Patent Publication Number: US-11644244-B2

Title: Curved heat exchanger and method of manufacturing

Description:
TECHNICAL FIELD 
     The present disclosure relates to a method of manufacturing a curved heat exchanger with two bent manifolds connected by a heat exchanger core that includes refrigerant tubes and fins. 
     BACKGROUND 
     Heat exchangers have various uses in the automotive industry. Some applications require a bent shape heat exchanger. For heat exchangers featuring flat micro-channel refrigerant tubes separated by corrugated fins, the bending process is challenging. 
     Bending micro-channel heat exchanger cores (MCHX cores) by bending the manifolds causes full width fin centers to crush in various locations, and the center crush varies uncontrollably between different fins along the length of the refrigerant tubes within the bend zone portion of the core. This leads to bent tubes due to irregular deformation of the fins. 
     SUMMARY 
     According to the present disclosure, a heat exchanger has an upper manifold having a first curved section; a lower manifold spaced from and extending parallel to the upper manifold and having a second curved section; a plurality of refrigerant tubes, and a plurality of corrugated fins. Each refrigerant tube extends along a tube length from the upper manifold to the lower manifold and is in hydraulic communication with the upper and lower manifolds. Each of the corrugated fins is inserted between respective adjacent ones of the refrigerant tubes so that the refrigerant tubes and corrugated fins define a core having a plurality of air channels from a curve-outer face of the core to a curve-inner face of the core. Each corrugated fin is formed by a strip having radiused portions alternating with planar portions, and the radiused portions are in contact with the respective adjacent refrigerant tubes. Each of the fins has a curve-inner edge and a curve outer edge and at least one edge of the curve-inner edge and the curve outer edge of at least one fin has a recessed portion in the planar portions that is recessed inward toward a center of the core. 
     According to one aspect of the present disclosure, the recessed portion in the planar portions is bent toward the lower manifold. 
     Accordingly, the recessed portion may be a central subsection of the planar portions between two subsections of the planar portion, where the edge extends as far outward from the core as the edge of the radiused portions. 
     The recessed portion may be present in each of the planar portions of the respective fin at least on the curve-inner edge or on the curve outer edge. 
     The recessed portion may alternatively be present on both the curve-inner edge and the curve outer edge. 
     Two of the fins that have a recessed edge may be spaced apart by at least one intermediate fin lacking a recessed portion on the side where two adjacent fins have a recessed portion. 
     In heat exchangers, in which the recessed portion is on the curve-inner edge, a subsection of the curve-inner edge may be folded down to extend downward toward the lower manifold. 
     Alternatively, the recessed portion may have an incision formed in the at least one edge, the incision extending inward toward the center of the core. In this case, the recessed portion may be on the curve-inner edge, the curve-outer edge, or both. 
     The cut edge may additionally be bent downward toward the lower manifold in regions laterally adjoining the incision. 
     In heat exchangers, in which the recessed portion is disposed on both the curve-inner edge and the curve-outer edge of a fin, a subsection of the curve-inner edge may be folded down to extend downward toward the lower manifold and an incision may be formed in the curve-outer edge. 
     According to a further aspect of the present disclosure, a method of making a curved heat exchanger comprises the following steps:
         assembling parts of the heat exchanger, the parts, after assembly, form a flat heat exchanger including:
           an upper manifold having a straight elongated shape;   an lower manifold spaced from and extending parallel to the upper manifold;   a plurality of refrigerant tubes, each refrigerant tube of the plurality of refrigerant tubes extending along a tube length with one tube end attached to the upper manifold and another tube end attached to the lower manifold; and   a plurality of corrugated fins, each of the corrugated fins inserted between two respective adjacent ones of the refrigerant tubes, the refrigerant tubes and corrugated fins defining a core having a plurality of air channels for airflow from a first face of the core to a second face of the core, each corrugated fin of the plurality of corrugated fins being formed by a strip having radiused portions alternating with planar portions, wherein the radiused portions are in contact with the respective adjacent refrigerant tubes;   
           driving an edge tool along the first face of the core between the respective adjacent refrigerant tubes in a direction parallel to the refrigerant tubes so as to form a respective recessed portion in a plurality of the planar portions; and   bending the first manifold, the second manifold, and the core about a common bending axis extending parallel to the refrigerant tubes to form a curved portion of the heat exchanger, wherein the curved portion of the heat exchanger includes the recessed portions.       

