Abstract:
A compact, low-cost and thermally efficient multi-plate heat exchanger includes a plurality of stamped plates that are stacked adjacent one another in a compact configuration. The plates each have a thin, flat body portion and a sidewall. Inlet and outlet passages are provided in the plates to direct first and second fluids through the stack. The plates are mechanically formed to emboss the plates around the passages. The respective passages for the first fluid are embossed on one direction, while the respective passages for the second fluid are embossed in another direction. The embossing alternates between plates, such that ring grooves are formed between the plates where it is desired to fluidly communicate with a respective passage. A high efficiency, extended surface fin structure and a pair of flow rings are located on each plate. The flow rings are located in the ring grooves for directing fluid between the respective plates. Each of the flow rings includes radial flow openings for evenly distributing the fluid between the plates. The plates are stacked with additional fin structure and ring pairs between each pair of plates, to achieve the thermal requirements of the particular application. The plates are then permanently secured together into a integral structure, such as by brazing.

Description:
CROSS-REFERENCE TO RELATED CASES  
       [0001]    The present application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/243,921; filed Oct. 27, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to multi-plate heat exchangers.  
         BACKGROUND OF THE INVENTION  
         [0003]    Multi-plate heat exchangers are known which allow heat transfer between two or more fluids. The heat exchangers can be used to heat or cool a primary fluid, using for example, air, water or oil as a second fluid. Multiple plates are held together and have flow passages for the fluids, which are directed into a fin or corrugated structure between the plates. The fin/corrugated structure increases the surface area between the plates to improve the thermal efficiency of the exchanger.  
           [0004]    The flow of one (for example, the primary) fluid is directed through a first inlet passage, through the fin structure between two plates, to a first outlet passage; while the flow of the second fluid is directed through a second inlet passage, through a separate fin structure between other plates, to a second outlet passage. The plates are stacked adjacent one another in alternating relation such that heat transfer (via convection and conduction) occurs between the fluids and the plates. The plates are sealed around their periphery and around the passages to provide a flow path and to separate the fluids. More than two fluids can be incorporated by appropriately scaling the number of plates and adding appropriate inlet and outlet passages. The plates are held together such as through brazing, soldering or welding or by end plates which squeeze the plates together.  
           [0005]    Multi-plate heat exchangers of this type are appropriate for many applications, and can be more thermally efficient as compared to competing technologies such as shell-and-tube heat exchangers.  
           [0006]    Various configurations of multi-plate heat exchangers are known, but it is believed many suffer drawback such as a large size, complicated manufacture of the plates and difficult and time-consuming assembly. Many of the plates are mechanically formed so as to include a unitary fin structure. This generally requires complicated, time-consuming and expensive forming operations. The apparatus for pressing the plates together also adds bulk and cost to the exchanger. As such, it is believed there is a demand for a compact, low-cost, thermally-efficient, multi-plate heat exchanger which is appropriate for many applications, and which is simple to manufacture and assemble.  
         SUMMARY OF THE PRESENT INVENTION  
         [0007]    The present invention provides a compact, low-cost and thermally efficient multi-plate heat exchanger which is appropriate for many applications, and which is simple to manufacture and assemble.  
           [0008]    According to the present invention, the heat exchanger includes a plurality of stamped plates that are stacked adjacent one another in a compact configuration. The plates each have a thin, flat body portion and a sidewall extending around the periphery of the body portion. Inlet and outlet passages are provided in the plates to direct first and second fluids through the plate stack. The plates are mechanically formed to emboss the plates around the passages. The respective passages for the first fluid are embossed in one direction, while the respective passages for the second fluid are embossed in another (opposite) direction. The embossing alternates between plates, such that ring grooves are formed between the plates where it is desired to fluidly communicate with a respective passage.  
           [0009]    A high efficiency, extended-surface fin structure, and a pair of flow rings are located on each plate. The fin structure is preferably a separate component from the plates and can have any type of convoluted geometry appropriate for the particular application. The fins are formed with an appropriate height, and from an appropriate material. The flow rings are located in the ring grooves for directing fluid through the fin structure between the respective plates. Each of the flow rings includes a pair of annular body portions separated by a series of support members. The flow rings are sized to bound the flow passage, and each includes radial flow openings between the support members for evenly distributing the fluid through the fin structure. The thickness and configuration of the flow rings can be varied so as to easily customize the flow for a particular application. The plates are stacked with additional fin structure and ring pairs between each pair of plates, to achieve the thermal requirements of the particular application.  
