| 摘要 |
PURPOSE:To improve nucleate boiling performance on the outside of a pipe, by providing a surface structure for promoting nucleate boiling also in the axial direction of the pipe as well as the circumferential direction of the pipe. CONSTITUTION:Circumferential cavities 1 extending helically aroung the circumference of a pipe is formed under the outer surface of the pipe at desired pitches in the axial direction of the pipe. Similarly, small axial cavities 3 are also formed under the outer surface of the pipe. Openings 2 formed discontinuously at the same pitches as the cavities 3, which are formed substantially continuously for communicating the cavities 1 to the outside, are shaped in irregular forms having many corrugations and ruggedness, and the maximum average width of the openings 2 is selected to be equal to or smaller than 0.13m/m. Further, it is preferable to select the maximum average width of the small axial cavities 3 and narrow interstices 4 communicated to the outside also to be equal to or smaller than 0.13m/m. Since, with such an arrangement, the configuration and surface conditions of the pipe are made preferable for forming many nuclei of bubbles, nucleate boiling can be promoted effectively markedly. |
