Method of forming a refrigerant system

Abstract

A method for improving a refrigeration system includes modifying the system and replacing an existing refrigerant with a replacement refrigerant comprising: (1) at least about 50% by weight of R1234ze (E); (2) from greater than 0% to about 11% of HFC-134a, HFC-134, HFC-227ea, HFC-125, and a combination of two or more of these; and (3) from about 4% to about 20% by weight of HFO-1336mz (E), HFO-1224yd (Z), and combinations of these, wherein the second refrigerant: (i) has a occupational contact limit (OEL) greater than 400; (ii) classifying into 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 improving heat transfer systems using high global warming refrigerants such as R404A, R448, R449, R407 etc. The invention also extends to heat transfer systems obtainable by these methods and heat transfer methods using such improved heat transfer systems. Background Art

[0002] Mechanical refrigeration systems and related heat transfer devices (such as heat pumps and air conditioners) using refrigerant liquids are well known in the art for industrial, commercial and domestic use. 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 become a focus of more attention. In 1987, many governments signed the Montreal Protocol (Montreal Protocol) aimed at protecting the global environment, setting a timetable for the gradual elimination of CFC products. CFCs are to be replaced by more environmentally acceptable hydrogen-containing materials, i.e., hydrochlorofluorocarbons (HCFCs). One of the most commonly used hydrochlorofluorocarbon refrigerants is difluoromonochloromethane (HCFC-22). However, subsequent amendments to the Montreal Protocol have accelerated the elimination of these CFCs, and also set a timetable for the elimination of HCFCs (including HCFC-22).

[0003] Creating new refrigerants that meet environmental demands while possessing the necessary mosaic of favorable performance characteristics is a huge and complex challenge for industry. Improving one performance characteristic often worsens the performance of another, and individual commercial applications often place their own specific demands on refrigerants, exacerbating the situation.

[0004] For example, heat transfer fluids such as R22, R404A, R407A, R448A, R449A, etc. have been used in large distributed direct expansion refrigeration systems for commercial purposes, such as supermarkets, for low temperature applications or medium temperature applications. However, according to IPCC AR5, these refrigerants have unacceptably high global warming potentials (GWP): R404A (GWP = 3940), R22 (GWP = 1760), R407F (GWP = 1674), R448A (GWP = 1273), R449A (GWP = 1283). Since the fittings, hoses and / or equipment parts in such systems are likely to eventually leak, such environmentally harmful refrigerants are likely to escape into the atmosphere. In addition, since long conduit runs involve more pipe joints, valves, etc. that may potentially leak, the longer the conduit run, the greater the amount of high GWP refrigerant lost to the atmosphere when a leak occurs.

[0005] Efforts to address the environmental shortcomings of such distributed refrigeration systems present considerable engineering challenges, in part because of the large costs that would be associated with large-scale replacement of such expensive and large systems. Furthermore, conventional roof-mounted or machine room condenser / compressor systems offer high levels of efficiency and capacity, and any effort to modify these systems to be more environmentally attractive should ideally maintain such efficiency and capacity.

[0006] Efforts to address the environmental shortcomings of such distributed refrigeration systems present considerable engineering challenges, in part because of the large costs that would be associated with large-scale replacement of such expensive and large systems. Furthermore, conventional roof-mounted or machine room condenser / compressor systems offer high levels of efficiency and capacity, and any effort to modify these systems to be more environmentally attractive should ideally maintain such efficiency and capacity.

[0007] In efforts to convert conventional distributed refrigeration systems to be more environmentally friendly while maintaining efficiency and capacity, several thermodynamic and fluid flow challenges have arisen. For example, applicants have recognized that it is difficult (if not impossible) to identify environmentally friendly refrigerants (e.g., GWP of about 150 or less (as measured by AR5)) that can be simply used in existing distributed 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 reduction in performance. (See WO2020 / 223196A1). This demonstrates the difficulty in developing a viable solution to this problem.

[0008] In addition, in many applications, including in particular in many distributed refrigeration systems, the use of non-flammable compositions is generally considered important or necessary. As used herein, the term "non-flammable" refers to a compound or composition that is determined to be non-flammable, as described in ASHRAE Standard 34-2016 "Designation and Safety Classification of Refrigerants" and under the conditions described in Appendix B1 of ASHRAE Standard 34-2016, according to ASTM Standard E-681-2009 "Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases)" (which is incorporated herein by reference). Unfortunately, many HFCs that might have been expected to be used to modify existing distributed refrigeration systems are not non-flammable, as the term is used herein. For example, the fluoroalkane difluoroethane (HFC-152a) and the fluoroolefin 1,1,1-trifluoropropene (HFO-1243zf) are each flammable and therefore not feasible for use in many applications.

[0009] With regard to usage efficiency, it is important to note that a loss in refrigerant thermodynamic performance or energy efficiency can have secondary environmental impacts through increased fossil fuel use resulting from increased demand for electrical energy.

[0010] This application describes inventions that meet these and other needs. This application describes methods for improving heat transfer systems (particularly distributed systems) that enable technicians to replace refrigerants with lower GWP refrigerants while maintaining acceptable thermodynamic performance (particularly operational capabilities) and making only minor changes to the system infrastructure. Minimizing changes to the system infrastructure is particularly attractive because it minimizes equipment downtime and financial capital cost expenditures associated with the method. Summary of the invention

[0011] Applicants have discovered that the above needs and others can be met by a method for improving a heat transfer system, wherein the heat transfer system comprises:

[0012] (i) an existing refrigerant having a GWP greater than 150; and

[0013] (ii) an existing refrigeration circuit comprising, in refrigerant flow order, at least one evaporator, at least one compressor and at least one condenser and at least one expansion device, the at least one evaporator being located in or near a refrigerated space containing a product available to a consumer;

[0014] The method comprises:

[0015] (a) installing a subcooling refrigeration circuit, the subcooling refrigeration circuit comprising a subcooling refrigerant and comprising, in order of refrigerant flow, a compressor, a heat exchanger for removing heat from the subcooling refrigeration circuit, an expansion device and a subcooling heat exchanger, wherein:

[0016] 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 (eg, an expansion valve) of the existing refrigerant circuit; and

[0017] b. The subcooling heat exchanger is configured to transfer heat from the existing refrigerant circuit to the subcooling circuit; and

[0018] (b) replacing the existing refrigerant with a replacement refrigerant comprising: (1) at least about 50 weight percent R1234ze(E); (2) greater than 0% to about 11% HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more of these; and (3) about 4 weight percent to about 20 weight percent HFO-1336mzz(E), HFO-1224yd(Z), and combinations of these, wherein the replacement refrigerant: (i) has an occupational exposure limit (OEL) greater than 400; (ii) is classified as Class A1 by ASHRAE Standard 34; and (iii) has a GWP of about 150 or less.

