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Satoshi Wada, Noboru Koike, Tadashi Shudo, Kenya Kurokawa
Session ID: B232
Published: 2016
Released on J-STAGE: June 19, 2017
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When lithium-ion batteries are used long time by high temperature, their battery capacities may decay. Therefore, we developed lithium-ion battery modules to which bottom water-cooling is applied in order to reduce the rise in heat of batteries. As a result of evaluating the rise in heat of lithium-ion battery module, it was proved that the rise in heat would be less than 15K in 6C charge-discharge cycle. Heat resistance of lithium-ion battery module became low so that Reynolds number was high, but it turned out that the amount of change is a tendency which becomes small gradually. The most important thing to improve performance of bottom water-cooling system is structure which carries the heat from the inside of batteries efficiently.
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Ryoga Nakauchi, Yuya Maeda, Kosuke Nishida, Toyofumi Umekawa, Masahiro ...
Session ID: B233
Published: 2016
Released on J-STAGE: June 19, 2017
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To improve the performance of polymer electrolyte fuel cells (PEFCs), it is necessary to establish diagnostic techniques for understanding mass transport phenomena inside operating fuel cell. We focus on a fiber-optic gas sensing technique based on tunable diode laser absorption spectroscopy (TDLAS), and apply it to the measurement of water concentration in narrow channel of PEFC. In this study, a transmission/reception integrated fiber-optic probe was first developed, and the absorption spectra of water vapor in a simulated flow cell were detected by using the fiber-optic TDLAS sensor. Furthermore, the validity of TDLAS measurements was verified by the numerical analysis of absorption spectra based on the HITRAN database.
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Shodai Sunami, Tatuya Muto, Kosuke Nishida
Session ID: B234
Published: 2016
Released on J-STAGE: June 19, 2017
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Enzymatic biofuel cell is expected to be a promising power source for implantable and wearable medical devices because of its compact design and biocompatibility. Especially, lactate biofuel cell has attracted much attention as a wearable power source, due to its ability to generate power using sweat from human body. In this study, we fabricated several enzyme-immobilized electrodes for lactate biofuel cell, and investigated the effect of immobilization method of enzyme and mediator on the electrode reaction characteristics at the bioanode based on cyclic volutammetry. It was found that the mixing process of enzyme and mediator solutions unfortunately causes the denaturation and deactivation of enzyme.
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(The effect of inlet quality)
Masayoshi Nakamura, Yusuke Kawabata, Takeshi Yasunaga, Yasuyuki Ikegam ...
Session ID: C111
Published: 2016
Released on J-STAGE: June 19, 2017
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The low-grade thermal energy conversion (LTEC) can generate electricity using so small temperature difference between heat sources compared with conventional power plant that the optimized heat exchangers are required. In LTEC the plate heat exchangers are adopted. The ultimate purpose this research is to optimize the plate surface geometry for LTEC. As a first step, in this paper, the visualization of evaporation and condensation inside of whole PHE with the variable various inlet quality of working fluid (HFE7000). Furthermore, the effects of inlet quality of working fluid on the flow pattern were investigated.
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Sami Mutair, Takeshi Yasunaga, Takafumi Morisaki, Yasuyuki Ikegami
Session ID: C112
Published: 2016
Released on J-STAGE: June 19, 2017
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Enhancement of heat transfer performance results in an increase of the overall system efficiency and reflects on the process economics. This study comprises numerical analysis using Computational Fluid Dynamics (CFD) methods and reports on the results of a novel technique for enhancement of the heat exchanger performance by means of insertion of air bubbles into the flow in herringbone-type Plate heat Exchanger (PHE). Initial results revealed that air containment in water flow at a given mass flux doesn't always result in heat transfer degradation, yet there exist a certain air quality at which the overall heat transfer coefficient is seen to increase. The overall heat transfer coefficient is seen to increase by about 34~38% with insertion of air at a rate of 50 mg/kg, with an insignificant associated increase in the pressure drop. This behavior is ascribed to the increased flow velocity and hence turbulence level with the added air, the effect that overweighs the retarding effect of the declined thermal properties of the mixture. The outcome of this study is expected to pave the way for the development of novel heat transfer equipment encountered in the relevant thermal energy conversion processes.
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Yutaka UMEMURA, Takehiro HIMENO, Kastuhide OHIRA, Osamu KAWANAMI, Kiyo ...