     The edge tool is may be driven along the first face of the core at such a depth that the recessed portions are recessed by a depth within a range of 2% to 50% of a local core depth of the heat exchanger. 
     The step of driving the edge tool along the first face may also bend the fin downward toward the lower manifold. 
     This step of driving the edge tool may be repeated on a different one of the plurality of corrugated fins. 
     The first face including the recessed portions may be a curve-inner face of the core or a curve-outer face of the core. 
     The step of driving the edge tool or a different edge tool may be repeated along the second face of the core between the respective adjacent refrigerant tubes or between different adjacent refrigerant tubes in a direction parallel to the refrigerant tubes so as to form further respective recessed portions in a plurality of the planar portions. 
     In one version, the edge tool is a folding tool and the recessed portions are formed by folded-down edge portions. 
     In a different version, the edge tool is a scoring tool and the recessed portions are formed by cut edge portions. 
     Further details and benefits of the present disclosure will become apparent from the following description of the appended drawings. The drawings are provided herewith solely for illustrative purposes and are not intended to limit the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, 
         FIG.  1    shows a heat exchanger prior to bending into a curved heat exchanger; 
         FIG.  2    shows a first edge tool in the form of a folding tool; 
         FIG.  3    shows a heat exchanger in the process of folding down edges of corrugated fins; 
         FIG.  4 A  shows a detail view of a fin prior to applying the folding tool; 
         FIG.  4 B  shows a detail view of a fin after applying the folding tool; 
         FIG.  4 C  shows a detail view of the fin of  FIG.  4 B  in a perspective indicated by line C-C of  FIG.  4 B ; 
         FIG.  5    shows a heat exchanger with folded fin edges after bending the heat exchanger into a curved heat exchanger; 
         FIG.  6    shows a second edge tool in the form of a scoring tool; 
         FIG.  7    shows a heat exchanger in the process of cutting edges of corrugated fins; 
         FIG.  8 A  shows a detail view of a fin prior to applying the scoring tool; 
         FIG.  8 B  shows a detail view of a fin after applying the scoring tool; 
         FIG.  8 C  shows a detail view of the fin of  FIG.  8 B  in a perspective indicated by line C-C of  FIG.  8 B ; 
         FIG.  9    shows a curve-inner side of a heat exchanger with cut fin edges after bending the heat exchanger into a curved heat exchanger; 
         FIG.  10    shows a curve-outer side of the heat exchanger of  FIG.  5    or of a different heat exchanger with cut fin edges after bending the heat exchanger into a curved heat exchanger; 
         FIG.  11    shows a cross-sectional detail view of a heat exchanger with both cut and folded fin edges; 
         FIG.  12    shows a schematic cross-sectional detail view of a heat exchanger with a full core; and 
         FIG.  13    shows a schematic cross-sectional detail view of a heat exchanger with a recessed core. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG.  1    shows an example of a heat exchanger  10  that, prior to bending, has a horizontal lower straight manifold and a horizontal upper straight manifold, which are spaced apart from each other extend parallel to each other. A plurality of parallel equidistant refrigerant tubes  14  extend from the lower manifold  12  to the upper manifold  13 . Each of the refrigerant tubes  14  is in hydraulic communication with the upper and lower manifolds  12  and  13 . The lower manifold  12  and the upper manifold  13  are of cylindrical tubular shape, while the refrigerant tubes  14  are flat tubes. Each of the refrigerant tubes  14  may be internally divided into a plurality of microchannels. The flat sides of adjacent flat tubes face each other. 
     A plurality of corrugated fins are arranged between the refrigerant tubes  14 . Each of the corrugated fins spans the distance between respective adjacent ones of the refrigerant tubes  14  so that the refrigerant tubes  14  and corrugated fins form a core of the heat exchanger  10 . The corrugation of the fins defines a plurality of air channels from an upstream face of the core to a downstream face of the core. Each corrugated fin  16  of the plurality of corrugated fins is formed by a strip having radiused portions alternating with planar portions  19  as is, for example, shown in  FIGS.  4 A and  8 A . The radiused portions are in contact with the respective adjacent refrigerant tubes  14 .  FIGS.  4 A and  8 A  also show micro-louvers  17  that may be formed from the strip material of the fin  16  and that are also present in  FIG.  11   . 