[0019] The skilled person will appreciate that the method of improving the heat transfer system requires minimal changes to existing equipment. To implement the method of the present invention, most of the pipelines / conduits / piping do not need to be changed and in most cases will simply remain in place, as will the evaporators, condensers, compressors, etc. Instead, the existing circuit is modified by installing a subcooling heat exchanger, which enables the subcooling refrigeration circuit to further cool the replacement refrigerant on the way to the expansion device / valve and evaporator. This change greatly increases the capacity of the system, enabling the use of low GWP refrigerants while maintaining attractive thermodynamic properties. The properties of the subcooling refrigerant are not particularly limited, which provides the skilled person with the further advantage of being able to flexibly select a subcooling refrigerant to meet the specific expectations of their system.

[0020] The present invention also includes a heat transfer system obtainable by the method described above and herein. The present invention includes a heat transfer system comprising:

[0021] (a) a first (core) refrigeration circuit, the first (core) refrigeration circuit comprising:

[0022] a. in 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, and at least one compressor, the at least one evaporator being located in or near a refrigerated space containing a product available to a consumer; and

[0023] b. A core refrigerant within the first (core) refrigeration loop, wherein the core refrigerant comprises: (1) at least about 50 wt% R1234ze(E); (2) greater than 0% to about 11% HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more of these; and (3) about 4 wt% to about 20 wt% HFO-1336mzz(E), HFO-1224yd(Z), and combinations of these, wherein the core refrigerant: (i) has an occupational exposure limit (OEL) greater than 400; (ii)

[0024] Classified as Class A1 by ASHRAE Standard 34; and (iii) having a GWP of about 150 or less; and

[0025] (b) a subcooling refrigeration circuit, the subcooling refrigeration circuit comprising:

[0026] a. in refrigerant flow order, a compressor of the first refrigeration circuit, a heat exchanger for rejecting heat from the subcooling refrigeration circuit, an expansion device (e.g., an expansion valve), and the subcooling heat exchanger; 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; and

[0027] b. The subcooled refrigerant in the subcooling refrigeration circuit.

[0028] It will be apparent to the skilled person that the heat transfer system can be obtained by the method of improving the heat transfer system as described above and as described below. Therefore, the first / core refrigeration circuit of the heat transfer system corresponds to the existing refrigeration circuit used for the method of improving the heat transfer system. Therefore, each disclosure in this patent application related to the existing refrigeration circuit is expressly applicable to the first / core refrigeration circuit of the refrigeration system described above and elsewhere in this patent application (both individually and collectively).

[0029] The invention also extends to a method of heat transfer using a heat transfer system as described above and below.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

[0030] Figure 1 It is a semi-schematic diagram of a prior art system.

[0031] Figure 2 It is a semi-representation of the prior art distributed system.

[0032] Figure 3 is a semi-schematic diagram of a system according to the present invention.

[0033] Figure 4 is a semi-schematic diagram of a distributed system according to the present invention. DETAILED DESCRIPTION

[0034] definition

[0035] For purposes of the present invention, for amounts greater than 2%, the term "about" with respect to an amount expressed as a weight percent means that the amount of the component may vary by + / - 2% by weight.

[0036] For the purposes of the present invention, the term "about" with respect to a temperature in degrees Celsius (°C) means that the temperature may vary by an amount of + / - 5°C.

[0037] For purposes of the present invention, the term "about" with respect to a power usage percentage means that the percentage may vary by an amount up to 1%.

[0038] For purposes of the present invention, the term "substantially" 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.

[0039] The term "capacity" is the amount of cooling provided by the refrigerant in a refrigeration system (in BTU / hour or kW). This is determined experimentally by multiplying the enthalpy change (in BTU / lb or kJ / kg) of the refrigerant as it passes through the evaporator by the mass flow rate of the refrigerant. The enthalpy can be determined by measurements of the pressure and temperature of the refrigerant. The capacity of a refrigeration system relates to the ability to keep an area cooled at a specific temperature. The capacity of a refrigerant represents the amount of cooling or heating it provides, and provides some measure of the ability of a compressor to pump heat for a given volume flow of refrigerant. In other words, given a specific compressor, a refrigerant with a higher capacity will deliver more cooling or heating power.

[0040] The phrase "coefficient of performance" (hereinafter referred to as "COP") is a measure of the performance of a refrigerant that is generally accepted, and 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, the term represents the ratio of the available refrigeration or cooling capacity to the energy applied by the compressor when compressing the vapor, and therefore represents the ability of a given compressor to pump heat for a given volume flow of a heat transfer fluid such as a refrigerant. In other words, given a specific compressor, a refrigerant with a higher COP will deliver more cooling or heating power. A method for estimating the COP of a refrigerant under specific operating conditions is to estimate from the thermodynamic properties of the refrigerant using standard refrigeration cycle analysis techniques (see, for example, RC Downing, "FLUOROCARBON REFRIGERANTS HANDBOOK", Chapter 3, Prentice-Hall, 1988, which is incorporated herein by reference in its entirety).

