HEAT TRANSFER DOUBLE PIPE AND METHOD FOR MANUFACTURING SAME

An inner pipe (2) is used in a heat-transferring double pipe for exchanging heat between a fluid that flows through the interior of the inner pipe (2) disposed in the interior of an outer pipe and a fluid that flows between the inner pipe (2) and the outer pipe. The inner pipe (2) has a first region (21) and a second region, which have cross-sectional shapes that differ, and the first region (21) has a plurality of first protruding parts (211) that protrude outward and has a first recess-protrusion shape in which locations of the first protruding parts (211) are offset helically in a longitudinal direction. The second region has a plurality of second protruding parts that protrude outward, in which the number of second protruding parts is greater than the number of first protruding parts, and has a second recess-protrusion shape, in which locations of the second protruding parts are offset helically in the longitudinal direction.