膜沸騰蒸気膜の伝ぱ的崩壊に関する研究 : 伝熱面温度が液の過熱限界温度以上における膜沸騰蒸気膜の崩壊機構

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The mechanism of propagative collapse of a vapor film at high wall superheat and the effect of a local-cold spot on the minimum-heat-flux(MHF)temperature and collapsing fashion in film boiling were investigated experimentally and analytically. Using a 1 mm diameter and 160 mm long platinum wire, pool film-boiling experiments were performed for saturated or subcooled water at atmospheric pressure. In the experiments, temperatures of electrodes which served as the cold spots of the test section were varied in a range from 250 to 450 °C. Experimental results showed that the propagation velocity of vapor film collapse decreased and the MHF temperature increased with a decrease in the local-cold spot temperature. In particular, when the local-cold spot temperature was lower than the thermodynamic limit of liquid superheat, the MHF temperature increased remarkably. Application of the Yamanouchi model for rewetting of a hot surface by a falling film to the present vapor film collapse was successfully tested by including conventional MHF-temperature and critical -heat-flux correlations. Furthermore, a more precise model was developed by coupling heat conduction and a full boiling curve as the boundary condition. The propagation velocities measured were well represented by this model. It was proved that local temperature at a collapsing front of the vapor film, that is the local solid surface temperature at the initiation of liquid-solid contact, never exceeds the thermodynamic limit of liquid superheat even if the collapse of the vapor film occurs at high wall superheat.
一般社団法人日本機械学会の論文
2000-12-25

膜沸騰蒸気膜の伝ぱ的崩壊に関する研究 : 伝熱面温度が液の過熱限界温度以上における膜沸騰蒸気膜の崩壊機構

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