Abstract:
A storage evaporator for an air conditioning system in a vehicle is provided that includes phase change material-containing tubes arranged side-by-side in contact with refrigerant-containing tubes. The storage evaporator includes an upper coolant tank, a lower coolant tank, refrigerant-containing tubes fluidly connecting said tanks; and phase change material-containing tubes provided in contact with said refrigerant tubes. The refrigerant tubes have flat sides and the phase change material-containing tubes have flat sides. The flat sides of the refrigerant tubes are attached to the flat sides of said phase change material-containing tubes. The phase change material may be any of several materials and may an eutectic, a salt hydrate, and an organic material. In operation, cold energy is stored in the phase change material when the air conditioning compressor is in its “On” position. This cold energy is released from the phase change material when the compressor is in its “Off” position.

Description:
TECHNICAL FIELD 
       [0001]    The disclosed inventive concept relates to air conditioning systems for vehicles that utilize an evaporator. More particularly, the disclosed inventive concept relates to an evaporator for an air conditioning system for a vehicle that has air conditioning tubes that contain refrigerant and air conditioning storage tubes that contain a phase change material. The air conditioning storage tubes are fin-shaped and are physically connected to the refrigerant tubes. The storage tubes may be added to one side of a generally conventional fin and tube evaporator or may be incorporated into the evaporator. 
       BACKGROUND OF THE INVENTION 
       [0002]    Most vehicles today include air conditioning systems to provide for improved occupant comfort. While being first introduced in the automotive world several decades ago, air conditioning systems have changed little. Thus the fundamental parts of the modern vehicle&#39;s air conditioning system are known and understood. These parts include the compressor, the condenser, the evaporator, the thermal expansion valve, and the drier or accumulator. In many ways the compressor is the heart of the vehicle&#39;s air conditioning system. The compressor pressurizes hot gaseous refrigerant and forces it on to the condenser. The condenser, which is like a small radiator, cools the hot gases received from the compressor. As these gases cool, they become liquid in the condenser. 
         [0003]    Liquid refrigerant leaves the condenser under high pressure and enters the drier or accumulator. The drier catches any liquid water that may inadvertently have entered the system. The liquid refrigerant, once cleared of any water, flows to the expansion valve which functions to remove pressure from the liquid refrigerant and literally allows it to expand. This reduction of pressure allows the liquid refrigerant to return to the vapor stage in the evaporator, the refrigerant&#39;s next stop. 
         [0004]    The evaporator is also similar in shape and function to a small radiator. Typically the evaporator is fitted inside of the vehicle&#39;s passenger compartment in or around the instrument panel. The still-liquid refrigerant enters the evaporator under low pressure from the expansion valve. The liquid refrigerant vaporizes while absorbing heat from inside the car. Cold air is circulated within the passenger compartment by a fan that pushes air across the fins of the evaporator. Low pressure refrigerant, now in gaseous form, exits the evaporator and returns to the compressor where the cycle is repeated. 
         [0005]    As fuel economy becomes an increasingly critical factor in the design of the automobile, many automobile manufacturers are equipping the engine with automatic start and stop technology. The start-stop technology enables the engine to be off while the vehicle is stopped, for example, at a stop light or in congested traffic. As some vehicles use mechanically belt-driven compressors to run the air conditioning system, the compressor will not function during the engine off time. Thus, an improvement in the air conditioning system components is required during the engine off time. 
       SUMMARY OF THE INVENTION 
       [0006]    The disclosed inventive concept overcomes the problems encountered during the engine off time by providing a storage evaporator that includes phase change material-containing tubes arranged side-by-side and in contact with refrigerant-containing tubes. The phase change material-containing tubes themselves are fin-shaped. More particularly, the storage evaporator of the disclosed inventive concept includes an upper coolant tank, a lower coolant tank, refrigerant tubes fluidly connecting said upper and lower tanks, and phase change material-containing tubes provided in contact with said refrigerant tubes. The storage tubes and the tanks may be added to one side of a generally conventional fin and tube evaporator or may be incorporated into the evaporator itself. 
