii) a thermostatic expansion valve at the inlet of the at least one evaporator, and (iv) a liquid ejector fluidly connected between vapor exiting the at least one second refrigerant evaporator and an inlet to the inter-circuit heat exchanger. EXAMPLES

[0103] The following examples are offered for the purpose of illustrating the present invention, but not limiting its scope.

[0104] For evaluation of possible ways to improve an existing centralized refrigeration system to make it more environmentally friendly, including for comparative purposes by essentially removing the entire charge of an existing high GWP refrigerant and replacing it with a lower GWP refrigerant, it is important to consider performance parameters such as: (1) the volumetric flow rate of the refrigerant in the system to achieve the same cooling capacity, (2) the mass flow rate of the refrigerant in the system to achieve the same cooling capacity, (3) the density of the refrigerant, and (4) the pressure drop ratio.

[0105] Comparative Example C1 - Large Capacity Centralized Refrigeration System Using R-404A as the Refrigerant in Medium Temperature Applications A large capacity (i.e., 243 kW cooling capacity) direct expansion central refrigeration system of the type disclosed in Figure 1 is equipped with R-404A as the existing refrigerant. The system operating conditions using R-404A as the refrigerant in the system of Figure 1 are as follows: Cooling capacity: 243kW Isentropic efficiency: 0.7 Volumetric efficiency: 1 Condensation temperature: 56.85℃ Supercooling: 5℃ Overheating: 10℃ Evaporation temperature: -3.15℃

[0106] 0.1m 3 Based on the volumetric flow rate to establish a baseline value of 26.8 kg / m 3 and a mass flow rate of 2.68 kg / sec. While this system works well from a thermodynamic and heat transfer performance standpoint, it is highly undesirable from an environmental impact standpoint since the entire system involves the high GWP refrigerant R404A circulating throughout a large and complex network of piping.

[0107] Comparative Example C2 - Large Capacity Centralized Refrigeration System Using R-471A to Replace R-401A in Medium Temperature Applications Comparative Example 1 is repeated, except that all of the R-404A refrigerant is removed from the system and, with no other changes made to the system, the R-404A refrigerant is replaced with the low GWP refrigerant R-471A. Specifically, R-471A is a refrigerant composed of the following components in the following relative amounts:

[0108] [Table 6]

[0109] However, making this substitution does not achieve the primary goal of maintaining performance while minimizing environmental impact. Specifically, based on the same operating conditions specified in Comparative Example 1, substantial and undesirable changes in refrigerant volumetric flow rate, mass flow density, and pressure drop ratio result from simply substituting R471A for R404A in this manner, as shown in Table C2 below.

[0110] [Table 7]

[0111] As can be seen from the results in Table C2 above, replacing the existing R-404A with R-417A improves the system in terms of containing a low GWP refrigerant, but produces unacceptable performance in terms of a high (i.e., greater than 1) pressure drop ratio, which means that compression system performance is significantly degraded. In addition, this high pressure drop ratio means that the existing piping is not suitable for continued operation of the system, and that continued reliable system operation will require disassembly and replacement of the old piping network, and possibly other significant system modifications.

[0112] Comparative Example C3 - Large Capacity Centralized Refrigeration System Using R-1234ze to Replace R-404A in Medium Temperature Applications Comparative Example 1 is repeated, except that all of the R-404A refrigerant is removed from the system and replaced with low GWP refrigerants 1234ze(E) or 1234yf, with no other changes to the system. The use of R-1234ze(E) or R-1234yf improves the system in terms of including a low GWP refrigerant (less than 1), but is nevertheless a solution that has the drawback that neither refrigerant is non-flammable.

