The Proceedings of the Thermal Engineering Conference
Online ISSN : 2424-290X
2007
Displaying 51-100 of 197 articles from this issue
  • Masaru NAGATA
    Article type: Article
    Session ID: E111
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Crank shaft end energy conversion efficiencies of a 1300cc engine are presumed by using the data of ECU and GPS at driving on a highway. They are full of 10-35%. However, each mean value of the round trip of the highway is about 30%. There are high values in some malfunctions that exceeded 35%, too, when they have been analyzed in detail. The cause is possibly judged that the engine is always connected with the wheel. For instance, the output powers do not necessarily become the lowest, though the foot parts from the accelerator pedal and the opening angle of the throttle becomes the lowest. As for the classification according to the driving condition, these efficiencies have corresponded to the driving condition.
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  • Toshinori Ogawa, Yasuo Kawaguchi
    Article type: Article
    Session ID: E112
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Although portable electric devices have become increasingly sophisticated and compact, the amount of energy required for their operation has increased and device performance may be restrained by the energy source in the near future. Small, portable distributed power sources with higher energy density than the conventional battery are required. In this research, we focused on the small glow-ignition engine developed for model airplanes. In order to clarify the combustion process, a miniature pressure sensor was built into the cylinder head, and pressure fluctuation was measured. Analysis was conducted to detect cycle-to-cycle variation. The base engine was a commercial glow-ignition four-stroke engine with a swept volume of 4.89cc. Although the nominal output was 368W, the value measured by this research was much lower.
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  • Masashi Iwasaki, Umerujan Sawut, Shinya Yamaguchi, Takeshi Fukawa, Yum ...
    Article type: Article
    Session ID: E113
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The LPG vehicle spread as an alternative fuel vehicle for a petroleum fuel vehicle all over the world. In recent years, Japan actively promotes the remodeling LPG vehicle. In this study, Nikki develops the new LPG prototype vehicle equipped with Nikki advanced technology of multi-point liquid fuel injection system, and investigates fuel consumption rate and exhaust performance of the LPG vehicle. As the 1st step, this paper describes the outline of the LPG fuel pump and the control method. The typical result indicates that the LPG liquid fuel injection system can reduce an amount of electric power consumption than a conventional gasoline system.
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  • Norifumi Mizushima, Susumu Sato, Yasuhiro Ogawa, Toshiro Yamamoto, Ume ...
    Article type: Article
    Session ID: E114
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In this research, for the purpose of promoting energy saving and reduction of CO_2 emissions by popularizing the LPG vehicle in Japan, it is need to improve the fuel consumption, the exhaust emissions and the power of LPG engine more than those of gasoline engine. Liquid fuel injection system will solve these problems. This paper describes that LPG engine with liquid fuel supply system has superiority of the knock-resistant, the fuel consumption and the exhaust emissions to gasoline engine because of combustion characteristic of this fuel.
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  • Yoshifumi YAMAZAKI, Seiji OKAMURA, Hiroki KASUYA, Akira IIJIMA, Hideo ...
    Article type: Article
    Session ID: E115
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Homogeneous Charge Compression Ignition (HCCI) combustion has attracted considerable interest in recent years as a new combustion concept for internal combustion engines. The HCCI combustion process has four issues to be resolved: ignition timing control, slower combustion reaction rate (maximum heat release rate), difficulty expanding stable operation to the high load region and avoidance of knocking. In this study, an attempt was made to overcome these issues by applying exhaust gas recirculation (EGR). EGR rates were varied and examined their respective influence on HCCI combustion.
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  • Jin Kusaka, Yasuhiro Daisho, Shigetomo Sawamoto
    Article type: Article
    Session ID: E116
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    This paper deals with improvements in combustion and exhaust gas emissions in a single cylinder Diesel engine for heavy-duty commercial vehicle applications. A low compression ratio type piston was used to assure suitable ignition delay time during which sufficient air was introduced into the spray plume to suppress NO_x and soot formation. As a result, PCI combustion successfully controls NO and soot emissions simultaneously at 40% load. At 50% load, 70% EGR with 100kPa (gage) supercharging favorably reduce both emissions. In addition, after-injection was also tested to reduce THC and soot emissions at the same load.
