Based on nonequilibrium molecular dynamics simulations the inverted temperature profile is investigated. Heat and mass fluxes across the liquid-vapor interface are discussed using kinetic theory, irreversible thermodynamics and the entropy production rate in the vicinity of the condensation surface. It is found that the inverted temperature profile takes place in NEMD simulations without contradiction in the second law of thermodynamics and kinetic theory of gas.

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In-flight microplasma synthesis of luminescent silicon nanocrystals (Si-NCs) is presented. A mixture of SiCl_4 and H_2 is activated in the high pressure (10 kPa), miniaturized non-thermal plasma reactor. High pressure condition accelerates cluster nucleation via three-body reaction, while a miniaturized reactor suppresses excess crystal growth due to short residence time, leading to 3-5 nm crystalline nanoparticles: process yield of 30-100 mg/h of luminescent Si-NCs was demonstrated. Crystallinity of as-produced silicon nanoparticles increased with increasing either input power or initial H2 content in the feed gas. Strong photon absorption in the short wavelength (less than 450 nm) and associated red-photo luminescence due to quantum confinement effect was confirmed.

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This paper presents pressure-dependent (5 kPa-100 kPa) selective growth of multi-walled and single-walled carbon nanotubes (CNTs) in plasma enhanced chemical vapor deposition (PECVD). High-purity, vertically-aligned single-walled CNTs (SWCNTs) were synthesized only when PECVD was employed at atmospheric pressure, while multi-walled CNTs were preferentially synthesized when the total pressure was lower than 20 kPa. In the reduced pressure range, catalyst coagulation was unavoidable at the initial stage of CNT nucleation: catalyst coagulation took place independently of plasma-induced damage such as excess supply of reactive species and energetic ion bombardment. If catalyst coagulation was avoided at the moment of CNT nucleation by marker growth technique, SWCNTs were grown in the root growth regime even at 5 kPa; however, top SWCNT layer, which is adjacent to the reactive plasma, was seriously contaminated by amorphous carbon produced as a result of excess supply of reactive species.

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The purpose of this study is to clear the synthesizing mechanism of the compound materials using plasma CVD method. The determination method of the chemical reaction using the values of electronegativity and ionization energy is presented. The chemical reaction between the atom that has the highest electronegativity and the atom that has the lowest ionization energy occurs with first priority. The calculated results using the method have good agreement with the experimental results of synthesizing materials such as carbon and silicon carbide. Consequently, the method is useful to synthesizing compound semiconductors using plasma CVD method.

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In this paper, we prepared ZnO nano-particles by using pulsed laser ablation in water. ZnO particles are dispersed in pure water as a target material of laser ablation. We irradiated the ZnO particles in water with YAG laser with different wavelengths to investigate the effects of photon energy on the nano-particle formation. We measured both atomic composition of ZnO and crystallinity of the fabricated nano-particles by EDX and XRD. We also observed ZnO nano-particles by TEM. The averaged diameter of ZnO nano-particles was 6 nm.

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Distributions of emission intensity from radicals, electron temperature and rotational temperature at a radio frequency of 27.12MHz plasma in water are clarified by detailed spectroscopy measurement. Through this investigation, the following were observed. The points of maximum emission intensity of Hα, Hβ, O(777 nm) and O (845 nm) are almost the same, while that of OH shifts upward. The electron temperature decreases, while the rotational temperature increases with pressure. The distribution of the electron temperature changes at a threshold pressure, which is concerned with a change in the electron discharge mechanism. The point of the maximum rotational temperature of OH radicals shifts to approximately 1 mm above that for the maximum intensity of OH emission.

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The interaction mechanism between an argon plasma flow at atmospheric pressure and water surface was studied. The generation and residual of reactive oxygen species (ROS) in purified water were focused in this study. Exposure of a water surface to the plasma flow at atmospheric pressure for 10 min generated ROS in purified water. The ROS concentration increased greater than 30,000 counts/10 s with 43% of the ROS still remaining after 30min in air, whereas exposure only to the plasma emission did not affect the level of ROS in purified water. The generation of chemical species which were transported to the water surface was also clarified. The ROS in the former water had a weak bacteriostatic effect.

