Method for forming a refrigerant system

Abstract

A method for improving a refrigeration system, comprising modifying the system and replacing an existing refrigerant with a replacement refrigerant comprising (1) at least about 50% by weight of R1234ze(E), (2) more than 0% to about 11% of HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more thereof, and (3) about 4% to about 20% by weight of HFO-1336mzz(E), HFO-1224yd(Z), and combinations thereof, wherein the second refrigerant has (i) an occupational exposure limit (OEL) of more than 400, (ii) is classified as Class A1 by ASHRAE Standard 34, and (iii) has a GWP of about 150 or less.

Description

Technical Field

[0001] The present invention relates to the improvement of heat transfer systems using high global warming refrigerants such as R404A, R448, R449, and R407. The present invention further extends to heat transfer systems obtainable by these methods, and heat transfer methods using such improved heat transfer systems.

Background Art

[0002] For industrial, commercial, and household use, mechanical refrigeration systems using refrigerant liquids, as well as related heat transfer devices such as heat pumps and air conditioners, are well known in the art. Chlorofluorocarbons (CFCs) were developed in the 1930s as refrigerants for such systems. However, since the 1980s, the impact of CFCs on the stratospheric ozone layer has received much attention. In 1987, many governments signed the Montreal Protocol for the protection of the global environment, which established a timetable for the phased reduction of CFC products. More environmentally acceptable materials containing hydrogen, namely hydrochlorofluorocarbons (HCFCs), replaced CFCs. One of the most commonly used hydrochlorofluorocarbon refrigerants was chlorodifluoromethane (HCFC-22). However, subsequent amendments to the Montreal Protocol accelerated the phased reduction of CFCs and also scheduled the phased reduction of HCFCs, including HCFC-22.

[0003] Creating new refrigerants that meet environmental requirements while gathering the necessary collection of advantageous performance characteristics has been a very large and complex challenge for the industry. Improving one category of performance often deteriorates another category of performance, and is deteriorated by individual commercial applications that often impose their own specific requirements on the refrigerant.

[0004] For example, heat transfer fluids such as R22, R404A, R407A, R448A, and R449A have been used in low or medium temperature applications in large-scale distributed direct expansion refrigeration systems for commercial use such as supermarkets. However, these refrigerants have an unacceptably high Global Warming Potential (GWP) according to IPCC AR5, namely, R404A (GWP = 3940), R22 (GWP = 1760), R407F (GWP = 1674), R448A (GWP = 1273), R449A (GWP = 1283). Since joints, hoses, and / or components of equipment within such systems are likely to eventually leak, there is a high possibility that refrigerants harmful to such an environment will leak into the atmosphere. Moreover, long pipelines contain more piping joints, valves, etc. that can potentially leak, so in the event of a leak, the longer the pipeline, the greater the amount of high-GWP refrigerant lost to the atmosphere.

[0005] Efforts to address the environmental defect problems of such distributed refrigeration systems present significant engineering challenges, in part due to the high costs associated with the large-scale replacement of such expensive and large systems. Moreover, conventional rooftop or mechanical room condenser / compressor systems provide a high level of efficiency and capacity, and any effort to modify these systems to be more environmentally attractive should desirably maintain this efficiency and capacity.

[0006] Efforts to address the environmental defect problems of such distributed refrigeration systems present significant engineering challenges, in part due to the high costs associated with the large-scale replacement of such expensive and large systems. Moreover, conventional rooftop or mechanical room condenser / compressor systems provide a high level of efficiency and capacity, and any effort to modify these systems to be more environmentally attractive should desirably maintain this efficiency and capacity.

[0007] In connection with efforts to convert conventional decentralized refrigeration systems into more environmentally friendly ones while maintaining efficiency and capacity, several thermodynamics and fluid flow challenges arise. For example, the Applicants have come to recognize that identifying environmentally friendly refrigerants (e.g., having a GWP of about 150 or less as measured by AR5) that can simply be used in existing decentralized refrigeration systems in place of existing high-GWP refrigerants is very difficult, if not impossible. Previously disclosed alternatives to R-22 have been studied and shown to result in a decrease in cooling capacity and an increase in power requirements, and thus a significant overall degradation in performance. (See WO 2020 / 223196 (A1)). This indicates the difficulty in developing a practicable solution to this problem.

[0008] In addition, using a nonflammable composition is generally considered to be either important or essential in many applications, particularly those involving many decentralized refrigeration systems. As used herein, the term "nonflammable" means a compound or composition that is measured to be nonflammable when measured in accordance with ASTM standard E-681-2009 Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases) under the conditions described in Appendix B1 of ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants, which is incorporated herein by reference. Unfortunately, many HFCs that may be desirable as a retrofit for existing decentralized refrigeration systems are not nonflammable as used herein. For example, fluoroalkane difluoroethane (HFC-152a) and fluoroalkene 1,1,1-trifluoropropene (HFO-1243zf) are each flammable and thus not practicable for use in many applications.

[0009] Regarding utilization efficiency, it is important to note that the loss of the thermodynamic performance or energy efficiency of the refrigerant can have secondary environmental impacts as an increase in the use of fossil fuels is brought about as a result of the increased demand for electrical energy.

[0010] This application describes inventions that meet these and other needs. This application describes a method for improving a heat transfer system, particularly a decentralized system, that allows a person skilled in the art to replace the refrigerant with a refrigerant having a lower GWP while maintaining an acceptable thermodynamic performance (particularly the ability to operate) and making only minor changes to the system infrastructure. Minimizing changes to the system infrastructure is particularly attractive as it minimizes the downtime of the equipment and the expenditure of financial capital costs associated with this method.

