【作者】 许超；

【导师】 高璞珍；

【作者基本信息】 哈尔滨工程大学 ， 核能科学与工程， 2010， 硕士

【摘要】 本文以去离子水为工质,对常压条件下的环形通道内过冷沸腾中的气泡行为进行了摄像可视化观察与实验研究。对于摄像可视化,基于图像处理技术,实验中进行了测试并对管道弧面的光学影响进行了校正计算讨论。结果表明,在低空泡份额下,该方法与采用快速截止阀法测量有着良好的吻合性。在中高空泡份额的情况中,由于气泡数量过多,形状任意,且存在重叠的情况,使得图形处理难以进行,误差极大。而必要的光学校正,有助于提高空泡份额的测量准确性。在单气泡方面,实验结果表明,滑移气泡的持续生长规律符合热力控制区Mihic方程。这说明滑移气泡在核化点处的生长符合Mihic惯性控制方程。气泡脱离频率与脱离直径,在本文实验条件下,不符合Ivey分区关系。根据实验数据采用对频率的隐格式得到了高度相关的拟合关系式。在理论和实验上证明气泡的上升速度正比于气泡直径的平方根值,且与工况参数无关。对阻力系数,验证了小雷诺数流动中主要的两个计算公式。对比值表明,阻力系数计算时应该考虑工质流动速度,并将其从气泡上升速度中扣除。气泡的形态主要受粘性与表面张力的影响,粘性与表面张力越小气泡的变形程度越大。在多气泡间行为方面,本文主要研究了两气泡之间的垂直追赶聚合现象和管道轴向空泡份额分布。相比于Fortes确定的聚合过程,实验中观察到在绕过上侧气泡之后还存在一个短暂的分离过程。气泡之间的聚合是大部分气泡从小气泡到大气泡的主要生长形式,也是壁面附近换热强化的主要方式。管道轴向空泡份额,在形式上与已知的理论与实验值一致。更多还原

【Abstract】 In this paper, by using the de-ionized water as the working fluid, photographic method and experiment are used to research the bubble behaviors in annular channel under subcooling natural circulation in low pressure.On the basis of photographic method, an experiment is designed to test the void fraction with photographic method and some optical corrections are discussed to the bubbles. Experimental results show that the method has the capacity of measuring of volumetric quality and section void fraction at low fraction, and match the valve cut-off method. At high fraction, bubbles are existing in great amount with random shapes and overlap each other. Thus, it’s hard to differentiate a single bubble in admissible error, and emendation would improve the measuring precision.On single bubble, the results show that growing sliding bubbles are accord to the Mihic function, which is belong to thermal phase. This means the growth at nucleate sites belong to the inertial phase. In the conditions of this paper, Ivey relationships gave higher results than experiment. Compared with experiment data, an implicit function for frequency is gotten, which is fit to the data well. Theoretical and experimental analysis proved that the rising velocity is in proportion to bubble diameter’s square root and independent of conditions. About resistance coefficient, two formulas of low Reynolds number flow are tested. Compared with data, the flow velocity should be minus by rising velocity in calculation of coefficient.The main factors which influence bubble shape are viscosity and surface tension. The viscosity and surface tension are lower, the bubble distortion is higher.On bubbles behaviors, aggregation and void distribution in axial direction are main research contents. In experiment, a departure phase is observed after tumbling phase, which is different from Fortes chart. From the experiment, the process of big bubbles coalesced small bubbles is the main mode of bubble growing to big bubble, and a way to enhance the heat transfer near the heat rod. As a whole, the axial distribution of void fraction is the same as the existing theory and experiment.更多还原