| 摘要 |
PURPOSE:To simplify and miniaturize a boiler body and heat water that is flowing through the heat exchanger coil efficiently by providing a pair of upper and lower headers in the upper section of the boiler body, and providing a heat exchange coil which forms an upper bundle of a plurality of thin tubes and a lower bundle of a plurality of then tubes between those headers, and connecting respectively piping for additional burning to the pair of headers. CONSTITUTION:A pair of upper and lower headers 39 and 40 are provided in the upper section of a water chamber 23, and between the headers 39 and 40 a heat exchange coil 29 is connected. The heat exchange coil 29 has two thin tubes 29A and 29B which have row fins bundled in the up-and-down direction and the coil 29 is wound lie a coil to form two parallel flow channels between the headers 39 and 40. With this arrangement it is possible to make the heat exchange area of the heat exchange coil 29 large without making the upper section of the water chamber 23 wider than the lower section of the chamber. Furthermore, there is no need to provide an outer cylinder by connecting two members with different diameters, making the structure of the boiler body 17 simple with only a few number of welding spots, and the material cost is thereby reduced and also it is possible to manufacture the boiler body 17 at a low cost.
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