Micro gas turbine systems have been developed for a portable power supply. In this study kerosene sprays with pre-vaporized system for the ultra-micro gas turbine combustor were tested. Fundamental characteristics of the kerosene spray with fuel vaporization on a hot wall were investigated experimentally. A model combustor of ultra-micro gas turbine was used for combustion test of kerosene spray. In the combustion test, an extension tubes were set at the exits of fuel injectors for the enhancement of pre-vaporization of the kerosene spray. The effect of the extension tube on flame stability was discussed. As a result, the blow off limit became wider when the extension tube was set at fuel nozzle exit.

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We have developed a microcombustor which has a porous catalyst layer and investigated the flammability map and combustion characteristics for methane, n-butane and DME. For methane fuel, the flammable area in the lean condition is narrow. On the other hand, for n-butane and DME, the flammable area in the lean condition is wide. This difference is caused by the difference in activation temperature of oxidation. Activation temperature of n-butane and DME is relatively low compared with that of methane, which leads to the fact that the combustion efficiency for n-butane and DME is lower than that of methane. In addition, higher air-fuel ratio at the stoichiometric condition for n-butane and presence of intermolecular oxygen for DME enhance the reaction in the lean condition. These different characteristics of the fuel affect the lower LHV limits, ignition temperatures and combustion efficiencies.

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Wind power generation systems contribute to diversification of energy sources and reduction of dependence on the foreign energy sources as a domestic energy source. And it is possible to achieve conservation of the environment, activation of economy, creation of new jobs, reduction of the environmental load, and energy security at the same time by using wind power generation systems. In this study, field experiment was carried out with trial model of vertical axis wind turbine, and comparison with simulation result was done.

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In this study, two types of experimental wind turbines were tested to compare the performance at low tip speed ratio. One has a rotor with tapered blades designed by the combined blade element and momentum theory less than tip speed ratio 2. The other rotor has inversely tapered blades in which the calculated chord length are applied in an opposite way. Moreover, to analyze the behavior of the air flow around these rotors, the visualization test by PIV has also conducted.

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While global warming has become more deeply concerned, it is vital for Japan, which has world's top energy efficiency, to proactively adopt renewable energy in consumer category to shift from high dependency of fossil fuels. As for such approach, we have made comprehensive analysis and determination for usage of solar thermal energy. Although it is one of the most effective green technology to reduce GHG emission today, number of installation in Japan has been declining as well as its market shrinking causing withdrawal of manufacturer from the division. On the other hand, installation of such equipments in abroad has been growing which tightened competition resulting in improvements of cost performance and technology, and eventually price-reduction. Thus, we have completed verification test of foreign-made solar heat panels on behalf of Ministry of the Environment and examined its usage, economic impact and influence of installation in order to stimulate domestic market of solar heat panel.

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To clarify the mechanism of coupling phenomena such as heat, mass and electric charge transfer in a single-cell polymer electrolyte fuel cell (PEFC), we have measured in-plane temperature distribution in a single-cell PEFC by thermograph under power generation. We have investigated the influence of relative humidity and flow rate of supply gas and gas channel pitch of separator on in-plane temperature distribution and power generation performance. As a result, when the stoichiometric ratio of gas flow rate is set over 1.00 regardless of relative humidity of supply gas, the lower and higher temperature region is observed near the inlet and outlet of cell, respectively. This is caused by the convention heat transfer by excess oxygen flow in gas channel at the cathode. Total voltage is increased and the temperature in observation area is decreased with decreasing the gas channel pitch of separator regardless of relative humidity of supply gas under the experimental condition in this study.

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The authors develop a small and simple steam-reforming reactor in a home-use size for n-dodecane as a heavy-hydrocarbons fuel. Under such a well-controlled condition by a thermal diffuser as the reactor satisfies two target-temperature criteria, the authors measure the inside-temperature profile and the hydrogen-molecule ratio (concentration) R_H2, together with the molecule ratios R_CH4, R_CO and R_CO2 of other main gass components such as CH₄, CO and CO₂, respectively. In addition, the authors conduct theoretical calculations, as well as experiments. As a result, the authors successfully achieve suitable inside-temperature profiles. The effects of the steam-to-carbon molar ratio S/C upon R_H2, R_CH4, R_CO and R_CO2 are shown, experimentally and theoretically. The experimental results agree well with the theoretical ones. Besides, both carbon balance and conversion ratio show high accuracy in experiments.