[0113] Comparative Example C4 - Large Capacity Centralized Refrigeration System Using CO2 to Replace R-404A in Medium Temperature Applications Comparative Example 1 is repeated, except that all of the R-404A refrigerant is removed from the system and replaced with a low GWP refrigerant or CO2, without making any other changes to the system. The use of CO2 improves the system in terms of including a low GWP refrigerant, but is nevertheless an unacceptable solution for several reasons. First, CO2 is a very high pressure fluid compared to R404A, and as a result, R-404A piping does not accommodate CO2 well. Second, even if all piping is replaced (which is a costly and undesirable requirement), the CO2 system requires that all CO2 be completely vented to the atmosphere in the event of a system failure, which in turn leads to high CO2 emissions and food loss in the display cabinet. Third, CO2 as a replacement for a direct expansion refrigerant in such a system results in a reduced efficiency (COP) at medium and high temperature ambient conditions, resulting in high power consumption and high indirect CO2 emissions.

[0114] Comparative Example C5 - Centralized Refrigeration System Using R-404A as the Refrigerant in Medium Temperature Applications As shown diagrammatically in FIG. 2, a direct expansion central refrigeration system with a cooling capacity of 45 kW in a medium temperature refrigeration application has R-404A as the existing refrigerant. The system comprises a refrigeration circuit 10 with a rack of compressors (three compressors are shown, but any number of compressors can be used according to specific design considerations to meet the compression capacity required for each particular system). The R-404A refrigerant vapor discharged from the compressors in the rack 11 is fed to a condenser 12 (which may include multiple condensers) that uses the surrounding outside air to absorb heat from the refrigerant vapor and condense it. The heated air is then discharged to the surroundings. The refrigerant liquid leaves the condensers and enters accumulators 13, which contain a supply of liquid refrigerant to feed the evaporators (evaporators 1-5) in their respective display cases. The dotted lines in FIG. 2 represent that the compressor rack 11, condensers 12, and accumulators 13 are located away from the display case locations (preferably with limited access by the public). The operating conditions of the portion of the circuit including the compressors and condensers are given below. Condensation pressure: 2558kPa Condensation temperature: 55℃ Evaporation pressure: 439kPa Evaporation temperature: -10℃ The liquid refrigerant supply pipe 14 transports the liquid refrigerant over long distances at high pressures of approximately 2585 kPa, and the combination of long transport distances and high pressures results in a high rate of refrigerant leakage. The liquid refrigerant arrives at the inlet of the expansion valve of each of the evaporators, and each evaporator is designed to provide the indicated levels of medium temperature cooling, as reported in Table CE5 below, along with other operating conditions for this portion of the system.

[0115] [Table 8]

[0116] Although not shown to scale in Figure 2, the system piping on the vapor outlet side of the evaporator is referenced to nodes a through j in Figure 2 and carries refrigerant vapor at a pressure of approximately 439 kPa. As with the liquid lines, the large distances that the piping covers to return the vapor to the compressor racks combined with the relatively high pressure of 439 kPa also results in a high rate of refrigerant leakage on the vapor side of the system. The lengths of piping between the nodes, and the sizes of the copper piping between each node are shown in Table CE5C below.

[0117] [Table 9]

[0118] Example 1A - Modifying the original system using R-404A and replacing R404A with refrigerant A1 (R-471A) to create centralized refrigeration The heat transfer system of Comparative Example 5 (including the existing refrigerant R404A contained therein) is used as a starting point to form an improved heat transfer system. The modification of the system is first described in relation to FIG. 3A. A portion of the system including the condenser 12, compressor rack 11, and accumulator 13 is disconnected from the display case, preferably near where the compressor rack and accumulator are located, for example, by disconnecting the liquid line 14 leading from the accumulator and by disconnecting the vapor riser 15 leading to the compressor rack. The R404A located in this portion of the system does not need to be removed, but can be removed optionally. In this example, the refrigerant in this portion of the system (above the dotted line) is not removed and is used in the modified system. However, the R404A located in the remaining portion of the system (below the dotted line) is removed from all of the remaining refrigerant conduits and all evaporators.