           [0010]    The plates are permanently secured together into an integral structure, preferably by cladding or spraying the plates with a braze material, and then heating the plates in a furnace.  
           [0011]    The flow rings provide a flow of one fluid between a specific set of plates—without allowing leakage to the fluid flow through an adjacent plate set. The plates and flow rings distribute fluid evenly across the entire plate structure and utilize the entire fin structure. The rings can also be easily configured to customize the flow between any of the plates. The separate fin structure and flow rings are easy to manufacture and assemble with the plates. The separate fin structure also allows the plates to be more compact—as compared to forming the plates with a unitary fin structure. The separate fin structure also allows fin structure of different material to be used, to further customize the heat exchanger for a particular application. In all, a thermally efficient exchanger is provided that has a low cost, a compact size, and which is easy to manufacture and assemble.  
           [0012]    Further features of the present invention will become apparent to those skilled in the art upon reviewing the following specification and attached drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a top plan view of a heat exchanger constructed according to the principles of the present invention;  
         [0014]    [0014]FIG. 2 is a side view of the heat exchanger of FIG. 1;  
         [0015]    [0015]FIG. 3 is a cross-sectional side view of the heat exchanger taken substantially along the plane described by the lines  3 - 3  of FIG. 1;  
         [0016]    [0016]FIG. 4 is a cross-sectional end view of the heat exchanger taken substantially along the plane described by the lines  4 - 4  of FIG. 2;  
         [0017]    [0017]FIG. 5 is an elevated perspective view of one of the plates of the heat exchanger of FIG. 1 shown with the fin structure and flow rings;  
         [0018]    [0018]FIG. 6 is a side view of one of the plates of the heat exchanger of FIG. 1;  
         [0019]    [0019]FIG. 7 is a cross-sectional end view of the plate taken substantially along the plane described by the lines  7 - 7  of FIG. 6;  
         [0020]    [0020]FIG. 8 is a cross-sectional end view of the plate taken substantially along the plane described by the lines  8 - 8  of FIG. 6;  
         [0021]    [0021]FIG. 9 is an enlarged view of a portion of the plate shown in FIG. 8;  
         [0022]    [0022]FIG. 10 is a top plan view of a flow ring for the heat exchanger of FIG. 1;  
         [0023]    [0023]FIG. 11 is a cross-sectional side view of the flow ring taken substantially along the plane described by the lines  11 - 11  of FIG. 10; and  
         [0024]    [0024]FIG. 12 is a schematic illustration of the flow path through the heat exchanger. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    Referring to the drawings, and initially to FIGS.  1 - 5 , a heat exchanger constructed according to the principles of the present invention is indicated generally at  15 . The heat exchanger  15  includes a series of stacked plates as at  17 , a fin structure as at  19 , and flow rings as at  20 . The stacked plates are all thin, flat plates formed of an appropriate material, preferably a corrosion-resistant sheet metal (such as type 304 Stainless). The plates are shown having a rectangular configuration, but the dimension and configuration of the plates can vary depending upon the particular application, i.e., the heat transfer requirement. In one embodiment, it was found that plates having a thickness of 0.015 in. was appropriate, but again, this can vary depending upon the particular application. In addition, the number of plates, and consequently the number of fin structures and flow ring sets can vary depending upon the particular application. In the illustrated embodiment (see FIG. 4), nine plates  17 A- 17 I, eight flow rings  20 A- 20 H and eight fin structures  19 A- 19 H are shown, however, again, this can vary depending upon the particular application.  
         [0026]    The plates each include an inlet opening  21  and an outlet opening  22  for a first fluid; and an inlet opening  23  and an outlet opening  24  for a second fluid. The inlet and outlet openings for each fluid are preferably at opposite ends of the plate and are catty-corner (diagonally-opposite) from each other. The inlet openings and outlet openings can of course be reversed, depending on the connection within the fluid system. Appropriate fittings or nipples  25  (see FIG. 12) are sealingly attached to each opening in the uppermost plate  17 A to facilitate the connection within the fluid system. The lowermost plate  17 I preferably is continuous, that is, it does not include openings  21 - 24 , although all other aspects of this plate are the same as the others.  
         [0027]    Preferably each plate is cladded or sprayed on both sides with an appropriate braze material to facilitate securing the plates together, as will be described herein in more detail.  
