著者

北川 石英 山本 和明 村井 祐一

出版者

The Japan Society of Mechanical Engineers

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.78, no.793, pp.1539-1549, 2012

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This paper describes effects of microbubble injection on natural convection heat transfer from a vertical heated plate in water. Thermocouples are used for the temperature measurement and an image processing technique is used for obtaining the bubble diameter, the bubble velocity and the bubble layer thickness. The working fluid used is tap water, and hydrogen bubbles generated by electrolysis of the water are used as the microbubbles. For a constant bubble flow rate and a constant wall heat flux, in the laminar and transition regions, the heat transfer coefficient is significantly increased by the microbubble injection (The ratio of the heat transfer coefficient with bubble injection to that without injection is 1.6-2.0 in both regions). The heat transfer enhancement in the laminar region results from both the forced-convection and mixing effects due to microbubble injection. On the other hand, the heat transfer enhancement in the transition region is mainly affected by acceleration of the transition to turbulence due to microbubble injection.