[0119] As shown in FIG. 3B, the system is then reconfigured as a first heat transfer system 10A using the original R404A (or other high GWP refrigerant that has been commonly used in centralized systems), and a second heat transfer circuit 10B with evaporators 1-5 and using a new low GWP refrigerant according to the present invention (in this example 1, R471A). The new heat exchanger 20 thermally interconnects the first heat transfer circuit 10A to the second heat transfer circuit 10B by transporting the liquid R404A refrigerant from the accumulator, preferably over a relatively short distance in conduit 14A, to the intercircuit heat exchanger 20, which absorbs heat from the new refrigerant in the second circuit to evaporate the liquid R404A refrigerant. The evaporated R-404A is then returned to the suction side of the compressor rack via conduit 15A, which also preferably extends over a relatively short distance.

[0120] A liquid pump 21 is added to the second circuit system to provide the motive force to deliver the low GWP refrigerant R471A to each of the evaporators via their respective conduits and valves. In each evaporator, the R471A refrigerant evaporates in thermal contact with the relatively warm air within the display case, thus cooling its respective display case. The R471A vapor exiting evaporators 1-5 is then manifolded to riser 15B where it is transported to intercircuit heat exchanger 20 where it gives up heat to liquid R-404A from the first circuit, and in so doing condenses back into a liquid. The liquid R471A from heat exchanger 20 travels via conduit 14B to accumulator 22, which provides a source of liquid R471A to pump 21.

[0121] The R471A refrigerant in the second circuit operates as a two-phase refrigerant between the condensers where it condenses as a saturated liquid at about -6°C (the condenser pressure is about 160 kPa) and in each of the evaporators the R471A evaporates at a temperature of about -3°C, with an average evaporation temperature of about -2°C. The R471A evaporates completely in each evaporator and the return flow of refrigerant R471A vapour through the riser 15B is saturated or superheated.

[0122] Table E1 below demonstrates that by using the existing piping from the original R404A centralized system, the modified system is able to utilize a much larger proportion of the low GWP refrigerant R471A in the second circuit to achieve the same level of cooling in each evaporator and operate with a pressure drop low enough to allow effective operation of the heat transfer circuits.

[0123] [Table 10]

[0124] As can be seen from Table E1 above, the steam return pressure at node 10, which corresponds to the R471A inlet to the intercircuit heat exchanger, is 160.8 kPa. Since the condenser operates at 160 kPa, the pressure at the condenser inlet ensures proper and continued operation of the second circuit using the existing piping network.

[0125] Example 1B - Modifying the original system using R-404A and replacing R404A with refrigerant A2 (R476A) to create centralized refrigeration Example 1A was repeated, except that the R-404A refrigerant was replaced with a low GWP refrigerant, hereinafter referred to as Refrigerant A2, which contains the following components in the following relative amounts: Refrigerant A2 Ingredient weight% 1234ze(E)78 1336mzz(E)12 R134a 10 characteristics GWP (IPCC AR5) 133 Acceptable pressure drop performance similar to that of Example 1 is achieved.

[0126] Example 1C - Modifying the original system using R-404A and replacing R404A with refrigerant A3 to create centralized refrigeration Example 1A was repeated, except that the R-404A refrigerant was replaced with a low GWP refrigerant, hereinafter referred to as Refrigerant A3, containing the following components in the following relative amounts: Refrigerant A3 Ingredient weight% 1234ze(E)83.5 1224yd(Z)13 R134a 10 characteristics GWP (IPCC AR5) 131 Acceptable pressure drop performance similar to that of Example 1 is achieved.

[0127] Example 1C' - Modifying the original system using R-404A and replacing R404A with refrigerant A3' to create centralized refrigeration Example 1A was repeated, except that the R-404A refrigerant was replaced with a low GWP refrigerant, hereinafter referred to as Refrigerant A3', which contained the following components in the following relative amounts: Refrigerant A3' Ingredient weight% 1234ze(E)77 1224yd(Z)13 R134a 10 characteristics GWP (IPCC AR5) 131 Acceptable pressure drop performance similar to that of Example 1 is achieved. Ingredient weight% 1234ze(E)77 1224yd(Z)13 R134a 10 characteristics GWP (IPCC AR5) 131 Acceptable pressure drop performance similar to that of Example 1 is achieved.