Session ID: C113
Published: 2016
Released on J-STAGE: June 19, 2017
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The payload capacity of launch vehicles must be increased in order to allow the exploration and development of space to be extended from low-Earth orbit into the solar system. A propellant system using a cryogenic fluid must reduce the amount of unusable propellant due to evaporation and boiling. However, in space exploration and development, where safety and reliability of missions are critical, predictions of the boiling heat transfer of current technology are not sufficiently reliable for thermal management design due to a lack of knowledge and relevant research. Therefore, the objective of this research is to understand and accurately predict boiling heat transfer by developing numerical simulation tools for two-phase flows that consider phase change. In this paper, recent research activity toward the development of chill-down process simulation technology is presented.
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Makiko Ando, Atsushi Okamoto, Kosuke Tanaka, Hiroyuki Sugita
Session ID: C114
Published: 2016
Released on J-STAGE: June 19, 2017
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An oscillating heat pipe (OHP) is desired as an excellent thermal control device for the thermal management system of future spacecraft with larger heat dissipation, and a flat-plate heat pipe (FHP), a type of OHP with check valves, has been developed. Applying FHP to spacecraft, the heat transfer characteristics of FHP under micro-gravity conditions should be examined. The on-orbit experiment of FHP had been conducted since 2012 as one of the Small Demonstration Satellite-4 (SDS-4) missions. FHP showed good heat transfer characteristics, the same as those under 1g conditions, and no degradation was seen for almost 4 years on orbit.
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Niro Nagai, Shingo Oida
Session ID: C115
Published: 2016
Released on J-STAGE: June 19, 2017
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Bubble-actuated circulating heat pipe, BACH, is one of new types of heat pipe, utilizing buoyancy force of vapor bubbles generated at bubble-generation part for liquid circulation. In the former report, top-heat BACH consisting of heated section, cooled section and intermediate cooled section were presented. The bubble buoyancy force acts only at between the heated section and the intermediate cooled section, realizing liquid circulation for heat transport from the heated section to the cooled section. The heat transport model of the topheat BACH was proposed in the former report which show that heat transport rate of top-heat BACH is affected by several parameters. However, there were several problems to solve in order to establish general heat transport modeling of BACH. In this report, the authors proposed methods to solve these problems.
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Hideaki Teshima, Takashi Nishiyama, Koji Takahashi
Session ID: C121
Published: 2016
Released on J-STAGE: June 19, 2017
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Since the existence of nanobubbles at solid-liquid interface was first suggested, many studies have reported the success of observing nanobubbles. However, the surprisingly stability mechanism is still unclear. In this work, we investigated surface nanobubbles at a pure water-highly ordered pyrolytic graphite interface by peak force tapping mode. To explain the stability, we introduced “pinning force,” which acts as a force per unit length on three-phase contact line and estimated it quantitatively. The metastability of coalesced nanobubbles was explained in terms of differences of the pinning force between the semispherical parts and the joint part.
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Yoko TOMO, Takashi NISHIYAMA, Tatsuya IKUTA, Yasuyuki TAKATA, Koji TAK ...
Session ID: C122
Published: 2016
Released on J-STAGE: June 19, 2017
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Liquid cell electron microscopy (LCEM) is a useful experimental method of bubble nucleation, which is not understood sufficiently because it is difficult to observe nucleation at nanometer scale in real-time. In our TEM observation, when an electron beam irradiated water, interfacial nanobubbles were generated and grew in a nano liquid cell, whose gap was filled with pure water between two silicon nitride (Si3N4) membranes. In this paper, we introduce Fresnel fringe method, which enable to understand the position of nucleated nanobubbles and the interaction between nanobubbles on the surface of top Si3N4 membrane and the bottom membrane.
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Ryosuke Hosoya, Osamu Nakabeppu
Session ID: C123
Published: 2016
Released on J-STAGE: June 19, 2017
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Formation and evaporation mechanisms of the microlayer beneath a flat bubble of water in the mini-channel have been investigated by measuring the local wall temperature and the steam temperature in bubble with MEMS thermal sensor, T.C. having the diameter of 25μm and a high speed observation. The initial microlayer thickness and evaporation thickness were evaluated from the local wall heat flux by one–dimensional transient heat conduction analysis with the wall temperature data. The dimensionless initial microlayer thickness and evaporation thickness increased with Capillary number corresponding to the ratio of the viscous force and the surface tension.
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Sota Kuroki, Tomohide Yabuki, Koji Miyazaki
Session ID: C124
Published: 2016
Released on J-STAGE: June 19, 2017
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In this study, we investigated the influence of the surface wettability on behavior of thin liquid film in the minichannel boiling and heat transfer characteristics. In the air bubble injection experiment under adiabatic condition, the liquid-repellent-type dry-out, where a thin liquid film on the wall ruptures and then the nucleated dry-patch expands without heating, was observed on the bare silicon surface with the contact angle of 50°. On the other hand, the liquid-repellent-type dry-out was not observed on the superhydrophilic surface. The minichannel boiling experiment using the superhydrophilic surface fabricated by wet-etching and chemical oxidation was conducted, and the superhydrophobic surface was found effective to prevent the liquid-repellent-type dry-out that potentially deteriorate the heat transfer coefficient.
