| 摘要 |
PROBLEM TO BE SOLVED: To provide an opening portion in a ceiling part of a boiler, have a small number of bent pipe parts, and smoothly flow steam without having a fear of a blocked phenomenon (drain plugging) by condensed water. SOLUTION: A pair of first heat transfer tubes 12 pinching an opening portion 3 therebetween and a pair of second heat transfer tubes 14 located in outer sides of the pipes 12 are provided. The first heat transfer tubes 12 and the second heat transfer tubes 14 are coupled with each other by means of parts 12a, 14a surrounding the opening portion 3, and a common part 13 thereof is constituted so that both fluids flow. The second heat transfer tube 14 has a bypass pipe 16 nearly horizontally bypassing outside the common part 13 so that fluid can be flowed both common part 13 and bypass pipe 16. Although an upper/lower bent part are formed in the coupled part of the second heat transfer tubes 14 and bypass pipe 16, since the second heat transfer tubes themselves are formed only by a horizontal pipe as similar to the conventional, even if condensed water is formed in a part, it flows as it is without stagnation in the upper/lower bent part, and a normal flow can be maintained.
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