| 摘要 |
A double-pipe heat exchanger that is easy to manufacture, and the whole thereof is smoothly bent to serve as part of the piping, and that provides high pressure resistance, wherein an inner tube has a section orthogonal to an axis line thereof in which a plurality of swollen portions in a bladder-like or balloon-like shape in section are formed in a radial direction from the center, mouths of these swollen portions are closed, and the tip ends of respective swollen portions are in contact with the inner surface of an outer tube.
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