We investigated on direct decomposition of heat-trapping gases using intense shock waves. Our experimental apparatus is a shock tube using exhaust gas of detonation. In this study, we paid attention to the decomposition of CCl_2F_2 and N_2O. A purpose of our experiments is to clarify influence of the temperature and heating time on the decomposition characteristic of CCl_2F_2. We ignited C_3H_8-O_2 premixed gas, and propagated intense shock wave. As a result, we obtained 63% of the highest CCl_2F_2 decomposition rate in 4000K, and 99% of the highest N_2O decomposition rate in 1400K.

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This paper reports the visual observations of the clathrate hydrate crystal growth at the interface of water and a guest-substance liquid with surfactant. Cyclopentane and Span80 were used as the guest substance and surfactant, respectively. We visually analyzed the individual hydrate crystals and classified the morphology of the crystals according to ΔT_<sub> at atmospheric pressure. It was found that the size of the individual hydrate crystals decreased with increasing ΔT_<sub>. The results showed that the size of the individual hydrate crystals in cyclopentane-Span80 solution systems was greater than that in pure cyclopentane system. Organizing the crystal morphology, we revealed the influence of surfactants on hydrate crystal growth process. Hydrate crystals in cyclopentane-Span80 solution systems were grown into the bulk of water and cyclopentane solution instead of covering the interface.

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We present a preliminary thermodynamics-based simulation study about the hydrate-based multistage separation of CO_2 from a CH_4 + CO_2 mixture, a simplified model of a low-quality natural gas supplied from gas fields in Southeast Asia. The entire process at an arbitrary one of the successive stages has been modeled as an isobaric hydrate-forming operation in an open thermodynamic system accompanied by successive feed gas + water supply and gas + aqueous liquid + hydrate discharge. Based on such a modeling, we have predicted the evolution of the composition (CH_4 and CO_2 fractions) of the gas discharged from the system.

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This paper reports the four-phase (ice + hydrate + CO_2 + 3,3-dimethyl-2-butanone) equilibrium pressure-temperature conditions at temperatures (252 to 272) K in the system of water, CO_2 and 3,3-dimethyl-2-butanone. The pressure range of the present measurements in the system is (0.44 to 1.04) MPa. This paper also reports the four-phase (ice + hydrate + CO_2 + 2,2-dimethylbutane) equilibrium pressure-temperature conditions at temperatures (254 to 263) K in the system of water, CO_2 and 2,2-dimethylbutane. The pressure range of the present measurements in the system is (0.49 to 0.74) MPa. The measurements were carried out using isochoric methods. The results indicate that structure H hydrate formed with CO_2 and 3,3-dimethyl-2-butanone is stable exclusively at the temperatures below 272 K.

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CO_2 dissolution phenomena are important issues in enhanced oil recovery (EOR). Fundamental mechanism of them, however, is not clarified. In this study, CO_2 dissolution in cyclohexane (C_6H_<12>) was investigated by molecular dynamics simulations. Although CO_2 seems to be dissolved into C_6H_<12> which shows distinct difference to the case of CO_2/H_2O, aggregation of CO_2 molecules was observed under the condition of high CO_2 mole fraction. Furthermore, dissolution process in the CO_2/C_6H_<12> interface was enhanced in the case of supercritical CO_2, compared with that of liquid CO_2.

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This research focuses on the catalytic effect of nickel foam metal through steam reforming of methane. The experiments were conducted under the conditions of steam-carbon (S/C) ratio of 22.2, 16.4, and 5.01. The results showed that almost all of the produced syngas is composed of H_2 and CO for S/C=22.2 and 16.4, which may be one of the peculiar features of this nickel foam metal. Also, the conversion reaches 95.2% under the condition of S/C=22.2. On the other hand, coking was observed with low S/C, which led to catalytic effect instability during reforming. It is expected that, by separating H_2 from syngas using hydrogen separation membrane and lowering its concentration, more H_2 would be produced from CO rich gas through shift reaction.

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Top-heat thermosyphon can transport heat without power input and many applications of it are expected. We built up an experimental set up of top-heat thermosyphon on a model house. The working fluid, water is warmed by solar irradiation in the thermal collector on the roof of the model house. The heat is transported to the heat exchanger which is set 4m lower than the thermal collector. In our experiment heat transported was oscillating and we could not observe unidirectional semi-stable flows which occur in a laboratory with constant heating.

