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Science and Technology of Nuclear Installations
Volume 2012 (2012), Article ID 785157, 15 pages
Research Article

Experimental Investigation of Rising Gas Bubble Characteristics from a Vertical Tube under CCFL Condition

Faculty of Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi Ibaraki 316-8511, Japan

Received 11 November 2011; Accepted 10 January 2012

Academic Editor: Michio Murase

Copyright © 2012 Kunihito Matsumura and Fumito Kaminaga. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This paper describes an experimental study of gas/liquid countercurrent flow in a vertical circular tube. CCFL experiments were carried out with three different water levels in the upper plenum, two different tube diameters. Measurements were made for liquid and gas flow rates, time variations of pressure at locations of the upper entry of the tube and lower plenum. Visual observations were also conducted to investigate the relationship between rising gas bubble characteristics and time variation of gas pressure at the upper entry of the tube. The results indicate that one bubble formation cycle (e.g., bubble growth, expansion, and detachment into the water pool) corresponds to one pressure fluctuation cycle. For the 20 mm diameter tube, it was confirmed that there was a characteristic waiting time between bubble cycles in which no bubble was formed at the upper entry of the tube. The waiting time is a favorable time for a liquid introduction into the tube from the upper plenum. The bubble volumes are compared with existing bubble formation correlations.