Summary of the Invention

[0011] The applicants have found that the above needs and other needs can be met by a method for improving a heat transfer system, the heat transfer system comprising (i) an existing refrigerant having a GWP greater than 150, and (ii) an existing refrigeration circuit comprising, in the order of the refrigerant flow, at least one evaporator, at least one compressor, at least one condenser, and at least one expansion device, located within or near a refrigerated space containing products available to a consumer, The method comprises (a) installing a subcooling refrigeration circuit comprising a subcooled refrigerant and, in the order of the refrigerant flow, a compressor, a heat exchanger for releasing heat from the subcooled refrigeration circuit, an expansion device, and a subcooling heat exchanger, a. the subcooling heat exchanger thermally connects the subcooling refrigeration circuit and the existing refrigeration circuit between the at least one condenser and the at least one expansion device (e.g., expansion valve) of the existing refrigerant circuit, b. the subcooling heat exchanger is configured to transfer heat from the existing refrigerant circuit to the subcooling circuit, (b) replacing the existing refrigerant with a replacement refrigerant comprising: (1) at least about 50% by weight of R1234ze(E); (2) more than 0% to about 11% of HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more thereof; and (3) from about 4% to about 20% by weight of HFO-1336mzz(E), HFO-1224yd(Z), and combinations thereof, wherein the replacement refrigerant has (i) an Occupational Exposure Limit (OEL) of greater than 400, (ii) is classified as Class A1 by ASHRAE Standard 34, and (iii) has a GWP of about 150 or less.

[0012] As will be appreciated by those skilled in the art, methods for improving heat transfer systems require minimal changes to existing equipment. Most of the wiring / conduit / tubing need not be changed to implement the method and, in most cases, simply remains in place, as do the evaporator, condenser, compressor, etc. Instead, the existing circuitry is modified by installing a subcooling heat exchanger that allows the subcooling refrigeration circuit to further cool the replacement refrigerant on its way to the expansion device / valve and the evaporator. This change significantly increases the capacity of the system and allows for the use of low-GWP refrigerants while maintaining attractive thermodynamic performance. The nature of the subcooled refrigerant is not particularly limited, providing the additional advantage to those skilled in the art that the subcooled refrigerant can be flexibly selected to meet the specific requirements of its own system.

[0013] The present invention also includes a heat transfer system obtainable by the methods described above and herein. The present invention (a) a first (core) refrigeration circuit comprising a. in the order of refrigerant flow, a condenser, an optional receiver, a subcooling heat exchanger, at least one expansion device (e.g., an expansion valve), at least one evaporator located within or near a refrigerated space containing a product available to a consumer, and at least one compressor; b. The core refrigerant within the first (core) refrigeration circuit, wherein the core refrigerant comprises: (1) at least about 50% by weight of R1234ze(E); (2) more than 0% to about 11% of HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more thereof; and (3) about 4% by weight to about 20% by weight of HFO-1336mzz(E), HFO-1224yd(Z), and combinations thereof, and the core refrigerant has: (i) an occupational exposure limit (OEL) of greater than 400; (ii) is classified as class A1 according to ASHRAE Standard 34; and (iii) has a GWP of about 150 or less, and a first (core) refrigeration circuit comprising the core refrigerant. (b) A subcooling refrigeration circuit, a. In the order of refrigerant flow: a compressor, a heat exchanger for discharging heat from the subcooling refrigeration circuit, an expansion device (e.g., an expansion valve), and a subcooling heat exchanger of the first refrigeration circuit, wherein the subcooling heat exchanger is configured to transfer heat from between the at least one condenser and the at least one expansion device (e.g., an expansion valve) of the first (core) refrigerant circuit to the subcooling refrigeration circuit, the compressor, the heat exchanger, the expansion device, and the subcooling heat exchanger; b. A subcooling refrigerant within the subcooling refrigeration circuit, and a subcooling refrigeration circuit comprising the same. A heat transfer system is included.

[0014] It will be apparent to those skilled in the art that the heat transfer system can be obtained by a method for improving the above and below heat transfer systems. Thus, the first / core refrigeration circuit of the heat transfer system corresponds to an existing refrigeration circuit of a method for improving the heat transfer system. Accordingly, all disclosures regarding the existing refrigeration circuit in this patent application can be clearly applied, individually or collectively, to the first / core refrigeration circuit of the refrigeration system described above and other parts of this patent application.

[0015] The present invention also extends to a heat transfer method using the above and below heat transfer systems. The heat transfer method is particularly useful when attempting to provide refrigeration, as will be described in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0017] Definition For the purposes of the present invention, the term "about" in relation to an amount expressed in weight percent for an amount exceeding 2% means that the amount of the component can vary by an amount of ±2 weight percent.

[0018] For the purposes of the present invention, the term "about" in relation to a temperature in degrees Celsius (°C) means that the specified temperature can vary by an amount of + / −5°C.

[0019] For the purposes of the present invention, the term "about" in relation to a ratio of power usage means that the stated ratio can vary by up to 1%.

[0020] For the purposes of the present invention, the term "substantial portion" in relation to the removal of existing refrigerant from a heat transfer system means removing at least about 50% of the existing refrigerant contained in the system.

[0021] The term "capacity" is the amount of cooling (BTU / hr or kW) provided by the refrigerant in a refrigeration system. This is determined experimentally by multiplying the change in enthalpy of the refrigerant in BTU / lb or kJ / kg as it passes through the evaporator by the mass flow rate of the refrigerant. Enthalpy can be determined from measurements of the pressure and temperature of the refrigerant. The capacity of a refrigeration system is related to the ability to maintain a cooled area at a specific temperature. The capacity of a refrigerant represents the amount of cooling or heating provided by the refrigerant and provides a measure of the ability of a compressor to pump heat for a given volume flow rate of the refrigerant. In other words, considering a specific compressor, a refrigerant with a higher capacity will supply more cooling or heating power.