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Yuki Mikoshiba, Hiroyasu Ohtake, Koji Hasegawa, Tomohito Nishimura
Session ID: C125
Published: 2016
Released on J-STAGE: June 19, 2017
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Dropwise condensation (DWC) has high heat transfer coefficient. However, it is difficult to maintain DWC for a long time. It is important to understand the effect of the surface condition. In the present paper, the wettability of the metal-sputtered surfaces were controlled by MEMS technology. The effect of several metal-sputtered surfaces, i.e., Titanium (Ti), Silver (Ag), Chromium (Cr), and Lead (Pb) on the pattern of the condensation, i.e., DWC or FWC, was examined qualitatively. The surface condensation with sputtered thin Silver (Ag) and Lead (Pb) films were DWC. On the other hand, the surface condensation with sputtered thin Titanium (Ti) and Chromium (Cr) films were FWC. For DWC, the surface adsorption force was lower than that of FWC. These results can be explained by Young's equation.
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Daniel Orejon, Yutaku Kita, Yuya Okauchi, Yuki Fukatani, Masamichi Koh ...
Session ID: C131
Published: 2016
Released on J-STAGE: June 19, 2017
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In this work we investigate the effect of relative humidity and ambient temperature on the self-generated hydrothermal waves at the liquid-vapor interface of evaporating ethanol drops by means of infrared thermography and CCD camera. Absorption and/or condensation of water vapor onto the drop was found to have a strong impact on the thermal patterns retrieved at the drop interface. Furthermore, we make use of gas chromatography to quantify for the first time water absorbed and/or condensed onto the drop. To conclude, we highlight the importance to account for the heat of water absorption/condensation in order to characterize the complete heat and mass transfer problem during organic solvent drop evaporation.
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Kazuyoshi Sadamura, Haruyuki Nishijima, Yosuke Kawamura, Masafumi Naka ...
Session ID: C133
Published: 2016
Released on J-STAGE: June 19, 2017
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Recently, the refrigeration air conditioning or heat pump system using the two-phase flow ejector is beginning to appear, as the efficiency of the ejector cycle is improved largely in comparison with the conventional system. Shock and expansion waves can occur in the internal flow fields of the ejector, and the effect of the pressure fluctuation by those waves must be considered on the designs of the ejector. In this study, the pressure fluctuation of the shock wave appeared at the outlet of the two-phase flow nozzle are measured by using the HFO1234 refrigeration cycle. It was clarified by experiment that the pressure fluctuations are increased with the strength of the shock waves for each inlet quality.
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Daichi Tokumoto, Hajime Onishi, Yukio Tada
Session ID: C134
Published: 2016
Released on J-STAGE: June 19, 2017
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This study experimentally investigated the refrigerant distribution and evaporation characteristics in parallel micro channels in airfoil-shaped tube. Test section consisted of two stainless steel tubes that have inner diameter of 0.8mm using R134a as the refrigerant. The effects of heat flux and heat flux ratio on refrigerant distribution, pressure drop and evaporation heat transfer were investigated. The results revealed that mass flow rate ratio and pressure drop decreased with increasing heat flux ratio. Moreover, it was found that with increasing heat flux ratio, the variation of the vapor quality of the tube with high heat flux condition became larger due to the decrease of mass flux.
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Sota Kitabayashi, Koji Enoki, Tomio Okawa
Session ID: C135
Published: 2016
Released on J-STAGE: June 19, 2017
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The secondary droplets production during the drop impingement onto a liquid film has been studied extensively by many researchers. It is known that the two types of splashing mechanisms are present: the prompt splash and the late splash. In the prompt splash, small droplets are scattered with high velocity immediately after the impact. Whilst, in the late splash, larger droplets of lower velocity are produced after the development of liquid crown. In the present experiments, the empirical correlations of splashing limit for pure water are proposed separately for the prompt and late splashes. Since the splashing limit was dependent on the impact velocity and liquid film thickness, the two dimensionless numbers (the Weber number and the dimensionless film thickness) were used in the correlations.
