Recuperative Heat Exchanger, Fuel Cell System Including Recuperative Heat Exchanger, and Method of Operating Same

Abstract

A heat exchanger, such as a cathode recuperator for a high temperature fuel cell system, has a corrugated separator, a barrier and a plurality of flow channels. The corrugated separator has a surface positioned along a heat exchange fluid flow path, opposite ends of the separator having flattened corrugations. The barrier is positioned adjacent the surface. The plurality of flow channels are in the heat exchange fluid flow path and are at least partially defined by the surface and the barrier. The flattened corrugations are positioned adjacent crests in the corrugated separator and secured to the barrier.

1 . A heat exchanger comprising:
 a corrugated metal separator having a surface positioned along a heat exchange fluid flow path, opposite ends of the separator having flattened corrugations;   a barrier positioned adjacent the surface; and   a plurality of flow channels in the heat exchange fluid flow path at least partially defined by the surface and the barrier;   wherein the flattened corrugations are secured to the barrier.   
     
     
         2 . The heat exchanger of  claim 1 , wherein the heat exchange fluid flow path is a first heat exchange fluid flow path, wherein the surface is a first surface, wherein the barrier is a first barrier and wherein the plurality of flow channels are a first plurality of flow channels, wherein the corrugated separator further includes a second surface positioned along a second heat exchange fluid flow path, the heat exchanger further comprising:
 a second barrier positioned adjacent the second surface; and   a second plurality of flow channels in the second heat exchange fluid flow path bounded by the second surface and the second barrier;   wherein the first barrier and the second barrier are substantially concentric cylinders, and wherein the first barrier is located radially inward from the second barrier.   
     
     
         3 . The heat exchanger of  claim 2 , wherein the corrugated separator includes a first flattened region adjacent a first end of the separator, a second flattened region adjacent a second end of the separator, a corrugated region between the first flattened region and the second flattened region, a first transition region connecting the first flattened region and a first end of the corrugated region, and a second transition region connecting the second flattened region and a second end of the corrugated region, and wherein the first barrier includes an inlet to the first heat exchange fluid flow path, the inlet being positioned proximate the first end of the corrugated region. 
     
     
         4 . The heat exchanger of  claim 3 , wherein the inlet includes a plurality of trapezoid-shaped openings. 
     
     
         5 . The heat exchanger of  claim 3 , wherein the first barrier includes an outlet from the first heat exchange fluid flow path, the outlet being positioned proximate the second end of the corrugated region. 
     
     
         6 . The heat exchanger of  claim 5 , wherein the outlet includes a plurality of trapezoid-shaped openings. 
     
     
         7 . The heat exchanger of  claim 1 , wherein the corrugated separator includes crests, wherein the crests are secured to the barrier by one of soldering, brazing, welding, adhesive bonding, and cohesive bonding. 
     
     
         8 . The heat exchanger of  claim 1 , wherein the corrugated separator is formed into a substantially cylindrical shape. 
     
     
         9 . The heat exchanger of  claim 8 , wherein the corrugated separator includes corrugations extending in a direction substantially parallel to a central axis of the substantially cylindrical shape. 
     
     
         10 . The heat exchanger of  claim 1 , wherein the corrugated separator includes a longitudinal direction in which the corrugations extend, wherein the corrugated separator includes a first flattened region adjacent a first longitudinal end of the separator, a second flattened region adjacent a second longitudinal end of the separator, a corrugated region between the first flattened region and the second flattened region, a first transition region connecting the first flattened region and a first end of the corrugated region, and a second transition region connecting the second flattened region and a second end of the corrugated region, and wherein the first transition region and the first flattened region include corrugations bent in a direction transverse to the longitudinal direction, the corrugations overlapping adjacent corrugations in the first flattened region. 
     
     
         11 . The heat exchanger of  claim 1 , wherein the flattened corrugations secured to the barrier substantially seal off the heat exchange fluid flow path. 
     
     
         12 . The heat exchanger of  claim 1 , wherein the corrugations include a plurality of peaks and troughs, and wherein the flattened corrugations are located adjacent one of the peaks and the troughs. 
     
     
         13 . A method of making a heat exchanger, the method comprising the acts of:
 providing a corrugated metal separator sheet having metal corrugations extending in a longitudinal direction;   flattening the metal corrugations into flattened portions positioned at first and second longitudinal ends of the corrugated separator sheet;   positioning the corrugated separator sheet adjacent a non-corrugated barrier to create a heat exchange flow path between the corrugated separator sheet and the non-corrugated barrier; and   securing the flattened portions to a surface of the non-corrugated barrier.   
     
