Abstract:
An air-to-air heat exchanger, is provided that comprises a folded fin core formed from a continuous sheet of thermally conductive material that has been folded into alternating flat ridges and troughs; an insert overlay having an opening including two sets of uniform fingers, wherein each finger has a portion protruding into and essentially filling each trough on one surface of the folded fin core; an inset region between each finger portion and the end edges of each trough; a sealant within each inset region sealably attaching the insert overlay to the folded fin core; and an air flow divider plate. Heat exchanger components are also provided.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is related to and claims priority from U.S. Provisional Patent Application No. 60/552,414, filed on Mar. 11, 2004. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to heat-exchangers, and more particularly to heat-exchangers of the type including plates arranged side-by-side and mutually parallel. 
     BACKGROUND OF THE INVENTION 
     Heat-exchangers having a plurality of mutually parallel plates, with channels that are adapted to carry at least one heat transfer fluid, are well known in the art. Such parallel plate devices are often formed by folding a continuous sheet of metal to yield a so called “folded-fin” heat exchanger. The plates in such prior art heat-exchangers sometimes form a circuit path for circulation of two independent fluids, in counterflow, from one end of the heat-exchanger to the other. The plates are often connected to one another at their longitudinal edges by longitudinal braces or the like that are fixed together by a leak-tight wall extending over the entire length and height of the bundle of plates. The plates define a central zone for heat exchange between the fluids. 
     In some prior art heat exchange structures, the plates may have one or more corrugated sheets positioned between them, along the entire central heat transfer and exchange zone, to enhance heat exchange with the plates by increasing surface area and introducing turbulence in the flowing liquids. For example, U.S. Pat. No. 5,584,341, discloses a plate bundle for a heat-exchanger including a stack of mutually parallel metal heat-exchange plates. Each heat-exchange plate includes smooth-surfaced edges and a corrugated central portion which, with the associated heat-exchange plates, forms a double circuit for circulation of two independent fluids in counterflow. The plates are connected to one another at their longitudinal edges by connection structures, and have a zone of heat transfer and exchange between the fluids. Another zone is formed at the free ends of the plates for inlet and outlet of the fluids. The fluid inlet and outlet zones are formed by the plane ends of the heat-exchange plates. 
     A significant disadvantage in prior art heat-exchangers of this type is the inherent thermal impedance, i.e., resistance to thermal conduction through the thickness of the plate, associated with the materials used to form the heat-exchange plates. These prior art heat-exchange plates must have sufficient thickness so as to provide the requisite structural integrity needed for the physical demands that are placed upon such devices in normal use. Very often, the heat exchange plates are required to structurally support a portion of the heat exchanger. These design requirements typically require a minimum material thickness (e.g., a material thickness that is some minimum percentage of the plate&#39;s width or length) that results in a disadvantageously large inherent thermal impedance. Material selection is also dictated by this requirement, normally resulting in only metals being selected for the heat-exchange plates. Polymer materials typically exhibit significant dielectric and thermal insulating properties that preclude their use in heat-exchange plates, especially when they are required to provide structural integrity to the device. 
     U.S. Pat. No. 6,408,941, discloses a folded fin heat-exchanger that provides for the use of very thin materials and even polymeric materials such as one or more of the well known engineering polymers, e.g., polyhalo-olefins, polyamides, polyolefins, poly-styrenes, polyvinyls, poly-acrylates, polymethacrylates, polypropylene, polyesters, polystyrenes, polydienes, polyoxides, polyamides and polysulfides and their blends, co-polymers and substituted derivatives thereof, in its fabrication. However, there continues to be a need for enhanced air-to-air heat exchangers that are low cost and simple to manufacture. 