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  • Yusuke Shibuya, Jin Kusaka
    Article type: Article
    Session ID: E117
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    A phenomenological soot model coupled with detailed chemistry was introduced into the 3-D CFD code KIVA-3V. The model treats soot formation as four global stages including particle nucleation, surface growth, surface oxidation, and particle coagulation. In paper Particulate Matter Formation process of a Diesel engine under various O_2 concentration conditions were analyzed. As a result, predicted in-cylinder pressure and RHR histories have good agreement with measured ones. It can be predicted qualitative trends of measurement data of soot emission under wide range of O_2 concentration conditions.
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  • Masaaki Okuyama, Toshio Tomimura
    Article type: Article
    Session ID: E121
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    An experimental study has been carried out on the synthesis of carbon nanomaterials using Fe catalyst in methane/air laminar, fuel-rich premixed flames under atmospheric pressure. By placing a pair of porous media in the upstream and downstream sides of the combustion space, excess enthalpy burning was applied to the methane/air mixture. We have investigated effects of reaction time on nanomaterials growth. As s result, carbon nanomaterials with a diameter of from 20 to 50nm have been synthesized in region near the downstream side of the porous medium.
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  • Akira Nakajima, Tsubasa Shimizu, Masahiko Shibahara, Nilson Kunioshi
    Article type: Article
    Session ID: E122
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The combustion synthesis method is actually used in the industrial mass production process of fullerenes. However, the fullerene formation mechanism from PAHs in a toluene and oxygen premixed flame has not been clarified yet. In the present research, fullerene contents and PAH contents in soot samples were investigated to clarify the formation mechanism of PAHs and fullerenes when the burner structure was changed in two kinds. In the case of the burner B the fullerene contents decreased remarkably and PAHs contents increased in comparison with the case of the burner A. These results showed that the heat supply and the temperature in the chamber were important factors in the fullerene formation mechanism in a flame.
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  • Yong Fan, Yuji Suzuki, Nobuhide Kasagi
    Article type: Article
    Session ID: E123
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    This paper presents (1) the development of optical measurement system of near-wall OH^* concentration in order to investigate the flame quenching mechanism in ultra-thin chamber; and (2) observation and analysis of premixed CH_4/Air flame propagation and quenching in three quartz combustors with chamber depth of 0.7mm, 1.0mm and 1.5mm, respectively. It is found that the quenching distance for heated quartz wall can be smaller than 0.7mm, and is dependant on the wall temperature. Flammability limits are obtained for different equivalence ratios and mixture velocities.
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  • Satoshi Yoshida, Satoshi Someya, Koji Okamoto
    Article type: Article
    Session ID: E131
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The interaction phenomena of one drop impinging on a hot surface at around Leidenfrost temperature have been experimentally investigated. In this experiment, especially the effect of released position on the droplet behavior was analyzed with high speed camera at 5000 frame per second. A large influence on the Leidenfrost phenomena of hastelloy and several materials was summarized. It has been observed that with increasing the droplet falling height, evaporation time of the droplet was decreased. At a certain droplet falling height and surface temperature, a droplet jet extraction phenomenon has been observed. Because of the vaporization at the first impact of the droplet bottom, the vaporization pressure attack top of the droplet, then the jet has been extracted from top of the droplet. At higher droplet falling distance and temperature, the jet extraction phenomenon does not occur, since the droplet has higher impact moment.
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  • Shizuo Saitoh, Takamoto Saitoh
    Article type: Article
    Session ID: E132
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In order to study the mechanism of the vapor explosion, we focused on the behavior of a falling water-drop and the force produced by its contact with hot molten metal (Fuji Metal No. 25, or Zinc). The phenomena are classified into the 3 types. Type A corresponds to the vapor explosion, accompanying large sound and large impact. Type B does to the phenomena of smaller impact under the same condition with Type A. The impact of Type C is below 10% of Type A. The water penetration into the molten metal plays an important role for the vapor explosion, relating to the temperature of metal and water-drop, and the fall height.