         [0028]    Referring to FIGS.  6 - 9 , the plates are each stamped or otherwise mechanically formed to create embossments (i.e., a raised or indented portion) around the openings. Two sets of plates are provided, with a different embossment configuration provided for each set. In one set (plates  17 A,  17 C,  17 E,  17 G,  17 I), each plate end includes a first embossment  28  bounding outlet opening  24  projecting outwardly (upwardly) away from the upper surface  29  of the plate, and a second embossment  31  bounding outlet opening  22  projecting outwardly (downwardly) away from the lower surface  32  of the plate. The opposite end of each plate includes a similar structure, however, preferably the embossments are reversed, that is, a third embossment  34  bounds inlet opening  21  and projects outwardly (downwardly) away from the lower surface  32  of the plate; while a fourth embossment  36  bounds outlet opening  23  and projects outwardly (upwardly) away from the upper surface  29 . The embossments  28  and  36  are preferably co-planar with one another; while the embossments  31  and  34  are preferably co-planar with one another. The terms “upper” and “lower” are used herein only for ease of describing the relative position of the various components, and it is noted that the heat exchanger may be oriented in any direction appropriate for the particular application.  
         [0029]    The other set of plates (plates  17 B,  17 D,  17 F,  17 H) also have embossments, however the embossments are reversed, with the embossment bounding outlet opening  24  projecting outwardly (downwardly) away from the lower surface of the plate, and the second embossment bounding outlet opening  22  projecting outwardly (upwardly) away from the upper surface of the plate. Similarly, the opposite end of each plate in this set includes a third embossment  34  bounding inlet opening  21  and projecting outwardly (upwardly) away from the upper surface of the plate; and a fourth embossment bounding outlet opening  23  and projecting outwardly (downwardly) away from the lower surface of the plate. All other aspects of the plates of this set are the same as in the first set.  
         [0030]    Each embossment defines an annular ring groove surrounding the respective opening. As shown for example in FIG. 9, embossment  34  defines an annular, flat ring groove  40  which completely surrounds opening  21  and opens outwardly from the lower surface  32 . Likewise, an annular, flat ring groove is provided by embossment  31  surrounding opening  22  opening outwardly (downwardly) from lower surface  32 ; while annular, flat ring grooves are provided by embossments  28  and  36  surrounding openings  24  and  23 , respectively, but opening outwardly (upwardly) from upper surface  29 .  
         [0031]    Each plate also includes a short lip or sidewall as at  46  bounding the periphery of the plate and extending outwardly (downwardly) from the lower surface  32 . The sidewall  46  allows the plates to be stacked one on top the other in adjacent, surface-to-surface relation, with the sidewall providing a peripheral seal with an adjacent underlying plate, as will be described herein in more detail. The sidewall projects away from the plate considerably further than the embossments. In one embodiment, the embossments projected outwardly from the surface of the plate about 0.081 in., while the sidewall projected outwardly from the plate about 0.375 inches. But again, this can vary depending upon the particular application.  
         [0032]    In any case, the fin structure  19  is disposed across the majority of the plate. The fin structure  19  comprises any type of convoluted geometry appropriate for the particular application, such as lanced offset, wavy, plain or any other surface configuration, and the fins can be formed with an appropriate height, and of an appropriate density and material. Preferably the fin structure is formed from a light weight, thermally efficient material (e.g., type 304 Stainless), and is relatively thin (less than the height of the sidewall  46 ), so that the heat exchanger assembly is relatively compact and yet has a considerable surface area. The fin structure preferably extends essentially from side-to-side of the plates, and has a geometry to direct fluid from one end of the plates directly to the other. The fin structure is preferably formed of a single piece, although it could also be formed from multiple pieces laid end-to-end. The fin structure is preferably a separate piece from the plates, and then located in the area of the plates between openings  21 ,  23  and  22 ,  24 .  
         [0033]    The flow rings  20  are illustrated in FIGS. 10 and 11. Each flow ring has an upper annular body portion  50  and a lower annular body portion  52 , separated by a series of axial support members as at  54 . The upper and lower annular body portions are preferably thin and flat and are supported parallel (co-planar) to one another. The annular body portions  50 ,  52  have essentially the same geometry as the ring grooves  40 , such that the flow rings fit easily within each groove. The support members define radial flow passages around the circumference of the flow ring to facilitate the even distribution of fluid. The number and geometry of the support members can vary, depending upon the particular application. In one embodiment, twelve evenly-spaced support members were provided, which comprised approximately 30% of the total circumferential area of the flow ring. The support members in the illustrated embodiment extend between the inner diameters of the upper and lower annular body portions, and projected radially inward a short amount, however the geometry of the support members can vary depending upon the particular application, with the number and circumferential length of the support members influencing the flow through the ring.  