[0041] 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 allows the use of existing equipment without activating thermal protection aspects of the system, which are preferably designed to protect the compressor components, and avoids the use of expensive control measures (such as injection of liquid) to reduce the discharge temperature.

[0042] As used herein, the term "centralized refrigeration system" means a refrigeration system that includes one or more centrally located compressors or compressor racks and one or more centrally located condensers and a plurality of evaporators that are located remotely from the centralized compressors or compressor racks and receive liquid refrigerant from the centrally located condensers.

[0043] In contrast to a centralized system, the term "distributed refrigeration system" means a system comprising several compressors or compressor racks that are distributed near or very close to locations where refrigeration is needed (eg, display cases).

[0044] As used herein, "direct expansion" means a heat transfer system utilizing an evaporator, wherein liquid refrigerant enters the evaporator and flows through a coil (preferably a tubular coil) and evaporates absorbing heat from air circulating in the display case, and which utilizes a thermal expansion valve at the inlet of the evaporator and which is controlled to supply sufficient refrigerant to cause substantially all of the refrigerant to evaporate at the evaporator outlet and optionally with a predetermined amount of superheat at the outlet.

[0045] The phrase "global warming potential" (hereinafter "GWP") was developed to allow the global warming impact of different gases to be compared, and as used herein refers to the GWP as determined by AR5 as described above. Specifically, it is a measure of how much energy one ton of a gas emitted in a given time period will absorb relative to one ton of carbon dioxide emitted. The greater the GWP, the warmer the earth will be made by a given gas compared to CO2 in that time period. The time period commonly used for GWP is 100 years. GWP provides a common measure - allowing analysts to add up emission estimates for different gases. See http: / / www.protocolodemontreal.org.br / site / images / publicacoes / setor_manufatur a_equipamentos_refrigeracao_arcondicionado / Como_calcular_el_Potencial_de_Calentamiento_Atmosferico_en_las_mezclas_de_refrigerantes.pdf

[0046] The term “occupational exposure limit (OEL)” is based on the ASHRAE Standard 34-2016 Nomenclature and Safety Classification of Refrigerants.

[0047] As used herein, the phrase "acceptable toxicity" means that the composition is classified as Class "A" by ASHRAE Standard 34-2016 Nomenclature and Safety Classification of Refrigerants, and is described in Appendix B1 of ASHRAE Standard 34-2016 (as various standards existed before the filing date of this application). Non-flammable and low toxicity materials are classified as Class "A1" by ASHRAE Standard 34-2016 Nomenclature and Safety Classification of Refrigerants, and are described in Appendix B1 of ASHRAE Standard 34-2016 (as various standards existed before the filing date of this application).

[0048] The term "mass flow rate" is the mass of refrigerant passing through a conduit per unit time.

[0049] As used herein, the term "replacement" means the use of the composition of the present invention in a heat transfer system that has been designed for use with another refrigerant, or is suitable for use with another refrigerant. By way of example, when the refrigerant or heat transfer composition of the present invention is used in a heat transfer system that is designed for use with R-410A, then the refrigerant or heat transfer composition of the present invention is a replacement for R-410A in the system. It should therefore be understood that the term "replacement" includes the use of the refrigerant and heat transfer composition of the present invention in new and existing systems that have been designed for use with R-410A, are typically used with R-404A, or are suitable for use with R-404A.

[0050] The term "glide" applies to non-azeotropic refrigerant mixtures having different temperatures during the phase change process in an 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.

[0051] The term "cryogenic 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 up to and including -12°C.

[0052] 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.

[0053] As used herein, the term "supermarket refrigeration" refers to commercial refrigeration systems used to keep foods chilled or frozen in both product display cases and storage refrigerators.

[0054] As used herein, the term "subcooling" refers to cooling the replacement (or core) refrigerant to a temperature significantly below the temperature at the condenser outlet. Figure 3 and Figure 4 , subcooling is the difference between the condensing temperature and the liquid temperature at the inlet of the expansion device / valve.

[0055] The term "normal boiling point" refers to the boiling point of a single component measured at 1 atmosphere pressure, and refers to the initial boiling point of a blend of components at 1 atmosphere pressure.

[0056] The term "R22" means chlorodifluoromethane.

[0057] As used herein, the terms "HFC32" and "R32" each mean difluoromethane.

[0058] The terms "HFC-125" and "R125" mean pentafluoroethane.

[0059] The terms "HFC-134a" and "R134a" mean 1,1,1,2-tetrafluoroethane.

[0060] The terms "HFC-134" and "R134" mean 1,1,2,2-tetrafluoroethane.

[0061] The term "R143a" means 1,1,1-trifluoroethane.

[0062] The term R290 means propane.

[0063] The term "R404A" means a combination of about 44 wt% R-125, about 52 wt% R143a, and about 4 wt% R-134a.

[0064] The term "R407A" means a combination of about 20 wt% R-32, about 40 wt% R125, and about 40 wt% R-134a.

[0065] The term "R407B" means a combination of about 10 wt% R-32, about 70 wt% R125, and about 20 wt% R-134a.

[0066] The term "R407C" means a combination of about 23 wt% R-32, about 25 wt% R125, and about 52 wt% R-134a.

[0067] The term "R407D" means a combination of about 15 wt% R-32, about 15 wt% R125, and about 70 wt% R-134a.

[0068] The term "R407F" means a combination of about 40 wt% R-32, about 30 wt% R125, and about 30 wt% R-134a.

[0069] The term "R407" means any one of R407A, R407B, R407C, R407D and R407F.

[0070] The term "R448A" means a combination of about 26 wt% R-32, about 26 wt% R125, and about 21 wt% R-134a.

[0071] The term "R448A" means a combination of about 26 wt% R-32, about 26 wt% R125, and about 21 wt% R-134a.

[0072] The term "R448" means any refrigerant named R448, including R448A.

[0073] The term "R449A" means a combination of about 24.3 wt% R-32, about 24.7 wt% R125, and about 25.7 wt% R-134a.

[0074] The term "R449" means any refrigerant named R449, including R449A.

