Abstract:
A heat exchanger is provided. The heat exchanger includes a stack assembly with a plurality of plates and a plurality of frames arranged in an alternating stacked relationship with the plates along a predetermined direction. Each of the plates has a plurality of first openings and each of the frames has a plurality of second openings. A plurality of first and second fluid channels extends through the stack assembly along the predetermined direction and through the plurality of first and second openings. A first fluid flow path includes a first inlet channel in fluid communication with the plurality of first fluid channels, and a first outlet channel in fluid communication with the plurality of second fluid channels. A second fluid flow path is in thermal contact with the first fluid flow path and fluidically isolated from the first fluid flow path.

Description:
CLAIM FOR PRIORITY  
       [0001]     The present application claims priority from U.S. Provisional Application Ser. No.  60 / 753 , 812 , filed Dec. 23, 2005, which is fully incorporated herein. 
     
    
     TECHNICAL FIELD  
       [0002]     The present disclosure is directed to a heat exchanger, and more particularly to a stacked plate heat exchanger and method of assembly thereof.  
       BACKGROUND  
       [0003]     Plate-type heat exchangers are used for certain industrial applications in place of fin and tube or shell and tube type heat exchangers because they are less expensive and easier to make than most forms of heat exchangers. In one form of such plate-type heat exchangers, a plurality of primary surface plates are brazed together in a unitary structure with spacer frames located between adjacent plates and traversing a course adjacent to the plate peripheries. Flow of the two fluids involved in heat exchange is through alternate layers defined by the brazed plates. The space between the plates may be occupied by protuberances or fins formed in the plates to increase turbulence or heat exchange in the fluid flow. All of the fluid flowing in a given defined space is in contact with the plates to enhance heat transfer.  
         [0004]     In order to handle larger heat loads, existing plate-type heat exchangers may be scaled up in size by adding more layers or using denser configurations of layers. However, one problem that arises with some designs is that the pressure loss across the heat exchanger increases. One technique used to decrease the pressure loss is to transversely supply each layer from a single conduit. The conduit is sized to minimize any pressure drops. An example of such a heat exchanger is disclosed in U.S. Pat. No. 5,911,273 to Brenner et al. (“the &#39;273 patent”). The &#39;273 patent discloses a heat exchanger having a stacked plate construction made of four distinct parts: a cover, a flow duct plate, a connection cover plate, and a connection plate. These parts are alternated and rotated in a stack assembly. A first fluid flows into the heat exchanger through a connection opening, into a single connection conduit, then transversely through fluidically parallel layers. A second fluid has a similar flow pattern, with the heat exchange occurring across the parallel layers of the stack assembly.  
         [0005]     While the configuration of the &#39;273 patent attempts to decrease pressure losses, it results in an increased manifold volume or supply conduit volume to heat exchanger volume ratio. As the size or the number of layers in the heat exchanger increases, the size of the manifold volume increases as well. For applications requiring a compact construction, this may prove to be unacceptable. In addition, there may be non-uniform heat exchange such that layers farthest from the supply conduit inlets may receive less flow than layers closest to the supply conduit inlets.  
         [0006]     The present disclosure is directed to overcoming one or more of the problems set forth above.  
       SUMMARY OF THE INVENTION  
       [0007]     In one aspect, the present disclosure is directed to a heat exchanger. The heat exchanger includes a stack assembly with a plurality of plates and a plurality of frames arranged in an alternating stacked relationship with the plates along a predetermined direction. Each of the plates has a plurality of first openings and each of the frames has a plurality of second openings. A plurality of first and second fluid channels extends through the stack assembly along the predetermined direction and through the plurality of first and second openings. A first fluid flow path includes a first inlet channel in fluid communication with the plurality of first fluid channels and a first outlet channel in fluid communication with the plurality of second fluid channels. A second fluid flow path is in thermal contact with the first fluid flow path and fluidically isolated from the first fluid flow path.  
         [0008]     In another aspect, the present disclosure is directed to a method of making a heat exchanger including the steps of providing a plurality of plates having a plurality of first openings and providing a plurality of frames having a plurality of second openings. The method also includes the steps of alternately stacking the plates with the frames along a stack direction and aligning the plurality of first openings with the plurality of second openings to define a first and second plurality of fluid channels extending through the plates and the frames along the stack direction. The method also includes the steps of coupling a first manifold to each of the first plurality of fluid channels along the stack direction and coupling a second manifold to each of the second plurality of fluid channels along the stack direction. The method also includes the step of sealingly interconnecting the stacked plates and frames to each other. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is an exploded perspective view of one exemplary embodiment of a heat exchanger.  
         [0010]      FIG. 2  is a plan view of a cover for the heat exchanger of  FIG. 1 .  
         [0011]      FIG. 3  is a plan view of a frame layered on the cover of  FIG. 2 .  
