TED-AJ03-656 CHARACTERISTICS OF TRANSIENT BOILING HEAT TRANSFER
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概要
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In this paper, a measurement of pool boiling curve is carried out by solving one dimensional inverse heat conduction problem. The experiments are performed under atmospheric pressure for gold, copper, brass and carbon steel surface. It has been found that boiling curves, including transient transition boiling region, can be traced fairly well using inverse heat conduction solution developed by Monde for data obtained in a simple experiment system. Vapor-liquid behaviors on boiling surface are observed with a high-speed camera. A time correspondence is constructed between the taken video images and the recorded temperature data. Two types of temperature data are recorded for transition boiling region in a heating process (Figs. a, b). Both the types can happen either under steady or transient heating, saturated or subcooled boiling, or either for gold, copper, brass or carbon steel surface. No general law is observed for their occurrence. In other words, the occurrence of the two types is considered being occasional. Their occurring probability is about half to half.[figure] Corresponding to the data in Figs. a and b, two types of transition boiling curves are obtained (Figs. c and d). The second heat flux peak in Fig. d corresponds to the beginning point of the sharp temperature jump in the transition boiling region in Fig. B. For both the curves, a point of inflection is observed on transition boiling region. The reason, which results from an analysis to the recorded video images, is attributed to the full spreading of vapor film over the boiling surface.[figure] Thereby, the transition-boiling region may be divided into two parts : low temperature and high temperature transition-boiling region, respectively. The low temperature transition boiling region possesses characteristics much similar to that of the nucleate boiling, whereas the high temperature transition boiling region is much similar to that of film boiling. The development of low temperature transition boiling is a process of violent seesaw-struggle between nucleate boiling and film boiling. The process is very transient and occasional and may result in a complicate heat transfer characteristics. There may be no such a conclusive curve for the low-temperature transition boiling region. Corresponding to the two kinds of transition boiling region in heating process, two kinds of transition boiling region in cooling process is also observed. Similar results are achieved as that achieved for the heating process. Moreover, boiling curves for steady heating and transient heating, for heating process and cooling process are compared. Boiling curves obtained under different heating rates, cooling rates and subcooling degree are compared.
著者
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Mitsutake Y.
Dept. Mechanical Engineering Saga University
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Liu W.
Dept. of Nuclear Energy System, Japan Atomic Energy Research Institute
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Monde M.
Dept. Mechanical Engineering, Saga University
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Monde M.
Dept. Mechanical Engineering Saga University