Lithium salts solutions are used activate agency at absorption refrigerating machine. However, as an influence factor of the nucleate pool boiling heat transfer characteristic, which governs the performance of absorption refrigerating machine, the extensive knowledge of concentration and pressure is not fully acquired yet. This research experimentally brought out the nucleate pool boiling heat transfer characteristics under pressurization to the high concentration aqueous solutions of lithium chloride and lithium bromide

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In order to develop a compact and high efficient absorber used in absorption refrigeration system, a mixing type absorber has been proposed which is composed of an ejector and a cooler. Compared to conventional methods, mixing type absorber first mixes absorbent with refrigerant and then moves to the cooling process. The mixing process affects the performance of mixing type absorber significantly. In this research, an attempt to evaluate the absorption rate affected by the flow pattern after the nozzle was presented.

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For the absorption of water vapor into the aqueous lithium bromide aqueous solution, eight-carbon alcohols such as 2-ethyl-l-hexanol have been commonly used to improve the absorption process. However, as additives six-carbon and seven-carbon alcohols have not been tested experimentally very much. In the present study, absorption of water vapor into the 62 wt% lithium bromide aqueous solution with several additives such as 4-methyl-2-pentanol, 2-ethyl-l-butanol, 1-hexanol, 2,4-dimethyl-3-pentanol, 4-heptanol, 2-heptanol and 1-heptanol were investigated by using a simple stagnant pool absorber. Besides using the conventional method for adding additives into LiBr solution by liquid phase, the method for adding by vapor phase also was experimented. The result showed that the method for adding by vapor phase is effective for the absorption of water vapor into the aqueous LiBr solution.

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This paper presents the experimental results of Reheat Two-Stage Adsorption Cycle in terms of Specific of Cooling Power (SCP) and Coefficient of Performance (COP). The performance of the cycle was evaluated under different operating conditions such, as heat source temperature and cycle time setting. The experimental result shows that cycle performance is influenced by driving heat source temperatures as well as cycle time. The experiment result (in term of SCP and COP) obtained from the Reheat Two-Stage, Single-Stage, and Two-Stage Cycle are also compared and discussed.

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By installing the additional condenser on the existing air-conditioning machine for R22, a more effective heat pump system could be operated with R134a. This heat pump system could also be operated at high and low ambient temperature. It was proved that COP was improved by 10% when operating with R134a and that the air-conditioning machine could be operated when the temperature exceeding 50℃. It was also shown to be able to prevent frost on the outdoor unit for heating operation.

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This report is concerned with an experimental study of freezing enhancement of water saturated in the weavless aluminum fiber layer (WAFL) around a cooling pipe. It was seen that the freezing amount of water in the WAFL more increases about 2.5 times compared with that of around a bare pipe without the WAFL.

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Operating condition of ambient temperature and humidity for the evaporative cooling system with self-supplied water was examined experimentally. Since dehumidified air was humidified again with self-supplied water through the humidifier, Operating condition was deeply dependent on the humidity and temperature of ambient air. It is found that high humidity and high temperature were helpful for the desiccant cooling with self-supplied water.

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Clean coal technologies, especially in large-scale pulverized coal-fired power stations in Japan, have already realized quite low emissions of NOx, SOx and fly ash particles, and a remained problem for the protection of global environment is how to suppress CO_2 emissions. For that purpose, in this paper, a new system integration toward CO_2-free clean coal technology combined with hydrogen energy and CO_2 sequestration is discussed based on the present status and future prospect of various related technologies including coal combustion with CO_2 recovery, highly sophisticated utilization of hydrogen and CO_2 sequestration.

