US20070039351A1

US20070039351A1 - Refrigeration system having an integrated bypass system

Info

Publication number: US20070039351A1
Application number: US10/547,043
Authority: US
Inventors: Cheolho Bai
Original assignee: Vortex Aircon Inc; VAI Holdings LLC
Current assignee: VAI Holdings LLC
Priority date: 2003-02-28
Filing date: 2004-02-25
Publication date: 2007-02-22
Also published as: KR20050121201A; EP1597526A2; WO2004079279A3; JP2006519350A; KR100764926B1; CN1764810A; WO2004079279A2

Abstract

A heat transfer system usable as an air conditioner, a heat pumpt or the like includes a compressor, a condenser, a main expansion device and an evaporator connected in a closed circuit through which a refrigerant is circulated, and a bypass device in which subcooling is performed rather than in the downstream portion of the condenser, as is conventional. The subcooling device is comprised of a unitary integrated structure having an inner tube connectable in a main refrigerant flow path at the outlet of a condenser, a concentric outer tube having end portions sealed to the outside of the inner tube thereby providing a chamber surrounding the inner tube, an inlet orifice connecting the inner tube to an upstream end of the outer tube that allows a portion of the refrigerant flowing in the inner tube to be diverted to the chamber, at a reduced temperature and pressure, an outlet orifice at the downstream end of the outer tube; and a return line in communication with the outlet orifice, and connectable to the main refrigerant path, whereby the diverted refrigerant can flow through the chamber, provide subcooling for refrigerant flowing in the inner tube, and then be returned to the main refrigerant flow path. The outlet orifice may also be sized to cause a pressure drop in the refrigerant as it exits the chamber, thereby accommodating a pressure differential between the refrigerant in the bypass device and the main refrigerant path at the point of reentry.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application is a 35 U.S.C. § 371 national phase conversion of PCT/US2004/005721 filed 25 Feb. 2004, which claims priority to U.S. Provisional Application Ser. No. 60/451,356, filed 28 Feb. 2003, incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to a high efficiency heat transfer system and more specifically, to such a system utilizing a bypass path to optimize the sizes of components, including the condenser, compressor and evaporator, thereby increasing overall system efficiency. For convenience, the invention will be described in the context of a “refrigeration system” but it is to be understood that the invention is directly applicable to purely refrigeration systems and also to similar systems used as heat pumps.