         [0007]    The phase change material-containing tubes are disposed parallel with one another in a longitudinal direction. In addition, the phase change material-containing tubes may be attached to one another in the longitudinal direction. Attachment of the adjacent phase change material-containing tubes may be made by a strip. 
         [0008]    The refrigerant tubes have flat sides and the phase change material-containing tubes have flat sides. The flat sides of the refrigerant tubes are attached to the flat sides of said phase change material-containing tubes. The phase change material-containing tubes have a cross-sectional shape. The shape may be multi-sided, and is preferably six-sided or four-sided. 
         [0009]    The phase change material may be any of several materials. Preferably, but not exclusively, the phase change material is selected from the group consisting of an eutectic, a salt hydrate, and an organic material. The organic material is preferably, though not exclusively, selected from the group consisting of waxes, fatty acids, oils and polyglycols. 
         [0010]    In operation, energy is stored in the phase change material when the air conditioning compressor is in its “on” position. This energy is released from the phase change material when the compressor is in its “off” position. 
         [0011]    The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein: 
           [0013]      FIG. 1  is an isometric view of an add-on version of the storage evaporator according to the disclosed inventive concept that includes phase change material-containing tubes fitted adjacent refrigerant-containing tubes; 
           [0014]      FIG. 2  is also an isometric view of the storage evaporator of  FIG. 1  but taken from a different perspective in which the fluid flow tubes are illustrated; 
           [0015]      FIG. 3  is a front view of the storage evaporator of  FIGS. 1 and 2 ; 
           [0016]      FIG. 4  is an end view of the storage evaporator of  FIGS. 1 and 2 ; 
           [0017]      FIG. 5  is close-up view of a portion of the front view of the storage evaporator of the disclosed inventive concept illustrating the alternating, side-by-side placement of the phase change material-containing tubes and the refrigerant-containing tubes according to a first embodiment of the disclosed inventive concept; 
           [0018]      FIG. 6  is a perspective view of the portion of the storage evaporator illustrated in  FIGS. 1 and 2 ; 
           [0019]      FIG. 7  is a sectional view of the phase change material-containing tubes and the refrigerant-containing tubes according to a second embodiment of the disclosed inventive concept in which the phase change material-containing tubes have a six-sided configuration; 
           [0020]      FIG. 8  is a perspective view of a series of phase change material-containing tubes according to the second embodiment of the disclosed inventive concept; 
           [0021]      FIG. 9  is a sectional view of the phase change material-containing tubes and the refrigerant-containing tubes according to a third embodiment of the disclosed inventive concept in which the phase change material-containing tubes have a four-sided configuration; 
           [0022]      FIG. 9A  is a sectional view of a pair of adjacent refrigerant-containing tubes; 
           [0023]      FIG. 10  is a perspective view of a series of phase change material-containing tubes according to the third embodiment of the disclosed inventive concept; 
           [0024]      FIG. 11  is an end view of the integrated version of the storage evaporator according to the disclosed inventive concept that includes phase change material-containing tubes fitted adjacent refrigerant-containing tubes; 
           [0025]      FIG. 12  is an isometric view of a storage evaporator of  FIG. 11 ; and 
           [0026]      FIG. 13  is a perspective view of the portion of the storage evaporator illustrated in  FIGS. 11 and 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting. 
         [0028]    The storage evaporator for use with an air conditioning system for a vehicle according to the disclosed inventive concept is illustrated in its various embodiments in  FIGS. 1 through 10 . However, it is to be understood that the illustrated embodiments are suggestive and are not intended as being limiting. The general arrangement of the add-on version of the disclosed inventive concept is illustrated in  FIGS. 1 through 6 . In  FIGS. 5 and 6 , a first embodiment of the phase change material-containing tubes is illustrated. An alternate embodiment of the phase change material-containing tubes is illustrated in  FIGS. 7 and 8 . A further alternate embodiment of the phase change material-containing tubes is illustrated in  FIGS. 9 and 10 . The general arrangement of the integrated version of the disclosed inventive concept is illustrated in  FIGS. 11 through 13 . Regardless of the embodiment, the storage evaporator of the disclosed inventive concept overcomes challenges and limitations associated with current evaporators during engine off time and thus still provides air conditioning to the cabin when the compressor is off. 