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The effect of solid particles on the performance of pulsating heat pipe (PHP) has been investigated using unlooped and looped PHPs. The PHP is made of copper tubes with 3mm OD and 2mm ID, and the number of turns is 12. Lengths of heating, adiabatic and cooling sections are 50mm, 100mm (or 90mm) and 50mm, respectively. Diamond particle (8-20μm) or alumina particle (10μm) is added to the working fluid, water or R141b. It was found, the temperature difference between heating and cooling sections decreases by adding particles. The enhancement of PHP performance by particle is more remarkable for looped PHP. Alumina particle has nearly the same effect as diamond particle in high heat input region.

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One of the improvement techniques of effective thermal conductivity for metal hydride particles bed is a insertion of radial fins into the bed, by which the heat transfer characteristics and reaction kinetics can be enhanced. Rectangular fins are inserted from 3 to 6 into the metal hydride particles bed and hydrogen absorption amount of metal hydride has been measured by constant volume Sievert's method. Reaction kinetics is defined as a ratio of 80% of maximum hydrogen absorption over the absorption time when the amount of hydrogen absorption reaches its corresponding value. As the results, radial fins are useful for the enhancement of the heat transfer and reaction kinetics of metal hydride particles bed. Reaction kinetics of reactor with 6 fins can become two times faster than that without the fin.

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We have investigated the hydrogen storage tanks with metal hydrides employed for load leveling of commercial buildings. The storage tank with 50 kg AB5 type metal hydride alloy was assembled to investigate the hydrogen absorbing / desorbing process, which is exothermic / endothermic process. We have a plan to utilize hot heat and cold heat of each process for air conditioning that can expect to improve the system efficiency. To verify the practical effectiveness of the idea, we planned the special operating procedure and carried out the experiments. Here, we report the experimental results and discuss the effectiveness of the system using the energy balance analysis.

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We proposed the totalized hydrogen energy utilization system that consists of a fuel cell device, a water electrolysis device and metal hydride tanks, and developed the mathematical model of hydrogen storage system that composes of several metal hydride tanks. The discharging hydrogen performance was investigated experimentally and numerically. As a results, it was shown that if the circulating water piping that flows in metal hydride tanks was connected with the series, and control method that increased the number of operating tanks are adopted when the outlet pressure of hydrogen decreases, hydrogen in each tank could be efficiently used.

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This paper presents a new measurement technique of neutron radiography for fuel cell researches. Water condenses in MEA, GDL and channel in cathode side of PEFC (Polymer Electrolyte Fuel Cell) while PEFC generates electricity. It is expected the condensed water may decrease power generation capability. Visualization of the condensed water behavior is important to study the fuel cell and neutron radiography is effective for the visualization. A borescope system was introduced into neutron radiography to visualize water of thickness in the MEA and the GDL. Borescope system enables neutron radiography to take a picture pixel size of which is 6.5μm and to measure water of thickness in the MEA and the GDL with the exposure time of 50 seconds.

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Water management is very important in the development of the Polymer Electrolyte Fuel Cells (PEFC) with high performance and high reliability. We devised a movable separator rib which can change its position manually, and carried out experiment and three-dimensional numerical analysis with Lattice Gas Automaton method. It is found that the movable separator rib can control water behaviors and performance of the fuel cell.

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Microstructural properties of an SOFC anode, such as tortuosity factor, surface-to-volume ratio and permeability, are quantitatively evaluated using three-dimensional data obtained by a focused ion beam and scanning electron microscope, FIB-SEM. Random-walk-based diffusion simulation is applied to evaluate these properties, in which the diffusion of imaginary particles is considered. The relationships among these properties and their effects on transport phenomena in a porous anode are discussed. It is revealed that large tortuosity factors of the Ni and YSZ phases are caused by inefficient network of the Ni phase and complex microstructural configuration of the YSZ phase, respectively.

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Mathematical models to simulate phenomenologically hyperthermic stress-induced cell damage and death have been developed by the authors so far. In this study, the mathematical model was applied to predict such cell damage and death in the semiinfinite body heated by unsteady ID heat conduction. Unsteady changes in number fractions of damaged cells and dead cells were calculated using the analytical solution of unsteady ID heat conduction and the mathematical model with a rate constant of temperature dependency expressed by the Arrhenius' equations. Characteristics of spread of heated region and damaged and dead regions in the body were investigated.