BACKGROUND OF THE INVENTION

FIG. 1 is a block diagram of a conventional refrigeration system, generally denoted at 10. The system includes a compressor 12, a condenser 14, an expansion device 16 and an evaporator 18. These components are connected together typically via copper tubing such as indicated at 19 to form a closed loop system through which a refrigerant such as R-12, R-22, R-134a, R-407c, R-410a, ammonia, carbon dioxide or natural gas is cycled.
The main steps in the refrigeration cycle are compression of the refrigerant by compressor 12, heat extraction from the refrigerant to the environment by condenser 14, throttling of the refrigerant in the expansion device 16, and heat absorption by the refrigerant from the space being cooled in evaporator 18. This process, sometimes referred to as a vapor-compression refrigeration cycle, is used in air-conditioning systems, which cool and dehumidify air in a living space, in a moving vehicle (e.g., automobile, airplane, train, etc.), in refrigeration equipment, in heat pumps and in other applications. As will be appreciated, the system configuration of FIG. 1 is generally representative of all such systems.
In the condenser 14, heat is removed from the refrigerant so that the superheated refrigerant vapor from the compressor 12 becomes liquid refrigerant by the time it reaches the exit of the condenser. In FIG. 1, the condenser 14 is divided into two parts, 14 a and 14 b. The first portion of the condenser identified as 14 b is where superheated refrigerant vapor becomes saturated vapor, a process called desuperheating, and the saturated vapor undergoes phase change from vapor to liquid refrigerant. The second portion of the condenser identified as 14 a is where the liquid refrigerant is further cooled below the saturation temperature at the condenser pressure, a process known as subcooling.
In my Application Ser. No. PCT/US03/36424, filed Nov. 11, 2003, entitled REFRIGERATION SYSTEM WITH BYPASS SUBCOOLING AND COMPONENT SIZE DE-OPTIMIZATION (the '424 application), I disclose a refrigeration system in which the subcooling is performed in a secondary refrigerant path which partially bypasses the main refrigerant path, rather than in the condenser.
A system of this type is shown in FIG. 2. Here, the main refrigeration path is the same as the system shown in FIG. 1, but there is also provided a bypass line 27 into which a portion of the refrigrant from the main refrigeration path is diverted. This includes a secondary expansion device 23, and a heat exchanger 22 thermally coupled to the main refrigerant flow path between the condenser 14 and the main expansion device 16. As the diverted portion of the refrigerant exiting condenser 14 passes through secondary expansion device 23, its pressure and temperature are lowered substantially below the condenser outlet pressure and temperature.
The cold refrigerant mixture exiting secondary expansion device 23 then flows through heat exchanger 22, where heat is extracted from the liquid refrigerant flowing from condenser 14, producing additional subcooling in the liquid refrigerant. The additional subcooling produced from the bypass technology makes the subcooling process in the condenser unnecessary. This is indicted in FIG. 2 by a smaller condenser in which the subcooling section 14 a has been eliminated, and is shown in outline.
Because the refrigerant pressure in bypass line 27 at the outlet of the heat exchanger is greater than the pressure at the outlet of evaporator 18, a pressure differential accommodating device (PDAD) 38 is used to couple the outlet of the bypass line to the primary refrigerant line. The pressure differential accommodating device can be either a vacuum generating device or a pressure-reducing device, as disclosed in the '424 application.
Other information concerning the implications and benefits flowing from the use of a bypass path for subcooling is also disclosed in the '424 application, and the entire contents of that application are hereby incorporated herein by reference, as if fully set forth.
Although significant improvements over conventional systems in which subcooling takes place in the condenser are achieved using bypass subcooling, the need remains to find ways to further reduce cost and size, especially in small systems. The present invention addresses this continuing need.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide improvements in bypass subcooling for refrigeration systems, heat pumps and the like.
It is another object of the invention to provide a subcooling bypass device employing components which can be manufactured less expensively than conventional components.
It is also an object of the invention to provide a subcooling bypass line employing components which can be manufactured more compactly than conventional components.
An additional object of the invention is to provide an improved component which can be employed to provide bypass subcooling in a refrigeration or heat pump system.
Yet a further object of the invention is to provide such an improved component by which bypass subcooling can be provided less expensively than with conventional components.
Another object of the invention is to provide such an improved component which will permit refrigeration in a heat pump system employing bypass subcooling to be more compact than if conventional components are employed for the bypass path.