[0075] The term "R454B" means a combination of about 68.9 wt% R-32 and about 31.1 wt% R1234yf.

[0076] The term "R454" means any refrigerant named R454, including R454B.

[0077] The term "R513A" means a combination of about 44 wt% R-134a and about 56 wt% R1234yf.

[0078] The term "R449" means any refrigerant named R449, including R449A.

[0079] As used herein, the terms "HFO1234yf" and "R1234yf" each mean 2,3,3,3-tetrafluoropropene.

[0080] As used herein, the terms "HFO1234ze(E)", "R1234ze(E)" and "1234ze(E)" each mean trans-1,3,3,3-tetrafluoropropene. Unless otherwise indicated, "HFO1234ze", "R1234ze" and "1234ze" mean trans-1,3,3,3-tetrafluoropropene.

[0081] Reference herein to a set of defined items includes all such defined items including all such items designated with a suffix.

[0082] System and method

[0083] The present invention incorporates a method of improving existing heat transfer systems.

[0084] Before the improvement, the existing heat transfer system included:

[0085] (i) an existing refrigerant having a GWP greater than 150 (e.g., greater than 500 or greater than 1200);

[0086] (ii) an existing refrigeration circuit comprising, in flow order, 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), the at least one evaporator being located in or near a refrigerated space containing a product available to a consumer;

[0087] By reference Figure 1 and Figure 2 , can further understand the existing heat transfer system, the Figure 1 and Figure 2 is a representative example of an existing distributed refrigeration system of the type to be improved according to the present invention. As the skilled person will appreciate, these types of systems operate by circulating a refrigerant around a vapor compression refrigeration loop. At least one evaporator (4, 4a) is located in or near a refrigerated space, such as a space containing consumer products available to consumers. The evaporator is used to transfer heat from the refrigerated space to the refrigerant, as a result of which the refrigerant is generally changed from a liquid / vapor to a vapor. The vapor passes through at least one compressor or compressor rack (5), which compresses the refrigerant to a higher temperature. The compressed refrigerant vapor passes through a condenser (1), in which the refrigerant releases heat during its conversion to a liquid. A receiver (3) is optionally located downstream of the condenser to provide a reservoir of liquid refrigerant to feed an expansion device 3. Before returning to the at least one evaporator (4, 4a), the refrigerant is rapidly evaporated while passing through at least one expansion device (3, 3a) (e.g., at least one expansion valve) to produce a liquid-vapor that receives the desired cooling in the at least one evaporator. When there are multiple evaporators and expansion devices or valves (3a), each evaporator / expansion valve pair may serve a different refrigeration cabinet in a distributed system, such as a commercial store such as a food store (e.g., a supermarket), optionally operating at different temperatures.

[0088] At least one evaporator (4, 4a) is preferably configured to operate as a medium temperature evaporator. Optionally, the evaporator is configured to operate at a temperature from -12°C to 0°C.

[0089] Despite Figure 1 and Figure 2 , but in practice, each of these piping networks typically represents a large and long series of conduits for conveying liquid refrigerant from an accumulator receiver (3), which is typically placed at a location remote from the display cabinets together with the compressor or compressor rack (5) and the condenser (1). The piping network is therefore typically large, covering a distance from, for example, the roof or machine room of a supermarket to the grounds of the supermarket in order to reach the multiple display cabinets located there.

[0090] Those skilled in the art should also understand that although Figure 1 and Figure 2 The compressor or compressor rack in the embodiment is depicted as having two compressors, but in practice, the compressor / compressor rack may include one compressor up to about 5 compressors, depending on the individual application. Existing refrigerant systems provided according to the present invention may represent compressor operating capacities of about 3 kW to about 500 kW. With regard 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 of these.

[0091] Existing refrigerants in existing refrigeration circuits typically have a GWP (determined according to AR5) greater than 150, greater than 500, or greater than 1200. Preferred existing refrigerants include R404A, R407 (including each of R407A, R407B, R407C, R407D), R448 (all letter designations), R449 (all letter designations), R454, R513, R22, and 134a, more preferably R404A, R407A, R407B, R407C, R407D, R448 (all letter designations), and R449 (all letter designations), and most preferably R404A.

[0092] The present invention relates to improving systems such as Figure 1 and Figure 2 of the type disclosed in to improve the environmental friendliness of the system while achieving at least acceptable performance of the entire system and preferably improving the overall heat transfer performance without compromising the safety of the system in terms of toxicity and flammability of the refrigerant exposed to areas open to the public.

[0093] The improvement method generally involves two main steps: inserting a subcooling refrigeration circuit connected via a subcooling heat exchanger; and replacing the existing refrigerant with a replacement refrigerant (e.g., by removing substantially all of the existing refrigerant before adding the replacement refrigerant to the system). The skilled person will recognize that these steps can be performed in any order according to the practical limitations of the system to which they are improved. For example, if it is practical to isolate the existing refrigerant away from the area of ​​the existing system that will be mechanically changed or replaced, it is possible to replace the existing refrigerant after installing the subcooling refrigeration circuit without the risk of leakage of the existing refrigerant. If it is not practical to isolate the existing refrigerant in this manner, which is typically the case, 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. Doing so reduces the risk of leakage of the existing refrigerant. The method steps are discussed below in an order consistent with the sequence of steps shown in claim 1, but the skilled person will recognize that the present invention is not limited to this order of events.

[0094] The subcooling heat exchanger is installed in the fluid connection between the condenser and at least one expansion device (e.g. at least one expansion valve) of the existing refrigeration circuit. If a receiver (2) is present, the subcooling heat exchanger is usually installed in the fluid connection between the receiver and the at least one expansion device. This task usually involves removing some of the entirety of the fluid connection by completely replacing the pipe or by removing sections of the pipe.