     SUMMARY OF THE INVENTION 
     The present invention provides an air-to-air heat exchanger having a folded fin core that includes a plurality of substantially parallel, thin fin walls that are spaced apart from one another by alternating ridges and troughs so as to define a top face and a bottom face. A frame is positioned in overlying relation to the folded fin core. The frame includes a pair of spaced-apart confronting lateral rails and a pair of spaced apart longitudinal rails that together define the central opening. A plurality of fingers project inwardly and downwardly from an interior side of each of the lateral rails so that one of the plurality of fingers is sealingly received within each trough of the folded fin core. The air-to-air heat exchanger also includes an air flow divider plate positioned in overlying relation to the top face and between the lateral rails. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be more fully disclosed in, or rendered obvious by, the following detailed description of the preferred embodiment of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein: 
         FIG. 1  is a perspective view of an air-to-air heat exchanger formed in accordance with the present invention showing a folded fin core, an insert overlay, a sealed inset region, and an air flow divider plate; 
         FIG. 2  is an exploded perspective view of the air-to-air heat exchanger shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of a folded fin core; 
         FIG. 4  is an end view a folded fin core; 
         FIG. 5  is a top plan view of a flat sheet precursor of an inset overlay; 
         FIG. 6  is a perspective view of the flat sheet precursor shown in  FIG. 5 ; 
         FIG. 7  is a perspective view of an insert overlay produced from the flat sheet precursor shown in  FIGS. 5 and 6 ; 
         FIG. 8  is a top plan view of the insert overlay shown in  FIG. 7 ; 
         FIG. 9  is an enlarged, partially cross-sectional view of bent and unbent finger portions of the insert overlay shown in  FIG. 7 ; 
         FIG. 10  is a cross-sectional view of an assembled air-to-air heat exchanger, as taken along line  10 — 10  in  FIG. 1 ; 
         FIG. 11  is a broken-away, cross-sectional view of the inset shown in  FIG. 10 ; 
         FIG. 12  is a cross-sectional view of the final assembled heat exchanger, as taken along line  12 — 12  in  FIG. 1 ; 
         FIG. 13  is a partially exploded, perspective view of one alternative embodiment of the air-to-air heat exchanger invention including folded fin inserts; 
         FIG. 14  is a perspective view of the air-to-air heat exchanger shown in  FIG. 13 , with the folded fin inserts fully assembled; and 
         FIG. 15  is a side plan view of the air-to-air heat exchanger shown in  FIG. 14 ; 
         FIG. 16  is a broken-away, enlarged view of a portion of the air-to-air heat exchanger shown in  FIG. 15 ; and 
         FIGS. 17–19  comprise end-on views of a variety of folded fin inserts that may be used in connection with the air-to-air heat exchanger shown in  FIGS. 13–16 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. In the claims, means-plus-function clauses are intended to cover the structures described, suggested, or rendered obvious by the written description or drawings for performing the recited function, including not only structural equivalents but also equivalent structures. 
     Referring to  FIGS. 1–4 , an air-to-air heat exchanger  1  formed in accordance with the present invention includes a folded fin core  5 , an insert overlay  10 , sealed inset regions  15 , and an air flow divider plate  20 . Folded fin core  5  includes a plurality of substantially parallel, thin fin walls  22  that are spaced apart from one another by alternating flat ridges  25  and troughs  27 , a top face  29  and a bottom face  31 . Each pair of thin fin walls  22  are spaced apart by flat ridge  25  so as to form each trough  27 . Folded fin core  5  also includes end fin walls  34 . Folded fin core  5  may be formed by folding a continuous sheet of thermally conductive material, such as a metal or a polymer, back-and-forth upon itself so as to create a pleated or corrugated cross-sectional profile. Folded fin core  5  may be formed from any of the metals known for having superior heat transfer and structural properties, such as stainless steel, aluminum and its alloys, copper and its alloys, as well as other thermally conductive metals and combinations of metals. Alternatively, folded fin core  5  may be formed from a polymer, such as one or more of the well known engineering polymers, e.g., polyhalo-olefins, polyamides, polyolefins, poly-styrenes, polyvinyls, poly-acrylates, polymethacrylates, polypropylene, polyesters, polystyrenes, polydienes, polyoxides, polyamides and polysulfides and their blends, co-polymers and substituted derivatives thereof. 