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Based on our field experiment on a solar thermal collector without using optical surfaces, the maximum available temperature of the collector is about 80℃. This paper describes possibility and meaning of a steam Rankine cycle driven under the temperature range of ambient to 80℃. The working fluid is water. According to a simple cycle calculation, thermal efficiency of the present system was estimated 5% at the highest. As far as the present conversion coefficients of the photovoltaic cells (i.e. 5-10%) are concerned, the electricity generated by the solar heat is above 2% of that by the photovoltaic cells. This suggests that the electricity generation by solar heat seems to be very promising, even if the operation temperature of the steam cycle is rather low. On such low temperature cycle, sophisticated pressure control of the system is considered to be one of the major breakthrough subjects.

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In the new century, the energy and environmental problems are becoming more critical, the development of natural energy is desired. Low-grade Thermal Energy Conversion (LTEC) is refocused as one of the renewable energy. The aim of this study is to improve the system performance with Double Stage-Rankine cycle. The irreversible loss in heat exchanger can be decreased at the cycle. As a result, the thermal efficiency of Double Stage-Rankine cycle is larger than that of Rankine cycle, and is smaller than that of Kalina cycle. On the other hand, the maximum of turbine power of Double Stage-Rankine cycle is larger than that of Rankine cycle and Kalina cycle.

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Life cycle environmental evaluation of a new lightweight electric-assist tricycle has been discussed in terms of materials supply, production, use and recycling/disposal stages. The effectiveness of a tricycle is compared with existing transportation such as light truck, passenger car, scooter and the well-known two-wheel electric-assist bicycle from the viewpoint of life cycle environmental impact. The factors affecting the environmental impact of each type of transportation device were shown. Then the optimum transport means is proposed suitable for the loadage and the time required in terms of environmental impact. As a result, the lightweight electric-assist tricycle was found to be effective for short-distance transport of a small amount of materials, as in a factory or for local transportation.

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A study has been conducted about an effect of a heat transfer enhancement in a downstream region of the backward-facing step using a small amount of mist whose size is a very small. Additionally, we focused a method in which a rod was inserted near the top end of the step in the channel. As the first in this paper, the effect of the mist on the thermal field of the heating surface and the flow field in the channel are studied experimentally. As the second, this paper shows the experimental results of the effect of the inserted rod on the thermal field of the heating surface and the flow field in the channel. In the position of the rod, x-axis was fixed and y-axis was adopted at three points. The greatest the enhancement of the heat transfer was obtained in the case with the mist and the rod position of Y/H=0.6.

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Heat transfer enhancing method is more and more needed to decrease heat exchanger size and power consumption. This study was carried out to develop a high performance vortex generator, and clarify the relationship between vortex structure and heat transfer. Arc wing pair was developed to increase lift-drag ratio. It was clarified that Arc wing pair had higher performance than Double delta wing pair by 5% at flow velocity of 1.0m/s (Re=1900) by measuring average heat transfer coefficient and pressure drop. It was found that arc wing pair had the position of vortex core at short distance from center of wing pair than that of double delta wing pair. Therefore, vortex intensity was more stronger by the interaction of the between vortices, so heat transfer performance was improved.

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There are several methods for heat transfer enhancement. For example, one can attach various fins on the heat-transfer surface, process the surface roughly, insert twisted tape, and so on. These methods increase the heat-transfer coefficient or area by manufacturing changes to the heat transfer surface. However, one must take into consideration the deterioration of the attached fins on the tubular surface in the design of the heat exchanger. The objective of this study is the clarify characteristics of heat transfer and pressure drop in a channel by inserting metallic wire with high porosity. A heat transfer experiment has been performed using a horizontal circular tube to obtain the heat transfer characteristics in the channel with the inserted wire. In this paper, the effects of porosity, wire diameter and wire material are discussed.

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A new film cooling concept has been developed by managing the swirled film coolant induced inside a hexagonal plenum by two slant impingement jets, which are inclined at a degree toward the vertical direction and installed in a staggered position on the plenum chamber wall. Film cooling tests have been conducted by using a circular film cooling hole model mounted on a low speed wind tunnel. The film cooling effectiveness on the surface of the wind tunnel was measured by pressure sensitive paint (PSP). It appeared from experimental results that the swirled film coolant flow deteriorated the film cooling effectiveness at low swirl number but improved it at high swirl number.

