| 摘要 |
PROBLEM TO BE SOLVED: To provide a working method for manufacturing inexpensively a heat exchanger having a hot-water supplying pipe and a bath heating pipe, which are connected in a flat plane. SOLUTION: A plurality of plate fins 6 are arrayed and a brazing material is arranged, then, are received into a combustion drum 9 and, thereafter, a first fin pipe 7 and a second fin pipe 8, which are produced by bending straight material tubes having a substantially circular sectional configuration so as to have a U-shape, are inserted into the plate fins 6. Subsequently, mandrels having a predetermined configuration are fitted forcibly into the opening ends of the first fin pipe 7 and the second fin pipe 8, then, the connecting surface between the fins are worked so as to have a flat configuration while expanding the pipes. Subsequently, the opening ends are connected by a communicating tube 11 having a different configuration from that of pipe expanding and, thereafter, these parts are heated to a predetermined temperature in a brazing process to braze them by passing them through a high-temperature furnace heated to a predetermined temperature.
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