US20080184731A1

US20080184731A1 - Multi-Part Heat Exchanger

Info

Publication number: US20080184731A1
Application number: US11/908,418
Authority: US
Inventors: Tobias H. Sienel; Yu Chen; Parmesh Verma; Hans-Joachim Huff
Original assignee: Carrier Comercial Refrigeration Inc
Current assignee: Taylor Commercial FoodService LLC
Priority date: 2005-03-18
Filing date: 2005-12-30
Publication date: 2008-08-07
Also published as: JP2008533425A; JP4705157B2; CN100575813C; CN101175952A; WO2006101563A3; EP1872068A4; EP1872068B1; EP1872068A2; ES2580080T3; WO2006101563A2; HK1120103A1

Abstract

A refrigeration system includes a compressor for driving a refrigerant along a flow path in at least a first mode of system operation; a first heat exchanger along the flow path downstream of the compressor in the first mode; a second heat exchanger along the flow path upstream of the compressor in the first mode; and a pressure regulator or expansion device in the flow path downstream of the first heat exchanger and upstream of the second heat exchanger in the first mode, wherein the first heat exchanger comprises a plurality of heat exchanger components arranged along a flow path of heat exchange fluid for the first heat exchanger. The heat exchanger components can be positioned in smaller available areas within the unit and thereby use space more efficiently.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of earlier filed Provisional Application Ser. No. 60/663,917 filed Mar. 18, 2005. Further, copending application docket 05-258-WO, entitled HIGH SIDE PRESSURE REGULATION FOR TRANSCRITICAL VAPOR COMPRESSION SYSTEM and filed on even date herewith, and the aforesaid Provisional Application Ser. No. 60/663,917, disclose prior art and inventive cooler systems. The disclosure of said applications is incorporated by reference herein as if set forth at length.

BACKGROUND OF THE INVENTION

The invention relates to vapor compression systems and, more particularly, to a heat exchanger configuration for such a system.
In many vapor compression systems, the heat exchanger placement is very much constrained by space. For these applications, the efficiency of the system is often low in comparison to a system with a properly sized heat exchanger due to the large temperature difference between the air and the refrigerant in the heat exchangers.
The need exists for more efficient heat exchange despite space requirements of the system, and it is an object of the invention to provide such a system.
Other objects and advantages will appear herein below.

SUMMARY OF THE INVENTION

According to the present invention, the foregoing objects and advantages have been attained.
According to the invention, a refrigeration system is provided which includes a compressor for driving a refrigerant along a flow path in at least a first mode of system operation; a first heat exchanger along the flow path downstream of the compressor in the first mode; a second heat exchanger along the flow path upstream of the compressor in the first mode; and an expansion device in the flow path downstream of the first heat exchanger and upstream of the second heat exchanger in the first mode, wherein the first heat exchanger comprises a plurality of heat exchanger components arranged along a flow path of heat exchange fluid for the first heat exchanger. The heat exchanger components can be positioned in smaller available areas within the unit and thereby use space more efficiently. Further, flow to these heat exchange components can be routed so as to provide counter flow of the heat exchange fluid, for example air, with the refrigerant. In addition, the system of the present invention can be at least partially if not entirely incorporated into a cassette which can be readily interchanged within the existing housing or case of a refrigerator unit to allow replacement of the cassette when needed without replacing the entire unit.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of preferred embodiments of the invention follows with reference to the attached drawings, wherein:

FIG. 1 is a perspective view of a system having a multi-part heat exchanger according to the invention;

FIG. 2 is a schematic illustration of a multi-part heat exchanger system according to the invention; and

FIG. 3 illustrates the refrigerant and air flow in a system according to the invention.