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A thermosyphon is a heat exchanging device which transports a large amount of heat with a very small temperature difference between the ends of the pipe. In this study, we applied biomass energy that is anticipated as resource saving and resource energy to thermosyphon's heat source. And we devised and worked heat transportation system that can transport heat for a long time. As this experimental result, we found that this experimental system is utility because temperature difference appears in a condensation part and an environmental temperature.

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A series of Multi-thermosyphons is able to recover the waste heat effectively and is paid to attention. In this research, we apply Multi-thermosyphons to a waste heat recovery system in the cascade thermal energy place, and evaluate the performance of the system by the theory. For the direction of the flow, we have understood the counter-flow obtains a high exit temperature and a big amount of the heat transportation comparing with the parallel-flow. As for the heat recovery steps, we have obviously understood the multi-step is excellent comparing with the single-step.

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Systematic dew and frost point data were required on the assumption that occlusions of pipes or instabilities of flow systems would occur due to condensation of high boiling point residual gases, such as water vapors, in high pressure hydrogen under rapid hydrogen filling processes in hydrogen stations for FCVs. Dew point measurement system with high pressure test cell utilizing cooled mirror technique with visible image analysis were designed and produced. Measurements with H_2+H_2O standard gases for detecting generation and growth of frosts on the mirror surface were carried out to verify basic functions of the system. Dew point estimation procedures for phase equilibrium systems with solid phases as condensed phases were also considered.

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In order to achieve in situ viscosity measurement, we have developed a new miniaturized optical viscosity sensor, namely MOVS (Micro Optical Viscosity Sensor), based on a laser-induced capillary wave (LiCW) method enabling high speed, small sample volume and non-contact measurement of sample viscosity. The newly integrated optical surface tracking system makes possible the stable viscosity measurement under external disturbances. In this study, by integrating the optical surface tracking system, nanosecond damping oscillation of LiCW is successfully observed in the presence of high speed evaporation (speed of 1 micrometer per second) and external forced vibration.

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A non-contact fluid temperature measurement in microscopic scale using fluorescence polarization is proposed and carried out in this study. The polarization of the fluorescence emitted from a FITC-Casein solution is measured, and the effects of pH, measuring time and fluid temperature are evaluated. In the result, a linear relationship was observed with the polarization and the fluid temperature. Furthermore, while the fluorescence intensity itself showed a significant dependency on the pH and measuring time, the polarization remained constant. From these results the possibility of using fluorescence polarization for fluid temperature measurement was affirmed.

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Conversion characteristics of thermophotovoltaic cells made of GaSb semiconductors were investigated through a hemispherical irradiation with isotropic intensity from a blackbody light source. The TPV cells were manufactured by molecular beam epitaxial growth method. The conversion efficiency reached 4% in the range of wavelength from zero to 1.8μm at the source temperature of 924K. The maximum output power was 18mW/cm^2 at 1124K.

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In microwave heating, interference of transmission wave and reflection wave in a sample has an important meaning. Using the microwave of TE_<10> mode and frequency of 2.45GHz in rectangular waveguide, the characteristics of microwave heating on three-dimensional electromagnetic field has been investigated by numerical analysis. Although the electromagnetic distribution of the microwave of TE_<10> mode in the rectangular wave guide generally has two-dimensional distribution, the distribution turns into three-dimensional distribution with a structure of sample or a setting position of sample. It was found that the microwave heating of sample for three-dimensional electromagnetic field was effective compare with the case of two-dimensional electromagnetic filed.

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The technical development makes devices downsizing. There are some devices that causing functional disorder with the water or some devices that humidity adjustment is necessary for driving, and humidity measurement for the small space is required. A new small humidity sensor based on the principle of a psychrometer was proposed. The sensor is made by using the thermocouple (ψ100μm) as a dry-bulb and applying a polymer having water retentivity in substitution for gauze as a wet-bulb. As a result, the invasion diameter became 0.3mm in a minimum.