[0128] Example 1D - Modifying the original system using R-404A, replacing R404A with refrigerant A1 (471A), and forming centralized refrigeration by adding a liquid ejector. Each of Examples 1A, 1B, 1C, and 1C' are repeated except that the length of piping between nodes i and j is 28 meters instead of 10 meters, and a liquid injector is added at the condenser inlet as shown in Figure 4 herein.

[0129] In this case, since the length of the steam return piping is increased, the pressure at node j will be lower than the design pressure at the inlet to the intercircuit heat exchanger, in the absence of other changes in the system of Example 1. To overcome this situation, a liquid ejector is added to the system, having an ejector liquid inlet and a motive fluid inlet controllably connected to the steam from node I. The following acceptable operating conditions, or similar acceptable conditions, are achieved:

[0130] [Table 11]

[0131] Comparative Example 6 - Operation of a centralized refrigeration system operating with R-404A A large capacity (i.e., 189 kW cooling capacity) direct expansion centralized supermarket medium temperature display case refrigeration system of the type disclosed in Figure 1 has R-404A as the existing refrigerant. The system has the following operating parameters, emissions parameters, and ambient conditions: Operating parameters Lifespan: 10 years Number of trading and non-trading hours: 14 / 10 respectively Installed cooling capacity: 189kW Execution conditions (Tevap, min, Tcond): Tevap=-8°C; Min Tcond=10℃ Air-cooled condenser = 45kW / Kw Air-cooled dry cooler=45kW / Kw Temperature difference between condensation temperature and ambient air -8° Kelvin emissions Leak rate = 15% per year CO2 emissions per kWh = 430 grams of CO2 / kWh (Reference: Coal approx. 1000 grams of CO2 / kWh, Nuclear approx. 50 grams of CO2 / kWh) Ambient conditions The climate conditions used in the model are as follows (e.g. London):

[0132] [Table 12] Cooling load distribution: 100% of total installed cooling capacity during the day 50% of total installed cooling capacity at night. Compressor and condenser fan performance: The COP of a compressor is rated based on the operating conditions (Tevap, Tcond, superheat). Condenser energy consumption = (heat needed to be rejected in the condenser) / (condenser energy efficiency). The energy consumption of the display cabinet is based on the energy consumption of fans, lighting and defrost heaters (if applicable); the defrost heaters operate twice per 24 hours. System operation as defined in this example defines the baseline conditions (100%) for power consumption and total CO2 emissions for comparison with the following examples.

[0133] Example 2A - Modification and operation of the modified central refrigeration system of Comparative Example 6 using R-1234ze(E) and A1 (R-471A) The system described in Comparative Example 6 is modified in accordance with the present invention. Referring generally to Figures 2A-2C, the liquid line 14 from the accumulator is disconnected to separate the liquid side of the evaporator from the liquid from the condenser 12, and the vapor line 15 is disconnected to separate the vapor side of the evaporator from the compressor to create a new first refrigeration circuit and a new second refrigeration circuit as described herein, including with reference generally to Figures 2A-2C. The existing R-404A refrigerant is removed in its entirety, R-1234ze(E) is used in the new first circuit, and R-471A is used in the new second circuit. A liquid pump 21 and an intercircuit heat exchanger are added as described herein and shown in Figure 3 to the new second system, and a releasable closure is added to the refrigerated display case, but the piping remains largely unchanged.

[0134] The new interconnected first and second refrigeration circuits are then operated to achieve the advantages set out in the table below.

[0135] [Table 13]

[0136] As can be seen from the table above, substantial improvements in CO2 emissions are achieved without any new electricity consumption, which is a significant and unexpected benefit.

[0137] Example 2B - Modification and operation of the modified central refrigeration system of Comparative Example 6 using R-1234ze (E) and A2 (R476A) Example 2A is repeated, except that refrigerant A2 as described above is used instead of refrigerant A1. The same desirable and unexpected results are achieved.

