Abstract: A device for exchanging heat between the two fluid streams is disclosed. The device includes parallel heat exchange tubes arranged in an annular pattern, the first and second ends of the tubes being coupled to first and second halves of a core housing configured to channel the first gas stream through the heat exchange tubes between a first intake formed on the first half of the core housing and a first exhaust formed on the second half of the core housing. The device further includes a shell enclosing the core housing and separated from the core housing by a space, the shell configured to channel the second gas from a second intake, then between the heat exchange tubes, and then through a second exhaust. The heat exchanger device includes an expansion joint coupling the core housing and the shell housing such that the core housing floats within the shell.