Steam generator with vertical tubesheets

A heat exchanger for transferring heat from a primary fluid to a secondary fluid, said heat exchanger comprising:

• a vertically oriented cylindrical sheel portion, said shell portion having an upper thickened cylindrical portion and a lower thickened cylindrical portion, said thickened portion having a plurality of holes so disposed to form upper and lower tubesheets integral with the shell and extending around the upper and lower portions thereof;
• an upper head forming one end closure for said shell;
• a lower head forming another end closure for said shell;
• and
• a plurality of C-shaped tubes, the end of which are received by said holes to form the heat transfer surface of said heat exchanger, said tubes being disposed in wedge shaped bundles with a space between adjacent bundles and being disposed to provide a central opening free of tubes extending throughout said bundles, thereby forming a heat exchanger with vertically oriented tubesheets to eliminate the buildup of crud adjacent the lower tubesheet.