Abstract: A heat exchanger includes: a first straight section; a second straight section; and a bent section or elbow linking the first straight section and the second straight section. Each straight section comprises a part of an internal cylindrical shell and of an external cylindrical shell, both cooperating to form an intershell space enclosing a bundle of parallel U-bent tubes having each a first and a second straight part respectively located in the first straight section and second straight section of the exchanger and a 180°-bent part located in the bent section or elbow of the exchanger, so that, in use, a first fluid to be heated and vaporized is flowing in the tubes. The external cylindrical shell is provided respectively at one end with an inlet and at another end with an outlet for a second fluid which is a hot thermal fluid.

Abstract: A heat exchanger includes: a first straight section; a second straight section; and a bent section or elbow linking the first straight section and the second straight section. Each straight section comprises a part of an internal cylindrical shell and of an external cylindrical shell, both cooperating to form an intershell space enclosing a bundle of parallel U-bent tubes having each a first and a second straight part respectively located in the first straight section and second straight section of the exchanger and a 180°-bent part located in the bent section or elbow of the exchanger, so that, in use, a first fluid to be heated and vaporized is flowing in the tubes. The external cylindrical shell is provided respectively at one end with an inlet and at another end with an outlet for a second fluid which is a hot thermal fluid.

Abstract: A hairpin heat exchanger (1), wherein the bundle of parallel U-bent tubes (2) is extended out of the exchanger and connected, via bent tubes (11), respectively beyond an end of the internal shell (3) and of the external shell (4) at the first straight section to a first header (9) distributing the first fluid to the bundle of straight tubes (2) and beyond an end of the internal shell (3) and of the external shell (4) at the second straight section to a second header (10) collecting the first fluid under the form of liquid, vapor or a mixture liquid/vapor from the bundle of straight tubes (2).