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Manabu YAGI, Tadaharu KISHIBE, Susumu NAKANO
Article type: Article
Session ID: 4342
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Effects on adiabatic efficiency of meridional dimensions for radial inflow turbine impeller were investigated. Following Taguchi method, 8 meridional dimensions were selected as control parameters, and 2 or 3 levels were considered to each parameter. The second level was fixed the dimensions of present turbine impeller. Adiabatic efficiencies were calculated by using commercial softwares. Accuracy of the predictions which were carried out by those softwares had been improved by adjusting multipliers of loss models to reflect the experimental results. As the results, the most sensitive meridional dimension to achieve high adiabatic efficiency was impeller outlet tip diameter. It can be concluded that the reduction of both exit kinetic energy and friction loss was the most effective to design for high efficiency radial inflow turbine.
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Shigeo HATAMIYA, Shinya MARUSHIMA, Hidefumi ARAKI
Article type: Article
Session ID: 4343
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The Advanced Humid Air Turbine system improves the gas turbine thermal efficiency by using high-humidity air without needing a high firing temperature and pressure ratio. The following gas turbine elemental technologies concerning humidity air have been developed to realize the AHAT system: compressor, recuperator, turbine blade cooling, and combustor. A system verification plant that consists of a gas turbine generator (two-stage radial compressor with pressure ratio 8, two-stage axial turbine, single-can combustor), recuperator, humidification tower, water recovery system, and other components will be completed in a few months. The validation and performance test begin in October 2006. The expected performance is: rated output 3.6MW, efficiency 43% (LHV), and NO_x emissions less than 10ppm at 16% O2 from 50% to 100% load.
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Toru TAKAHASHI, Yoshinobu NAKAO, Eiichi KODA
Article type: Article
Session ID: 4344
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Some gas turbine systems such as AHAT that increase the power output and improve generation efficiency by using high humid air are proposed. We analyzed these systems under the same calculation condition, evaluated the thermal characteristic of these systems, and compared the generation efficiency of these systems. The atmospheric temperature characteristic of AHAT was analyzed to compare with that of combined cycle. In addition, four methods of part load were examined to analysis part load characteristic of AHAT, and it was compared with that of combined cycle. As a result, we understood the atmospheric temperature characteristic and part load characteristic of AHAT were better than that of combined cycle.
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Kenichi HIGUCHI, Hideyuki SUEHIRO, Takeshi UEDA, Akira NAGASHIMA
Article type: Article
Session ID: 4345
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes the development of the accurate numerical simulation that evaluates heat exchange performance at different layouts of heat transfer tubes. The method to simulate the performance of fin tube heat exchanger is the combination of the physical model that predicts a state of refrigerant and air based on the governing equations, and the fundamental experiment and fluid dynamics analysis to acquire heat transfer characteristics (Target product is a Gas Heat Pump operated by R410A refrigerant).
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Isao KATAOKA, Kenji YOSHIDA
Article type: Article
Session ID: 4346
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In recent years, various heat supply systems for private houses have been developed for the purpose of reduction of energy consumption and greenhouse gas emission. Among them, gas engine cogeneration system and heat pump system are most typical and in practical use. It is quite important to evaluate the thermal efficiencies of these heat supply systems. The simulation models have been developed for these systems and the evaluation of thermal efficiencies was carried out for the typical thermal and electricity consumption patterns in private houses. The simulation result indicated that heat pump system is effective in reduction of energy consumption compared with gas engine cogeneration system
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Michiyuki SAIKAWA
Article type: Article
Session ID: 4347
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The reverse Carnot cycle, the high and low heat source of which are constant temperatures, decides the theoretical limit of COP of conventional heat pumps used as air conditioners etc., but the cycle which decides the theoretical limit of COP of a heat pump used as tap water heater is considered the cycle whose high heat source varies temperature with constant specific heat, because the specific heat of tap water is constant and tap water heating with high temperature rise is needed. In this paper, the theoretical COP of this cycle is clarified. And upper limit COP of heat pump cycle with various refrigerants for tap water heating is studied and finally the refrigerant which achieves the highest COP for supplying hot water is clarified.
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Kenji UEDA, Yasushi HASEGAWA, Yoshinori SHIRAKATA, Kenichiro NISHII, W ...
Article type: Article
Session ID: 4348
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The turbo compressor of heat-pump works wide range operating area, so that, a variable speed control method is essential factor for stable operation. An application of optimized variable speed control is incomplete without experimental data of turbo compressor. These data of turbo compressor show that theoretical characteristic line of adiabatic head-capacity must be modified on each rotated speed.
