Abstract:
A heat exchanger assembly designed for use as a fluid cooler formed of a first metal that includes a dissimilar metal connection allowing the exchanger to be utilized and reliably secured to another structure formed of a second metal. The assembly provides an easy way to cool engine exhausts, oil or another fluid flowing through the exchanger by transferring its heat to a cooling fluid flowing around the exchanger, or vice versa. The exchanger of the assembly is formed from a number of heat exchanger modules. In an embodiment intended particularly to cool diesel engine exhaust for a turbocharger, a steel or stainless steel exhaust inlet/outlet cap which is exposed to the high temperature exhaust is demountably attached to an all-aluminum heat exchange unit connected to the engine cooling system. The high temperature exhaust and the engine coolant follow generally parallel vertical paths through the heat exchanger in a generally U-shaped path that permits a short compact construction. A further embodiment utilizes a rubber-like sealant to seal the joints between an assembly of modules and header plates which hold the assembly together and provide a base to attachment of tanks.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is based on and claims priority from U.S. patent application Ser. No. 09/356,188 filed on Jul. 16, 1999. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to heat exchangers used to cool various flowing fluids. More particularly, the invention relates to a heat exchanger assembly for use in cooling engine oil, transmission fluid, or exhaust by passing a cooling fluid around or through the exchanger, particularly one utilizing two different metals in its construction.  
         BACKGROUND OF THE INVENTION  
         [0003]    Heat exchangers are used to transfer heat absorbed by a first fluid to a second cooling fluid. Either fluid may flow through passages located within the exchanger or around the passages, passing through openings extending through the exchanger that are spaced about the passages and are defined by a plurality of fins extending outwardly around the passages. Prior art heat exchangers have been constructed in a multitude of arrangements to expose the maximum surface area on the passages and the surrounding fins to allow the greatest heat transfer to occur between the first and second fluids.  
           [0004]    Older heat exchangers consist of arrangements of tubular passages having radially extending fins spaced from one another and attached to the passages in a permanent relationship. Heat exchangers of this type, while effective in cooling the heated first fluid flowing from the engine, are difficult to maintain and repair due to the unitary construction of the heat exchanger, as this construction necessitates the total disassembly of the exchanger to repair the exchanger. Disassembling these types of exchangers requires that the permanent connections between the components of the heat exchanger be undone, a process which is both time consuming and expensive.  
           [0005]    More recent developments with regard to fluid heat exchanger design have resulted in the creation of modular heat exchangers, such as that disclosed in Dierbeck U.S. Pat. No. 5,303,770. In this heat exchanger, the exchanger is comprised of a number of modules that are positioned against one another to form the modular heat exchanger. The individual modules can be releasably connected to one another to form the heat exchanger, removing the need for permanent welded, brazed, or soldered connections between the modules. In this arrangement, the modules are connected to one another by a set of tie rods extending through the ends of each of the modules to rigidly, but removably, secure the modules to one another to form the heat exchanger. Alternatively, similarly to prior art exchangers, the individual modules can also be welded to each other or otherwise joined to form permanent assemblies of specified numbers of modules used to form the heat exchanger.  
           [0006]    Each module disclosed in the above-identified patent consists of an elongate, rectangular extruded aluminum block including longitudinally extending oval-shaped passages and a series of outwardly extending fins spaced around the passages along the exterior of the block on the wide face thereof. The module also includes a flat face portion at either end in which no fins are disposed. A lateral opening is located in each face portion of the module that perpendicularly intersects opposite ends of the longitudinal passages. The openings cooperate with similar openings on adjacent modules to form a pair of fluid accumulation chambers. Each fluid accumulation chamber is closed at one end and open at the other end to provide an inlet or an outlet connection for fluid flow through the heat exchanger. In this arrangement, the heated first fluid enters the exchanger through an inlet end piece secured over the open end of one of the fluid accumulation chambers in the heat exchanger. Upon entering the chamber, the fluid is dispersed to flow in parallel through the longitudinal passages of each modular element in the exchanger. The second cooling fluid passes through transverse flow passages between the fins disposed about the longitudinal passages and cools the heated fluid flowing within the passages. Upon exiting the passages, the now cooled first fluid enters the fluid accumulation chamber on the opposite end and is recirculated back to the source of the first fluid through an outlet end piece secured over the open end of the other accumulation chamber.  
           [0007]    In the above-identified patent, the inlet and outlet end pieces are secured to the ends of the heat exchanger by the tie rods that also hold the modules together. Alternatively, the modules may be welded to each other. When welded together, the end pieces must be formed of the same metal as the modules to insure weld integrity and avoid potential problems of weld failure resulting from differential thermal expansion in dissimilar metals. Therefore, to avoid these problems, the inlet and outlet end pieces, as well as any other attachments connected to the modular elements, should be formed of aluminum to insure that the welded connections will not fail. This necessarily limits the application of the modular heat exchanger comprised of the extruded aluminum block modules to uses in which any necessary attachments welded to the heat exchanger, and any other elements welded to those attachments, can be formed of the same metal as the exchanger elements.  
           [0008]    In a situation where a modular heat exchanger of this type is placed within an enclosure to utilize a fluid flowing through the enclosure as the cooling fluid, the heat exchanger must be able to be fixed within the enclosure to openings in a wall or walls of the enclosure in a secure and leak-proof manner. This normally requires welded or brazed connections made between the wall and the exchanger. However, if the end pieces welded to the heat exchanger are aluminum and the enclosure is formed of a different metal, welding the two dissimilar metals may be impossible or may not provide a reliable leak-proof connection due to the thermal expansion differential between the dissimilar metals.  
           [0009]    To overcome this problem, certain prior art patents have disclosed methods for securing elements of a heat exchanger made from dissimilar metals to one another that form welded connections between the elements that greatly reduce weld failure.  
           [0010]    U.S. Pat. No. 2,368,391 discloses a method of fastening copper tubes within steel headers or tube plates. In this method, a copper tube is brazed to a steel sleeve that forms a protective layer around the copper tube. The steel sleeve is then welded to the steel header to connect the copper tube to the header. As the weld is formed between a sleeve and a header formed of the same metal, the weld made between the sleeve and the header does not have any thermal expansion problems that would cause premature failure of the weld. Also, when the steel sleeve is welded to the steel header, the steel sleeve around the copper tube prevents the tube from being damaged by the heat generated during the welding process.  
