EP4034821A1

EP4034821A1 - Heat exchanger for mixed refrigerant systems

Info

Publication number: EP4034821A1
Application number: EP20785883.8A
Authority: EP
Inventors: Richard G. Lord
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2019-09-24
Filing date: 2020-09-18
Publication date: 2022-08-03
Also published as: US20220252311A1; CN114424002A; WO2021061520A1

Abstract

A vapor compression cycle is provided including a compressor, condenser, expansion device, and evaporator fluidly connected via one or more fluid conduits, A fluid circulating within the one of more fluid conduits has a high temperature glide. An intermediate heat exchanger has a first part including at least one pass there through and a second part including at least one pass there through. The first part is arranged downstream from the condenser and at least a portion of the fluid output from the condenser is provided to the first part of the intermediate heat exchanger. Within the first part, a temperature of the at least a portion of the fluid output from the condenser is reduced.

Description

HEAT EXCHANGER FOR MIXED REFRIGERANT SYSTEMS CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Application No.62/904,921, filed on September 24, 2019, which is incorporated herein by reference in its entirety. BACKGROUND [0001] Exemplary embodiments disclosed herein relate generally to a refrigeration system, and more particularly, to a refrigeration system suitable for use with a refrigerant mixture having a high temperature glide fluid. [0002] One of the most common technologies in use for residential and commercial refrigeration and air conditioning is the vapor compression refrigerant heat transfer loop. These loops typically circulate a refrigerant having appropriate thermodynamic properties through a loop that comprises a compressor, a heat rejection heat exchanger (i.e., heat exchanger condenser), an expansion device and a heat absorption heat exchanger (i.e., heat exchanger evaporator). Vapor compression refrigerant loops effectively provide cooling and refrigeration in a variety of settings, and in some situations can be run in reverse as a heat pump. [0003] It has been determined that commonly used refrigerants, such as the commonly used R-410A for example, have unacceptable global warming potential (GWP) such that their use will be phased out for many HVAC&R applications. There are some Non- flammable, low GWP refrigerants that could be used to replace the common refrigerant using in most HVAC comfort cooling products but there are not good higher pressure refrigerants and many of the options being evaluated are mixtures that are also mildly flammable and also have higher glides like R-454B. BRIEF DESCRIPTION [0004] According to an embodiment, a vapor compression cycle is provided including a compressor, condenser, expansion device, and evaporator fluidly connected via one or more fluid conduits. A fluid circulating within the one of more fluid conduits has a high temperature glide. An intermediate heat exchanger has a first part including at least one pass there through and a second part including at least one pass there through. The first part is arranged downstream from the condenser and at least a portion of the fluid output from the condenser is provided to the first part of the intermediate heat exchanger. Within the first part, a temperature of the at least a portion of the fluid output from the condenser is reduced. [0005] In addition to one or more of the features described above, or as an alternative, in further embodiments the high temperature glide is at least 2°F. [0006] In addition to one or more of the features described above, or as an alternative, in further embodiments the high temperature glide is at least 5°F. [0007] In addition to one or more of the features described above, or as an alternative, in further embodiments the high temperature glide is at least 10°F. [0008] In addition to one or more of the features described above, or as an alternative, in further embodiments the fluid includes a mixture having two or more distinct fluid components having different boiling temperatures and condensing temperatures. [0009] In addition to one or more of the features described above, or as an alternative, in further embodiments at least one of the two or more distinct fluid components is a refrigerant. [0010] In addition to one or more of the features described above, or as an alternative, in further embodiments the refrigerant is an A2L refrigerant or an A3 refrigerant. [0011] In addition to one or more of the features described above, or as an alternative, in further embodiments the second part of the intermediate heat exchanger is arranged downstream from and in fluid communication with an outlet of the evaporator. [0012] In addition to one or more of the features described above, or as an alternative, in further embodiments within the second part, a temperature of a fluid provided to the second part of the intermediate heat exchanger from the outlet of the evaporator is increased. [0013] In addition to one or more of the features described above, or as an alternative, in further embodiments a first portion of the fluid output from the condenser is provided to the first part of the intermediate heat exchanger and a second portion of the fluid output from the condenser is provided to the second part of the intermediate heat exchanger. [0014] In addition to one or more of the features described above, or as an alternative, in further embodiments comprising another expansion device arranged upstream from and in fluid communication with the second part of the intermediate heat exchanger, wherein the second portion of fluid output from the condenser is provided to the another expansion