[0095] The nature of the subcooling heat exchanger (6) is not particularly limited and it is within the skill of the artisan to select an appropriate design for their system. However, the heat exchanger is configured to thermally couple the existing circuit and the subcooling circuit being installed by transferring heat from the existing heat transfer circuit to the subcooling refrigeration circuit. In this way, the subcooling circuit assists in providing additional cooling of the refrigerant in the existing refrigeration circuit before the refrigerant reaches the expansion device or valve (3, 3a).

[0096] As mentioned above, the subcooling heat exchanger forms a key part of the subcooling refrigeration circuit. This circuit can be implemented, for example Figure 3 and Figure 4 In the form shown, the Figure 3 and Figure 4 Describes the method according to claim 1 by applying Figure 1 and Figure 2 The heat transfer system is obtained by the heat transfer system. Figure 3 and Figure 4 In the figure, the remainder of the existing refrigeration circuit (101) is shown as being thermally coupled to the subcooling refrigeration circuit (102) via a subcooling heat exchanger (6). The subcooling heat exchanger is configured to cool the refrigerant downstream of the condenser (1) through the expansion device / valve (3, 3a) and the optional receiver (2). As shown, the subcooling circuit also includes a compressor (7), a heat exchanger (8) for removing heat from the subcooling refrigerant, and an expansion valve (9). The heat exchanger (8) can remove heat in a variety of different ways, which introduces yet more advantageous versatility to the present invention. For example, the heat exchanger (8) can remove heat to the surrounding air, such as outside a building, or it can remove heat to water. The water heated by the latter can itself be used for heating purposes, such as residential or commercial heating.

[0097] The property of subcooling refrigerant is not particularly limited. This flexibility is another advantage of the present invention, because it provides the technical staff with the degree of freedom to choose based on the preference of itself and the demand of its improved particular system. Subcooling refrigerant can advantageously be selected from the group consisting of the following: R455A, R454C, propane, R1234yf, R152a, R1234ze, R471A, R476A and B6. It has been found that these refrigerants are particularly effective in the subcooling refrigeration circuit. For example, it has been found that, compared with the existing refrigeration circuit (without subcooling) using R404A as refrigerant, the subcooling refrigeration circuit using these refrigerants has improved the coefficient of performance by at least 30 weight %. More preferably, the subcooling refrigerant is selected from R455A, R454C, R1234yf, R1234ze and R471A, most preferably R455A and R454C. The subcooling refrigeration circuit comprising a subcooling heat exchanger is preferably located outside the area usually exposed to the public. For example, if the heat transfer system is used in a commercial environment such as a supermarket, the subcooling refrigeration circuit is typically located outside the area exposed to customers. Positioning the subcooling refrigeration circuit in this way is preferred because it improves safety when using flammable subcooled refrigerants.

[0098] Although the conditions for subcooling the refrigerant may vary widely, it is preferred that the subcooling temperature is in the range of 10°C to 70°C, preferably 30°C to 50°C, for example about 40°C.

[0099] Importantly, the present method involves the use of an alternative refrigerant comprising: (1) at least about 50 weight percent R1234ze (E); (2) greater than 0% to about 11% HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more of these; and (3) about 4 weight percent to about 20 weight percent HFO-1336mzz (E), HFO-1224yd (Z), and combinations of these, wherein the alternative refrigerant: (i) has an occupational exposure limit (OEL) greater than 400; (ii) is classified as Class A1 by ASHRAE Standard 34; and (iii) has a GWP of about 150 or less. Table A below identifies two alternative refrigerant blends that meet these criteria and provide substantial and unexpected advantages according to the present invention, it being understood that the amounts in the table are to be considered preceded by "about":

[0100] Table A

[0101]

[0102] In a preferred embodiment, the replacement refrigerant is selected from the composition range specified in Table B below, it being understood that the amounts in the table are to be considered to be preceded by "about":

[0103] Table B

[0104]

[0105]

[0106] The skilled person will recognize that B4 is a scaled-down version of B1 , B5 is a scaled-down version of B2 , and B6 is a scaled-down version of B6 .

[0107] In a preferred embodiment, the replacement refrigerant has a normal boiling point within the range specified in Table C below, it being understood that the amounts in the table are to be considered to be preceded by the word "about":

[0108] Table C

[0109] Refrigerants→ C1 C2 C3 Standard boiling point range, ℃ -40 to 20 -20 to 20 -20 to -12

[0110] In a preferred embodiment, the replacement refrigerant has a glide within the range specified in Table D below, it being understood that the amounts in the table are to be considered to be preceded by the word "about":

[0111] Table D

[0112] Refrigerants→ D1 D2 D3 Slip, °K <＝5 <＝4 <＝3

[0113] An advantage of the present invention is that the method of improving an existing heat transfer system requires little or no changes to much of the equipment that forms the existing heat transfer system. Except for the conduits that are partially or completely removed to enable installation of a subcooling heat exchanger, little or no equipment changes are required elsewhere. This is because comparable or improved thermodynamic performance is achieved without radically changing the operating conditions of the existing refrigeration circuit. Generally speaking, the conduits / pipes, condensers, expansion valves, compressors and pressure seals of the system do not need to be changed to accommodate the present invention, which reduces the time, complexity and cost associated with improving a heat transfer system.

[0114] Reducing the number of mandatory equipment changes also frees up budget and time to make voluntary equipment changes to further enhance the system, if the technician chooses. For example, the technician may choose to improve the performance of the system by increasing the level of insulation in the space cooled by the evaporator, for example by adding doors in the space refrigerated by at least one evaporator, such as a shop / supermarket refrigeration unit. Adding doors to shop / supermarket refrigeration units is particularly useful when the existing refrigerant is R448A or R404A, as it helps to achieve a close match in terms of capacity. When replacing R448A or R404A as the existing refrigerant, capacity can also be improved by replacing the expansion valve (3, 3a) to change the physical properties of the replacement refrigerant before entering the evaporator (4, 4a).

