Abstract: First heat transfer plates S1 and second heat transfer plates S2 folded along crest folding lines L1 and valley folding lines L2 are bonded to an inner periphery of an outer casing 6 and an outer periphery of an inner casing 7, so that the first and second heat transfer plates S1 and S2 are disposed radiately, thereby forming combustion gas passages and air passages circumferentially alternately. One end of both the combustion gas passages and the air passages is cut into an angle shape, and one side and the other side of the angle shape are closed to form combustion gas passage inlets 11 and air passage outlets 16. In a similar manner, combustion gas passage outlets 12 and air passage inlets 15 are formed at the other end of the combustion gas passages and the air passages. Thus, it is possible to provide a heat exchanger which has a simple structure and is easy to manufacture, and in which the pressure loss due to bending of flow paths can be suppressed to the minimum.

Abstract: In the case where a partition for partitioning a combustion gas passage inlet 11 from an air passage outlet 16 is defined by a plate 8 attached by brazing to end surfaces of a plurality of heat-transfer plates S1, S2 in a heat exchanger 2, durability of the brazed portions are prevented from being degraded due to a load F acting on the plate 8 by a pressure differential between a combustion gas and air. Thus a bonding base plate 26 is attached by brazing to the end surfaces of the heat-transfer plates S1, S2 with the front surface of the bonding base plate 26 brazed to the rear surface of a bonding flange 28, which is formed by bending an end of the plate 8 by right angles, and a bonding flange 27 having an L-shaped cross section is attached by brazing to an underside of the plate 8 and the front surface of the bonding base plate 26. Accordingly, the bonded portions are increased in rigidity to ease stress concentration, thus enhancing durability.

Abstract: A heat exchanger is formed from a metal strip wound concertina fashion to provide superimposed plates. The plates are stamped in pairs separated by a narrow section which forms a return bend for folding the two plates over one another. Each plate is provided with ribs shaped to guide gas flow paths through the pocket between an inlet in one corner region of the plate and an outlet in a second corner region of the plate. Corrugated zones are formed in the plate between the ribs to promote a whirling motion of air as it travels between the ribs flanking the corrugated zones.

Abstract: In a heat exchanger for exchanging heat of fluids, the heat exchanger is provided with a heat exchanging section having a shape bent alternately consecutively so as to form laminate space and is constructed such that a first flow passage is formed on a space contacting a first surface of the heat exchanging section among the laminate space; and a second flow passage is formed on a space contacting a second surface of the heat exchanging section among the laminate space, wherein a first fluid flows on the first flow passage and a second fluid flows on the second flow passage.