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Hiroto Sakashita
Session ID: C211
Published: 2016
Released on J-STAGE: June 19, 2017
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This paper investigates the CHF in saturated pool boiling of ethanol, R141b, and water on a 7 mm diameter vertical copper surface at high pressures. The results show that the well-known Kutateladze-Zuber type CHF correlation explains the variations in the CHF with pressure well for ethanol and R141b, and underestimates the pressure dependence of the CHF for water. A correlation considering the effect of surface wettability on the CHF agrees fairly well with the CHF for water in the whole range of pressures here, when the temperature dependence of the contact angle determined from available data is incorporated into the correlation.
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Masashi Inoue, Hiroyasu Ohtake, Koji Hasegawa
Session ID: C212
Published: 2016
Released on J-STAGE: June 19, 2017
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The present paper aimed to clarify the boiling heat transfer, especially the mechanism of the critical heat flux. Pool boiling experiments were conducted the copper thin film on the silicon wafer by the sputtering. Test liquid was distilled water. The system pressure was 0.01 and 0.10 MPa, respectively. Boiling heat transfer mechanism was examined through two-dimensional temperature field and high speed observations of the boiling bubble. Temperature of the test heater was measured by using a infrared thermometer from a back side of it. The temperature fluctuation on the test heater was considered with bubble behavior.
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Shinichiro Uesawa, Yasuo Koizumi, Mitsuhiko Shibata, Hiroyuki Yoshida
Session ID: C213
Published: 2016
Released on J-STAGE: June 19, 2017
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Seawater pool nucleate boiling heat transfer experiments with deposited sea salts on a heat transfer surface was conducted, in order to understand effects of the deposited sea salt on boiling heat transfer for seawater in reactor cores in the accident at the Fukushima Daiichi Nuclear Power Station. The present study indicated that a heat transfer surface temperature excursion occurred at a certain heat flux for seawater boiling because the deposited sea salt layer became thick, and then a thermal resistance. Finally, burn-out of the heat transfer surface occurred when the temperature reached the melting point of the heat transfer surface by the increase of the thermal resistance of the deposited sea salt. The phenomenon was a peculiarly seawater boiling phenomenon. The burn-out mechanism was different from that for the pure water.
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Makoto ITO, Kei KOBAYASHI, Tatsuya KOWA, Manabu TANGE
Session ID: C214
Published: 2016
Released on J-STAGE: June 19, 2017
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This study reports a heat flux partitioning during pool boiling in a confined space derived from the flow field and the liquid film structure. The PIV method measured the flow field near a heat transfer surface and the backlighting method clarified the liquid film structure beneath bubbles. The total heat transport was evaluated as the Nusselt numbers of two modes: sensible heat transfer due to microscale convection and latent heat transfer due to liquid film evaporation. At relatively high heat flux, heat transport due to the liquid film evaporation played a dominant role. Evaluated Nusselt number of the liquid film increased and that of the microscale convection decreased as the heat flux increased.
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Masayuki Yamada, Biao Shen, Sumitomo Hidaka, Masamichi Kohno, Koji Tak ...
Session ID: C215
Published: 2016
Released on J-STAGE: June 19, 2017
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In the present study, to investigate the mechanism of transition to intermittent boiling, we have conducted a visualization study of pool boiling on biphilic surfaces at subatmospheric pressures. Experiments were conducted on copper surfaces with a single hydrophobic spot at their centers. The hydrophobic spots were made by PTFE spray coating, and their contact angles were 120–130°. Bubble behavior on the spot was captured using a high speed camera (with 1000 fps). Compared to that at atmospheric pressure, considerably different bubble behaviors were observed under sub-atmospheric conditions. It was suggested that dynamics of the three-phase contact line of bubble was closely related with the transition to intermittent boiling.
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Shintaro Sakamoto, Kazuhiro Kaiho, Koji Enoki, Tomio Okawa
Session ID: C221
Published: 2016
Released on J-STAGE: June 19, 2017
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Numerical simulation of subcooled flow boiling in a vertical rectangular duct was carried out using a one-way bubble tracking method; this method treats each bubble as an individual particle. Although a bubble behavior after lifting off the heated surface depends on the bubble size and velocity at lift-off, these lift-off conditions are not taken into consideration in existing subcooled flow boiling models. In the present simulation, the distributions of lift-off velocity and bubble size were considered. It was demonstrated that the calculated void fraction in subcooled flow boiling is influenced significantly by the lift-off conditions.
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Wei Liu
Session ID: C222
Published: 2016
Released on J-STAGE: June 19, 2017
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Prediction of Critical Heat Flux (CHF) is important for nuclear reactor safety. However, the CHF prediction for subcooled flow boiling in complicated geometry such as fuel assembly still remains unsolved. As the first step for the CHF prediction in rod bundles, in this paper, we tried to predict the CHF in annulus, which is the most basic flow geometry simplified from a fuel bundle. We performed the CHF prediction by using liquid sublayer dryout model, combining with ANSYS CFX code to get the single phase velocity distribution inside the annulus. The results show that the CHF in annulus can be predicted in an accuracy of about ±20%.
