Abstract: A plate-type annular heat exchange cylinder which has increased resistance to cracking under the stress of heat gradients. The invention comprises providing the cylinder in the form of two or more longitudinal segments, such as hemi-cylinders, spaced by axial narrow expansion slots, sealing the spaces between adjacent pairs of the plates of each segment and each expansion slot, uniting the segments by attaching radial coupling plates over the slots at each end of the segments, and blocking the inner peripheral entrance of each axial slot by attaching a narrow gas seal strip thereover.