Abstract: A heat exchanger for use in applications with high temperatures and rapidly changing thermal gradients. The heat exchanger has a shell, a head, a tubesheet, a tubesheet skirt, and a tube bundle. The tubesheet has a peripheral diameter smaller than the inner diameter of the interior of the head and is coupled to the head by the tubesheet skirt. The gap between the tubesheet and the head is sufficient to allow the removal of the tubesheet from the head after the tubesheet suffers typical thermal deformation. In a preferred embodiment, the head defines a chamber having a combined spherical-cylindrical geometry.

Abstract: The invention discloses a novel head closure apparatus for shell and tube-type heat exchangers. The disclosed apparatus is substantially resistant to thermal stress cracking in that it has an internal closure chamber configured to withstand and dissipate thermal stresses caused by rapidly changing thermal gradients. The apparatus also provides for full access to the entire interior volume of the head closure and to the entire area of the head closure inner tubesheet surface in order to facilitate maintenance and repairs. The invention also discloses a compact and efficient retaining key apparatus for constraining the end-cover of a cylindrically-shaped head closure member against internal working pressures. The apparatus enables substantial reductions in the masses of the retaining keys, the head closure member, and the end-cover, which results in the head closure apparatus being simpler and more economical to manufacture and maintain.