         [0029]    The disclosed inventive concept includes the use of phase change material-containing tubes adjacent refrigerant-containing tubes. The phase change material may be any material that stores and releases thermal energy during the processes of melting and freezing. When a phase changing material freezes, it absorbs cold energy, thus providing cooling. This energy is referred to as latent heat of fusion or energy of crystallization. On the other hand, when phase change material melts, cold energy (cooling) of an equal amount is released, thus causing the physical change from a solid to a liquid. 
         [0030]    Phase change materials include salts and organics. Salts include eutectic phase change materials that are salt solutions in water having phase change temperatures below 0° C. Salts also include types of salts that have phase change temperatures above 0° C. Organics include polymers made up of long chain molecules. These typically include carbon and hydrogen compounds. Specific examples include waxes, fatty acids, oils and polyglycols. 
         [0031]    Referring to  FIGS. 1 through 6 , a general arrangement for the add-on version of a storage evaporator according to the disclosed inventive concept is illustrated. With particular reference to  FIGS. 1 and 2 , a storage evaporator  10  is illustrated. The overall shape and size of the storage evaporator  10  illustrated herein is meant to be suggestive only and is not intended as being limiting, as other shapes and sizes may be suitable as well. 
         [0032]    The storage evaporator  10  includes an upper tank assembly  12  and a lower tank assembly  14 . The upper tank assembly  12  and the lower tank assembly  14  are typically made of a metal, although other materials including polymerized materials may be used alone or in combination. A lower pressure, inlet refrigerant input  16  is provided as is a lower pressure, outlet gas refrigerant output  18 . The refrigerant flowing into the evaporator is typically a two-phase flow as opposed to a liquid state. On the other hand, the outlet of the evaporator may be either two-phase flow or in the gaseous state, depending on the application. The inlet refrigerant input  16  is connected to liquid input upper tank portion  20  and inlet input upper tank portion  22  by a branch  23 . The outlet refrigerant output  18  is connected to a outlet output upper tank portion  24 . 
         [0033]    A series of refrigerant-containing tubes  26  fluidly connect the upper tank assembly  12  and the lower tank assembly  14 . Positioned between the refrigerant-containing tubes  26  are phase change material-containing tubes  28 . The phase change material-containing tubes  28  may be made from one or more of several materials, including a polymerized material (such as polypropylene or polyamide), a metal, ceramic, or any other material suitable for this purpose.  FIGS. 5 and 6  illustrate a first embodiment of the phase change material-containing tubes in which the long axis of the phase change material-containing tubes  28  has a non-linear shape whereby gaps are alternatingly formed between the adjacent phase change material-containing tubes  28  themselves and the adjacent walls of the refrigerant-containing tubes  26 . The phase change material-containing tubes  28  are themselves fin-shaped, adding to overall system cooling efficiency. 
         [0034]    While the shape of the phase change material-containing tubes  28  shown in  FIGS. 5 and 6 , it is to be understood that, regardless of the particular shape, the phase change material-containing tubes  28  are fin-shaped. This is also the case for the shapes of the phase change material-containing tubes shown in  FIGS. 7 and 8  and also in  FIGS. 9 and 10 . The fin-shaped configuration allows these tubes to additionally function as cooling fins, thus avoiding the need for separate fins as is currently known. 
         [0035]    Referring to  FIGS. 7 and 8 , a second embodiment of the phase change material-containing tube construction is illustrated. According to this embodiment, a series of plenums  30  is illustrated in cross-section next to adjacent refrigerant-containing tubes  26 . Each plenum  30  includes a first PCM-filled half  31  and a PCM-filled second half  32 . The first half  31  and the second half  32  are joined by brazing or other joining techniques as are known in the art. The joined first half  31  and second half  32  define a series of six-sided, axially-formed air passageways  34 . The outer walls of the first half  31  and the second half  32  are in direct contact with a portion of outer walls  36  of the adjacent refrigerant-containing tubes  26 . The plenums  30  are formed from sheets of a stamped material, such as aluminum, that is formed together, thus defining the spaced apart walls that form the hollow, phase change material-containing walls. The plenums  30  are substantially shaped to act as fins where the cooling air flows through the axially-formed air passageways  34 , thereby eliminating the need for conventional cooing fins in this area. 
