Patent Publication Number: US-2006005940-A1

Title: Heat exchanger with bypass seal

Description:
FIELD OF INVENTION  
      This invention relates generally to the field of heat exchangers and, more particularly, to heat exchangers that are specifically configured to include a bypass seal disposed internally therein to maintain the separation of heat exchanger inlet and outlet flow within the heat exchanger, thereby improving heat exchanger operation efficiency.  
     BACKGROUND OF THE INVENTION  
      The present invention relates to heat exchangers that are generally configured having one or more manifold members that are constructed to receive and/or dispense a particular fluid or gas in need of cooling, and a core member that is connected to the manifold members to receive the fluid or gas in need of cooling by conductive and convective heat transfer. The heat exchanger can also include one or more manifold members constructed to receive and/or dispense a particular cooling fluid or gas, that are placed into contact with the core member. Such heat exchangers known in the art can be configured having a single or multiple pass hot-side or cold-side designs.  
      The core member is typically configured to provide a desired degree of heat transfer. Generally, the core comprises a plurality of hollow heat transfer passages that are provided in number sized and position to permit a desired degree of fluid or gas flow therethrough. These heat transfer passages may also be configured having extended inside or outside surfaces that are specially designed to promote desired heat transfer.  
      Referring to  FIG. 1 , a particular type of heat exchanger  10  known in the art is a shell and tube heat exchanger that comprises a shell  12  or body that surrounds the core  14 . For purposes of clarity and reference, the core is illustrated with only two passages instead of being fully loaded with a plurality of passages. In a two-pass heat exchanger design, the manifold  16  is attached to one end  18  of the shell and includes both an inlet opening  20  and an outlet opening  22 . This type of heat exchanger is used in applications such as for cooling exhaust gas from an internal combustion engine using an exhaust gas recirculation system.  
      In this example, the core includes a first end  24  that is positioned adjacent the manifold and a second end  26  that is positioned adjacent a closed end  28  of the shell  12 . The manifold  16  includes a divider wall  30  that operates to form separate inlet and outlet passages  32  and  34  therein. Hot exhaust gas entering the manifold inlet passes into openings in the first end  24  of the core that are in communication with the manifold inlet passage  32 , exits the second end  26  of the core, is directed into passage openings in the core second end that are in communication with the manifold outlet passage  34 , and is passed for a second time through the core. As this occurs, the gas traveling through the core is cooled by contact that is made between a cooling medium circulated within the shell and the core. The exhaust gas then exits the core first end  24  through passage openings that are in communication with the manifold outlet passage, and is routed out of the heat exchanger via the exhaust outlet opening  22 .  
      A problem known to exist in heat exchangers configured in the manner described above involves the existence of undesired gas flow bypass within the heat exchanger between the gas inlet and gas outlet streams; specifically, gas bypass that occurs within the manifold gas inlet and gas outlet passages by virtue of a gap that exists between the manifold divider wall and the core. Past attempts at addressing this situation have involved the use of an elastomeric seal between the divider wall and the core. However, the use of such elastomeric seals have not proven effective due to the high operating temperatures that exist within the manifold, which can exceed 315° C. metal temperature. Such internal exhaust gas bypass is undesired as it can adversely impact heat exchanger operating efficiency. If the divider wall is structurally attached to the core, for example by welding or brazing, destructive thermal stresses may arise, reducing heat exchanger life  
      It is, therefore, desired that a heat exchanger be constructed in a manner that reduces or eliminates unwanted internal bypass of inlet and outlet gas therein. Is desired that such heat exchanger be constructed in a manner that permits the use of existing heat exchanger parts or elements with minimal if any modification. It is further desired that such heat exchanger be constructed in a manner that neither adversely impacts other heat exchanger performance properties, nor adversely impacts construction by using materials and methods that are readily available to facilitate cost effective manufacturing and assembly of the same.  
     SUMMARY OF THE INVENTION  
      Heat exchangers constructed in accordance with this invention comprise a core having a plurality of passages arranged therein that can be configured to provide multi-pass flow of gas or fluid therein. The plurality of passages each have openings positioned adjacent an end portion of the core.  