         [0012]      FIG. 4  is a plan view of a plate of the heat exchanger of  FIG. 1 .  
         [0013]      FIG. 5  is a plan view of a frame, which is rotated 180 degrees about a stack direction from the frame of  FIG. 3 , layered on the plate of  FIG. 4 .  
         [0014]      FIG. 6  is a plan view of a plate that is rotated 180 degrees about a transverse direction from the plate of  FIG. 4 .  
         [0015]      FIG. 7  is a plan view of a frame layered on the plate of  FIG. 6 .  
         [0016]      FIG. 8  is a perspective view of a tapered insert that may be placed in the manifolds or fluid channels of  FIG. 1 .  
         [0017]      FIG. 9  is a detail view of the plate of  FIG. 1 .  
         [0018]      FIG. 10  is an exploded perspective view of another exemplary embodiment of the heat exchanger, shown with foam inserts.  
         [0019]      FIG. 11  is a detail view of the inserts of  FIG. 10 .  
         [0020]      FIG. 12  is a perspective view of a frame that may be used with another exemplary embodiment of a heat exchanger.  
         [0021]      FIG. 13  is a plan view of the frame of  FIG. 12 . 
     
    
     DETAILED DESCRIPTION  
       [0022]     Reference will now be made in detail to the drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0023]      FIG. 1  shows a heat exchanger  10 . Heat exchanger  10  includes a stack assembly  20  made up of alternating layers of plates  30  and frames  40 , a bottom cover  50 , a top cover  60 , and manifolds  82 ,  84 ,  86 , and  88 . Heat exchanger  10  is shown assembled along a stack direction  12  that is oriented vertically, but this is only for purposes of illustration.  
         [0024]     Stack assembly  20  is made up of layers of plates  30  and frames  40 . As seen in  FIG. 1 , plates  30  are flat plates formed of a thin sheet of material such as stainless steel, aluminum, brass, copper, bronze, or any other material with desired heat transfer characteristics. In addition, while plates  30  are depicted as rectangular, other shapes may also be used. In one exemplary embodiment plates  30  have dimensions of 279 mm long by 179 mm wide by 0.1 mm thick, although plates  30  of other sizes may also be used. Plates  30  may be formed by methods known in the art, such as stamping, laser beam cutting, water torch cutting, eroding, etc.  
         [0025]     As seen in  FIG. 4 , a first and second row  34 ,  36  of openings  32  are positioned along parallel edges of plate  30 . Openings  32  in each of first and second row  34 ,  36  are spaced a distance of “d” apart. In one exemplary embodiment, openings  32  are symmetrically aligned on opposite edges of plate  30 , although other configurations may also be used.  
         [0026]     In addition, as seen in  FIGS. 1, 4 , and  9 , plates  30  are integrally formed with a plurality of turbulators  38  arranged in an array  39 . As seen in  FIG. 9 , plates  30  may be formed such that adjacent turbulators  38  have opposite configurations with respect to stack direction  12 . One turbulator  38   a  may project out of plate  30  along stack direction  12 , while an adjacent turbulator  38   b  may project into plate  30  along stack direction  12 . In one exemplary embodiment, turbulators  38  have a height of 1 mm, or one half the thickness of frames  40 . As seen in  FIG. 4 , the turbulators  38  may be oriented at an angle of “θ1” to a transverse direction  14 , which is approximately twenty degrees in one exemplary embodiment.  
         [0027]     As seen in  FIGS. 5 and 7 , frames  40  are sized to have similar outer dimensions to that of plates  30 , and may also be made of similar materials. Frames  40  also may have a thickness of approximately twice the height of turbulator  38 , which in one exemplary embodiment is 2 mm, although other thicknesses may be used. As seen in  FIG. 3 , frames  40  also have a first and second row  44 ,  46  of alternating openings  42  and voids  43  that are positioned along parallel edges. Openings  42  in each of first and second row  44 ,  46  are spaced a distance of “2d” apart, and are enclosed within the interior periphery  41  of frame  40 . Voids  43  are also formed in the interior periphery  41  of frame  40  and are spaced a distance of “2d” apart, such that each opening  42  is spaced a distance of “d” from an adjacent void  43 . This spacing between voids  43  and openings  42  is maintained for both first row  44  and second row  46 . In addition, the openings  42  and voids  43  in first and second row  44 ,  46  may be symmetrically aligned along parallel edges of frame  40 , such that the openings  42  and voids  43  in the first row  44  are mirror images of the openings  42  and voids  43  in the second row  46 . Openings  42  and voids  43  are sized to match the openings  32  in plates  30 , although they may be slightly increased or decreased to facilitate alignment and sealing.  