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The phenomenon in the vaporizer for low volatile organic solvent is analyzed and the performances of the two types of vaporizer are evaluated. The numerical simulation shows that the vaporizer using a two-fluid nozzle cannot fully utilize the tube space because of the strong penetration characteristic and the low adjusting capability of the flow pattern. The vaporizer with ultrasonic nozzle and gas inlets is presented to avoid the disadvantages above. It is demonstrated that the ultrasonic nozzle type can achieve more than 6 times particle residence time as compared with the two-fluid nozzle type and it can be applied for the evaporator of the low volatile organic solvents.

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A two-dimensional, two-phase flow model for a passive-type vapor-feed DMFC (PV-DMFC) is analyzed to clarify the transport phenomena and the cell performance. As a result, the smaller liquid saturation in the anode diffusion layer than a liquid-feed type brings the easier CO_2 removal from the anode catalyst layer. This is one of the important advantages in the PV-DMFC. However, the small liquid saturation causes the anode reaction site to decrease, and the cell performance is degraded. The appropriate water management in the MEA enables higher performance of the PV-DMFC.

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A simultaneous measurement of thermal diffusivity and heat conductivity using inverse solution is significantly improved by introducing a new idea. In the idea, a data window for series of sampled temperature is opened for a time interval, where number of measured temperature in a solid are enough to estimate the temperature at any time and any position. The size of window is determined by Fourier number including thermal diffusivity.

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Heat transfer characteristics of a gas-to-gas parallel-flow microchannel heat exchanger has been experimentally investigated. The microchannel has a rectangular cross section with 200 μm high and 300 μm wide. Working fluid used was air. Reynolds number ranged from 63.5 to 191. The inlets and outlets temperatures of the heat exchanger were measured to obtain heat transfer rate. Experimental heat transfer rates were compared with those predicted by a conventional log-mean temperature difference method. The log-mean temperature difference method can be employed to a parallel-flow configuration whereas that cannot be employed to a counter-flow configuration investigated in our earlier work.

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Spatio-temporal distribution of convective heat transfer behind a backward-facing step was measured in order to explore the mechanisms of the heat transfer caused by flow separation and reattachment. This measurement was achieved by using a high-speed infrared thermograph which measured temperature fluctuation on a thin foil heated electrically. The attenuation due to both the heat capacity and the lateral conduction of the foil was restored by solving heat conduction equations inside the test surface. As a result, it was clarified that the heat transfer enhancement in the flow reattaching region has a spot-like feature. The spatio-temporal characteristics are composed by a combination of many spots, which appear and disappear almost randomly but have some periodicity in time and spanwise direction.

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The effect of mainstream turbulence on a symmetric-airfoil/endwall junction flows and the associated endwall heat transfer was investigated by a combination of Large Eddy Simulation (LES) and wind tunnel experiments using Particle Image Velocimetry (PIV) and naphthalene sublimation method. The grid-generated mainstream turbulence was found to affect the time-mean flow and heat transfer fields greatly due to the change in dynamics of horseshoe vortex (HV) system. By LES showing reasonable agreements with experiments, it was found that the secondary peak of heat transfer rate on a symmetric line disappeared due to the random and unsteady motion of HV induced by mainstream turbulence.

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Heat transport characteristics and liquid flow configuration in a pulsating heat pipe consisting of single, straight tube and having a liquid containing structure in the heating section are investigated experimentally. The effective thermal conductivity increases monotonously with the heating power and becomes approximately 60000 W/(m・K) when the amplitude is approximately ±70mm. A part of liquid film, which forms during the vapor plug growth, flows into the heating section when the plug shrinks. The liquid supply from the heat transport section to the wick of the liquid containing structure in the heating section are shown to be necessary for realizing the successive, stable oscillation with high heat transport characteristics.

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This paper describes an experimental investigation of heat transfer characteristics of a closed two-phase thermosyphon using water based SiO_2 nanofluid with particle size of 80 nm as a working fluid. The total length of the thermosyphon was 800 mm (evap. 250mm, cond. 200mm) and O.D was 12 mm (I.D. 10 mm). SiO_2 particle volume fraction was changed from 0 to 18 Vol% in the experiment. The following conclusions were obtained from the experiment. (1) The thermosyphon with 10 Vol% nanofluid showed larger heat transfer characteristics than that with other particle volume fraction including pure water (=0 Vol%) (2) Nanofluid showed remarkable effect to minimize temperature fluctuation of evaporator under low radial heat flux condition around 5000-30000 W/m^2.

