| 摘要 |
PROBLEM TO BE SOLVED: To eliminate such problems in a combustion device provided with a flow passage having a plurality of functions at one boiler that fluid stayed in the flow passage with a function not used at each of the single operations is boiled, scale is accumulated in the flow passage, its durability performance is deteriorated or output at each of the single operations must be reduced. SOLUTION: Joint flow passages 7 having a first flow passage 10 and a second flow passage 5 passing through some heat transfer fins 4 alternatively jointed to each other are arranged at upper and lower two stages. The joint flow passages 7 of these upper and lower two stages are jointed to each other to cause four flow passages to be cooperatively connected, thereby even if a heating operation for independently heating each of the flow passages is carried out, a temperature of water left in the other pipe not being operated is restricted from being increased, prevention of occurrence of the scale in the pipe and an extension of life of the heat exchanger 8 can be realized. That is, performance of the device can be sufficiently realized, durability performance of the combustion device can be improved, a reliability of product can be substantially improved and an extension of lifetime of the device can be realized.
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