Abstract: A heat transfer tube (10) for use in an application, such as a shell and tube type air conditioning system condenser, in which a fluid flowing through the heat exchanger external to the tubes condenses by transfer of heat to a cooling fluid flowing through the tubes. The tube has at least one fin convolution (20) extending helically around its external surface (13). A pattern of notches (30) extends at an oblique angle (&agr;) across the fin convolutions at intervals about the circumference of the tube. There is a spike (22) between each pair of adjacent notches. The fin convolution, notches and spikes are formed in the tube by rolling the wall of the tube between a mandrel and, first, a gang of finning disks (63) and, second, a notching wheel (66). Because, during the manufacture of the tube, of the interaction of the rotating and advancing tube and the notching wheel, the angle (&bgr;) of inclination of the axis of the tip of the spike is oblique with respect to the notch angle.

Abstract: A tube for use in a heat exchanger where heat is transferred between a fluid flowing through the tube and a fluid flowing around the exterior of the tube and where the fluid external to the tube boils during the heat exchange process. The tube has one or more external fin convolutions extending from its external surface. At intervals along each side surface of the fin convolutions there are shoulder notches extending from the fin side surfaces. The groove space between adjacent fin convolutions has raised teeth located circumferentially at intervals. The fin convolutions do not extend perpendicularly from the tube surface but are inclined, with one convolution overlying an adjacent groove but not touching its adjacent neighbor fin convolution to form a re-entrant boiling cavity with an opening gap. In one embodiment, the opening gap extends completely around the circumference of the tube.

Abstract: A heat exchanger tube (10) for use in an application, such as a shell and tube type air conditioning system condenser, in which a fluid flowing through the heat exchanger external to the tubes condenses by transfer of heat to a cooling fluid flowing through the tubes. The tube has at least one fin convolution (22) extending helically around its external surface (13). Multiple axial notches (23) are impressed into the fin at intervals along its extent. Because the notches are impressed and not cut into the fin, material displaced from a fin to form a notch forms lateral projections (24) from the the walls of the fin. The notched fins provide increased external heat transfer surface area on the tube, destabilize the film of condensate on the tube external surface, thus causing the film to be generally thinner, and promote condensate drainage from the fins and off the tube and thus increase the heat transfer performance of the tube.