Heat exchanger for a molten salt steam generator in a concentrated solar power plant (iii)

A heat exchanger, comprising:

• a first straight section;
• a second straight section;
• and
• a bent section or elbow linking the first straight section and the second straight section,
• wherein 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,
• wherein 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, so that, in use, the second fluid is flowing according to an annular flow path within the intershell space and cooling down by exchanging heat with the first fluid flowing in the tubes, the intershell space enclosing also baffles to guide the second fluid,
• wherein the bundle of parallel U-bent tubes is connected via a connection to a first end, a first hemispherical bonnet distributing the first fluid to the tubes of the first straight section, and to a second end, a second hemispherical bonnet collecting the first fluid under a form of liquid, vapor, or a mixture of liquid/vapor from the tubes of the second straight section, each connection comprising a tube sheet configured to withstand a difference between the second fluid low pressure inside the intershell space and the first fluid high pressure inside the respective bonnet,
• wherein the tube sheet comprises a circular plate having a central circular orifice, and
• wherein the tube sheet further comprises a hemispherical shell located over the orifice and tightly connected to the circular plate, so as to make a physical separation between the first fluid and the second fluid.