Patent ID: 6026892
Filing Date: 2000-02-22
Classification: B21C,F28F

Abstract:
A heat transfer tube with a cross-grooved inner surface comprising:a plurality of primary spiral grooves spaced in parallel to each other at a helix angle to a longitudinal axis of the tube;a plurality of secondary grooves spaced in parallel to each other and intersecting the primary spiral grooves at an intersecting angle to a direction of the primary spiral grooves to form a plurality of ridges between adjacent secondary grooves and adjacent primary spiral grooves; andthe helix angle of the primary spiral groove to the longitudinal axis of the tube being in the range of 10.degree. to 40.degree., and the intersecting angle of the secondary groove to the primary spiral groove being in the range of 75.degree. to 105.degree.;the ridge having an upstream slant face at a nearly right angle to the direction of the primary spiral groove and a downstream slant face at an angle in the range of 30.degree. to 60.degree. to the direction of the primary spiral groove;the ratio A/B of a width A of an upper surface of the ridge to a width B of an upper opening portion of the secondary groove being in the range of 0.2 to 1.0.