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Katsumi HASHIMOTO, Akihiro KIYOTANI, Naoe SASAKI
Article type: Article
Session ID: 4349
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The CO_2 heat pump water heater has a high potential for energy conservation and greenhouse abatement. To encourage the broader use of the heat pump water heater, it is necessary to develop space saving and high efficient equipment. The most important element is always the evaporator. Experimental studies have been conducted to measure the pure CO_2 (99.999% purity, without oil) flow boiling heat transfer coefficient in a horizontal smooth tube (outer diameter 6mm, thickness 0.4mm). In our previous report, the mean heat transfer coefficient had a peak value at a certain mass velocity or a heat flux, but which influence strongly affected the result was not understood. In this report, to distinguish the influence of mass velocity and that of heat flux to the heat transfer coefficient, the tube length is varied to 3.0m, 4.0m and 5.0m. The test conditions were: CO_2 mass velocity from about 150 to about 700kg/(m^2s), saturation temperature of CO_2 are about 0, 5 and 10℃, quality at inlet of test section is fixed to be 0.17 and CO_2 super heat at outlet of test section is fixed to be 5K. As a result, it has been understood that heat flux has a greater influence on the heat transfer coefficient.
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Kenji YOSHIDA, Keisuke SHIOOMI, Fumihito ANDOU, Isao KATAOKA
Article type: Article
Session ID: 4350
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We employed the recent micro-order surface machining technology on the heating surface and produced the artificial micro-ordered groove pattern on the heating surface. The pool boiling heat transfer characteristics and the frost phenomena on the artificial surface with micro-structure are experimentally investigated. The effects of the groove depth or pattern pitch between grooves on the heat transfer promotion and frost characteristics were especially focused. For the boiling experiments, the measurements for the surface temperature and heat flux on the heating surface were carried out by using thermocouples and obtained the boiling curve by changing the surface properties. The direct observations for the bubble nucleation on the heating surface were also carried out by using a digital camera. For the frost phenomena, the direct observations of the frost and melting phenomena on the surface by using the microscope were carried out. It is cleared that the groove pattern pitch strongly affects the diameter of droplets formed after the frost melting.
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Teppei Nagatomi, Rafael Batres, Yuji Naka
Article type: Article
Session ID: 4401
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper presents a systematic approach for the synthesis of biomass processing networks. Biomass refers to any renewable organic matter such as agricultural crops and residue, wood and wood waste, animal waste, and organic components of municipal and industrial wastes. The purpose of the proposed approach is to determine the optimal interconnection of processing units (equipment items) as well as the optimal type and design of the units within a biomass conversion system. Specifically, this paper studies the use of a dynamic programming approach based on an implicit enumeration algorithm that is known to be computationally efficient. To evaluate the feasibility of the proposed approach, a simple synthesis problem involving the conversion of woody biomass is presented that includes biomass physical properties models, as well as gas turbine, drier, and downdraft-gasifier models.
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Kazuhiro KIDOGUCHI, Kazuyoshi ICHIKAWA, Masami ASHIZAWA, Masao KANAI
Article type: Article
Session ID: 4402
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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CRIEPI has been condunting R & D activities on development of "High-efficiency Biomass/Waste Carbonizing Gasification Power Generation System" in collaboration with Okadora Co., Ltd. This system can use various fuels by integrating carbonizing technology of Okadora as pretreatment equipment of the fuel such as biomass and waste, etc. with entrained flow gasification technology of CRIEPI. This system can obtain high thermal efficiency because the fuel such as biomass and waste is fed into the gasifier after pyrolyzed in the carbonizer by using the exhaust gas from the power generation system such as the gas engine. As a result of gasification tests of wood chips, it was clarified that the carbonizing gasifier can provide the sufficient product gas for the gas engine operation.
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Nariyuki YOSHINAGA, Soe NAING, Takanobu YAMADA, Kimio NAKANISHI
Article type: Article
Session ID: 4403
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Biogas produced in fermentation process generally tends to give the excessive in hot season and conversely shows the shortage in winter, resulting in larger waste energy. To keep well-balances production and consumption of biogas, effective storage and recovery system for excessive biogas has been expected in sewage treatment process. In the study, gas hydration was investigated as a storage method with use of a high pressure vessel to find optimum conditions of formation. As results of the experiment and calculation, it was found that hydrate formation could be effectively obtained on specified conditions of initial gas pressure, ambient temperature and amount of ice as a host material. It was also suggested that the hydrate storage system could be successfully applied to an CGS plant.
