Mitsubishi Shindowh Co., Ltd.

Yoshikatsu Arayama

Shunroku Sukumoda

Haruo Kohno

Kohtaroh Nagahara

Makoto Miyauchi

Takashi Kazama

The object of the present invention is to offer a heat transfer tube having a grooved inner surface, wherein the side edges of the board material do not form a waved shape and cracks do not form during tube expansion. In order to achieve this object, the grooved-inner-surface heat transfer tube of the present invention has a metallic tube with an inner circumferential surface, on which are formed a weld portion which extends in an axial direction of this metallic tube, a pair of projecting strip portions formed parallel to and separate from this weld portion, and a plurality of fins formed in an area between these projecting strip portions. The fins are formed with a constant angle with respect to the tube axis, and the ends of these fins are connected with the projecting strip portions. The thickness of the metallic tube within the grooves formed between the fins is made to increase in approaching the weld portion within an area surrounding the weld portion wherein the central angle is within 30.degree..about.90.degree. on both sides from the center of the weld portion.

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Aizuwakamatsu, Japan

Yoshikatsu Arayama