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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

STUDY ON SUPERHEATED LIQUID LAYER IN POOL BOILING

Mao Takeyama
Department of Nuclear Engineering, Kyoto University, Kyoto-Daigaku Kastura, Nishikyo-Ku, Kyoto, 615-8540 Japan

Tomoaki Kunugi
Department of Nuclear Engineering, Kyoto University, Kyoto Daigaku-Katsura, Nishikyo-ku, Kyoto, Japan

Takehiko Yokomine
Advanced Energy Engineering Science, Interdisciplinary Graduate School of Engineering Science, Kyushu University, Kasuga-kouen 6-1, Kasuga, Fukuoka 816-8580, JAPAN; Department of Nuclear Engineering, Kyoto University, Kyoto-Daigaku Kastura, Nishikyo-Ku, Kyoto, 615-8540 Japan

Zensaku Kawara
Department of Nuclear Engineering, Kyoto University, Kyoto-Daigaku katsura, Nishikyo-ku, Kyoto, 615-8540, Japan

DOI: 10.1615/IHTC16.bae.023750
pages 1405-1411


KEY WORDS: Temperature Measurement, Miniature Thermocouple Probe, Pool Boiling, Superheated Liquid Layer, Transient Conduction, High Speed Visualization

Abstract

This paper describes the temperature measurement surrounding of an isolated vapor bubble on the upward flat plate in the pool boiling. The heated surface is covered with a superheated liquid layer during boiling, and its thickness attenuates because of the vapor bubble growing, its departure, and its entraining the bulk liquid. It needs several milliseconds before the superheated liquid layer develops again. After that a nucleate bubble is generated, this period is called a waiting time. Previous several studies reported that the transient conduction, during the wall rewetting process and the regrowth of superheated liquid layer, is the dominant mechanisms in boiling heat transfer. This has been indicated by many experiences regarding the measurement of temperature and heat flux of heater surface. The purpose of this study is to measure the transient temperature profile near and inside the isolated boiling bubble with a miniature thermocouple and clarify the transient feature. The behaviors of isolated boiling bubble on an artificial heater were observed because boiling phenomenon is very complex. In the experiment, temperature was measured with a sharp-edged K-type miniature thermocouple probe at three vertical and horizontal locations. The high spatiotemporal visualization by a high-speed camera and the temperature measurement of 10kHz sampling rate were conducted simultaneously. Temperature variations induced by vapor bubble behavior, such as removing the superheated liquid layer, its regrowth process and bulk liquid agitation, were discussed.

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