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  • Yusuke Kizaki, Ichiro Ueno
    Article type: Article
    Session ID: E133
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    An experimental study on the dynamics of the fluid in the vicinity of the boundary line of three phases was carried out. The apparent boundary of solid-liquid-gas interface is so-called 'macroscopic contact line.' It has been known over about a century there exists a wafer-thin liquid film ahead the macroscopic contact line. This wafer-thin liquid film has been known as the precursor film. The present authors paid their special attention to the existing length of the precursor film ahead traveling droplet on a solid substrate with non-uniform temperature distribution. The length of the precursor film was detected by applying a conventional laser interferometer, and the position of the macroscopic contact line was grasped by simultaneous observation with a white light source. The present manuscript indicates the precursor film length is strongly affected by the temperature gradient of the solid surface.
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  • Sutopo P. Fitri, Katsuya Fukuda, Qiusheng Liu
    Article type: Article
    Session ID: E134
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The surface superheats at incipient boiling and critical heat flux (CHF) due to transient heat inputs have been measured on horizontal gold cylinder surface with a diameter of 1.0mm. Measurements were made under a wide range of pressures and subcoolings ranged from atmospheric up to 1082kPa and from saturated condition up to 140K, respectively. It was observed in high subcooling that the incipient boiling surface superheat, ΔT_i, is higher than the CHF surface superheat, ΔT_c, The ΔT_i and ΔT_c for direct transition and semi-direct transition processes show an almost constant value. It was found also that the incipient boiling and CHF surface superheats are dependent on subcooling.
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  • Ryoji Imai, [in Japanese]
    Article type: Article
    Session ID: E135
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Our purpose is to develop miniaturized heat rejection system that can dissipate more than 100W/cm^2. In the evaporator, thin liquid film vaporization which can dissipate very high heat flux, was utilized. The liquid film is stabilized in micro-channels by capillary forces. The micro-channels are fabricated by chemical etching on copper plate. Also miniaturized condenser which utilized droplet condensation was tested. Droplets were produced on a cooled plate covered by non-wetting coating. After we built a heat rejection system constructed by above mentioned evaporator and condenser, influence of heat flux, coolant flow rate, and inlet temperature on the temperature of the heater element were investigated. Water is used as working fluid. Heat flux of 100W/cm^2 could be achieved for water inlet temperature in flow rate of 3.0mL/min. The temperature of the heater element is kept constant at about 120℃. The measured pressure drop is less than 1000Pa.
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  • Satoshi Hada, Kenichiro Takeishi, Seijiro Mori, Sigeaki Nuta
    Article type: Article
    Session ID: F111
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    This paper describes the results of experimental and numerical studies about the heat transfer and flow dynamics in the leading edge region on a symmetric airfoil. The effect of boundary layer thickenss was investigated. Local heat transfer coefficient is measured by naphthalene sublimation method. By using a Particle Image Velocimetry (PIV), instantaneous flow field data near the junction of an airfoil and endwall have been studied. Furthermore, the experimental results are compared to the computational results solved by Detached Eddy Simulation (DES). The value of primary peak is unchanged as the boundary layer thickness is changed from 20 to 40mm.
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  • Hitoshi Matsushima, Hiroshi Fukuda
    Article type: Article
    Session ID: F112
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Measurement of fan performance characteristics and sound pressure level of tandem fans is performed. Measured maximum static pressure and maximum volume flow rate of tandem fans are 1.5 and 1.1 times of single fan, respectively. These values are almost constant for fan spacing of 0mm to 70mm. Rotational speed of tandem fans at normal operation condition is almost linier to the input voltage of fan, and that is independent of volume flow rate. When one of the tandem fans is stopped, rotational speed of stopped fan is almost proportional to the volume flow rate produced by the other operating fan. Sound pressure level of tandem fans is reduced by 3 to 5dB by changing fan spacing from 0mm to 70mm.
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  • Masanori MATSUO
    Article type: Article
    Session ID: F113
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The objective of this paper is to design development sliding thrust bearings for screw compressors. The tests were carried out to obtain the data for bearing performance operating at an actual condition of refrigerant-blended lubricant. The thrust bearing used here is a groove type bearing with grooves on the runner and plane surface for the stationary side. The grooves are combination of spiral shape on outer side and radial shape on inner side in order to make reverse rotation possible. This bearing is named "The Ribbon Type Bearing", furthermore, the lubricating system of injection was adopted for starting torque decrease of the plain Bearing. "The Ribbon Type Bearing" is intended to achieve higher load capacity and lower bearing loss by the pumping effect and cooling effect of the both types of grooves in comparison with a conventional spiral groove bearings. The tests were carried out using pure lubricant and refrigerant blended lubricant containing refrigerant quantity of 6wt%, 10wt% and 44wt%. The operating conditions were 2500rpm rotational speed and 377kg bearing load. At that condition using 44% refrigerant blended lubricant, bearing temperature was about 74℃. The potential of the ribbon type bearings were well demonstrated.
