3519 強制対流サブクール沸騰の可視化実験(S49-2 流動,原子炉用機器(1),S49 原子炉システムおよびその要素技術)

概要

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Vapor bubbles in water subcooled flow boiling were observed visually to investigate the bubble rise characteristics after the departure from a nucleation site and the mechanism of the increase of void fraction with wall heat flux. Three typical bubble rise paths were observed in the present experimental setup: some bubbles slid upward the vertical wall for long distance, while other bubbles were detached from the wall after sliding for several millimeters and then migrated toward the bulk liquid; after the migration, some of the detached bubbles were collapsed in subcooled liquid but others remained close to the wall and were reattached eventually to the wall. It was suggested that the variation in bubble shape from flattened to more rounded was of primary importance for the occurrence of bubble detachment. The dependence of void fraction on heat flux was influenced significantly by the mass flux: the void fraction increased smoothly with heat flux at low mass flux while the increase of void fraction with heat flux was almost negligible near the onset of nucleate boiling (ONB) at high mass flux. It was considered that the difference in bubble size caused the difference in the dependence of void fraction on heat flux.
社団法人日本機械学会の論文
2005-09-18