According to a first aspect of the invention, subcooling is provided by a bypass device comprising means for diverting a portion of the liquid refrigerant exiting the condenser in the main refrigerant path to the bypass path, expansion means for reducing the pressure and temperature of the diverted refrigerant, heat exchange means thermally coupling a refrigerant flow path containing the diverted refrigerant at the reduced pressure and temperature to a portion of the main refrigerant path downstream of the condenser to extract sufficient heat from the refrigerant therein to provide subcooling, and outlet means connected to the heat exchange means for returning the diverted refrigerant to the main refrigerant path downstream of the heat exchanger means.
According to the first aspect of the invention, the outlet means may comprise a pressure differential accommodating means.
Further according to the first aspect of the invention, all of the stated functions of the bypass line are performed by a single mechanical component.
According to a second aspect of the invention, subcooling is provided by an integrated structure including a first orifice through which a portion of the liquid refrigerant exiting the condenser is diverted from the main refrigerant path to a bypass path, and by which the pressure and temperature thereof are reduced, a heat exchanger including a first flow path, the upstream end of which is in communication with the aperture, and which is thermally coupled with a portion of main refrigerant flow path downstream of the condenser whereby heat can be extracted from the refrigerant exiting the condenser to provide subcooling, and a second orifice in communication with a downstream end of the first flow path which returns the diverted refrigerant to the main refrigerant path.
Further according to the second aspect of the invention, the second aperture may comprise a pressure differential accommodating device to accommodate differences in pressure between the refrigerant in the main flow path and the bypass path.
Also according to the second aspect of the invention, all of the stated functions of the bypass line are performed by a single mechanical component.
According to a third aspect of the invention, there is provided a bypass subcooling component for a refrigeration or heat pump system which performs, in a single integrated structure, the functions of a diverter for a portion of the refrigerant exiting a condenser, an expansion device for the diverted refrigerant thereby to reduce the temperature thereof significantly relative to the temperature of the refrigerant exiting the condenser, a heat exchanger that employs the cooled diverted refrigerant to subcool the refrigerant flowing from the condenser to the main expansion device, and a coupling device for returning the diverted refrigerant to the main refrigerant path after it has been employed for subcooling.
Further according to the third aspect of the invention, the coupling device may also function as differential pressure accommodating device.
According to a fourth aspect of the invention, the subcooling component may be comprised of first and second concentric tubes. The inner tube is designed to be coupled to the outlet of the condenser, and to serve as part of the main refrigerant flow path. A first orifice is provided between the inner and outer tubes at the upstream end of the outer tube. This functions as an expansion device to divert a portion of the refrigerant exiting the condenser into the bypass path, and to cool the diverted refrigerant. As the cooled refrigerant flows through the outer tube, it extracts heat from the refrigerant flowing through the inner tube, thereby providing subcooling for the refrigerant in the main flow path. A second orifice at the downstream end of the outer tube couples the bypass path to a return tube by which the diverted refrigerant can reenter the main flow path downstream of the evaporator. By proper selection of the size of the second orifice, a pressure differential between the main flow path and the bypass flow path can be accommodated.
The integrated structure described greatly simplifies manufacturing and assembly of the bypass path, and thus can yield significant cost reduction. In addition, the ability to employ a first small orifice between the inner and outer heat exchanger tubes, instead of a separate secondary expansion device, and a second small hole the wall of the outer heat exchanger tube instead of a separate PDAD can yield substantial reduction in the size of the subcooling device. This is particularly beneficial for small air-conditioning or heat pump systems.
According to a fifth aspect of the invention, the integrated subcooling device described herein may be used in the various configurations described in the '424 application. It may also find utility in other aspects of modern heat transfer technology, such as disclosed in my U.S. patent application Ser. No. 10/253,000 filed Sep. 23, 2002, and entitled REFRIGERATION SYSTEM WITH DESUPERHEATING BYPASS, the contents of which are hereby incorporated by reference herein as if fully set forth.
The above-stated and other objects of this invention, as well as the various features thereof will be fully appreciated from the following description and the accompanying drawings.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 shows a block diagram of a conventional refrigeration system.
FIG. 2 shows a block diagram of a refrigeration system which employs bypass subcooling.
FIG. 3 shows a schematic diagram illustrating the principles of the present invention according to a first embodiment in which the diverted refrigerant flows through the heat exchanger in the same direction as the main refrigerant flow.