[0022] The term "coefficient of performance" (hereinafter "COP") is a widely accepted measure of refrigerant performance that is particularly useful for representing the relative thermodynamic efficiency of a refrigerant in a specific heating or cooling cycle involving evaporation or condensation of the refrigerant. In refrigeration engineering, this term represents the ratio of useful refrigeration or cooling capacity to the energy applied by the compressor during compression of the vapor, and thus represents the ability of a given compressor to pump heat for a given volume flow rate of a heat transfer fluid such as a refrigerant. In other words, considering a specific compressor, a refrigerant with a higher COP will supply more cooling or heating power. One means for estimating the COP of a refrigerant under specific operating conditions is from the thermodynamic properties of the refrigerant using standard refrigeration cycle analysis techniques (see, for example, R.C. Downing, FLUOROCARBON REFRIGERANTS HANDBOOK, Chapter 3, Prentice-Hall, 1988, which is incorporated herein by reference in its entirety).

[0023] The term "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 operating the thermal protection aspect of the system designed to protect the compressor components, and avoids the use of expensive control devices such as liquid injection to lower the discharge temperature.

[0024] As used herein, the term "central refrigeration system" means a refrigeration system that includes one or more centrally located compressors or compressor racks, one or more centrally located condensers, and a plurality of evaporators that are located remotely from the central compressor or compressor rack and that receive liquid refrigerant from the centrally located condenser.

[0025] In contrast to a central system, the term "distributed refrigeration system" means a system that includes several compressors or compressor racks that are distributed adjacent to or near locations (e.g., display cases) that require refrigeration.

[0026] As used herein, "direct expansion" means a heat transfer system that utilizes an evaporator in which liquid refrigerant enters the evaporator, flows through a coil (preferably a tubular coil), and evaporates as heat is absorbed from air circulating within a display case, uses a thermostatic expansion valve at the inlet of the evaporator, and is controlled to supply sufficient refrigerant such that substantially all of the refrigerant evaporates at the outlet of the evaporator and optionally has a predetermined amount of superheat at the outlet.

[0027] The term "Global Warming Potential (GWP)" was developed to enable comparison of the effects of different gases on global warming and, as used herein, refers to the GWP determined by AR5 as described above. Specifically, it is a measure of how much energy a one-ton emission of a gas absorbs relative to a one-ton emission of carbon dioxide over a given period. The higher the GWP, the more a given gas will warm the planet over that period compared to CO2. The period commonly used for GWP is 100 years. GWP provides a common metric that enables analysts to sum emission estimates for 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.

[0028] The term "Occupational Exposure Limit (OEL)" is determined in accordance with ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants.

[0029] As used herein, the phrase "acceptable toxicity" 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 (each standard as it exists as of the filing date of this application). Substances that are nonflammable and of low toxicity are classified as "A1" by ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants and are described in Appendix B1 of ASHRAE Standard 34-2016 (each standard as it exists as of the filing date of this application).

[0030] The term "mass flow rate" is the mass of refrigerant passing through a conduit per unit time.

[0031] As used herein, the term "replacement" means the use of the compositions of the present invention in a heat transfer system that is designed to be used with or is 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 to be used with R-410A, the refrigerant or heat transfer composition of the present invention is a replacement for R-410A in that system. Thus, it will be understood that the term "replacement" includes the use of the refrigerants and heat transfer compositions of the present invention in both new and existing systems that are designed to be used with R-410A, are commonly used with R-410A, or are suitable for use with R-410A.

[0032] The term "glide" is applied to azeotropic refrigerant mixtures having various temperatures during a phase change process in an evaporator or condenser at a 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.

[0033] The term "low-temperature refrigeration system" refers to a heat transfer system that operates at a condensation temperature of about 40°C to about 70°C and an evaporation temperature of about -45°C to -12°C (including this temperature).

[0034] The term "medium-temperature refrigeration system" refers to a heat transfer system that operates at a condensation temperature of about 40°C to about 70°C and an evaporation temperature of -12°C to about 0°C.

[0035] As used herein, the term "supermarket refrigeration" means a commercial refrigeration system used to maintain chilled or frozen foods in both product display cases and storage refrigerators.

[0036] As used herein, the term "subcooling" refers to cooling the replacement (or core) refrigerant to a temperature significantly below the temperature at the outlet of the condenser. Referring to FIGS. 3 and 4, subcooling means the difference between the condensation temperature and the liquid temperature at the inlet of the expansion device / valve.

[0037] The term "standard boiling point" refers to the boiling point of a single component measured at 1 atmosphere and the initial boiling point of a blend of components at 1 atmosphere.

[0038] The term "R22" means chlorodifluoromethane.

[0039] As used herein, the terms "HFC32" and "R32" each mean difluoromethane.

[0040] The terms "HFC-125" and "R125" mean pentafluoroethane.

[0041] The terms "HFC-134a" and "R134a" mean 1,1,1,2,-tetrafluoroethane.

[0042] The terms "HFC-134" and "R134" mean 1,1,2,2-tetrafluoroethane.

[0043] The term "R143a" means 1,1,1-trifluoroethane.

[0044] The term "R290" means propane.

[0045] The term "R404A" means a combination of approximately 44% by weight of R-125, approximately 52% by weight of R143a, and approximately 4% by weight of R-134a.

[0046] The term "R407A" means a combination of approximately 20% by weight of R-32, approximately 40% by weight of R125, and approximately 40% by weight of R-134a.

[0047] The term "R407B" means a combination of approximately 10% by weight of R-32, approximately 70% by weight of R125, and approximately 20% by weight of R-134a.

[0048] The term "R407C" means a combination of approximately 23% by weight of R-32, approximately 25% by weight of R125, and approximately 52% by weight of R-134a.

[0049] The term "R407D" means a combination of approximately 15% by weight of R-32, approximately 15% by weight of R125, and approximately 70% by weight of R-134a.

[0050] The term "R407F" means a combination of approximately 40% by weight of R-32, approximately 30% by weight of R125, and approximately 30% by weight of R-134a.