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Maromu OTAKA, Masami ASHIZAWA, Hiroaki WATANABE, Shiro KAJITANI, Yan Z ...
Article type: Article
Session ID: 4404
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The purpose of this study was to establish and contribute to putting into practical use the technology that converts high-quality upgraded dehydrated biomass (UDB) to gas with high calorific value using a pyrolytic gasifier. The pyrolytic gasifier consists of separate pyrolyzing and combusting sections after dehydrating and deoxidizing biomass with high moisture using the technology of upgrading in oil, which is the technology proven for dehydrating brown coal. Among these processes, our institute took responsibility for elucidating and modeling gasification reaction of UDB, predicting the performance through numerical analysis of a gasifier, and studying the optimum system for the entire system including gas engine generators as well as evaluating its costs.
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Hiroki UEDA, Yasunori OKAMOTO, Hiroshi NODA, Kiyoshi MORIMURA
Article type: Article
Session ID: 4501
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In order to make practical use of energy-saving type cooling system which is possibly introduced into general buildings, an experimental evaluation with the desiccant cooling system (1000CMH machine) that has 5kW cooling ability and can even use the low temperature energy at 70℃ level generated from small type power generator with 5-10kW class power generation amount was made and the field test results were reported.
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Yutaka WATANABE, Kunio MIURA, Toshihiko ISHIZAWA, Masazumi GODO, Norio ...
Article type: Article
Session ID: 4502
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Air humidity control technique with desiccant seems to grow into a major field of air ventilation systems. In 2002 Japanese government provided a rule for continuous air ventilation at least 0.5 times of air volume of house every hour. Also in Western countries to avoid mold and damp, dehumidifier with desiccant becomes popular in airtight residences. We started to develop high performance air-conditioning systems with desiccant ventilation units in 2005 under the direction of NEDO (New Energy and Industrial Technology Development Organization). To achieve the high performance and simple structure we aim to use absorption heat to regenerate adsorbents.
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Hiroshi OKANO, Wei-Li JIN, Tsutomu HIROSE
Article type: Article
Session ID: 46503
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Experimental research about highly-efficient-izing of a desiccant rotor used for a desiccant air-conditioner (Dehumidification) which attracts attention as exhaust heat use apparatus of cogeneration. A moisture absorption characteristic of various desiccant materials were compared with the dehumidification performance for the desiccant rotor using the desiccant material, and the characteristic required for highly-efficient-izing is explored.
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Takuya TSUJIGUCHI, Akio KODAMA
Article type: Article
Session ID: 4504
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We have studied adsorption/desorption behavior of water vapor in a desiccant rotor by means of computer simulation to clarify the operating and design concept of desiccant rotor. First, mass transfer coefficient in mathematical model was derived from curve-fitting with a lot of experimental results and it was related to cycle time by applying the penetration theory. Four types of adsorption isotherm were selected to investigate the influence of shape of adsorption isotherm on the dehumidifying performance. It was found that appropriate shapes of adsorption isotherm existed at each regeneration temperature. Moreover, it was expected to reduce the length of desiccant rotor considerably by selecting appropriate shape of adsorption isotherm since water vapor was adsorbed in a limited part of air flow direction of the rotor when the shape of adsorption isotherm risen sharply at a suitable value of relative humidity was used.
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Yuusuke YAMADA, Takuya TSUJIGUCHI, Akio KODAMA
Article type: Article
Session ID: 4505
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A conventional desiccant cooling process can not produce a sufficient dehumidifying performance enough for the use in high humidity condition. In this study, desiccant cooling process with a reflux flow and two stage adsorption was proposed and investigated experimentally. In this process, air flow path of adsorption side was further divided into two so that once dehumidified air was dehumidified again at the different adsorption zone. Amount of dehumidified water of this process increased by 30 percents as compared with conventional process at the regeneration temperature of 80℃. Moreover, when the ambient air was supplied to the latter half of dehumidification zone, the amount of dehumidified water was rather higher than the case that the ambient air was supplied to the first half of dehumidification zone. This behavior indicated that rotary dehumidifier could be used more efficiency by considering the supply position of ambient air.
