Patent Publication Number: US-2010108304-A1

Title: Heat exchanger and method of assembling same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Priority is hereby claimed to German Patent Application No. DE 10 2008 021 544.9 filed on Apr. 30, 2008, German Patent Application No. DE 10 2007 032 211.0 filed on Jul. 11, 2007, and German Patent Application No. DE 10 2007 032 015.0 filed on Jul. 10, 2007, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present invention relates to heat exchangers for vehicles and the manufacturing process therefor. 
     A conventional manufacturing method is shown in German Patent Application No. DE 10 2006 002 627.6. In this application, which has not yet been published, injection openings are provided for the bonding agent to be injected into the space around flat tube ends. 
     DE 38 09 944 C2 also discloses injection openings for applying the bonding agent in a heat exchanger. However, this document does not state whether a brazed flat tube and fin core is to be used. The manufacturing step of applying the bonding agent through injection openings is considered disadvantageous because it is not possible to monitor whether the bonding agent is introduced in a way which is compatible with quality requirements. In addition, a suitable backup solution is desirable. 
     WO 2007/009588 discloses a heat exchanger and a method of manufacturing the heat exchanger. The method disclosed does not provide for the flat tube ends to be bonded but instead provides for the flat tube ends to be plugged through openings in a plastic insertion plate and for the flat tube ends to be bent over onto the opening edges of the aforementioned insertion plate. This method is also considered undesirably complex due to the necessary shaping step. 
     SUMMARY 
     The present invention provides a manufacturing process for a heat exchanger, in particular for motor vehicles, having a flat tube and fin core. The flat tube and fin core is formed in such a way that free flat tube ends are provided. The flat tube and fin core is brazed in a brazing furnace, and the flat tube ends are attached in receptacle openings of a header using a bonding agent or a sealing compound which is placed in a space around the flat tube ends. 
     One independent object of the present invention is to provide a cost-effective heat exchanger while improving the quality of the connections formed by a bonding material or agent. 
     For example, in some embodiments, the present invention provides a mounting plate with receptacle openings for receiving flat tube ends. A bonding agent can be applied to the mounting plate or to a header. The mounting plate and the header can form an enclosed space specifically for receiving the bonding agent. The enclosed space can provide a space at least partially defined by parts of the mounting plate and of the header. However, in alternate embodiments, the enclosed space can be connected to relatively small openings (e.g., venting openings or monitoring bores) for allowing the bonding agent to exit therethrough. 
     The step of applying the bonding agent can be carried out with a metered or predetermined quantity of bonding agent being applied to the mounted plate. The mounting plate is then connected to the header for pressing the bonding agent within the enclosed space. In some embodiments, the present invention provides that if the volume of the enclosed space is fixed, then the necessary quantity of bonding agent is also fixed. In some embodiments, the bonding agent partially fills the enclosed space. In other words, when the header is connected to the mounting plate, the amount of bonding agent is sufficient to leave a void within the enclosed space. In other embodiments, the bonding agent is sufficient to fill the enclosed space in an optimum way after the header is connected to the mounting plate. The bonding agent can be a commercially available bonding agent and can be injected into the enclosed space by, for example, injection needles. 
     The receptacle openings in the mounting plate and in the header are configured such that the openings can tightly receive the flat tube ends. In some embodiments, the mounting plate is first fitted onto the flat tube ends, wherein the tube ends can be simultaneously calibrated or newly aligned because the tube ends may have become distorted during the brazing process for forming the flat tube and fin core. 
     Because the receptacle openings of the header are intended to bear closely against the outer surfaces of the flat tubes, the enclosed space for receiving the bonding agent does not extend to the tube ends. Instead, the tube ends bear closely against the wall forming the receptacle openings of the header so that the bonding agent is restricted from flowing into the interior of the header. In addition, the enclosed space also extends only as far as the receptacle openings of the mounting plate so that the bonding agent is restricted from flowing therethrough. The bonding agent, which is preferably a pasty compound, can be satisfactorily applied on an arcuate or circumferentially shaped channel constructed between openings of the mounting plate. Other embodiments of the heat exchanger include a cup-shaped mounting plate. 