[0115] As mentioned above, the present invention also extends to heat transfer systems. These heat transfer systems can be obtained by modifying the method of the above-mentioned heat transfer system, but they are not limited to those that have been produced in this way. The heat transfer system comprises:

[0116] (a) a first (core) refrigeration circuit, the first (core) refrigeration circuit comprising:

[0117] a. a core refrigerant in the first (core) refrigeration circuit, wherein the core refrigerant comprises: (1) at least about 50% by weight of R1234ze(E); (2) greater than 0% to about 11%

[0118] (i) an occupational exposure limit (OEL) greater than 400; (ii) is classified as Class A1 by ASHRAE Standard 34; and (iii) has a GWP of about 150 or less; and

[0119] b. at least one evaporator, at least one compressor, at least one condenser, and at least one expansion device, in refrigerant flow order, the at least one evaporator being located in or near a refrigerated space containing a product available to a consumer; and

[0120] (b) a subcooling refrigeration circuit, the subcooling refrigeration circuit comprising:

[0121] a. a subcooled refrigerant within the subcooled refrigeration circuit; and

[0122] b. In refrigerant flow order, a compressor, an evaporator for removing heat from the subcooling refrigerant / circuit, an expansion device, a subcooling heat exchanger, and a subcooling refrigerant, wherein the subcooling heat exchanger is configured to transfer heat from the at least one condenser of the first (core) refrigerant circuit to the at least one expansion device (e.g.,

[0123] expansion valve) to the subcooling refrigeration circuit.

[0124] Preferred features of the method of improving a heat transfer system are expressly applicable to the heat transfer system. For example, the preferred refrigerants and operating conditions described for the method of improving a heat transfer system are expressly applicable to the above-described heat transfer system as being obtainable by such a method.

[0125] The invention also extends to heat transfer methods using heat transfer systems, which can be obtained by the method of improving the heat transfer system. The benefit of the improved heat transfer system is that it can be used for a variety of end uses. Particularly preferred types of heat transfer systems are low temperature refrigeration systems or medium temperature refrigeration systems, preferably medium temperature refrigeration systems. Preferred end uses are refrigeration, stationary refrigeration, commercial stationary refrigeration, for example in food warehouses, cold stores and food stores, such as supermarkets.

[0126] Refrigerant combination

[0127] As will be appreciated by those skilled in the art, the present invention relates to methods and systems for using different refrigerants for different purposes. Tables E to G below provide preferred refrigerant combinations. The skilled artisan will recognize that:

[0128] ●Methods for improving refrigeration systems involve existing refrigerants, replacement refrigerants and subcooling refrigerants.

[0129] The heat transfer systems that can be produced by these methods have a core refrigerant (i.e., a replacement refrigerant) and a subcooling refrigerant, and the heat transfer methods using these heat transfer systems have the same core refrigerant and subcooling refrigerant. In other words, the "Existing Refrigerant" column in Table E can be ignored when looking at the refrigerant combinations for these heat transfer systems and heat transfer methods.

[0130] Table E

[0131]

[0132]

[0133]

[0134]

[0135]

[0136] Table F

[0137]

[0138]

[0139]

[0140]

[0141] Table G

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148] The skilled person will also recognize that it is advantageous to include compressor lubricants in combination with alternative / core refrigerants and / or subcooling refrigerants. Useful compressor lubricants include polyol esters (POE), mineral oils, alkylbenzenes (AB), polyvinyl ethers (PVE), poly(alkylene glycols) (PAGs) and poly(alpha-olefins) (PAOs). Therefore, the skilled person will recognize that the combination of features in Tables H and I is also advantageous.

[0149] Table H

[0150]

[0151]

[0152]

[0153]

[0154]

[0155]

[0156]

[0157]

[0158]

[0159]

[0160]

[0161]

[0162] Table I

[0163]

[0164]

[0165]

[0166]

[0167]

[0168]

[0169]

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176]

[0177]

[0178]

[0179]

[0180] Example

[0181] The following examples are provided for the purpose of illustrating the present invention, but not to limit the scope of the present invention.

[0182] When evaluating methods for improving refrigeration systems, including replacing a higher GWP refrigerant with a lower GWP refrigerant, it is important to consider performance parameters such as: (1) the volume 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.

[0183] Comparative Example 1 - Refrigeration System Using R-404A as Refrigerant

[0184] Figure 1 A refrigeration system of the type disclosed in is provided with R-404A as the existing refrigerant. The system operating conditions using R-404A as the refrigerant are:

[0185] Cooling capacity: 45.0kW

[0186] Isentropic efficiency: 0.65

[0187] Volumetric efficiency: 100%

[0188] Condensation temperature: 40℃

[0189] Overheat: 10℃

[0190] Evaporation temperature: -10℃

[0191] Although this system operates well from a thermodynamic and heat transfer performance point of view, it is highly undesirable from the point of view of its environmental impact since the entire system contains the circulating high GWP refrigerant R404A. The performance of this system is further summarized in the results Tables 1 and 2 below.

[0192] Comparative Example 2 - Refrigeration System Using R-471A Instead of R-404A

[0193] 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:

[0194] R 471A components weight% 1234ze(E) 78.7 1336mzz(E) 17 R227ea 4.3 characteristic GWP (according to IPCC AR5) 148

[0195] The performance of this system is further summarized in the result tables 1 and 2 below.

[0196] Results Table 1

[0197]

[0198]

[0199] As can be seen from the results of the above Results Table 1, replacing R-404A with R-417A improves the system from the standpoint of including a low GWP refrigerant, but reduces cooling capacity. The present invention addresses this and other problems.

[0200] Example 1 - By installing a dedicated mechanical subcooling system (DMSS) using R455A and using refrigerant A1 (R- 471A) replaces R404A to improve refrigeration system

[0201] The heat transfer system of Comparative Example 1 containing the existing refrigerant R404A was used as a heat transfer system to form a heat transfer system. Figure 3 The starting point of the improved heat transfer system shown. The refrigeration system is emptied of refrigerant R404A and a subcooling heat exchanger (6) is installed between the receiver (2) and the expansion valve (3). The subcooling heat exchanger is configured to exchange heat between the main refrigeration circuit and a dedicated mechanical subcooling system (DMSS) (102) which is used to cool the refrigerant flowing through the existing refrigerant circuit. The DMSS evaporation temperature is 0°C and the condensing temperature is 40°C. Other details of the DMSS are provided in the results table 2 below.