         [0034]    The annular body portions  50 ,  52  and support members  54  of the flow rings are preferably formed unitarily (in one piece) for ease of manufacture, although they could also be formed in multiple pieces and secured (e.g., brazed, welded, etc.) together. The flow rings can also have different configurations (arrangement of support members, length of support members, etc.) to vary the fluid flow through the respective opening, as will be described herein in more detail.  
         [0035]    The heat exchanger is assembled by locating a pair of flow rings and the fin structure between a pair of plates, one plate being from each set. The plates are arranged such that a pair of embossments of one inlet and one outlet opening are spaced somewhat apart from one another, while a pair of embossments from the other inlet and other outlet opening are in adjacent, surface-to-surface relation to each other. The flow rings are positioned in the ring grooves between the spaced-apart embossments, and fit essentially flush between the opposing ring grooves. The flow rings and contacting embossments space the plates apart sufficiently such that the fin structure can be located therebetween. In this way, a flow path is provided through the one inlet opening, axially into and radially outward through one flow ring, through the fin structure, and radially into and axially out of the other flow ring. The pair of plates therefore direct one fluid across the plate structure, and allow convection and conduction to occur between the fluid and the fin structure.  
         [0036]    Similarly, another plate, fin structure and pair of flow rings are located on one of the first two plates, the additional plate being a plate from the other set, such that the embossments for the other inlet and outlet openings are spaced apart from one another, while the embossments for the first inlet and outlet openings are in adjacent, surface-to-surface relation. The flow rings are then located between the embossments which are spaced-apart from each other, and another fin structure is located between the plates. In this way, a second flow path is provided for a second fluid through the other inlet opening, across the other fin structure, to the other outlet opening. Conduction occurs across the adjoining plate such that thermal transfer occurs between the fluids.  
         [0037]    To prevent leakage between the plates, the plates are sealed together, such as by brazing, into an integral structure. The plates can be heated such that the cladding brazes the plates together, such as at the tips of the fin structure contacting the plates, and along the contacting flat surfaces of the flow rings. The flat, surface-to-surface contact between the contacting embossments facilitates a leak-free seal between the plates, while the inner plate surfaces and the surfaces of the annular body portions of the flow rings facilitates securing the flow rings to the plates. The sidewall along the periphery of the plates is also brazed to the sidewall of an adjacent plate. As such, the flow paths of the two fluids are completely fluidly separated between the plates. Other means such as welding, soldering or presses, can be provided to secure the plates to one another, and although less preferred, may be appropriate in certain applications.  
         [0038]    The number of plates, fin structures and flow rings can be scaled up or down depending upon the particular application. The flow rings are located between the spaced apart embossments, and therefore alternate locations across the width of the plate stack. More than two inlet openings and outlet openings can also be provided, to introduce three or more fluids between the plates. In this case, further embossments would be created and additional flow rings would be used. This is easily accomplished.  
         [0039]    As should be appreciated, the flow rings can be sized so as to space the plates varying distances apart from one another to increase or decrease the flow between the plates. As illustrated in FIG. 12, flow rings  20 B and  20 D have a longer axial length than flow rings  20 F. Thus, a greater flow will occur between plates  17 B and  17 C, and  17 D and  17 E, than between plates  17 F and  17 G (only seven plates  17 A- 17 G are shown in FIG. 12). The flow ring pairs can also have different configurations (such as by varying the width and/or number of support members), if it desirable to have a greater or lesser flow of one fluid as compared to the other. The use of flow rings therefore easily customizes the fluid flow for the particular application.  
         [0040]    The flow rings thereby provide a flow of one fluid between a specific set of plates—without allowing leakage to the fluid flow through an adjacent plate set. The plates and flow rings distribute fluid evenly across the entire plate structure and entirely utilize the fin structure. The rings can also be easily configured to customize the flow between any of the plates. The separate fin structure and flow rings are easy to manufacture and assemble with the plates. The separate fin structure also allows the plates to be more compact—as compared to forming the plates with a unitary fin structure. The separate fin structure also allows fin structure of different material to be used, to further customize the heat exchanger for a particular application. In all, a thermally efficient exchanger is provided that is low in cost, has a compact size, and which is easy to manufacture and assemble.  
         [0041]    The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein should not, however, be construed as limited to the particular form described as it is to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the scope and spirit of the invention as set forth in the appended claims.