     When a heat exchanger  10  of the type shown in  FIG.  1    is bent about a bend axis that extends parallel to the refrigerant tubes  14 , the curve-inner side  38  of the core is laterally compressed, while the curve-outer side  40  of the core is expanded, as will be further discussed below in regards to  FIG.  5   . As the lower manifold  12  and the upper manifold  13  are bent parallel to each other, forces acting on the core may cause irregular deformation of the refrigerant tubes  14  and of the fins that impairs the optical appearance and may locally reduce the cross-sections of microchannels in some of the refrigerant tubes  14 . 
     According to one aspect of the present disclosure,  FIGS.  2  and  3    show a process of pre-treating the curve-inner side  38  of a heat exchanger  10  of the type shown in  FIG.  1    for facilitating a uniform deformation across the curve inner side of the heat exchanger  10  without the need for protective inserts or complex tools.  FIG.  2    shows a simple manual edge tool for creating a deformation of the edges of the fins on the curve-inner side  38 . The edge tool of  FIG.  2    includes a handle  20 , a cylindrical shaft  22 , and a conical tip  24 . The edge tool forms a folding tool  18  that is run along the curve-inner edges  42  of at least some of the fins in the direction of the refrigerant tubes  14  between two adjacent refrigerant tubes  14 . In view of the later use of the heat exchanger  10  that may result in condensed water collecting on the heat exchanger  10  core, it is preferred that the folding tool  18  is run along the fin edges from the upper manifold  13  toward the lower manifold  12  to facilitate the run-off of condensate. In the example shown in  FIG.  3   , the folding tool  18  is applied to fold down the edges of every other fin  16  arranged within a core section that will be bent in a later step. 
     The folding tool  18  is preferably held at an angle where the fin  16  is contacted by the blunt annular edge of the transition between the cylindrical shaft  22  and the conical tip  24 . The tip  24  of the folding tool  18  may alternatively be a rounded blunt tip  24 . 
       FIG.  4 B  shows a close-up detail of the folded edge of a fin  16  treated with the folding tool  18 . In comparison with  FIG.  4 A , which shows the untreated fin edges, the edge portions  26  at centers of the planar portions  19  of the fin  16  are all folded down toward the lower manifold  12 . The width of the folded edge portions  26  of the fin  16  depends on the diameter of the folding tool  18  used to deform the edge. Preferably, however, the folded edge portions  26  form a central subsection of the planar portions  19 , are limited to only the planar portions  19 , and do not extend to the radiused portions of the fin  16 . 
       FIG.  4 C  shows one of the folded-down edge portions of the fin  16  from below as indicated by the line C-C in  FIG.  4 B . By folding the edge of the fin  16  downward toward the lower manifold  12 , the edge is recessed inward toward the center of the core in the folded edge portion  26  relative to an unfolded edge portion  27 . The recess depth d of the folded edge portion  26  relative to the unfolded edge portion  27  provides a weakened resistance to bending and thereby a predetermined collapse point when the lower manifold  12 , the upper manifold  13 , and the core are bent to a desired curvature. The recess depth d of the folded edge portions  26  may be within the range of 2% to 30% of the depth  48  of the heat exchanger core, preferably 4% to 20%, for example within the range of 1 mm to 5 mm for a heat exchanger core having a depth of 2.5 cm (1 inch). 
     As will be described in more detail below, it has been found that alternating fins having folded edge portions  26  with fins having unfolded edge portions  27  is sufficient to protect the straight configuration of the refrigerant tubes  14  during bending because each refrigerant tube  14  is adjacent to a fin  16  with folded edge portions  26  on one side of the refrigerant tube  14  that provides the predetermined collapse points. It would, however, be within the scope of the present invention if adjacent fins had folded edge portions  26  within the curved section  46  of the heat exchanger  10 , or if only every third or fourth fin had folded edge portions, depending on the desired curvature radius of the heat exchanger. A greater curvature radius would require fewer fins with recessed edge portions. 