[0202] Once modified, refrigerant R471A was used as the core circuit refrigerant and refrigerant R455A was used for DMSS refrigeration. The performance of the modified refrigeration system is summarized in the results table 2 below.

[0203] Example 2 - By installing a dedicated mechanical subcooling system (DMSS) using R455A, using refrigerant A1 (R- 471A) to replace R404A and modify the heat exchanger to improve the refrigeration system

[0204] Example 1 was repeated except that the heat exchanger was modified to accommodate low pressure fluids. The performance of the improved refrigeration system is summarized in the results Table 2 below.

[0205] Results Table 2

[0206]

[0207]

[0208] As can be seen from the results in Table 2, replacing the high GWP refrigerant R404A with a lower GWP refrigerant, such as R471A, results in an unacceptable drop in cooling capacity. However, this disadvantage can be surprisingly mitigated by installing a deep subcooling system between the condenser and the evaporator. The cooling capacity increases from 39% of R404A to 57% of R404A without making other changes. Modifying the heat exchanger further increases this ratio to 70% of R404A.

[0209] These modifications to the system of Comparative Example 1 bring about a number of advantages. First, the GWP of the refrigerant circulating around the primary loop can be significantly reduced without sacrificing intolerable levels of cooling capacity. Second, the modifications to the primary refrigeration loop itself are relatively minor, requiring only the installation of a heat exchanger between the condenser and the evaporator.

[0210] Example 3 - By installing a dedicated mechanical subcooling system (DMSS) using R454C and using refrigerant A1 (R- 471A) replaces R404A to improve refrigeration system

[0211] Example 1 was repeated, but using refrigerant R454C in the DMSS circuit. The performance of the improved refrigeration system is summarized in the results table 3 below.

[0212] Example 4 - By installing a dedicated mechanical subcooling system (DMSS) using R454C, using refrigerant A1 (R- 471A) to replace R404A and modify the heat exchanger to improve the refrigeration system

[0213] Example 2 was repeated, but using refrigerant R454C in the DMSS circuit. The performance of the improved refrigeration system is summarized in the results table 3 below.

[0214] Results Table 3

[0215]

[0216]

[0217] As with 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 a variety of refrigerants can be used in a DMSS circuit.

[0218] Example 5 - By installing a dedicated mechanical subcooling system (DMSS) using propane and using refrigerant A1 (R- 471A) replaces R404A to improve refrigeration system

[0219] Example 1 was repeated, but using propane as the refrigerant in the DMSS loop. The performance of the improved refrigeration system is summarized in the results table 4 below.

[0220] Example 6 - By installing a dedicated mechanical subcooling system (DMSS) using propane, using refrigerant A1 (R-471A) Improve refrigeration system by replacing R404A and modifying heat exchanger

[0221] Example 2 was repeated, but using propane as the refrigerant in the DMSS loop. The performance of the improved refrigeration system is summarized in the results table 4 below.

[0222] Results Table 4

[0223]

[0224]

[0225] Examples 5 and 6 show that good cooling capacity can be obtained using the present invention and further emphasize the flexibility of the subcooling refrigerant.

[0226] Example 7 - By installing a dedicated mechanical subcooling system (DMSS) using HFO-1234yf and using refrigerant A1 (R-471A) replaces R404A to improve refrigeration system

[0227] Example 1 was repeated, but using refrigerant HFO-1234yf in the DMSS loop. The performance of the improved refrigeration system is summarized in the results Table 4 below.

[0228] Example 8 - By installing a dedicated mechanical subcooling system (DMSS) using HFO-1234yf and using refrigerant A1 (R-471A) replaces R404A and modifies the heat exchanger to improve the refrigeration system

[0229] Example 2 was repeated, but using refrigerant HFO-1234yf in the DMSS loop. The performance of the improved refrigeration system is summarized in the results Table 4 below.

[0230] Results Table 4

[0231]

[0232]

[0233] Examples 7 and 8 show that good cooling capacity can be obtained using the present invention and further emphasize the flexibility of the subcooling refrigerant.

[0234] Example 9 - By installing a dedicated mechanical subcooling system (DMSS) using R152a and using refrigerant A1 (R- 471A) replaces R404A to improve refrigeration system

[0235] Example 1 was repeated, but using refrigerant R152a in the DMSS circuit. The performance of the improved refrigeration system is summarized in the results table 5 below.

[0236] Example 10 - By installing a dedicated mechanical subcooling system (DMSS) using R152a, using refrigerant A1 (R- 471A) to replace R404A and modify the heat exchanger to improve the refrigeration system

[0237] Example 2 was repeated, but using refrigerant R152a in the DMSS circuit. The performance of the improved refrigeration system is summarized in the results table 5 below.

[0238] Results Table 5

[0239]

[0240] Examples 9 and 10 show that good cooling capacity can be obtained using the present invention and further emphasize the flexibility of the subcooling refrigerant.

[0241] Example 11 - By installing a dedicated mechanical subcooling system (DMSS) using HFO-1234(E) and using the refrigerant A1(R-471A) replaces R404A to improve refrigeration system

[0242] Example 1 was repeated, but using refrigerant HFO-1234(E) in the DMSS loop. The performance of the improved refrigeration system is summarized in the results Table 6 below.

[0243] Example 12 - By installing a dedicated mechanical subcooling system (DMSS) using HFO-1234 (E), using refrigerant A1 (R-471A) replaces R404A and modifies the heat exchanger to improve the refrigeration system

[0244] Example 2 was repeated, but using refrigerant HFO-1234(E) in the DMSS loop. The performance of the improved refrigeration system is summarized in the results Table 6 below.