[0051] The term "R407" means any one of R407A, R407B, R407C, R407D, and R407F.

[0052] The term "R448A" means a combination of approximately 26% by weight of R-32, approximately 26% by weight of R125, and approximately 21% by weight of R-134a.

[0053] The term "R448A" means a combination of approximately 26 wt% R-32, approximately 26 wt% R125, and approximately 21 wt% R-134a.

[0054] The term "R448" means a refrigerant designated as R448 having any literal notation including R448A.

[0055] The term "R449A" means a combination of approximately 24.3 wt% R-32, approximately 24.7 wt% R125, and approximately 25.7 wt% R-134a.

[0056] The term "R449" means a refrigerant designated as R449 having any literal notation including R449A.

[0057] The term "R454B" means a combination of approximately 68.9 wt% R-32 and approximately 31.1 wt% R1234yf.

[0058] The term "R454" means a refrigerant designated as R454 having any literal notation including R454B.

[0059] The term "R513A" means a combination of approximately 44 wt% R-134a and approximately 56 wt% R1234yf.

[0060] The term "R449" means a refrigerant designated as R449 having any literal notation including R449A.

[0061] As used herein, the terms "HFO1234yf" and "R1234yf" each mean 2,3,3,3-tetrafluoropropene.

[0062] As used herein, the terms "HFO1234ze(E)", "R1234ze(E)", and "1234ze(E)" each mean trans-1,3,3,3-tetrafluoropropene. Unless otherwise specified, "HFO1234ze", "R1234ze", and "1234ze" mean trans-1,3,3,3-tetrafluoropropene.

[0063] References in this specification to groups of defined terms include all such defined terms and all such terms with suffix designations.

[0064] Systems and Methods The present invention incorporates a method for improving existing heat transfer systems.

[0065] Prior to the improvement, the existing heat transfer system comprises (i) an existing refrigerant having a GWP greater than 150 (e.g., greater than 500, or greater than 1200), and (ii) in flow order, an existing refrigeration circuit comprising at least one evaporator, at least one compressor (or compressor rack), at least one condenser, and at least one expansion device (e.g., at least one expansion valve) located within or near a refrigerated space containing products available to a consumer.

[0066] The existing heat transfer system can be further understood by referring to FIGS. 1 and 2, which are representative examples of existing distributed refrigeration systems of the type improved in accordance with the present invention. As those skilled in the art will recognize, these types of systems operate by circulating refrigerant around a vapor compression refrigeration circuit. At least one evaporator (4, 4a) is located within or near a refrigerated space, such as a space containing consumer products available to consumers. The evaporator functions to transfer heat from the refrigerated space to the refrigerant, which generally results in a change from liquid / vapor to vapor. The vapor is sent to at least one compressor or compressor rack (5) that compresses the refrigerant to a higher temperature. The compressed refrigerant vapor is sent to a condenser (1), where heat is released from the refrigerant while the refrigerant is converted to a liquid. A receiver (3) is optionally located downstream of the condenser and provides a reservoir of liquid refrigerant for supply to the expansion device 3. Before returning to at least one evaporator (4, 4a), the refrigerant rapidly evaporates as it passes through at least one expansion device (3, 3a) (e.g., at least one expansion valve) to produce a cooled gas / liquid that is desirable for receiving heat in at least one evaporator. If multiple evaporators and expansion devices or valves (3a) are present, each evaporator / expansion valve pair can service different refrigerated cabinets that optionally operate at different temperatures in a distributed system, such as a commercial store like a grocery store (e.g., a supermarket).

[0067] It is preferred that at least one evaporator (4, 4a) is configured to operate as a medium-temperature evaporator. Optionally, the evaporator is configured to operate at a temperature between -12°C and 0°C.

[0068] Although schematically shown in FIGS. 1 and 2, in reality, each of these pipe networks generally represents an extensive and long series of conduits for transporting liquid refrigerant from the accumulator receiver (3), and the accumulator receiver (3) is often located at a place away from the compressor or compressor rack (5) and the condenser (1). Therefore, the pipe network is large and often covers a distance, for example, from the roof of a supermarket or a machine room to spread over the floor of the supermarket to reach a number of display cases arranged in the supermarket.

[0069] Although the compressor or compressor rack in FIGS. 1 and 2 is shown as having two compressors, in reality, it will also be recognized by those skilled in the art that the compressor / compressor rack can be equipped with from one compressor to a maximum of about five compressors depending on individual applications. The existing refrigerant system provided according to the present invention can represent a compressor operating capacity of about 3 kW to about 500 kW. Regarding the type of compressor, it is contemplated that all types of compressors can be present in such a system, but in many of such systems, the compressors used are selected from screw compressors, scroll compressors, reciprocating compressors, centrifugal compressors, twin screw compressors, and combinations thereof.

[0070] Existing refrigerants in existing refrigeration circuits generally have a GWP (measured in accordance with AR5) of greater than 150, greater than 500, or greater than 1200. Preferred existing refrigerants include R404A, R407 (such as each of R407A, R407B, R407C, R407D), R448 (all letter notations), R449 (all letter notations), R454, R513, R22, and 134a, more preferably R404A, R407A, R407B, R407C, R407D, R448 (all letter notations), and R449 (all letter notations), and most preferably R404A.

[0071] The present invention improves a system of the type disclosed in FIGS. 1 and 2 to achieve at least an acceptable performance of the overall system, preferably while improving the overall heat transfer performance, without degrading the safety aspect of the system in terms of the toxicity and flammability of the refrigerant exposed to the area open to the public, including improving the environmental compatibility of the system.