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Nuclear power plants are required to have especially high reliability and increasingly longer service life. As a contribution to the solution of these issues, an analysis was conducted on steam field-related troubles and their causes based on a data from an online database that tracks troubles at nuclear power plants and the authors' experience. As a result, the reality of piping damage attributed to the two-phase flow of steam and condensate characteristic of nuclear power plants was elucidated. This note introduces preventive measures against piping damage to steam and condensate lines that has been proven effective through actual use in various industries under the following topics: 1) technology for the separation of steam/condensate in steam piping, 2) technology for the discharge of condensate from steam piping, and 3) technology for the measurement, inspection or monitoring of steam and condensate lines.

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Fatigue and creep damage of Ni-base superalloys have been investigated using the electron back-scattering diffraction pattern (EBSP) method. The damage caused by high temperature fatigue test is detected as misorientation, and localize at the surface of damaged specimens. The value of misorientation tends to increase with increasing the fatigue damage. Creep damage is also evaluated as the misorientation, but localized around grain boundaries and interfaces of precipitates. The misorientation has a good correlation with the creep strain. Among some misorientation parameters applied in this study, orientation distribution (OD) shows better sensitivity and relativity to the damage than the other misorientation parameters.

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We have developed the constant incident angle method to inspect pipes by using high power square burst wave in non contact air coupled ultrasonic testing (NAUT). We also succeeded to scan the effective guided wave propagated circumferentially in pipes. This paper describes the optimum frequency, incident angle, the selection of probes and examples of detecting image pictures with the constant incident angle focusing method using focus probe.

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To detect stress corrosion cracking (SCC) and evaluate its depth on the surface of Ni-base alloys, a microwave microscope was employed. An open-ended coaxial line sensor was used to increase the spatial resolution. The working frequency was 110 GHz and the standoff distance between the sensor and the sample was 60 μm. The shape of SCC was obtained by microwave imaging. By measuring the amplitude of reflection coefficient, detection of SCC was achieved. To evaluate SCC depth, the attenuation constant of microwave in the crack was decided by comparing the measured microwave signal with the depth of a reference SCC obtained by destructive testing. Finally, the distribution of the depth of another SCC was evaluated by the proposed equation with the obtained attenuation constant.

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Sodium reacts chemically with water in case of unexpected heat transfer tube failure in a steam generator (SG) of sodium-cooled fast breeder reactors (FBRs) and exothermic reaction produces reaction field with high temperature and high corrosive action (sodium-water reaction). Adjacent tubes are damaged due to erosive and corrosive environment of the reaction field (wastage). Therefore, it is integral to evaluate the sodium-water reaction phenomena with high accuracy for the safety assessment of FBRs. For the purpose of understanding the wastage mechanism, an experiment was carried out in which sodium hydroxide (NaOH) as the main reaction product collided with the tube material under high temperature conditions to simulate the reaction field. We confirmed that the erosion-corrosion rate of tube material has a tendency to increase as the temperature and velocity of NaOH are raised.

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Numerical simulations for a T-pipe consisting of a rectangular duct for main stream and a circular pipe for branch stream were performed to investigate relation between large-scale eddy structure formation in the mixing area and temperature fluctuation generation on the wall. Moreover, the numerical simulation to investigate thermal interaction between fluid and structure were conducted. Experimental results of temperatures at 2mm from the wall in fluid, on the wall and at 3mm inside from the wall in structure were compared with those of the numerical results. The numerical results indicate that the fluid-structure thermal interaction is necessarily considered for thermal fatigue estimation in the thermal striping phenomena.

