Patent Publication Number: US-8978746-B2

Title: Heat exchanger header plate

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to co-pending U.S. Provisional Patent Application Ser. No. 61/439,642, which was filed on Feb. 4, 2011, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to heat exchangers and, more particularly, to header plates for use with heat exchangers. 
     BACKGROUND 
     Some heat exchangers include flattened tubes that extend between and are supported by two spaced apart header plates. Each header plate typically includes openings that are shaped and sized to receive ends of the flattened tubes. A fluid tank is fitted and sealed to each header plate to receive heat exchange fluid that flows through the flattened tubes. Such heat exchangers commonly experience thermal cycle stress due to fluids of different temperatures passing through the flattened tubes. In particular, different temperature fluids may cause expansion and/or contraction of the flattened tubes, creating stresses at joints between the tubes and the header plates. As a result, the joints, or the flattened tubes themselves, may fracture, resulting in leakage and possible failure of the heat exchanger. 
     SUMMARY 
     In some embodiments, the invention provides a header plate for a heat exchanger, the header plate comprising a first side flange; a second side flange spaced apart from and opposing the first flange; a generally planar surface located between and connecting the first and second flanges, the generally planar surface and the first and second side flanges together at least partially defining an internal volume of the heat exchanger; a bead formed into the generally planar surface to locally deform the surface in a direction away from the internal volume, the bead extending to and blending into the first side flange; and a tube receiving opening extending through the generally planar surface into the internal volume, the tube receiving opening extending through the bead. 
     In other embodiments, the invention provides a heat exchanger comprising a plurality of parallel arranged flat tubes having internal passages to convey a fluid through the heat exchanger; a fluid tank; and a header plate coupled to the fluid tank to at least partially define an internal volume of the heat exchanger, the header plate comprising a first flange, a second flange spaced apart from and opposing the first flange, a generally planar surface located between and connecting the first and second flanges, a bead formed into the generally planar surface to locally deform the surface in a direction away from the internal volume, the bead extending to and blending into the first side flange, and a plurality of tube receiving openings extending through the generally planar surface into the internal volume and receiving an end of one of the plurality of parallel arranged flat tubes, wherein at least one of the plurality of tube receiving openings extends through the bead. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates a heat exchanger according to one embodiment of the invention. 
         FIG. 2  is a perspective view of a header plate of the heat exchanger of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of a portion of the header plate taken along section line  3 - 3  of  FIG. 2 . 
         FIG. 4  is a cross-sectional view of the header plate taken along section line  4 - 4  of  FIG. 2 . 
         FIG. 5  is a perspective view of a portion of a header plate according to another embodiment of the invention. 
         FIG. 6  is a perspective view of a portion of a header plate according to yet another embodiment of the invention. 
         FIG. 7  is a cross-sectional view of the header plate taken along section line  7 - 7  of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  illustrates a heat exchanger  10 , which may be, for example, a charge-air-cooler or intercooler positioned downstream of a turbocharger in a vehicle engine. The heat exchanger  10  includes a plurality of flat tubes  14  arranged in parallel, a fluid tank  18  positioned at each end of the heat exchanger  10 , and a header plate  22  coupled to each fluid tank  18 . The tubes  14  are generally elongated tubes defined by two rounded ends and two generally flattened sides that connect the ends. Each tube  14  extends between the header plates  22  and has an internal passage to convey a fluid through the heat exchanger  10 . The fluid tanks  18  and the header plates  22  at least partially define internal volumes  26  of the heat exchanger  10 . The internal volumes  26  confine fluid within the heat exchanger  10  as the fluid passes through the tubes  14  and fluid tanks  18 . 
       FIGS. 2-4  illustrate one of the header plates  22  in detail. Although only one header plate  22  is shown, it should be readily apparent that the other header plate  22  in the heat exchanger  10  can be substantially similar to the illustrated header plate  22 . In the illustrated embodiment, the header plate  22  includes a generally planar surface  30 , a pair of side flanges  34 , and a plurality of tube receiving openings  38 . The planar surface  30  extends between and connects the flanges  34 . The flanges  34  are spaced apart from each other on opposing sides of the planar surface  30  and extend generally perpendicularly from the planar surface  30 . The flanges  34  couple to and engage the corresponding fluid tank  18  ( FIG. 1 ) to help define the internal volume  26  of the heat exchanger  10 . 