       FIG.  5    shows a heat exchanger  10  prepared as discussed above with folded fin edges after bending the upper manifold  13 , the lower manifold  12 , and the core about a bend axis A into a specified curvature. The bend axis A extends parallel to the refrigerant tubes  14 . Because each refrigerant tube  14  within the curved section  46  of the heat exchanger  10  is adjoined by a fin  16  with folded edge portions  26 , the refrigerant tubes  14  retain their integrity during the bending process. Accordingly, the refrigerant tubes  14  remain straight after bending. Instead, the folded fins collapse in the locations of the folded edge portions  26  that represent predetermined collapse points. 
       FIGS.  6  through  10    illustrate a variation of producing recessed fin edges that is suitable for curve-inner edges  42  and curve-outer edges  44  of the fins alike.  FIG.  6    shows an edge tool used for providing the recessed edge portions according to this variation. The edge tool is a scoring tool  28  with a handle  30 , and a blade  32 . The blade  32  has a convexly curved cutting edge  34 . 
     The scoring tool  28  is run along the curve-inner edges  42  of at least some of the fins in the direction of the refrigerant tubes  14  between two adjacent refrigerant tubes  14 . By running the scoring tool  28  along the fin edge as shown in  FIG.  7   , the fin edges are provided with an incision  35  in a cut edge portion  36 . The cut edge portions  36  are located generally centrally in the planar portions  19  of the fin  16 . The planar portions  19  immediately adjoining the incision  35  may be pulled in the direction of movement of the scoring tool  28 . In view of the later use of the heat exchanger  10  that may result in condensed water collecting on the heat exchanger  10  core, it is thus preferred that the scoring tool  28  is run along the fin edges from the upper manifold  13  toward the lower manifold  12  to facilitate the run-off of condensate. In the example shown in  FIG.  7   , the scoring tool  28  is applied to cut the edges of every other fin  16  arranged within a core section that will be bent in a later step. 
     The scoring tool  28  is preferably held at an angle where the fin  16  is contacted by the convexly curved cutting edge  34  of the blade  32 . The scoring tool  28  may alternatively have a rounded blade  32  extending at a different angle relative to the handle, for example generally perpendicular to the handle. 
       FIG.  8 B  shows a close-up detail of the cut edge portion  36  of a fin  16  treated with the scoring tool  28 . In comparison with  FIG.  8 A , which shows the untreated fin edges, the edge portions  36  at centers of the planar portions  19  of the fin  16  are all cut inward and slightly bent downward toward the lower manifold  12 . The extent of the downward bend of the lateral sides of the incisions  35  depends on the blade  32  of the scoring tool  28  used to deform the edge and on the stiffness of the fin  16  material. Preferably, however, the cut edge portions  36  including the bent sides form a central subsection of the planar portions  19 , are limited to only the planar portions  19 , and do not extend to the radiused portions of the fin  16 . 
       FIG.  8 C  shows one of the cut edge portions  36  of the fin  16  from below as indicated by the line C-C in  FIG.  8 B . By cutting the edge of the fin  16 , the edge is recessed inward toward the center of the core in the cut edge portion  36  relative to an uncut edge portion  37 . The recess D of the cut edge portion  36  relative to the uncut edge portion  37  provides a weakened resistance to bending or tearing and thereby a predetermined collapse point or tear line when the lower manifold  12 , the upper manifold  13 , and the core are bent to a desired curvature. The recess depth D of the cut edge portions  36  may be within the range of 5% to 50% of the depth of the core, preferably within the range of 10% to 30%. 
     As the recesses in the fin edges are formed by incisions  35 , not just folds, these edges can be collapsed on the curve-inner side  38  of or expanded on the curve-outer side  40  of a curved heat exchanger  10 . It has been found that alternating fins having cut edges with fins having uncut edges  37  is sufficient to protect the straight configuration of the refrigerant tubes  14  during bending because each refrigerant tube  14  is adjacent to a fin  16  with cut edge portions  36  on one side of the refrigerant tube  14  that provides the predetermined collapse points or tear lines. It would, however, be within the scope of the present invention if adjacent fins had cut edge portions  36  within the curved section  46  of the heat exchanger  10 , or if only every third or fourth fin had cut edge portions, depending on the desired curvature radius of the heat exchanger. A greater curvature radius would require fewer fins with recessed edge portions. 
