Recent trend in research of critical heat flux (CHF) in boiling has been reviewed for pool boiling and simpler boiling systems from macro-and microscopic points of view in order to grasp fundamentals and to enhance better understanding of the CHF. A CHF model based on heat balance in macrolayer can provide a good clue for analyzing and deriving CHF correlation but does not include any information on surface conditions. In addition, a way to improve the CHF can be thougth to be progressing steadily in light of understanding of macrolayer. Another model related to microlayer has been developing and may be expected to bridge between nucleate and transition pool boilings. There seems for this model to show no way how liquid is supplied into heated surface and generated vapor escapes from the microlayer.

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In this study, the simultaneous measurement technique for three-dimensional density and three-dimensional velocity distributions was evaluated. The Holographic Particle Image Velocimetry (HPIV) was the technique to record the three-dimensional position of the tracer particle on the hologram. When there were density distributions in the interrogation region, the plane optical wave may be modulated because of the difference of the refraction indices. Then, both of the plane wave modulated by density and the spherical wave by particle scatter were interfered with the reference beam, being recorded on the single hologram. With reconstructing the hologram, the both of the modulated plane wave and spherical wave were reconstructed. Since the plane wave and spherical wave belong to low and high spacial frequency, respectively, the plane wave was reconstructed with the low-pass filter, resulting in the information of the density distributions to be obtained. With the high pass filter, the particle three dimensional positions were determined, i.e., the same procedure with the original HPIV technique. The effectiveness of the proposed technique (Filtering Extraction: FX) was confirmed through the Helium Jet experiment. The information of the density and velocity were separately measured.

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The present study quantitatively analyzes changes of flow patterns occurring in unsteady horse shoe vortex systems, using a flow visualization and spectral analysis for fluctuations of velocity, u', measured by PIV. Experiments were performed for flows around an obstacle mounted on a fiat plate in a water channel. In the spectral analysis, the auto correlation, the power spectrum and the cross correlation were investigated for the velocity data measured at the core of vortices. The flow visualization employed was devised so as to be able to made the images of unsteady flows. As a result, the flow patterns in the transient process were characterized quantitatively, where the changes of flow patterns were classified by both of the flow visualization and the spectral analyses.

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A doublet flow is the circular jet added the annular suction flow mounted on the same axis by using a double coaxial pipe. This flow was proposed for the purpose of diffusion control of a circular free jet. The doublet flow was measured by using PIV. The effects of the diameter ratio of suction pipe to injection pipe on the time mean characteristics and the unsteady characteristics of two dimensional flow field were examined. From the analysis of the time mean characteristics, it is clarified that the fluctuating velocity increases by adding the suction flow in all cases of the diameter ratio. Therefore, it is found that the doublet flow has the superior effect of the diffusion compared with a circular free jet. And the cause of the increase of the fluctuating velocity is clarified by the analysis of the unsteady characteristics. Furthermore. the experimental equations which can predict the fluctuating velocity were proposed.

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Experimental study was conducted to examine applicability of Pyragas' Delayed feedback control theory for active control of fluid flow. Although many attempts of turbulence active control have been made, most of those experimental studies experience "out of control" state in the case of using larger feedback gain. In the present study, we assume this "out of control" state as Chaos, and apply chaos control theory to prevent the flow field from falling into "out of control" state. Experiments were carried out for low Reynolds number oil flow in a rectangle thin container, whose aspect ratio is 6 : 1 : 0.5. Two pulsed jets were used as actuator in order to keep the circulation of the flow in container constant. Fluid flow was observed using Particle Image Velocimetry (PIV) technology and the flow state was estimated by moving least square (MLS) method. As a result, we found that Pyragas Control was effective to prevent Chaos for active control of fluid flow.

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Air flows in a heater unit for automobiles are studied by flow visualization with tracer injection technique and the visualized images are analyzed by cross correlation method to obtain the velocity distributions in the unit at various mixdoor angles. The results indicate the variations of flow pattern in the heater unit with the mixdoor angles and the appearance of strong interaction between separated main flow and circulating heater flow at relatively large mixdoor angles, which promotes the flow mixing and simultaneously increases the pressure loss inside the unit. The flow fields in the heater unit are calculated numerically based on three dimensional momentum equations combined with κ-ε model of turbulence and with an experimental flow model of heater core. The numerical results reproduce well the experimental flow patterns in the heater unit, but there exits some deviations in the mean velocity and surface pressure distributions at large mixdoor angles.

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The two-dimensional (2-D) OH concentration distribution in an axisymmetric coflow methaneair diffusion flame was measured by using planar laser-induced fluorescence (PLIF) technique. On the other hand, the flame structure was calculated numerically by using a detailed chemical reaction mechanism and the accurate thermal and transport properties. The adopted mechanism was GRI mechanism involving 49 species and 279 elementary reactions. The derived flame structure made it possible to obtain the 2-D distribution of the collisional quenching rate and thus to evaluate its effect on the OH fluorescence emission distribution. The evaluation has revealed that the effect is not appreciable and the PLIF method is a convenient and reliable technique to obtain the 2-D relative concentration distribution of OH.

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The two-dimensional (2-D) NO concentration distribution in axisymmetric coflow methane-air diffusion flame was measured by using planar laser induced fluorescence (PLIF) technique. On the other hand, the flame structure was calculated numerically by using a detailed chemical reaction mechanism and the accurate thermal and transport properties. The adopted mechanism was GRI mechanism involving 49 species and 279 elementary reactions. The derived flame structure made it possible to obtain the 2-D distribution of the collisional quenching rate and thus to evaluate its effect on the NO fluorescence emission distribution. The evaluation has revealed that the effect is not appreciable and the PLIF method is a convenient and reliable technique to obtain the 2-D relative concentration distribution of NO.