     The tube receiving openings  38  are formed in and extend through the generally planar surface  30  to the internal volume  26 . In the illustrated embodiment, the header plate  22  includes fifteen tube openings  38  arranged in a single row. In other embodiments, the header plate  22  can include fewer or more tube openings  38 . Additionally or alternatively, the tube openings  38  can be arranged in multiple rows, can be spaced apart by different distances, and/or can be arranged in different orientations. Each opening  38  receives an end of one of the tubes  14  of the heat exchanger  10  to support the tube  14 . As shown in  FIG. 2 , the illustrated openings  38  include two rounded ends  42  and two elongated straight sides  46  that generally match the shape and size of the tubes  14  and create a relatively tight fit between the header plate  22  and the tubes  14 . After having been received into the openings  38 , the tubes  14  can be permanently and sealingly affixed to the header plate  22  by brazing, soldering, welding, mechanical expansion, or other joining processes known in the art. 
     The header plate  22  also includes a plurality of beads  50  formed into the generally planar surface  30 . The beads  50  locally deform the surface  30  in a direction away from the internal volume  26  such that the beads  50  stand above the planar surface  30 . In the illustrated embodiment, the beads  50  are drawn out from the planar surface  30  in a direction substantially opposite the direction that the flanges  34  extend from the planar surface  30 . 
     In the illustrated embodiment, a single continuous bead  50  is located adjacent each tube opening  38  and substantially wraps around (e.g., surrounds) the opening  38  such that each tube receiving opening  38  extends through one of the beads  50 . When the tubes  14  ( FIG. 1 ) are inserted into the openings  38 , the beads  50  surround end portions of the tubes  14  to couple the tubes  14  to the header plate  22 . In other embodiments, multiple continuous or discontinuous beads may be formed into the planar surface  30  adjacent each tube opening  38  such that each tube opening  38  extends through more than one bead. 
     As shown in  FIG. 3 , each bead  50  has a generally rounded outer surface  54  whose apex defines the edge or perimeter of the corresponding tube opening  38 . A V-shaped groove  58 , or channel, is defined between the rounded outer surfaces  54  of adjacent beads  50 . Troughs  62  of the grooves  58  define a plane  66  that approximately represents the shape of the planar surface  30  if the beads  50  were not present. The beads  50  are formed in the planar surface  30  to extend beyond the plane  66  by a fraction of the thickness of the header plate  22 , without increasing the amount of material on the plate  22 . For example, in the illustrated embodiment, the header plate  22  has a thickness t of approximately 4 mm and the beads  50  extend beyond the plane  66  approximately 2 mm, or about half of the thickness of the header plate  22 . However, the thickness of material at the beads  50  is not greater than the thickness t of the header plate  22  because the beads  50  are formed by drawing or bending a portion of the planar surface  30  into the desired bead shape, rather than by adding material to the plate  22 . In other embodiments, the beads  50  may be formed in the planar surface  30  to extend beyond the plane  66  by a greater or lesser amount. By way of example, in some embodiments, the beads  50  can extend beyond the plane  66  by an amount ranging from 25% to 75% of the thickness t of the header plate  22 . 
     In the illustrated embodiment, the troughs  62  of the grooves  58  are spaced apart approximately 16 mm such that each bead  50  is approximately 16 mm wide. As such, the ratio of bead width to bead height (i.e., the height of the bead  50  extending beyond the plane  66 ) is approximately 8. In other embodiments, the ratio of bead width to bead height may be larger or smaller. 
     Referring to  FIGS. 2 and 4 , each tube opening  38  passes through a portion of a generally arcuate surface  70  on each side of the header plate  22 . The arcuate surfaces  70  define the transition from the generally planar surface  30  to the side flanges  34 . In the illustrated embodiment, the beads  50  extend across the entire planar surface  30  to the flanges  34 . As such, the beads  50  extend at least partially over the arcuate surfaces  70  to extend past rounded ends  42  of openings  38  to wrap entirely around the rounded ends  42  of the tube openings  38 . In the illustrated embodiment, the beads  50  decrease in height along the arcuate surfaces  70  thereby blending into the side flanges  34 , forming a smooth transition from the flanges  34  to the beads  50 . 
     As seen in  FIG. 4 , by extending the beads  50  entirely across the surface  30  to the flanges  34 , the openings  38  are kept entirely within the beads  50  while at the same time providing only a minimal clearance between the inner surfaces of the flanges  34  and the rounded ends of the tubes  14  (generally corresponding to the rounded ends  42  of the openings  38 ). Minimizing such clearances provides benefits in the ability of the heat exchanger  10  to withstand structural loadings such as can be caused by pressure cycling of the fluid in the internal volumes  26 . 