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This paper describes functional use of water electrolysis in the future energy system using hydrogen as energy carrier. It mentions that the conversion efficiency from electricity to hydrogen in PEWE (Polymer Electrolyte Water Electrolysis) may become close to 100% in near future, and may even exceed 100% when external heat will be given to the electrolyzer, though a technical breakthrough in R&D of anodic electrocatalyst is required for. The role of water electrolysis among many hydrogen production technologies from fossil fuel and renewable energy is characterized for providing efficient energy conversion means from electricity to hydrogen. Efficient water electrolysis could be applied to the following energy systems : A) power load levering in nuclear power plants through producing hydrogen, B) refueling stations for fuel cell vehicles, C) leveling or storage of intermittent renewable energy (PV and wind). In addition, efficient reversible electrolyzer (unitized regenerative fuel cell) could be applied to system with power load levering function to supply electricity, heat and hydrogen gas to urban building facilities.

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On board hydrogen storage and transportation of hydrogen are one of key issues to introduce hydrogen energy to the society. Hydrogen storage materials provide hydrogen storage means that work at ambient hydrogen pressure and temperature. Controlling of the reaction heats is needed for application of hydrogen storage materials. Mechanism of hydrogen storage includes adsorption on the surface, absorption into the solid and chemical reaction between materials and hydrogen gas. Hydrogen absorbing alloys, alanates such as NaAlH4 and some kinds of carbon materials are explained.

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Metal Hydride is suitable in safety and compact for decentralized fixed hydrogen storage and the boil off hydrogen collect.LaNi_<4.7>AL_<0.3> hydriding and dehydriding near normal temperature and pressure was adopted and measured basic physical properties value. Afterwards, the hydrogen storage experiment was made with changing pressure and temperature. In simultaneous experiment with charging and discharging, outflow hydrogen rate was controlled for about 3 hours by maintaining inflow hydrogen rate (0.8NL/min). Considering the hydrogen supply system to the fuel cell for 1000 families' power supply, the total energy efficiency was 76%, and effect of CO_2 reduction became 4167 kg-CO_2/day.

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Reduction of the cooling loss by the heat transfer from the burning gas to the combustion chamber wall is very important for improving the thermal efficiency in hydrogen combustion engines. The previous research by the author proposed the direct injection stratified charge for a technique to reduce the cooling loss in hydrogen combustion and shown its high effect of the cooling loss reduction by experiments in a constant combustion chamber. However, it is known that a reduced cooling loss reduction does not always lead to an improved thermal efficiency in conventional gasoline engines because of an increased exhaust heat loss. This research analyzed the relation between the cooling loss and the exhaust loss in a hydrogen combustion engine.

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When PEFC is operated at high power, a drop of water is appeared in the channel and the gas diffusion layer. And the gas supply is blocked, and then the cell voltage decreaces and becames unstable. So we are developing a PEFC numerical code considering gas-liquid two-phase flow to elucidate the problem of water. In the numerical model, the water vapor is condensed when the vapor perssure exceeds its saturation vapor pressure. In this report, we show the outline of the code and an example of the saturation distribution in cathode.

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In order to clarity the characteristics of water transport at gas diffusion layer (GDL) in stack of polymer electrolyte membrane fuel cell (PEMPC), in this paper, a measurement for the effect of porosity, plate thickness and water temperature on moisture transport from constant temperature water to dry air through porous media having very small pores was performed. In addition, in order to evaluate the degree of moisture absorption of air, a parameter called the humidity absorption rate was introduced. It was shown that the humidity absorption rate decreases with respect to the increase of the air velocity and water temperature.

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The polymer electrolyte fuel cell (PEFC) is expected as one of the next power generation system. Although high-performance PEFC is expected, understanding of mass transfer is not enough due to the complex structure of PEFC. So it is very important to investigate the mass transfer inside the porous gas diffusion layer. We calculated the distribution of water concentration to simulate water transfer in PEFC cathode with porous gas diffusion layer. We used lattice Boltzmann method (LBM) to calculate the flow and water transfer in porous media, because LBM is easy to set boundary conditions. From these result, we suggest the way to estimate the conditions that PEFC works without flooding and concentration overvoltage.

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High performance operation of polymer electrolyte fuel cell (PEFC) is limited by water condensation in a cathode gas diffusion layer (GDL) because oxygen transport to reaction sites is blocked. In this study, we observe removal behavior of condensed water in a cathode of PEFC using a long-distance microscope and discuss its characteristics. Furthermore, the structure of cathode electrode for controlling water transport is proposed in order to improve cell performance. It is shown that water removal is promoted by using the cathode GDL with a slit and cell voltage is increased.