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The Rayleigh number effects on turbulence structure of thermally-driven boundary layer generated by horizontal heated round plate are investigated by using a well-resolved large-eddy simulation. The simulation is performed with an open-source code, OpenFOAM, with the Cartesian coordinate grid with the large computational domain to prevent the decrease in grid resolution near the edge of the heated plate and the generation of large-scale circulations. The range of Rayleigh number based on the radius of the heated plate is 2.1×10^7 to 4.2×10^7, which yields transition of the boundary layer from the laminar to turbulence. The predicted statistics reveals that there exists similarity of turbulence statistics-profiles and structures whereas the mean thermal- and velocity-fields depends on the Rayleigh number.

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We have carried out numerical simulations of ice crystal growth in a two-dimensional duct. An immersed-boundary method and the Phase Field equation are utilized to determine the interface. It is found that, as Reynolds number become higher, the growing dendrite arms to upstream become thick. Moreover, since a released latent heat in the upstream direction is transported downstream by flow, temperature gradient near the interface developing upstream becomes gentler compared with the temperature gradient near the interface developing downstream. Thus, ice growth is inhibited. Therefore, it is found that there is a strong correlation between temperature gradient around the interface and ice growth velocity.

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DNSs with a spectral method are performed to study Couette as well as Poiseuille flows at a low-Reynolds number. In both flows, quasi-laminar and turbulent regions simultaneously appear in unique stripe pattern over a computational region, and especially, the turbulent regions, tilted about 20〜30 degrees from streamwise direction, are flanked by high-speed fluids at the upwind side and low-speed fluids at downwind side. As a result of calculating the budget of turbulent energy inside the turbulent region, it is found that in the upwind side, the enhanced sweep contributes to transferring turbulent kinetic energy into the wall vicinity, while in the downwind side where the sweep dominance disappears, its transfer into the wall vicinity is significantly attenuated, and turbulent kinetic energy is mostly transferred into the channel center.

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PIV measurements were made in this study to discuss the flow and turbulence characteristics of viscoelastic fluid flow in a serpentine square channel under low Reynolds number conditions (Re=0.15〜3.3). Polyacrylamide solution was used as viscoelastic fluid, and was compared with the results of Newtonian fluid. While no fluctuations and secondary flows were observed in the Newtonian fluid case, an asymmetric distribution of the mean velocity was obtained in the viscoelastic fluid case. Further, in the downstream of the inflection point of the curves, maximum values of the fluctuation intensities were observed. This could be attributed to the change of the streamwise position where the crossing flow exists at the inflection point. The mean fluctuation intensity increased markedly as Re increased, and showed a good correlation with the relationship between the heat transfer coefficient and Re.

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A simultaneous measurement of velocity and thermal fields in the turbulent natural convection boundary layer in water has been conducted with a particle image velocimetry and a thermocouple rake. The measurement accuracy of turbulent heat fluxes was improved by compensating instantaneous velocity fluctuations with POD analysis. Because the maximum velocity for water becomes relatively larger than that for air, turbulent heat fluxes normalized with the maximum velocity and temperature difference made a marked difference between water and air. When turbulent heat fluxes are normalized with wall heat flux, both profiles for water and air are coincided with respect to one another. Therefore, it is recognized that characteristics of turbulent heat transfer essentially remain unchanged.

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This study was examined the possibility of a new method of simultaneously measuring temperature and velocity in convection field of heat transfer using micro-encapsulated thermo-chromic liquid crystal(MTLC). The present calibration technique is improved the more accuracy of temperature measurement in comparison with conventional calibration technique by hue divided by intensity. Their simultaneous measurement of thermal plume is carried out by capturing sequential visualized images and doing image processing of them. Those measured values are shown the same tendency as the Kaminski's result. These results indicate the potential of their simultaneous measurement using MTLC.

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To understand the heat transfer characteristics in fluidized bed, the particle convection becomes the most important factor in the bed. In this investigation, the heat transfer experiment under a forced particle convection was conducted by using the cylinder-shaped fluidized with stirrer, and we measured a temperature in the bed. In this experiment, several sizes of particles (d_p=0.2mm, 0.4mm, 1.0mm) were used. As a result, there was a sharp temperature drop in the first layer from the heating surface. And the experimental results were estimated by using a simple heat transfer model with effective thermal conductivity, particle-gas heat transfer coefficient and thermal contact resistance.