         [0028]     As seen in  FIG. 1 , stack assembly  20  begins with a frame  40 . A first plate  30  is aligned on the frame  40 . A second frame  40 , which is rotated 180 degrees about the stack direction  12  from the first frame  40 , is placed on the plate  30 . A second plate  30 , rotated 180 degrees about a transverse direction  14 , is placed onto the frame  40 . As seen in  FIG. 6 , the turbulators  38  of the second plate  30  are symmetrically disposed about the transverse direction  14 , such that “θ2” is equal to the “θ1” shown in  FIG. 1 . The stack continues in this fashion, alternating frames  40  and plates  30 , with successive frames  40  and plates  30  rotated 180 degrees about a transverse direction  14  from the preceding one.  
         [0029]     Stack assembly  20  is placed onto a bottom cover  50 . As seen in  FIG. 2 , bottom cover  50  has a first and second row  54 ,  56  of openings  52  positioned along parallel edges. Openings in first and second row  52  are positioned a distance of “2d” apart. In addition, a series ridges  51  may extend across an inner surface of bottom cover  50 . Depending on the orientation, these ridges  51  may serve to direct the flow of fluid across the cover, turbulate the water, and/or increase heat exchange. The openings  52  in first and second row  54 ,  56  of bottom cover  50  are laterally offset a distance of “d”, such that the first and second rows  54 ,  56  of openings  52  are not symmetric along the length of the cover. Bottom cover  50  may be sized with substantially the same outer dimensions as frame  40  or plate  30 .  
         [0030]     As seen in  FIG. 1 , a top cover  60  is placed at the top of the stack assembly  20 . Top cover  60  has a first and second row  64 ,  66  of openings  62  positioned on parallel edges. In one exemplary embodiment, top cover  60  is identical to bottom cover  50 . However, in assembling top cover  60  to stack assembly  20 , top cover  60  is rotated 180 degrees about a transverse direction  14  with respect to bottom cover  50 . Other aspects of top cover  60  are similar to bottom cover  50 , shown in  FIGS. 1 and 2  and described above.  
         [0031]     As the heat exchanger  10  is stacked, the alignment of openings  32 ,  42 ,  52  and voids  43  in the plates  30 , frames  40 , and covers  50 ,  60  define a plurality of fluid channels  95 ,  96 ,  97 ,  98  that extend through the stack assembly  20  along the stack direction  10 . Fluid channels  95 ,  96  are defined in the first row  34 ,  44 ,  54 ,  64  of plates  30 , frames  40 , and covers  50 ,  60 , while fluid channels  97 ,  98  are defined in the second row  36 ,  46 ,  56 ,  66  of plates  30 , frames  40 , and covers  50 ,  60 . In one exemplary embodiment, fluid channels  95 ,  96  alternate openings  32 ,  42 ,  52 ,  62  and voids  43  throughout first row  34 ,  44 ,  54 ,  64 , so that each fluid channel  95  is adjacent a fluid channel  96 . Similarly, fluid channels  97 ,  98  alternate openings  32 ,  42 ,  52 ,  62  and voids  43  throughout second row  36 ,  46 ,  56 ,  66 , so that each fluid channel  97  is adjacent a fluid channel  98 .  
         [0032]     As seen in  FIG. 1 , each of manifolds  82 ,  84 ,  86 , and  88  is positioned over the first and second row of openings  54 ,  56 ,  64 ,  66  of top and bottom covers  60 ,  50 . Manifolds  82 ,  84 ,  86 , and  88  each serve as fluid conduits. Manifolds  82  and  84  function as an inlet and outlet, respectively, for a first fluid, such as hot engine oil. Manifolds  86  and  88  function as an inlet and outlet, respectively, for a second fluid, such as coolant.  
         [0033]     As seen in  FIG. 8 , tapered inserts  90  may be placed in manifolds  82 ,  84 ,  86 , and  88 . In one exemplary embodiment of the present invention, inserts  90  are placed in the first and second fluid outlet manifolds  84  and  88 . These inserts serve to equalize the pressure drop across the heat exchanger so that there is a substantially equal flow and heat exchange between fluids across the length and height of the heat exchanger  10 . Alternately, inserts  90  may be placed in the fluid channels  95 ,  96 ,  97 ,  98  extending along the stack direction  12 , designated as “h” and “c” in first and second row  34 ,  36  in  FIG. 4 . The inserts  90  may be integrally formed with manifolds  82 ,  84 ,  86 , and  88 , or sealed to the manifolds  82 ,  84 ,  86 , and  88  in a separate step. Inserts  90  may be made from stainless steel, aluminum, brass, copper, bronze, or other material with desired heat transfer characteristics.  