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Mitsuhiro KUBOTA, Motohiro SAITAKE, Fujio WATANABE, Hitoki MATSUDA
Article type: Article
Session ID: 4506
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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For the purpose of effective regeneration of an adsorbent applied for a desiccant air conditioning, microwave irradiation to the adsorbent has been proposed. To investigate the effects of microwave irradiation on the rate of water desorption from zeolite and silica gel, the experiment was conducted in a N_2 flow type adsorption column equipped with a microwave irradiator. The desorption amount of water from zeolite with microwave irradiation for 15 minutes was about 1.6 times larger than that with hot air heating. The water desorption from silica gel also indicated similar tendency to that from zeolite. The acceleration of desorption of adsorbed water from adsorbents was achieved by using microwave irradiation. However, change in desorption rate for zeolite was different from that for silica gel in an initial period of desorption.
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Noriyuki KOBAYASHI, Yasuki HIROTA, Kenatro ITO, Masanobu HASATANI, Tak ...
Article type: Article
Session ID: 4507
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Adsorption heat pump system is considered to be one of the most leading technologies to utilize low temperature thermal energy, because it can generate cold heat energy around 283K for air conditioning without any mechanical power by utilizing the low temperature heat as regeneration heat source of an adsorbent. Aiming to enhancement of cold-heat output of adsorption heat pump system, many theoretical and experimental studies have been already conducted. However, adsorption heat pump system still has problems for practical use. Most serious one is that cold heat output per unit volume of adsorption heat pump is much smaller than that of an absorption heat pump ; e.g. the silica gel-water type adsorption heat pump needs more than 4 times as big apparatus volume as absorption heat pump. As one of the solution to this problem, we have develop the automatic adsorbent test equipment, and estimated the new materials of adsorbents for adsorption heat pump from the view of the rate of adsorption. The results were 4 times as fast as that of silica gel-water system adsorption heat pump at a maximum, which approached the available size in the market.
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Shigeru KOYAMA, Keishi KARIYA, Bidyut Baran Saha, El-Sharkawy Ibrahim
Article type: Article
Session ID: 4508
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The performance of low temperature waste heat driven adsorption cooling systems depends on the thermophysical properties of the adsorbent/refrigerant pair as well as the performance of the adsorber/desorber heat exchanger. Therefore, it is important to investigate the local heat and mass transfer phenomena in the adsorber. This study deals with two dimensional numerical simulations to clarify adsorption characteristics in the plate-fin and tube type adsorber heat exchanger during adsorption process using activated carbon fiber (ACF) of type A-20 and ethanol pair. It is found that the cooling capacity can be enhanced by optimizing fin pitch. Simulation results also show that cooling capacity increase with the increasing of fin (ACF) height and the decreasing of fin thickness.
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Yasuhiro KASHIRAJIMA, Takumi SUGIURA, Minoru TAKAHASHI, Shigeo YOKOTA
Article type: Article
Session ID: 4510
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We applied floor thermal storage system using packaged air-conditioner to the office building and evaluated the basic performance and energy consumption. As a result, we confirmed that air-conditioner keeps on operating stably during thermal storage time in case of using simply improved packaged air-conditioner. When the air-conditioner is operating, return air was cooled during coming through ceiling chamber by using thermal storage in slab and the load of air-conditioner was reduced. And, energy consumption of thermal storage system was also reduced compared with standard system.
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Naoki OSAKABE, Ritsu HOMMA, Youichi FUJITA, Toshihiro ASANUMA
Article type: Article
Session ID: 4511
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A high efficient gas fired absorption chiller/heater with auxiliary cogeneration exhaust gas heat and waste hot water heat recovery was cooperatively developed by Hitachi Appliances, Inc. and Tokyo Gas Co., Ltd.. A cogeneration package, which consists of the absorption chiller/heater and a high efficient gas engine, generates electric power and chilled water. The system efficiency of the cogeneration package is more than 90%. It is expected that the package contribute to energy saving, prevention form global warming, and level out the demand for electricity.
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Ritsu HOMMA, Yoshimi TAKEUCHI, Naoki OSAKABE, Youichi FUJITA, Toshihir ...
Article type: Article
Session ID: 4512
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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High-COP energy system driven by city gas, named "Hybrid Gas-Eco" which COP is 2.68 by primary energy base, is developed. The system is consist of high efficient gas engine, high efficient absorption chiller-heater driven by waste heat of the engine, and high efficient centrifugal chiller driven by power generated by the engine. It is expected that the system contribute to energy saving, prevention from global warming, and level out the demand for electricity.
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Kaoru YASUHARA, Masahiko IKEDA, Susumu KIKKOUJIN
Article type: Article
Session ID: 4513
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Removed snow and its site causes serious problem in the heavy snow fall area. This unique air conditioning system uses removed snow as cold heat source. In summer season, it works as cooling apparatus circulating air between room and heat exchanger inside snow storage. Components are only snow storage by removed snow, double tube, heat exchanger and air blower. From winter through autumn 2005, this system has tested. This paper describes volume change of snow storage, air temperature change in systems, effect of cold heat on underground, cooling capacity and environmental load. On trial, cooling capacity is not enough, however, dehumidification is good, therefore this system provide for comfort. In addition, running cost and environmental load are much lower than that of usual air conditioning system.