device. [0015] In addition to one or more of the features described above, or as an alternative, in further embodiments the first part of the intermediate heat exchanger and the another expansion device are arranged in parallel. [0016] In addition to one or more of the features described above, or as an alternative, in further embodiments the first portion of fluid output from the condenser is mixed with the second portion of fluid output from the condenser directly upstream from the compressor. [0017] In addition to one or more of the features described above, or as an alternative, in further embodiments the second portion of fluid output from the condenser is configured to bypass the expansion device and the evaporator. [0018] In addition to one or more of the features described above, or as an alternative, in further embodiments the intermediate heat exchanger is a refrigerant to refrigerant heat exchanger. [0019] In addition to one or more of the features described above, or as an alternative, in further embodiments the intermediate heat exchanger is a liquid suction heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS [0020] The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: [0021] FIG. 1 is a schematic diagram of a basic vapor compression cycle of a heating, ventilation, air conditioning and refrigeration (HVAC&R); [0022] FIG. 2 is an example of a temperature/enthalpy chart of a fluid having a high temperature glide according to an embodiment; [0023] FIG. 3 is a schematic diagram of a vapor compression cycle suitable for use with a fluid having a high temperature glide according to an embodiment; and [0024] FIG.4 is a schematic diagram of another vapor compression cycle suitable for use with a fluid having a high temperature glide according to an embodiment. DETAILED DESCRIPTION [0025] A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. [0026] Referring now to FIG.1, a basic vapor compression or refrigeration cycle 10 of a heating, ventilation, air conditioning and refrigeration (HVAC&R) system is schematically illustrated. Examples of HVAC&R systems include split, packaged, and rooftop systems, for example. A fluid, such as a refrigerant R-410A for example, is configured to circulate through the vapor compression cycle 10 such that the refrigerant R absorbs heat when evaporated at a lower temperature and pressure in heat exchanger 18 and releases heat when condensing at a higher temperature and pressure in heat exchanger 14. Within this cycle 10, the refrigerant R flows in a counterclockwise direction as indicated by the arrows. The compressor 12 receives refrigerant vapor from the evaporator 18 and compresses it to a higher temperature and pressure, with the relatively hot vapor then passing to the condenser 14 where it is cooled and condensed to a liquid state and partially subcools by a heat exchange relationship with a cooling medium such as air or water. The subcooled liquid refrigerant R then passes from the condenser 14 to an expansion device 16, such as an expansion valve, wherein the refrigerant R is expanded to a low temperature two phase liquid/vapor state as it passes to the evaporator 18. The low pressure vapor then returns to the compressor 12 so that the cycle may be repeated. [0027] Various types of refrigerants are available for use in a vapor compression cycle. These refrigerants may include either a single fluid, or alternatively, may include a fluid mixture or blend including two or more distinct fluid components. The distinct components of these refrigerant blends can have different boiling temperatures and condensing temperatures, and can result in a temperature glide as shown in Fig.2. The greater difference in the boiling and condensing temperatures increases the amount of temperature glide. [0028] Temperature glide is defined as the temperature difference between the starting and ending temperature of a refrigerant phase change within a system at a constant pressure. In existing HVAC&R systems, the refrigerant typically used is either an azeotropic refrigerant or a near-azeotropic refrigerant blend. An azeotropic refrigerant is typically a single refrigerant fluid and does not experience a temperature glide and the boiling and condensing temperature of each component are close in temperature. A near-azeotropic refrigerant blend experiences a very small amount of temperature glide as it condenses and evaporates in a vapor compression cycle, such as less than one degree for example. Accordingly, the temperature glide of a near-azeotropic refrigerant blend does not significantly impact the operation of the vapor compression cycle. [0029] In embodiments where the fluid configured to circulate through the vapor compression cycle is a refrigerant mixture or blend having a high temperature glide, the refrigerant blend is considered zeotropic. As used herein, the term “high temperature glide” includes refrigerant blends having a temperature glide of at least two degrees, such as at least three degrees, at least four degrees, at least five degrees, or at least ten degrees for example. In such embodiments, a refrigerant of the refrigerant blend can also be an A2L refrigerant or an A3 refrigerant. In an embodiment, the refrigerant blend includes refrigerant R-454B; however, it should be understood that R-454B is intended as an example, and the zeotropic refrigerant or refrigerant blend disclosed herein is not limited to this specific refrigerant. Although a refrigerant blend is described herein as having a high temperature glide, it should be understood that other suitable refrigerants, fluids, or mixtures thereof that similarly have a high temperature glide are also within the scope of the disclosure. [0030] An example of a temperature