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Kota Kiyomi, Satoshi Matsumoto, Kenichiro Sawada, Yutaka Abe, Akiko Ka ...
Session ID: C223
Published: 2016
Released on J-STAGE: June 19, 2017
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This paper deals with subcooled flow boiling experiments using various different dissolved air concentrations in the Perfluorohexane (PFH). To clarify its effects on the flow boiling heat transfer through a tube with an inner diameter of 4 mm, flow boiling experiments were conducted by varying levels of mass flux. As a result, dissolved air was shown to affect boiling characteristics. In particular, dissolved air significantly affected the boiling curve in the low heat flux region. Boiling curve of higher dissolved air concentration after onset of boiling has lower excess temperature than the lower dissolved air concentration. Furthermore, dissolved air effects were varied mass flux.
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Takaho KOREKAWA, Takeyuki AMI, Hisashi UMEKAWA, Mamoru OZAWA
Session ID: C224
Published: 2016
Released on J-STAGE: June 19, 2017
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Entrainment under high heat flux is one of a key important factor for predicting a liquid film dryout in annular flow, because liquid droplets would be produced due to not only interfacial shear stress but also breakup of bubble in liquid film. In this experiment, the liquid droplet flow rate in boiling two-phase flow was measured by using an isokinetic sampling method. On the basis of entrainment fraction just below CHF condition, the applicability of this method was confirmed. As the results, under high quality condition, the liquid droplet flow rate shows the good agreement with a film flow model, while the liquid droplet cannot be measured due to disturbance wave under low quality with high mass flux condition. These data implied to exist of the entrainment due to boiling, and more detail investigation is needed.
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Ryuma Fujiwara, Takeyuki Ami, Hisashi Umekawa, Mamoru Ozawa
Session ID: C225
Published: 2016
Released on J-STAGE: June 19, 2017
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Understanding of re-flooding phenomena under oscillatory flow condition is important for the development of emergency core cooling system of a LWR and simplified BWR. In this investigation, the re-flooding experiment was conducted under both steady flow and oscillatory flow forcibly induced by a oscillator installed at downstream of pump. The period and amplitude of oscillation are arbitrary controlled. As the results, the flow pattern has been estimated with an equivalent hydraulic height based on pressure drop, and the heat transfer calculated with one-dimensional heat balance has been evaluated on each flow pattern. The influence of oscillatory flow is clearly appeared in the region of inverted-annular flow not dispersed flow.
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Jun Moriyasu, Masaya Nakahara, Takafumi Doo, Fumiaki Abe
Session ID: D111
Published: 2016
Released on J-STAGE: June 19, 2017
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The present study is performed to investigate experimentally the deflagration flame of hydrogen-propane-air mixtures propagating in a narrow space simulated channel ( t10×w150×h500 mm ) with special attention to flame acceleration and deceleration. In order to examine the effects of C3H8 addition and the grids on the flame propagation speed, the mixtures with different equivalence ratios (ϕ=0.8~1.4) with different propane additional rates (δp=0.2~1.0) are prepared. The flame shape and propagation speeds are obtained by using sequential shadowgraph or schlieren images recorded under conditions which are the ignition near the bottom and the upper-end open of channel. It was found that as the additional rate of C3H8 increase, the acceleration of flame propagation tends to be suppressed, especially for lean mixtures.
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Hiroshi Terashima, Yu Daimon
Session ID: D112
Published: 2016
Released on J-STAGE: June 19, 2017
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Detailed structures of gaseous CH4/O2 combustion flow fields behind a GOX post of rocket engines have been numerically investigated by using the Navier-Stokes equations with a detailed chemical kinetic model. The results show that the two types of combustion flow structures are established in the region behind the GOX post according to CH4 and O2 jet injection conditions. A broad higher-temperature region appears with a single anticlockwise recirculation region for larger velocity ratios of CH4 to O2 jets, while a lower-temperature region is formed with the presence of non-premixed flame structures and additional generations of another clockwise recirculation region for smaller velocity ratios.
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Hiroaki Watanabe, Akiko Matsuo
Session ID: D113
Published: 2016
Released on J-STAGE: June 19, 2017
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Spontaneous hydrogen ignition inside and outside the tube is simulated by two-dimensional axisymmetric calculation with detailed chemical model in order to estimate the shock heated region and the effect of tube length on the spontaneous ignition. From comparison of shock propagation speed with experimental and theoretical results, the present results show good agreement and are validated. The volume of shock heated region does not change very much regardless of burst pressure under the condition that the position of shock wave from the diagram is the same. On the other hand, ignited volume increases as the burst pressure increases. Spontaneous ignition is likely to occur when the tube length increases due to the increment of shock heated region and ignited region.
