Tube provided with inner fins and outer fins or pins, particularly for heat exchangers, and method therefor

A heat exchanger comprising a finned tube provided with both external and internal fins, constituted by a plurality of sections, the base portion of each section being curved according to a circle arc, said sections being welded together to form the outer surface of the tube, each section being provided with at least one wing extending inwardly radially from the curved base portion to act as inner fin of the tube and with at least a fin extending outwardly radially from the curved base portion to act as external fin of the tube, wherein each section has a Z-shaped cross-section, one end portion of which constituting the inner fin, the other portion forming the outer fin, wherein the inner and the outer fin are each offset with respect to the adjacent fin, the middle portions of each section being joined to one another at the corners of said sections by a weld joint of the lower side wall of each section with the upper side wall of an adjacent section.