DETAILED DESCRIPTION

The invention relates to a vapor compression system of a refrigerator unit and, more particularly, to the arrangement of a heat exchanger in a vapor compression system, preferably in a transcritical vapor compression system.
As set forth above, the greater the area of heat exchanger contact with heat exchange medium such as air, the greater the efficiency in operation of a vapor compression system. In accordance with the present invention, greater contact area between the heat exchanger and heat exchange medium is obtained by utilizing all potentially available spaces within a particular vapor compression system to house additional components of a heat exchanger, such that the heat exchanger is implemented in a series or plurality of heat exchange components. In this manner, small available spaces are nevertheless utilized to increase heat exchange efficiency and, therefore, efficiency of the overall system.
FIG. 1 shows a system in accordance with the present invention. FIG. 1 shows system 10 which, in this particular embodiment, is the vapor compression system for a bottle cooler refrigeration assembly. FIG. 1 shows the lower portion of such an assembly, including a housing 12 containing a vapor compression system. Reference is made to FIGS. 1-3 for further discussion of the vapor compression system, which includes a compressor 14, a downstream heat exchanger 16, an expansion device 18 and an evaporator 20. Compressor 14 is operative to drive a refrigerant along refrigerant lines (FIG. 3) first to heat exchanger 16, then to expansion device 18, and then to evaporator 20. Refrigerant flows from evaporator 20 back to compressor 14 to complete the circuit.
In accordance with the present invention, first heat exchanger 16 is provided having a first heat exchange component 22 and a second heat exchange component 24. These components are positioned within housing 12 to take advantage of the spaces available such that high amounts of heat exchange can be accomplished with relatively small available spaces.
As illustrated in the drawings, housing 12 defines a flow path for heat exchange medium, for example air, to enter into heat exchange relationship with first heat exchanger 16. An upper portion of housing 12 also defines a flow path for air from within the refrigerated space (not shown, but located above housing 12 and supplied with air cooled by arrows 27) to be treated with second heat exchanger 20.
In connection with any heat exchange system, and particularly in connection with vapor compression systems which form the preferred embodiment of the present invention, extended area of heat exchange contact between the heat exchange medium and the refrigerant-carrying heat exchangers is critical to obtaining good efficiency of the system. It has also been found that such systems operate most efficiently with counter-current flow of refrigerant verses heat exchange medium. That is, referring to FIG. 3, if heat exchange medium or air is flowing in the direction of arrows 26, it is preferred that refrigerant flow through heat exchanger 16 be in the flow direction shown such that the direction of flow of refrigerant is counter to that of the flow of heat exchange medium. Referring further to FIGS. 1-3, it should readily apparent that first and second components 22, 24 of first heat exchanger 16 can and most likely will be different in size and/or shape so that these components can advantageously take advantage of the available space within a particular device. For example, in the embodiment shown, first component 22 has a relatively larger area in a transverse plane with respect to the flow, and is relatively thin from front to back. This is because first component 22 in this embodiment is sized to fit within a relatively narrow (from front to back) space toward the open front of housing 12. A second space within housing 12 in this embodiment is available beneath a wall 28 which separates one portion of housing 12 for treating the first flow of air 26 from a second portion of housing 12 for treating the second portion of air 27. This wall 28 extends downwardly relative to the outer contour of housing 12, and results in a restriction in flow area as air flows from the inlet end 30 to the outlet end 32 of housing 12. This zone of decreased cross sectional flow area results in an increase in velocity of the air flowing through this zone. An increased velocity flow has been found to provide improved efficiency heat exchange in heat exchangers such as that of the present invention. According to the invention, it is preferred to position second component 24 of first heat exchanger 16 within this zone of decreased cross sectional flow area so as to take advantage of the increased flow of velocity in this zone. Further, the shape of this zone dictates a different configuration for second component 24 as compared to first component 22. Specifically, this zone has a substantially short height and yet extends much further from the inlet side toward the outlet side as compared to the space for accommodating first component 22. Thus, second component 24 is advantageously shaped and adapted to fit properly within this space, thereby providing maximum possible heat exchange area and further taking advantage of the increased flow velocity of air through that zone.
As set forth above, one preferred implementation of the vapor compression system in accordance with the present invention is a transcritical vapor compression system. Such a system, as is known to a person of skill in the art, operates upon a refrigerant which does not condense in the first heat exchanger. One example of a refrigerant of a transcritical vapor compression system is CO₂. Of course, other refrigerants could be used well within the scope of the present invention to provide suitable vapor compression systems which would benefit from the heat exchanger arrangement of the present invention.
Expansion device 18 can be any suitable expansion device for decreasing the pressure of refrigerant passing there through as is known to a person of skill in the art. Various known expansion devices could be utilized for this purpose. In accordance with a preferred aspect of the present invention, a pressure regulator such as that disclosed in a commonly-owned and simultaneously filed PCT Patent Application bearing attorney docket number 05-258-WO and having the title HIGH SIDE PRESSURE REGULATION FOR TRANSCRITICAL VAPOR COMPRESSION-SYSTEM, is a particularly desirable type of expansion device for use in connection with the present invention. As used herein, the term expansion device is considered to include such a pressure regulator.
Second heat exchanger 20, which performs the function of an evaporator, is shown as a single heat exchanger in the drawings. It should be appreciated that second heat exchanger 20 could also be provided in a plurality of components, as well, in the event that space for treatment of flow of air from the refrigerated space is particularly small and/or irregularly shaped.
FIG. 3 shows refrigerant lines connecting from first heat exchanger 16 to expansion device 18 and then to second heat exchanger or evaporator 20. Refrigerant flows from evaporator 20 back to the suction inlet of compressor 14.
It should be appreciated that the present invention provides for increased heat exchange efficiency due to increase in area of contact between the heat exchanger and the heat exchange medium. It should further be appreciated that the system of the present invention provides for enhanced utilization of space available for heat exchange, thereby providing more efficient operation of a vapor compression system as desired in accordance with the present invention.
In some systems it is possible to use a heat exchanger divided into multiple parts and arranged where space is available to increase the overall heat transfer area of the heat exchanger. This disclosure makes use of this with the addition of arranging the multiple parts of the heat exchanger in such a way that the effective refrigerant flows and air (or other heat transfer mediums) flows are opposite to each other.
FIG. 2 shows an example with a two part heat exchanger. In this case the refrigerant flow would be circuited first through component 24 and then through component 22 if the air flow was directed from front to back. The refrigerant flow would be circuited first through component 22 and then through component 24 if the air flow was from back to front. This concept is especially useful for transcritical vapor compression systems (such as using CO₂), where it is critically important for efficiency that the temperature of refrigerant leaving the heat rejecting heat exchanger be as close as possible to the heat sink fluid (typically air) entering the heat exchanger. The individual heat exchanger segments or components could also be circuited to be as counterflow as possible to further enhance this effect.
In FIG. 2, only one fan 34 is used to move the heat transfer fluid (air) through all of the heat exchanger components 22, 24. This is an additional benefit to cost and energy efficiency, although this is not a necessary embodiment.
The segments or components of the heat exchanger could be manufactured and shipped as one piece, or separately manufactured and connected during the unit assembly process. This type of a heat exchanger is particularly useful for applications where a low number of fins are used on the heat exchanger for reasons of fouling. The reduction in fins due to fouling concerns is offset by the additional heat exchanger tube or channel surface area. This heat exchanger could be a round tube plate fin, wire on tube, microchannel, or any other configuration.
One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, when implemented as a remanufacturing of an existing system or reengineering of an existing system configuration, details of the existing configuration may influence details of the implementation. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A refrigeration system comprising:

