An abnormal phenomenon which appears after critical heat flux and before minimum heat flux in pool boiling is introduced. We do not know why this phenomenon occurs only in a certain range of subcooling and is never observed for saturated liquid. Why a cycle of wet and dry occurs between minimum and critical heat fluxes appears during cooling is still unknown. An interesting phenomenon is observed during quenching with impinging jet cooling, which can be categorized into three different characteristics: the first one is homogeneous nucleation, second is repetition of wet and dry, during which surface is gradually cooled and then a well wetted condition by which the surface is rapidly cooled. A model is tentatively proposed to explain the mechanism of homogeneous nucleation.

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This paper summarizes wetting phenomena and heat transfer characteristics on high wall superheated surface. Especially, rewetting conditions on high temperature surface is examined experimentally, focusing on the thermodynamics limit of superheat. Heat Transfer during the wetting is also measured.

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Effects of surface wettability on liquid-vapor phase change phenomena and single- and two-phase flow in tube have been studied in wide range of contact angles using superhydrophilic (SH) and super-water-repellent (SWR) surfaces. Heat transfer in falling film evaporation on a TiO_2-coated SH surface is tremendously enhanced due to very thin stable film. Wetting limit temperature of water drop on heated surface increases with the decrease in contact angle. In pool boiling on SWR surface, bubble nucleation and film boiling occur in extremely small superheating.

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In this paper we give an overview of some novel mechanisms in insect-and bird-flight and their potential of applications to the Micro Air Vehicle (MAV). Till now robotic flapper has been mostly responsible for study of insect/bird flapping wing mechanisms as in hovering flight but quick-turn like freely flapping flight keeps unknown. To provide an overall understanding of aerodynamic and dynamic mechanisms in flying insects and birds we have succeed in establishing a biology-inspired dynamic flight simulator as well as a robotic flapping model which is capable to mimic hovering, forward flight and quick-turn on a basis of modeling of realistic geometry and wing kinematics, and modeling of wing-body flight dynamics. It is expected that this simulator is capable to quantify and unveil the mechanisms in biological flapping flight and to provide some novel theories and technical innovations for research and development in the Micro Air Vehicles.

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[in Japanese]

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