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In order to improve the thermal efficiency of a gas turbine, an attempt to operate the gas turbine at higher gas temperature has been made. Although the film cooling of the turbine blade by blowing out the air flow of low temperature along the blade surface is the most effective method, the improvement is approaching in the limit. In the present paper, the introduction of the mist flow was experimentally examined. The present experimental results showed that the maximum cooling efficiency was 24 % under the mist flow.

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Turbulence model testing has been made for the k-e model proposed by Abe-Kondoh-Nagano [Int. J. Heat Mass Transfer, 37 (1994), 139] using data obtained from a direct numerical simulation (DNS) of a separated flat-plate turbulent boundary layer. The Reynolds number at the inlet is set to be Re_θ=300 where Re_θ is the Reynolds number based on the freestream velocity and the momentum thickness. It is shown that the model calculation for a large separation bubble predicts the location of the separation point too early and yields large reversal flow due to the underprediction of the eddy viscosity near the wall.

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Spatio-temporal characteristics of convective heat transfer accompanied by the separated and reattaching flow are investigated. The distribution of heat transfer coefficient in the reattaching region is measured by an infrared thermography. It compared with the distribution of velocity measured by PIV. Both instantaneous measurements show spot-like distributions which indicates that the spot-like flow reattachment causes the spot-like heat transfer enhancement. Moreover, the relation between the position of maximum heat transfer coefficient and the time mean reattaching point were examined. In the case of forward-facing step flow, the position of maximum heat transfer exists about a step height upstream to the reattaching point.

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In this study, the analytical wall function (AWF) is improved to calculate heat transfer in separating-reattaching flows and impinging jets. Since the model coefficient for turbulent length scale is desirable to vary in such flows, it is functionalised by introducing sensitivity to the shear parameter. The obtained results are compared with the experimental data, and they showed that the modified AWF improves heat transfer in those test flows.

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An experimental study was made on the promotion and control of turbulent mixing of hot and cold airflows in a T-junction that simulated an HVAC unit for automobile A/C system. Delta wings were used as a mixing promoter, and the influence of their attack of angles on the thermal mixing and flow field were examined in detail. It was found that the thermal mixing is promoted by strong turbulence produced by the delta wings and its promotion can be controlled by changing the angle of attack of the wings.

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A numerical method was proposed to solve time-mean conjugate heat transfer in complex turbulent flows. The method is based on RANS, in which eddy thermal diffusivity is estimated by the turbulence statistics obtained by large eddy simulation. The proposed method was applied to examine the effect of endwall modification on total heat transfer in inclined pin-fin channels with a flat or wavy endwall. As a result, it is found that the wavy endwall shows an effect to enhance endwall heat transfer than flat endwall, while it shows less heat transfer rate on the pin surface. Thus, it is found that the benefit of wavy endwall depends on Biot number, which determines the heat transfer contribution of pin-fin surface to the total heat transfer area.

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Direct numerical simulation was performed for a spatially advancing turbulent flow in a two-dimensional curved channel. The radius ratio of the curved part, α, was set at 0.92, the same as Kobayashi et al.'s experiment. And the friction Reynolds number, Re_<τ0>, was set at 550 and 300. Numerically solved mean velocity field showed trends consistent with the experiment. As a result, the validity of the simulation was confirmed. Instantaneous flow field implied that micro-scale structures near the outer wall were related to the birth and growth of large-scale vortices.

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The objective of this study is to investigate a thermal field in turbulent boundary layer by means of direct numerical simulation (DNS), in which the wall heating is suddenly vanished in the downstream region, i.e., the wall is heated by a constant temperature condition followed by an adiabatic condition. The present DNSs conduct the spatially developing boundary layers with heat transfer using the generation of turbulent inflow data method. In this study, a constant temperature wall followed by adiabatic wall condition is adopted for a turbulent boundary layer along a flat plate. DNS results show clearly the statistics and structure of turbulent heat transfer in a constant temperature wall followed by an adiabatic wall.

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The aim of this research is to investigate the effects of freestream turbulence (FST) in a main flow on turbulent structure and heat transfer in turbulent boundary layers (TBLs) by means of direct numerical simulation (DNS). The FST is generated by a turbulence-generating grid as in previous experimental studies. The results show that instantaneous and mean temperature profiles are affected by the FST in the outer region of the TBL. The rms temperature normalized by the friction temperature is enhanced by the FST.