     According to one method of manufacturing the header plate  22 , a flat sheet is first machined, molded, formed, or otherwise provided. The beads  50  are then formed in the generally planar surface  30  of the flat sheet by drawing portions of the sheet outward. After the beads  50  are formed, holes are pierced or cut through the beads  50  to form the tube receiving openings  38 . Piercing the holes after the beads  50  are drawn makes it easier to create tube receiving openings of the desired shape and size. Otherwise, the tube receiving openings  38  may deform or warp if the beads are drawn around the holes after the holes are pierced. Edges of the flat sheet are subsequently bent to form the side flanges  34 . In some embodiments, it may be preferable to form the side flanges  34  at an earlier stage of the manufacturing process. For example, the side flanges  34  may be formed concomitant with the forming of the beads  50 , or after forming the beads  50  but before creating the openings  38 . 
       FIG. 5  illustrates a header plate  110  according to another embodiment of the invention. Similar to the header plate  22  discussed above with reference to  FIG. 2 , the illustrated header plate  110  includes a generally planar surface  114 , two side flanges  118  extending perpendicularly from the planar surface  114 , and a plurality of tube receiving openings  122  extending through the planar surface  114 . In the illustrated embodiment, the tube openings  122  are arranged in two parallel rows, rather than a single row, such that the header plate  110  can support two rows of tubes. In other embodiments, the header plate  110  may include three or more rows of tube openings  122 . 
     The illustrated header plate  110  also includes a plurality of beads  126  formed into the planar surface  114 . Similar to the beads  50  discussed above, the beads  126  may be formed into the planar surface  114  by drawing a portion of the planar surface  114  outward without increasing the amount of material on the header plate  110 . In the illustrated embodiment, the beads  126  are drawn out of the planar surface  114  at a relatively constant height across the entire planar surface  114 . In other embodiments, the beads  126  may be drawn out of the planar surface  114  at irregular heights. 
     As shown in  FIG. 5 , adjacent tube openings  122  from each row extend through a single bead  126  such that one continuous bead  126  wraps around both openings  122 . In other embodiments, each bead  126  may only wrap around a single tube opening  122 . In such embodiments, the header plate  110  may include two rows of discontinuous beads corresponding to the two parallel rows of tube openings. The illustrated beads  126  extend across the planar surface  114  and blend into both of the side flanges  118 . In some embodiments, each bead  126  may blend into only one of the flanges  118 . 
       FIGS. 6 and 7  illustrate a header plate  210  according to yet another embodiment of the invention. The header plate  210  includes a generally planar surface  214 , two side flanges  218  extending perpendicularly from the planar surface  214 , and a plurality of tube receiving openings  222  extending through the planar surface  214 . Similar to the header plate  110  discussed above with reference to  FIG. 5 , the tube openings  222  of the illustrated header plate  210  are arranged in two parallel rows, rather than a single row. 
     The illustrated header plate  210  also includes a plurality of beads  226  formed into the planar surface  214 . Similar to the beads  50 ,  126  discussed above, the beads  226  may be formed into the planar surface  214  by drawing a portion of the planar surface  214  outward without increasing the amount of material on the header plate  210 . In the illustrated embodiment, the beads  226  are arranged in parallel rows in direct correspondence to the parallel rows of tube openings  222 , so that each of the beads  226  wraps around a single tube opening  222 . 
     Each pair of side-by-side arranged beads  226  includes a mid portion  230  positioned therebetween. As shown in  FIG. 6 , the mid portion  230  between each pair of beads  226  is tapered or pinched such that the beads  226  more closely follow the contours of rounded ends  242  of the tube openings  222 . In addition, as shown in  FIG. 7 , the mid portion  230  between the beads  226  is slightly recessed such that the mid portion  230  does not extend as far outward from the planar surface  214  as the remainder of the beads  226 . Accordingly, the three-dimensional profile of the rounded ends  242  of the tube openings  222  located toward the center of the header plate  210  is similar to the profile of the rounded ends  242  near the flanges  218 . Such an arrangement also reduces the amount of material that needs to be drawn out from the planar surface  214  to form the beads  226 . 
     Forming beads on header plates reduces thermal stresses at joints between the header plates and the tubes of a heat exchanger. The beads allow the header plate and the tubes to be used in relatively higher-temperature applications, such as at inlet temperatures greater than 275 Celsius. In some scenarios, the beads provide a 20 percent reduction in stress, which may increase the thermal cycle life of the header plate up to four times that of a standard pierced header plate. 
     The beads also provide a low cost solution to increase the strength, life, and durability of header plates since they do not require additional material or components to manufacture. 
     Various features and advantages of the invention are set forth in the following claims.