气体横掠顺排管束流动特性实验研究

螺旋管式换热器换热系数高且结构紧凑,被用于高温气冷堆蒸汽发生器及中间换热器。这类换热器壳侧为有壁面包围的横掠管束流动,而壁面的存在会对横掠管束流动产生一定影响。本文中采用分裂式热膜测量了不同管距管径比(P/D)和不同雷诺数(Re)下横掠顺排管束流动管间和管后的速度分布。讨论了流动充分发展区域P/D、Re对管间和管后时均速度分布的影响。然后分析了P/D、Re对管间和管后雷诺正应力分布的影响。选取Re=35875的结果,从频谱角度分析了产生不同雷诺正应力分布的原因,并比较了P/D对管间速度频谱的影响。

液态铅铋合金横掠管束对流换热数值计算

直流螺旋管式蒸汽发生器具有结构紧凑和换热系数高等优点,能够进一步提高液态金属反应堆的紧凑性和经济性。此时蒸发器壳侧为液态金属横掠管束流动,而在可查阅文献中专门针对液态金属横掠顺排管束的换热关系式却很有限。本文采用SST k-ω模型和湍流普朗特数模型数值研究了液态铅铋合金横掠顺排管束的流动和换热特征。首先采用前人的实验结果对数值模型进行了验证,模拟结果与努塞尔数实验值偏差小于8%。研究了普朗特数、雷诺数以及管束结构对液态金属横掠顺排管束换热特征的影响。讨论了不同工况下分子热扩散系数和湍流热扩散系数对于换热的贡献以及传热管周向局部换热特征。最后根据计算结果拟合出了液态铅铋合金横掠顺排管束的努塞尔数公式。

High-speed experimental photography of collapsing cavitation bubble between a spherical particle and a rigid wall

The synergetic effects between cavitation bubbles and silt particles on the damages of materials are essential problems in fluid machineries. For studying the underlying microscopic mechanisms, in the present paper, the dynamic behaviors of a single cavitation bubble between a spherical particle and a rigid wall are experimentally investigated with a high-speed camera. The results indicate that the existence of the particle can affect the bubble shape during collapse and significantly accelerate the collapse velocity of the bubble. The influences of the particle size, the distance between the bubble and the particle and the distance between the bubble and the rigid wall on the phenomena are qualitatively and quantitatively analyzed. These parameters can prominently affect the collapse velocity of the bubble(especially its maximum value).