Abstract: The heat exchanger includes a tube having axially spaced fins or a continuously spirally wound fin about the tube. One or more of the fins are dimpled, mechanically or molded, to provide concavities and projections on opposite sides of the fins or alternating concavities and projections on opposite side of the fins. The dimples improve the heat transfer between the fluid flowing through the tubes and the air circulating about the tubes and through the fins. The dimples create vortices and turbulent flow between the fins and effectively increase the heat transfer rate.

Abstract: A method of enhancing the heat transfer coefficient of a tube flowing a fluid in the tube in heat exchange relation with a second fluid external to the tube includes applying metal particles to an interior surface of the tube to thereby create an increased wetted area for interaction with fluid flowing through the tube; wherein the particles are applied by: providing an applicator head including an electric arc and at least one metal wire; displacing the head along the interior of the tube; feeding the wire into the electric arc as the head is displaced along the interior of the tube; melting the wire to form molten metal particles; and applying the molten metal particles about and along the length of the interior wall surface of the tube as the head is displaced along the interior of the tube.

Abstract: The heat exchanger includes a tube having axially spaced fins or a continuously spirally wound fin about the tube. One or more of the fins are dimpled, mechanically or molded, to provide concavities and projections on opposite sides of the fins or alternating concavities and projections on opposite side of the fins. The dimples improve the heat transfer between the fluid flowing through the tubes and the air circulating about the tubes and through the fins. The dimples create vortices and turbulent flow between the fins and effectively increase the heat transfer rate.

Abstract: A surface of an article, for example an external fluid flow surface, includes a plurality of metal wires lengthwise of the wires along the article surface. The article can be in the form of a component of an apparatus, for example a component of a gas turbine engine, the wires being bonded along and modifying surface characteristics of the article. Also, the article can be in the form of a bonding layer, for example a brazing tape, including the metal wires carried along a surface of the layer.