| 摘要 |
A cylindrical pipe which is excellent in heat transfer characteristic and has no accumulation of liquid, wherein a flat-shaped portion (2) along the pipe axis (L) is formed inside the cylindrical pipe (1) formed in corrugated shape. As a method for manufacturing said pipe, the present invention provides a pipe manufacturing method, wherein a thin-wall blank cylindrical pipe (P) is fed in increments of a prescribed distance, while being rotated at a definite speed, a roller die (85) being pressed against the outer periphery of the cylindrical pipe, the roller die being advanced and retracted in accordance with the feed of the cylindrical pipe, for forming a spiral corrugation such that the groove depth thereof is gradually increased, starting from the flat portion of the cylindrical pipe, and reaches a maximum in the portion opposed to the flat one.
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