     The present invention also provides a mounting plate with receptacle openings to be connected to a header to form an enclosed space therebetween. Furthermore, a bonding agent can be injected into the enclosed space subsequent to the assembly of the header and mounting plate. In addition, venting of the enclosed space is permitted such that the enclosed space can be filled with the bonding agent to an optimum degree. To this end, at least one venting opening and at least one injection opening can be provided by the header and/or mounting plate. The size and number of the venting openings and injection openings can depend on the consistency of the bonding agent and manufacturing parameters of the headers and mounting plates. Therefore, the size and number of such openings can be selected in such a way that the openings provide optimum functionality during assembly of the heat exchanger. 
     Alternatively or in addition, the mounting plate and the header of the heat exchanger can be connected as a single unit with a clamping device. In some such embodiments, the heat exchanger remains under tension until the bonding agent is injected. However, it is also possible for the mounting plate to be held together with the header by elastic clamps or the like, where the clamps are located or integrally formed on one of the header and the mounting plate after applying the bonding agent. 
     In some embodiments, the invention provides a method of manufacturing a heat exchanger for motor vehicle applications. The method can include the acts of forming a flat tube and fin core with tube ends extending from the core, mounting a mounting plate onto the flat tube and fin core, connecting a header to the mounting plate and flat tube and fin core, such that a substantially enclosed space is defined between the header and mounting plate around a portion of at least one of the tube ends, and applying a bonding agent to the enclosed space for connecting the header, mounting plate and tube ends. 
     In other embodiments, the invention provides a heat exchanger for motor vehicle applications. The heat exchanger includes a flat tube and fin core having a number of tube ends extending from the core, a mounting plate connected to the flat tube and fin core adjacent to the tube ends, and a header connected to the mounting plate and adjacent to the tube ends, the mounting plate and the header forming an enclosed space around a portion of at least one of the tube ends for receiving a bonding agent connecting the header, mounting plate and tube ends. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a heat exchanger according to a first embodiment of the present invention. 
         FIG. 2  is a partial cross section of the heat exchanger of  FIG. 1  specifically illustrating a header and flat tube ends of the heat exchanger. 
         FIG. 3  is a cross section taken along A-A. 
         FIG. 4  is a partial cross section of the heat exchanger of  FIG. 1  specifically illustrating an intermediate stage of a manufacturing process for forming the heat exchanger. 
         FIG. 5  is a detailed view of a portion of a mounting plate of the heat exchanger of  FIG. 1 . 
         FIG. 6  is a partial cross section of a heat exchanger according to a second embodiment of the present invention particularly illustrating a partial longitudinal section of the heat exchanger. 
         FIG. 7  is a detailed view of a portion of a mounting plate of the heat exchanger of  FIG. 6 . 
         FIG. 8  illustrates a first intermediate stage of a manufacturing process for forming a heat exchanger according to the present invention. 
         FIG. 9  illustrates a second intermediate stage of the manufacturing process of the present invention. 
         FIG. 10  illustrates a third intermediate stage of the manufacturing process of the present invention. 
         FIG. 11  is a cross section of a flat tube of a heat exchanger according to the present invention. 
         FIG. 12  is a partial cross section of a heat exchanger according to a third embodiment of the present invention particularly illustrating a partial longitudinal section of the heat exchanger. 
         FIG. 13  illustrates a detailed view of a portion of a mounting plate of the heat exchanger in  FIG. 12 . 
         FIG. 14  illustrates the mounting plate of  FIG. 13  with a boding agent. 
         FIG. 15  illustrates an alternate embodiment of a mounting plate of a heat exchanger according to the present invention. 
         FIG. 16  is a detailed view of a portion of the mounting plate of  FIG. 15 . 
