A method for making a tube is described in which a multi-layer billet is extruded to provide a tube having a wall comprising an inner layer metallurgically bonded to an outer layer.

A process of producing shell and tube heat exchangers where the ends of the tubes are secured to a tube sheet while reacting applied FSW forces without introducing a crevice or local deformation near the ends of the tubes. In particular, an interference fit is used to lock the ends of the tubes into the tube sheet without flaring or expanding the tube ends. A FSW process is then used to weld the ends of the tubes to the tube sheet.

A heat exchanger comprising helically wound tube bundles is disclosed. The helically wound tube bundles are joined with tube sheets to define a primary working fluid system that is fluidically isolated from a secondary working fluid system. The tube sheets and tubes are formed of the same material, which facilitates their joining by means of joints that are substantially galvanic corrosion-resistant joints.

A joined body includes: a main body section including a wall section forming a passage along which a medium for accelerating heat exchange flows; and a cover configured to cover a surface of the main body section, the cover including: a covering section provided on a side facing the main body section and configured to cover the surface; a groove section provided on the side facing the main body section and configured to accommodate an end portion of the wall section; and a stirred joint section provided on a side opposite to a side where the covering section and the groove section are provided, the stirred joint section being at least partly frictionally stirred by a depth reaching a bottom of the groove section from a surface on a side opposite to the side facing the main body section and bonded to the end portion of the wall section.

A heat sink assembly includes a heat sink having a plurality of ribs integrally molded along a length direction of the heat sink by extrusion molding, the heat sink having spaces between the plurality of ribs forming a flow path, and the heat sink having first and second surfaces that are open at ends of the length direction of the heat sink; and a pair of end plugs respectively closing the first and second surfaces at the opposite ends of the heat sink, wherein the plurality of rib includes a center rib having one end of the first surface being closed and another end of the second surface being open with respect to the pair of end plugs, and a side rib disposed on at least one side of the center rib in a width direction of the center rib, and the side rib being open at opposite ends of the first and second surface sides.