In this paper, an experimental apparatus was developed based on the evaporating water tower of the circuit bottom‐ash sluicing system. The formation and movement of single bubble that emerged from an orifice with 5 mm diameter in the middle of the tray were investigated by visual experiments, with water flow rates of 150, 200, and 250 L/h⁻¹, steam flow rate of 5 kg/h⁻¹, and nitrogen flow rates of 0.1632 and 0.32645 kg/h⁻¹. The lifetime of bubbles was recorded by high‐speed camera, and the characteristics of bubble deformation and movement were determined by image processing software Image Pro‐plus. Results showed that the lifetime of bubbles was divided based on the pictures into three parts, namely, formation, region, and oscillation regions. Bubble deformation and movement were assessed in each part. The equivalent radius of bubbles increased rapidly in the first region because of gas influx and grew more slowly in the two latter regions. The aspect ratio of bubbles changed from large to small in the formation region but surged in the oscillation region. The vertical velocity of the centroid of steam bubbles increased at the beginning and then fluctuated. However, the vertical velocity of the centroid of nitrogen bubbles increased over time due to the lack of mass transfer. The hollow phenomenon was found in steam and mixture bubbles through condensation. The effect of noncondensable gases on transmission was also discussed. With increasing nitrogen ratio, the time of formation and oscillation regions decreased for the mixed gas bubbles, leading to the deterioration of heat transfer in the tower. This work provides theoretical guidance for evaporating hot water tower operation.

中文翻译：

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溢流筛板热水塔中气泡的可视化研究

本文基于电路底灰泄水系统的蒸发水塔开发了一种实验装置。通过目视实验研究了从塔板中间直径为5 mm的孔口出来的单个气泡的形成和运动，水流量为150、200和250 L / h ^-1，蒸汽流量为5 kg / h ^-1，氮气流量为0.1632和0.32645 kg / h ^-1。气泡的寿命由高速相机记录，气泡变形和运动的特征由图像处理软件Image Pro-plus确定。结果表明，气泡的寿命根据图片分为三个部分，即形成区域，区域和振荡区域。在每个部分中评估气泡的变形和运动。由于气体的涌入，气泡的等效半径在第一个区域迅速增加，而在后两个区域则更慢。气泡的长宽比在形成区域中从大到小变化，而在振荡区域中则上升。蒸汽质心的垂直速度在开始时增加，然后波动。然而，由于缺乏传质，氮气气泡质心的垂直速度随时间增加。在蒸汽和混合物气泡中通过冷凝发现中空现象。还讨论了不可冷凝气体对传输的影响。随着氮比率的增加，混合气泡的形成时间和振荡区域减少，导致塔中传热的恶化。这项工作为蒸发热水塔的运行提供了理论指导。导致塔内传热变差。这项工作为蒸发热水塔的运行提供了理论指导。导致塔内传热变差。这项工作为蒸发热水塔的运行提供了理论指导。