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Described were the overview of the performance-estimation models for a propulsive pulse detonation engine (PDE), and the performance of the actual flight model of a pulse detonation rocket engine (PDRE-FM). As the performance-estimation models, the wave-dynamics model and the thermodynamics model were touched on. Furthermore, the homogeneous-dilution model of a partially-fueled detonation tube was introduced. The performance of the actual PDRE-FM was analyzed by using the homogeneous-dilution model and the thermodynamics model. It was found that the measured specific impulse of the actual PDRE-FM was reasonable.

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Performance analysis of the Pulse Detonation Rocket Engine (PDRE) is numerically conducted focusing on partially filled system. Initial explosives, inert gas species, tube fill fraction, and equivalence ratio are chosen as parameters to clarify their effects on the performance of PDRE. The simulation results are compared with previous studies that used several explosives, and agreed well with them. The simulation results indicate that the initial mass fraction of explosive to the total mass is the dominant factor for the normalized I_<sp> under arbitrary conditions. We newly propose the partial fill model to predict the performance of partially filled PDRE.

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The pulse detonation engine (PDE) has recently become recognized as a possible new aerospace propulsion system. The PDE system has high thermal efficiency because of its constant-volume combustion and its simple tube structure. We are now constructing a simple PDE system, an ethylene-oxygen single-tube pulse detonation rocket (PDR), in order to verify that the PDR produces sufficient thrust performance for its application to rocketry even though it uses an intermittent fuel supply system and has a very simple structure. The PDR-FM is operated for three cycles at 10-12.5 Hz in frequency. Liquid ethylene (312K, 250g), oxygen gas (10MPa, 240g), and helium gas (15MPa, 8g) are the fuel, oxidizer, and purge gas, respectively. We measure thrust using a load cell coupled with a spring-damper system and directly measure momentum using a high speed video camera. From these experimental results, we found that effective specific impulses were almost identical to the partial filling model proposed by Endo et al. The maximum thrust and effective specific impulse reached 233.9 sec and 345.1 N, respectively, in the present experiment.

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We will present the outline of JAXA's flight experiment of the hypermixer scramjet engine planned for 2005. The principal aims of this flight experiment are 1) to clarify if the ground developed technique for supersonic mixing and combustion enhancement using streamwise vortices can work well in the real flight conditions, and 2) to calibrate the experiments of the High Enthalpy Shock Tunnel (HIEST) by the flight data. The scramjet engine consists of two symmetrically arranged engines. One engine is installed with a hypermixer injector to generate six pairs of streamwise vortices, while the other engine has a backstep injector that generates no streamwise vortices. Fuel is gaseous hydrogen sonically injected at 12°. The engine will be launched by small two-stage rocket using HyShot developed by University of Queensland. Engine data will be obtained at supersonic combustion mode throughout the altitude 34〜23 km at the flight Mach number 7.6.

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The flame structure in unsteady counterflow premixed flame is investigated by numerical simulation using detailed chemical kinetics. The methane-air premixed gas and air are spouted from lower and upper planes, respectively. Fuel lean mixture (equivalence ratio is 0.75) is considered in this study. The spout velocity u_0 is varied in a sine function. The influences of average velocity u_m and frequency f in the spout velocity on flame structure are examined. The unsteady characteristics of flame structure are organized by a progress variable defined by mass fraction of oxidizer at flame front C_q and its gradient at flame front ∇C_q.

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A high emphasis is placed on disposal of waste gas from plant because of rise of environmental consciousness. A catalytic combustion deodorizer that has an advantage on the running cost is getting a lot of attention. This work reports numerical simulation of catalytic combustion of CR_4/air mixtures on palladium catalysts in honeycomb used in deodorizer. The numerical model has the elementary reaction kinetics considering nine surface chemical species. As the result, details of catalytic combustion in a channel - temperature and mole fraction in the gas phase, temperature and heat release rate at the catalyst, -are obtained.