      A manifold is positioned adjacent the core end portion and includes a gas or fluid inlet and a gas or fluid outlet. The manifold further includes a divider wall that extends internally therein forming a gas or fluid inlet passage that is in communication with the gas or fluid inlet, and forming a gas or fluid outlet passage that is in communication with the gas or fluid outlet and that is separate from the inlet passage.  
      The heat exchanger further includes a metallic seal interposed between the divider wall and the core end portion to provide a seal therebetween. The metallic seal is configured to create a biasing force between the divider wall and core when the manifold and core are assembled together. The biasing force operates to provide the desired seal between the manifold and core to minimize or prevent the unwanted bypass of fluid or gas within the manifold during heat exchanger operation, thereby increasing heat exchanger operating efficiency. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be more clearly understood with reference to the following drawings wherein:  
       FIG. 1  is a cross-sectional view of a prior art heat exchanger;  
       FIG. 2  is a top view of a manifold portion of the heat exchanger from  FIG. 1 ;  
       FIG. 3  is a cross-sectional view of a manifold portion of a heat exchanger of this invention comprising a bypass seal according to a first invention embodiment;  
       FIG. 4  is a cross-sectional view of a manifold portion of a heat exchanger of this invention comprising a bypass seal according to a second invention embodiment;  
       FIG. 5  is a cross-sectional view of a manifold portion of a heat exchanger of this invention comprising a bypass seal according to a third invention embodiment; and  
       FIG. 6  is a cross-sectional view of a manifold portion of a heat exchanger of this invention comprising a bypass seal according to a fourth invention embodiment.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention relates to heat exchangers used for reducing the temperature of an entering gas or fluid stream. The particular application for the heat exchangers of the present invention is with vehicles and, more particularly, to cool an exhaust gas stream in an exhaust gas recirculation (EGR) system, or to cool a pressurized air intake stream in a turbocharged or supercharged engine system. However, it will be understood that this is only an exemplary embodiment. It will be readily understood by those skilled in the relevant technical field that the heat exchanger configurations of the present invention described herein can be used in a variety of applications.  
      Generally, the invention involves use with heat exchangers that are similar to that described above and as illustrated in  FIG. 1  having a shell and tube design.  
      As mentioned above, the core includes a plurality of passages or tubes disposed therein and can be referred to as a tube bundle. The core comprises a plurality of passage openings positioned adjacent the shell open end  18  when the core is disposed within the shell. The core passages positioned in communication with the manifold inlet passage facilitate a first pass of exhaust gas through the core, and the core passages positioned in communication with the manifold outlet passage facilitate a second pass of exhaust gas through the core.  
      The shell includes a cooling inlet port (not shown) and a cooling outlet port  36  for circulating a desired cooling medium within the shell that contacts the core and the plurality of passages to reduce the temperature of the gas as it is passed therethrough. Depending on the particular application, the cooling inlet and outlet ports can be provided in the form of manifolds that are attached to the shell.  
      Referring to  FIG. 2 , the manifold  16  is attached to the shell  12  and includes inlet and outlet openings  20  and  22 . The inlet opening  20  is positioned and configured to receive gas or fluid and direct the gas or fluid into the heat exchanger and, more specifically, to the portion of the core passages in communication with the manifold inlet passage  32 . The outlet opening  22  is positioned and configured to receive gas or fluid exiting the portion of the core passages in communication with the manifold outlet passage  34 .  
      As illustrated, the manifold inlet opening  20  is disposed through a top surface  38  of the manifold and is positioned within a first portion of the manifold top surface. It is understood that the opening may be on the side or other location of surface  38 . In such preferred embodiment, the manifold outlet opening  22  is also disposed through the top surface  38  and is positioned along a second portion of the manifold top surface. Additionally, as shown in  FIG. 2 , diffuser vanes  40  can be positioned within the manifold downstream from the inlet opening  22  for the purpose providing a desired gas or fluid entry flow path within the heat exchanger.  
