Abstract: A metallurgical joint between a copper tube and an aluminum tube is disclosed. The metallurgical joint between the tubes is elongated and extends along the length of the telescoping tubes and is substantially free of materials other than copper and aluminum. A method and apparatus for making the metallurgical joint is disclosed.

Abstract: A method and apparatus for forming a heat exchanger assembly including wrapping a one-piece heat exchanger tube onto a heat transfer unit having a plurality of fins on upper and lower surfaces, the fins being provided with notches which are aligned in sets with each set of notches receiving a section of the heat exchanger tube as it is wrapped around the heat transfer array, return bend portions of the heat exchanger tube being formed in the wrapping process to have a generally rectangular cross section to maximize the cross sectional area of the heat exchanger tube in the return bend areas of the tube. Apparatus for forming the heat exchanger assembly includes a mandrel for rotating the fin unit, drawing the heat exchanger tube around the fin unit, and forming devices mounted on the mandrel to define the pitch of the return bends and to maintain the cross section of the heat exchanger tube in the return bend portions generally rectangular in shape when the heat exchanger tube subsequently is expanded.

Abstract: A method for separating a thin-walled multiport extrusion into a plurality of micro-tubes for use as single pass lengths in a heat exchanger assembly, the method including the steps of threading the micro-extrusion into a clamping device including first and second sets of clamping blocks which hold the micro-extrusion rigidly while the clamping blocks of the clamping device are drawn in opposite directions on opposite sides of a groove cut in the upper and lower walls of the extrusion, tearing the extrusion apart along cutting lines formed in the upper and lower walls of the extrusion during the separation process.

Abstract: A method for forming a heat exchanger assembly including wrapping a one-piece heat exchanger tube onto a heat transfer unit having a plurality of fins on upper and lower surfaces, the fins being provided with notches which are aligned in sets with each set of notches receiving a section of the heat exchanger tube as it is wrapped around the heat transfer array, return bend portions of the heat exchanger tube being formed in the wrapping process to have a generally rectangular cross section to maximize the cross sectional area of the heat exchanger tube in the return bend areas of the tube.

Abstract: A heat exchanger assembly of the side-entry cross-fin type includes first and second integral fin units, each comprising a single sheet of material provided with a plurality of aligned apertures, the sheet of material being folded in accordian-fashion such that the apertures define a plurality of notches arranged in rows which extend longitudinally of the fin unit. Two of the fin units are assembled together with a single length of heat exchange tube which threads the notches of the fin units, the tube extending over an oval-shaped helical path through the two fin units. In another embodiment, a single folded fin unit is provided with notches in fins on its upper and lower surface, a single length of tube being wrapped around the single fin unit threading the apertures therein, the tube extending in a generally oval-shaped helix path.

Abstract: A heat transfer unit includes an elongated finned tubular element bent in a serpentine pattern with the thickness of the wall of the tubular member made greater at return bend portions than at cross portions either by more shallow cutting of the rib material from which the fins are formed at the return bend portions than at the cross portions, or by crimping the tubular member at the return bend portions prior to cutting the fins so that a portion of the rib material from which the fins are cut is compressed inwardly on both sides of the tubular member to increase the wall thickness of tube material at the return bend portions.

Abstract: A heat exchanger assembly of the side-entry cross-fin type includes first and second integral fin units, each comprising a single sheet of material provided with a plurality of aligned apertures, the sheet of material being folded in accordian-fashion such that the apertures define a plurality of notches arranged in rows which extend longitudinally of the fin unit. Two of the fin units are assembled together with a single length of heat exchange tube which threads the notches of the fin units, the tube extending over an oval-shaped helical path through the two fin units. In another embodiment, a single folded fin unit is provided with notches in fins on its upper and lower surface, a single length of tube being wrapped around the single fin unit threading the apertures therein, the tube extending in a generally oval-shaped helix path.

Abstract: A heat exchanger having groups integral fins projecting outwardly from the sidewalls of the heat exchanger is manufactured by advancing a cutter into the sidewalls of the heat exchanger, turning the integral fins outwardly and severing predetermined fins with the cutting instrument to provide predetermined fin-free areas on the sidewalls.

Abstract: A heat exchanger embodying an elongated tubular member with integral fins projecting therefrom, with predetermined areas of the tubular member being rendered fin-free during formation of the heat exchanger.