         FIG. 17  illustrates a heat exchanger according to a fourth embodiment of the present invention. 
         FIG. 18  is an exploded view of a portion of the heat exchanger of  FIG. 17 . 
         FIG. 19  is a partial cross section of the heat exchanger of  FIG. 17  particularly illustrating a longitudinal cross section of the heat exchanger. 
         FIG. 20  is another partial cross section of the heat exchanger of  FIG. 17  particularly illustrating one alternate embodiment of the heat exchanger. 
         FIG. 21  is another cross section of the heat exchanger in  FIG. 17  particularly illustrating another alternate embodiment of the heat exchanger. 
     
    
    
     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 embodiment 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. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       FIG. 1  illustrates a heat exchanger  10  according to some embodiments of the present invention. The heat exchanger  10  is a coolant cooler particularly suitable for motor vehicle applications. However, the heat exchanger  10  can have applications other than those described in this application. 
     The method of forming a flat tube and fin core  15  of the heat exchanger  10  includes alternatively pre-treating flat tubes  20  and fins  25  and brazing the flat tubes  20  and fins  25  (by a brazing process in a furnace, for example). The flat tubes  20  and the fins  25  can be manufactured from braze-coated, relatively thin sheet aluminum. For example, the thickness of the aluminum sheet can be between about 0.03 mm and about 0.15 mm. In other embodiments, the heat exchanger  10  can include tubes  20  and/or fins  25  of different materials and having a different range of sheet thickness. 
       FIG. 11  illustrates a cross section of one exemplary flat tube  20  of the heat exchanger  10 . However, the following description of the flat tube  20  is also applicable to alternate heat exchangers described in this application. As illustrated in  FIG. 11 , the flat tube  20  includes first, second and third sheet metal strips  30 ,  35  and  40 . More specifically, first and second sheet metal strips  30  and  35  are shaped to form the outer wall of the flat tube  20  and the third sheet metal strip  40  is shaped to form a corrugated internal insert of the flat tube  20 . The insert  40  is manufactured from a relatively thinner sheet metal strip in comparison to the first and second sheet metal strips  30  and  35 , which form the walls of the flat tube  20 . Narrow sides  45  of the flat tube  20  are reinforced by overlapping the longitudinal edges of the first and second sheet metal strips  30  and  35  and additionally by folding the longitudinal edges of the internal insert  40  to nest the folded longitudinal edges inside of the overlapped longitudinal edges of the first and second sheet metal strips  30  and  35 . It is to be understood that the flat tube  20  illustrated herein is only an exemplary embodiment. Further, other embodiments of the flat tube  20  fall within the scope of the present invention. 
     With reference to  FIG. 1 , the heat exchanger  10  further includes headers  50  and mounting plates  55  cooperating to at least partially support the flat tube and fin core  15 . Each header  50  is sealingly connected to a corresponding mounting plate  55 . The headers  50  include inlet/outlet apertures  60  for directing the flow of a suitable fluid through the heat exchanger  10 . In the illustrated embodiment, the headers  50  and mounting plates  55  are formed of a plastic material. Because both headers  50  and mounting plates  55  are manufactured from plastic material, the weight of the heat exchanger  10  is relatively low in comparison to heat exchangers having metal headers. This allows the heat exchanger  10  to meet or exceed the latest weight requirements in the automobile industry. Furthermore, the heat exchanger  10  can also or alternatively meet or exceed current industry requirements in terms of the heat exchanging properties. It is to be understood that the header  50  can be embodied in one or more parts formed of a plastic material, which can then be fused. Accordingly, the term “header” encompasses a header part (e.g., header  50 ) including one or more individual parts. 