     Referring to FIGS.  2  and  5 – 11 , insert overlay  10  includes a frame  38  formed from a pair of spaced-apart lateral rails  40  and a pair of spaced apart longitudinal rails  42  that together define a central opening  45 . In a preferred embodiment of the invention, insert overlay  10  has a generally rectangular shape, with rails  40  and  42  including mounting holes  46 . A plurality of spaced apart, parallel fingers  48  project inwardly from an interior side of each lateral rail  40  toward the opposing lateral rail  40  ( FIGS. 5 and 6 ). Prior to assembly to folded fin core  5 , fingers  48  are bent downwardly relative to frame  38  by approximately 90° ( FIG. 7 ). Adjacent fingers, among plurality of fingers  48 , are arranged and spaced apart so as to be complementary to corresponding troughs  27  in folded fin core  5 . 
     Referring to FIGS.  1 , 2 , 10 – 12 , air flow divider plate  20  is formed from a substantially flat sheet of metal or polymer that is sized and shaped to correspond to at least a portion of top face  29  of folded fin core  5  that is bounded by frame  38 . 
     Referring to  FIG. 2 , air-to-air heat exchanger  1  is assembled in the following manner. Folded fin core  5  is positioned below insert overlay  10  so that longitudinal rails  42  are in substantially parallel spaced relation with flat ridges  25 . In this position, fingers  48  are arranged in spaced confronting relation to corresponding troughs  27  of folded fin core  5 . Once in this position, insert overlay  10  is moved toward folded fin core  5  so that each individual finger  48  is received within an individual trough  27  of folded fin core  5 . Insert overlay  10  continues to move toward folded fin core  5  until the tips of fingers  48  engage the interior surfaces of flat ridges  25  at the bottom of their respective troughs  27 . A suitable sealant material, e.g., silicone rubber or the like, is applied between fingers  48  and each thin fin wall  22  that forms its respective trough  27 . In this position, lateral rails  40  of frame  38  extend beyond the free end edge of folded fin core  5 , with longitudinal rails  42  positioned in parallel relation to flat ridges  25  and troughs  27 , and above end fin walls  34 . Once insert overlay  10  has been affixed to folded fin core  5 , air flow divider plate  20  is positioned between longitudinal rails  42  of frame  38 , so as to be in spaced parallel relation to lateral rails  40  of frame  38  and overlying top face  29  of folded fin core  5 . Air flow divider plate  20  is then fastened to frame  38  and folded fin core  5  by conventional fastening techniques known in the art, e.g., welding, brazing, adhesives, or the like. 
     In operation, air-to-air heat exchanger  1  is positioned so that air flow is created on one side of air flow divider plate  20 . Heat laden air passes through troughs  27  thereby exchanging heat through conduction with thin fin walls  22 . The flowing air exits air-to-air heat exchanger  1  from adjacent the air flow divider plate  20 . The conductive exchange of heat within air-to-air heat exchanger  1  may be enhanced by introducing fin inserts  50  ( FIGS. 13–17 ). More particularly, additional thermal conduction surfaces are provided between adjacent thin fin walls  22  by introducing fin inserts  50  ( FIGS. 13 and 14 ). Each fin insert  50  includes a plurality of substantially parallel insert walls  53  that are separated from one another by alternating flat ridges  55  and troughs  57 . Each pair of insert walls  53  are spaced-apart by a flat ridge  55  so as to form each trough  57  between them. Thus, each fin insert  50  comprises a continuous sheet of thermally conductive material folded into alternating flat ridges  55  and troughs  57  defining spaced insert walls  53 . Each flat ridge  55  provides a flat top surface that is more suitable for brazing, soldering, or welding, or otherwise thermally attaching flat ridge  55  to confronting surfaces of thin fin walls  22  ( FIGS. 15–16 ). Advantageously, the introduction of fin inserts  50  into air-to-air heat exchanger  1  acts to reduce the pneumatic cross-section thereby increasing the pneumatic pressure exerted by a coolant fluid against thin fin walls  22 . This arrangement helps to increase conductive heat transfer from air-to-air heat exchanger  1  to the flowing coolant fluid, e.g., air. Of course, pointed or rounded ridges  61  ( FIGS. 17–19 ) may also be incorporated into fin insert  50 . 
     It is to be understood that the present invention is by no means limited only to the particular constructions herein disclosed and shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.