ABSTRACT Experiments on subcooled flow boiling have been carried out to investigate the dynamical parameters and thermal impact of a growing vapor bubble under vertically upward and downward flow configurations with water as the fluid medium. Bubble growth and detachment phenomena have been visualized in real-time using high-speed rainbow schlieren technique. Schlieren-based imaging technique simultaneously maps both the bubble dynamics and thermal gradients field along the heater surface. Experimental data have been compared for a range of Reynolds number (Re = 3600–7200) at a constant subcooling level of ΔTsub = 4°C. The thermal aspects have been identified in the form of real-time visualization of thermal boundary layer and its scavenging as the bubble detaches/lifts-off from the heater surface. Time variation of various bubble dynamic parameters have been determined from the quantitative processing of the schlieren images. Significant differences in the bubble trajectory after departure from the nucleation site were observed for downward and upward flow configurations. For Re ≤ 6000, comparatively higher evaporative heat flux dissipation was obtained for upward flow, while at Re ≥ 6000, the evaporative heat flux dissipation was found to be more or less similar for both upflow and downflow configurations.

中文翻译：

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比较受向上和向下流动沸腾配置的单个蒸汽泡的动力学和热影响的实验

摘要 已经进行了过冷流沸腾实验，以研究在以水为流体介质的垂直向上和向下流动配置下不断增长的蒸汽泡的动力学参数和热影响。气泡生长和脱离现象已使用高速彩虹纹影技术实时可视化。基于纹影的成像技术同时绘制沿加热器表面的气泡动力学和热梯度场。在 ΔTsub = 4°C 的恒定过冷度下，比较了一系列雷诺数 (Re = 3600–7200) 的实验数据。热方面已经以热边界层的实时可视化及其清除的形式确定，因为气泡从加热器表面分离/升起。从纹影图像的定量处理中确定了各种气泡动态参数的时间变化。对于向下和向上流动配置，观察到离开成核位点后气泡轨迹的显着差异。对于 Re ≤ 6000，向上流动获得了相对较高的蒸发热通量耗散，而在 Re ≥ 6000 时，发现向上流动和向下流动配置的蒸发热通量耗散或多或少相似。