      FIGS.  3  to  5  each illustrate sectional views of the manifold as used with heat exchangers of this invention. The manifold  42  includes a divider wall  44  therein that projects outwardly away from an inside portion of the top surface  38 . The divider wall  44  operates to form a distinct and separate inlet passage  46  and outlet passage  48  within the manifold that each communicate with respective manifold inlet and outlet openings  50  and  52 . The divider wall extends lengthwise internally within the manifold separating the inlet and outlet ports, and forming a partition along the core passages that are in communication with the manifold inlet passage and outlet passage.  
      As illustrated in these figures, the manifold is configured internally to accommodate attachment with an end of the shell and adjacent a first end of the core. As shown each of FIGS.  3  to  5 , the end of the core is actually disposed a partial distance into the manifold when the manifold is connected to the shell, as illustrated in schematic by the line  54 . It may also be located on the end of the shell in the case of a flat plate configuration of the core endplate.  
      As discussed above, an issue that exists with respect to prior art heat exchangers is the unwanted bypassing of gas or fluid within the manifold. This is caused by a gap or space that may exist or develop between an end portion of the divider wall and an adjacent surface of the core. While attempts have been tried to address this issue through the use of an elastomeric seal, the use of such elastomeric seal has not prevented such leakage. This is due to the undesired distortion, softening, or disintegration of the seal at the heat exchanger operating metal temperatures of 315° C. or greater.  
       FIG. 3  illustrates a first embodiment of the invention as used with heat exchangers to remedy this problem. In this first embodiment, the manifold  42  includes a seal  56  that is interposed between the divider wall  44  and an adjacent core surface  58 , and that may be attached to at least one of the divider wall or core. In a preferred embodiment, the seal  56  is formed from a metallic material and is configured having a first segment  60  that is attached to an adjacent surface of the divider wall  62 , and having a second segment  64  that is integral with the first segment and that projects inwardly towards the outlet passage  48 .  
      The second segment  64  includes an end  66  that is configured to abut against the adjacent core surface  58  when the manifold and core are assembled together. The combined configuration of the first and second segments provide a seal profile resembling a “V” or having a “V-shaped” profile. The seal  56  is configured having a length that spans the distance between the divider wall and core within the manifold to provide a leak-tight seal against the core for the length of the core.  
      The seal can be formed from any type of metallic material that is capable of functioning to provide a desired seal when placed into contact with or pressed against the core, and that is capable of retaining a desired sealing engagement against the core when exposed to heat exchanger operating metal temperatures, which may exceed 315° C. Additionally, the seal can be formed by machining, stamping, rolling or other process, depending on the particular material selected, configuration, and available manufacturing equipment. In an example embodiment, the metallic seal is formed from stainless steel and is made by a stamping process.  
      In a preferred embodiment, the angle of projection as measured between the seal first and second segments is in the range of from about 110 to 170 degrees. Functionally, it is desired that the angle provide a sufficient bias and loading force onto the core when installed to provide a tight seal therebetween during the high-temperature operating conditions within the heat exchanger. Additionally, it is desired that first and second segments each be of sufficient dimension to help provide the above-noted desired loading force onto the core.  
      The seal can be attached to the divider wall by conventional methods, such as by welded, bolted, riveted attachment or the like. In an example embodiment, the seal  56  is attached by welding. Additionally, while the seal is shown in  FIG. 3  as being attached to the inlet passage side of the divider wall  44 , the seal can alternatively be attached to the outlet passage side of the divider wall if so desired.  
       FIG. 4  illustrates a second embodiment of the invention as used with heat exchangers. In this second embodiment, like the first embodiment, the manifold  42  includes a seal  68  that is interposed between the divider wall  44  and the core. In this particular embodiment, the seal  68  is formed from the same types of metallic materials disclosed above for the first embodiment, and is generally configured having an “M-shaped” profile.  