       FIGS. 8-10  illustrate intermediate stages of the manufacturing process of the heat exchanger  10 . However, the intermediate stages and/or steps related to the process described in relation to  FIGS. 8-10  are also applicable to alternate heat exchangers described in this application. With reference to  FIGS. 2 ,  3  and  8 , each of the mounting plates  55  includes a peripheral side wall  70 , an inner surface  72  facing the header  50 , an outer surface  74  facing the flat tube and fin core  15  and a number of elongated openings  75 . Each of the elongated openings  75  is operable to receive one corresponding tube end  65  of the flat tube and fin core  15 . An alternate mounting plate  655  is illustrated  FIGS. 15 and 16 . Similar to the mounting plate  55 , the mounting plate  655  includes a peripheral side wall  670 , an inner surface  672 , an outer surface  674  and a number of elongated openings  675 . However, the side wall  670  includes two flat sides  671  formed at the longitudinal ends of the mounting plate  655  and two corrugated sides  672  formed along the length of the mounting plate  655 . In addition, the inner surface  672  is substantially flat and the openings  675  are defined by flange-like or bent edges  676 . 
       FIGS. 2 and 3  illustrate a stage of the manufacturing process of the heat exchanger  10  in which the mounting plate  55  has been fitted onto the flat tube ends  65 . During the brazing process for forming the flat tube and fin core  15 , the flat tubes  20  and/or fins  25  may become deformed and fitting the mounting plate  55  onto the tube ends  65  can realign the tube ends  65 . As illustrated in  FIGS. 2-5 , the openings  75  include chamfered edges  80  to ease the insertion of the tube ends  65  through the openings  75 . In the illustrated embodiment, the mounting plates  55  are connected to the flat tube and fin core  15  such that each mounting plate  55  is fitted tightly against the fins  25  of the flat tube and fin core  15 . 
     A bonding agent  85 , schematically illustrated with a circular cross section in  FIG. 4  or with dashed lines in  FIG. 5 , is applied to the inner surface  72  of the mounting plate  55 . The bonding agent  85  may be silicone-based and may be a commercially available product. However, other embodiments of the heat exchanger  10  can include other types of bonding agents. The bonding agent  85  can be applied to the mounting plate  55  prior to connecting the mounting plate  55  to the flat tube and fin core  15  ( FIG. 8 ) or subsequent thereto ( FIG. 9 ). In the illustrated embodiment, the inner surface  72  defines a number of elongated channels  90 . Each channel  90  is further defined between two elongated openings  75  and extends along the width of the mounting plate  55 . Accordingly, the bonding agent  85  is placed on the channels  90  for ease of the forming process of the heat exchanger  10 . In the illustrated embodiment, the channels  90  do not extend around the narrow areas of the inner surface  72  defined mainly between the ends of the openings  75  and the peripheral wall  70  of the mounting plate  55 . 
     Subsequent to applying the bonding agent  85 , the header  50  is fitted onto the corresponding mounting plate  55 , as illustrated in  FIGS. 2 ,  3  and  10 . The header  50  includes an outer wall  100  and an inner structure  105  joining the two ends of the outer wall  100 . In the illustrated embodiment, the inner structure  105  is integrally formed with the outer wall  100  and defines a number of receptacle openings  95  for receiving the tube ends  65  of the flat tube and fin core  15 , a number of elongated projections  110  each between two openings  95 , and a projection  115  with a shoulder  120  for engaging the peripheral side wall  70  of the corresponding mounting plate  55 . 
     Upon engagement of the header  50  with the corresponding mounting plate  55  and tube ends  65  ( FIGS. 2 ,  3  and  10 ), the projections  110  engage corresponding channels  90 , distributing the bonding agent  85  thereon. Concurrently, the tube ends  65  are received in corresponding receptacle openings  95  of the header  50 . In the illustrated embodiment, the tube ends  65  do not project into the interior (also known and the tank portion) of the header  50 . For this reason only a relatively small pressure loss occurs during operation of the heat exchanger  10 . Engagement of the headers  50  with corresponding mounting plates  55  and tube ends  65  forms a number of enclosed spaces  125  therebetween. Particularly, each enclosed space  125  is defined by the inner surface of the projections  110  of the header  50 , the inner surface  72  of the mounting plate  55  and a portion of the outer surface of the tube ends  65 . 
