Patent ID: 8220152

Claim:
A process for making heat exchanger tubes, characterised in that it comprises the operating steps of: cutting a substantially rectangular piece of sheet which has a first main face ( 11 a ), a second main face ( 11 b ), a front edge ( 12 ), a rear edge ( 13 ) and two lateral edges ( 7 ); subjecting the piece of sheet ( 3 ) to a forming step to obtain a plurality of first elements ( 8 , 9 ) raised relative to the second face ( 11 b ), positioned in such a way that they mirror one another relative to a central axis (X) of the piece of sheet ( 3 ) parallel with the lateral edges ( 7 ), and each having an upper face ( 8 a ) with an extended shape in a main direction of extension; bending the piece of sheet ( 3 ) parallel with the lateral edges ( 7 ), to create a tubular element ( 1 ) whose outer surface consists of the second face ( 11 b ) and which has two flat walls ( 4 ) with the raised elements on them and opposite one another, joined by two connecting walls ( 5 ); the bending step substantially connecting the lateral edges ( 7 ) to one another; and welding the lateral edges ( 7 ) to close the tubular element ( 1 ); wherein during the forming step at least four rows of first raised elements are produced parallel with the central axis (X); the first raised elements ( 8 ) of the rows closest to the central axis (X) being made in such a way that their main direction of extension is set at an angle to the central axis (X) and to a direction perpendicular to it; and the first raised elements ( 8 ) of the rows closest to the lateral edges ( 7 ) being made in such a way that their main direction of extension is set at an angle to the central axis (X) and to a direction perpendicular to it, on the opposite side relative to the first raised elements ( 8 ) of the rows closest to the axis (X), and wherein the forming step involves making one or more higher second raised elements ( 9 ).