enthalpy diagram of a refrigerant mixture or blend having high glide is illustrated in FIG.2. As shown, the temperature glide exists during both condensing and evaporation of the refrigerant mixture. The temperature glide of a zeotropic refrigerant blend negatively affects operation of a basic vapor compression cycle. For example, as a result of the temperature glide, it is difficult to get adequate state point subcooling within a condenser required for proper operation of the downstream expansion valve. Similarly, the temperature glide of a zeotropic refrigerant blend makes it difficult to achieve sufficient superheat required for proper operation of the compressor and control of the expansion valve. [0031] With reference now to FIGS.3 and 4, schematic diagrams of a vapor compression cycle 30 of an HVAC&R system suitable for use with a zeotropic refrigerant blend, shown by RM, are illustrated according to various embodiments. As previously described, the vapor compression cycle 30 includes a compressor 32, a heat rejection heat exchanger or condenser 34, an expansion device 36, and a heat absorption heat exchanger or evaporator 38. As shown in FIG, 3, the vapor compression cycle 30 additionally includes an intermediate heat exchanger 40 configured to further increase the heat transfer of the refrigerant blend RM. In an embodiment, the intermediate heat exchanger 40 is a refrigerant to refrigerant liquid suction heat exchanger configured to use a cold gaseous fluid to subcool the liquid refrigerant blend output from the condenser 32. [0032] In the illustrated, non-limiting embodiment of FIG. 3, the intermediate heat exchanger 40 is positioned within the suction line extending between the evaporator 38 and the compressor 32. Accordingly, the gaseous refrigerant blend output from the evaporator 38 makes a pass through a second part of the intermediate heat exchanger 40 before ultimately being supplied to the compressor 32. In an embodiment, the intermediate heat exchanger 40 is positioned upstream from the thermal expansion device 36 and directly downstream from the condenser 34. The refrigerant blend provided to a first part of the intermediate heat exchanger 40 from the condenser 34 may be a liquid, or alternatively, in some instances may be a two phase mixture of both liquid and gas if adequate subcooling is not possible in the condenser due to the high glide of the refrigerant. [0033] As the condensed refrigerant blend passes through the first part of the intermediate heat exchanger 40, heat transfers from the condensed refrigerant blend to the vaporized or gaseous refrigerant blend output from the evaporator 38. As a result of this heat transfer, the condensed liquid refrigerant blend is further subcooled, such as below the ambient temperature. At the same time, the vaporized refrigerant blend is superheated, thereby allowing the evaporator 38 to run at or near a fully saturated condition, which enhances operation of the evaporator. [0034] In another embodiment, illustrated in FIG.4, the intermediate heat exchanger 40 is fluidly coupled to an outlet of the condenser 32 and is arranged in parallel with another thermal expansion valve 42. A first portion of the refrigerant blend output from the condenser 34, illustrated by RM1, is provided to a first part of the downstream intermediate heat exchanger 40 and a second portion of the refrigerant blend output from the condenser 34, illustrated by RM2, is provided to the expansion device 42. The two phase flow of refrigerant blend output from the expansion device 42 is then provided to a second part of the intermediate heat exchanger 40. Within the intermediate heat exchanger 40, heat transfers from the first portion of the refrigerant blend RM1 to the at least partially vaporized or gaseous second portion of the refrigerant blend RM2 output from the expansion valve 42. As a result of this heat transfer, the first portion of the refrigerant blend RM1 is further subcooled, such as below the ambient temperature for example, and the second portion of the refrigerant blend RM2 is superheated. It should be understood that each of the first and second parts of the intermediate heat exchanger 40 illustrated and described herein may include a single pass, or alternatively, may include multiple passes to achieve the desired amount of heat transfer. [0035] The subcooled first portion of the refrigerant blend RM1 may then be provided to one or more downstream components, such as the expansion device 36, evaporator 38, and/or compressor 32 for example. The second portion of the refrigerant blend RM2 output from the intermediate heat exchanger 40 is rejoined with the first portion of the refrigerant blend RM1 when the first portion of the refrigerant blend RM1 has a generally gaseous configuration. In an embodiment, the first portion and the second portion of the refrigerant blend RM1, RM2 are joined directly upstream from the inlet of the compressor 32. The refrigerant can then be sent to the compressor 32 suction or it can be introduced into an economizer port of the compressor 32 which is part way thru the compression process. [0036] A vapor compression cycle 30 as illustrated and described herein has enhanced performance when used with a refrigerant blend having a high temperature glide compared to a basic vapor compression system. Further, in embodiments where the HVAC&R system is a split system having long fluid lines, the subcooling of the refrigerant within the intermediate heat exchanger 40 may additionally reduce the refrigerant charge. [0037] The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. [0038] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. [0039] While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.

