Thermal Science and Engineering
Online ISSN : 1882-2592
Print ISSN : 0918-9963
ISSN-L : 0918-9963
Volume 16 , Issue 4
Showing 1-6 articles out of 6 articles from the selected issue
  • Yasuharu MIYAMOTO, Junji KAMOSHIDA, Jun YAMADA
    2008 Volume 16 Issue 4 Pages 113-120
    Published: 2008
    Released: April 23, 2009
    JOURNALS FREE ACCESS
    To clarify the mechanism of Marangoni drying used for rinsing and drying process in semiconductor manufacturing industries, the concentration of organic component in the meniscus during organic vapor dissolution have been measured with a micro-optical concentration sensor and have been visualized by phenol red reagent when ammonia gas was used as organic gas. It is clarified that a concentration gradient that induces Marangoni force appears in the meniscus during the vapor dissolution and the three phases line is pulled down by the Marangoni force. In addition, behavior of three phases line has been observed, while the wafer is drawn up, by using a CCD camera. This reveals that the liquid film separates from the meniscus and remains on the wafer when a wave hits on the wafer.
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  • Yoshito TANAKA, Yoshifumi TSURU, Masato YOSHINO, Tetsuo HIRATA
    2008 Volume 16 Issue 4 Pages 121-130
    Published: 2008
    Released: April 23, 2009
    JOURNALS FREE ACCESS
    The lattice kinetic scheme based on the lattice Boltzmann method (LBM) for two-phase fluid flows with large density differences is applied to the Rayleigh-Taylor instability problem with heat transfer. First, the isothermal simulation is carried out, and the growth rate of the instability against an infinitesimal disturbance is investigated. The results are in good agreement with the theoretical prediction for different values of the interfacial tension. Next, the simulation of thermal fluid flow is performed to obtain the flow fields and temperature distributions under various thermal conditions. From these results, it is found that the flow characteristics are different from the corresponding isothermal ones owing to the buoyancy effects by heat transfer through the interface.
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  • Yoshiaki HATTORI, Shinobu MUKASA, Shinfuku NOMURA, Hiromichi TOYOTA
    2008 Volume 16 Issue 4 Pages 131-137
    Published: 2008
    Released: April 23, 2009
    JOURNALS FREE ACCESS
    “In-liquid plasma” is generated inside the bubbles on the tip of an electrode by applying microwave radiation from the electrode. The in-liquid plasma on the tip of an electrode consists of a plasma generation region, vapor phase, bubble interface, and liquid phase. The growth of the bubble, including the plasma, in n-dodecane was observed using a high-speed camera. This was done because the pressure and the temperature surrounding the plasma needed to be clarified for utilizing it in such processes as chemical vapor deposition. The dependence of the bubble growth on the vessel pressure and on the microwave power was clarified, and the internal pressure of the bubbles was calculated by substituting the approximation curve of the observed bubble diameter in the Rayleigh-Plesset equation. The bubbles grow not continuously but intermittently as the plasma region expands and contracts. The growth of the bubbles increases with increase in the microwave power or decrease in the vessel pressure. The value of the internal pressure of the bubbles peaks between 200 and 600 hPa, it increases as the microwave power increases, and the effect of the vessel pressure on it is small. In addition, we measured the temperature surrounding the plasma using a thermocouple. The temperature can be measured vertically from the vapor phase to the liquid phase by moving the thermocouple in that direction. The point where the temperature measurable by the thermocouple reaches a maximum moves away from the tip of the electrode as the microwave power increases. The maximum temperature reaches the approximate saturation temperature of the liquid.
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  • Masafumi NAKAGAWA, Hiroyuki CHINO, Atsushi HARADA
    2008 Volume 16 Issue 4 Pages 139-145
    Published: 2008
    Released: April 23, 2009
    JOURNALS FREE ACCESS
    CO2 has been extensively researched as a refrigerant for refrigeration and air conditioning systems because of its environment-friendly, nontoxic and nonflammable characteristics. In order to increase the COP in using CO2, a new refrigeration system that uses the two-phase flow ejector to recover the expansion energy at the expansion valve is needed. Understanding the characteristics of both waves in two-phase flow is very important in designing the ejector. The purpose of the present study is to elucidate the experimentally determined characteristics of expansion waves of CO2 at the outlet of the two-phase flow nozzle. High-pressure blowdown experiment of CO2 had been carried out. The measured decompression curves of the expansion waves were varied by changing the inlet temperature and pressure and the back pressure of the nozzle. The experimental decompression profiles after the nozzle were more rapidly decreasing than those predicted using Isentropic Homogenous Equilibrium. As the inlet temperature became low, the pressure profiles inside the nozzle and of expansion waves after the nozzle decreased far from the predicted profiles. Almost flat pressure profiles, which were increasing in length with decreasing inlet temperature, also appeared right after the nozzle. Expansion waves could reach the opposite wall after those flat profiles because the flow was supersonic. Considerably, the effective length of expansion region after the nozzle was also becoming longer with decreasing inlet temperature. The lengthening of the expansion region of CO2 for low inlet temperature was the same as that observed in the experimental pressure profiles of steam expansion waves.
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  • Takashi FUKUE, Takafumi YOSHIMOTO, Masaru ISHIZUKA, Shinji NAKAGAWA
    2008 Volume 16 Issue 4 Pages 147-156
    Published: 2008
    Released: April 23, 2009
    JOURNALS FREE ACCESS
    This paper describes the effects of frame and inlet sizes of an electronic casing on the cooling fan performance. The performance of air-cooling fans is defined by their P-Q characteristics. Recent studies report that P-Q curves of cooling fans depend considerably on their operational environments. It is impossible for accurate CFD (Computational Fluid Dynamics) analyses to be performed on the thermal design of electronic equipments, including fans. In this study, we measured a fan performance in some frames and explored effects of environment for their P-Q characteristics, especially effects from area of frame and cooling air inlet sizes. From experimental results, it was found that the fan P-Q characteristics, especially flow rate were affected strongly by inlet sizes.
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  • Qiusheng LIU, Katsuya FUKUDA, Makoto SHIBAHARA
    2008 Volume 16 Issue 4 Pages 157-162
    Published: 2008
    Released: April 23, 2009
    JOURNALS FREE ACCESS
    Forced convection transient heat transfer for helium gas at various periods of exponential increase of heat input to a horizontal cylinder and a plate (ribbon) was experimentally and theoretically studied. In the experimental studies, the authors measured heat flux, surface temperature, and transient heat transfer coefficients for forced convection flow of helium gas over a horizontal cylinder and a plate (ribbon) under wide experimental conditions. Empirical correlations for quasi-steady-state heat transfer and transient heat transfer were obtained based on the experimental data. In the theoretical study, transient heat transfer was numerically solved based on a turbulent flow model. The values of numerical solution for surface temperature and heat flux were compared and discussed with authors′ experimental data.
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