FINNED HEATHER EXCHANGER TUBING WITH VARYING WALL THICKNESS

摘要

A heat transfer unit includes an elongate finned tubular element (18) bent in a serpentine pattern with the thickness of the wall of the tubular element (18) made greater at return bend portions (42) than at cross portions (41) either by more shallow cutting of the rib material from which the fins (21-26) are formed at the return bend portions (42) than at the cross portions (41) or by crimping the tubular element (18) at the return bend portions (42) prior to cutting the fins so that portions (31, 31a) of rib material (27-29) from which the fins (21-26) are cut are compressed inwardly on both sides of the tubular element (18) to increase the wall thickness of tube material at the return bend portions (42).