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  • Takahiro Ohmura, Yasuo Ito, Isami Abe, Junichi Nyumura, Makio Naito, H ...
    Article type: Article
    Session ID: F114
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    We have developed a nanoporous composite thermal insulation that consists of fumed silica (SiO_2). This insulation has ultra low thermal conductivity, because the mean free pass of air included in the insulation is limited by the mean size of the pore inside. However, the ways of jointing thermal insulations each other become serious problems, when setting up them on the buildings, furnaces, houses, etc. Especially, when using the developed thermal insulation, a large amount of heat should be lost from the jointing part. Because adhesives, whose thermal conductivity is larger than one of the developed thermal insulation, are used for jointing each surfaces of the specimen. Therefore, it is very important to know the thermal properties of the jointing part of the specimen. Here, it was shown that no adhesive in the jointing part was more proper, when using the developed thermal insulation
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  • Naoya KINOSHITA, Hiroyuki IYOTA, Nobuya NISHIMURA, Masamichi YOSHIDA
    Article type: Article
    Session ID: F115
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Convective drying of glass beads packed beds containing NaCl aqueous solution, under a wide range of gas temperature and humidity (room air to superheated steam), and the relationship between surface salt deposition, material temperature and moisture content changes, was investigated. In the case of high gas temperature and low humidity, salt deposition was evenly distributed across the bed surface, and salt crystallization was observed to begin at high moisture content. Drying proceeded over two stages of distinctly different drying rates. At high humidity, salt crystallization was observed to begin at lower moisture content, and was unevenly distributed across the bed surface.
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  • Yasuhiro SHIMAZAKI, Shinichi KINOSHITA, Atsumasa YOSHIDA
    Article type: Article
    Session ID: F116
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    There is increasing concern about the health effects of the severe thermal environment in urban area. Because of these, it is important to estimate the thermal comfort for environmental improvements and designs. The heat and the moisture transfer coefficients on clothing material are measured in various conditions, because the clothing material is one of major factors which influence the human thermal comfort. In the experiment, the authors find out the effectiveness of the velocity of wind and the thickness of clothing material on the heat and the moisture transfer properties.
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  • Nobuhiro HIMENO, Shigeru TERATANI, Yasuo MIZUSHIMA
    Article type: Article
    Session ID: F117
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The present study proposes a new shower cleaning system which can remove not only small particles but also environmental pollutant gases and bad-smelling components from an exhaust gas. A fundamental research was experimentally conducted on the performance of the shower cleaning system by using "Silica Sand" (particle diameter: 27-31μm) and "Fly Ash" (particle diameter: 4.8-5.7μm) as test particles. In the case of "Silica Sand" the conventional shower cleaning system removed the particles almost completely, but for fine particles like "Fly Ash" the cleaning was not attained completely, which suggests the effectiveness of the "direct contact condensation effect" proposed in the present study.
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  • Takenori Iio, Ryousuke Matsumoto, Mamoru Ozawa, Toshikazu Takemori, Yo ...
    Article type: Article
    Session ID: F121
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The purpose of this study is R & D of micro superheated-steam generator having 90cc/min evaporation rate at 250℃ superheated steam. The micro steam generator should be within 200×200×150mm including the burner, the micro boiler and the combustion chamber to be equipped into the household cooking stove. Therefore, the air-preheating and the gas re-circulation are applied to the micro steam generator to achieve complete combustion in limited space. Thus were achieved downsizing of combustor, low-NO_x combustion with high efficiency.
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  • Hirotsugu Miyamoto, Ryosuke Matsumoto, Mamoru Ozawa, Masashi Katsuki
    Article type: Article
    Session ID: F122
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The purpose of this study is development of water tube boiler in tubular flame. The single water tube is inserted into the center of the tubular flame for using as a boiler. The flow field was measured by flow visualization in the water. The flow patterns were classified into three patterns; the forward flow, the stable reverse flow and the disturbed reverse flow. The axial velocity distribution with the water tube has the same distribution without the water tube. The combustion tests were carried out. The tubular flame was formed in the combustion chamber with the water tube, however, the flame became unstable due to the excess cooling by the water tube.