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Yosuke NAKADA, Kentaro ISHIDA, Yoshinobu NAKAO, Yoichi TAKEDA, Akio OH ...
Article type: Article
Session ID: 4514
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Geothermal power plants are often operated off design point because of the change of ambient conditions, like air temperature, production well and deterioration of the components. For this reason, thermodynamic performance analysis simulator for geothermal power plant was developed. Quantitative evaluation on the influence for overall plant could be performed at the time that outside conditions and performance of plant components varied. By this simulator, power output and variation of exhaust vacuum accompanying with ambient temperature, production well condition and related parameters can be analyzed. This simulator is useful how planning of the plant maintenance strategy and its operation.
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Atsushi AKISAWA, Takao KASHIWAGI
Article type: Article
Session ID: 4515
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The objective of this study is to examine the performance of a solar collector with non-imaging Fresnel lens to concentrate solar irradiation in order to generate higher hot water temperature than conventional solar water heaters. A non-imaging Fresnel lens was designed and manufactured, which had the optical concentration ratio of 13. The lens was mounted on an evacuated tube with a pipe inside. Experimental results indicated that thermal efficiency of infrared rays was slightly lower than that of whole irradiation, and that only infrared rays could produce hot water at about 90 degree Celsius.
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Toshiaki INOUE, Masanori MONDE, Teruki KUWAHARA, Yoshio TERUYA
Article type: Article
Session ID: 4601
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Yasuyuki IMAI, Koji OKAMOTO
Article type: Article
Session ID: 4602
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Improvement of CHF requires that the cooling liquid can contact the heating surface, or a high-wettability heating surface, even if a vapor bubble layer is generated on the surface. From this point of view, an experimental study to investigate boiling condition was performed by use of an ITO glass after a γ ray irradiation environment. The results showed that the number of nucleation site was decreased and diameter of generating bubble was increased after ^<60>Co γ ray irradiated.
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Takashi YAMADA, Toru SHIGECHI, Satoru MOMOKI, Kuniyasu KANEMARU, Tomoh ...
Article type: Article
Session ID: 4603
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Correlating equations for the film boiling heat transfer from a vertical cylinder of finite-length to subcooled liquids were examined and proposed. The overall heat transfer rate around the cylinder was determined by taking into account each convective heat transfer on the bottom, side and top surfaces of the cylinder. The present prediction method was compared with the experimental data obtained by quenching method. The test cylinder used in the experiments are, respectively, 32mm×16mm, 32mm×32mm, 32mm×64mm, 45mm×45mm, 50mm×16mm, 50mm×32mm and 50mm×64mm in diameter and length. The degree of liquid subcooling was varied from 2 to 30K. All the experimental data can be correlated within ±15% by the present prediction method.
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Takahiro ARAI, Masahiro Furuya
Article type: Article
Session ID: 4604
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Experiments were conducted in which a molten copper droplet released into water pool. Spontaneous vapor explosion did not occur when water temperature was 50℃. Spontaneous vapor explosion did, however, occur at a rate of 70%, when water temperature was 20℃. A high-speed video frames explored the stages of vapor explosions: (1) a vapor film was formed and separates the copper droplet and surrounding water, (2) a filament of molten copper grew from the surface and deformed the vapor film, (3) the vapor film collapsed along the filament surface, and finally (4) triggering of vapor explosions occurred from the filament to the whole molten copper droplet. When the filament growth was observed, it triggered the vapor explosion in almost all cases. When not, vapor explosion was not observed and the vapor film was, therefore, stably formed around the molten copper droplet. We concluded that the filament form the molten copper triggered vapor explosion in a highly subcooled water.
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Noriaki INABA, Hiroshige KIKURA, Masanori ARITOMI
Article type: Article
Session ID: 4605
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A phenomenon of subcooled boiling with a bubble condensation is thermal nonequilibrium, and to bring out complicated behavior in a conventional study. But it was clear that the result does not accord with the conventional experimental data and theory, which be adapted to two-fluid model or three-fluid model in forced-convection subcooled boiling. It is the fact that the characteristic of bubble in forced-convection subcooled boiling is not made enough clear. In this study, the object find out that the condensation of bubble in the low quality region gives the two-phase flow, which is photographed by using high speed camera. As a result, the bubble diameter is changed the flow condition and the influence of heat, and the changing of bubble diameter with condensation and a term of condensing bubble change the flow of down stream.
