Abstract:
A multi-fluid heat exchanger and a method of making the same are provided wherein a cut portion is provided in an elongated header of the heat exchanger at a location between a pair of baffles in the elongated header and first and second cores of the heat exchanger. At least a majority of the transverse cross section of the elongated header is removed at the cut portion to allow for relative thermal growth of the first and second cores.

Description:
FIELD OF THE INVENTION 
   This invention relates to heat exchangers and more particularly to combination-type heat exchangers wherein heat exchangers for two or more fluids share a common manifold or header, and in more particular applications, to such heat exchangers as used in vehicular systems, such as automobiles, buses, trucks, etc. 
   BACKGROUND OF THE INVENTION 
   It is known to form a so-called “combination” or “combo” type heat exchanger by including one or more baffles in each of the manifolds or headers of the heat exchanger to divide the interiors of each of the headers into at least a first section for a first working fluid and a second section for a second working fluid with each of the working fluids being directed through the respective heat exchange tubes that are connected to the respective sections of the common manifolds. While such constructions may be suitable for their intended purposes, problems can arise when there are large temperature differentials between the different working fluids in each section of the shared manifold, particularly for constructions where the cores or tubes for each of the working fluids are assembled in the same plane, such as, for example, in parallel flow constructions. Accordingly, there is a continued need for improvement in combo heat exchangers. 
   SUMMARY OF THE INVENTION 
   The invention reduces the strain on heat exchanger core tubes by sectioning or partially sectioning one or both common headers in a combination type heat exchanger. The invention also allows the heat exchanger to be assembled using conventional methods. The invention provides for the possibilities of cutting the headers during or after core assembly, or after brazing. Cutting can be accomplished by various methods such as sawing or punching. 
   The option of partially sectioning or cutting the header allows the heat exchanger to be installed intact into a system, and have the header sections break apart during thermal events in the vehicle. Also, partially cutting the headers can be done prior to cores assembly, and the final cutting can be done during or after core assembly. 
   In accordance with one form of the invention, a multi-fluid heat exchanger is provided for transferring heat between a first fluid and a common fluid in one part of the heat exchanger and between the second fluid and a common fluid in a second part of the heat exchanger. The heat exchanger includes first and second elongated header pipes, first and second core sections, and a pair of baffles in the first header pipe. The first elongated header pipe has a plurality tube receiving opening spaced along a length of the first header pipe. The second elongate header pipe has a plurality of tube receiving openings spaced along a length of the second header pipe. The first core section includes a plurality of parallel, spaced tubes, each of the tubes having a first end and a second end, with the first end received in a corresponding one of the tube receiving openings of the first header pipe and the second end received in a corresponding one of the tube receiving openings of the second header pipe to direct the first fluid between the first and second header pipes through an interior of the tube. The second core section comprising a plurality of parallel, spaced tubes, each of the tubes having a first end and a second end, with the first end received in a corresponding one of the tube receiving openings of the first header pipe and the second end received in a corresponding one of the tube receiving openings of the second header pipe to direct the second fluid between the first and second header pipes through an interior of the tube. The second core is spaced from the first core along the lengths of the first and second header pipes. The pair of baffles are located in the first header pipe at a location between the first and second cores to divide an interior of the first header pipe into a first fluid manifold for the first fluid and a second fluid manifold for the second fluid. The first header pipe includes a cut portion located between the pair of baffles, the cut portion having at least a majority of a transverse cross section of the header pipe removed in comparison to the immediately adjacent transverse cross sections of the first header pipe. 
   In one feature, the cut portion is sized so that any remaining part of the transverse cross section of the first header pipe at the cut portion is severed under thermal cycling of the heat exchanger during operation of the heat exchanger. 
   As one feature, all of the transverse cross section of the first header pipe has been removed in the cut portion, so that the first header pipe is separated into two unconnected pieces. 
   In accordance with one feature, one of the tube openings of the first header pipe is located at the cut portion. 
   In a further feature, the one of the tube openings of the first header pipe doe not have a tube end received therein. 
   According to a further feature, the cut portion is defined by at least one saw cut extending through a portion of the header pipe outside of the one of the tube openings. 
   As a further feature, the cut portion is defined by a saw cut extending through a side of the header pipe immediately opposite from the one of the tube openings. 
   In accordance with a further feature, the cut portion is defined by a saw cut extending through the one of the tube openings. 
   In one feature, the cut portion is defined by a pair of saw cuts extending through opposite respective sides of the first header pipe. 
   According to one feature, the cut portion is characterized by the absence of any of the tube openings. 
   In one feature, there is a serpentine fin extending between the first and second cores and connected to both the first and second cores. 
   As one feature, the heat exchanger includes another pair of baffles located in the second header pipe at a location between the first and second cores to divide an interior of the second header pipe into a first fluid manifold for the first fluid and a second fluid manifold for the second fluid, the second header pipe including a second cut portion located between the another pair of baffles, the second cut portion having at least a majority of a transverse cross section of the header pipe is removed in comparison to the immediately adjacent transverse cross sections of the first header pipe. 