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  • Hideaki kuwabara, Makoto Nishimura, Masaki matsukuma, Takayoshi Matsui
    Article type: Article
    Session ID: F123
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The minor scale steam plant is widely prevalent in the industrial world. However, change of steam flow, a small amount of steam, and low-pressure steam prevent energy saving technology in spreading minor scale steam plants. From such a reason, screw type small steam generator was developed, it was called micro steam energy generator. This machine enables effective use of steam in a minor scale steam plant and promotes the further energy saving and CO2 reduction. The advantage of this machine can control the downstream pressure, equivalent to a reducing valve, and generate the power in the wide range of steam flow. Furthermore, 60% or more of high efficiency was realized in the 100kW class steam turbine. The test result of this machine is shown in this paper.
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  • Yukio FUJIWARA, Junichi FUJIYAMA, Hitoshi ASANO, Kazuhiro KIMURA
    Article type: Article
    Session ID: F124
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Recently, the reduction in CO_2 emissions is taken up as a worldwide problem. For household gas water heater, improvement in the thermal efficiency by latent heat recovery from the exhaust gas is required. In this report, a compact vertical tube bank heat exchanger was designed by a numerical analysis based on analogy of heat and mass transfer. It is expected that the designed heat exchanger improve the HHV based thermal efficiency 12.8%. Two prototypes using SUS smooth tubes with 8 and 6mm O.D. had been manufactured and tested.
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  • Fumiyoshi KIMURA, Toshihiko TAKETANI, Kenzo KITAMURA
    Article type: Article
    Session ID: F131
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Experimental investigation have been performed on natural convection of air over an upward facing, inclined, heated plate. The special interests were paid to the turbulent transition and the heat transfer characteristics. The flow field over the plate was visualized with smoke. The results showed that the longitudinal vortices appear over the plate when the inclination angle θ<72° from horizontal, and they become a trigger to the turbulent transition. The local heat transfer coefficients were also measured with the angles 0°<θ<90°. The results showed that the local Nusselt numbers of the laminar flow depend on the inclination angles, while those of the turbulent flow are consistent with the angles.
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  • Tadasuke Matsuno, Toshihiro TSUJI, Yasushi KAJITA
    Article type: Article
    Session ID: F132
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    An experimental study on heat transfer enhancement for a laminar natural convection boundary layer along a vertical flat plate has been performed by inserting flat plates set in array at fixed intervals (split heat transfer promoter) in the spanwise direction of the boundary layer. As a result, the local heat transfer rates in the downstream region of the promoter substantially increase. By visualizing flows with smoke and laser sheet, it is found that the increase in heat transfer rates is mainly caused by the longitudinal vortex motions formed with the split heat transfer promoter. Thus, placing several columns of split heat transfer promoters in the flow direction may result in heat transfer enhancement in the wide range of the laminar natural convection boundary layers.
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  • Mitsuo HIGANO, Muneo FUTAMURA, Koki SATO, Masato AKAMATSU
    Article type: Article
    Session ID: F133
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The magnetothermal wind is induced by the magnetic (Kelvin) force in two coaxial circular pipes with both thermal and magnetic gradients. When the one-turn electric coil as a source of the magnetic (Kelvin) force is placed at the upper end of the heated region of the inner pipe, the flow direction of the magnetothermal wind changes from the upward flow to downward flow with the increase of magnetic strength. The present study noticed the reverse flow of a magnetothermal wind under various Rayleigh numbers. Our numerical results showed that the critical magnetic strength caused the reverse flow was almost independent of Rayleigh number.
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  • Hajime Nakamura
    Article type: Article
    Session ID: F134
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Time-space distribution of convective heat transfer behind a backward-facing step was measured in order to investigate the mechanisms of the heat transfer caused by the flow separation and reattachment. This measurement was achieved by using a high-speed infrared thermograph which measured temperature fluctuation on a thin conductive-film heated electrically. As a result, the spatio-temporal behavior of the heat transfer, which was reflected by the vortical structure formed in the near-wall region, was clearly revealed.