Claims

What is claimed is: 1. A vapor compression cycle comprising: a compressor, condenser, expansion device, and evaporator fluidly connected via one or more fluid conduits; a fluid circulating within the one of more fluid conduits, wherein the fluid has a high temperature glide; and an intermediate heat exchanger having a first part including at least one pass there through and a second part including at least one pass there through, wherein the first part is arranged downstream from the condenser and at least a portion of the fluid output from the condenser is provided to the first part of the intermediate heat exchanger, wherein within the first part, a temperature of the at least a portion of the fluid output from the condenser is reduced. 2. The vapor compression cycle of claim 1, wherein the high temperature glide is at least 2°F. 3. The vapor compression cycle of claim 1, wherein the high temperature glide is at least 5°F. 4. The vapor compression cycle of claim 1, wherein the high temperature glide is at least 10°F. 5. The vapor compression cycle of claim 1, wherein the fluid includes a mixture having two or more distinct fluid components having different boiling temperatures and condensing temperatures. 6. The vapor compression cycle of claim 5, wherein at least one of the two or more distinct fluid components is a refrigerant. 7. The vapor compression cycle of claim 5, wherein the refrigerant is an A2L refrigerant or an A3 refrigerant. 8. The vapor compression cycle of claim 1, wherein the second part of the intermediate heat exchanger is arranged downstream from and in fluid communication with an outlet of the evaporator. 9. The vapor compression cycle of claim 8, wherein within the second part, a temperature of a fluid provided to the second part of the intermediate heat exchanger from the outlet of the evaporator is increased. 10. The vapor compression cycle of claim 1, wherein a first portion of the fluid output from the condenser is provided to the first part of the intermediate heat exchanger and a second portion of the fluid output from the condenser is provided to the second part of the intermediate heat exchanger. 11. The vapor compression cycle of claim 10, further comprising another expansion device arranged upstream from and in fluid communication with the second part of the intermediate heat exchanger, wherein the second portion of fluid output from the condenser is provided to the another expansion device. 12. The vapor compression cycle of claim 11, wherein the first part of the intermediate heat exchanger and the another expansion device are arranged in parallel. 13. The vapor compression cycle of claim 10, wherein the first portion of fluid output from the condenser is mixed with the second portion of fluid output from the condenser directly upstream from the compressor. 14. The vapor compression cycle of claim 10, wherein the second portion of fluid output from the condenser is configured to bypass the expansion device and the evaporator. 15. The vapor compression cycle of claim 10, wherein the intermediate heat exchanger is a refrigerant to refrigerant heat exchanger. 16. The vapor compression cycle of claim 10, wherein the intermediate heat exchanger is a liquid suction heat exchanger.