著者

新井 崇洋 古谷 正裕

出版者

社団法人 日本伝熱学会

雑誌

日本伝熱学会論文集 (ISSN:09189963)

巻号頁・発行日

vol.15, no.3, pp.91-100, 2007 (Released:2008-02-25)

参考文献数

10

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We proposed ultra rapid solidification and atomization technique, CANOPUS (Cooling and Atomizing based on NOble Process Utilizing Steam explosion), using small-scale vapor explosions to make an amorphous metal. The CANOPUS method is suitable for rapid cooling and atomization process, which utilizing sustainable small-scale vapor explosions. In order to apply the CANOPUS method to a high melting point metal, it is necessary to make a small-scale vapor explosion occur at a high temperature of the molten metal. Small-scale experiment is conducted to develop the vapor explosion promotor in which spontaneous vapor explosion can occur at a high temperature of a molten metal. Spontaneous vapor explosion do not occur when water at 80°C is used as a coolant. However, spontaneous vapor explosion occurs when water at 80°C with salt additives is used as a coolant. Specifically, lithium chloride solution generates spontaneous vapor explosions at the highest temperature of the molten tin in the experiment. In order to clarify the triggering mechanism of the spontaneous vapor explosion when the promotor is used as a coolant, a high-temperature solid stainless steel sphere is immersed into a coolant. The interfacial temperature of the stainless steel sphere is measured, and the behavior of a vapor film around the stainless steel sphere is observed with a digital video camera. As a result, salt additives resulted in an increase of quench temperature in all salt solutions. The quenching curves of each coolant indicate that the salt additives improve the film boiling heat transfer. The improvement of the film boiling heat transfer causes an unstable formation of the vapor film and a rise of the quench temperature. It is clarified that the salt additives to water promotes a vapor film collapse. Comparing two experiments, the quench temperature of each solution is in close agreement with the upper limit of the molten tin temperature that causes spontaneous vapor explosion. This result suggests that the vapor film collapse triggers spontaneous vapor explosion.

著者

阿部 豊 新井 崇洋

出版者

日本機械学会

雑誌

日本機械学會論文集. B編 = Transactions of the Japan Society of Mechanical Engineers. B (ISSN:03875016)

巻号頁・発行日

vol.71, no.702, pp.658-665, 2005-02-25

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Spontaneous vapor explosion can occur when a layer of the high temperature molten material lies on the water pool or on the moisture floor. This is so-called base-triggered vapor explosion. The base-triggered vapor explosion is supposed to occur in the case of a severe accident in various industrial facilities. It is very important to clarify the occurrence condition and possibility of the base-triggered vapor explosion from the viewpoints of the prediction and the prevention of the vapor explosion. In order to evaluate the occurrence conditions and to clarify the micro-mechanism of the base-triggered vapor explosion, the experimental apparatus to observe the base-triggered vapor explosion from the bottom of the floor to above is designed and constructed. The experiments using U-Alloy95 as a simulant material are conducted. Consequently, the microscopic behavior at the interface between the molten material and water can be observed in detail with this experimental apparatus. The interfacial behavior of the molten material is quantitatively evaluated by the PIV analysis and the digital auto-colrrelation method with the experimental results. The blowout velocity of the molten material at vapor explosion is evaluated from the visual data obtained on the experiment. The generated pressure at the vapor explosion is estimated by using the blowout velocity. In addition, occurrence condition of the base-triggered vapor explosion is evaluated with the thermal interaction zone (TIZ) theory.

著者

新井 崇洋 阿部 豊 佐藤 健一郎 中川 裕二

出版者

一般社団法人日本機械学会

雑誌

年次大会講演論文集 : JSME annual meeting

巻号頁・発行日

vol.2004, no.3, pp.221-222, 2004-09-04

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Spontaneous vapor explosion can occur when a layer of the high temperature molten material lies on the water pool or on the moisture floor. This is so-called base-triggered vapor explosion. The base-triggered vapor explosion is supposed to occur in the case of a severe accident in a nuclear reactor and in other industrial facilities. It is very important to clarify the base-triggered vapor explosion from the viewpoints of the prediction and the prevention of the vapor explosion. In order to evaluate the heat transfer and fluid dynamic behavior of the base-triggered vapor explosion, the experimental apparatus is designed and constructed. The experiments using U-Alloy95 as a stimulant material are conducted. Consequently, the behavior of the molten material can be observed in detail with this experimental apparatus. The digital auto-correlation method and PIV are also applied to the visual observation data obtained on the experiments in order to evaluate the velocity distribution of the molten material. Based on the velocity, the conversion ratio of kinetic energy in initial thermal energy at the vapor explosion is also evaluated. In addition, the experimental results are compared with the thermal interaction zone (TIZ) theory in order to evaluate the occurrence condition of base-triggered vapor explosion.