Counterflow plate-fin heat exchanger with extended header fin

Abstract

A plate-fin heat exchanger includes a stacked array of cells. Each cell includes top and bottom sheets defining manifolds and header finned members disposed between the top and bottom sheets. The top and bottom sheets include substantially planar portions, diverging portions angled with respect to the planar portions, and divergence edges defined between the planar and diverging portions. The header finned member extends beyond the divergence edges of the top and bottom sheets and is supported in cantilevered fashion within the manifold.

1 . A recuperated microturbine engine comprising: 
 an air compressor operable to create a flow of compressed air;    a combustor operable to mix the flow of compressed air with a fuel, and operable to combust the fuel/air mixture to create an expanding flow of products of combustion;    a turbine and generator assembly communicating with said combustor and operable in response to the expanding flow of products of combustion to generate electricity, said turbine and generator assembly exhausting a flow of hot exhaust gases; and    a recuperator including at least one cell through the inside of which said flow of compressed air flows, and around the outside of which the flow of exhaust gases flows, said recuperator preheating the flow of compressed air with heat from the flow of exhaust gases before the flow of compressed air is delivered to said combustor, said recuperator cell having top and bottom sheets and at least one header finned member sandwiched between and metallurgically bonded to said top and bottom sheets within the inside of said cell, said recuperator also including inlet and outlet manifolds communicating with the inside of said cell to direct the flow of the compressed air into and out of said cell, respectively;    wherein said header finned member includes a cantilever portion that is not directly metallurgically bonded to said top and bottom sheets and that extends into one of said inlet and outlet manifolds in a cantilever fashion, said cantilever portion including a free end edge within said manifold;    wherein said flow of compressed air creates a high pressure environment within said cell, which environment imparts tensile stresses to said header finned member; and    wherein said free end edge is subject to a substantially reduced state of tensile stress due to said cantilever extension of said header finned member into said manifold.    
     
     
         2 . The engine of  claim 1 , wherein said header finned member is a first header finned member, said first header finned member extending into said inlet manifold, and wherein said cell further includes a second header finned member metallurgically bonded to said top and bottom sheets and having a cantilever portion extending into said outlet manifold.  
     
     
         3 . The engine of  claim 1 , wherein said at least one cell includes a plurality of substantially identical cells arranged in a stacked configuration, said plurality of cells being metallurgically bonded to each other, and wherein said cells define exhaust gas flow spaces between said cells through which the flow of exhaust gases flows.  
     
     
         4 . The engine of  claim 1 , wherein said top and bottom sheets each include a substantially flat portion, a diverging portion angled with respect to said substantially flat portion, and a divergence edge defined between said substantially flat portion and said diverging portion, wherein said flat portions of said top and bottom sheets are substantially parallel to each other, wherein said diverging portion of said top sheet extends away from said bottom sheet and said diverging portion of said bottom sheet extends away from said top sheet, and wherein said cantilever portion is cantilevered with respect to said divergence edges.  
     
     
         5 . The engine of  claim 4 , wherein said header finned member is metallurgically bonded to said flat portions of said top and bottom plates.  
     
     
         6 . The engine of  claim 4 , wherein said divergence edge at least partially defines a boundary of one of said inlet and outlet manifolds.  
     
     
         7 . A heat exchanger cell comprising: 
 top and bottom sheets each including a manifold opening, said top and bottom sheets being positioned in stacked relation relative to one another to align their respective manifold openings; and    a header finned member disposed between and metallurgically bonded to said top and bottom sheets, said header finned member having a cantilever portion extending into said manifold openings in cantilever fashion, said cantilever portion being free from a direct metallurgical bond to said top and bottom sheets, said cantilever portion terminating in a free end edge;    wherein said cell is adapted to receive a high pressure fluid therein that creates tensile stresses in said header finned member; and    wherein the tensile stresses on said free end edge are substantially less than those on the portion of said header finned member that is metallurgically bonded to said top and bottom sheets by virtue of said cantilever portion being free from direct metallurgical bond to said top and bottom sheets.    
     
     
         8 . The cell of  claim 7 , wherein said top and bottom sheets each include a substantially planar portion, a diverging portion, and a divergence edge defined between said planar and diverging portions, and wherein said cantilever portion is cantilevered with respect to said divergence edge of at least one of said top and bottom sheets.  
     
     
         9 . A plate-fin heat exchanger comprising a first cell including: 
 a top sheet and a bottom sheet each having a substantially planar portion and a diverging portion angled with respect to said planar portion and joined to said planar portion along a divergence edge, said diverging portion of each sheet at least partially defining a manifold opening generally aligned with a manifold opening at least partially defined by the diverging portion of the other sheet; and    a formed member between and metallurgically bonded to said planar portions of said top and bottom sheets and having a cantilever portion extending into said manifold openings and terminating in a free end edge, said cantilever portion being free from a direct metallurgical bond to said top and bottom sheets;    wherein said diverging portions of said top and bottom sheets both extend away from said finned member and wherein said divergence edges of said top and bottom sheets are metallurgically bonded to said finned member, and said cantilever portion is cantilevered with respect to said divergence edge.    
     
     
         10 . The plate-fin heat exchanger of  claim 9 , further comprising a second cell substantially identical to said first cell and including a top sheet having a diverging portion metallurgically bonded to said diverging portion of said bottom sheet of said first cell.