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A computer program called SERAPHIM has been developed to calculate the multicomponent multiphase flow involving the sodium-water chemical reaction in a steam generator of sodium cooled fast reactors. In this study, numerical analysis of supersonic gas jets into liquid pools with or without chemical reaction was performed to validate the numerical methods. As validation for a non-reaction problem, the visualization experiment on the horizontal supersonic air jet into the water was analyzed. The behavior of the jet and the horizontal penetration length were reproduced very well. On the other hand, the experiment on the vertical supersonic chlorine jet into the Na-NaCl mixture was analyzed. The numerical result showed that the injected gas disappeared at a certain height. The estimated plume length showed good agreement with the experimental data. The numerical methods were found to be applicable to the multiphase flow with the supersonic gas jets and the chemical reaction.

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To evaluate gas entrainment (GE) phenomena in a large-scale sodium-cooled fast reactor, the authors are developing a high-precision numerical simulation algorithm for gas-liquid two-phase flows based on a volume-of-fluid methodology. In this simulation algorithm, the PLIC (Piecewise Linear Interface Reconstruction) algorithm is employed to achieve accurate interface-tracking. Moreover, physically appropriate formulations have been conducted on gas-liquid interfaces to eliminate unphysical behaviors. Thanks to these improvements, it is confirmed that the developed simulation algorithm can reproduce the GE phenomena in a simple experiment. In this study, the simulation algorithm is applied to a real-scale GE test to check the applicability of the algorithm to the GE phenomena in the fast reactor. The mesh resolution and boundary conditions are considered carefully to be suitable for the numerical simulation of the two-phase flow around inlet and outlet pipes. As a result, transient behaviors of the vortical flows around the pipes and the accompanied GE phenomena are simulated well. In particular, the origin of the flow which induces the GE phenomena is showed clearly. Finally, from the investigation of a lot of GE phenomena observed in the simulation result, it is verified that the GE phenomena by relatively strong vortical flows are important in terms of the GE suppression in the fast reactor.

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A conceptual design study of Japan Sodium-cooled Fast Reactor (JSFR) is in progress as an issue of the “Fast Reactor Cycle Technology Development (FaCT)” project in Japan. JSFR adopts a selector-valve mechanism for a failed fuel detection and location (FFDL) system. The Selector-Valve FFDL system identifies failed fuel subassemblies by sampling sodium from each fuel subassembly outlet and detecting fission product. One of the JSFR design features is employing an upper internal structure (UIS) with a radial slit, in which an arm of fuel handling machine can move and access the fuel assemblies under the UIS. Thus, JSFR cannot place sampling nozzles right above the fuel subassemblies located under the slit. In this study, appropriate sampling method for indentifying under-slit failed fuel subassemblies has been developed by water experiments.

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An advanced two-fluid model has been developed in Japan Atomic Energy Agency (JAEA). In this model, an interface tracking method is combined with a two-fluid model. In this procedure, liquid clusters and bubbles larger than a computational cell are calculated using the interface tracking method, and those smaller than a cell are simulated by the two-fluid model. A turbulent dispersion force term is one of the most important constitutive equations for advanced two-fluid model. We have developed the new model for turbulent dispersion force and verified the developed model using the 3-dimensional two-fluid model code ACE-3D, and the comparisons between the results of the analyses and air-water two-phase flow experiments in 200 mm diameter pipe. In this study, to verify the applicability of developed model for middle diameter vertical pipe, we compared between the analyses of results and air-water two-phase flow experiments in 38 mm diameter pipe.

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One of the strategies of cost reduction of nuclear power generation is increase of power outputs. In order to achieve increase of power outputs of a Boiling Water Reactor (BWR), it is extremely important to evaluate coolant flow in a lower plenum of a BWR. Although the simulation by a CFD code is helpful to predict the coolant flow in a lower plenum, experimental data to verify the simulation results are not enough, and the simulation results considerably depends on models. Hence, the present study is focusing on the establishment of the benchmark of CFD code by using the visualization method in a lower plenum. The objective of the present study is to clarify the flow structure of a lower plenum in detail, and to investigate effects of complicated flow structure of lower plenum on core inlet flow. We constructed a 1/10 model of a lower plenum to measure velocity profiles with LDV and PIV. And differential pressure of the lower plenum was measured with differential pressure instrument. In the experiment, it turned out that flow structure of the lower plenum vary depending on experimental condition.