           [0011]    U.S. Pat. No. 4,034,802 also discloses a heat exchanger, namely, a radiator, that is formed of aluminum and to which are connected pipes formed of a dissimilar metal. The pipes are retained in connection with the aluminum radiator through the use of sleeves placed around the end of the pipes that contact and engage the interior of the conduit in the aluminum radiator to which the pipes are attached. The sleeves are attached to both the radiator and to the pipe by frictional forces generated by the insertion of the pipe into the sleeve within the radiator. The necessary frictional forces are generated by sets of threads disposed on the interior and exterior surfaces of the sleeve that contact the conduit and pipe. The insertion of the pipe flexes the sleeve outwardly, engaging the exterior threads with the conduit, and securing the sleeve within the conduit. The interior threads engage a complementary thread on the pipe exterior when the pipe is inserted into the sleeve to hold the pipe within the sleeve.  
           [0012]    While providing reliable dissimilar metal connections, in both of these prior art patents, the methods of attachment of the pieces of dissimilar metals include the attachment of a connecting element to each of the items to be attached. In the former, the steel sleeve must be brazed to the copper tube before welding to the header, and in the latter, the pipe must be threaded into the connector sleeve in order to engage the sleeve with the conduit. Thus, each prior art method requires that the connecting element be separately connected to each item. This places a large amount of stress on the connecting element and is also an unnecessary duplication of effort. Therefore, it is desirable to develop a heat exchanger assembly that includes a dissimilar metal connection that is formed on the exchanger in a single step to avoid any undesirable stress on the connection element.  
         SUMMARY OF THE INVENTION  
         [0013]    It is an object of the present invention to provide a novel heat exchanger assembly and method for attaching an end piece formed from one metal to a heat exchanger formed from a dissimilar metal.  
           [0014]    It is another object of the present invention to provide a heat exchanger assembly having this dissimilar metal connection that is formed of easily dissassembleable components.  
           [0015]    It is still another object of the present invention to provide a heat exchanger assembly with a dissimilar metal connection that can be quickly modified for use in a variety of different applications.  
           [0016]    The present invention is a heat exchanger designed for use as an fluid cooler that includes a dissimilar metal enclosure connection. The body of the heat exchanger can be of unitary construction, or may be comprised of individual modules similar to those disclosed in U.S. Pat. No. 5,303,770, which is herein incorporated by reference. The modules are generally rectangular extruded blocks that include a pair of longitudinal passages extending through the block and a number of V-shaped grooves extending along the wide faces of the block. A plurality of slots are cut transversely into the grooves to form fins disposed about the wide faces of the block along the entire length of the block.  
           [0017]    Each block also includes a pair of grooved face portions located at either end of the block in which no slots are cut. The face portions each have a lateral opening that extends through the face portion and intersects the longitudinal passages. The openings communicate with similar openings disposed within the face portions of adjacent blocks when a number of blocks are connected to form the heat exchanger. In such an arrangement, the lateral openings form a fluid accumulation chamber along each side of the exchanger. These fluid accumulation chambers make up flow inlet and outlet connections for the exchanger.  
           [0018]    To prevent the fluid flowing through the longitudinal passages from leaking around the edges of the lateral openings and between adjacent blocks, a counterbore is circumferentially disposed about each end of the lateral openings. In the counterbore is disposed a sealing arrangement which engages a complimentary structure about the lateral opening on an adjacent block to effectively seal the lateral openings.  
           [0019]    The grooves to either side of the counterbores extend through the face portions to the opposite ends of the blocks to form additional channels through which a fluid may flow. These channels may be closed off by welding when the block is utilized for certain specific purposes to control the flow of fluid through the exchanger.  
           [0020]    Each accumulation chamber is closed at one end and open at the opposite end to form the inlet and outlet connections. A cap plate, formed of the same metal as heat exchanger, is welded to the exchanger over one end of the accumulation chamber. The cap plate closes off that end of the accumulation chamber to retain one of the fluids within the heat exchanger, preventing any mixing of the fluid flowing through the exchanger and the fluid flowing around the exchanger.  
           [0021]    The exchanger formed of these modules can be positioned within an enclosure to allow a fluid flowing through the enclosure to pass through a number of flow slots defined by the fins on the exchanger in order to cool or be cooled by the fluid flowing through the passages in the heat exchanger. The fluid flowing through the heat exchanger passages may be oil, transmission fluid, coolant, or any other fluid to be cooled or used as a cooling fluid. The fluid is charged to and removed from the heat exchanger through a pair of hoses attached to the inlet and outlet connections of the exchanger. Each hose is sealingly engaged with a nipple joined to the exchanger over the inlet and outlet connections of the exchanger. Each nipple is usually formed of the same metal as the enclosure so that the nipples may be welded to the enclosure wall creating a reliable seal about the periphery of the nipple to prevent mixing or leakage of the respective fluids.  
           [0022]    However, as the nipples and the exchanger are formed from dissimilar metals, the nipples cannot be welded directly to the inlet and outlet connections due to the aforementioned problems associated with dissimilar metal welded connections. In order to overcome these problems, the nipple is retained in sealing engagement over the inlet and outlet connections of each fluid accumulation chamber by a peripheral retainer formed of the same metal as the exchanger. The retainer includes an opening in its center that is inserted around the nipple to hold the nipple in engagement with the heat exchanger over the connections. The retainer is then welded directly to the face portion of the heat exchanger to reliably secure the nipple in sealing engagement with the heat exchanger.  
           [0023]    In certain arrangements, the heat exchanger is positioned within an enclosure formed of a second metal in a sealed manner due to a the novel exchanger assembly and method of securing an end piece formed of a second metal to the heat exchanger. The assembly and method enables a reliable welded connection to be made between the end piece and the enclosure and between the exchanger and the end piece to prevent mixing of one fluid with the other.  
           [0024]    The construction of the novel exchanger assembly also allows the fluid to be cooled to flow through the passages in the exchanger or around the passages, depending upon the type of fluid that is to be cooled and the use to which the exchanger is put. Therefore, the exchanger can also be positioned in an exhaust system for use as an exhaust cooler, where the cooling fluid flows through the passages to cool hot exhaust gases flowing through the exchanger around the passages. In another embodiment of the invention where the heat exchanger is used as a transformer oil cooler, the grooves extending through the face portions on either side of the lateral openings are not welded shut when the longitudinal passages are closed. The open grooves allow a cooling fluid, such as air, to flow through the exchanger in the same manner as the previous embodiment, as well as along the grooves parallel to the longitudinal passages and perpendicular to the original cooling fluid flow, providing additional capacity for heat transfer in the exchanger.  
           [0025]    In accordance with a presently preferred embodiment of the invention for use as a diesel engine exhaust cooler, the heat exchanger includes a housing having an open end, a closed end and a pair of spaced first fluid openings that are disposed adjacent to the open end. A cap is secured to the housing over the open end and includes a central dividing wall that separates the cap into a pair of chambers, each chamber being in fluid communication with one of a pair of second fluid openings in the cap. A plurality of unitary heat exchange modules, of a block-like construction described above, are disposed within the housing in fluid communication with the first fluid openings and the second fluid openings. The modules are grouped to define a pair of separate cells each of which is aligned with one of the chambers in the cap. The through bores in each group of heat exchange modules are in fluid communication with one of the second fluid openings, and the slots defined by the toothed fins in the modules are in fluid communication with the first fluid openings permitting fluid flow along and transverse to the slots.  
