Abstract: A heat exchanger for use in high pressure environments, such as in a gas turbine engine, includes an outer casing, a tubular element within the outer casing and an inner sleeve within the tubular element. The tubular element has an outer surface and an inner surface. The outer casing and outer surface of the tubular element define a first annular passage through which a first fluid flow path extends. The inner sleeve and inner surface of the tubular element define a second annular passage through which a second fluid flow path extends. The first annular passage is sealed against the outer surface of the tubular element and the second annular passage is sealed within the inner surface of the tubular element.

Abstract: Heat exchanger includes tubular element within outer casing and inner sleeve within tubular element. Outer casing and outer surface of tubular element define a first annular passage through which first fluid flow path extends. Inner sleeve and inner surface of tubular element define second annular passage through which second fluid flow path extends. First annular passage is sealed against outer surface of tubular element and second annular passage is sealed within inner surface of tubular element. Second heat exchanger having tubular element within outer casing. Tubular element has outer fins and inner fins. Outer casing and outer surface of tubular element define a first annular passage through which first fluid flow path extends. Inner surface of tubular element defines a second passage through which second fluid flow path extends. Outer fins are integral with outer surface of tubular element and inner fins are integral with inner surface of tubular element.

Abstract: A duct comprising an inner casing spaced apart from an outer casing and which also comprises a number of interfaced duct sections must be assembled in such a way to prevent relative redial movement between the casings and thereby inhibit buckling. The present invention is a duct which utilises abutment members which longitudinally extend from each of the inner walls across the interface of the duct sections. The abutment members are radially spaced apart in normal use but are configured such that substantially relative radial movement of the inner and outer walls is prevented when the overlapping members abut.