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The performance of a Joule-Thomson microcooler utilizing a concentric counterflow heat exchanger was investigated in this study. Trials were conducted for three coolants: C_2H_4, CO_2 and N_2. Three microcoolers of different dimensions were tested for pressures ranging from 0.5 MPa to 5MPa. The microcooler managed to obtain cooling power of 100mW at 234 K, well exceeding the target performance of 100 mW at 273 K. Comparisons between gas species highlight the importance of considering favorable heat transfer properties as well as a high Joule-Thomson coefficient when selecting the working gas.

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This paper describes about study of temperature controlling system for beds of truck drivers. Nowadays, idling is undesirable from the view point of global warming. However, idling is needed for air conditioning while truck drivers take a rest in their trucks. In this research, the cooling or heating bed with heat storage material instead of air conditioner with idling is proposed. As the 1^<st> state of the research, we made trial bed and examined the desirable property of the bed. As a result, it was investigated that 518.9 kJ/K of heat capacity of heat storage material is required for the bed.

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This paper describes the visualization study of the fluid flow inside the vapor chamber. In order to observe the inside liquid flow phenomena, the special vapor chamber is fabricated. It is composed of a bottom plate, a top plate and a spacer. The bottom plate has a sintered wick and the top plate has the observation window. The heat is applied from a heat source to the bottom plate, while the top plate except the window is cooled by heat sinks. The images of the evaporator section inside the vapor chamber are presented with the temperature distributions, and the liquid flow and its evaporation phenomena are discussed.

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A vapor chamber has been used as a heat spreader for cooling high-power small heat sources, such as CPUs in personal computers and servers. The vapor chamber is essentially a flat-plate type heat pipe and generally made of copper. In the present study, the aluminum vapor chamber is fabricated to reduce the weight. The aluminum vapor chamber is composed of two aluminum plates and a clear acrylic spacer sandwiched between them. HFE-7200 is used as the working fluid. The heat transfer characteristics of the aluminum vapor chamber are investigated, and the thermal performance is compared with the aluminum solid plate. The aluminum vapor chamber is 61 % lighter than the copper one.

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Subcooled flow boiling of water has been investigated for a heating surface of 50mm in length and 20mm in width placed on the bottom of horizontal rectangular channel under lower pressure of TOkPa.abs and higher pressure of 150kPa.abs in the boiling fluid loop. The mass flow rate of liquid is fixed at 500kg/m^2s (0.5m/s). The critical heat fluxes are well coincident with the existence theories modified with pressure. Microbubble emission boiling (MEB) occurs easily at lower liquid subcooling, 20K for an example, and the heat flux obtained is higher than CHF. The pressure gives strongly effect on MEB generation in subcooled flow boiling.

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The number of thin natural cooling equipment has increased in recent years. In a study about the natural convection of electrical equipment, it is important to measure the natural convection velocity. However, the internal flow of natural cooling equipment is complicated, and the behavior is not understood. In this study, the velocity distributions in a transparent model of thin natural cooling electrical equipment were measured using a PFV. Temperature increase of a heating component was also measured as a function of a casing clearance. It was found that the vertical velocity has a maximum at the center of the heater. Measured velocity profiles were compared with simulation results and the validity of the PIV measurement was confirmed.

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This paper describes air cooling performance which is driven by axial cooling fans for electronic circuit boards set in the thin enclosure, where cooling air flow pass is very narrowed by many mounted devices. Especially, we focused on an effect of a flow pattern difference between the fan flow, which is a rotational flow, and the uniform stream. To discuss the effects of the fan flow to the heat transfer performance, we designed a test enclosure model which is composed of a model cardboard including 5 heat sources and a heatsink duct including the axial fan and inspected a temperature rise of the model board and heat sources. From the result, it is found that the effect of the fan's three-dimensional flow may affect the heat transfer performance.