           [0026]    The housing and the heat exchange modules are preferably made of aluminum and the cap is made of steel, preferably stainless steel. The housing and heat exchange modules are easily removed from the stainless steel cap with bolted connections of which two embodiments are disclosed.  
           [0027]    The construction of the preferred embodiments also utilize a unique construction and arrangement of header plates to separate the two fluids and to position the unitary modules that form the heat exchanger assembly. The modules are formed with narrowed necks at each end defining the end of the pattern of toothed fins, the necks also surrounding and defining the end openings to the through bore. A header plate for each end of the plurality of modules forming an assembly is sized to receive the necks of the modules and to interconnect and hold the modules in the assembly. Each header plate is supported at the end of the assembly on the end-most fins and closes the space defined by the fins between the necks of adjacent modules. The peripheral edge of each header plate generally coincides with the outer periphery of the assembly of modules. Sealing material is used to provide fluid tight seams between each header plate opening and the respective module neck that extends therethrough. Each header plate is connected to the assembly with welds. Finally, a tank having a continuous outer edge is connected to the peripheral edge of each header plate along a fluid tight joint. In one embodiment, a first fluid inlet connection is made to one of the tanks to direct a first fluid through the longitudinal bores in the modules and into the other tank. A housing is provided that extends between the header plates and at least partially encloses the assembly and an inlet is provided in the housing for directing a second fluid into and through the slots between the modules of the assembly. An outlet is also provided for directing the second fluid from the housing and is positioned with respect to the inlet to cause the second fluid to flow through the assembly in a direction along the slots and transverse thereto through the spaces defined by the tooth-shaped fins. Preferably, the housing comprises a walled enclosure that includes a pair of side walls and a pair of end walls, and the heat exchanger further comprises a pair of module assemblies within the housing, a partition wall separating the assemblies which partition wall extends between opposite side walls and is connected along an edge between the side walls to one of the header plates. An open passage is provided between an opposite partition wall and the other header plate to provide a connection for the second fluid between the two assemblies. The inlet and the outlet for the second fluid are positioned in the housing walls on opposite sides of the partition wall and adjacent to the header plate to which the partition wall is connected.  
           [0028]    In a further variation, a separator plate divides the one tank into an inlet chamber for the first fluid and an outlet chamber for the first fluid. The first fluid inlet connection opens into the inlet chamber, and a first fluid outlet connection is provided in the outlet chamber for directing the first fluid from the heat exchanger.  
           [0029]    In a further embodiment, which is particularly adaptable for use in more conventional automotive radiator applications, the slots that are cut in the faces of the modules do not extend the full length of the module, but rather terminate on both ends to form unslotted module ends. Each of the ends, in turn, terminates in a shoulder that leads to a neck surrounding and defining an end opening to the module throughbore. The header plate is supported on the shoulders of adjacent modules forming the assembly and closes the space between the necks of adjacent modules. In this embodiment, the header plate comprises a generally flat mean body portion in which are formed the openings for the necks of the modules. The main body portion is surrounded by a peripheral outer rim that encloses the plate body portion and forms a sealant contaminant chamber. The chamber is adapted to receive a pourable sealant to a depth sufficient to fill the chamber and cover the body portion of the header plate. The header plate is permanently secured to the module assembly with spaced welds between the unslotted ends of the modules and the undersurface of the plate body opposite the containment chamber. The outer edge of the tank is dimensioned to extend into the containment chamber and the sealant therein to form the fluid tight joint. Spaced tack welds are them provided along an interface between the rim of the containment chamber and the edge of the tank. In a typical automotive application, the slots define air flow passages through the assembly and each of the tanks includes a fluid transfer connection. 
       
    
    
     BRIEF DESCRIPTION OF THE OF THE DRAWINGS  
       [0030]    [0030]FIG. 1 is a front elevation view of a heat exchanger assembly constructed according to the present invention placed in a bottom collection tank of a conventional radiator;  
         [0031]    [0031]FIG. 2 is a cross-sectional view along line  2 - 2  of FIG. 1;  
         [0032]    [0032]FIG. 3 is a cross-sectional view along line  3 - 3  of FIG. 2;  
         [0033]    [0033]FIG. 4 is a cross-sectional view along line  4 - 4  of FIG. 2;  
         [0034]    [0034]FIG. 5 is a partially broken away isometric view of a second embodiment of the present invention used as a transformer oil cooler;  
         [0035]    [0035]FIG. 6 is a cross-sectional view along line  6 - 6  of FIG. 5;  
         [0036]    [0036]FIG. 7 is a side elevation view of the transformer oil cooler of FIG. 5 attached to a transformer;  
         [0037]    [0037]FIG. 8 is a partially broken away cross-sectional view of the heat exchanger of FIG. 5 showing a turbulator plate disposed within a passage of the exchanger;  
         [0038]    [0038]FIG. 9 is a cross-sectional view along line  9 - 9  of FIG. 8;  
         [0039]    [0039]FIG. 10 is a partially broken away side elevation view of a third embodiment of the heat exchanger assembly of the present invention utilized as an exhaust cooler;  
         [0040]    [0040]FIG. 11 is a cross-sectional view along line  11 - 11  of FIG. 10;  
         [0041]    [0041]FIG. 12 is an isometric view of a fourth embodiment of the heat exchanger assembly of the present invention utilized as an exhaust cooler;  
         [0042]    [0042]FIG. 13 is a cross-sectional view along line  13 - 13  of FIG. 12;  
         [0043]    [0043]FIG. 14 is a cross-sectional view along line  14 - 14  of FIG. 13;  
         [0044]    [0044]FIG. 15 is a cross-sectional view along line  15 - 15  of FIG. 13;  
         [0045]    [0045]FIG. 16 is a partial sectional view of a heat exchanger module utilized in the embodiment of FIG. 12;  
         [0046]    [0046]FIG. 17 is a schematic view of the system in which the exhaust cooler of FIG. 12 is utilized;  
         [0047]    FIGS.  18 A- 18 C are additional embodiments of the heat exchanger modules of the present invention;  
         [0048]    [0048]FIG. 19 is a top plan view of the alternative module construction of FIG. 18 a  secured to a header plate;  
         [0049]    [0049]FIG. 20 is a top plan view of the heat exchanger module of FIG. 18C secured to a header plate;  
         [0050]    [0050]FIG. 21 is a cross-sectional along line  21 - 21  of FIG. 19;  
         [0051]    [0051]FIG. 22 is a cross-sectional view along line  22 - 22  of FIG. 21;  
         [0052]    [0052]FIG. 23 is a partial sectional view similar to FIG. 21 illustrating an alternate configuration of the heat exchanger modules of FIG. 19; and  
         [0053]    [0053]FIG. 24 is a cross-sectional view along line  24 - 24  of FIG. 23.  
