A heat exchanger comprising: a shell including: a shell body having a hollow an inner chamber defined by a wall structure, the inner chamber having opposed ends; a pair of shell end members (36, 38) attached to adjacent respective shell body ends; and an expansion element positioned around an outside surface of the shell, the expansion element having a first end attached to a portion of the shell body adjacent to one of its ends, and having a second end attached to an end of one of the shell end members (36, 38), wherein the end of the shell end member body attached to the expansion element is disposed completely around the shell body, and wherein the expansion element accommodates axial movement between one of the shell end members (36, 38) and the shell body, and the expansion element includes a collar configured to overlap a portion of one of the shell end members (36, 38), wherein the expansion element includes multiple outwardly projecting members connected to each other by a web section; a tube stack disposed within the inner chamber and comprising a plurality of tubes, the tubes having opposed ends positioned adjacent the shell body opposed ends; and a pair of tube header plates each comprising a number of openings attached to adjacent respective tube ends, and including an outer edge that is attached to one of the shell end members (36, 38) to form a leak-tight seal between the tubes and the shell inner chamber. a shell including: a shell body having a hollow an inner chamber defined by a wall structure, the inner chamber having opposed ends; a pair of shell end members (36, 38) attached to adjacent respective shell body ends; and an expansion element positioned around an outside surface of the shell, the expansion element having a first end attached to a portion of the shell body adjacent to one of its ends, and having a second end attached to an end of one of the shell end members (36, 38), wherein the end of the shell end member body attached to the expansion element is disposed completely around the shell body, and wherein the expansion element accommodates axial movement between one of the shell end members (36, 38) and the shell body, and the expansion element includes a collar configured to overlap a portion of one of the shell end members (36, 38), wherein the expansion element includes multiple outwardly projecting members connected to each other by a web section; a tube stack disposed within the inner chamber and comprising a plurality of tubes, the tubes having opposed ends positioned adjacent the shell body opposed ends; and a pair of tube header plates each comprising a number of openings attached to adjacent respective tube ends, and including an outer edge that is attached to one of the shell end members (36, 38) to form a leak-tight seal between the tubes and the shell inner chamber. a shell body having a hollow an inner chamber defined by a wall structure, the inner chamber having opposed ends; a pair of shell end members (36, 38) attached to adjacent respective shell body ends; and an expansion element positioned around an outside surface of the shell, the expansion element having a first end attached to a portion of the shell body adjacent to one of its ends, and having a second end attached to an end of one of the shell end members (36, 38), wherein the end of the shell end member body attached to the expansion element is disposed completely around the shell body, and wherein the expansion element accommodates axial movement between one of the shell end members (36, 38) and the shell body, and the expansion element includes a collar configured to overlap a portion of one of the shell end members (36, 38), wherein the expansion element includes multiple outwardly projecting members connected to each other by a web section; a tube stack disposed within the inner chamber and comprising a plurality of tubes, the tubes having opposed ends positioned adjacent the shell body opposed ends; and a pair of tube header plates each comprising a number of openings attached to adjacent respective tube ends, and including an outer edge that is attached to one of the shell end members (36, 38) to form a leak-tight seal between the tubes and the shell inner chamber.