Ribbed heat exchanger tube

摘要

The tube has multiple, circumferential, integral ribs on it's outer surface. Assuming a thread pitch of up to 4, a single group contains two adjacent rib run starts (A1, A2, A3...), with groups of rib starts, groups of three run starts and groups of four rib starts whose rib crests are upset to form thick rib ends. The rib crests are notched out, split and/or bent to the sides and/or upset in a rib pitch of 0.25-1.50 mm and rib height of 1.60 mm upwards. The inner ribs are in helix form at a preferred lead angle of 5-25 deg. and inner rib pitch of 0.5-3 mm, height 0.2-0.5 mm. The ribs are rolled out of the smooth tube surface by material displacement using a dissimilarly diametered disc rolling tool pressed into the tube wall as supported by mandrel. The tube being ribbed is rotated and/or fed forward to form the ribs so pitched that each tool completes a number of ribs.