         [0054]    [0054]FIG. 25 is a horizontal sectional view of another embodiment of the FIG. 12 exhaust cooler take on line  25 - 25  of FIG. 26.  
         [0055]    [0055]FIG. 26 is a vertical sectional view take on line  26 - 26  of FIG. 25.  
         [0056]    [0056]FIG. 27 is a front elevation view of a further embodiment of the invention with a portion shown in section.  
         [0057]    [0057]FIG. 28 is a horizontal section through the heat exchanger taken on line  28 - 28  of FIG. 27. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0058]    With reference now to the drawing figures wherein like reference numerals designate like parts throughout the disclosure, the present invention is a heat exchanger indicated generally at  20  and illustrated in FIG. 1. The exchanger  20  is positioned in a bottom collection tank  22  of a conventional radiator  24  for use as an oil cooler. In this arrangement, the oil flows through the exchanger  20  via a pair of openings  21  in a side wall  23  of the tank  22 . The exchanger  20  transfers heat from the oil flowing through the exchanger  20  in a direction shown by arrows A to a coolant fluid passing through the collection tank  22  and around the cooler  20  in a direction shown by arrows B before recirculating the oil back to the automobile engine.  
         [0059]    Referring now to FIGS.  2 - 5 , the exchanger  20  is made up of a plurality of modular elements  26  that are assembled to form a body  25  of the exchanger  20 . An exchanger  20  having this general construction is disclosed in Dierbeck U.S. Pat. No. 5,303,770, which is herein incorporated by reference. Each element  26  is preferably made from an elongate extruded aluminum block  28 . The block  28  is generally rectangular in cross-section, having a pair of wide faces  30  joined by a pair of narrow faces  31 . Two parallel, longitudinal passages  32  having flattened or oval cross-sections extend completely through the block  28  along the wide faces  30 . Each block  28  also includes a number of V-shaped grooves  33  extending along the wide faces  30  of the block. The grooves  33  increase the available surface area over which heat transfer can occur and reduce the amount of aluminum used to form the block  28 .  
         [0060]    A series of parallel fins  34  are formed on both wide faces  30  of the block  28  to overlay the passages  32 , with adjacent pairs of fins  34  defining slots  36  between the fins  34 . The fins  34  are formed by cutting the slots  36  across the grooves  33  at predetermined intervals so that the fins  34  extend generally perpendicular to the axes of the passages  32  have a sawtooth profile. The outer edges  38  of the fins  34  lay coplanar with the wide face  30  in which they are formed.  
         [0061]    The body  25  of the exchanger  20  is formed by stacking the blocks  28  together in face-to-face contact with the outer edges  38  of the fins  34  on adjacent blocks  28  directly abutting one another. The fins  34  and slots  36  on the blocks  28  in the assembled body  25  define inner fluid flow passages  40  between adjacent blocks  28  which are twice the height of the fins  34  in length, and as wide as the slot  36  between adjacent fins  34 . The fins  34  and slots  36  located on the blocks  28  at each end of the exchanger  20  define a series of outer air flow passages  42  which are half the length of inner air passages  40 .  
         [0062]    The opposite ends of each block  28  include grooved, unslotted face portions  44  on both wide faces  30 . A lateral opening  46  is centered in and extends through each of the face portions  44 . The opening  46  intersects both of the passages  32  extending through the block  28 . When the blocks  28  are assembled to form the body  25  of exchanger  20 , the openings  46  in the blocks  28  define a pair of accumulation chambers  47  for collection of the fluid flow at an inlet end  48  and an outlet end  50  of the exchanger  20 .  
         [0063]    In order to prevent fluid flowing through the passages  32  from leaking around the lateral openings  46 , a counterbore  52  is disposed about each lateral opening  46 . The counterbore  52  is located in each face portion  44  on either side of the lateral opening  46 , and extends into the base portion  44  for a depth greater than the grooves  33 . In one counterbore  52  is disposed a rectangular section annular insert  54 . The rectangular insert  54  is preferably made of aluminum and is press fit into the counterbore  52  to effectively prevent any fluid communication between the grooves  33  intersecting the counterbore  52  and the lateral opening  46 .  
         [0064]    Opposite the rectangular insert  54 , a second aluminum insert having a L-shaped cross-section  56  is placed within the opposite counterbore  52 . An O-ring  58  is positioned within the L-shaped insert  56 . When adjacent blocks  28  are positioned in a face-to-face arrangement, the O-ring  58  extending around the lateral opening  46 , one block  28  sealingly engages the rectangular insert  54  of the adjacent block  28 . In this manner, the O-ring  58  and rectangular insert  54  provide a liquid seal about the lateral openings  46 . To secure each insert  54  and  56  in position, an adhesive may be placed between the inserts  54  and  56  in the counterbore  52 , or, should the inserts  54  and  56  be formed of aluminum, small seam welds may be positioned about the circumference of each insert  54  and  56 . In an alternative embodiment, the L-shaped insert  56  and O-ring  58  may be replaced by a single resilient grommet (not shown) that sealingly engages the rectangular insert  54  positioned on an adjacent block  28 .  
         [0065]    When positioned in this face-to-face arrangement, the grooves  33  on adjacent blocks  28  which extend through the face portions  44  on either side of the counterbores  52  form a number of diamond-shaped channels  60 . The channels  60  allow the fluid flowing around the passages  32  to flow longitudinally through the exchanger  20  in a direction parallel to the passages  32 , increasing the heat transfer capacity of the exchanger  20 .  
         [0066]    As shown in FIG. 4, to close off the passages  32  in outer edges  62  of face portions  44 , a number of plugs  64  are positioned within each end of passages  32 , completely obstructing the ends of each passage  32 . The plugs  64  may comprise permanent welds, elastomer plugs, or aluminum plugs secured in place with an adhesive. These plugs may also cover the channels  60  to restrict fluid flow around the passages  32  in a single direction or the channels may be covered by a second set of plugs  66 .  
         [0067]    To form the body  25  of the exchanger  20  from blocks  26 , the preferred means for securing adjacent blocks  28  together is to weld the outer edges  62  of face portions  44  of adjacent blocks  28  to one another. However, the blocks  28  may also be connected by placing an adhesive (not shown) on adjacent face portions  44 , either alone, or in connection with some type of positioning arrangement. In either arrangement, the welds or adhesive used also form the plugs  66  used to close the channels  60  extending through the face portions.  