[0138] Modification and operation of the modified central refrigeration system of Comparative Example 6 using Example 2C-R-1234ze(E) and A3 Example 2A is repeated, except that refrigerant A3 as described above is used instead of refrigerant A1. The same desirable and unexpected results are achieved.

[0139] Modification and operation of the modified centralized refrigeration system of Comparative Example 6 using Example 2C'-R-1234ze(E) and A3' Example 2A is repeated, except that refrigerant A3 as described above is used instead of refrigerant A1. The same desirable and unexpected results are achieved.

[0140] Modification and operation of the modified centralized refrigeration system of Comparative Example 6 using Example 2D-R-454C and A1 Example 2A is repeated, except that the refrigerant R454C is used instead of R1234ze(E), and the same desirable and unexpected results are achieved.

[0141] Example 2E - Modification and operation of the modified central refrigeration system of Comparative Example 6 using R-455A and A3 Example 2A is repeated, except that refrigerant R455A is used instead of R1234ze(E), and the same desirable and unexpected results are achieved.

[0142] Example 3A - Modification and operation of the modified central refrigeration system of Comparative Example 6 using R-1234ze(E) and A1 (R-471A) and a water-cooled condenser Example 2A is repeated, except that a water-cooled condenser is used instead of the air-cooled condenser, and the same desirable and unexpected results are achieved.

[0143] Example 3B - Modification and operation of the modified central refrigeration system of Comparative Example 6 using R-1234ze(E) and A2 (R476A) and a water-cooled condenser Example 2B is repeated, except that a water-cooled condenser is used instead of the air-cooled condenser, and the same desirable and unexpected results are achieved.

[0144] Modification and operation of the modified central refrigeration system of Example 3C-R-1234ze(E) and A3 and Comparative Example 6 using a water-cooled condenser Example 2C is repeated, except that a water-cooled condenser is used instead of the air-cooled condenser, and the same desirable and unexpected results are achieved.

[0145] Modification and operation of the modified central refrigeration system of Example 3C'-R-1234ze(E) and A3' and Comparative Example 6 using a water-cooled condenser Example 2C' is repeated, except that a water-cooled condenser is used instead of an air-cooled condenser, and the same desirable and unexpected results are achieved.

[0146] Comparative Example 7 - Modification and operation of a modified centralized LT and MT refrigeration system using R-404A and substituting R-1234ze(E) and A1 (R471A) A large capacity direct expansion centralized supermarket medium temperature display case refrigeration system of the type shown in Figure 1 and described in Comparative Example 6 is installed in parallel with a low temperature refrigeration system operating with R455A refrigerant. The MT system has the same operating parameters, emissions parameters, and ambient conditions as those disclosed in Comparative Example 6, and the low temperature system operates under the following conditions: Operating parameters Capacity: 30kW Tevap = -32°C (R-455a or CO 2 using ); Temperature difference between condensation temperature and ambient air -8° Kelvin System operation as defined in this example defines the baseline conditions (100%) for power consumption and total CO2 emissions for comparison with Example 4 below.

[0147] Example 4A - Modification and operation of the modified central refrigeration system of Comparative Example 7 using R-1234ze(E) and A1 (R-471A) The MT system of Comparative Example 7 was modified and interconnected as described in Example 2A above, and then operated in parallel with the LT system, as shown in FIG.

[0148] The MT system has the same operating parameters, exhaust parameters, and ambient conditions as disclosed in Comparative Example 6, and the cooler system operates under the conditions specified in Comparative Example 7. The new first and second refrigeration circuits are then operated to achieve the benefits set forth in the table below.

[0149] [Table 14]

[0150] As can be seen from the table above, substantial improvements in CO2 emissions are achieved while at the same time reducing electricity consumption by approximately 3% - a significant and unexpected benefit.

