高速加熱される伝熱面上の揺らぎ核生成時の沸騰伝熱挙動 : 第1報, 大気圧下における実験

概要

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Heat transfer during boiling and its relationship to the boiling configuration on a small platinum film heater immersed in subcooled ethyl alcohol at atmospheric pressure and heated so rapidly so as to realize the fluctuation nucleation on it are studied. The rate of temperature rise of the heater examined ranged from 5.7×10^5 K/s to 20×10^6 K/s. Concurrent generation of a large number of tiny bubbles, the behavior of which is well predicted by the theory of homogeneous nucleation, was observed at a higher rate. The tiny bubbles coalesced with each other to form a large bubble on the heater slightly after the boiling incipience and immediately before the transition to film boiling, which was identified by a sudden rise in the temperature time curve. At a high rate, no appreciable increase in the heat transfer rate after the boiling incipience was observed, whereas at a low rate, the increase rate of the wall temperature decreased due to a sudden increase in the heat transfer rate before the boiling transition. After the boiling transition, the heat flux decreased markedly to about 50% of the value before the boiling incipience. The coalesced bubble grew once and then contracted as a reaction of the excess growth due to inertia. The heat flux increased markedly when the bubble collapsed. The results for water are, in general, the same as those for ethyl alcohol.
一般社団法人日本機械学会の論文
1997-09-25