D214 低圧条件における気泡直下伝熱面温度・熱流束分布計測(OS-15: 沸騰・凝縮伝熱および混相流の最近の進展(5))

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  • D214 Measurements of surface heat flux and surface temperature under a boiling bubble at low pressure condition

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Compared to single-phase flow, nucleate boiling has high heat transfer coefficient and is widely used in heat exchangers, boilers and BWR, etc. The nucleate boiling has been studied extensively but its heat transfer mechanism is still unknown. Recently, JAEA has developed a technology for the measurements of the surface heat flux and surface temperature distributions. The technology solved inverse heat conduction problem to get the surface heat flux and surface temperature distributions, with using a measured inside wall temperature distribution data from self-developed high sensitive temperature sensors. The temperature sensors are allocated in high density (utmost 6 points in 1 mm), at a depth several micro meters beneath the heated surface. In this paper, with using the developed technology, we measured the surface heat Flux and surface temperature distributions under a nucleate pool boiling bubble at both atmospheric pressure and a lower pressure. Image information of boiling bubble was recorded with a high speed camera synchronized with the temperature measurements. To control the position of boiling bubble, we mirror processed the heated surface and formed a nucleus at the center of the surface. Temperature sensors are allocated beside the nucleus, in a density of upmost 6 points per 1mm and at a depth about 1.4μm beneath the surface. Based on the experimental data, we examined boiling heat transfer models. In the present experimental conditions, surface heat flux distribution in the boiling process shows contact line heat transfer model is correct.

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