         [0068]    Another arrangement that can be utilized to form the exchanger  20  is that disclosed in the Dierbeck patent, i.e., using tie rods (not shown) that are insertable through openings (not shown) in the face portions  44  of each block  28  and secured to the exchanger  20  by nuts (not shown) threadedly mounted at both ends of the rods.  
         [0069]    To completely enclose the interior of the exchanger  20 , the face portion  44  at each the end of accumulation chamber  47  opposite the outermost O-ring  58  is closed off by attaching a rectangular cap plate  68  over the opening  46 , as shown in FIGS. 2, 3 and  4 . The cap plate  68  is formed of aluminum and includes a circular depression  70  in its center. The depression  70  receives an O-ring  72  similar to O-rings  58  located in the U-shaped inserts  56  of each face portion. The cap plate  68  is attached to the face portion  44  by a weld  74  between the cap plate  66  and the face portion  44  to sealingly engage the O-ring  72  in depression  70  with the rectangular insert  54  about the counterbore  52  in the face portion  44 .  
         [0070]    Looking now at FIGS. 2 and 3, attached over the inlet end  48  and outlet end  50  opposite the cap plates  68  are tank connections  76  used to attach the exchanger  20  to the tank  22 . Each connection  76  includes a steel nipple  78  that is generally cylindrical in shape, including a channel  80  extending through the nipple  78 . The nipple  78  also includes a flange  82  extending radially outward from one end of the nipple  78 . The diameter of the channel  80  in nipple  78  is approximately equal to the diameter of the opening  46  in face portions  44 . The flange  82  has a diameter greater than that of the L-shaped insert  56  in the face portion  44 . Therefore, when the nipple  78  is attached to the d exchanger  20  over the inlet end  48  or the outlet end  50  to form the connection  76 , the flange  82  rests on the face portion  44  and sealingly engages the O-ring  58  positioned in the insert  56  in the face portions  44  of the inlet end  48  or outlet end  50  of exchanger  20 .  
         [0071]    The nipple  78  is secured to the exchanger  20  to form the connection  76  by a retainer  84 . Retainer  84  is formed of aluminum, is generally rectangular in shape, and includes a nipple opening  86  in its center. The diameter of the opening  86  is slightly greater than the exterior diameter of the nipple  78  to allow the nipple  78  to be inserted through opening  86  in retainer  84 . Also, on one side of the retainer  84 , the opening  86  includes a circular recess  88 . When the retainer  84  is positioned over nipple  78  on the face portion  44 , the recess  88  receives and engages the flange  82  on nipple  78 , pressing the flange  82  into engagement with the O-ring  58 . Furthermore, as the retainer  84  is formed of the same metal as the exchanger  20 , the retainer  84  can be secured directly to the exchanger  20  by a weld  90  between the retainer  84  and the face portion  44 .  
         [0072]    In each connection  76 , the nipple  78  is sealingly secured over the inlet  48  or outlet  50  of the exchanger  20  without the need for welding the nipple  78  directly to the exchanger  20 , avoiding the problems typically found when welding dissimilar metals together. Also, when the exchanger  20  is placed within the collection tank  22  of the radiator  24 , the nipples  78  extend through the openings  21  in side wall  23  of the tank  22  for connection to a pair of hoses (not shown) that carry the heated oil from the engine to the cooler  20 , and from the exchanger  20  back to the engine. To secure the exchanger  20  and within the tank  22  so that the hoses can be connected to the nipples  78 , a weld  92  is formed between the nipple  78  and the tank  22 . Because the nipples  78  and tank  22  are formed of the same metal, similarly to the retainers  84  and the exchanger  20 , the weld  92  between each nipple  78  and the tank  22  is not subject to differential thermal expansion. Therefore, the tank connections  76  allow the aluminum exchanger  20  to be positively joined with the steel tank  22  to cool oil flowing from the engine and avoid the problems normally associated with attaching dissimilar metals without having to provide and connect multiple intermediate pieces in order to form a proper seal between the exchanger  20  and tank  22 .  
         [0073]    A second embodiment of the present invention is illustrated in FIGS.  5 - 9 . In this embodiment, the exchanger  20  is secured to a transformer  94  and utilized as a transformer oil cooler. In this embodiment, the exchanger  20  is substantially identical to the first embodiment to allow air to circulate through the exchanger  20  in a direction perpendicular to the fluid flow through the passages  32  along the channels  60  and also in a direction parallel to the direction of fluid flow through the passages  32  between the fins  34 . Thus, an increased amount of air is able to flow through the exchanger  20  around the passages  32  to cool the oil flowing through the passages from the transformer  94 .  
         [0074]    As shown in FIG. 7, the exchanger  20  is attached to one side of the transformer  94  such that the inlet end  48  is disposed directly beneath the outlet end  50 . This orientation is required as the oil flows between the transformer  94  and exchanger  20  by a convection current indicated at C generated by the heating of the oil within the transformer  94  and the cooling of the oil as it flows upwardly along the exchanger  20 . To secure the exchanger  20  in this arrangement with the transformer  94 , the nipples  78  in each connection  76  are attached to the transformer  94  by welds  96  between the nipple  78  and the transformer  94 .  
         [0075]    Referring now to FIGS. 8 and 9, the passages  32  within the exchanger  20  may include additional elements to enhance the heat transfer capability of the exchanger. The first structure is a turbulator plate  98  that is insertable into the passage  32  prior to the closure of the passage  32  by the end plug  54 . The turbulator plate  96  is formed of a thin piece of metal or other rigid material that has a length and width slightly shorter than the corresponding dimensions of the passage  32 . The plate  98  includes a number of raised portions  100  disposed over the surface of the plate. The raised portions  100  extend from both sides of the turbulator plate  98  and serve to agitate the flow through the passage  32 , allowing the fluid to more uniformly contact the exterior of the passage  32  in order to more effectively transfer heat from the fluid flowing within the passages  32 . The raised portions  100  give the turbulator plate  98  a height slightly greater than the height of the passage  32  such that the inner edges of passages  32  engage the tips of the raised portions  100  when the turbulator plate  98  is inserted into the passage  32 . The turbulator plate  98  is thus rigidly retained within the passage  32  while in operation.  
         [0076]    Alternatively, in an embodiment not shown in the figures, the turbulator plate  98  may be formed of a plurality of thin individual strips of a rigid material that are interwoven to form a generally flat plate having a number of raised portions distributed about both the surfaces of the plate.  
