On the Heat Transfer Mechanism and Stability of High Heat Flux Microbubble Emission Boiling

高热通量微泡发射沸腾传热机理及稳定性研究

• 批准号: 05805021
• 负责人: KUMAGAI Satoshi
• 金额: $ 1.34万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05805021/
• 关键词: Boiling Heat Trnasfer; Microbubble Emission Phenomena; Liquid Subcooling; Bubble Motion; Pressure Fluctuation; Boiling Sound Frequency Characteristics; 気泡挙動; サブクール; 沸騰音

Microbubble Emission Boiling (MEB) is the regime that occurs in the transition process from nucleate to film boiling with high liquid subcooling condition, and realizes extremely high heat flux without a marked increase in the amount of wall superheat. MEB has unique aspects different from that of ordinary boiling, such as a profusion of microbubbles emitted from a heat transfer surface. This experimental investigation reveals that this phenomenon includes two regimes, i.e., the stormy and calm microbubble emission boilings. This study also shows temperature fulctuations of a heat transfer surface and pressure fluctuations in the liquid near the surface to classify MEB into the above regimes. The temperature fluctuations in either regime are smaller than those at the critical heat flux. The pressure fluctuations are larger in the stormy MEB,and smaller in the calm MEB as compared with those at the critical heat flux. The liquid subcooling and flow velocity approaching the surface are i … More mportant aspects by which to generate those regimes. A number of experiments lead to the map of MEB regimes that consists of liquid subcooling and flow velocity. An oscillatory character between the two regimes appears under several conditions.The frequency distribution of sound pressure level when MEB exists, has two peak levels. The first peak that appears from 500 [Hz] has the highest sound pressure level and is difficult to be found out in nucleate boiling region. The second peak appears from 8000 to 16000 [Hz] and this peak is not only in MEB region but also in nucleate boiling region, especially with high liquid subcooling. The intensity of the both peaks is depending on liquid subcooling and heat flux. Bubbles in MEB region collapse toward the heat transfer surface. Bubble collapse frequency and sound pressure level of MEB have similar frequency distributions. Consideration of the above results lease to a hypothesis that collapse of a bubble is an important or controlling factor of the heat transfer mechanism of MEB. Less

微泡发射沸腾(MEB)是在液体过冷度较高的条件下，发生在核态沸腾向膜状沸腾过渡过程中，在不显著增加壁面过热度的情况下，实现极高热流密度的一种现象。MEB具有不同于普通沸腾的独特方面，例如从换热表面散发出大量的微泡。实验研究表明，这一现象包括两个区域，即风暴式和风平式微气泡排放沸腾。本研究还显示了换热表面的温度波动和近表面液体中的压力波动，从而将MEB归类为上述区域。这两种情况下的温度波动都小于临界热流密度下的温度波动。与临界热流率相比，风暴区压力波动较大，风平区压力波动较小。液体过冷度和接近表面的流速均为I…更重要的方面，以产生这些制度。大量实验得到了由液体过冷度和流速组成的MEB区域图。在几种情况下，声压级在两种情况下都表现出振荡特征，存在时声压级的频率分布有两个峰值。在500[Hz]处出现的第一个峰具有最高的声压级，在核沸腾区域很难找到。第二个峰出现在8000~16000[Hz]范围内，该峰不仅出现在MEB区，而且还出现在核沸腾区，特别是在液体过冷度较高的区域。这两个峰的强度取决于液体过冷度和热流密度。MEB区域的气泡向换热面坍塌。气泡破裂频率和声压级具有相似的频率分布。考虑到上述结果，提出了一个假设，即气泡的破裂是MEB换热机理的一个重要或控制因素。较少

项目成果

久保 良: "気泡微細化沸騰の発生音と熱伝達の相関性" 日本機械学会論文集 B編. 59. 183-190 (1993)

Ryo Kubo：“气泡细化沸腾产生的声音与传热之间的相关性”，日本机械工程学会会刊，B 版，59. 183-190 (1993)。

R.KUBO and S.KUMAGAI: "Occurrence and Stability of Microbubble Emission Boiling -Stormy and Calm Regimes-" Proceedings of the 10th International Heat Conference. 5. 99-104 (1994)

R.KUBO 和 S.KUMAGAI：“微泡发射沸腾的发生和稳定性 - 暴风雨和平静的状态 -”第十届国际热学会议论文集。

R.KUBO,R.SHIMAD and S.KUMAGAI: "Relationship between Sound and Heat Transfer on Microbubble Emission Boiling" Transaction of the Japan Society of Mechanical Engineers. 59-557. 183-190 (1993)

R.KUBO、R.SHIMAD 和 S.KUMAGAI：“微泡发射沸腾中声音与传热的关系”日本机械工程师学会会刊。

M.KAWASAKI,S.KUMAGAI and R.KUBO: "Microbubble Emission Boiling from a Vertical Surface" Proceedings of the 31st National Heat Transfer Conference. 2. 424-426 (1994)

M.KAWASAKI、S.KUMAGAI 和 R.KUBO：“垂直表面的微泡发射沸腾”第 31 届全国传热会议论文集。

Ryo KUBO: "Occurence and Stability of Microbubble Emission Boiling-Stormy and Calm Regimes-" Proceedings of the 10th International Heat Transfer Conference. 5. 99-104 (1994)

Ryo KUBO：“微泡发射沸腾的发生和稳定性——暴风雨和平静的状态——”第十届国际传热会议论文集。