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The purpose of this study is to develop the superheated steam generator using the tubular flame. The tubular flame is formed in a rotating flow field by injecting the air-fuel mixture tangentially into the cylindrical chamber. The tubular flame consists of an inner hot gas core of burning gas and an outer region of unburned mixture. The water tube located at the hot gas core can be used as the superheater of the superheated steam generator. This paper focuses on the stability of the tubular flame and related heat transfer characteristics of the water tube. Subsequently, the prototype of superheated steam generator was made. The thermal efficiency is 86 % based on HHV at the hot-water supply mode.

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Recently, development of a small and high efficient heat exchanger, which is utilized in a fuel battery and a heat pump system for CO₂ refrigerant and so on, is strongly required. In author's previous study, a prototype of stacked high pressure resistance microchannel heat exchanger manufactured with diffusing bond technique has been proposed. In the present study, the objective is to reveal flow and heat transfer properties of this microchannel heat exchanger when water and vapor are employed as low- and high-temperature fluids, respectively. Pressure drop and heat transfer rate are measured as flow and heat transfer properties, respectively. As the results, it is identified that the cross-flow heat exchanger operates as a condenser with small pressure drop of less than 60 kPa. Heat transfer rate of it is approximately 7500 W despite the weight of 240 g. Counter-flow heat exchanger indicates high heat transfer properties as heat transfer rate of approximately 9000 W.

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For continuing nuclear energy as one of basic power sources, it is necessary to strengthen the supply stability, moreover, build nuclear fuel cycle which reprocesses spent fuel produced from nuclear power plant, and reuses uranium and plutonium collected. In the research field of reprocessing process of this cycle, recently, a new type centrifugal extractor using Taylor-Couette vortex flow is studied for improving the extraction efficiency. By the way, since the unstable vortex formation causes fluctuations in extractor's torque and chemical reaction time, the understanding and control of this kind of vortex flow are necessary. Especially, for the practical usage, it is important to investigate the characteristics of Taylor-Couette vortex flow with a through-flow. In this study, we investigated the effects of through-flow on Taylor-Couette vortex flow with use of an Ultrasonic Velocity Profiler (UVP), which is capable of visualizing the flow dynamic characteristics. Under through-flow condition, we found that vortices are drifting in the direction of through-flow and their motions depend on Reynolds number of through-flow.

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Flooding is one of very important designing factor of actual boiling system with counter-current two-phase flow. Consequently, many investigations have been conducted, but most of those investigations have been done with large diameter tubes. Thus, flooding characteristics under a small diameter tubes (I.D. < 10 mm) have not been fully understood so far. In this study, flooding experiment was conducted by using air-water adiabatic system with glass and acrylic resin tubes of 5 mm in inner diameter. As results, tube material did not influence on the critical flooding and flow reversal, but influenced on the flooding velocity and flooding pattern transitions. These flooding velocities have been estimated by using Wallis's correlation.

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This experimental research concerns an air-bubble-jet flow in water. The authors try to conduct the measurements of the flow applying a three-dimensional particle-tracking-velocimetry (3D-PTV) technique, in order to show both air-bubble and liquid (water) velocities. As tracers, we regard air bubbles in bubble-velocity measurements, and we regard polyethylene particles suspended in the liquid in liquid-velocity measurements. Then, we visualise the three-dimensional motions of air bubbles and ambient liquid. As we record stereo images using two high-speed video cameras, we can get timely-consecutive information of air-bubble and ambient-liquid motions. As a result, we quantitatively reveal the three-dimensional instantaneous motion of an unsteady bubble-jet plume from a simple air nozzle.

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Experimental investigation of the inner diameter in the thermoacoustic cooling system was carried out to confirm the effect for energy conversion efficiency. We carried out an experiment by using the thermoacoustic cooling system with 3 type inner diameters (24 mm, 42 mm, 100 mm). As results, acoustic power and a phase difference between sound pressure and particle velocity was varied. Moreover, it was confirmed that energy conversion efficiency in it changed with the variety of inner diameter. Energy conversion efficiency in it with inner diameter 100 mm was best of all. It is considered that a factor of improvement of energy conversion efficiency was change of phase difference between the sound pressure and the particle velocity.

