Method of manufacture of a primary heat exchanger jacketed by a secondary heat exchanger

A method of manufacturing a composite heat exchanger including a primary heat exchanger surrounded by a hydraulically discrete, secondary heat exchanger, said secondary heat exchanger having a core of predetermined width as defined by parallel header plates, comprising the steps of;

• forming a plurality of composite, U shaped tubes, each having a pair of, regularly spaced parallel arms longer than the predetermined width of said core, each air of parallel arms having an inner tube joined to the other inner tube of the pair by an integral U shaped junction and an open, inner end aligned in a pair with an open, inner end of the other inner tube of the pair, each inner tube also being surrounded by an open, outer tube each outer tube having a length substantially equal to the predetermined width of said core, a thickness greater than said inner tubes, and having a series of internal webs that slide fit closely over the outside of said inner tubes, thereby forming a jacket space surrounding each inner tube,
• providing a pair of header plates with a series of tube slots having a spacing equal to said regular spacing of said inner tubes and a thickness equal to the thickness of said outer tubes,
• installing each of said header plates over the outer tubes on each of said composite tubes to a separation substantially equal to the predetermined width of said core, thereby fixturing said composite tubes into a regularly spaced pattern,
• attaching a separate U shaped junction to interconnect each adjacent pair of inner tube open ends, diagonally opposed to the integral U shaped junctions, except the first and last inner tube open ends, thereby joining said inner tubes into a single, serpentine flow pattern comprising said primary heat exchanger with open first and last tube ends,
• joining a manifold tank to each of said header plates, thereby interconnecting said jacket spaces into a single, parallel flow pattern comprising said secondary heat exchanger discrete from said primary heat exchanger,
• fixing a primary inlet and outlet through said manifold tanks and into said first and last inner tube open ends, and,
• providing a secondary inlet and outlet into said manifold tanks,
• whereby, a primary heat exchange medium fed through said primary inlet and outlet flows in a serpentine pattern through said primary heat exchanger only, completely surrounded by, but hydraulically discrete form, said secondary heat exchange medium in said secondary heat exchanger.