         [0077]    The second structure of the exchanger  20  that increases the capacity for heat transfer of the passages  32  is a plurality of generally U-shaped grooves  102  disposed along the passage  32  and extending in the direction of the fluid flow through the passage  32  as shown in FIG. 9. The grooves  102  are located about the entire surface of the passage  32  and greatly increase the surface area of the passage  32  over which heat transfer from the fluid may occur. Furthermore, though the turbulator plate  98  and U-shaped grooves  102  are discussed with respect to the use of exchanger  20  as a transformer oil cooler, the two structures may also be utilized in other embodiments to increase the heat transfer capacity of an exchanger  20  used for a purpose other than as a transformer oil cooler.  
         [0078]    A third embodiment of the present invention is shown in FIGS. 10 and 11 where the exchanger  20  is utilized as an exhaust cooler. In this embodiment, engine coolant flows through the passages  32  of the exchanger  20  to cool hot exhaust gases flowing from the engine through the passages  40  defined by the slots  36 . The construction of the exchanger  20  in this embodiment is similar to that disclosed in the first embodiment in that the exchanger  20  is formed of a number of blocks  28  secured to each other in a vertically stacked arrangement. The exchanger  20  also includes a pair of end plates  104  welded over the wide faces  30  of the uppermost and lowermost blocks  28  forming the exchanger  20 . The plates  104  serve to enclose the fins  34  located on the uppermost and lowermost blocks  28  to enable the exchanger  20  to direct heated exhaust gases flowing from the engine through the slots  36  formed by the fins  34  on each block  28 .  
         [0079]    The end plates  104  and face portions  44  provide attachment points for the attachment of a pair of exhaust pipe connectors  106  to the exchanger  20 . The connectors  106  serve to position the exchanger  20  within an exhaust system for a vehicle. The connectors  106  include a circular end portion  108 , an outwardly extending angled portion  110 , and a generally rectangular end portion  112 . Opposite the angled portion  104 , the rectangular end portion  112  includes a number of flanges  114  extending outwardly from each side of the rectangular end portion  112 . The flanges each include a pair of mounting openings (not shown) that receive fasteners  118  to secure the exhaust pipe connectors  106  to the exchanger  20 . Each of the flanges  114  extends along an entire side of the rectangular end portion  112 , with the flanges  114  at the top and bottom of the exchanger  20  extending parallel to the direction of exhaust gas flow through the exchanger, and flanges  114  on either side of the exchanger  20  extending perpendicularly to the direction of air flow. Thus, the fasteners  118  inserted through the mounting openings in the flanges contact the end plates  104  at the top and bottom of the exchanger, and the face portions  44  on either side of the exchanger  20  without intersecting the lateral openings  46  within the face portions  44 . Opposite the rectangular end portion  112 , the circular end portion  108  is dimensioned to be slightly larger than an exhaust pipe  120  connected to an automobile engine. The circular end portion  108  is connected to the exhaust pipe  100  in a conventional sealed manner to prevent heated exhaust from flowing between the pipe  120  and connector  106  without flowing through the exchanger  20 . Also, the grooves  33  passing through the face portions  44  are completely sealed by a number of plugs or welds (not shown) extending across the grooves to prevent exhaust from flowing outwardly through the grooves without passing entirely through the exchanger  20 .  
         [0080]    Each connector  106  also includes a number of baffles  122  disposed within the angled portion  110  and rectangular end portion  112 . The baffles  122  extend into the connector  106  perpendicularly to the direction of air flow through the connector and serve to act as a muffler by dampening the noise generated by the air flow through the exhaust system.  
         [0081]    Referring now to FIGS.  12 - 17 , a fourth embodiment of the invention is illustrated. In this embodiment, the diesel exhaust cooler  124  includes a cap  126  secured to a housing  128 . The cap  126  is generally rectangular in shape and includes a flat top end  130  from which extend opposed pairs of side walls  132  and end walls  134 . The side walls  132  and end walls  134  define an open end  136  opposite the top end  130  which is encircled by a peripheral flange  138 . The flange  138  includes a number of bolt holes  140  extending around the flange  138  through which are inserted bolts  142  for connections to be described below.  
         [0082]    The cap  126  also includes an interior baffle  144  extending downwardly parallel to end walls  134  between the midpoints of the side walls  132 . The baffle  144  separates the cap  126  into a pair of chambers  146 , each of which is in fluid communication with one of a fluid inlet  148  or a fluid outlet  150  disposed diagonally opposite from one another on opposed sides of the cap  126 .  
         [0083]    Looking specifically now at FIG. 13, the housing  128  includes a top portion  152  secured to a bottom portion  154 . The top portion  152  includes a pair of side walls  156  joined at opposed ends by a pair of shorter end walls  158 . The side walls  156  and end walls  158  define an enclosure  160  in which is disposed a partition wall  162 . The partition wall  162  is in alignment with the baffle  144  on the cap  126  and is positioned within the enclosure  160  between the midpoints of the side walls  156 . The partition wall  162  divides the enclosure  160  within top portion  152  into a pair of cells  164 . The partition wall  162  also permits fluid communication between the respective cells  164  because the wall  162  has a length shorter than that of walls  156  and  158 , defining a passage  165  at the lower end of the top portion  152  between the cells  164 . The passage  165  enables a coolant fluid which enters the top portion  152  through a fluid inlet  166  disposed in the end wall  158  of the top portion  152  in fluid communication with the adjacent cell  164 , to flow between the cells  164 . This allows the coolant fluid to contact each of the heat exchanger modules  170  within the top portion  152  before flowing out of the cooler  124  through a fluid outlet  167  disposed in the end wall  158  opposite the fluid inlet.  
         [0084]    Referring now to FIGS.  13 - 16 , each cell  164  encloses an assembly  168  of heat exchanger modules  170 . Each module  170  is similar to the modules or blocks  28  described with respect to previous embodiments. Each module  170  includes a body  172  having toothed fins  184  formed in opposite faces and a pair of longitudinal throughbores  176  extending the length of each module  170  between the faces  174  and in a direction transverse to the fins  184 . The modules  170  are preferably formed from aluminum extrusions that include the throughbores  176  and V-shaped grooves  178  extending parallel to the bores along the exterior of each of the faces  174 . The grooves  178  are subsequently cut laterally to form slots  182  which extend across the faces  174  perpendicular to the grooves  178  to define the saw-toothed fins  184 . The modules are slotted along their full lengths and, at opposite ends, the endmost fin  185  end at necks  180  which define the bores  176 .  
