TWI757942B

In the present invention, a plurality of columns of heat exchange bundles 41 are formed by heat transfer tube groups in which a plurality of linear tube parts 45 of heat transfer tubes 12 are arranged side by side in block shapes separated from each other. The heat exchange bundles are disposed in a serial arrangement in a plurality of columns, from the upstream side of exhaust gas to the downstream side. In each of the plurality of columns of the heat exchange bundles 41, the plurality of linear tube parts 45 are disposed so as to intersect the exhaust gas flow direction. The plurality of heat exchange bundles 41 include a tube pattern hybrid bundle 41A in which a first array tube group 51, in which the tube pattern of the plurality of linear tube parts 45 in a tube orthogonal cross-section that is substantially orthogonal to the linear tube parts 45 is a first array, and a second array tube group 52, in which the tube pattern of the plurality of linear tube parts 45 provided on the downstream side of the fi