Abstract: A method for joining a tube and tube plate for use in a tube-and-shell heat exchanger is disclosed. The method enables a joint between the tube and tube plate that is substantially hermetic and substantially corrosion-resistant. The method comprises providing an anvil inside the tube, wherein the anvil supports the tube wall during a friction-stir welding process used to join the tube and tube plate. The anvil facilitates formation of a reliable weld region and enables faster friction-stir welding.

Abstract: A heat exchanger for exchanging heat between a first fluid and a second fluid is disclosed; wherein the heat exchanger has improved thermal efficiency and low fluid back pressure. The heat exchanger comprises conduits for conveying the first fluid, wherein the conduits include a plurality of flow passages. The flow passages are defined by a plurality of fins that are continuous along the direction of flow of the first fluid. Each fin includes a wave-shaped region, and adjacent fins sub-divide each flow passage into first and second sections that are interposed by a third section. The wave-shape of the fins creates a continuously varying cross-sectional area for each third section. The variation of the cross-sectional area of the third section, coupled with the wave-shape of the fins, induces a swirl flow between the third section and each of the first and second sections. This swirl flow improves the efficiency of the overall convection heat transfer in each conduit.

Abstract: A method for joining a tube and tube plate for use in a tube-and-shell heat exchanger is disclosed. The method enables a joint between the tube and tube plate that is substantially hermetic and substantially corrosion-resistant. The method comprises providing an anvil inside the tube, wherein the anvil supports the tube wall during a friction-stir welding process used to join the tube and tube plate. The anvil facilitates formation of a reliable weld region and enables faster friction-stir welding.