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.

Abstract: A heat transfer surface for nucleate boiling of liquids is formed on the outer surface of a heat exchanger tube. Helical ridges having two fins each encase the tube. A fin at each ridge is angled toward the adjacent fin on the adjacent ridge forming a gapped cavity therebetween. The method of making the tube includes rolling alternating deep grooves and shallow grooves in the outside surface of the tube and then flaring the fins to form the gapped cavity.

Abstract: A heat transfer surface for nucleate boiling of liquids is formed on the outer surface of a heat exchanger tube. Helical ridges having two fins each encase the tube. A fin at each ridge is angled toward the adjacent fin on the adjacent ridge forming a gapped cavity therebetween. The method of making the tube includes rolling alternating deep grooves and shallow grooves in the outside surface of the tube and then flaring the fins to form the gapped cavity.