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Decomposition of Methane Hydrate is studied numerically. Global one-step irreversible reaction model is applied for melting Methane Hydrate and its Arrhenius type of temperature dependency. Two-dimensional, time-dependant phenomena in the cold Methane Hydrate block are simulated. As the time goes by, local temperature increases due to thermal conduction and then the decomposition of Methane Hydrate starts, which discourages the rise of the temperature because of the endothermic reaction.

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The propagation characteristics of premixed flame in a narrow tube with swirling flow have been examined by the numerical calculation. The flame is classified into three configurations for angular velocity and tube radius as follows : For smaller angular velocity, when the inlet velocity is small, the flame is able to stand only near the upstream boundary, and the flame reaches tube wall in the downstream. When the inlet velocity becomes larger, the flame blows off. For larger angular velocity, the flame is stable, but the flame does not reach tube wall so that the unburned mixture flows out. For intermediate angular velocity, the flame oscillates in the narrow tube.

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Effect of gravity direction on stability of small spherical diffusion flame (so called 'microflame') is investigated numerically. In this paper, microflames under normal gravitational field and reversed gravitational field are compared. The flame under reversed gravitational field can establish more stably. Here stability means it can establish under lower flow rate. When the microflame is reversed, the way of oxygen flow differs from under normal gravitational field. There are two distinct features. First, under normal gravitational field more oxygen can flow in flame base. Chain reaction (H+O_2→OH+O) occurs more fast. Second, under reversed gravitational field flame base exists at flame top. Distance of flame base to burner is longer and heat loss decreases. That means heat loss is more effective than heat release, and the microflame under reversed gravitational field can establish more stably

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In order to clarify spray combustion mechanism, numerical calculation on flame propagation of a fuel droplet array was conducted. Numerical results were compared with microgravity experiments, and revealed details of the propagation process. However, most of those researches were considered in stillness atmosphere. In actual spray combustion, droplets are influenced of the circumference air current. It is not yet clear that the influence which a circumference air current has on flame propagation, In the present paper, the effect of forced convection on flame propagation of a fuel droplet array was discussed by numerical calculation.

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In this paper, a dependence factor of soot emissivity on wavelength, a is studied in a counterflow propane diffusion flame by spectroscopic measurement. The spectrometer is set vertically to the nozzle and radiation of luminous flame is obtained each height from the lower burner. The emissivity is calculated from emissive power of luminous flame and blackbody furnace, and a is obtained by analysis of the emissivty. The relations between a and temperature, wavelength and distance from lower burner are examined. Results show that a is smaller with longer wavelength in the range of 600nm - 1000nm. Additionally, it is suggested that a also depends on soot conditions.

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In this paper, solar-hybrid reforming of methane to produce hydrogen was proposed and investigated using a xenon lamp pseud-solar radiator. A mixture of methane and steam is introduced into a porous Ni catalyst heated directly by the solar energy passing through a quartz glass, and then, converted into product gases, i.e., hydrogen, carbon monoxide and carbon dioxide. The enthalpy of the product gas was recovered through a reciprocating-flow energy recirculation system using an inert porous ceramics that play a role of heat storage. As a result, it was shown that hydrogen including solar energy was produced quickly and effectively.

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We are developing the new type of an air conditioner for deodorization in houses of cattle, pigs or chickens. The machine consists of a disk fan, a refrigerator and heat exchangers. In the air conditioner, heat exchange takes place between the refrigerator and input air. Temperature decrease of the air causes the condensation of the moisture, with the ammonia and other impurities are dissolved. When water is sprayed on the rotating disks, it splits into the small droplets, which enhance the dissolution of ammonia and other impurities into water. Experimental results revealed that the concentration of ammonia in the water exceeds much more to the equilibrium solubility.

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CO emission of the gas phase combustion in a packed bed has been investigated experimentally and numerically for lean methane/air premixed mixture. The results show that CO emission is generated at the bed temperature just lower than the temperature in which combustion is completed. This CO emission is due to the early stages of combustion reactions, which does not only depend on the bed temperature but on a residence time of mixture in the bed.