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  • Yoshinobu Nishii, Yuta Sasaki, Kyoji Inaoka, Mamoru Senda
    Article type: Article
    Session ID: F135
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Flow modification downstream of a backward-facing step has been tried to achieve heat transfer enhancement by introducing two kinds of devices, a triangle prism rib and electromagnetic actuators, on the step edge. The triangle prism rib attached to the side-wall corner makes the downward flow inclined and generates a circle-like fluid motion behind it. Because such kind of flow modifications work effective in reducing the flow re-circulation caused behind the step, large heat transfer recovery is obtained near the side-wall. This advantage of the triangle rib remains effective when the flap actuations are imposed. Thus, the large-scale unsteady vortex intensively reduces the flow re-circulation, the triangle rib with flap actuations attains the largest heat transfer recovery behind the step.
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  • Yasuyuki Yokono, Katsumi Hisano, Kenji Hirohata
    Article type: Article
    Session ID: G111
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In order to utilize numerical analysis techniques in the actual design process, not only the numerical analysis techniques themselves, but the procedures for applying those techniques in the design, were examined According to the stage of a design, the example of application of numerical analysis and visualization in the design of an electric equipment was divided into the system performance analysis which drops a product concept on a system function, the layout analysis which determines a system function to a part layout, and the parameter analysis which determines the design parameter of each part. The progress of the numerical technology for product planning is expected. The product development process requires not only numerical simulation based on physics but also statistical approach.
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  • Yutaka Shinki, Shuhji Ubemoto, Nobuyuki Kishimoto, Daisuke Takeda, Yas ...
    Article type: Article
    Session ID: G112
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The thermal issue is critical in development of Mobile Phones, which tend to be downsized and consumes more power. We use thermal simulation to estimate thermal behavior, and decide the design of product. To be put into practice, thermal simulation must be done in short time and bring a necessary and sufficient accurate result. In this paper, we talk about equivalent thermal conductivity of print circuit boards under electronic components and boundary conditions of heat transfer to human fingers/palm.
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  • Katsuhiro KOIZUMI, Masaru ISHIZUKA, Shinji NAKAGAWA
    Article type: Article
    Session ID: G113
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In the design process of electronic equipment, the early estimation of component temperature is of great importance. In order to predict the lifetime of equipments, the electrolytic capacitor is one of the most important components in thermal analysis of electronic equipment. To predict the component and system temperature, the thermal flow simulation technique has been applying to thermal design in the development phase of electronic equipment. In this study, we investigate the compact thermal modeling method of electrolytic capacitors. This paper describes the result of experiment of the confirmation of the main thermal path of the electrolytic capacitor on the printed circuit board as the basic data for the investigation of modeling method. In addition, X-ray structure analysis of three types of electrolytic capacitor was conducted.
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  • Tomoyuki Hatakeyama, Kazuyoshi Fushinobu, Ken Okazaki
    Article type: Article
    Session ID: G114
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Nowadays, CMOS devices are widely used in LSIs. For higher degree of integration of semiconductor devices, the distance between nMOS and pMOS in CMOS must be decreased. However, in bulk CMOS, nMOS and pMOS are not completely insulated. Therefore, decrease of the distance between nMOS and pMOS in bulk CMOS leads to the interaction between two MOSFETs. To decrease the distance between two MOSFETs in bulk CMOS, the interaction phenomena between nMOS and pMOS in bulk CMOS should be investigated. In this research, we report our experimental work of CMOS inverter. We fabricated CMOS inverters, in which the distance between two MOSFET is changed. We measured the drain current under several voltage conditions. The experimental results show, in the case that the distance between two MOSFET in bulk CMOS is decreased, the current of each MOSFET is dependent only on drain voltage and we cannot control the current by the gate voltage.
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  • Ryoji IMAI, Yasushi NISHINO, Shinji NAKAGAWA, Masaru ISHIZUKA
    Article type: Article
    Session ID: G115
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The natural cooling capacity and flow field in relatively small electronic equipment were studied. A channel model was used as an experimental model of electronic equipment. The channel model has two vertical copper walls modeling the printed circuit boards and two transparent walls modeling the casing walls. The width between the copper walls was varied from 10mm to 15mm. Velocity distributions in the channel were quantitatively measured using a particle image velocimetry (PIV). Thermal resistance is strongly influenced by the ratio of heating energy at the walls. Velocity distributions become asymmetric depending on the channel width and the heating energy ratio.
