| CPC F28D 1/05391 (2013.01) [F25B 13/00 (2013.01); F25B 39/00 (2013.01); F25B 39/028 (2013.01); F28F 1/022 (2013.01); F28F 1/128 (2013.01); F28F 1/40 (2013.01); F28D 2021/0068 (2013.01); F28F 2215/12 (2013.01)] | 6 Claims |

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1. A heat transfer tube comprising:
first flow paths aligned in the heat transfer tube; and
a second flow path disposed in an inner end part of the heat transfer tube along a first direction parallel with an alignment direction of the first flow paths, wherein
each of the first flow paths includes:
a section with a rectangular shape that is elongated in the first direction; and
protrusions disposed on an inner surface,
the second flow path includes:
a section with a rectangular shape or a square shape; and
protrusions disposed on an inner surface,
an end surface in the first direction of the heat transfer tube has a semiarcuate section,
the section of each of the first flow paths has a long side having a first length and a short side having a second length, where a ratio of the first length to the second length is between 1.1 and 1.5,
the second flow path has a sectional area that is smaller than a sectional area of each of the first flow paths, where an aspect ratio of the second flow path is less than 1.1, and
each inner end part of the heat transfer tube along the first direction includes the second flow path.
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