       FIG.  9    shows a heat exchanger  10  prepared as discussed above with cut fin edges after bending the upper manifold  13 , the lower manifold  12 , and the core about a bend axis A into a specified curvature such that the cut fin edges are on the curve-inner side  38  of the curved heat exchanger  10 . The bend axis A extends parallel to the refrigerant tubes  14 . Because each refrigerant tube  14  within the curved section  46  of the heat exchanger  10  is adjoined by a fin  16  with cut edge portions  36 , the refrigerant tubes  14  retain their integrity during the bending process. Accordingly, the refrigerant tubes  14  remain straight after bending. Instead, the cut fins collapse in the locations of the cut edge portions  36  that represent predetermined collapse points. 
       FIG.  10    shows another heat exchanger  10  prepared as discussed above with cut fin edges after bending the upper manifold  13 , the lower manifold  12 , and the core about a bend axis A into a specified curvature such that the cut fin edges are on the curve-outer side  40  of the curved heat exchanger  10 . The bend axis A again extends parallel to the refrigerant tubes  14 . Because each refrigerant tube  14  within the curved section  46  of the heat exchanger  10  is adjoined by a fin  16  with cut edge portions  36 , the refrigerant tubes  14  retain their integrity during the bending process. Accordingly, the refrigerant tubes  14  remain straight after bending. Instead, the cut fins spread apart in the locations of the cut edge portions  36  that represent predetermined tear lines. 
     The principles of  FIGS.  9  and  10   , or of  FIGS.  3  and  10   , while shown on different heat exchanger  10   s , may be combined on a single heat exchanger  10 . For example, both the curve-inner and the curve-outer fin edges may carry incisions  35 , thus combining the features of  FIG.  9    and  FIG.  10   . Where only every other fin edge is cut on a given side of the heat exchanger  10 , the incisions  35  on the curve-outer side  40  may be made in fins that also carry incisions  35  on the curve-inner side  38 . Alternatively, each of the fins within the curved portion of the heat exchanger  10  may have a cut edge, alternating between the curve-inner edge  42  and the curve outer edge of adjacent fins. 
     Also, as discussed above, while the curve outer side of the heat exchanger  10  may have cut fin edges, the curve-inner side  38  of the heat exchanger  10  may have folded fin edges. Again, where only every other fin edge is cut on the curve-outer side  40  and folded on the curve-inner side  38  of the heat exchanger  10 , the incisions  35  on the curve-outer side  40  may be made in fins that also carry folds on the curve-inner side  38 . 
     This is illustrated in  FIG.  11   , showing a vertical cross-sectional cut through one of the corrugated fins. The curve-inner side  38  of the fin  16  features folded edge portions  26 , while the curve-outer side  40  features cut edge portions  36 . Alternatively, each of the fins within the curved portion of the heat exchanger  10  may have one of a cut edge and a folded edge, alternating between the curve-inner edge  42  being folded and the curve outer edge being cut from one fin  16  to the next. 
     Combining the principles of  FIGS.  9  and  10   , or of  FIGS.  3  and  10    is of particular interest in heat exchanger  10   s  having a full core as shown in  FIG.  12   , where the core composed of the refrigerant tubes  14  and fins extends equally far to the curve-inner side  38  and curve-outer side  40  of the manifold. Some heat exchangers  10  are designed to have a recessed core as shown in  FIG.  13   , at least in the curved section  46  of the heat exchanger  10 . This recess may be on the curve-outer side  40  or the curve-inner side  38 , or on both sides  38  and  40 . The entire curved core section may be recessed on one side so that no cut edge portions  36  or folded edge portions  26  may be necessary on that side. If only one side of the curved core section is recessed without any treated edge portions, the recessed side is preferably the curve-outer side so that the cut edge portions  36  or folded edge portions  26  are located on the curve-inner side, which is less visible in the installed state of the heat exchanger. That way, the curve-outer side has an optically more appealing appearance. The recessed side of the core may be close enough to the central axis of the manifold that the compression or expansion between the refrigerant tubes  14  is sufficiently reduced to avoid deformations of the refrigerant tubes  14 . Alternatively, the even the fin edges of a recessed core section may be folded or cut. 
     It should be noted that the step of folding or cutting the fin edges in the planar portions has been described as a manual process. This process, however, can easily be performed by a machine providing a linear movement of a rake-like attachment, in which each of the rake teeth is formed of an edge tool as described. The edge tools may be interchangeable between a folding tool and a cutting tool. Further, the lateral distances between the rake teeth may be adjustable to account for different requirements. 
     While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.