Heat exchanger, especially for cooling a high temperature air stream

A heat exchanger comprising two fluid headers and a bundle of tubes fitted between the headers, each of the tubes having a cross section transverse to the respective tube lengths thereof, wherein each header comprises a stack of shell members arranged in pairs, the stack having a predetermined height, each shell member having an endless side wall, a flat outer flange joined to one edge of the side wall, and a flat inner flange joined to the other edge of the side wall, the inner flange being parallel to the flat outer flange and defining an axial through aperture, the side wall of the shell member defining a lateral aperture having a cross section corresponding to one half of the transverse cross section of the tube, indexing means for positioning the shell members on the flat outer flange of each shell member, said inner flange having an offset region defining said lateral aperture of the shell member, said offset region lying intermediately between the plane of the outer flange and the plane of the inner flange, the sidewall of each shell member including a substantially straight region joined to said offset region of the inner flange, whereby the shell members are assembled in pairs of alternate shell members, through their inner and outer flanges, so as to define together an internal chamber extending over the whole height of stack, the tubes having end portions each of which is received in the two said lateral apertures of two adjacent shell members, the indexing means positioning the shell members of a pair with respect to each other through their respective outer flanges.