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Makoto Asahara, Takeshi Miyasaka, Katsuo Asato
Session ID: D114
Published: 2016
Released on J-STAGE: June 19, 2017
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This paper deals with the simulations of hydrogen release from the storage to ambient through the release orifice 1.91mm opening. In this study, the numerical simulations were compared with an experiment implemented by Schefer et al. using Reynolds stress model. Based on the finding, the numerical results and the experiment results about distribution of time averaged hydrogen concentration have qualitatively similar features. Also, it is clarified that axial hydrogen concentration have an agreement, compared between the numerical results and the experiment results. In addition, we put high temperature region at ignition region forced ignition indicated by Schefer et al. As the results, a flame kernel is formed and extinct to drift towards downstream.
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Kazunori Kuwana, Kenta Suzuki, Yuki Tada, Genichiro Kushida
Session ID: D121
Published: 2016
Released on J-STAGE: June 19, 2017
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This paper presents results of theoretical and experimental studies on smoldering combustion of thin solid with a particular focus on its stability. In a recent study, an effective Lewis number was proposed to be the governing parameter of the phenomena; it was shown that combustion characteristics such as the fraction burned and the finger width can be expressed in a unified manner using the effective Lewis number. In this paper, an attempt is made to express the experimentally measured smoldering spread velocity as a function of the effective Lewis number.
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Takuya Nakajima, Hiroyuki Torikai, Akihiko Ito
Session ID: D122
Published: 2016
Released on J-STAGE: June 19, 2017
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The purpose of this study is to reveal the characteristics of jet diffusion flame under partial gravity environment. To understand the flame structure, the flame height and the surface area of jet diffusion flame were measured. The gravitational acceleration was changed 1G to 0.55G. The flame height was increased with increasing Reynolds number. The flame height H and characteristics length L were arranged by Peclet number and Froude number as H/L = 0.1188Pe0.667Fr-0.0861.
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Fumiya Mitsui, Masashi Nagachi, Jean-Marie Citerne, Hugo Dutilleul, Gr ...
Session ID: D123
Published: 2016
Released on J-STAGE: June 19, 2017
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Flame spread tests were conducted to obtain Limiting Oxygen Concentrations (LOC) of electric wires in external flow condition of 100 mm/s. The ignition power and heating time were varied as parameters to reveal the effect of the ignition condition on the LOC value. In the experiments, polyethylene-coated Nickel-Chrome wires were used as the sample wires, and a coil heater was used as the ignition source, which consisted of 0.50 mm diameter Kanthal wire. Experiments were conducted in both normal gravity and microgravity. The experimental results show that the LOC gradually decreases as the ignition power or heating time increases and eventually it became almost constant.
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Akito Sugahara, Takeshi Yokomori, Ryo Ohmura, Toshihisa Ueda
Session ID: D124
Published: 2016
Released on J-STAGE: June 19, 2017
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We conducted the flame extinction experiments for the pool flame with deep fuel depth in the thermally stable glass container by using the ice, dry ice, CO2 hydrate as a flame extinguisher. Methanol and 1-hexanol are used as a fuel. The boiling point of the methanol is lower than that of the water, while that of the 1-hexanol is higher. Motion of the flame extinguisher was observed by a high-speed camera. When the flame extinguisher except CO2 sank into the fuel.
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Yasuo Hattori, Keisuke Nakao, Hitoshi Suto, Yuzuru Eguchi, Hiromaru Hi ...
Session ID: D131
Published: 2016
Released on J-STAGE: June 19, 2017
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We performed a large-eddy simulation for a natural convection boundary layer along a vertical plate heated at high temperature, which gave the turbulence transition with the significant non-Boussinesq effects. An open source CFD code, Fire FOAM, was used to consider the density fluctuation effects directly and the one-equation model was applied to estimate SGS components. The spatial distributions of statistics with Reynolds decomposition clearly showed the transition at Grz ≅ 109; this critical Gr number agreed with that in the boundary layer without non-Boussinesq effects. The non-Boussinesq effects were definitive in the amplification process of fluctuations, i.e., the density fluctuations primarily generated the velocity fluctuations with reduction in correlation with temperature fluctuations.
