| 摘要 |
In boiling heat transfer tube, fins 2 are provided on an outer surface of the tube body 1 in a manner such that the fins 2 each extend in a peripheral direction of the tube and a direction inclined to the tube axis at a pitch P2 in the tube axial direction. Protrusions 4 and recesses 5 are alternately formed in a length direction of a fin, a protrusion coming after a recess or vice versa, by being pressed. Opening 6 widths at the top ends of the cavity 3 between an adjacent pair of fins 2 are narrowed by inward jutting-out of the fins at both recesses 5 and protrusions 4. A profile of each of the protrusions in section perpendicular to the tube axis assumes a trapezoid. An opening width (W) between protrusions in section including the tube axis is 0.13 mm<W <=0.40 mm, an angle (theta) formed between opposed side surfaces of each recess in section perpendicular to the tube axis is 55 degrees or less. A pitch (P1) of the recesses or the protrusions in section perpendicular to the tube axis is 0.28 mm<=P1<=0.55 mm. A pitch (P2) of the cavities in section including the tube axis is 0.50 mm<=P2<=0.90 mm. Ribs are provided on an inner surface of the tube body in a spiral fashion, wherein a rib lead angle (alpha) to the tube axis is 41 degrees<=alpha<=50 degrees, a rib height (h) is 0.22 mm<=h<=0.45 mm and a rib pitch (P3) in a tube axial direction is 2.6 mm<=P3<=6.5 mm.
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