Method and apparatus for controlled atmosphere brazing of unwelded tubes

A method of manufacturing a heat transfer device, comprising:

• a) providing a plurality of heat transfer folded-type tubes, each having an inner surface which ducts a fluid coolant, the inner surface being uncladded and an outer cladded surface, each having a first and a second end, a seamless bottom surface and a seamed top surface defined by folding a first edge and a second edge of a sheet inwardly toward and into contact with the inner surface;
• b) providing a first header for attachment to said first end of said plurality of heat transfer tubes, said header having a cladded inner surface;
• c) providing a second header for attachment to said second end of said plurality of heat transfer tubes, said header having a cladded inner surface;
• d) providing a plurality of heat transfer fins having between about 0.01 w % and about 0.9 w % magnesium to block the flow of molten clad away from the heat transfer tubes to the plurality of heat transfer fins, and from the headers to the heat transfer tubes, with one of said plurality of heat transfer fins being positioned between two of said plurality of heat transfer tubes;
• and
• e) brazing said plurality of heat transfer tubes, said first header, said second header, and said plurality of heat transfer fins to provide a strong joint with a fillet where said first and second ends of said plurality of heat transfer tubes attach to said first and second headers, respectively, and where the inwardly folded edges meet the seamless bottom surface of each tube, and where the plurality of heat transfer fins meet the heat transfer tubes.