Patent Publication Number: US-10317144-B2

Title: Brazed heat exchanger

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German Patent Application No. 10 2014 002801, filed Feb. 26, 2014, the entire contents of which are hereby incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The invention relates to a brazed heat exchanger from a stack of plate pairs and fins which are disposed between the plate pairs, and having ducts which vertically extend through the stack, for conveying in and conveying out a medium which flows through the plate pairs and which exchanges heat with another medium which flows through the fins, wherein the ducts are formed from openings in the plates and have moldings which extend around the opening peripheries of said openings, and having a plate, having corresponding apertures, which finishes off the stack. 
     BACKGROUND 
     A brazed heat exchanger has been depicted in the older patent application having the file number DE 10 2013 015 179.1, FIGS. 3 and 8. In this heat exchanger, a further but thinner plate has been disposed directly below the finishing-off plate. In this thinner plate, openings having moldings which extend around the opening peripheries of said openings and which, by way of the abovementioned moldings are brazed, as is the entire heat exchanger, to the adjacent first plate of the first plate pair, are likewise located. 
     In the case of this heat exchanger, deficiencies with regard to the resilience to alternating temperature loadings due to operational reasons have been observed in the course of testing. 
     SUMMARY 
     The object of the invention consists in improving the brazed heat exchanger mentioned at the outset with regard to its resilience to alternating temperature loadings due to operational reasons. 
     It has been determined in the mentioned test that cracks or fractures mainly arise below the finishing-off plate, specifically toward the adjacent moldings. 
     On account of the provision according to one embodiment of the invention of a thermally decoupling element which is disposed between the finishing-off plate, around the corresponding opening of the latter and toward an adjacent molding, cracks or fractures which are induced by alternating temperature loadings due to operational reasons are eliminated or at least significantly reduced, as has been demonstrated by further testing undertaken in the meantime. The thermally decoupling element may be inserted as an individual part. The thermally decoupling element, however, may also be a specially transformed region of a further plate, that is to say be integrally configured with the mentioned further plate. The further plate is located below the finishing-off plate. 
     The thermally decoupling element is a flat, plate-like element, the contour of which approximately corresponds to the contour of a molding. 
     The inventors have established that by means of the thermally decoupling elements(s), variable expansions on account of thermal loadings in the finishing-off plate and in the adjacent plate of the plate pair can be largely compensated for, on account of which the effects described above arise. 
     The invention will be explained in the following with exemplary embodiments by means of the appended drawings. Further features and advantages of the invention emerge from this description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a preferred exemplary embodiment, in a view onto part of a heat exchanger. 
         FIG. 2  shows this exemplary embodiment in another view. 
         FIGS. 3 and 4  show a second exemplary embodiment. 
         FIGS. 5 and 6  show a third exemplary embodiment. 
         FIG. 7  shows a substantial part of another heat exchanger in which the invention has been implemented. 
         FIG. 8  shows the heat exchanger according to  FIG. 1, 3 or 5 , inserted into an intake pipe of an internal combustion engine that represents a housing. 
     
    
    
     DETAILED DESCRIPTION 
     The appended  FIGS. 1 to 6  show practical views onto one of two sides, for example narrow sides, of the brazed heat exchanger. Visible are two vertical ducts  3  and  4 , wherein these may be ducts  3 ,  4  for a medium, for example for a coolant, which flows within the plate pairs  10  and/or through the plate pairs  10 . 
     It may be assumed here that the other side, for example narrow side, not shown, is configured in an identical manner. In this case two further vertically extending ducts  3 ,  4  are located on the other narrow side. 
     In order to clarify the aforementioned,  FIG. 7  has been added. Otherwise, this figure does not show the matter proposed here, since the region having a cover plate  6  at the top of the stack  1  of plate pairs  10  and fins  2  is not illustrated in  FIG. 7 . The ducts may be two inflow ducts  3  and two outflow ducts  4 .  FIG. 7  shows a view into the interior of the uppermost plate pair  10 . Ribs  9  are located in the plate pairs  10 . The ribs  9  are smaller than the interior of the plate pairs. There are two peripheral ducts  90  which extend in the longitudinal direction of the plates. The one peripheral duct  90  is an inflow-side peripheral duct in which a concurrent flow is present. The other peripheral duct  90  is an outflow-side peripheral duct  90  in which a diverging flow toward the two outflow ducts  4  is present. This design leads to an effective counterflow in relation to another medium, as is to be indicated by the arrows, on account of which the efficiency of heat exchange is improved as a spin-off. 
