A HEAT EXCHANGE UNIT

摘要

A heat exchange unit comprising a heat exchange duct for the passage of hot gas therethrough, a heat exchange array located within the heat exchange unit, a bypass duct concentrically arranged with respect to the heat exchange duct to selectively enable at least a portion of the hot gas to bypass the heat exchange duct; a variable position sleeve valve arrangement having a first end and a second end, movable axially such that in a first position the sleeve substantially closes a downstream opening of the bypass duct at the second end and opens an upstream opening at the first end to permit gas to flow past the heat exchange array, the second end being arranged to seal against a plug formation; the plug formation comprising an extension extending upstream towards the first end to define an annular channel between the sleeve and the extension, wherein the upstream end of the extension is torispherical.