     In some embodiments, the quantity of the bonding agent  85  is calculated such that the bonding agent  85  redistributed by engagement of the projections  110  with corresponding channels  90  fills a portion of each of the enclosed spaces  125 , thus leaving a void within each of the enclosed spaces  125 . In another embodiment, the quantity of bonding agent  85  is precisely calculated and is perhaps slightly more than the volume of the enclosed spaces  125 . Accordingly, the bonding agent  85  redistributed by engagement of the projections  110  with the corresponding channels  90  entirely fills the enclosed spaces  125 .  FIGS. 2 and 3  illustrate the enclosed space  125  in a closed state. However, other embodiments of the heat exchanger  10  can include openings defined by the headers  50  and/or mounting plates  55  to allow bonding agent  85  therethrough to relieve pressure. 
     In the illustrated embodiment of  FIGS. 2 and 3 , the tube ends  65  are tightly received within the openings  95 . Therefore, the tube ends  65  are not part or do not define the enclosed spaces  125 . Further, the bonding agent  85  is prevented from passing through the engagement between the tube ends  65  and the walls defining the openings  95  and into the interior of the header  50 . Similarly, the bonding agent  85  is prevented from passing through the engagement between tube ends  65  and inner walls of the openings  75  of the mounting plates  55 . As illustrated in  FIG. 2 , the enclosed space  125  for receiving the bonding agent  85  extends around the narrow sides  45  of the flat tubes  20 . In the illustrated embodiment, there is no provision for a bonding connection between the longitudinal edges of the header  50  and the mounting plate  55 . On the contrary, the projection  115  cooperates with the inner edge of the peripheral side wall  70  of the mounting plate  55  for preventing bonding agent  85  from flowing therebetween. Further functions of the projection  115  are to define or limit the depth at which the header  50  is connected to the mounting plate  55  ( FIG. 2 ), and also to ensure better overall stability of the header  50  and mounting plate  55 . 
     With reference to  FIG. 1 , the heat exchanger  10  includes side parts  101  for, among other things, relieving loading of the bonded connections of the tube ends  65 . The side parts  101  are two sheet metal strips arranged to the left and right sides of the flat tube and fin core  15  and connected to the headers  50  that are also on opposite sides of the flat tube and fin core  15 . Generally, the side parts  101  are fitted on or connected to the flat tube and fin core  15  before brazing the flat tubes  20  and fins  25  together. In the illustrated embodiment, the side parts  101  are approximately 1.0 mm thick and therefore thinner than other side parts used in conventional heat exchangers. It is to be understood that the side parts  101  are optional and that the bonded connections between the headers  50 ,  250 ,  450 , corresponding mounting plates  55  and tube ends  65  are sufficiently durable to support the operation of the heat exchanger  10 . It is to be understood that the principles and features described above with respect to the heat exchanger  10  are also applicable to other heat exchangers described in this application. 
       FIGS. 6 and 7  illustrate a heat exchanger  210  according to an alternate embodiment including, among other things, a header  250  and a mounting plate  255 . The heat exchanger  210  employs much of the same structure and has many of the same properties as other heat exchangers described in this application. Accordingly, the following description focuses primarily upon the structure and features that are different than the other heat exchangers described in this application. Reference should be made to the description in connection with the other heat exchangers described in this application for additional information regarding the structure and features, and possible alternatives to the structure and features of the heat exchanger  210  illustrated in  FIGS. 6 and 7  and described below. Structure and features of the heat exchanger  210  shown in  FIGS. 6 and 7  that correspond to structure and features of the other heat exchangers described in this application are designated hereinafter in respective two and three hundred series of reference numbers. 