[0072] This improvement method generally includes two main steps, namely, the step of inserting a subcooling refrigeration circuit connected via a subcooling heat exchanger, and the step of replacing the existing refrigerant with a replacement refrigerant (for example, by removing substantially all of the existing refrigerant before adding the replacement refrigerant to the system). Those skilled in the art will understand that these steps can be performed in any order subject to the practical limitations of the system to be improved. For example, if it is practical to isolate the existing refrigerant from areas of the existing system that are mechanically modified or replaced, it is possible to replace the existing refrigerant after installing the subcooling refrigeration circuit without risking leakage of the existing refrigerant. As is generally the case, if it is not practical to isolate the existing refrigerant in this way, it is more practical to remove the existing refrigerant, install the subcooling refrigeration circuit and the subcooling heat exchanger, and then add the replacement refrigerant to the system. By doing so, the risk of leakage of the existing refrigerant is reduced. These method steps are described below in the order corresponding to the sequence of steps shown in claim 1, but those skilled in the art will understand that the present invention is not limited to this order of events.

[0073] The subcooling heat exchanger is installed in fluid connection between the condenser of the existing refrigeration circuit and at least one expansion device (for example, at least one expansion valve). If a receiver (2) is present, the subcooling heat exchanger is generally installed in fluid connection between the receiver and at least one expansion device. This operation generally includes removing part or all of this fluid connection by replacing the entire pipe or by removing part of this pipe.

[0074] The properties of the subcooling heat exchanger (6) are not particularly limited, and it is within the ability of those skilled in the art to select an appropriate design for their systems. However, the heat exchanger is configured to thermally couple the existing circuit and the installed subcooling circuit by enabling heat transfer from the existing heat transfer circuit to the subcooling refrigeration circuit. In this way, the subcooling circuit facilitates further cooling of the refrigerant in the existing refrigeration circuit before the refrigerant reaches the expansion device or valve (3, 3a).

[0075] As described above, the subcooling heat exchanger forms an important part of the subcooling refrigeration circuit. This circuit can take the form shown in FIGS. 3 and 4, which illustrate a heat transfer system obtained, for example, by applying the method of claim 1 to the heat transfer systems of FIGS. 1 and 2. In FIGS. 3 and 4, the remainder of the existing refrigeration circuit (101) is shown to be thermally coupled to the subcooling refrigeration circuit (102) via the subcooling heat exchanger (6). The subcooling heat exchanger is configured to cool the refrigerant passing downstream from the condenser (1) through the expansion device / valve (3, 3a) and an optional receiver (2). As shown, the subcooling circuit further includes a compressor (7), a heat exchanger (8) for releasing heat from the subcooled refrigerant, and an expansion valve (9). The heat exchanger (8) can release heat in a variety of different ways, providing further advantageous versatility to the present invention. For example, the heat exchanger (8) can release heat to the surroundings, such as the air outside a building, or it can release heat to water. The water heated thereby can itself be used for heating purposes, such as domestic heating or commercial heating.

[0076] The properties of the subcooled refrigerant are not particularly limited. This flexibility provides an additional advantage of the present invention as it offers those skilled in the art the freedom to select based on their preferences and the requirements of the specific system being improved. The subcooled refrigerant can preferably be selected from the group consisting of R455A, R454C, propane, R1234yf, R152a, R1234ze, R471A, R476A, and B6. These refrigerants have been found to be particularly effective in subcooled refrigeration circuits. For example, adding a subcooled refrigeration circuit using these refrigerants has been found to increase the coefficient of performance by at least 30 wt% compared to an existing refrigeration circuit (without subcooling) using R404A as the refrigerant. More preferably, the subcooled refrigerant is selected from R455A, R454C, R1234yf, R1234ze, and R471A, and most preferably from R455A and R454C. The subcooled refrigeration circuit including the subcooling heat exchanger is preferably located outside the area generally exposed to the public. For example, when the heat transfer system is used in a commercial environment such as a supermarket, the subcooled refrigeration circuit is generally located outside the area exposed to customers. Positioning the subcooled refrigeration circuit in this way is preferred as it enhances safety when using a flammable subcooled refrigerant.

[0077] The conditions of the subcooled refrigerant can vary widely, but the subcooling temperature is in the range of 10 to 70 °C, preferably 30 to 50 °C, for example, about 40 °C.

[0078] Importantly, the method of the present invention involves using a replacement refrigerant comprising: (1) at least about 50% by weight of R1234ze(E); (2) greater than 0% to about 11% of HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more thereof; and (3) about 4% to about 20% by weight of HFO-1336mzz(E), HFO-1224yd(Z), and combinations thereof, wherein the replacement refrigerant has: (i) an occupational exposure limit (OEL) greater than 400; (ii) is classified as Class A1 according to ASHRAE Standard 34; and (iii) has a GWP of about 150 or less. Table A below identifies two replacement refrigerant blends that meet these criteria and provide significant, unexpected advantages in accordance with the present invention, and it is understood that all amounts in the table are considered to be preceded by "about".

[0079] [Table 1]

[0080] In a preferred embodiment, the replacement refrigerant is selected from within the ranges of the components specified in Table B below, and it is understood that all amounts in the table are considered to be preceded by "about".

[0081] [Table 2]

[0082] Those skilled in the art will understand that B4 is a narrow version of B1, B5 is a narrow version of B2, and B6 is a narrow version of B6.

[0083] In a preferred embodiment, the replacement refrigerant has a normal boiling point within the ranges specified in Table C below, and it is understood that all amounts in the table are considered to be preceded by "about".

[0084] [Table 3]

[0085] In a preferred embodiment, the replacement refrigerant has a gradient within the range specified in Table D below, and it is understood that all amounts in the table are considered to be preceded by "about".

[0086] [Table 4]

[0087] An advantage of the present invention is that the method of improving an existing heat transfer system requires little or no change to most of the equipment forming the existing heat transfer system. Except for the conduits that are partially or completely removed to enable the installation of the subcooling heat exchanger, little or no change to the equipment in other locations is required. This is because equivalent or improved thermodynamic performance is achieved without significantly changing the operating conditions of the existing refrigeration circuit. Generally, the conduits / piping, condenser, expansion valve, compressor, and pressure seal of the system do not require modification to accommodate the present invention, and thus the time, complexity, and cost associated with improving the heat transfer system are reduced.