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Shinnosuke Nishiki
Session ID: D132
Published: 2016
Released on J-STAGE: June 19, 2017
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Numerical simulation of upward fire spreading in woody material pile is described in this paper. The combustion simulation of woody material, such as wood pellets or wood chips, is attempted by FDS (Fire Dynamics Simulator) of popular software in the fire research. The difference of filling rate of the woody material or grid size is possible to strongly affect calculation accuracy. In order to improve the calculation accuracy, woody material pyrolysis model must be reformed and grid size effect should be investigated.
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Yuji Nakamura, Jian Gao, Tsuneyoshi Matsuoka
Session ID: D133
Published: 2016
Released on J-STAGE: June 19, 2017
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This paper examines the feasibility of adopting conventional “heat-release-rate prescribed” fire source model to predict the potential fire damage in early (developing) stage of the fire. Numerical experiments are performed to investigate the difference in the time-variation of heat flux onto the ceiling, if any, between following two models; one is real fire model (with-flame, with-radiation) and the other is conventional fire mode (without-flame, without-radiation). Results show the predicted heat flux onto the ceiling are under-estimated when the conventional model is adopted, suggesting that the conventional model is not conservative and might not be suitable to predict the fire fighting strategy. The cause of the difference is discussed and the potential engineering model to compensate such difference is proposed.
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Shingo Kuwana, Hidekazu Tamizu, Hiroyuki Torikai, Akihiko Ito
Session ID: D134
Published: 2016
Released on J-STAGE: June 19, 2017
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The purpose of this study is to reveal the flame spreading mechanism of tsunami fire. But the mechanism of tsunami fire is so complex that we could not assess qualitatively. So the basic research on tsunami fire is needed. As a first step, we did flame spread experiment on only fuel and liquid fuel/water layer under static. When fuel temperature is 20 ~ 45 ℃, flame spreading rate over only liquid fuel is faster than liquid fuel/water layer's at same fuel temperature. By these result, we did scaling analysis to estimate flame spreading rate at various conditions.
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Atsushi Tsuruta, Yuki Ueda
Session ID: D211
Published: 2016
Released on J-STAGE: June 19, 2017
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Oscillating flow type steam engine is a mechanism to extract the output using the thermal self-excited vibration caused by repeating the fluid is a gas-liquid phase change in the tubules. It is essentially same to the Pop-pop boat engine has been experimentally investigated. In this study, we measured P-V diagram , input power, output power and amount of heat transport to the heater of some rotation speeds, and confirmed that output power was 1.5W under the conditions that rotation speed was 60rpm and the temperatures of heating and cooling sections were 200 and 70℃.
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Taishi Hirata, Yuki Ueda
Session ID: D212
Published: 2016
Released on J-STAGE: June 19, 2017
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Heat exchangers are some of the most important parts in thermoacoustic devices. In oscillatory flow condition, the flow and temperature fields around the heat exchangers are quite complex and it may significantly affect their heat transfer behavior. As a result, we cannot directly apply the heat transfer definition for a steady flow to the design of heat exchangers operating in oscillatory flow conditions. Moreover, the fundamental knowledge of heat transfer in oscillatory flow is still not well established. By measuring the heat transfer between the heat exchangers and working fluid in oscillatory flow, we define evaluation index of heat transfer performance. We confirm that incorporating the device improve performance.
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Junya Onishi, Masashi Saito, Naoki Shikazono
Session ID: D213
Published: 2016
Released on J-STAGE: June 19, 2017
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We have conducted numerical simulation of a bubble rising in a capillary tube by using a novel Cartesian grid method. The present method is distinguished from the others by the use of the sharp interface model for the treatment of both liquid-gas interfaces and solid surfaces. The bubble rise velocity obtained by the present simulation has been compared with the existing experimental data at a wide range of Eotovos numbers, and has been shown to be in fairly good agreement. It has been suggested from the comparison study that the grid resolution inside a liquid film, created in between the bubble and the tube wall, is important to predict the rise velocity accurately.
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Takafumi Morisaki, Takeshi Yasunaga, Yasuyuki Ikegami
Session ID: D214
Published: 2016
Released on J-STAGE: June 19, 2017
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Low-grade Thermal Energy Conversion (LTEC) utilizes the unutilized heat source. The important to improvement performance of LTEC system is the thermal efficiency enhancement because of a small temperature difference between high- and low-temperature heat sources. This paper investigates on the influence of the temperature difference between high- and low-temperature heat sources on the system performance of the multi-stage Rankine cycle. As a result, maximum power and heat sources temperature change increase with an increase of the temperature difference. On the other hand, the temperature difference has little influence on the effectiveness ratio of maximum power output.
