The Japan Steel Works, Ltd.

Mitsubishi Shindowh Co., Ltd.

Kohtaroh Nagahara

Shunroku Sukumoda

Takashi Iwamoto

Haruo Kohno

Yukio Sato

Yasushi Owaki

Masayuki Kawai

Shinichi Ono

Yoshikatsu Arayama

Makoto Miyauchi

Takashi Kazama

Masashi Tomiie

In a heat transfer pipe, annular grooves in a direction inclined at an angle of 45&deg; to 90&deg; with respect to an axis of the pipe are continuously formed at an interval in a longitudinal direction of the pipe. The annular grooves desirably have a groove depth of 0.20 mm or more, and a groove pitch of two to five times larger than the groove depth. Moreover, a ratio W/P of a bottom width W of projections of the grooves to the groove pitch P is desirably 0.1 to 0.9.

Heat transfer pipe for liquid medium having grooved inner surface and heat exchanger employing the same

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.

Heat transfer tube having grooved inner surface and production method

Growing community of inventors

Aizuwakamatsu, Japan

Kohtaroh Nagahara