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Tetsuya NISHIDA, Junya ICHINOSE, Kiyohiro MATSUO, Tsutomu NAKAOKA
Article type: Article
Session ID: 4606
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper described of simulation of cooling and refrigerating of the aquatic products by personal computer. The experiments are carried out in the case of with freezing of the aquatic products using "tuna" and "salmon". The value of simulation is compared with experimental results. The simulation prediction agrees with experimental results.
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Shinsuke SUGIMOTO, Kenichiro TAKEISHI, Yutaka ODA, Masanori KUBO
Article type: Article
Session ID: 4607
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Impingement cooling is an extremely effective heat transfer enhancement technique. Though its feature is that heat transfer coefficient is a maximum at the stagnation point and decreases with distance along the plate. This paper shows the result of experimental and numerical study about impingement cooling for promoting heat transfer coefficient on the wall jet region by ribs as a part of enhancing cooling efficiency inside the turbine vanes. The effect of the rib height, the rib location, and the pitch of two ribs are investigated. The heat transfer measurements were performed using the naphthalene sublimation method. The AKN model was found to predict reattachment length correctly, which then resulted in good agreement of the local heat transfer coefficient distributions between experiments and numerical simulations except the stagnation region.
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Takeshi KAJIUCHI, Kenichiro TAKEISHI, Yutaka ODA, Takanori Kumagai
Article type: Article
Session ID: 4608
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The performance of film cooling used for gas turbine first vanes or blades depends on various factors. This paper discusses the effects of film-hole geometry on film cooling effectiveness distributions obtained by experiment and numerical analysis. In experiment, Laser-induced Fluorescence (LIF) has been utilized to measure film cooling effectiveness on the basis of heat/mass transfer analogy. Three-dimensional spatial distributions of film cooling air injected into the boundary layer on flat surface were investigated by using a low-speed wind tunnel. In numerical analysis, film cooling effectiveness was obtained with the standard k-ε model. Comparison of the film cooling effectiveness distribution between experimental results and numerical one shows qualitative agreement.
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Hiroaki OHBAYASHI, Yoichi MASADA, Masanori TAKEUCHI, Niro NAGAI, Kenji ...
Article type: Article
Session ID: 4610
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This research aims to develop temperature control system for a cabinet which is set up in outfield and has heat source inside. Underground heat source was utilized with steel pipes embedded into underground and water as working fluid. The inside of cabinet was cooled the in summer season and warmed in winter season. The experimental results show that this system can favorably control the inside air temperature of cabinet in summer and winter season. The results of numerical simulation using only meteorological data show good agreements with experimental data in summer and winter season. The results of numerical simulation where some parameters such as pipe distance, diameter, and length were changed show the effect of these parameters on performance of the system.
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Taichi FUJISAWA, Yoshiharu AMANO, Takumi HASHIZUME, Toshiyuki HINO
Article type: Article
Session ID: 4611
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Drying of wet wastes is expected to be effective in reduction and recycling of them. However, water-evaporation operations of concentration and drying are typical energy-intensive processes because the latent heat of vaporization of water is quite a lot. Therefore, an unique technology to achieve energy savings is studied. In this system, the output steam generated in drying wet wastes is compressed, and the heat of the steam is utilized to heat the material itself. This paper describes the basic characteristics of this system. Experiments in which water was used as the heated material, availability analyses to estimate which components cause bigger losses, and calculations to estimate the effects of the efficiency changes of each components to the system were conducted.
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Nobuyuki KIMURA, Kenji HAYASHI, Hideki KAMIDE
Article type: Article
Session ID: 4612
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A quantitative evaluation on thermal striping, in which temperature fluctuation due to convective mixing causes high cycle thermal fatigue in structural components, is of importance for reactor integrity. In this study, we performed a parallel triple-jet water experiment along a wall. The material of the wall was changed to acrylic resin, stainless steel and copper in order to evaluate an effect of thermal properties of the wall on the transfer characteristics of temperature fluctuation from fluid to structure. The temperature fluctuation intensity in structure was small as the thermal diffusivity of the wall material was large. Heat transfer coefficient was obtained from the transfer function between temperature fluctuations in fluid and wall. It was seen that the heat transfer coefficient was large as the thermal diffusivity of material was large. Furthermore, the dependence of Nusselt number on Reynolds number was close to the existing correlation.