         [0085]    The modules  170  can be secured to one another and to the top portion  152  to form the assembly  168  in a conventional manner such as by using bolts, a high temperature adhesive, or welds. However, most preferably, the modules  170  are held in position within the respective cells  164  of top portion  152  of the housing by a top header plate  186  and a bottom header plate  188  disposed at opposite ends of the top portion  152 . Each header plate  186  and  188  is secured to the top portion  152  by welds  189  and includes a plurality of openings  190  dimensioned to receive the necks  180  at the ends of each module  170  in order to position and securely retain each module  170  within the housing  128 . The necks  180  can be then secured within the openings  190  of the header plates by any conventional means, such as an adhesive, but are preferably secured by welds  192 . Between adjacent modules  170 , the header plates cover the endmost fins  185  (see FIG. 16) and also cover and close the diamond-shaped passages  187  defined by adjacent saw toothed fins  184 . Thus, the header plates also serve to assure leak proof separation of the two fluids (exhaust and coolant, for example) flowing through the head exchanger  124 . The header plates may further be used to adjust the module-to-module spacing within an assembly comprising a cell  164 .  
         [0086]    Top header plate  186  has a peripheral dimension approximately equal to the peripheral dimension of the flange  136  on cap  126 . Furthermore, the top header plate  186  includes a number of bolt holes  194  spaced about the periphery of the top header plate  186  that are alignable with the bolt holes  140  in the peripheral flange  136  on cap  126 . As a result, when the top header plate  186  is secured to the housing  128  by welds  189 , and the cap  126  is positioned on the top header plate  166  over the housing  128 , the holes  140  in peripheral flange  136  of cap  126  align with the holes  194  in the top header plate  186  such that the bolts  142  can be inserted through the respective holes  140  and  194  and secured therein with nuts  198 . Furthermore, in order to prevent fluid from leaking out of the cooler  124  between the cap  126  and top header plate  186 , a gasket  200  is disposed between the top header plate  186  and peripheral flange  136 . The gasket  200  is formed of a resilient material but is preferably an exhaust gasket with a boiler sealant applied to the exterior of the gasket  200 .  
         [0087]    Opposite the cap  126 , the bottom portion  154  of housing  128  is secured to the bottom header plate  188 . In one embodiment, as best shown in FIG. 15, the bottom portion  154  includes a bottom wall  202  from which extend upwardly opposed pairs of side walls  204  and end walls  206 . The side walls  204  and end walls  206  define an open upper end  208  which is positioned in fluid communication with the modules  170  extending through the openings  190  in the bottom header plate  188 . To retain the bottom portion  154  on the bottom header plate  188 , continuous weld  210  is formed between the open upper end  208  of the bottom portion  154  and the bottom header plate  188 .  
         [0088]    Referring also to FIGS. 25 and 26, there is shown another embodiment of an exhaust cooler  211  of the present invention. In this embodiment, the exhaust cooler includes an upper cap  212  and a unitary lower housing  213 . Rather than utilizing a separate bottom portion as in the previously described embodiment, the housing  213  includes extended length side walls  214  and end walls  215 . The walls  214  and  215  define a lower end opening  216  that is closed by an end plate  217  welded to the opening  216 . The interior space above the end plate  217  and the bottom header plate  188  defines the volume provided by the bottom portion  154  of the FIG. 13 embodiment.  
         [0089]    The interior of the housing  213  is provided with a modified partition wall  218  that separates the upper portions of the cells  164  as previously described. The central portion of the partition wall  218  includes a vertically extending bolt tube  220  extending the full vertical length of the wall. The upper cap  212  also includes a modified baffle plate  221  that is provided with an integral cylindrical stud  222 . When the cap  212  is installed atop the housing  213 , the cylindrical stud  222  is aligned with the bolt tube  220  in the lower partition wall  218 . The lower end plate  217  is centrally bored to receive a long connecting bolt  223  which extends upwardly through the bolt tube  220  in the partition wall  218  with the upper end of the bolt threaded into a tapped bore in the lower end of the stud  222 . The inner surface of the end plate  217  is provided with a pair of stiffening ribs  224  to maintain the rigidity of the end plate  217  when the connecting bolt  223  is threaded tightly to secure the cap  212  on the housing  213 . The lower edge of the cap  212  is provided with a widened end flange  226  which receives the upper edge of the housing  213  with a suitable sealing gasket  225  interposed therebetween. The cap  212  and housing  213  are readily detachable from one another simply by removing the connecting bolt  223 .  
         [0090]    Referring now to FIGS.  18 - 24 , three alternative embodiments for the heat exchange modules  170  used in the present invention are illustrated. In FIG. 18A, a module  170  includes U-shaped grooves on opposed faces  174  of the module that extend parallel to a single throughbore  176  disposed within the module  170 . The U-shaped grooves, in conjunction with the slots that extend perpendicularly across the grooves  244 , define fins  248  which can be positioned within the U-shaped grooves  244  on adjacent modules  170  to form the overlapping heat exchanger module configuration shown in FIG. 19. This configuration enables an exhaust cooler  124  constructed in this manner to be smaller in size than the cooler  20  shown in FIGS.  12 - 17  due to the nesting of the modules  170  within one another. Further, the effectiveness of the cooler  124  is not reduced because a higher amount of turbulence is generated in the flow of the cooling fluid past the fins  248 . This increase is graphically illustrated in FIGS.  21 - 24  where the overlap of the fins  248  on adjacent modules  170  and the flow path of the cooling fluid between the fins is shown for both aligned and staggered arrangements of the fins  248 . The increased turbulence increases the thermal contact of the cooling fluid with the module  170  insures heat transfer between the heated fluid flowing within the throughbores  176  and the cooling fluid comparable to that achieved with the previous embodiment for the cooler  124 .  
         [0091]    A similar configuration for the modules  170  is shown in FIG. 18 in which the U-shaped grooves  244  are cut deeper into the body of the module  170  in order to increase the surface area available for heat transfer and to reduce the amount of material the heat must be transferred through on each module  170 . This further increases through the amount of heat that can be transferred from the heated fluid in the throughbore  176  to the coolant fluid flowing past the fins  249 .  
         [0092]    A fourth embodiment of the module  170  is shown in FIG. 18C. In this embodiment, the module  170  includes a number of U-shaped grooves  244  formed on the opposite faces  174  of the module  170 . The grooves  244  on opposite faces  174  of the module  170  are offset from one another such that the fins  250  on one face  174  are in alignment with the grooves  244  on the opposite face  170 . This configuration enables the modules  170  to be positioned with the modules  170  in either a staggered arrangement similar to FIG. 19, or in an aligned arrangement as shown in FIG. 20. The arrangement of the modules  170  shown in either FIG. 19 or  20  positions the fins  250  of adjacent modules  170  is such that laminar flow of the cooling fluid past the fins  249  or  250  is disrupted and made highly turbulent to increase the thermal contact of the cooling fluid with the fins.  
