A heat exchanger is formed of a strip of corrugated material that is
folded back and forth upon itself to define a stack. Cut pieces of
corrugated material are inserted within the folds of the strip, such that
the corrugations of the cut pieces are generally perpendicular to the
corrugations of the folded strip. A set of duct attachments holds the
assembly together, and provides paths for fluid flowing into and out of
the exchanger. The ends of the stack, and those parts of the sides that
are not spanned by the duct attachments, are sealed with a
high-temperature sealant. The sealant is preferably a moldable material
that is applied and allowed to harden, and which has a coefficient of
thermal expansion that approximates that of the stack. The heat exchanger
is easy and inexpensive to manufacture, but is suitable for use in
high-temperature applications.