ABSTRACT

In order to develop models regarding subcooled boiling flow and its heat transfer, we conducted subcooled boiling experiments to investigate subcooled bubble formation and measured development process of the bubbles using a test loop with a vertical annulus flow path under atmospheric conditions. Two-phase flow parameters regarding subcooled boiling, such as instantaneous bubble velocity, turbulent velocity components, void fraction, onset of nucleate boiling (ONB) and onset of significant void (OSV), were obtained with two high-speed video cameras in high resolution in temporally and spatially. The identical bubbles were identified from the two video images taken by the high-speed video cameras, and the trajectories were reconstructed in three-dimensional. The instantaneous bubble velocities and turbulence velocity components regarding bubble transport were quantified with the trajectory data. It was observed that the bubbles were rising along the surface of the heater rod moved largely in the circumferential direction, and it was found from the result that velocity component for circumferential direction was enough large compared with that for radial direction.

摘要

为了开发有关过冷沸腾流动及其传热的模型，我们进行了过冷沸腾实验，以研究过冷气泡的形成，并在大气条件下使用具有垂直环形流路的测试回路测量气泡的发展过程。用两台高分辨率高速摄像机获得关于过冷沸腾的两相流参数，例如瞬时气泡速度、湍流速度分量、空隙率、核沸腾开始 (ONB) 和显着空隙开始 (OSV)在时间和空间上。从高速摄像机拍摄的两个视频图像中识别出相同的气泡，并在三维中重建轨迹。使用轨迹数据量化了与气泡传输有关的瞬时气泡速度和湍流速度分量。观察到气泡沿着加热棒的表面上升，沿圆周方向移动很大，从结果中发现，与径向相比，圆周方向的速度分量足够大。