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SATOYAMA CLUB demonstrated of a new energy system aimed for utilization of the woody biomass in the Expo '70 Commemorative Park (Suita-shi, Osaka) from 2005. And, in SUCTION, the development of the indirect heating type Stirling engine that used thermal oil for the heat transportation is in a good results. 1kW and 10kW class engines have been developed using a heat source of 300 degrees Celsius. From 2008, the 1kW class engine has been installed on a wood biomass boiler. The hot water from the boiler is used for a foot spa and the electricity is used for charging batteries of electrical bus. It is demonstrated now in the Expo '70 Commemorative Park.

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Woody biomass such as the thinned wood is widely distributed in the mountain-ringed region and the field, and it is difficult economically to collect and to transport it. Therefore, small-scale power generation is suitable in many cases. Development of small-scale power system based on the biomass gasification is under going. But because of so complicated system and high cost, the commercialization is not progressing as expected. Small-scale system which has high thermal efficiency and low cost is requested. So, in this study we develop small-scale power system, in which stirling engine power system is combined with biomass combustion furnace. We aim at high thermal efficiency and low cost of the biomass power system through this development. In this paper, our field tests of a 30kW-class stirling engine is reported. Moreover, the demonstration plant of stirling engine system using biomass is intrduced and typical results of the field test of the plant are reported.

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In the sea around Japan, there is the region of sufficient environment of CO₂ hydrate generation. When liquid CO₂ is injected in those regions, choking of liquid CO₂ flow is expected to occur due to CO₂ hydrate generation in pipe arrangement or seabed. The purpose of the present study is to evaluate the influence of CO₂ hydrate on the flow of liquid CO₂ when liquid CO₂ injected in a porous media as simulating seabed. In order to reveal the influence of CO₂ hydrate, differential pressure is measured under both condition of CO₂ hydrate generated and not generated. As the results, in the case of the hydrate generation environment, it is identified that differential pressure became large compared with the case of no-hydrate generation. In the upstream part, the differential pressure became large compared with the downstream region. It is suggested that flow resistance occurred due to choking of CO₂ hydrate membrane on the porous media. Friction factor is also compared with the Ergun's equation which is proposed for single-phase flow in a porous media. The measured friction factor is larger than the value from Ergun's equation.

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Particulate matter (PM) trapping and oxidation in regeneration on the surface of a diesel particulate membrane filter (DPMFs) were investigated in detail using an all-in-focus optical microscope. The DPMF consists of two-layer sintered filters, where a SiC-nanoparticle membrane (made from a mixture of 80 nm and 500 nm powders) covers the surface of a conventional SiC filter. Through a visualization experiment, it was shown that PMs were trapped homogeneously along fine surface pores of the membrane's top surface, whereas in the regeneration process, the particulates in contact with the membrane may have been oxidized with some catalytic effect of the SiC-nanoparticles. The oxidation temperature of particulate trapped on the SiC-nanoparticle membrane was lower than that on the conventional diesel particulate filters (DPFs) without a rare-metal catalyst. The activation energy of reaction on the nanoparticle membrane became lower than that on the conventional SiC-DPF without catalyst. Consequently, the SiC-nanoparticles membrane filters had some catalytic activity similar to that of the conventional catalyst DPF.

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The present study is concerned with experiments of the movement of a liquid droplet in a horizontal circular pipe exposed to air flow injected from a vertical pipe. A water droplet is exposed to air flow on a curved wall. The relation between air flow and the standing position of liquid droplet is examined experimentally. In the case that relative intensity of turbulence of gas flow at the standing position is less than 0.18-0.19, the gas velocity at the standing position agrees well with the analytical value calculated by the equilibrium between the force of adhesion to the wall and the dynamic pressure due to gas flow. As the intensity increases, the gas velocity at the standing position decreases. The relation between the intensity of turbulence and the behavior of a liquid droplet is also discussed statistically.