a compressor for driving a refrigerant along a flow path in at least a first mode of system operation;

a first heat exchanger along the flow path downstream of the compressor in the first mode;

a second heat exchanger along the flow path upstream of the compressor in the first mode; and

an expansion device in the flow path downstream of the first heat exchanger and upstream of the second heat exchanger in the first mode,

wherein the first heat exchanger comprises a plurality of heat exchanger components arranged along a flow path of heat exchange fluid for the first heat exchanger.

2. The system of claim 1 wherein the flow path of the heat exchange fluid is counter to the flow of refrigerant in the heat exchange components.

3. The system of claim 1 wherein the second heat exchanger also comprises a plurality of heat exchange components.

4. The system of claim 1 wherein the first heat exchanger is mounted within a housing having separate and discrete available spaces, and wherein the heat exchanger components are positioned in the spaces.

5. The system of claim 1 further comprising a refrigerator housing defining a cassette receiving area, and wherein the heat exchanger components are mounted within a cassette adapted to be inserted into the receiving area.

6. The system of claim 1, wherein the heat exchanger components include at least a first component and a second component, and wherein the first component has a different shape than the second component.

7. The system of claim 1, wherein the first heat exchanger is mounted within a housing defining a flow path for heat exchanger medium to flow past the first heat exchanger, and wherein the flow path has a cross sectional flow area and a decreased flow area zone along the path, and wherein at least one of the components is positioned at the decreased flow area zone.

8. The system of claim 1, wherein the refrigerant comprises, in major mass part, CO₂; and the first and second heat exchangers are refrigerant-air heat exchangers.

9. The system of claim 1, wherein the system contains a refrigerant and the refrigerant is a transcritical vapor compression.

10. A beverage cooling device comprising the system of claim 1.