     As illustrated in  FIGS. 6 and 7 , channel  290  is made significantly deeper than the previously described channel  90  and also extends around elongated openings  275  of the mounting plate  255 . Accordingly, upon engagement of the header  250  with mounting plate  255  and end tubes  265 , the channel  290  extends around the narrow side  245  of the flat tubes  220 . With particular reference to  FIG. 6 , the channel  290  receives an elongated portion  311  of the projection  310  of the header  250 . The projection  310  with elongated portion  311  is adapted or formed to conform to the deeper channel  290 . Accordingly, each enclosed space  325  is substantially defined by the portion of the inner surface  272  forming the channel outer wall of the mounting plate  255 , and not by the border of the receptacle openings  295  of the header  250 , as in the embodiment of the heat exchanger  10  described above with respect to  FIGS. 1-5 . 
       FIGS. 12-14  illustrate a heat exchanger  410  according to an alternate embodiment including, among other things, a header  450  and a mounting plate  455 . The heat exchanger  410  employs much of the same structure and has many of the same properties as other heat exchangers described in this application. Accordingly, the following description focuses primarily upon the structure and features that are different than the other heat exchangers described in this application. Reference should be made to the description in connection with the other heat exchangers described in this application for additional information regarding the structure and features, and possible alternatives to the structure and features of the heat exchanger  410  illustrated in  FIGS. 12-14  and described below. Structure and features of the heat exchanger  410  shown in  FIGS. 12-14  that correspond to structure and features of the other heat exchangers described in this application are designated hereinafter in respective four and five hundred series of reference numbers. 
     As illustrated in  FIGS. 12-14 , the embodiment of the mounting plate  455  differs from the previously described mounting plates  55 ,  255  in that the mounting plate  455  has a cup-shaped design with a predominantly circumferential peripheral side wall  70 . It is to be noted that  FIGS. 12-14  only illustrate one end of the mounting plate  455 . However, the mounting plate  455  extends over approximately the entire length of the flat tube and fin core  415 . In the illustrated embodiment, the mounting plate  455  is formed of a plastic material with a thickness of about 1 mm or less. In the illustrated embodiment, the mounting plate  455  does not provide alignment for the tube ends  465 , as described above with respect to mounting plates  55 ,  255 . Another difference with the previously described mounting plates  55 ,  255  is that no channel is formed. The mounting plate  455  is of a substantially flat design, apart from the circumferential, upright side wall  475 . 
     Further, the enclosed space  525  formed as a result of the engagement between the header  450  and corresponding mounting plate  455  and end tubes  465  is not entirely filled with bonding agent  485 . With particular reference to  FIG. 12 , a relatively small upper portion of the space  525  remains substantially free of bonding agent, forming a void  526  within the space  525 . Forming such a void  526  helps avoid stresses and/or strains in or caused by the bonding agent  525 . In order to securely position the mounting plate  455 , the latter is let into, for example, groove-like depressions  416  in the header  450 . The inventors have found that the quality of the bonded connection between the header  450  and the mounting plate  455  improves significantly if there is no flux in the bonding area. 
       FIGS. 17-21  illustrate a heat exchanger  810  according to another embodiment of the present invention. The heat exchanger  810  employs much of the same structure and has many of the same properties as other the heat exchangers described in this application. Accordingly, the following description focuses primarily upon the structure and features that are different than the other heat exchangers described in this application. Reference should be made to the description of the other heat exchangers described in this application for additional information regarding the structure and features, and possible alternatives to the structure and features of the heat exchanger  810  illustrated in  FIGS. 17-21  and described below. Structure and features of the heat exchanger  810  shown in  FIGS. 17-21  that correspond to structure and features of the other heat exchangers described in this application are designated hereinafter in respective eight and nine hundred series of reference numbers. 
     The heat exchanger  810  is a coolant cooler particularly suitable for motor vehicle applications. However, the heat exchanger  810  can have applications other than the ones described in this application. 
     The method of forming a flat tube and fin core  815  of the heat exchanger  810  includes alternatively pre-treating flat tubes  820  and fins  825  and brazing the flat tubes  820  and fins  825  (by a brazing process in a furnace, for example). The flat tubes  820  and the fins  825  are manufactured from braze-coated, relatively thin sheet aluminum. For example, the sheet metal thickness of the aluminum sheet can range between about 0.03 mm and about 0.15 mm. In other embodiments, the heat exchanger  810  can include tubes  820  and/or fins  825  of different materials and having a different sheet thickness. 