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In the first report, we investigated the characteristics of mean velocity such as the changes in mean velocity component profiles, and half-widths (b_1/2) of the mean velocity profile in the downstream direction. In our second report, we investigated turbulence characteristics such as turbulence intensity, Reynolds shear stress, and intermittency of turbulence. We carried out all experiments thus far under the condition that the distance between the nozzle and hood is constant. In this third report, we have experimentally investigated the above flow characteristics of Push-Pull flow under the condition that the distance between nozzle and hood (L) is variable. Then we operated the Push-Pull local ventilation systems at each leakage-limit flow ratio with three different distances between the nozzle and hood, respectively. As the result, the existence of a region where the flow of air accelerates in the downstream direction became clear near the hood as the distance L became longer. In this region, an increase rate of half-widths in the downstream direction near the hood became smaller. At the same time, the flow of air and the velocity of entrainment near the hood rapidly increased. Also, turbulence intensity in the axial direction becomes smaller in the downstream direction as the distance L becomes greater. The value approaches that of the intensity in the lateral direction. Reynolds shear stress decreases in the downstream direction.

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The backlayering phenomenon is the most important behavior in a tunnel fire. However, the backlayering distance, which is the upwind propagation length of thermal fume, has not been systematically examined so far. The backlayering distance of thermal fume in a tunnel fire was examined by using large-scale model tunnel in this study. Various longitudinal ventilation velocities and four kinds of fire size were set as experimental parameters. The following conclusions were obtained. A new expression was proposed to estimate the non-dimensional backlayering distance L_b / H by using the non-dimensional heat release rate Q^* and Froude number Fr. L_b / H = a (Q^*1/3 / Fr) - b. The included constants a and b in this expression are obtained from experimental data by using the least square method. The proposed expression can predict not only the backlayering distance but also the critical velocity. This expression was applied to the experimental results of other researchers.

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Direct numerical simulations of the airflow over periodic superposed wave train with different wave lengths and phase velocities were carried out to investigate effects of airflow perturbation due to long waves on momentum transfer from the airflow to short waves. Both the short and the long waves travel in the streamwise direction of the airflow. The results show that the short wave-correlated component of the mean velocity and the pressure are affected by the long waves. The effects of the long wave on the momentum transfer from the airflow to the short waves depend on the wave ages of the short waves. For the low wave ages, it is guessed that the variance of the shear stress in the inner region due to the long wave-correlated momentum flux effects on the momentum transfer. On the other hand, for the middle wave ages, phase shift of the cat's eye caused by the mean velocity variance due to the long waves would effect on the momentum transfer.

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The critical nozzle flow meter was developed for high-pressure hydrogen gas flow measurements, and its characteristics was experimentally examined with hydrogen gas at the pressure up to 70 MPa. The results show that the critical back pressure ratio is 0.93-0.95 under the above pressure conditions, and its discharge coefficient has a curious behavior which the discharge coefficient decreases with increasing the Reynolds number over 40 MPa. Also, tests filling hydrogen gas into the storage tank of fuel cell vehicle was conducted under 35 MPa condition with the developed flow meter, and the high efficiency of this flow meter was confirmed even on practical uses.

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Main steam control valves in power plants are required to operate under wide ranges of valve openings and pressure ratios. In the present paper, experimental and numerical investigations are conducted with rigid and flexible valve head supports in order to clarify mechanisms of valve head vibrations caused by unsteady flows around the valve. Results obtained with the rigid support without valve head vibration show that the unsteady flow around the valve head causes pressure fluctuations on the valve head surface with random and impulsive wave forms. With flexible support, the valve head vibrates at near the natural frequency of the valve head support system and the vibrations are excited around the operation condition where the pressure fluctuation becomes large with rigid support valve head. When the valve head vibration becomes large, the pressure fluctuation becomes periodic with the same frequency of the valve head vibration. The numerical result shows that the response of the separated jet delays behind the valve head motion. As a result, the lateral fluid force fluctuations on the valve head provide negative damping on the vibration.

