Abstract: A tube having a plurality of hydraulically parallel fluid passages for use in a heat exchanger can be made by forming an elongated, undulating insert and disposing the same within a flattened tube. A noncorrosive brazing flux is adhered to at least one of the interior of the tube and the crests on the undulating insert. Braze alloy is also located at the interface of the crests of the insert and the interior wall of the tube. Thereafter, the insert is located within the tube without disturbing the flux and the tube deformed along its length to bring the interior of the tube into contact with the crests on the insert. The assembled tube and insert construction is then heated to braze joints between the interior wall of the tube and the crests of the insert along the entire length of the latter.

Abstract: A tank-header connection including a groove extending about the periphery of a header plate and having a bottom wall surrounded by an upstanding wall with spaced apertures therein. A compressible gasket is located in the groove and a plastic tank having an opening surrounded by a rim is provided. The rim has a series of outwardly projecting lugs and is otherwise sized and configured to fit within the groove with the lugs extending through and being captured in aligned ones of the apertures.

Abstract: Improved resistance to pressure caused deformation in header and tank construction utilized in heat exchangers is achieved by providing domes, preferably exteriorally convex, in the header surfaces of the header and tank construction. These domes are located in the area between the holes in such constructions through which tubes extend.