High-temperature heat exchanger

A heat exchanger comprising:

• a metal monolith having two ends and a plurality of channels through which fluid flows, said plurality of channels including two outermost channels;
• a shell surrounding said monolith, wherein said shell is open on both ends to provide fluid flow to said channels, said shell further comprising two fluid openings adjacent said ends of said monolith;
• at least one comb comprising a spine and a plurality of teeth, wherein the comb is attached to one end of said monolith and said teeth are aligned with a portion of said channels to provide a fluid flow stop at one end of said monolith;
• at least one duct collar attached to one end of said monolith, wherein said comb is positioned between said duct collar and said monolith end;
• at least one u-shaped metal piece attached to at least one said shell fluid opening adjacent said end of said monolith, wherein said u-shaped metal piece and said spine form a duct opening to provide fluid flow to said channels;
• and
• said two outermost channels having cut pieces configured such that the fluid flow through said two outermost channels is substantially blocked and said cut pieces provide enhanced support to said shell of said heat exchanger.