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  • Masao Fujii
    Article type: Article
    Session ID: G116
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Two rectangular block-like elements as an electronic module are positioned in a parallel-walled channel and cooled by forced convection airflow. A metal plate with holes as a barrier protrudes above the plane of the modules, which is intended to function as a cover for protecting them from mechanical or electromagnetic damage. Per-module heat transfer coefficients in the presence of barriers of various height, H and distance, L between the module and the barrier were measured. In the presence of the barrier with holes, the heat transfer coefficient at two modules is rapidly diminished. Nusselt numbers are correlated as a function of Reynolds number and H/L.
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  • J.Y. Shim, S. Tsushima, S. Hirai
    Article type: Article
    Session ID: G121
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In this study, the membrane degradation experiments were conducted under open circuit voltage condition with high purity H_2 and O_2 under dry and fully humidified conditions to investigate which side of the membrane is severely deteriorated. For this experiments, the laminated bi-layer MEA was used to delineate the division of the membrane; anode and cathode. Based on the SEM images, it is figured out that the anode side of membrane is severely deteriorated than the cathode side of membrane under both gas supplying conditions. It is also found that the membrane under dry conditions was more deteriorated than humidified conditions.
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  • Takashi SASABE, Keigo YOSHIDA, Jin KUSAKA, Norio KUBO, Koichiro AOTANI
    Article type: Article
    Session ID: G122
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    An experimental and numerical study was carried out to investigate the effect of cathode flow distributor geometry on the performance of PEMFCs under low oxygen concentration operations. The results shows oxygen concentration and current density are not uniform between under the ribs and under the channels with the straight flow fields. In addition, numerical study shows the importance of the understanding of liquid water transport phenomena in MEA.
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  • Hiroshi Takahashi, Shigeyuki Sekigutci, Takemi Chikahisa
    Article type: Article
    Session ID: G123
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The authors developed PEM fuel cells consisting of thin separators with the thickness of 0.8mm. The paper investigates the channel depth in the separators on cell performance and the pressure losses. The result shows that the pressure loss increases inversely proportional to the third power of the channel depth and it increases significantly for the channel depth less than 0.2mm. Compared with the channel depth of 0.5mm, the channel with 0.3mm depth showed better cell-voltage-performance: voltage fluctuation was smaller with 0.3mm depth and the cell voltage itself was higher than the 0.5mm channel particularly at higher current density conditions. This result indicates that specific value of pressure loss or gas velocity is necessary for the cell to supply cathode gas to the catalytic layer without flooding. This suggests the possibility of straight channels with thin depth to give good performance.
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  • Hirofumi Tanigawa, Yuki Miyazaki, Takaharu Tsuruta
    Article type: Article
    Session ID: G131
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Water management is the most important subject in the development of the Polymer Electrolyte Fuel Cells (PEFC) with high performance and high reliability. We have developed a three-dimensional simulator by using the Lattice Gas Automaton (LGA) method to analyze the transport phenomena in the gas diffusion layer (GDL) as well as in the separator channel. It is found that the three-dimensional simulator enable us to examine the liquid water distribution inside the Polymer Electrolyte Fuel Cells.
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  • Kazuhiko Kudo, Akiyoshi Kuroda, Takashi Yamaguchi, Shougo Takeoka, Hit ...
    Article type: Article
    Session ID: G132
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Cathode side gas diffusion layer (GDL) is modeled considering the behavior of water vapor, liquid water and oxygen diffusion. The model is consists of many parallel hydrophobic pores. By using the model, the current density at which water vapor starts to condense at catalyst side GDL is calculated for various values of GDL porosity and channel air humidity. As the results following results are obtained: the increase in the GDL porosity raises the current density at condensation initiation, and the increase in the supply air humidity reduces the current density.
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  • Yutaka TASAKI, Shixue WANG, Yasushi ICHIKAWA, Denis. Kramer, Pierre. B ...
    Article type: Article
    Session ID: G133
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    The mass transfer characteristics of gas diffusion layer (GDL) are closely related to cell performance in PEFC. In this study, the oxygen diffusivity of paper and cloth type porous media used generally as GDL with respect to its liquid water content were measured by using an experimental apparatus consist of oxygen sensor based on Galvanic battery, and liquid water distribution in each porous medium is visualized by using Neutron Radiography. The relationship between oxygen diffusivity and liquid water distribution has been studied for paper and cloth type GDL, respectively.
