GB1390781A - Heat-exchange tubing - Google Patents

Abstract

1390781 Heat-exchange tube NORANDA METAL INDUSTRIES Inc 2 March 1972 9683/72 Heading B3A A method of forming longitudinal heatexchange tubing 10 comprises providing a round metal tube blank 24, Fig. 4, having a peripheral wall 12 with inner fins 14, and reducing the interior space of the blank by partially flattening the blank to produce an oblong cross-section with two opposite parallel wall sections spaced apart to allow the fins on one wall section to extend with their tips 16, Fig. 2, at least level with the fin tips on the opposite wall section. The blank may be formed by brazing or otherwise joining inserted fins to the inner wall of the blank or displacing metal from the blank wall by swaging on a mandrel to form integral fins which may extend parallel or helically to the tube axis. The blank is then partially flattened to form the tubing 10 by passing through rotary rolls (30) (32), Fig. 12 (not shown), or by drawing the blank through a die (36), Fig. 13 (not shown). The number of fins provided and their height, as well as the peripheral extent of the wall, may vary within a range and tubes may be formed with overlapping fins, Figs. 6, 9, 21 (not shown), and fins which touch the opposite wall section, Fig. 11 (not shown). The tubing may be provided with both outer (108) and inner fins, Figs. 21, 22 (not shown), which may extent longitudinally or helically to the tube axis using suitable forming rolls. Moreover, a brazing strip (112), Fig. 23 (not shown), may be interposed between the fins (14e) and the blank flattened and then furnace heated to melt the strip and bond the fins at their intersections. This provides a tube strengthened to resist opening under internal fluid pressure. Also, the tubes may be strengthened by bending. This is done by curving or twisting the tubes either longitudinally, Fig. 18 (not shown), transversely, Fig. 19 (not shown), or both longitudinally and transversely, Fig. 20 (not shown).