     With reference to  FIG. 17 , the heat exchanger  810  further includes headers  850  and mounting plates  855  cooperating to at least partially support the flat tube and fin core  815 . Each header  850  is sealingly connected to a mounting plate  855 . The headers  850  include inlet/outlet apertures  860  for directing the flow of a suitable fluid through the heat exchanger  810 . In the illustrated embodiment, the headers  850  and mounting plates  855  are formed of a plastic material. Because both headers  850  and mounting plates  855  are manufactured from plastic material, the weight of the heat exchanger  810  is relatively low in comparison to conventional heat exchangers with metal headers. This allows the heat exchanger  810  to meet or exceed the latest weight requirements in the automobile industry. Furthermore, the heat exchanger  810  also meets or exceeds current industry requirements in terms of the heat exchanging properties. It is to be understood that the header  850  can be embodied in one or more parts formed of a plastic material, which can then be fused. Accordingly, the term “header” encompasses a header part (e.g., header  850 ) including one or more parts. 
     With reference to  FIGS. 18-21 , each of the mounting plates  855  includes an inner surface  872  facing the header  850 , an outer surface  874  facing the flat tube and fin core  815 , a number of elongated openings  875  and two venting openings  877 . The venting openings  877  are defined by two grooves formed at opposite edges of the openings  875 . Each of the elongated openings  875  is operable to receive one corresponding tube end  865  of the flat tube and fin core  815 . In the illustrated embodiment, the mounting plate  855  is a plate having a thickness of about or significantly less than 1.0 mm.  FIG. 21  illustrates two alternate aspects of the mounting plate  855  and particularly of the receptacle openings  875 . In the some embodiments, the mounting plate  855  includes beads  811  formed around the openings  875 . The beads  811  correspond to the edges of the enclosed space  925 . More specifically, the beads  811  substantially match or align with the inner surface of an elongated projection  910  to define the enclosed space  920 . In other embodiments, the openings  875  are defined by a flange-like border  912  for providing a relatively tight closure around each tube end  865 . In both aspects of the receptacle openings  875 , the bent or flange-like borders  912  allow simplified insertion of the tube ends  865  through the openings  875  of the mounting plate  855 . 
       FIGS. 19-21  illustrate a portion of the manufacturing process of the heat exchanger  810  wherein the mounting plate  855  has been fitted onto the flat tube ends  865 . During the brazing process for forming the flat tube and fin core  815 , the flat tubes  820  and/or fins  825  may become deformed and fitting the mounting plate  855  onto the tube ends  865  can realign the tube ends  865 . The mounting plates  855  are connected to the flat tube and fin core  815  such that each mounting plate  855  is fitted tightly against the fins  825  of the flat tube and fin core  815 . 
     Subsequent to fitting the mounting plate  855  onto the tube ends  865  of the flat tube and fin core  815 , the header  850  is fitted onto the mounting plate  855 . The header  50  includes an outer wall  900  and an inner structure  905  joining the two ends of the outer wall  900 . In the illustrated embodiment, the inner structure  905  is integrally formed with the outer wall  900  and defines a number of receptacle openings  895  for receiving the tube ends  865  of the flat tube and fin core  815 , a number of elongated projections  910  each including a flat bottom  911  and formed between two openings  995 , and a contact portion or surface  916  for engaging the inner surface  872  of the corresponding mounting plate  855 . 