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Yuuki Matsushita, Hiroshi Sasaki, Katsuhiko Yokota, Kiyoto Motizuki, S ...
Article type: Article
Session ID: 4613
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The vehicle powered by the solar energy is expected to be clean and to make energy savings. In this report, the solar thermal collecting system, which collects the solar energy from the sunlight as energy source of the vehicle and uses Evacuated Double Glass Tubular Collectors and selection-absorption film, was manufactured and tested to evaluate the characteristcs of the collecting the solar energy. Test results present that the solar thermal collecting system needs to improve the construction and the efficiency and clarify the route of heat rejection from the tubes.
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Hidehiko NODA, Noriaki ICHIKAWA, Takashi NOZAKA, Mitsunobu KOWATARI
Article type: Article
Session ID: 4614
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Because of the need of a lot of fuel to maintain the temperature of a green house and a reduction of the cultivatable area, there is little agriculture profit at winter season in cold districts. The experimental study was conducted on the heat transfer when the heat pipes are used as the heating device for the green house. The results show that the overall heat transfer rate will be decreased by using the heat pipe heating. Moreover, the cultivatable area will increase, because of the effect of the radiation heat from the heat pipes.
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Kazuhiro SASAKI, Tsuyoshi KAJITANI, Yoshifumi KOJIMA, Toshihiro TSUJI
Article type: Article
Session ID: 4615
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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For a turbulent natural convection boundary layer in water along a vertical flat plate, the variation of local heat transfer rates is examined by inserting split heat transfer promoters consisting of short flat plates aligned at fixed intervals into the boundary layer. By changing the size and the inclination angle of the promoter, it is recognized that the local heat transfer rate downstream of the promoter locally increased up to approximately 40% as compared to that without promoter. Simultaneous measurement of velocity and temperature are also conducted with a PIV and a thermocouple rake, and the mechanism of heat transfer enhancement is discussed.
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Yasuaki SHIINA, Kota ISHIMKAWA, Makoto HISHIDA, Gaku TANAKA
Article type: Article
Session ID: 4616
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Heat transfer characteristics near the critical Rayleigh number of horizontal fluid layer with thin wires inserted with high porosity above 0.8 and heated from below were studied by an analysis and an experiment. Linear stability theory was applied to obtain the critical value of the convection on the basis of Darcy flow. The analysis showed that Nusselt number near the onset of the convection is similar to the natural convection with packed spheres. The results show that the experimental value of the critical Rayleigh number was higher than the analysis but the differences decrease with decrease in the porosity and that Nusselt number considerably decreases with slight decrease in porosity from unity.
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Masashi MURAKAMI, Akira SAITO, Tetsuya SUMIDA, Sotoji ODAKE, Hiroshi S ...
Article type: Article
Session ID: 4617
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The fluid flow and heat transfer of the natural convection in a horizontal water layer, with heated from below and cooled from above, using water as the working fluid, were investigated experimentally. An experiment was performed for the Rayleigh number (Ra) in the range of 10^8 up to 10^<11>. At Ra>10^7, turbulent large-scale flow was gradually replaced by rising and sinking plumes. As Ra increases further, plumes changed into a three-dimensional vortex which is new flow patterns appeared at high Rayleigh numbers. The three-dimensional vortex released from the thermal boundary layer rapidly mixed with the fluid and transferred a large quantity of the heat to the upper part of the water layer.
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Masahiro SAITO, Akira ISHII, Masataka ARAI, Goro OGIWARA
Article type: Article
Session ID: 4618
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In order to obtain fundamental data for gasification process of plastics, thermal gasification characteristics of plastics compounds containing flame retardant were investigated experimentally. Polypropylenes (PP) with flame retardant, which were composed by Al(OH)_3 or (NH_4PO_3)_n, were decomposed in an image furnace. The gas components produced by the thermal decomposition were measured by means of a gas analyzer. Soluble organic fraction (SOF) component produced during thermal decomposition process was analyzed with a combustion type PM analyzer. In addition, SOF and solid carbon components in the remains after the thermal decomposition were also analyzed by the PM analyzer. It was found that the thermal decomposition temperature increased with decreasing the oxygen concentration. As for the PP with Al(OH)_3, it was considered that PP was completely decomposed and main component of the remains was Al_2O_3 produced by decomposition of Al(OH)_3 even if the surrounding temperature increased up to 900K. As for the PP with (NH_4PO_3)_n, gradual mass reduction continued after rapid mass reduction.
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Thaung Oo, Ken-ichiro Tanoue, Tatsuya Hinauchi, Tatsuo Nishimura, Miki ...
