A counter-flow recuperator formed from annular arrays of recuperator core
segments. The recuperator core segments are formed from two opposing
sheets of fin fold material coined to form a primary surface zone
disposed between two flattened manifold zones. Each primary surface zone
has undulating corrugations including a uniform, full height central
portion and a transition zone disposed between the central portion and
one of the manifold zones. Corrugations of the transition zone rise from
zero adjacent to the manifold zone and increase along a transition length
to full crest height at the central portion. The transition lengths
increase in a direction away from an inner edge containing the air inlet
so as to equalize air flow to the distal regions of the primary surface
zone.