   In accordance with one feature of the invention, a method is provided for making a multi-fluid heat exchanger for transferring heat between a first fluid and a common fluid in one part of the heat exchanger and between a second fluid and the common fluid in a second part of the heat exchanger. The method includes the steps of: 
   a) providing a heat exchanger with first and second parallel flow core sections extending between a pair of elongated header tubes, with each of the tubes having a first fluid manifold for the first core section and a second fluid for the second core section; 
   b) providing a cut portion in one of the elongated headers at a location between the first and second manifolds, the cut portion having at least part of the header connecting the first and second manifolds of the header; 
   c) thermal cycling the heat exchanger to severe the at least part of the one of the elongated headers so that the first and second manifolds of the header are no longer connected at the cut portion. 
   As one feature, step b) includes providing the cut portion after the first and second core seconds are assembled and brazed together with the pair of elongated headers. 
   As another feature, step b) includes providing the cut portion before the first and second core seconds are assembled and brazed together with the pair of elongated headers. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1-5B  are views of a combo heat exchanger including a thermal relief mechanism embodying the present invention; and 
       FIGS. 6A-11C  are views of alternate embodiments of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a portion of a combination cooler embodying a multi-fluid heat exchanger of the present invention. The combo cooler  10  includes a common manifold or header  12  in the form of an essentially cylindrical tube that has pierced tube slots  14  to receive the flattened heat exchanger tubes  16  and  18 , respectively, that direct their respective first and second heat exchange fluids through the combo heat exchanger  10  so that heat can be transferred between the first and second working fluids to a third fluid, typically air, that flows over the exterior of the tubes  16 , 18  and passes through a plurality of serpentine fins  20  that are positioned between adjacent pairs of the tubes  16  and  18 . The manifold  12  includes a first section  22  for the first fluid and a second section  24  for the second fluid, with the first and second sections being separated by a pair of baffles  26  and  28  that have been inserted through cut baffle slots  30  in the manifold  12  and brazed in place during the common brazing operation that brazes all of the tubes  16 , 18 , fins  20 , and headers  12  together. A saw cut  32  is located between the baffles  26  and  28  at the location of a pierced tube slot  14 A. The cut  32  is created after the remainder of the heat exchanger  10  has been assembled and brazed together. This saw cut  32  is further illustrated in  FIGS. 5A and 5B , and the full heat exchanger is shown in  FIGS. 2-4 . As best seen in  FIG. 2 , in some applications it may be desirable to include the saw cut  32  in only one of the headers  12 . 
     FIGS. 6A-6B ,  7 A- 7 B,  8 A- 8 B,  9 A- 9 B,  10 A- 10 B, and  11 A- 11 C show alternate embodiments to the saw cut of  FIGS. 1-5B . 
   More specifically,  FIGS. 6A and 6B  show an alternate embodiment wherein a partial saw cut  34  extends from the side of the manifold  12  opposite the tube slots  14  so as to leave a pair of connection tabs  36  that extend between the tube slot  14 A and the saw cut  34 . 
     FIGS. 7A and 7B  show an alternate embodiment wherein a partial saw cut  38  is made on the same side of the manifold as the tube slots  14 A so as to leave a circumferential connection tab  40  on the side of the manifold  12  opposite from the tube slots  14 . 
     FIGS. 8A and 8B  show an optional embodiment wherein the manifold  12  includes a pair of saw cuts  42  and  44  that are made on each side of the manifold adjacent the pierced tube slot  14 A and extend all the way into the slot  14 A so as to remove all of the material except for a circumferential connecting tab  46  on the opposite side of the manifold  12  from the tube slots  14 . 
     FIGS. 9A and 9B  show an optional embodiment wherein the manifold  12  does not include a pierced tube slot  14 A at the location between the baffles  26  and  28 , but does include a baffle slot  48  that is of the same type as the slots  30  used for the baffles  26  and  28 , and which leaves a pair of connection tabs  50  on each side of the manifold  12 . 
     FIGS. 10A and 10B  show an alternate embodiment similar to that of  FIGS. 9A and 9B , but where the manifold  12  does include a pierced tube slot  14 A at the location of the cut baffle slot  48 . 
     FIGS. 11A ,  11 B and  11 C show yet another alternate embodiment wherein the manifold  12  includes a pierced tube slots  14 A and has saw cuts  52  on each side similar to the embodiment of  FIGS. 8A and 8B , but the saw cuts  52  do not extend into the tube slot  14 A, thereby leaving the connection tab  46  and a pair of side tabs  54 . 
   For each of the foregoing embodiments that include one or more connection tabs, the heat exchanger  10  can be installed intact, i.e., with the first and second sections  22  and  24  connected together by the connection tabs, and then the header sections  22  and  24  can be separated during operation by thermal stresses that result in the structural failure of the connection tabs. 
   It should be appreciated that the tubes  16 , and preferably the associated fins  20 , define a core section  60  for the cooler  10 , and the tubes  18 , and preferably the associated fins  20 , define another core section  62  of the combo cooler  10 . It should also be appreciated that the saw cuts  32 , 34 , 38 , 42 , 44 , 52  and cut baffles slots  48  of each of the foregoing embodiments define a cut portion  64  in the corresponding manifold of the embodiment that is located between the pair of baffles  26  and  28 . It can also be seen in the figures that, for each of the previously described embodiments, at least a majority of the transverse cross section of the header  12  has been removed at the cut portion  64  in comparison to the immediately adjacent transverse cross sections of the header  12 . 
   While the above embodiments have been shown for a combination cooler wherein the common manifold has only first and second sections, the invention may prove useful in applications wherein there are more than two sections in the common manifold  12  and therefore more than two of the saw cuts  32 , or the alternate embodiments thereto, in each of the manifolds  12 .