Article type: Article
Session ID: 4619
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Analyzing of slow pyrolysis process of woody biomass and effect of particle size of woody biomass on pyrolysis process has been studied by employing the heat and mass transfer process. The different particles size of the biomass influences on heat transfer rate (Temperature gradient), which affects on the pyrolysis process, the flow rates of generated gases and the concentration of the generated product gases (CO, CO_2, H_2 and CH_4). According to the gas chromatography results, CO_2 and CO of maximum gas yield are obtained at 60min, 220℃ and 80min, 420℃ respectively CH_4 and H_2 of maximum gas yield are obtained at 100min, 550℃ and 120min, 720℃ respectively.
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H. Kawasaki, H. Noda, T. Yabe, N. Baba, T. Nomura, H. Ishikawa, Y. Sai ...
Article type: Article
Session ID: 4620
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The long life test of a Loop heat pipe in Deployable Radiator (DPR) on the engineering test satellites VIII (ETS VIII) are planned. Non condensable gases with working fluid in a thermal control system such as a loop heat pipe affect the precise thermal control and the performance. The non condensable gas can not be completely excluded from the working fluid in the loop. The hydrogen is one kind of the non condensable gas in the loop. The hydrogen is genereted from corrosion reaction in ammonia. We investigats into the generation of hydorogen in the ammonia and an effect of the non condensable gas.
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Hidehiko NODA, Takayuki MASANO, Daichi NAKANO, Satoshi KAMEI, Tomoyuki ...
Article type: Article
Session ID: 4621
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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It is well known that adding 1,4-dioxane into H_2O affects the hydrogen bond of H_2O, the cluster configuration is altered, and the characteristics of H_2O change. Paying attention to this point, saturation characteristics of LiBr-H_2O-1,4-dioxane, which is used as a working fluid of an absorption refrigerator, are studied experimentally. Results show that the saturation temperature of the present solution is lower than conventional solution. Therefore, it is proved that if the present solution is used as the working fluid, a low temperature waste heat of less than 100℃ can be used to manufacture the cold brine for an air-conditioner.
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Miki Shimogori, Hidehisa Yoshizako, Yoshio Shimogori
Article type: Article
Session ID: 4622
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The purpose of our work is to examine the characteristics of coal ash emissivitiy to better understand the heat transfer mechanism through ash deposits on tubes in coal-fired boilers. This paper presents a method for determining coal ash emissivity in high temperature atmospheres and the influence of the ash surface temperature on its emissivity. Emissivity was determined by comparing theoretical radiation intensities with measured value obtained by a shield tube emissometer. An ash sample was heated in an electric furnace during the measurement and the radiation intensity from the sample was measured with a digital pyrometer. Emissivity characteristics of Powder River Basin (PRB) coal ash and bituminous coal ash were examined. The results are as follows: (1) Emissivity of deposited ash increases with an increase in deposit surface temperature. (2) The emissivity of a sample having fused surface exceeds 0.9. (3) PRB deposits have lower emissivities compared with bituminous deposits in the range of the surface temperature from 600℃ to 1100℃.
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Tetsuya HIGUCHI, Yoshiyuki YAMAGUCHI
Article type: Article
Session ID: 4623
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A water-type Stirling engine is replaced the power and displacer pistons with water columns. Therefore, it has no mechanical moving part in its compositions. It is known that resonance tube length influences the performance of water-type Stirling engine, but the effect of resonance tube length upon the performance has not been examined in detail. In this paper a series of experiments was performed with changing the resonance tube length. The result was shown in the relationship between resonance tube length and amplitude of each water column. Furthermore, the experimental result was compared with numerical result of an analysis considering head loss in duct lines and heat exchanges between working gas and heat sources, and the performance characteristic of water-type Stirling engine was discussed.
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Eiji EJIRI, Hiroki TANNO
Article type: Article
Session ID: 4624
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Methanol crossover found in the direct methanol fuel cell was experimentally investigated with a 15-cell stack. Fuel cell performance, fuel crossover quantity and stack temperature were measured while fuel concentration was varied between 1-5%. The results showed that the crossover increased as the fuel concentration increased with an increase of stack temperature. The stack temperature rise resulted in improvement of I-V characteristics and promotion of methanol vaporization. The results also showed that the current efficiency reached to 86% at the maximum in case of 1% of fuel concentration, however, it fell to as low as 40% at the maximum for 5% of fuel concentration. It was also confirmed that much water was consumed to transfer protons from the anode to the cathode.
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