Patent ID: 6913073
Filing Date: 2005-07-05
Classification: B21C,F28F,Y10T

Abstract:
1. A metallic heat transfer tube, comprising: integral completely formed fins formed on an outside of a tube wall, a primary groove being defined between mutually adjacent completely formed fins, a root of the completely formed fins projecting generally radially outwardly from the tube wall at a base of the primary groove, each of the completely formed fins having a T-shaped cross section so that the primary groove will be radially closed off by mutually adjacent fins, but for radially open pores opening into the primary groove; a re-entrant groove having opposing sidewalls and a bottom wall formed between the roots of the mutually adjacent completely formed fins and in the base of the primary groove, the re-entrant groove extending coextensively with the primary groove, the re-entrant groove being formed by a pair of projections extending continuously with the primary groove and projecting toward one another from a respective root of the mutually adjacent fins and terminating a first measured distance from one another so as to define a gap therebetween and so that a second measured distance at a widest spacing between the sidewalls of the re-entrant groove measured along a theoretical line spaced from and parallel to a further theoretical line containing the first measured distance is greater than the first measured distance, a relationship between the first and second measured distances being continuously maintained throughout the length of the primary groove; wherein the fins and the primary grooves extend helically; and wherein the cross section of the re-entrant secondary grooves is varied at regular intervals.