FIG. 4 shows a block diagram of an embodiment of the present invention similar to that of FIG. 3 but which provides accommodation for a pressure differential between main refrigerant path and the bypass path.
FIG. 5 shows a schematic diagram illustrating the principles of the present invention according to a second embodiment in which the diverted refrigerant flows through the heat exchanger in the opposite direction to the main refrigerant flow.
FIG. 6 shows a block diagram of a refrigeration system similar to that of FIG. 2 employing a bypass subcooling device as illustrated in FIG. 5.
Throughout the drawings, like parts are given the same reference numerals.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of this disclosure, FIG. 2 may be considered representative of the types of refrigeration systems and heat pumps employing bypass subcooling as disclosed in the '424 application. According to this invention, the components which comprise bypass path 27 are replaced by an integrated structure which performs all the functions of the replaced components. One such structure is illustrated in FIG. 3.
Here, the subcooler, generally designated at 40, is comprised of an inner tube 42 and a concentric outer tube 44. Inner tube 42 is connected at its upstream end 46 to the outlet side of condenser 14 (see FIG. 2), and at its downstream end 48 to the inlet of main expansion device 16. Thus, tube 42 replaces the conduit for the main refrigerant flow through the bypass heat exchanger 22.
Referring again to FIG. 3, outer tube 44 has closed ends 52 and 54 with respective openings 56 and 58 that receive inner tube 42. Openings 56 and 58 are suitably sealed to the respective ends 46 and 48 of inner tube 42 to prevent refrigerant leakage, as described below. The structure described thus provides a leak-proof chamber 60 surrounding inner tube 42.
Communication between the interior 62 of inner tube 42 and chamber 60 is provided by a small orifice 64 at the upstream end 46 of inner tube 42. Orifice 64 is sized to serve as an expansion orifice for a portion of the refrigerant exiting condenser 14 as it flows into inner tube 42. A second orifice 66 is provided at the downstream end of outer tube 44 in communication with an outlet tube 68. Thus, again referring to FIG. 2, chamber 60 replaces the conduit for the coolant flow through the bypass heat exchanger 22.
Referring still to FIG. 2, it will be recalled that in the illustrated system, there is a pressure differential between the refrigerant exiting the heat exchanger 22 in the bypass path, and the refrigerant exiting evaporator 18. PDAD 38 is therefore employed to permit the diverted refrigerant in bypass line 27 to be combined with the refrigerant exiting the evaporator for return to compressor 12. The '424 application describes several possible constructions for PDAD 38.
According to the present invention, however, it is possible to integrate the PDAD function into the bypass subcooling device itself, as illustrated in FIG. 4. Here, discharge orifice 70 is sized to produce a pressure drop as the refrigerant exiting chamber 60 flows into return line 68. The size of discharge orifice 70 is selected so that the refrigerant pressure in return line 68 is substantially the same as that of the refrigerant exiting evaporator 18 (see FIG. 2). Thus, discharge orifice 70 may be employed to provide the function of PDAD 38.
In FIGS. 3 and 4, the inlet orifices 64 for chambers 60 are located at the upstream ends of the respective inner tubes 42. Similarly, the outlet orifices 66 and 70 for chamber 60 are at the downstream ends of inner tubes 42. As a consequence, there is parallel flow of the refrigerants in the heat exchanger, i.e., the refrigerant flow in tube 42 and chamber 60 are in the same direction.
In the embodiment of FIG. 5, however, a bypass subcooling device 40 a is provided having an inlet orifice 80 for chamber 82 located at the downstream end 88 of inner tubes 84, and an outlet orifice 86 at the upstream end 90 of inner tube 84. Thus, for the embodiment of FIG. 5, counter-flow is provided in the heat exchanger, i.e., the refrigerant flow in tube 84 and chamber 82 are in opposite directions. As in the embodiment of FIG. 4, by proper sizing of outlet orifice 86, the function of PDAD 38 can be provided.
FIG. 6 illustrates the use of a bypass subcooling device such as illustrated in FIG. 5 in a system such as illustrated in FIG. 2. Here, the inlet end 90 of inner tube 84 is connected to the outlet of condenser 14 b, and the outlet end 88 of inner tube 84 is connected to the inlet of expansion device 16. The downstream end 92 of outer heat exchange chamber 82 is connected through discharge orifice 80 to return line 96 which is suitably coupled to the main flow path at the outlet end of evaporator 18 to return the diverted refrigerant to the inlet of compressor 12.
In describing the invention, specific terminology has been employed for the sake of clarity. However, the invention is not intended to be limited to the specific descriptive terms, and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.
Similarly, the embodiments described and illustrated are also intended to be exemplary, and various changes and modifications, and other embodiments within the scope of the invention will be apparent to those skilled in the art in light of the disclosure. The scope of the invention is therefore intended to be defined and limited only by the appended claims, and not by the description herein.