         [0034]      FIGS. 10-11  illustrate another exemplary embodiment of the present invention. Foam inserts  100  are placed within the interior periphery  141  of frames  140 . Foam inserts  100  may be made from a porous metal or carbon as described in U.S. Pat. Nos. 3,616,841 and 3,946,039 to Walz, U.S. Pat. App. No. 2004/0226702 to Toonen, or U.S. Pat. No. 6,673,328 to Klett. Inserts  100  have large surface area per unit volumes (approximately 1600 square feet/cubic foot).  
         [0035]     These inserts may be placed in the interior periphery  141  of every frame  140 , or only used with alternate frames  140 , as is shown in  FIG. 10 . As is shown in  FIG. 10 , plates  130  are formed with only a single surface of turbulators  38 . Other aspects of heat exchanger  110  are similar to the heat exchanger  10  shown in  FIG. 1  and described above.  
         [0036]     In another exemplary embodiment, a gas to fluid heat exchanger (not shown) may be constructed by substituting layers of frames  340 , as shown in  FIGS. 12 and 13 , with every other frame  40 ,  140  in heat exchangers  10 ,  110  as shown in  FIGS. 1 and 10 . Similar to frames  40  and  140 , frame  340  has a first and second row  344 ,  346  of alternating openings  342  and voids  343  that are positioned along parallel edges. A plurality of transverse openings  348  extend through the voids  343  in both the first and second row  344 ,  346 . These transverse openings  348  permit a transverse flow  390  along the transverse direction  14  to flow past the turbulators  38  and through the frame  340 , providing heat transfer to alternate plates  30 ,  130 . These transverse openings  348  open the heat exchanger to ambient air, allowing for an air-to-fluid heat exchanger. Such a heat exchanger could also eliminate one set of manifolds.  
         [0037]     Heat exchangers  10 ,  110  may be formed using a brazing operation. Before assembly, a flux is applied to the peripheries of each of manifolds  82 ,  84 ,  86 ,  88 ; covers  50 ,  60 , frames  40 , and plates  30 . Thin sheets of solder may be placed between each layer to ensure a solder seal extending around the entire periphery. After assembly, the heat exchanger  10 ,  110  may be clamped together and heated to form a sealed unit. Alternately, the heat exchanger  10 ,  110  may be formed from any other technique known in the art, such as welding.  
       INDUSTRIAL APPLICABILITY  
       [0038]     In operation, a first and a second fluid flow path  92 ,  94  are defined through the heat exchanger  10 ,  110 . A first fluid, such as heated engine oil, follows first fluid flow path  92  and enters through manifold  82 . From manifold  82 , the first fluid next flows into the fluid channels  96  extending through the stack assembly  20  defined by the first row  54  of openings  52  in the bottom cover  50  (as seen in  FIG. 2 , designated by “h”). From the flow channels, the first fluid flows through voids  43  in the first row  44  of alternate frames  40 ,  140  flowing across the turbulators  38  of primary surface sheets or plates  30 ,  130 . The flow path  92  continues into voids  43  in the second row  46  of alternate frames  40 ,  140  and back through fluid channels  98  extending through the stack assembly  20  (“designated by “h” in the second row  36  in  FIG. 4 ). Flow path  92  continues from the fluid channels  98  in the second row to manifold  84 , where it exits after being cooled by the heat exchange with the second fluid.  
         [0039]     Similarly, a second fluid, such as coolant, follows second fluid flow path  94  and enters through manifold  86 . From manifold  86 , the second fluid next flows into fluid channels  97  extending through the stack assembly  20  defined by the second row  56  of openings  52  in the bottom cover  50  (as seen in  FIG. 2 , designated by “c”). From the fluid channels  97 , the second fluid flows through voids  43  in the second row  46  of alternate frames  40 ,  140  flowing across the turbulators  38  of primary surface sheets or plates  30 . The flow path  94  continues into voids  43  in the first row  46  of alternate frames  40 ,  140  and back through fluid channels  95  extending through the stack assembly  20  (“designated by “c” in the first row  36  in  FIG. 4 ). Flow path  94  continues from the fluid channels  95  in the second row to manifold  88 , where it exits after being heated by the heat exchange with the first fluid. Alternately, the first and second fluid flow paths  92 ,  94  may be reversed. In addition, the first and second fluid inlets may feed into the upper manifolds  88 ,  84  instead of the lower manifolds  82 ,  86 , or any other combination. Fluid flow path  92  is fluidically isolated from fluid flow path  94 .  
         [0040]     Foam inserts  100  or turbulators  38  may also be used to increase the heat exchange that occurs across primary surface sheet or plate  30 ,  130 . Additional heat exchange may also occur in alternating channels in each of the first and second rows (as seen in  FIG. 2 , adjacent “h” and “c”).  
         [0041]     It will be apparent to those having ordinary skill in the art that various modifications and variations can be made to the disclosed heat exchanger without departing from the scope of the invention. Other embodiments of the invention will be apparent to those having ordinary skill in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the invention being indicated by the following claims and their equivalents.