Heat exchanger

Abstract

First heat-transfer plates S,and second heat-transfer plates S,are radially arranged between a larger diameter cylindrical-shaped outer casing,and a smaller diameter cylindrical-shaped inner casing,to form combustion gas passages,and air passages,alternately in a circumferential direction, and a multiplicity of projections,formed on both surfaces of the first heat-transfer plates S,and second heat-transfer plates S,are jointed to one another at tip ends thereof. Pitches P between adjacent projections,are changed in a radial direction to make the number of heat transfer units substantially constant in a radial direction to uniformize temperature distributions on the first heat-transfer plates S,and second heat-transfer plates S,in the radial direction, thereby avoiding a decrease in heat exchanging efficiency and generation of unwanted thermal stress.