         [0036]    Referring to  FIGS. 9, 9A and 10 , a third embodiment of the phase change material-containing tube construction is illustrated. According to this embodiment, a series of plenums  38  is illustrated in cross-section next to adjacent refrigerant-containing tubes  26 . Each plenum  38  includes a first PCM-filled half  39  and a PCM-filled second half  40 . The first half  39  and the second half  40  are joined by brazing or other joining techniques as are known in the art. The joined first half  39  and second half  40  define a series of four-sided, axially-formed air passageway  42 , thereby functioning as a cooling fin and thus avoiding the need for additional cooling fins. The plenums  38  are formed from sheets of a stamped material, such as aluminum, that is formed together, thus defining the spaced apart walls that form the hollow, phase change material-containing walls. 
         [0037]    As illustrated in  FIG. 9A , the plenums  38 , the first PCM-filled half  39  includes an outer wall  46  and an inner wall  48 . The second PCM-filled half  40  includes an outer wall  50  and an inner wall  52 . A phase change material-containing area  54  in which phase change material  56  is contained is formed between the outer wall  46  and the inner wall  48  of the first half  39 . A phase change material-containing area  58  in which phase change material  60  is contained is formed between the outer wall  50  and the inner wall  52  of the second half  40 . As illustrated in  FIG. 9 , the outer wall  46  of the first half  39  is in contact with a portion of the outer wall  36  of the adjacent refrigerant-containing tube  26 . In the same way, the outer wall  50  of the second half  40  is in contact with a portion of the outer wall  36  of another adjacent refrigerant-containing tube  26 . 
         [0038]    Referring to  FIGS. 11 through 13 , a general arrangement for an integrated version of a storage evaporator according to the disclosed inventive concept is illustrated. It is to be understood that the overall shape and size of the storage evaporator  70  illustrated herein is meant to be suggestive only and is not intended as being limiting, as other shapes and sizes may be suitable as well. 
         [0039]    The storage evaporator  70  includes a main evaporator  72  and a PCM-containing portion  74 . A refrigerant inlet tube  76  is connected to an upper inlet tank  78  while a refrigerant outlet tube  80  is connected to an upper outlet tank  82 . A lower tank assembly  84  connects the main evaporator  72  to the PCM-containing portion  74 . 
         [0040]    The PCM-containing portion  74  includes a series of refrigerant-containing tubes  86  that fluidly connect the upper outlet tank  82  to the lower tank assembly  84 . Positioned between the refrigerant-containing tubes  86  are phase change material-containing tubes  88 . As with the add-on embodiment of the disclosed inventive concept discussed above, the phase change material-containing tubes  88  may be made from one or more of several materials, including a polymerized material (such as polypropylene or polyamide), a metal, ceramic, or any other material suitable for this purpose. The structures of the phase change material-containing tubes  88  may be the same as those structures illustrated in  FIGS. 7 through 10  and discussed in conjunction therewith. 
         [0041]    In operation, when the air conditioning compressor is “on,” the phase change material is cooled as is known in a common refrigeration process. However, when the air conditioning compressor is “off” (as is typically the case in a start/stop vehicle), the phase change material releases its cold energy to cool the incoming air, thus providing air conditioning to a vehicle in an efficient and cost-effective manner. 
         [0042]    The disclosed inventive concept offers several advantages over the prior art, including, but not limited to, ease of addition to known fin and tube evaporator designs (whereby tooling costs are significantly reduced), avoidance of the need for additional fins since the phase shape material-containing tubes are already shaped like fins, and a more effective heat transfer because the phase change material has much larger heat exchange surface areas relative to the incoming air to be conditioned. For these and other reasons, the disclosed inventive concept of a storage evaporator provides superior performance at a lower cost when compared with known systems. 
         [0043]    While the preferred embodiments of the disclosed inventive concept have been discussed are shown in the accompanying drawings and are set forth in the associated description, one skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.