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  • Takeshi Murakami, Kosuke Nishida, Shohji Tsushima, Shuichiro Hirai
    Article type: Article
    Session ID: G134
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Water management in a cathode electrode of polymer electrolyte fuel cell (PEFC) is essential for high performance operation. When the open pores inside the GDL are filled with liquid water, oxygen cannot be sufficiently supplied to reaction sites. This phenomenon known as 'water flooding' is critical to achieve high power density. In this study, we experimentally and quantitatively investigate water accumulation inside a cathode electrode of PEFC, and show the effect of it on the characteristic of cell voltage. It was found that the voltage drop due to water flooding is greatly affected by current density and oxygen partial pressure.
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  • Hirokazu Ito, Kosuke Nishida, Shohji Tsushima, Shuichiro Hirai
    Article type: Article
    Session ID: G135
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    During cold startup of polymer electrolyte fuel cell (PEFC), water freezing in a cathode porous electrode is a critical barrier to achieve high power density, because ice particles in the catalyst layer (CL) and gas diffusion layer (GDL) block oxygen transport to the active reaction sites. In this study, we investigate water behavior inside a cathode electrode of PEFC at low temperature operations using an optical diagnostic, and show the effect of the mechanism of water freezing on the characteristic of cell voltage. The results showed that ice formation in cathode electrode during cold startup is largely affected by GDL structure.
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  • Article type: Appendix
    Pages App6-
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
  • Yasuaki SHIINA, Hiromichi OGI, Terumi INAGAKI
    Article type: Article
    Session ID: C211
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    Effect of non-uniform heat transfer coefficient on melting of solid phase filled in horizontal circular cylinders has been studied by numerical analysis. Conduction and convection analyses were performed under the condition of uniform and non-uniform heat transfer coefficient. The numerical results were compared with the experimental results. For small Rayleigh number in the liquid phase, melting process is dominated by thermal convection. With increase in Rayleigh number, natural convection dominates the heat transfer and the effect of non-uniform heat transfer coefficient on melting process is reduced..
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  • Yuya DAIKOKU, Koji MATSUMOTO
    Article type: Article
    Session ID: C212
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    In this study, temperature dependency of adhesion force per unit area corresponding to shearing stress to remove ice from a cooling solid surface (adhesion stress) was measured, varying the material. Moreover, temperature dependency of surface energy was also measured. And then, a relationship between both temperature dependences was clarified. Additionally, for the copper, which was a unique, influences of the composition and thickness of a oxide layer on adhesion stress were discussed. Moreover, influences of irradiations of ultraviolet wave and atmospheric plasma on adhesion stress were also discussed.
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  • Kengo Matsumoto, Koji Matsumoto
    Article type: Article
    Session ID: C213
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    As a thermal storage material in a dynamic ice storage, a W/O emulsion with higher water content consisting of water-silicon oil mixture with a little amino group modified silicone oil additive was formed. Use of the emulsion was possible to form ice slurry stably without ice adhesion to a cooling wall because of its structural feature. In this paper, validity of a new W/O emulsion proposed as a thermal storage material was discussed. And then, it was found that use of the W/O emulsion was also possible to form ice slurry without ice adhesion, additionally, it had new functions that propagation rate of supercooling dissolution and ice formation rate were faster than the conventional W/O emulsion.
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  • Yukio TADA, Akira TAKIMOTO, Haruki TUKAMOTO, Hajime ONISHI
    Article type: Article
    Session ID: C214
    Published: November 23, 2007
    Released on J-STAGE: June 19, 2017
    CONFERENCE PROCEEDINGS FREE ACCESS
    A method to actively controlling crystallization is one of promising technique for cryopreservation. The object of this paper is to study the effects of ultrasonic irradiation on ice formation during freezing of biological materials. In the experiments, agar gel was frozen under irradiation of ultrasound at frequency of 28kHz. It was found that ultrasound released the supercooling states, and reduced ice crystal size in the tissue. However, the fattning of ice crystal was observed by irradiation of higher ultrasonic power, since the cooling rate was reduced due to absorption of the ultrasonic wave. The mechanism of sonocrystallization in biological tissue was discussed in relation to ultrasonic power and tissue size.
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