Abstract: A heat exchanger includes a core adapted to heat air with counter-flowing hot gases. Substantially isothermal hot and cool portions of the core are interconnected by a matrix portion exposed to a temperature gradient. A top sheet is positioned over the core and includes first and second ends and a middle portion between the first and second ends. The middle portion includes a window and compliant ligament portions extending alongside the window and interconnecting the first and second ends. The first and second ends of the top sheet are positioned over the isothermal cool and hot portions of the core, respectively, and the middle portion of the top sheet is positioned over the matrix portion of the core. The compliant ligament portions of the top sheet are deflectable in response to the temperature gradient across the matrix portion of the core to reduce strain on and deflection of the first and second ends of the top sheet.

Abstract: A method of making a heat exchanger includes assembling one or more heat exchange cells. Each heat exchange cell is assembled by providing a top plate having an inlet aperture at one end thereof, an outlet aperture at the other end thereof, a first surface, a second surface and peripheral edges; and providing a bottom plate having an inlet aperture at one end thereof, an outlet aperture at the other end thereof, a first surface, a second surface and peripheral edges. The second surfaces of the top and bottom plates are juxtaposed with one another so that the inlet and outlet apertures of the plates are in substantial alignment with one another. The peripheral edges of the top and bottom plates are attached to form a high pressure chamber between the second surfaces of the plates. After being assembled, each individual heat exchange cell is tested before being attached to other heat exchange cells. The testing may include pressure testing of the heat exchange cell.