     However, it may in contrast also be assumed that the two ducts  3  and  4 , shown in  FIGS. 1 to 6 , are the only vertical ducts of the heat exchanger for the mentioned medium, wherein the one duct would be an inflow duct  3  and the other duct would be an outflow duct  4 . The arrows in  FIG. 2  are intended to indicate this. In the longitudinal direction of the heat exchanger, the medium covers an outward and an inward path. In this case, a throughflow of the heat exchanger would be present in the crossflow. 
     The ducts  3 ,  4  are formed from openings  5  in an upper plate  10   a  and in a lower plate  10   b  of the plate pairs  10 . The plates  10   a ,  10   b  have moldings  51  which extend around opening peripheries  50  of said openings  5 . 
     Visible are also the already mentioned fins  2  which are disposed between the plate pairs  10 . Another medium, which exchanges heat with the first mentioned medium, flows through the fins  2 . The other medium may be hot air (or an exhaust emission) which is to be cooled. 
     The temperature differences for operational reasons between the air and the coolant are enormous and stress the brazed heat exchanger to the point of material fractures which typically lead to the breakdown of the heat exchanger. 
     In order to improve the resilience of the heat exchanger to such loadings, the measure shown in  FIGS. 1 and 2  has proven particularly effective. 
     As shown by the mentioned figures, this measure is thermally decoupling elements  7  which are separately inserted as an individual part and which are incorporated into the vertical duct formation  3 ,  4 . As can be seen, each duct  3 ,  4 , has been assigned a separate element  7 . There thus may be either two or four such elements  7  per heat exchanger. At least one support foot  75  ( FIGS. 4 and 6 ) is disposed on the illustrated thermally decoupling elements  7 . 
     The term “thermally decoupling” used here refers exclusively to thermal influences due to operational reasons on the heat exchanger and/or on its decoupling, not to the brazing-technological production of said heat exchanger, which likewise takes place under thermal influences, as is known. With regard to the brazing-technological production, reference may be made to the prior art, such that no further explanations are required in this respect. 
     The insertion of the elements  7  takes place between a cover plate  6 , which is the uppermost plate lying on top of the stack in the exemplary embodiment, and the upper plate  10   a  of the first plate pair  10 . More specifically, the elements  7  are inserted between the cover plate  6  and the moldings  51  which extend around the opening peripheries  50  of the upper plate  10   a  of the first plate pair  10 . In respect of their extent, the elements  7  are also only slightly larger than the moldings  51 , as shown by  FIGS. 1 and 2 . A contour of the moldings  51  approximately corresponds to a contour  78  of the element  7 , which is to mean that these contours are similar with regard to shape and size. However, the thicknesses vary. 
     The particular effectiveness of this preferred embodiment may lie in that the elements  7  are provided with at least one fold  73  which, after the production or configuration thereof, leads to a doubling of the thickness of element  7  that extends partially across element  7 , the thickness differences across element  7  indicated by a doubling area  84  and an area without doubling  86  in  FIG. 2 . A second fold (not shown) at the opposite end would lead to a trebling of the thickness. As depicted in  FIG. 1 , the doubling area  84  of element  7  extends between the cover plate  6  and the upper plate  10   a  of the first plate pair  10 , and in the area without the doubling  86 , the cover plate  6  is not connected to element  7 . The doubling is provided by engagement between sections  70   a  and  70   b  of element  7 , section  70   b  being folded onto section  70   a , such that section  70   b  lies on top of section  70   a  and parallel to section  70   a . The fold  73  engages a top surface  71   b  of section  70   b  with a top surface  71   a  of section  70   a  such that the top surface  71   a  is partially covered by section  70   b . A bottom surface  72   a  of section  70   a  then faces away from a bottom surface  72   b  of section  70   b , the bottom surface  72   b  now facing in the same direction as the top surface  71   a . Since a portion of the top surface  71   a  is uncovered by section  70   b , there is a gap  82  between the top surface  71   a  and the cover plate  6 , where the cover plate  6  is disengaged from the element  7 . It should also be identifiable that the elements  7  are initially punched from a sheet metal having two openings—opening  74   a  of section  70   a  and opening  74   b  of section  70   b , as shown in  FIG. 2 . After production of the fold  73  (bending by 180°), the two openings  74   a ,  74   b  lie approximately on top of one another, as shown in  FIG. 2 . The two openings  74   a  and  74   b  extend the ducts  3 ,  4  from the upper plate  10   a  of the first plate pair  10  to the cover plate  6 , as shown in  FIGS. 1 and 2 . As can also be seen, the upper opening  74   b  of the elements  7  is slightly larger or designed in a somewhat different manner than the lower opening  74   a . Said opening  74   a  provides a transition from (in the exemplary embodiment) approximately flat-oval openings  5  and/or approximately flat-oval moldings  51  of the opening peripheries  50  to approximately round apertures  60  in the cover plate  6 . Accordingly, round connectors  30  for the coolant are located in the round apertures  60  of the cover plate  6  ( FIG. 4 ). 
