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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Boiling Behaviors on a Vertical Surface in Saturated Pool Boiling at High Pressures

Get access (open in a dialog) DOI: 10.1615/IHTC15.pbl.009772
pages 6125-6136

Аннотация

Experiments were carried out to observe boiling behaviors of water and ethanol on a flat copper surface at pressures from 0.25MPa to 3MPa. The heating surface was placed vertically in a high pressure cell and the boiling behaviors were observed through an optical window using high-speed video with a maximum 8000 fps and a microscope with a maximum 320-fold magnification. The growth curves of the primary bubbles are well described by the t1/2 variation over the whole range of pressures. The growth rates of primary bubbles are proportional to the square root of the Jakob number, and agree with the correlation by Labuntsov et al. The conventional correlation for the bubble growth rates, which is directly proportional to the Jakob number, predicts considerably slower growth rates at higher pressures. The dependence of nucleation site densities on the heat flux is very similar to the results obtained near atmospheric pressure where the nucleation site density is proportional to the 1.5th power of the heat flux. To examine the heat transfer characteristics in nucleate boiling at high pressures, the measured data of heat fluxes, superheats, and nucleation site densities were arranged using the available correlations. It was found that the present data arrange fairly well by the correlation developed by Sakashita and Kumada for both water and ethanol in the 0.25 to 3MPa range of pressures and at heat fluxes of 0.02 to 0.6MW/m2.