      Specifically, the seal  68  is configured having a central groove  70  that is sized and shaped to accept placement of the divider wall end  72  therein, and having a pair of raised ridges  74  surrounding the groove  70  that operate to help center placement of the divider wall end within the seal. Moving away from each raised ridge, the seal  68  includes a pair of base members or feet  76  that are configured for placement against the core. Configured in this manner, the seal groove  70  forms a seal with the divider wall and the seal feet  76  form a seal with the core.  
      Additionally, the seal  68  is provided in the form of a one-piece construction comprising the groove, raised ridges and feet that together operate to provide a self-loading mechanism between the divider wall and core, when the core and manifold are assembled together. This operates to provide and maintain a desired loading force for forming a seal between the divider wall and the core during heat exchanger operation. In a preferred embodiment, the seal  68  is formed from stainless steel and is made by a stamping process.  
      Although the seal  68  as illustrated in  FIG. 4  is shown without being attached to the divider wall other than by loading force, if desired, the seal  68  can be attached to the divider wall. For example, the seal can be attached by welded attachment or the like at the interface between the divider wall and the groove.  
       FIG. 5  illustrates a third embodiment of the invention as used with heat exchangers. In this third embodiment, like the first embodiment, the manifold  42  includes a seal  78  that is interposed between the divider wall  44  and the core  54 . In this particular embodiment, the seal  78  is formed from the same types of metallic materials disclosed above for the first embodiment, and is generally configured having a “C-shaped” profile.  
      Specifically, the seal  78  is configured having a central groove  80  that is sized and shaped to accommodate placement of the divider wall end  82  therein. The seal  78  includes a pair of legs or ends  84  that are integral with the groove and that each extend along respective opposed wall surfaces of the divider wall. The legs are attached to the divider wall by the same attachment methods noted above for the first invention embodiment. The seal  78  includes a base  86 , defining an outside surface of the groove from which the legs extend, and that is positioned against an adjacent core surface  88 . Configured in this manner, the seal legs  84  form a desired seal with the divider wall, and the seal base  80  forms a desired seal with the core.  
      Additionally, the seal  78  is provided in the form of a one-piece construction comprising the groove, legs, and base. The legs project outwardly from the base at less than a 90-degree angle, thereby providing a loading mechanism when the legs are each secured to the divider wall and the core and manifold are assembled together. This loading mechanism imposes a desired biasing force against the core surface to provide the desired seal between the core and seal during heat exchanger operation. In a preferred embodiment, the seal  78  is formed from stainless steel and is made by a stamping process.  
       FIG. 6  illustrates an alternative embodiment of the invention whereby the sealing mechanism between the divider wall  44  and the core  54  is provided without the use of an external element. Rather, in this specific embodiment, the sealing mechanism is provided by the manifold divider wall having an end  90  that is specially configured to complement and fit together with a complementary surface portion  92  of the core. In an example embedment, the manifold divider wall is configured with an end  90  that is sized and shaped to fit within a groove  92  disposed within the adjacent core surface to provide a tongue and groove attachment mechanism therebetween.  
      While specific invention embodiments useful with heat exchangers have been described and illustrated, it is to be understood that these embodiments are only exemplary of the many different types of inventive seals that can be installed and used with heat exchangers for the purpose of minimizing or eliminating bypass flow within the heat exchanger hot-side manifold within the scope of this invention.  
      Additionally, although the different embodiments of this invention have been described and illustrated as being positioned within a hot-side manifold having a particular inlet or outlet configuration, it is to be understood that heat exchanger seals of this invention can be used in other types of heat exchanger manifolds configured other than that specifically described and/or illustrated that generally use the interaction of a divider wall with the core to separate hot-side inlet and outlet gas or fluid flow therein.  
      Further, although the specific embodiments of this invention had been described in the context of a shell and tube-type heat exchanger, it is to be understood that the seal embodiments of this invention can be used with other types of heat exchangers, such as bar and plate heat exchangers, that use divider walls within a heat exchanger hot-side manifold to provide a seal between and separate inlet and outlet flow streams.  
      Heat exchangers comprising seals constructed in accordance with this invention operate to minimize or eliminate the unwanted bypass of gas or fluid within the heat exchanger manifold to enable the realization of improved heat exchanger operational efficiency.