High performance heat transfer tube and method of making same

Claim 1

In a heat transfer tube for transferring heat of condensation of a refrigerant fluid outside the tube to a circulating coolant liquid inside the tube and which is enhanced with a plurality of helically extending interior ribs on the interior surface of the tube for inducing turbulence in the circulating coolant liquid and at least one helically extending exterior fin about the exterior of the tube extending radially outward from a base portion disposed toward the tube axis to a tip portion radially remote from said axis, the fin defining at least one open channel in which the condensed refrigerant fluid can collect; the improvement wherein said external fin has a substantially uniform profile over the circumference of the tube, and said interior ribs are disposed at sufficiently small pitch that the exterior fin is formed without a Moire reduction in height at the positions where the exterior fin crosses the interior ribs and the distance from the base to tip of said fin is substantially uniform.