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Taika Horikawa, Yutaka Tabe, Takemi Chikahisa
Session ID: D221
Published: 2016
Released on J-STAGE: June 19, 2017
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Effective use of exhaust heat from a combined heat and power (CHP) in summer is an issue. This study tries to develop absorption refrigerator using exhaust heat from home CHP. We selected active carbon-ethanol pair for this refrigerator, and cooling capacity analysis showed that adsorption refrigerator using this pair works with high efficiency. To evaluate the effectiveness of introducing absorption refrigerator, the cost and CO2 emission analysis in the case with absorption refrigerator and CHP was conducted. This indicated that absorption refrigerator with CHP has a potential of CO2 emission reduction with low cost. In addition, we developed an experimental system of trial model.
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Tomoya Obuchi, Toshiaki Tsuchiya
Session ID: D222
Published: 2016
Released on J-STAGE: June 19, 2017
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It is well known that the wet compression technique is effective to improve the performance of gas turbines. A model has been developed to investigate the evaporation behavior of water droplets under gas turbine environments. The temperature of a water droplet has been calculated by treating the droplet as a lumped thermal mass with one representative temperature uniformly distributed in the droplet. It is assumed that the change of water droplet temperature is caused by convective heat transfer through droplet surface. The evaporation rate is calculated based upon mass transfer between water droplet and surrounding air flow. Based on the proposed model, the calculations have been conducted to investigate the evaporation behavior of water droplets in the compressor of Capstone C30 micro gas turbine.
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Hosei Nagano, M. P. Shyam, Chiemi Oka, Seiji Yamashita, Tsuyoshi Bessy ...
Session ID: D223
Published: 2016
Released on J-STAGE: June 19, 2017
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This paper reports the test results of a newly developed kW-class loop heat pipe (LHP), which is passive heat transfer device, for effective heat utilization of automobile. The LHP has 2 μm wick made of stainless steel. Pure water was used as a working fluid. The LHP was designed, fabricated, and tested under atmospheric condition. The LHP could transport heat up to 1.9 kW. A transient thermal analysis model based on a mass-spring-dumper system was also developed and compared with the test results. The analytical result relatively agreed well with the test result.
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Hiroshi Sekiya, Mitsuru Kera, Kazuo Okamura, Mark Sueyoshi, Masaharu I ...
Session ID: D224
Published: 2016
Released on J-STAGE: June 19, 2017
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Introduction of a waste carbonization furnace is advanced as a countermeasure to the global environmental problem. To reduce the power consumption of the carbonization furnace which is able to carbonize oily waste and recover oil in the oil field, the authors installed the Stirling engine generator into the carbonization furnace and conducted a demonstration. As a result, output of power generation 214W was obtained, and a possibility of the exhaust heat generation of electricity for the carbonization furnace using the Stirling engine generator could be proved.
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Choyu Watanabe
Session ID: D225
Published: 2016
Released on J-STAGE: June 19, 2017
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This paper describes theoretical and experimental study on heat recovery high temperature heat pumps. Firstly, two examples of trans-critical cycle heat pumps using CO2 or butane as each refrigerant are simulated. Secondly, sub-critical cycle heat pumps using R1234yf are discussed. A sub-critical cycle heat pump with small degree of sub-cooling are simulated for low temperature-rise heating. And, a sub-critical heat pump cycle with large degree of sub-cooling are simulated for high temperature-rise heating. Further, a test apparatus is presented.
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Session ID: D231
Published: 2016
Released on J-STAGE: June 19, 2017
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Measurement of a temperature field in the thermoacoustic engine is usually performed by a thermocouple. However, it is difficult to investigate thermoacoustic phenomena occurring in engine core in detail. In this study, in order to make clear temperature field in heat exchangers and regenerators, two-color toluene Laser Induced Fluorescence (LIF) is employed. As the first approach for the measurement by toluene two color LIF, temperature field by distributed between parallel plate simple heat conduction is visualized.
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Yosuke OGAWA, Mariko SENGA, Ryunosuke HASEGAWA, Kazuto KUZUU, Shinya H ...
Session ID: D232
Published: 2016
Released on J-STAGE: June 19, 2017
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The traveling wave thermoacoustic engine amplifies the acoustic power when a traveling wave passes the bundle of narrow channels with an axial temperature gradient. It has been experimentally determined that the maximum gain reaches ratio of absolute temperatures when using an ideal gas. In this study, we set up the traveling wave thermoacoustic engine combined with oscillatory water flow, and for this device with liquidvapor phase change, the acoustic power is measured by both Laser Doppler Velocimeter(LDV) and pressure trasducers. The result indicates that liquid-vapor phase change achieves the acoustic power amplification beyond the theoretical limit of ideal gas.
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