Rate of Heat Transfer between a Fluidized Bed and the Tube Wall at Higher Temperature

The heat transfer coefficient between a fluidized bed and the tube wall, hw, was measured in the temperature range of 500° to 800°C. Quartz and fused alumina particles were fluidized in the air stream. The coefficient hw was obtained between 70 and 800 kcal/m²·hr·°C. It increases with the flow rate of air. The effects of bed temperature and heat content and size of the particles on hw were imperceptible. By comparing the heat transfer coefficients obtained in this work with those at lower temperatures below 200°C, the difference between both coefficients was not significant

リュウドウソウニオケルキコソウハンノウノソクドロンテキケンキュウ

京都大学0048新制・課程博士工学博士甲第1562号工博第398号新制||工||297(附属図書館)4084UT51-50-A371京都大学大学院工学研究科冶金学専攻(主査)教授 近藤 良夫, 教授 森山 徐一郎, 教授 盛 利貞学位規則第5条第1項該当Kyoto UniversityDA

In Situ Observation of Dynamic Meniscus Front Interface in Alkaline Fuel Cell

Controlling the wetting properties at the three-phase interface is important for improving the performance of alkaline fuel cells. The meniscus of a potassium hydroxide droplet was formed on a nickel electrode, and the interference fringe during the oxygen reduction reaction was observed by confocal laser microscopy. The high spatial resolution of the microscope revealed thin film formation at the meniscus front interface. The thickness decreased with increasing cathodic potential. The generation of microscopic convection by interfacial surface tension may affect mass transfer in the thin film

Observation of Three-Phase Interface during Hydrogen Electrode Reactions in Unitized Regenerative Fuel Cell

The dynamic behavior of the meniscus of a potassium hydroxide and sulfuric acid droplet on a platinum electrode was studied using a charge-coupled device (CCD) camera and confocal laser microscopy. The three-phase interface was investigated during the hydrogen oxidation reaction (HOR) and the hydrogen evolution reaction (HER). Contact angle measurements revealed a spreading interface during the HER whereas the droplet shape remained unchanged during the HOR for both droplets. The overhead view revealed the formation of many fine droplets near the meniscus boundary during the HOR in the alkaline electrolyte, which agrees with previous results for the oxygen reduction reaction (ORR). The correlation of these observations with electrochemical data and differences in the results between the HOR and the HER suggest that the motion of the meniscus was induced by local pH and temperature gradients, presumably caused by a non-uniform reaction because of the limitations of the dissolved gas

Mechanisms for Enhanced Hydrophobicity by Atomic-Scale Roughness.

It is well known that the close-packed CF3-terminated solid surface is among the most hydrophobic surfaces in nature. Molecular dynamic simulations show that this hydrophobicity can be further enhanced by the atomic-scale roughness. Consequently, the hydrophobic gap width is enlarged to about 0.6 nm for roughened CF3-terminated solid surfaces. In contrast, the hydrophobic gap width does not increase too much for a rough CH3-terminated solid surface. We show that the CF3-terminated surface exists in a microscopic Cassie-Baxter state, whereas the CH3-terminated surface exists as a microscopic Wenzel state. This finding elucidates the underlying mechanism for the different widths of the observed hydrophobic gap. The cage structure of the water molecules (with integrated hydrogen bonds) around CH3 terminal assemblies on the solid surface provides an explanation for the mechanism by which the CH3-terminated surface is less hydrophobic than the CF3-terminated surface