     Upon engagement of the header  850  with the corresponding mounting plate  855  and tube ends  865  ( FIGS. 19-21 ), the flat bottom  911  of the projections  910  engage the inner surface  872  of the mounting plate  855  as the tube ends  865  are received in the receptacle openings  895  of the header  850 . In the illustrated embodiment, the tube ends  865  do not project into the interior of the header  850 . For this reason, only a relatively small pressure loss occurs during operation of the heat exchanger  810 . Engagement of the headers  850  with corresponding mounting plates  855  and tube ends  865  forms a number of enclosed spaces  925  therebetween. Particularly, each enclosed space  925  is defined by the inner surface of the projections  910 , the inner surface  972  of the mounting plate  955  and a portion of the outer surface of the tube ends  965 . 
     As illustrated in  FIGS. 19-21 , the tube ends  865  are tightly received within the openings  895 . Therefore, the tube ends  865  are not part or do not define the enclosed spaces  925 . Further, a bonding agent  885  is prevented from passing through the engagement between the tube ends  865  and the openings  895  and into the interior of the header  850 . Similarly, the bonding agent  885  is prevented from passing through the engagement between tube ends  865  and inner walls of the openings  875  of the mounting plates  855 , except at the location of the venting openings  877 . In other embodiments, venting openings (similar to openings  877 ) can be formed at other locations of the mounting plate  855  or on the headers  850 . 
     Subsequent to forming the heat exchanger  810 , as illustrated in  FIG. 17 , a bonding agent is injected into the enclosed spaces  925  through injection openings  822 . In the illustrated construction, the injection openings  822  are formed on the side of the header  850  and in substantial alignment with the peripheral edge of the header  850  as schematically illustrated in  FIGS. 17 and 18 . It is to be noted that  FIGS. 17 and 18  only show a few injection openings  822  for exemplary purposes. However, the injection openings  822  can extend throughout the entire length of the header  850 . In the embodiment illustrated in  FIG. 20 , one injection opening  822  is formed in alignment with each of the enclosed spaces  925  formed as a result of connecting the header  850 , mounting plate  855  and tube ends  865 . In the embodiment illustrated in  FIG. 21 , two injection openings  822  are formed in alignment with each of the enclosed spaces  925 . Other embodiments can include a different number of injection openings  822  formed for each of the enclosed spaces  925 . 
     As illustrated in  FIG. 21 , injection needles  950  are inserted into the enclosed space  925  in the direction of the width of the header  850  and through the injection openings  822 . The injection needles  950  are inserted substantially the full length (along the width of the header  850 ) of the enclosed space  925 . Then the bonding agent  885  is inserted into the enclosed spaces  925  through the injection needles  950  as the needles  950  are concurrently retracted outwardly through the injection openings  822  and out of the enclosed space  925 . This process ensures that the enclosed spaces  925  are filled with the bonding agent  885  to an optimum degree. 
     In some embodiments, the quantity of the bonding agent  885  is calculated such that the amount of bonding agent  885  injected into the enclosed space  925  fills a portion of the enclosed space  925 , thus leaving a void within each of the enclosed spaces  925 . In other embodiments, the quantity of bonding agent  885  is precisely calculated and is perhaps slightly more than the volume of the enclosed spaces  925 . Accordingly, the bonding agent  885  injected into the enclosed spaces  925  entirely fills the enclosed spaces  925 . 
     With reference to  FIG. 17 , the heat exchanger  810  includes side parts  901  for the purpose of relieving loading of the bonded connections of the tube ends  865 . The side parts  901  are two sheet metal strips arranged to the left and right sides of the flat tube and fin core  815  and connected to the headers  850  that are also on opposite sides of the flat tube and fin core  815 . Generally, the side parts  901  are fitted on or connected to the flat tube and fin core  815  before brazing the flat tubes  820  and fins  825  together. In the illustrated embodiment, the side parts  901  are about 1.0 mm thick and are therefore thinner than other side parts used in conventional heat exchangers. It is to be understood that the side parts  901  are optional features to the heat exchanger  810  and that the bonded connections between the headers  850 , corresponding mounting plates  855  and tube ends  865  are sufficiently durable to support the operation of the heat exchanger  810 . 
     Various features and advantages of the invention are set forth in the following claims.