AUTHOR=Ren Tingting , Zhu Zhiqiang , Zhang Rui , Shi Jiangwu , Yan Changqi TITLE=Visualization Experiment of Bubble Coalescence in a Narrow Vertical Rectangular Channel JOURNAL=Frontiers in Energy Research VOLUME=8 YEAR=2020 URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2020.00096 DOI=10.3389/fenrg.2020.00096 ISSN=2296-598X ABSTRACT=

Visualization experiments were carried out and sliding bubble coalescence behaviors were observed for subcooled flow boiling in a narrow rectangular channel. The results show that the consecutive coalescence process is composed of four steps based on the bubble morphological change: approaching, merging, adjustment, and stabilization, in which the more important are the merging and adjustment of the bubble. Bubble always slides along the heating surface and does not lift off in coalescence process. Bubble diameter and sliding velocity increase first, then decrease and finally stabilize. Bubble shape also oscillates from an irregular ellipse to a stable circle. In addition, a new small bubble may be induced in the coalescence process.