         [0093]    In operation and referring also to FIG. 17, the cooler  124  is connected to the exhaust system  230  of an automobile. Exhaust from an engine  232  passes along an exhaust pipe  234  to a Y-junction  236  where a portion of the exhaust is directed at the junction  236  to a muffler  238 . The remaining portion of the exhaust flows along the other leg of the junction  236  to the exhaust cooler  124  (or  211 ). The exhaust enters the cooler  124  through fluid inlet  148  and into the cap  126 . The baffle  144  directs the incoming exhaust downwardly into the throughbores  176  in each module  170  disposed in the cell  164  beneath the chamber  146  that is in communication with the fluid inlet  148  as indicated by arrows A in FIGS. 13, 15 and  16 . Simultaneously, a coolant fluid flowing from a coolant source  240  (such as the engine cooling system) enters the housing  128  through the fluid inlet nozzle  166 . The coolant flows into the cell  164  disposed directly beneath the chamber  146  into which the exhaust is flowing and flows along the slots  182  in each module  170  between the fins  184  and through the V-shaped grooves  178  in a direction transverse to the fins as shown by arrows B in FIGS. 15 and 16. As the exhaust flows through the throughbores  176 , the modules  170  are heated by the exhaust, and the coolant flowing past the fins  184  removes this heat to, in turn, cool the exhaust.  
         [0094]    The exhaust and coolant each flow downwardly through the respective flow paths in the cell  164  until each respective fluid is directed at or near the bottom of the cell into the adjacent cell  164 . For the exhaust, the bottom portion  154  of the housing receives the incoming exhaust from the first cell  164  and directs it in a direction shown by arrow C in FIG. 13 upwardly into the throughbores  176  of the modules  170  in the adjacent cell  164 . The coolant flows downwardly within the cell  16  until it reaches a level within the housing  128  below the lower edge of the partition wall  162  and then passes through the passage  166  into the adjacent cell  164  as shown by arrow D in FIG. 13. The pressure of the incoming exhaust and coolant forces each of these fluids respectively upwardly along the throughbores  176  and past the fins  184 , respectively. The exhaust flows upwardly through the thoughbores  176  until the exhaust reaches the second chamber  146  from which the now cooled exhaust is expelled from the cooler  124  through the fluid outlet  150  as indicated by arrow E in FIG. 13. The now-cooled exhaust is then directed to a turbocharger  242  for the engine  232 . The heated coolant rises to a level coincident with the outlet  167  and flows outwardly through this nozzle for recirculation to the coolant tank  240  as shown by arrow F in FIG. 13. The generally parallel flow paths of the exhaust and coolant, first downward through one cell  164  and then upward through the other cell  164  in a U-shaped path, allows for a very compact construction which can be easily modified to provide varying package sizes.  
         [0095]    The exhaust coolers  124  and  211  described above are particularly well suited to be used as air charge coolers for a turbocharger of a diesel engine. For this application, the top caps  126  and  212  of the respective embodiments are preferably made of stainless steel to withstand the high temperature of the exhaust gases entering the inlet  148 . The incoming exhaust gas temperature may be as high as 1200° F. The exhaust cooler of either embodiment is designed to cool the exhaust gas to a temperature of about 300° F. as it exits the outlet  150 . The lower housing  128  (or  213 ), including the heat exchange module assemblies  168  mounted therein, are preferably made of aluminum. The lower temperature of coolant through the housing, which may be supplied directly from the engine cooling system, maintains the temperature of the aluminum components sufficiently low to prevent thermal degradation. If necessary, the entire aluminum lower housing and heat exchange assemblies  168  are readily replaceable. In the embodiment of FIGS. 12 and 13, replacement of the lower section requires the removal of the mounting bolts  142 . In the embodiment shown in FIGS. 25 and 26, replacement of the lower housing  213  is much more simply accomplished by removal of the single long connecting bolt  223 .  
         [0096]    In addition to its principal intended use as an air charge cooler, either embodiment of the exhaust cooler  124  or  211  could also be adapted for use as a transmission oil cooler or other similar automotive application. As indicated above, in the primary intended use as an exhaust cooler, the incoming diesel exhaust may have a temperature as high as 1200° F. Nevertheless, it has been found that the aluminum components having a somewhat lower softening temperature remain protected by the flow of coolant therethrough as described above. However, because diesel exhaust tends to be acidic and may have a detrimental corrosive effect on aluminum, in some applications it may be desirable to coat the longitudinal through bores  76  of the module  170 , as well as the interior of the bottom portion  154  and other surfaces contacted by the exhaust, with an acid resistant coating.  
         [0097]    In FIGS. 27 and 28, there is shown an embodiment of the present invention that is particularly adapted for use as an automotive radiator or similar cooling system for an internal combustion engine. The heat exchanger  243  is made of an assembly of extruded aluminum modules  244 , each of which is similar to the previously described module  170 , except that the pattern of slots  245  cut in the outer face portions of the modules to form the fins  246  do not extend the full length of the module  244 . Instead, each module has unslotted ends  247  where there are no fins. Each of the opposite module ends  247  terminates in a shoulder  248 . Each shoulder  248 , in turn, surrounds a central axially extending neck  250  which is similar to the neck  180  in the previously described embodiment.  
         [0098]    A header plate  251  includes a flat main body portion  253  which is provided with a series of openings  252  for receipt of the necks  250  of the module assembly. The underside of the flat body portion  253  of the header plate rests on the shoulders  248  of  30  the modules. Each header plate is secured in position to the module assembly with a series of spaced welds  254  connecting the underside of the flat body portion of the header plate  251  to the unslotted ends  247  of the modules.  
         [0099]    The header plate  251  has an integral peripheral outer rim  255  that surrounds the center body portion to form, on the upper end of the heat exchanger  243 , a sealant containment chamber  256 . After the assembly of modules  244  has been secured to the header plate  251  with the welds  254 , a pourable sealant  257  is poured in a uniform layer over the bottom of the chamber  256 . The sealant  257  provides fluid tight seams between the openings  252  in the header plate and the necks  250  extending through the openings. A tank  258  having a continuous lower edge  259  sized to fit closely within the outer rim  255  of the header plate is pressed into the sealant layer  257  before the sealant hardens to form a fluid tight joint between the tank and the header plate. The sealed joint is secured by a series of tack welds between upstanding tabs  261  on the header plate and the side walls  262  of the tank.  
         [0100]    The lower header plate  251  and tank  258  are installed in the same manner with the heat exchanger inverted. To complete the heat exchanger  243  for a typical automotive application, the bottom tank is provided with an inlet connection and the top tank  258  is provided with an outlet connection and a fill opening with a pressure cap  265 . Suitable mounting brackets  266  may be conveniently attached to the outsides of the outermost modules  244  as by welding.  
         [0101]    One suitable sealant material is an RTV silicone adhesive. This material will withstand temperatures as high as 600° F. (315° C.). The sealant will thus retain its sealing capability in a typical automotive cooling system application.