[0088] Also, by reducing the number of essential equipment changes, if selected by a person skilled in the art, it frees up budget and time for voluntary equipment changes to further enhance the system. For example, a person skilled in the art can choose to improve the performance of the system by increasing the insulation level in the space cooled by the evaporator, such as by adding a door to the refrigerated space by at least one evaporator, such as a refrigeration unit in a store / supermarket. Adding a door to a refrigeration unit in a store / supermarket is particularly useful when the existing refrigerant is R448A or R404A as it helps to achieve a close match in terms of capacity. Also, by replacing the expansion valves (3, 3a) to modify the physical properties of the replacement refrigerant before it enters the evaporator (4, 4a), the capacity can be increased when replacing R448A or R404A as the existing refrigerant.

[0089] As described above, the present invention also extends to heat transfer systems. These heat transfer systems can be obtained by the methods for improving the heat transfer systems described above, but are not limited to those manufactured in this way. The heat transfer system (a) A first (core) refrigeration circuit, a. A core refrigerant in the first (core) refrigeration circuit, the core refrigerant comprising: (1) at least about 50% by weight of R1234ze(E); (2) more than 0% to about 11% of HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more thereof; and (3) about 4% to about 20% by weight of HFO-1336mzz(E), HFO-1224yd(Z), and combinations thereof, wherein the core refrigerant has: (i) an occupational exposure limit (OEL) of more than 400; (ii) is classified as Class A1 according to ASHRAE Standard 34; and (iii) has a GWP of about 150 or less, the core refrigerant; b. In the order of the refrigerant flow, at least one evaporator, at least one compressor, at least one condenser, and at least one expansion device, located within or near a refrigerated space containing a product available to a consumer, a first (core) refrigeration circuit; (b) A subcooling refrigeration circuit, a. A subcooling refrigerant in the subcooling refrigeration circuit, b. In the order of the refrigerant flow, a compressor, an evaporator for releasing heat from the subcooling refrigeration refrigerant / circuit, an expansion device, a subcooling heat exchanger, and the subcooling refrigerant, wherein the subcooling heat exchanger is configured to transfer heat from between the at least one condenser and the at least one expansion device (e.g., an expansion valve) of the first (core) refrigerant circuit to the subcooling refrigeration circuit, a subcooling refrigeration circuit.

[0090] Preferred features of the method for improving a heat transfer system are clearly applicable to such a heat transfer system. For example, the preferred refrigerants and operating conditions described for the method for improving a heat transfer system are clearly applicable to the above-described heat transfer system, since they can be obtained by such a method.

[0091] The present invention also extends to a heat transfer method using a heat transfer system that can be obtained by a method of improving a heat transfer system. The advantage of the improved heat transfer system is that it can be used for various end - uses. A particularly preferred type of heat transfer system is a low - temperature or medium - temperature refrigeration system, preferably a medium - temperature refrigeration system. Preferred end - uses are refrigeration, stationary refrigeration, commercial stationary refrigeration, such as in food stores like food warehouses, low - temperature storage warehouses, and supermarkets.

[0092] Combination of refrigerants As will be understood by those skilled in the art, the present invention relates to methods and systems for utilizing different refrigerants for different purposes. Preferred combinations of refrigerants are shown in Tables E - G below. Those skilled in the art will understand the following. · The method of improving a refrigeration system relates to existing refrigerants, alternative refrigerants, and sub - cooled refrigerants. · The heat transfer systems that can be obtained from these methods have a core refrigerant (i.e., alternative refrigerant) and a sub - cooled refrigerant, and the heat transfer methods using these heat transfer systems have the same core and sub - cooled refrigerants. In other words, the "existing refrigerant" column in Table E can be ignored when considering the refrigerant combinations of these heat transfer systems and heat transfer methods.

[0093]

Table 5 - 1

[0094]

Table 5 - 2

[0095]

Table 5 - 3

[0096]

Table 6 - 1

[0097]

Table 6-2

[0098]

Table 6-3

[0099]

Table 7-1

[0100]

Table 7-2

[0101]

Table 7-3

[0102]

Table 7-4

[0103]

Table 7-5

[0104] One skilled in the art will also understand that it is advantageous to include a compressor lubricant in combination with a replacement / core refrigerant and / or a subcooled refrigerant. Useful compressor lubricants include polyol ester (POE), mineral oil, alkylbenzene (AB), polyvinyl ether (PVE), poly(alkylene glycol) (PAG), and poly(alpha-olefins) (PAO). Thus, one skilled in the art will understand that combinations of the features of Tables H and I are also advantageous.

[0105]

Table 8-1

[0106]

Table 8-2

[0107]

Table 8-3

[0108]

Table 8-4

[0109]

Table 8-5

[0110]

Table 8-6

[0111]

Table 8-7

[0112]

Table 8-8

[0113]

Table 8-9

[0114]

Table 9-1

[0115]

Table 9-2

[0116]

Table 9-3

[0117]

Table 9-4

[0118]

Table 9-5

[0119]

Table 9-6

[0120]

Table 9-7

[0121]

Table 9-8

[0122]

Table 9-9

[0123]

Table 9-10

[0124]

Table 9-11

[0125]

Table 9-12

[0126]

Table 9-13

[0127]

Table 9-14

Examples

[0128] The following examples are provided for the purpose of illustrating the present invention and are not intended to limit its scope.

[0129] When evaluating methods for improving a refrigeration system, such as replacing a refrigerant with a higher GWP with a refrigerant with a lower GWP, the following performance parameters are important: (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 loss ratio.

