Abstract: A high temperature heat exchanger having an improved support apparatus for suspending a tube bundle. The improved support comprises a skirt from which the tube sheet and the bundle are supported, and a lip on an upper end of the skirt engaged in a flange assembly receiving the lip. A first refractory lining on an inside face of the skirt extends downwardly from the lip, and overlaps a second refractory lining on an outside surface of the skirt extending upwardly from adjacent the tube sheet toward the lip. By securing the support apparatus in the cold flange assembly, the interior refractory is not used for supporting the tube bundle and can maintain its integrity, have a lower incidence of premature failure and yield an optimum refractory life.