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The electrolytic capacitor is one of the most important components for the thermal analysis of electronic equipment. To predict component and system temperatures, the thermal flow simulation technique has been applied to thermal design of electronic equipment. In this study, we examined a compact modeling method for electrolytic capacitors in order to simulate thermal flow based on the computational fluid dynamics (CFD) code. To obtain fundamental data for the thermal modeling method, first, we conducted experiments to identify the major thermal path of electrolytic capacitors in actual electronic equipment by using a switch mode power supply unit. Next, to verify the validity of the thermal model, a benchmark experiment was conducted to obtain actual measurement data of the temperature rise of electrolytic capacitors under various operating conditions. The thermal model of the electrolytic capacitor was presented based on the CFD code. In this paper, we describe in particular the snap-in type electrolytic capacitor.

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Heat dissipation is a critical issue for designing LCD televisions, which tend to be designed more thinly. We use thermal simulations to evaluate thermal behavior, and decide a heat dissipation structure of LCD television. To be put into practice, thermal simulation must be done in short time and brought a necessary and sufficient accurate result. In this paper, we talk about the customized thermal simulator for LCD televisions and the case study of thin type LCD television.

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Isotropic conductive adhesives (ICAs) have been applied to die attachment materials for power devise and LED. The thermal characterization of ICAs is important to thermal management. We developed steady state comparative-longitudinal heat flow method using cartridge type specimens. Thermal conductivity of silver-epoxy conductive adhesive and interfacial contact thermal resistance between the conductive adhesive and the bonded interface were evaluated. The results showed that the measurement method has capability to measure thermal conductivity within 10% of uncertainty. Additionally, the interfacial contact resistance of ICAs affect thermal conductance at thin thickness.

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In this research, thermal resistance of the anisotropic thermal conductivity material was measured. For applying the local cooling technique by using spray cooling for semiconductor devices, splayed liquid should not be directly flowed to the surface of semiconductor devices. Then some solid materials are required between liquid and semiconductor devices. From the view point of reduction of thermal resistance with solid, super thermal conductivity material is attractive and we chose a block of STC. STC also has anisotropic thermal conductivity. As a result, thermal conductance for the good thermal conductive direction shows 5-6 times larger than that for other directions and thermal resistance for the good thermal conductive direction is 0.1 K/W.

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A wiring substrate in electronic equipments is a composite board, which consists of several elements having different thermal conductivities, such as wires, vias and matrixes. This paper describes the theoretical investigation on the simple equations to estimate the effective thermal conductivity of such a composite system. Two types of simple estimation equations are derived based on thermal resistance network models. Three-dimensional simulation is also performed to obtain the effective thermal conductivity of the composite system. By changing the geometrical layout and the ratio of thermal conductivities of the composite system, the estimated values by simple equations are compared with the calculated ones by simulation, and the discussion is made on the validity of simple equations.

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Heat and mass transfer of chemically reacting flow for reciprocal resolvable solvent has been studied using Hele-Shaw Cell. Neutralization reaction of sodium hydroxide (NaOH) + acid (hydrochloric acid (HC1) or acetic (CH_3COOH) of a constant initial density is adapted for the chemical reaction. The density distribution of around the chemical reaction front has been measured by using the laser speckle method. Furthermore, visualized thermal fluid flow has been compared with the density distribution. As a result, decrement of density due to the exothermic chemical reaction generated the natural convection near the reaction front.

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An optimization method with numerical simulations has been developed and used in several fields. In several methods, we will propose the method based on adjoint sensitivity analysis. Using this method, various sensitivities can be obtained by a couple of numerical computation of the conventional problem and the corresponding adjoint problem. On this paper, we focus the shape sensitivity for the maximization of local velocity in heat convection field. We set several conditions and compute forward and adjoint equations discretized by Colocated mesh with SIMPLE method. We show the conclusion of the shape sensitivity analysis and the application of this method.

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When we numerically investigate a periodic heat convection field which has a long cycle like a day cycle, a huge calculation cost is required to obtain the complete periodical solution. In this work, we solved the governing equations in the frequency domain, and applied an upwind scheme to the Fourier coefficients. To validate the accuracy, we compare the calculated result of Fourier series expansion method with that of time marching method. These results were calculated under high Rayleigh number to confirm the stability of the proposed scheme. This result reveals that the proposed scheme was stable and we could obtain a periodical solution at low cost.

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