[0130] Comparative Example 1 - Refrigeration System Using R-404A as Refrigerant The refrigeration system of the type disclosed in FIG. 1 was equipped with R-404A as the existing refrigerant. The operating conditions of the system using R-404A as the refrigerant are as follows. Cooling capacity: 45.0 kW Isentropic efficiency: 0.65 Volumetric efficiency: 100% Condensing temperature: 40°C Superheat: 10°C Evaporating temperature: -10°C

[0131] This system operates well from the perspective of thermodynamic performance and heat transfer performance. However, since the entire system contains the high-GWP refrigerant R404A that circulates throughout the system, it is highly undesirable from the perspective of its environmental impact. The performance of this system is further summarized in the following Result Tables 1 and 2.

[0132] Comparative Example 2 - Refrigeration system using R-471A instead of R-404A Comparative Example 1 was repeated, except that the low-GWP refrigerant R-471A was used instead of R-404A. R-471A is a refrigerant composed of the following components in the following relative amounts.

[0133] [Table 10]

[0134] The performance of this system is further summarized in the following Result Tables 1 and 2.

[0135] [Table 11]

[0136] As can be seen from the results in the above Result Table 1, replacing R-417A with R-404A improves the system from the perspective of containing a low-GWP refrigerant but reduces the cooling capacity. The present invention solves this problem and other problems.

[0137] Example 1 - Improvement of a refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using R455A and replacing R404A with refrigerant A1 (R-471A) A The heat transfer system of Comparative Example 1 (including the existing refrigerant R404A contained therein) was used as a starting point for forming the improved heat transfer system shown in FIG. 3. Refrigerant R404A was removed from the refrigeration system, and a subcooling heat exchanger (6) was installed between the receiver (2) and the expansion valve (3). The subcooling heat exchanger was configured to exchange heat between the main refrigeration circuit and a dedicated mechanical subcooling system (DMSS) (102) that serves to cool the refrigerant flowing through the existing refrigerant circuit. The DMSS evaporation temperature was 0°C and the condensation temperature was 40°C. Other details of the DMSS are shown in Table 2 of the following results.

[0138] After modification, refrigerant R471A was used as the core circuit refrigerant and refrigerant R455A was used as the DMSS refrigerant. The performance of the improved refrigeration system is summarized in Table 2 of the following results.

[0139] Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using R455A, replacing R404A with refrigerant A1 (R-471A), and modifying the heat exchanger Example 1 was repeated except that the heat exchanger was modified to be compatible with the low-pressure fluid. The performance of the improved refrigeration system is summarized in Table 2 of the following results.

[0140] [Table 12]

[0141] As can be seen from Table 2 of the results, replacing the high-GWP refrigerant R404A with a low-GWP refrigerant such as R471A resulted in an unacceptable decrease in cooling capacity. However, this drawback can be surprisingly mitigated by installing a powerful subcooling system between the condenser and the evaporator. The cooling capacity increases from 39% of R404A to 57% of R404A without making other changes. By modifying the heat exchanger, this further increases to 70% of R404A.

[0142] These modifications to the system of Comparative Example 1 have a number of advantages. First, without sacrificing an unacceptable level of cooling capacity, the GWP of the refrigerant circulating in the main circuit can be significantly reduced. Second, the modifications to the main refrigeration circuit itself are relatively few and only require installing a heat exchanger between the condenser and the evaporator.

[0143] Improvement of a refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using R454C and replacing R404A with refrigerant A1 (R - 471A) Example 1 was repeated, but refrigerant R454C was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in the following Result Table 3.

[0144] Improvement of a refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using R454C, replacing R404A with refrigerant A1 (R - 471A), and modifying the heat exchanger Example 2 was repeated, but refrigerant R454C was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in the following Result Table 3.

[0145]

Table 13

[0146] Similar to Examples 1 and 2, Examples 3 and 4 show that good cooling capacity can be achieved using the present invention. Examples 3 and 4 further show that various refrigerants can be used in the DMSS circuit.

[0147] Improvement of a refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using propane and replacing R404A with refrigerant A1 (R - 471A) Example 1 was repeated, but refrigerant propane was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in the following Result Table 4.

[0148] Example 6 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using propane, replacing R404A with refrigerant A1 (R - 471A), and modifying the heat exchanger Example 2 was repeated, but refrigerant propane was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in Table 4 of the following results.

[0149]

Table 14

[0150] Examples 5 and 6 show that good cooling capacity can be achieved using the present invention, further emphasizing the flexibility of the subcooled refrigerant.

[0151] Example 7 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using HFO - 1234yf and replacing R404A with refrigerant A1 (R - 471A) Example 1 was repeated, but refrigerant HFO - 1234yf was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in Table 4 of the following results.

[0152] Example 8 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using HFO - 1234yf, replacing R404A with refrigerant A1 (R - 471A), and modifying the heat exchanger Example 2 was repeated, but refrigerant HFO - 1234yf was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in Table 4 of the following results.

[0153]

Table 15

[0154] Examples 7 and 8 show that good cooling capacity can be achieved using the present invention, further emphasizing the flexibility of the subcooled refrigerant.

[0155] Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using R152a and replacing R404A with refrigerant A1 (R-471A) Example 1 was repeated, but refrigerant R152a was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in Table 5 of the following results.

[0156] Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using R152a, replacing R404A with refrigerant A1 (R-471A), and modifying the heat exchanger Example 2 was repeated, but refrigerant R152a was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in Table 5 of the following results.

[0157]

Table 16

[0158] Examples 9 and 10 show that good cooling capacity can be achieved using the present invention, further emphasizing the flexibility of the subcooled refrigerant.

[0159] Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using HFO-1234(E) and replacing R404A with refrigerant A1 (R-471A) Example 1 was repeated, but refrigerant HFO-1234(E) was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in Table 6 of the following results.