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Combined forced-convective and radiative heat transfer in cylindrical packed beds with constant wall heat flux was numerically studied. The zero-equation turbulence model proposed by the authors was incorporated into the governing equations. The macroscopic momentum equation considered the effects of turbulence and hydrodynamic dispersion, in addition to Darcy-Brinkman-Forchheimer flow resistances, while the effects of thermal radiation, turbulence and thermal dispersion were taken into account in the energy equation. With this model, numerical analysis of combined heat transfer in cylindrical packed beds with constant wall heat flux was made, and the results were compared with available experimental data. The agreement is acceptable, showing that proposed numerical model is satisfactory for predicting the characteristics of fluid flow and heat transfer in packed beds.

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Hydrodynamic characteristics of a fluidized bed at elevated temperature up to 850K were investigated. X-ray radiography (XR) was applied to the visualization of bed-material movement and quantitative measurement of void fraction in the bed at elevated temperature. Differential pressure of the fluidized bed was also measured, simultaneously. The result indicated that the minimum fluidization velocity decreased with an increase in the bed temperature. This agrees with the existing correlation, e.g. Kunii-Levenspiel. In this paper, the flow pattern transition and the agitation intensity of void fraction around horizontal tubes were also discussed on the basis of visualization results.

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A new nano- and micro-scale porous layer formed on the wall surface, named "NMPLS: Nano- and Micro-scale Porous Surface," has been developed by combing the chemical etching method combined with nano-particles : "NPL : Nano Porous Layer" method, and the non-electrolyzed plating technique : "FP : Fine Precipitate" method. The ultrahigh convective heat transfer performance compared to the well-known heat transfer correlations is achieved around 60〜80% increase for the basic water experiment and also 40% increase for an air-water co-current coaxial heat exchanger.

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Energy transfer from fluid to the surface was calculated by using the classical molecular dynamics method in order to investigate effects of surface structures in nanometer scale on the surface energy transfer numerically. Surface structures on the constant surface area were composed of several hundred atoms having the same thermal properties. Upper region in the calculation domain was controlled at a constant temperature and the solid atomic layer at lower region was controlled at a constant temperature so as to make a temperature gradient in the calculation system. Fluid molecular diffusion in the vicinity of the surface was dependent on characteristic length scale of the surface structures in nanometer scale that affected the dynamic behaviors of fluid molecules in the vicinity of the surface. The effect to fluid molecular diffusion was observed within 2nm distance in the present calculation conditions.

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In order to apply Flibe as a liquid blanket material, a heat transfer enhancement system is required because the Flibe is a high Prandtl number fluid. The purpose of this study is to visualize the detailed flow fields in the packed-bed tube, which is expected to utilize for the heat transfer enhancement. The visualization inside the packed-bed tube is performed by using a PIV system with a refractive index matching technique. The flow field in the packed-bed tube is visualized from various angles by the PIV system to describe the complicated flow structures in it.

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Every existing gas turbine is of open-cycle in which exhaust gas is discharged into atmosphere. Several exceptions, namely those of open-cycle, all disappeared so far, because there has been no demand for that. Therefore, the effort of gas-turbine development has been directed towards simple enhancement of the inlet gas temperature through material development and/or some exquisite blade cooling technique. In the field of nuclear energy, on the other hand, there exists a demand of closed-cycle for the next generation reactors such as high temperature gas-cooled power reactor or gas-cooled fusion reactor for which the perfect confinement of radioactivity is the crucial requisite. Moreover, in the nuclear applications, the highest temperature of the gas turbine cycle is restricted from above by other factors such as integrity of irradiated materials or possible mobility of the radioactivity. If so, the problem inevitably reduces to that of how to realize the excellent cycle performance through other thermo-mechanical considerations

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Direct numerical simulation methodology is employed to analyze a two-dimensional separated and reattached flow and heat transfer around an inclined downward step in a plane channel. Treated in the present study is an expansion ratio of 1.5. The inclination angle of step α is systematically varied from 15° to 90°, and the Reynolds number Re from 100 to 1200. The flow is found to be steady at Re&le;400 but become sensibly unsteady at Re=500. Heat transfer is promoted by the unsteadiness of flow and the Nusselt number increases in the neighborhood of the time averaged reattachment point.

