| 摘要 |
<p>Provided is a heat transmission tube wherein the heat transfer rate within a tube can be improved while the increase of a pressure loss is suppressed. A heat transmission tube (11) having an outer diameter of less than 7 mm has an inner surface (10) on which a helical fin (12) that is oriented at a predetermined angle (ß1) with respect to a tube axis direction (D1) and has a height (Hf) of 0.1 to 0.30 mm is formed. In the heat transmission tube (11), the fin (12) is comprised of fin components (12A) divided by a subsidiary helical groove (14) having a depth (Hn) of 0.1 to 0.30 mm. Each fin component (12A) is provided with a protrusion piece (16) on at least the downstream side (D2d) in the helical direction. The protrusion piece (16) is projected at an angle (a) of 5°=a<70° with respect to the fin (12) between the adjacent portions of the fin (12) on the upstream side (D1u) in the tube axis direction. The fin components (12A) are formed so that the distance (Pf) between the fin components (12A) in the fin forming direction is 1.5 mm or more, and the ratio (W1/W2) of the length (W1) of the protrusion piece (16) to the distance (W2) between the protrusion pieces (16) is 0.3 to 0.9.</p> |