[0160] Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using HFO-1234(E), replacing R404A with refrigerant A1 (R-471A), and modifying the heat exchanger Example 2 was repeated, but refrigerant HFO-1234(E) was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in Table 6 of the following results.

[0161]

Table 17

[0162] Examples 11 and 12 show that the present invention can achieve good cooling capacity, further emphasizing the flexibility of the subcooled refrigerant.

[0163] Example 13 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using R471A and replacing R404A with refrigerant A1 (R - 471A) Example 1 was repeated, but refrigerant R471A was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in the following result Table 7.

[0164] Example 14 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) using R471A, replacing R404A with refrigerant A1 (R - 471A), and modifying the heat exchanger Example 2 was repeated, but refrigerant R471A was used in the DMSS circuit. The performance of the improved refrigeration system is summarized in the following result Table 7.

[0165]

Table 18

[0166] Examples 13 and 14 show that the present invention can achieve good cooling capacity, further emphasizing the flexibility of the subcooled refrigerant.

[0167] Example 15 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) and replacing R404A with R476A Examples 1 to 14 were repeated, but R476A was used instead of R404A. For a number of experiments within this example, similar favorable and unexpected results were achieved.

[0168] Example 16 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) and replacing R404A with refrigerant B6 Examples 1 to 14 were repeated, but refrigerant B6 was used instead of R404A. For a number of experiments within this example, similar favorable and unexpected results were achieved.

[0169] Example 17 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) and replacing R448 with R471A Examples 1 to 14 were repeated, but R471A was used instead of R448. For a number of experiments within this example, similar favorable and unexpected results were achieved.

[0170] Example 18 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) and replacing R448 with R476A Examples 1 to 14 were repeated, but R476A was used instead of R448. For a number of experiments within this example, similar favorable and unexpected results were achieved.

[0171] Example 19 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) and replacing R448 with refrigerant B6 Examples 1 to 14 were repeated, but refrigerant B6 was used instead of R448. For a number of experiments within this example, similar favorable and unexpected results were achieved.

[0172] Example 20 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) and replacing R134a with R471A Examples 1 to 14 were repeated, but R471A was used instead of R134a. For a number of experiments within this example, similar favorable and unexpected results were achieved.

[0173] Example 21 - Improvement of the refrigeration system by installing a dedicated mechanical subcooling system (DMSS) and replacing R134a with R476A Examples 1 to 14 were repeated, but R476A was used instead of R134a. For a number of experiments within this example, similar favorable and unexpected results were achieved.

[0174] Example 22 - Improvement of a refrigeration system by installing a dedicated mechanical subcooling system (DMSS) and replacing R134a with refrigerant B6 Examples 1 to 14 were repeated, but refrigerant B6 was used instead of R134a. For a number of experiments within this example, similar favorable and unexpected results were achieved.

Claims

1. A method for improving a heat transfer system, the heat transfer system comprising (iii) an existing refrigerant having a GWP of greater than 150, and (iv) in the order of the refrigerant flow, an existing refrigeration circuit comprising at least one evaporator, at least one compressor, at least one condenser, and at least one expansion device, located within or near a refrigerated space containing products available to a consumer, The method comprising (a) a subcooling refrigeration circuit comprising, in the order of flow, a compressor, a heat exchanger for releasing heat from the subcooled refrigerant, an expansion device, and a subcooling heat exchanger, with subcooled refrigerant, a. the subcooling heat exchanger thermally connecting the subcooling refrigeration circuit and the existing refrigeration circuit between the at least one condenser and the at least one expansion device of the existing refrigeration circuit, b. installing a subcooling refrigeration circuit, wherein the subcooling heat exchanger is configured to transfer heat from the existing refrigeration circuit to the subcooling refrigeration circuit, (b) replacing the existing refrigerant with a replacement refrigerant comprising (1) at least about 50 wt% R1234ze(E), (2) greater than 0% to about 11% of HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more thereof, and (3) about 4 wt% to about 20 wt% of HFO-1336mzz(E), HFO-1224yd(Z), and combinations thereof, the replacement refrigerant having (i) an occupational exposure limit (OEL) greater than 400, (ii) being classified as class A1 by ASHRAE Standard 34, and (iii) having a GWP of about 150 or less.

2. The method of claim 1, wherein the replacement refrigerant is selected from R471A, R476A, and B6.

3. The method of claim 1, wherein the existing refrigerant is selected from R404A, R407, R448, R449, R454, R513, R22, and 134a.

4. The subcooled refrigerant is selected from R455A, R454C, propane, R1234yf, R152a, R1234ze, R471A, R476A, and B6, The method of claim 1, wherein the existing refrigerant is selected from R404A, R407, R448, R449, R454, R513, R22, and 134a.

5. The existing refrigerant is selected from R404A, R134a, and R448A. The replacement refrigerant is selected from R471A, R476A, and B6, The subcooled refrigerant is selected from R455A, R454C, R1234yf, and R1234ze, the method according to claim 1.

6. The replacement refrigerant is used with a lubricant selected from polyol ester (POE), mineral oil, alkylbenzene (AB), polyvinyl ether (PVE), and poly(alpha olefin) (PAO), the method according to claim 1.

7. The replacement refrigerant is used with a poly(alkylene glycol) (PAG) lubricant, the method according to claim 1.

8. The replacement refrigerant is used with a polyvinyl ether (PVE) lubricant, the method according to claim 1.

9. The subcooled refrigerant and the replacement refrigerant are used with a lubricant independently selected from polyol ester (POE), mineral oil, alkylbenzene (AB), polyvinyl ether (PVE), and poly(alpha olefin) (PAO), the method according to claim 1.

10. Step (b) comprises removing at least a part of the fluid connection between the at least one evaporator and the at least one expansion device of the existing refrigerant circuit, providing a replacement fluid connection through which the refrigerant passes through the subcooling heat exchanger while passing through the fluid connection, the method according to claim 1.

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