     
         14 . The method of  claim 13 , further comprising:
 forming the corrugated separator sheet into a corrugated cylinder by joining a first corrugation located at a first edge oriented parallel to the corrugations and a second corrugation located at a second edge oriented parallel to the corrugations.   
     
     
         15 . The method of  claim 13 , wherein the act of flattening further comprises:
 positioning the corrugated separator sheet adjacent a sleeve such that crests of the corrugated separator sheet engage the sleeve;   positioning the corrugated separator sheet and sleeve between two wheels spaced apart a distance smaller than a height of the corrugations;   rotating the two wheels in opposite directions to feed the corrugated separator sheet and sleeve between the two wheels, thereby forming one of the flattened portions flush with the crests.   
     
     
         16 . The method of  claim 13 , wherein the sleeve is substantially cylindrical. 
     
     
         17 . The method of  claim 13 , wherein the non-corrugated barrier is a first non-corrugated barrier, the method further comprising:
 positioning the corrugated separator sheet between the first non-corrugated barrier and a second non-corrugated barrier to define a first heat exchange fluid flow path on a first side of the corrugated separator sheet and a second heat exchange fluid flow path on a second side of the corrugated separator sheet.   
     
     
         18 . The method of  claim 17 , wherein positioning the corrugated separator sheet between the first non-corrugated barrier and a second non-corrugated barrier includes positioning the corrugated separator sheet in a substantially cylindrical space. 
     
     
         19 . The method of  claim 17 , further comprising:
 providing an inlet to the first heat exchange fluid flow path, the inlet being positioned proximate a first end of the corrugations; and   providing an outlet to the first heat exchange fluid flow path, the outlet being positioned proximate a second end of the corrugations;   wherein the acts of providing an inlet and providing an outlet include creating apertures in one of the non-corrugated barriers.   
     
     
         20 . The method of  claim 19 , wherein the act of creating apertures includes creating apertures in the non-corrugated barrier to which the flattened portions are secured. 
     
     
         21 . The method of  claim 13 , further comprising securing crests of the corrugated separator sheet to the non-corrugated barrier. 
     
     
         22 . A corrugated separator sheet for a heat exchanger, the corrugated separator sheet comprising:
 a plurality of metal corrugations extending parallel to one another in a longitudinal direction, the corrugations having a plurality of peaks and a plurality of troughs opposite the plurality of peaks; and   a flattened region proximate a longitudinal end of the separator sheet;   wherein the flattened region is adjacent the plurality of peaks.   
     
     
         23 . The corrugated separator sheet of  claim 22 , wherein the flattened region is substantially flush with the plurality of peaks. 
     
     
         24 . The corrugated separator sheet of  claim 22 , wherein the corrugated separator sheet is cylindrical. 
     
     
         25 . The corrugated separator sheet of  claim 22 , wherein the flattened region is a first flattened region, and wherein the longitudinal end is a first longitudinal end, further comprising a second flattened region proximate a second longitudinal end of the separator sheet, wherein the second flattened region is adjacent one of the plurality of peaks and the plurality of troughs. 
     
     
         26 . The corrugated separator sheet of  claim 25 , wherein the first flattened region is secured to a first cylindrical barrier and the plurality of troughs are positioned adjacent a second cylindrical barrier, wherein a first flow path is defined between the corrugated separator sheet and the first cylindrical barrier and a second flow path is defined between the corrugated separator sheet and the second cylindrical barrier. 
     
     
         27 . The corrugated separator sheet of  claim 26 , wherein the second flattened region is adjacent the plurality of peaks, wherein the second flattened region is secured to the first cylindrical barrier. 
     
     
         28 . The corrugated separator sheet of  claim 26 , further comprising a corrugated region between the first flattened region and the second flattened region, a first transition region connecting the first flattened region and a first end of the corrugated region, and a second transition region connecting the second flattened region and a second end of the corrugated region, wherein the first cylindrical barrier includes an inlet to the first flow path, the inlet being positioned proximate the first end of the corrugated region. 
     
     
         29 . The corrugated separator sheet of  claim 22 , wherein the flattened region is a first flattened region and the longitudinal end is a first longitudinal end, the corrugated separator sheet further comprising:
 a second flattened region adjacent a second longitudinal end of the separator sheet;   a corrugated region between the first flattened region and the second flattened region;   a first transition region connecting the first flattened region and a first end of the corrugated region; and   a second transition region connecting the second flattened region and a second end of the corrugated region;   wherein the first transition region and the first flattened region include corrugations bent in a direction transverse to the longitudinal direction, the corrugations overlapping adjacent corrugations in the first flattened region.