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The aerodynamic characteristics of airfoils have been researched in higher Reynolds-number ranges more than 10⁶, in a historic context closely related with the developments of airplanes and fluid machineries in the last century. However, our knowledge is not enough at low and middle Reynolds-number ranges. So, in the present study, we investigate such basic airfoils as a NACA0015, a flat plate and the flat plates with modified fore-face and after-face geometries at Reynolds number Re < 1.0×10⁵, using two- and three-dimensional computations together with wind-tunnel and water-tank experiments. As a result, we have revealed the effect of the Reynolds number Re upon the minimum drag coefficient C_Dmin. Besides, we have shown the effects of attack angle α upon various aerodynamic characteristics such as the lift coefficient C_L, the drag coefficient C_D and the lift-to-drag ratio C_L/C_D at Re = 1.0×10², discussing those effects on the basis of both near-flow-field information and surface-pressure profiles. Such results suggest the importance of sharp leading edges, which implies the possibility of an inversed NACA0015. Furthermore, concerning the flat-plate airfoil, we investigate the influences of fore-face and after-face geometries upon such effects.

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In the biomass plastic of which the fluidity is low, the mold design becomes for one of the key technology to realize resin moldings of various shapes. V-shaped biaxial cutting work was adopted in order to form micro-structure with fractal pattern at 10μm on the mold surface. The contact angle of the biomass plastic molding was increased in 20.6° and the water repellency was drastically improved.

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This study investigated the characteristics of cell performance degradation, decline of component performance and changes in the properties of MEA materials caused by repeated cold starts under subzero conditions of -30 deg. C. It was made clear that decay of function appeared mainly in the cathode by increase in proton conductive impedance and reduction of reactivity of electrode catalyst. Among the cathode components, an increase in proton conductive impedance in the cathode electrolyte was dominant. Furthermore by the application of Ion Chromatography and newly applied Proton Induced Gamma-ray Emission Method in fluorine measurement in the off-gas drain a decomposition of electrolyte was dominant in cathode catalyst layer. A decrease in fluorine in the cathode electrolyte measured by ¹⁹F-NMR confirmed the decomposition.

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The development of a polymer electrolyte fuel cell (PEFC) without external humidification is one of the most important issues to increase total efficiency and reduce cost. In the present study, we have developed hybrid pattern gas channels consisting of interdigitated and serpentine gas flow channels for PEFCs. The effects of gas flow channels at the anode and cathode on PEFC performance without external humidification were investigated. The PEFC performance was significantly deteriorated when a conventional triple serpentine channel was used at both the anode and cathode. However, when using the serpentine hybrid flow channel in the cathode, the performance was improved because of preventing the water from exhausting from the cathode. Moreover, the gas which flowed through the low pressure serpentine flow channel in the serpentine hybrid flow channel possibly promoted spreading water vapor over the whole active area. The triple serpentine flow channel in the anode was indicated to enhance spreading the water to whole of active area. Accordingly, IR overpotential was decreased and thereby PEFC performance was enhanced.

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An useful method for a spectral evaluation of a radiation energy was developed for far infrared heaters. The system consists on a simple radiometer and two band-pass filters; vitreous Silica and Silicon, which have different transmission. Numerical simulations with Microsoft Excel made sure this method works well. The experimental data obtained by this method gave the fact that a far infrared type heater radiates enough energy in a far infrared region even at high temperature as much as a black body does. It means a far infrared type heater can work effectively enough at high temperature for industry heating. This method can classify a type of a heater with the ratio of a near infrared energy and a far infrared energy in practical use. By using this data, the authors also proposed a simple identification method of spectral emissivity of far infrared heater made of ceramics. This inverse method could determine approximated values for real heaters.

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A boiling explosion occurs when a liquid impinges on a surface whose temperature is kept at higher than Leidenfrost temperature. This phenomenon is theoretically analyzed by applying a new model proposed by Monde et al.. In this model, a characteristic liquid cluster at the boundary is considered and the condition of homogeneous nucleation generation is characterized at a moment when the average temperature in the liquid cluster reaches the condition of ∂T_avg/∂t = 0, that is energy consumption due to bubble nucleation and subsequent growth balances transient external energy deposition, at which bubble generation and growth in the cluster cause the liquid sensible energy to decrease. The occurrence of the homogeneous nucleation generation has been studied by applying the present model for various conditions of steel quenching with impinging water jet at atmospheric pressure. The model shows that homogeneous nucleation generation does not occur at surface temperatures below 335 °C during quenching steel surface with water (20 °C). The results obtained in the present study might be helpful in better understanding the establishment of steady solid-liquid contact as well as the cooling phenomena that occur in the early stages of jet impingement quenching.

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