下向き水平伝熱面の沸騰熱伝達の研究
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概要
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The boiling heat transfer from a downward-facing, horizontal heating surface to saturated or subcooled water has been studied experimentally. The heating surface is one end of a copper cylinder with a diameter in 20mm, which is heated by an electric heater wound around it. Heat flux at the heating surface may be increased up to about 1.7×106W/m2. The system pressure was changed in the range from 0.01 MPa to 0.3 MPa and the subcooling in the range from 0℃ to 70℃. The experiments are performed under two conditions; (1) the heating surface is kept stationary in water and (2) the heating surface can be moved reciprocally between the vapor and the liquid at a period of 0.67 sec to 2 sec and cooled intermittently. Boiling curves are obtained for these two cases. From the observations, it is seen that, on the downward-facing heating surface, bubbles formed beneath the heating surface can easily coalesce and form a large blanket of vapor which prevents primary bubbles from separating on the heating surface. In such a case, the boiling curves obtained become discontinuous in the nucleate boiling region and, at low heat flux, they are shifted to the film boiling region. The burn-out heat fluxes are lower in comparison with that for an upward-facing, horizontal surface. The intermittent cooling due to the reciprocal motion of the heating surface and the pressures less than atmospheric pressure may reduce the value of burn-out heat fluxes.
- 長崎大学工学部,Faculty of Engineering, Nagasaki Universityの論文
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関連論文
- Film Boiling Heat Transfer from a Horizontal Circular Plate Facing Downward
- 有限の上向き水平面上の膜状凝縮熱伝達
- 下向き水平伝熱面の沸騰熱伝達の研究