     On account of the elongate or flat-oval openings  5  in the plates  10   a ,  10   b  there is inter alia also an advantageous flexibility in relation to the arrangement of the round connectors  30 . The arrangement of the connectors  30  depends on the circumstances of the installation space. This flexibility is not limited by the provision of the elements  7 , since the possibility for modifying the design of the elements  7  exists, that is to say for designing said elements  7  so as to be different, as can be seen from  FIG. 2 . 
     In other exemplary embodiments (not shown), the elements  7  are all configured so as to be identical, which is definitely more cost effective in relation to their production. 
     In the exemplary embodiment according to  FIGS. 3 and 4 , the fold  73  and/or the doubling of the element  7  produced by the fold  73  has been dispensed with. The element  7  has furthermore been configured in one part with two openings  172  for two adjacent ducts  3  and  4 . It is also significantly thicker than in the exemplary embodiment according to  FIGS. 1 and 2 . As can furthermore be seen from  FIG. 4 , the element  7  has at least in part been provided with a peripheral chamfer  77 . The brazing surface can be somewhat enlarged in this manner, but the main objective is presumably to improve the desired positioning of the fin  2 , which lies below the cover plate  6 , in the course of the pre-assembly of the heat exchanger. A support foot  75  on each end of element  7  is also shown in  FIG. 4 . Each support foot  75  extends from a bottom surface  171  of element  7  to the cover plate  6 . A hole  76  is disposed in the middle of element  7 , as depicted in  FIG. 4 . 
     In contrast to what has been described above in the exemplary embodiment, according to  FIGS. 5 and 6  a further plate  11 , which is substantially thinner than the cover plate  6 , has been disposed below the cover plate  6 . The elements  7 , likewise in contrast to what has been mentioned above, have been configured in an integral manner with the thinner further plate  11 , that is to say as one piece. In conformance with  FIGS. 1 and 2 , an element  7  has also here been assigned to each duct  3 ,  4 . A further conformance with the embodiments described above consists in that a doubling is also achieved with these elements  7  by means of a fold  73 . On account of the one-piece design, initially the further plate  11 , having corresponding projections  270  and the two openings  274   a ,  274   b  from which the elements  7  have to be configured by producing the fold  73 , will have to be cut out, wherein the projections  270  are laid inward and wherein the two openings  274   a ,  274   b  are brought into congruence. By means of  FIG. 6 , this procedure can be particularly clearly traced. The dimension of the further plate  11 , with respect to length and width, otherwise corresponds to that of the cover plate  6 . 
       FIG. 8  shows that the heat exchanger is disposed in a housing  8 , on the one side of which the other medium flows in, flows through the fins  2  of the heat exchanger, and flows out of the housing  8  on the opposite other side of said housing  8 , to which end the housing displays corresponding inflow and outflow openings  81 ,  82 . 
     The heat exchanger is sealed toward the housing  8 , in order to suppress bypasses for the other medium. 
     The medium flowing through the plate pairs  10  and the medium flowing through the fins  2  run either approximately in the direction of counterflow or in the direction of crossflow. 
     The heat exchanger is inserted into the housing  8  through an insertion opening  83  and, with a projecting, encircling periphery of the cover plate  6 , is preferably welded into place on a periphery of the insertion opening  83 .