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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Subcooled flow boiling of water with microbubble emission in a horizontal channel (Boiling characteristics of various channels)

Get access (open in a dialog) DOI: 10.1615/IHTC12.1590
6 pages

Abstract

Flow boiling of water with high subcooling of liquid was investigated for various rectangular and circular channels. The rectangular channels were 150 mm in length, 14 mm in width and 1 mm, 3 mm and 5 mm in height. A square heating surface with dimensions of 10 mm × 10 mm was placed on the bottom surface of the channel. The circular channels were 200 mm in length and 5 mm, 10 mm and 16 mm in diameter, and the heating section was 10 mm in length. The tested liquid subcooling was 20 ~ 40 K and the velocity was 0.3 m/s and 0.5 m/s. Microbubble emission boiling was observed in most of the channels in transition boiling and the heat flux increased higher than the critical heat flux. The maximum heat flux as high as 8 MW/m2 was obtained.
Periodic pressure fluctuation and periodic motion of coalesced bubbles were observed in microbubble emission boiling. In the periodic type of microbubble emission boiling, it is considered that the frequency of pressure fluctuation corresponds to the cycle of bubble collapse and liquid supply. The heat flux increased with increasing pressure frequency. The periodic bubble behavior and the close connection between the relation of heat flux and the pressure frequency are considered as one mode of microbubble emission boiling.