[0245] Results Table 6

[0246]

[0247] Examples 11 and 12 show that good cooling capacity can be obtained using the present invention and further emphasize the flexibility of the subcooling refrigerant.

[0248] Example 13 - By installing a dedicated mechanical subcooling system (DMSS) using R471A and using refrigerant A1 (R- 471A) replaces R404A to improve refrigeration system

[0249] Example 1 was repeated, but using refrigerant R471A in the DMSS circuit. The performance of the improved refrigeration system is summarized in the results table 7 below.

[0250] Example 14 - By installing a dedicated mechanical subcooling system (DMSS) using R471A, using refrigerant A1 (R- 471A) to replace R404A and modify the heat exchanger to improve the refrigeration system

[0251] Example 2 was repeated, but using refrigerant R471A in the DMSS circuit. The performance of the improved refrigeration system is summarized in the results table 7 below.

[0252] Results Table 7

[0253]

[0254] Examples 13 and 14 show that good cooling capacity can be obtained using the present invention and further emphasize the flexibility of the subcooling refrigerant.

[0255] Example 15 - Improvement of refrigeration by installing a dedicated mechanical subcooling system (DMSS) and replacing R404A with R476A system

[0256] Examples 1 to 14 were repeated, but R476A was substituted for R404A. Similar favorable and unexpected results were achieved in many of the experiments within this example.

[0257] Example 16 - Improvement by installing a dedicated mechanical subcooling system (DMSS) and replacing R404A with refrigerant B6 Refrigeration system

[0258] Examples 1 to 14 were repeated, but with refrigerant B6 replacing R404A. Similar favorable and unexpected results were achieved in many of the experiments within this example.

[0259] Example 17 - Improvement of refrigeration system by installing a dedicated mechanical subcooling system (DMSS) and replacing R448 with 471A System

[0260] Examples 1 to 14 were repeated, but R471A was substituted for R448. Similar favorable and unexpected results were achieved in many of the experiments within this example.

[0261] Example 18 - Improvement of refrigeration by installing a dedicated mechanical subcooling system (DMSS) and replacing R448 with R476A system

[0262] Examples 1 to 14 were repeated, but R476A was substituted for R448. Similar favorable and unexpected results were achieved in many of the experiments within this example.

[0263] Example 19 - Improvement of the system by installing a dedicated mechanical subcooling system (DMSS) and replacing R448 with refrigerant B6 Cold System

[0264] Examples 1 to 14 were repeated, but with refrigerant B6 replacing R448. Similar favorable and unexpected results were achieved in many of the experiments within this example.

[0265] Example 20 - Improvement of refrigeration by installing a dedicated mechanical subcooling system (DMSS) and replacing R134a with R471A system

[0266] Examples 1 to 14 were repeated, but R471A was substituted for R134a. Similar favorable and unexpected results were achieved in many of the experiments within this example.

[0267] Example 21 - Improvement of refrigeration by installing a dedicated mechanical subcooling system (DMSS) and replacing R134a with R476A system

[0268] Examples 1 to 14 were repeated, but R476A was substituted for R134a. Similar favorable and unexpected results were achieved in many of the experiments within this example.

[0269] Example 22 - Improvement by installing a dedicated mechanical subcooling system (DMSS) and replacing R134a with refrigerant B6 Refrigeration system

[0270] Examples 1 to 14 were repeated, but with refrigerant B6 replacing R134a. Similar favorable and unexpected results were achieved in many of the experiments within this example.

Claims

1. A method for improving a heat transfer system, wherein the heat transfer system comprises: (iii) existing refrigerants having a GWP greater than 150; and (iv) an existing refrigeration circuit comprising, in refrigerant flow order, at least one evaporator, at least one compressor, at least one condenser, and at least one expansion device, the at least one evaporator being located in or near a refrigerated space containing a product available to a consumer; The method comprises: (a) installing a subcooling refrigeration circuit, the subcooling refrigeration circuit comprising a subcooling refrigerant and comprising, in flow order, a compressor, a heat exchanger for removing heat from the subcooling refrigerant, an expansion device and a subcooling heat exchanger, wherein: 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 of the existing refrigeration circuit; and b. The subcooling heat exchanger is configured to transfer heat from the existing refrigeration circuit to the subcooling refrigeration circuit; and (b) replacing the existing refrigerant with a replacement refrigerant, the replacement refrigerant comprising: (1) at least about 50 weight percent R1234ze(E); (2) greater than 0% to about 11% HFC-134a, HFC-134, HFC-227ea, HFC-125, and combinations of two or more of these; and (3) about 4 weight percent to about 20 weight percent HFO-1336mzz(E), HFO-1224yd(Z), and combinations of these, wherein the replacement refrigerant: (i) has an occupational exposure limit (OEL) greater than 400; (ii) is classified as Class A1 by ASHRAE Standard 34; and (iii) has 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 the group consisting of R404A, R407, R448, R449, R454, R513, R22 and 134a.

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

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

6. The method of claim 1, wherein the replacement refrigerant is used in combination with a lubricant selected from the group consisting of polyol esters (POE), mineral oil, alkyl benzene (AB), polyvinyl ether (PVE), and poly(alpha-olefin) (PAO).

7. The method of claim 1, wherein the replacement refrigerant is used in combination with a poly(alkylene glycol) (PAG) lubricant.

8. The method of claim 1, wherein the replacement refrigerant is used in combination with a polyvinyl ether (PVE) lubricant.

9. The method of claim 1, wherein the subcooling refrigerant and the replacement refrigerant are used in combination with a lubricant independently selected from polyol esters (POE), mineral oils, alkylbenzenes (AB), polyvinyl ethers (PVE), and poly(alpha-olefins) (PAO).

10. The method of claim 1, wherein step (b) comprises: removing at least a portion of a fluid connection between the at least one evaporator and the at least one expansion device of the existing refrigerant circuit; as well as A replacement fluid connection is installed, wherein the refrigerant passes through the subcooling heat exchanger during passage through the fluid connection.

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