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A stirred-tank reactor is used for a unit operation in many fields of chemical processes, such as for mixing, heating, cooling and chemical reaction. Then the heat and mass transfer characteristics significantly depend on the flow structure induced by a rotor in the tank. In order to design high performance equipments, it is essential to identify and to optimize the flow structure. Aiming at further development of such stirred-tank reactor, flow visualization study was conducted on the structure of mixed convection due to a forced convective motion by the rotor and natural convective motion by heating and cooling.

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We numerically simulated how magnetizing force affects the natural convection of water with the diamagnetic property in a vertical cylindrical container heated from below and cooled from above. When the circular electric coil was placed at the lower end plate heated isothermally, the average Nusselt number in the system with the magnetic field decreased in comparison with that in the system without the magnetic field so that natural convection was suppressed by the magnetizing force. When the circular electric coil was placed at the upper end plate cooled isothermally, the reverse tendency was computed. Furthermore, to understand the mechanism of the generation of the magnetothermal convection induced by the magnetizing force, the variety of magnetothermal convection to the steady state was visualized under two different initial conditions.

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A numerical study has been made on forced convection around a porous obstacle concentrating on the effect due to the permeable surface condition. The effects of porous parameter induce a significant change in flow patterns and suppress the Karman vortex in a wake region. Further it is noted that the drag coefficient of a porous obstacle is reduced compared with that of an impermeable object. The degree of the decrease in the drag coefficient of the porous obstacle depends on its permeability and blockage ratio.

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Direct numerical simulation methodology is applied to analyze the three-dimensional unsteady characteristics of a separated and reattached flow and heat transfer around a downward step in a channel of expansion ratio 2.0 and aspect ratio 36. The Reynolds number Re is varied from 300 to 1 000. The flow is steady at Re&le;500 but becomes sensibly unsteady at Re=600. The present numerical results of the reattachment length agree very well with the previous experimental and numerical ones. The time averaged Nusselt number is large in the reattachment region, and becomes maximum in the neighborhood of the side walls due to the longitudinal vortex.

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For natural convection in the geometrically complicated channel, the convection flow is suppressed by flow resistance due to such channel itself and the lopsided flow may take place. This may give serious influences on the heat transfer in the channel. The purpose of the present research is to investigate the natural convection flow and heat transfer inside the vertical channel where flow resistance is added at the lower end. In this paper, the flow resistance and width of the channel were changed and the influence on the flow and heat transfer was discussed in connection with flow pattern.

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Radiation converter made of a wire mesh is proposal for heat transfer enhancement of HiCOT (high temperature air combustion technology) furnace. Heat transfer and fluid flow characteristics through a wire mesh at low Reynolds number are investigated by numerical simulation. Detailed model at various condition are necessary for performance prediction and modeling for design. It is confirmed that flow resistance results agree well with existing experimental data. Empirical formula of fluid resistance and heat transfer coefficient through a wire mesh was obtained.

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Experiments on convective heat transfer from a rotating disk with fins, which are arranged along radial direction, are performed to know the heat transfer characteristics for designing the ECB retarder. Heat transfer coefficients at three different positions along the longitudinal direction of the fin are evaluated from temperature distribution obtained by thermocouples inserted in the fin. The result shows that the heat transfer coefficient at each position is much higher than that for the rotating disk without fin, and varies complexly with fin angle. The heat transfer enhancement by arranging fins is marked especially at low rotating speed condition, since turbulent flow heat transfer exists over almost the entire surface even at such condition, in which laminar flow heat transfer appears in the case of the rotating disk without fins. Finally the fin array which has the highest heat removal performance in the disks tested is shown.

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