| 摘要 |
PROBLEM TO BE SOLVED: To enhance heat transfer performance in a heating tube by sectioning the inner face of the heating tube into a plurality of regions of specified width at a specified angle from the center of the tube along the axis thereof, making a large number of grooves in parallel in each region, and differentiating the lead angle, the pitch, or the like, of the groove between adjacent regions. SOLUTION: A heating tube (a) has inner surface sectioned into regions 1a-1h of uniform width at an angle of 20-50 deg. from the center of the tube along the direction of the tube axis and a large number of grooves 10 are made in parallel in each region 1a-1h. The lead angleθ1 of the groove made in the region 1a, 1c, 1e, 1g with respect to the tube axis is set at 40 deg., for example, and the lead angleθ2 of the groove made in the adjacent region 1b, 1d, 1f, 1h is set at 10 deg., for example. Since the lead angle of the grooves 10 is differentiated, flow of coolant is disturbed in the tube and heat transfer performance in the tube is enhanced. Furthermore, a metal material is prevented from being shifted at the time of making the groove 10 because the inner surface of the tube is sectioned into a plurality of regions.
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