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 spiral heat exchanger is disclosed for indirect heat transfer between fluid media, primarily in heat recovery applications characterized by undissolved materials suspended in one or both fluid media. The heat exchanger has a transition chamber between the inlet for a fouling fluid (one which carries undissolved materials) and a heat exchanging passage for the fouling fluid. The transition chamber is has an enlarged cross section compared to the fouling fluid passage to collect undissolved material that may otherwise flow into the fouling fluid passage. This arrangement allows undissolved material to collect without completely blocking the fouling fluid passage. Easy access is provided to the transition chamber to remove collected undissolved material. A heat-conducting strip spirally wound within a shell or casing with opposite edges of the strip sealed to the casing defines two adjacent, spirally extending fluid passages.