| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an inner helically grooved heat transfer tube capable of surely preventing degradation of heat transferring performance caused by crushing and falling of fins in expanding a tube. Ž<P>SOLUTION: A plurality of high fins 2 are arranged in the tube circumferential direction on a cross-section perpendicular to a tube axis, and three to five low fins 3 are disposed between the high fins 2. A height of the high fin 2 is 0.14-0.20 mm, an apex angle of the high fin 2 is 10-20°, a height of the low fin 3 is 0.10-0.14 mm, and an apex angle of the low fin 3 is 10-15°. The difference in heights between the high fin 2 and the low fin 3 is 0.04-0.06 mm. Lead angles of the high fin 2 and the low fin 3 are same as each other and kept within a range of 20-40°. Further apexes of the high fin 2 and the low fin 3 are curved faces respectively having a radius of curvature on the cross-section perpendicular to the tube axis. The radius of curvature of the apex of the high fin is 0.03-0.06 mm, and the radius of curvature of the apex of the low fin is 0.03-0.04 mm. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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