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 
       [0001]    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 
       [0002]    The invention relates to vapor compression systems and, more particularly, to a heat exchanger configuration for such a system. 
         [0003]    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. 
         [0004]    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. 
         [0005]    Other objects and advantages will appear herein below. 
       SUMMARY OF THE INVENTION 
       [0006]    According to the present invention, the foregoing objects and advantages have been attained. 
         [0007]    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 
         [0008]    A detailed description of preferred embodiments of the invention follows with reference to the attached drawings, wherein: 
           [0009]      FIG. 1  is a perspective view of a system having a multi-part heat exchanger according to the invention; 
           [0010]      FIG. 2  is a schematic illustration of a multi-part heat exchanger system according to the invention; and 
           [0011]      FIG. 3  illustrates the refrigerant and air flow in a system according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    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. 
         [0013]    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. 
         [0014]      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. 
         [0015]    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. 
         [0016]    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 . 
         [0017]    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. 
         [0018]    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 CO 2 . 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. 
         [0019]    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. 
         [0020]    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. 
         [0021]      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 . 
         [0022]    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. 
         [0023]    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. 
         [0024]      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 CO 2 ), 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. 
         [0025]    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. 
         [0026]    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. 
         [0027]    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.