Apparatus for fusion bonding tubular recuperator structures

Abstract

The novel embodiments disclosed herein also illustrate a novel method for making a recuperator structure. First and second pluralities of layers of elongated tubes are provided which are formed of a glass that is thermally crystallizable to a low expansion glass-ceramic. Each of the tubes is filled with a fluid medium that is expansible in response to the application of heat and the tubes have sealed ends to retain the expansible fluid medium entrapped therein. Each of the tubes has an essentially straight central portion and header connector portions continuing from each end of the central tube portions to the sealed end of the tube. The header connector tube portions of the first plurality of layers diverge away from the header connector tube portions of the second plurality of layers at the ends of the central tube portions when the first and second layers are placed on top of each other. The central tube portions of the first and second pluralities of layers are stacked one above the other with the axes thereof all essentially parallel and with the central tube portions of each first plurality layer in heat exchange relationship with the central tube portions of a second plurality layer. The header connector tube portions at each end of the central tube portions of each layer are arranged so that the header connector tube portions of the first layers diverge from the header connector tube portions of the second layers to provide four sets of separated header connector tube portion ends. Each set of header connector tube portion ends for one of the first and second pluralities of layers extend from the stacked array of tubes as a plurality of tube layers spaced apart by the central tube portions of the other of the first and second plurality of layers. The spaces between the layers and around the tubes adjacent the ends thereof of each set of header connector tube portions are filled with a header connecting material that is thermally crystallizable to a low expansion glass-ceramic which has substantially the same coefficient of lineal thermal expansion as the tubes to seal each set against fluid flow between the tubes. The outer surfaces of the assembly of tube layers and header connecting materials are constrained to prevent outward movement of the assembly. The constrained assembly is heat treated to soften the elongated tubes and enable the fluid medium therein to expand and urge the tubes into contact with adjacent tubes and with the header connecting material to fuse the assembly into an integral mass, and to effect crystallization of the tubes and the header connecting material into a low expansion glass-ceramic.