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Inner layer turbulent structures in a high-Re channel flow imposed wall-normal magnetic field were investigated by means of direct numerical simulation (DNS). Due to the magnetic effect, the large scale structure in a high-Re channel flow was suppressed. This degenerated turbulent structure can be characterized by the effective turbulent Reynolds number estimated by a gradient of the Reynolds shear stress. And we found that turbulent structures in this MHD flow has the similarity structures in the non-MHD flow of turbulent Reynolds number corresponded to this effective turbulent Reynolds number.

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This paper presents numerical results on heat transfer characteristics of turbulent gaseous flow in a micro-tube with constant wall temperature. The numerical methodology was based on Arbitrary-Lagrangian-Eulerinan (ALE) method to solve compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was employed to evaluate eddy viscosity coefficient and turbulence energy. The tube diameter ranges from 100 μm to 400 μm. The aspect ratio of the tube diameter and the length (L/D) is fixed at 200. The obtained Reynolds number ranges widely up to 10081 and the Mach number at the outlet ranges from 0.1 to 0.9. The heat transfer rates obtained by the present study are higher than those of the incompressible flow. This is due to the additional heat transfer near the micro-tube outlet caused by the energy conversion into kinetic energy.

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Recently, various detrimental substances exhausted from a large number of cars and/or factories have been making a large influence on living environments in the large urban area. Thus, it is necessary to predict accurately the diffusion processes of such substances in the city area, which has a very complex flow field because of the existence of various buildings in size and shape. To tackle this problem, we need simplify the flow field to find the relations between mass diffusion and the flow behind a building model. In the present study, we investigate experimentally the fluid-dynamical relationship between mean velocity and concentration fields formed behind the building model by focusing attention on the behaviors of the streamwise mass flux and turbulence intensity.

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Direct numerical simulations of chemically reacting turbulent mixing layer have been conducted to investigate effects of heat release on turbulent structures and fractal characteristics of turbulent scalar mixing. Fine scale eddies in roller structure and braid region are suppressed by dilatation induced by heat release. As the turbulent transition occurs, the fractal dimension increases linearly and reaches around 2.4. The development of the fractal dimension delays as a result of slower development of chemically reacting turbulence with heat release.

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This paper describes a thermal resistance measurement of pre-impregnated composite fibers (prepregs) in printed circuit boards (PCBs). To miniaturize electrical devices, electrical components are now embedded in multilayered PCBs and covered with multilayered prepregs made of glass fibers and epoxy resin. To estimate the accurate temperature of the components embedded in the prepreg, we should clarify the thermal contact resistance between prepreg layers around the components. In this study, we measured thermal contact resistance between prepreg layers and discussed the impact of the thermal contact resistance on estimation of temperature of the component.

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We have been developing the thermal conductivity measuring method of flat plate such as printed wiring board (PWB) in a direction parallel to the plane of the board by fin temperature fitting method. In this method, we applied the correlated heat transfer coefficient around the horizontally set specimens from the prior experiment with known thermal conductivity. From the experimental investigation, we obtained the following conclusions. (1) By using the correlated heat transfer coefficient, in-plane thermal conductivity of the horizontal specimen plate is obtained within 10 % dispersion in the range of fin efficiency 0.2〜0.8. (2) The thermal conductivity of 10 layered PWB was 3 times larger than the 2 layered PWB.

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In this paper, the thermal resistance caused by wage-type gap has been studied theoretically. This type of resistance is often encountered in the electronic equipment. As a first step to propose an estimation method of such resistance for simple thermal network analysis, the thermal resistance between two rectangular metal blocks which contact at one edge has been intensively studied. From a series of numerical calculations, the temperature field of the system has been shown, and further, the heat flow field in the two blocks contacting at only one edge has been clarified.

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The additional thermal resistance associated with the geometrical constriction is often encountered in the electronic components like relay circuits, the printed circuit boards, and so on. In these cases, heat is transferred frequently through a thin and narrow passage. In the present study, as a first step to propose an estimation equation for simple thermal network analysis of electronic components, the thermal constriction resistance of a thin plate has been intensively studied. Furthermore, heat flow of two thin plates connected by a narrow passage has been shown, and the effect of the plate length on the resistance has been clarified.

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This study describes temperature difference reduction among solder balls when solder balls are heated up with a uniform laser beam at a time by using CFD analysis. We focus on flexible printed wiring board. First, we detected the reason why temperature of each solder ball becomes different. Then, to reduce temperature difference, we designed light shielding mask. As a result, by using light shielding mask, temperature difference among solder balls can be reduced. Further, it can be concluded that heat diffusion through copper wires on the board is key point to design the mask.

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