Claims

1. A subcooling device for a heat transfer system, the subcooling device being in the form of a unitary integrated structure which includes:

a main refrigerant passage; a primary inlet by which the main refrigerant passage may be connected to an outlet of a condenser in a primary refrigeration path of a refrigeration system;

a primary outlet by which the main refrigerant passage may be connected to an inlet of an expansion device in the primary refrigeration path;

a bypass passage;

a secondary inlet operative to divert a portion of the refrigerant entering the subcooling device from the condenser to the bypass passage and to reduce the pressure and temperature of the diverted refrigerant; and

a secondary outlet by which the bypass passage may be connected to the primary refrigeration path downstream of the evaporator,

the bypass passage being thermally coupled to the main refrigerant passage to form a heat exchanger operable to transfer heat from refrigerant in the main refrigerant passage to refrigerant in the bypass passage.

2. A subcooling device according to claim 1, wherein the secondary outlet further provides, as part of the integrated structure thereof, pressure differential accommodation for refrigerant in the bypass passage relative to refrigerant in the primary refrigeration path.

3. A subcooling device according to claim 1, wherein: the main refrigerant passage is comprised of a first tube connectable between the outlet of the condenser and the inlet of the expansion device;

the bypass passage is comprised of a second tube which surrounds the first tube and has end portions sealed to the outside of the first tube thereby forming a chamber surrounding the first tube; and

the secondary inlet is comprised of an orifice connecting the first tube to an upstream end of the second tube,

whereby, when the refrigerant flows through the first and second tubes, heat is absorbed by the relatively cooler refrigerant in the second tube from the relatively warmer refrigerant in the first tube.

4. A subcooling device as described in claim 3, wherein the secondary outlet is comprised of an orifice at the downstream end of the second tube connectable to the main refrigerant path.

5. A subcooling device as described in claim 4, wherein the secondary outlet provides a pressure drop for the refrigerant flowing therethrough.

6. A subcooling device as described in claim 4, wherein the secondary inlet is at an upstream end of the first tube, and the secondary outlet is at a downstream end of the first tube.

7. A subcooling device as described in claim 4, wherein the secondary inlet is at a downstream end of the first tube, and the secondary outlet is at an upstream end of the first tube.

8. A heat transfer system comprising:

a primary refrigeration path including a compressor, a condenser, an expansion device, and an evaporator, connected together to form a closed loop system with a refrigerant circulating therein; and

a subcooling device according to claim 1, wherein:

the primary inlet is connected to an outlet of the condenser;

the primary outlet is connected to the inlet of the primary expansion device; and

the secondary outlet is connected to return the diverted refrigerant to the primary refrigeration path downstream of the evaporator.

9. A subcooling device for a heat transfer system comprising a unitary structure including:

inlet means for diverting a portion of a liquid refrigerant exiting a condenser means in a main refrigeration path of the refrigeration system;

expansion means for reducing the pressure and temperature of the diverted refrigerant,

heat exchange means thermally coupling the diverted refrigerant at the reduced pressure and temperature to a portion of the main refrigeration path downstream of the condenser to extract sufficient heat from the refrigerant therein sufficient to provide subcooling; and

outlet means connected to the heat exchange means for returning the diverted refrigerant to the main refrigeration path downstream of an evaporator means in the main refrigeration path.

10. A device according to claim 9, wherein the outlet means is operative to reduce the pressure of the refrigerant as it passes therethrough.

11. A heat transfer system comprising:

a primary refrigeration path including compressor means, condenser means, expansion means, and evaporator means, connected together to form a closed loop system with a refrigerant circulating therein; and

a subcooling device according to claim 9 wherein:

the inlet means is connected to an outlet of the condenser means; and

the outlet means is connected to return the diverted refrigerant to the primary refrigeration path downstream of the evaporator means.