[0151] Example 4B - Modification and operation of the modified central refrigeration system of Comparative Example 7 using R-455A and A1 (R-471A) Example 4A is repeated, except that R-455A is used instead of R-1234ze(E). The results are shown in the table below:

[0152] [Table 15]

[0153] Example 4C - Modification and operation of the modified central refrigeration system of Comparative Example 7 using R-454C and A1 (R-471A) Example 4A is repeated, except that R-454C is used instead of R-1234ze(E). The results are shown in the table below:

[0154] [Table 16]

[0155] Example 4D - Modification and operation of the modified central refrigeration system of Comparative Example 7 using R-290 and A1 (R-471A) Example 4A is repeated, except that R-290 is used instead of R-1234ze(E). The results are shown in the table below:

[0156] [Table 17]

Claims

1. 1. A method for forming an improved centralized refrigeration system, comprising: (a) providing an existing refrigeration circuit comprising: (i) an existing refrigerant having a GWP greater than 1200; (ii) a plurality of evaporators located within or near a refrigerated space containing consumer accessible products; and (ii) at least one compressor or rack of compressors and at least one condenser located away from said consumer accessible area, wherein the existing refrigerant liquid from said condenser is fluidly connected to said evaporator via a conduit and wherein existing refrigerant vapor from said evaporator is returned to the suction side of the compressor or compressor rack via a conduit; (b) severing a fluid connection between the existing liquid refrigerant from the condenser and at least one of the evaporators, preferably substantially all of the evaporators; (c) disconnecting a fluid connection between the existing refrigerant vapor from the at least one of the evaporators in step (b) and the suction of the compressor or compressor rack; (d) establishing a new first refrigeration circuit comprising the compressor or compressor rack and the condenser, wherein the existing refrigerant remains in the first refrigeration circuit or is removed and replaced; (e) (i) removing the existing refrigerant from at least a portion of the evaporator and conduit disconnected in steps (b) and (c); and (ii) replacing the removed existing refrigerant with a second refrigerant comprising: (1) at least about 50% by weight R1234ze(E); (2) greater than 0% to about 10% HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more thereof; and (3) about 10% to about 20% by weight HFO-1336mzz(E), HFO-1224yd(Z), and combinations thereof, wherein the second refrigerant (i) has an Occupational Exposure Limit (OEL) greater than 400; and (ii) is at least about 10% by weight of an ASHRAE refrigerant having an OEL greater than 400. establishing a new second refrigeration circuit comprising said at least one of the evaporators disconnected in steps (b) and (c), preferably all of said evaporators, by steps including: (i) replacing said at least one of the evaporators disconnected in steps (b) and (c), with a new evaporator classified as Class A1 according to Standard 34 and (iii) having a GWP of about 150 or less; (f) thermally interconnecting the fresh first refrigeration circuit and the fresh second refrigeration circuit with an inter-circuit heat exchanger, wherein at least a portion of the refrigerant in the first circuit is evaporated by absorbing heat from a second circuit refrigerant vapor and at least a portion of the second refrigerant vapor is condensed by transferring heat to a refrigerant liquid in the first circuit.

2. 2. The method of claim 1, wherein the second refrigerant has a gradient of 3° K or less.

3. 2. The method of claim 1, wherein the second refrigerant has a normal boiling point of -20°C to -12°C.

4. 2. The method of claim 1, wherein the second refrigerant comprises R741A.

5. 2. The method of claim 1, wherein the second refrigerant comprises R476A.

6. 10. The method of claim 1, wherein the second refrigerant comprises about 83.5% by weight HFO-1234ze(E), about 6.5% by weight HFO-1224yd(Z), and about 10% by weight HFC-134a.

7. 2. The method of claim 1, wherein the existing refrigerant is selected from R404A, R407, R448, R449, R454, R513, R455, and R22.

8. 2. The method of claim 1, wherein the existing refrigerant is R404A.

9. 3. The method of claim 2, wherein the existing refrigerant is R404A.

10. 4. The method of claim 3, wherein the existing refrigerant is R404A.

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