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Studies were made on the development of a digital imaging technique using double-pulsed laser-induced fluorescence (LIF) for detailed visualization and novel measurement of high-pressure diesel fuel spray. Rodamine B (C₂₈H₃₁CiN₂) was chosen for fluorescent dye and dissolved in the diesel fuel, 0-solvent. The second harmonic of a double pulsed Nd: YAG laser (532 nm wavelength and 7 ns pulse width) was used as a light source for exciting fluorescent dye. The combined use of a high definition CCD camera and a specially-designed synchronization system has enabled well-resolved digital images of diesel fuel spray to be acquired with a thin laser sheet pulsed twice at an arbitrary time separation. This technique was shown to be capable of visualizing clearly not only overall spray structures but also deeply internal structures with spatial and temporal resolutions high enough for quantitative particle sizing and velocimetry in the core of the spray.

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The effect of the structure and behavior of pseudo shock wave on jet noise containing discrete frequency has been studied by digital image processing. The shock waves were visualized by Schlieren method or a high-speed camera, and the motion of the over-compression regions was studied by the digital image processing. It was clarified that the behavior of over compression regions was periodical, and these periods were closely related to the generation of discrete frequency noise.

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As is by now well known, partial differential equations based on a one dimensional, one-pressure two fluid model are mathematically ill-posed as an initial-value problem. Up to the present, however, eigenvalue analysis of the two fluid model has been conducted only for a simplified two-fluid model without any source terms, since a necessary condition of well-posedhess can be derived from differential terms only. Consequently, effects of source terms have not been systematically investigated. In the previous report, we proposed the method to examine mathematical nature of the complete two-fluid model including source terms ; the effects of gravity were evaluated using this method. As a result, it was confirmed the two fluid model can be mathematically ill-posed due to source terms. In the present study, the effects of interfacial drag force and wall friction force were examined using the same method. The effects of virtual mass force were also evaluated, since its influence has not been clarified in spite of the fact that it can affect the numerical stability.

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This study is concerned with the proposal of a lattice BGK model with the internal degrees of freedom in the lattice Boltzmann method, which is a numerical method on the assumption that a fluid consists of many microscopic particles repeating the translation and the collison. The collision operator in the lattice BGK model employs the single time relaxation parameter introduced by Bhatnagar, Gross, and Krook in order to simplify the collision term in the Boltzmann equation. The particles in this model possess another freedom of enegy in addition to the energy of translation, and the internal degree of freedom increases. We assume that this energy distribution can approach the equilibrium state through the collision with the same manner as the number density of particles. In the numerical simulations of fluid flows, the results obtained by this model agree well with those by the finite difference method.

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This paper describes a numerical study of dynamics and efficiency of a two-joint bending propulsion mechanism that is composed of a streamlined body and a caudal fin. We used the quasivorrtex-lattice-method in order to analyze the lunate caudal fin, comprising the slender body theory for the body. Firstly, we examined the characteristics of the propulsive efficiency of various types of the caudal fins only. It was found that the propulsive efficiency of three dimensional analysis becomes lower than that of two-dimensional analysis and that large swept angle causes reduction of the propulsive efficiency. Next, we investigated the characteristics of the propulsive efficiency of the whole mechanism including the effect of the body. The propulsive efficiency of the whole mechanism exhibited similar tendency to that of caudal fin only, although the propulsive efficiency of the whole mechanism becomes lower than that of caudal fin only, especially at low reduced frequency. Finally, by comparing the calculated results with some observed data of dolphin, it was found that the optimum motion parameters, which gives the highest propulsive efficiency, agree well with the dolphin's motion parameters.

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The natural convection with large temperature difference is computed numerically using the Low-Mach-Number approximation with temperature dependent viscosity and thermal conductivity. In this study staggered grid system is used in order to hold down the numerical oscillation. Firstly, steady laminar natural convection above a horizontal heat source is simulated in order to validate the simulation method. The result is in good agreement with the analytical solution. Secondly, two dimentional flow field driven by two parallel heat sources is computed. This boundary condition may be regarded as a model situation of the big fire covering both sides of a wide straight road. At the same time, it is interesting to investigate interactions between two thermal plumes. The numerical results disclosed different flow behavior when the imposed temperature of the heat sources is changed and the rest of the governing system parameters are varied.

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The conventional shape function for the finite-element method (FEM) is a linear one, which is inadequate for analyzing numerically complex flows for high Reynolds numbers. In the present study, we propose GSMAC-CIP scheme using 3rd order shape function which requires continuity of the value of the function and its first space derivative in whole space and is formulated a finite element method for the cubic interpolated pseudo particle (CIP) method. We verified the effectiveness of this new scheme by the forced convection in a square cavity at Re=1 000, 5 000, 10 000. The numerical results obtafined by the present scheme is compared with those of GSMAC-FEM using rough meshes and it is showed that present scheme is superior to GSMAC-FEM on the space accuracy. Moreover, it is shown that the numerical results obtained by present scheme using fine meshes are agreement with those obtained by Ghia et al.

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The flow around a circular cylinder standing on the sand is computed numerically and the movement of the sand is investigated. The numerical method employed in this study can be derided into three parts: (1) calculation of the air flow around the cylinder using MAC method with a generalized coordinate system; (2) estimation of the sand transfer caused by the flow through the friction; (3) determination of the shape of the ground. Since the computational area is changed due to the step (3), this procedure has to be repeated for the next time step. From this simulation, it is found that the horseshoe vortex scoops out the ground in front of the cylinder and that the wake makes the sand accumulate in the rear region. The dented region becomes deeper as the cylinder leans to the windward.

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An experimental study has been carried out for an air jet with swirl discharging from a nozzle along a solid surface. Mean and fluctuating velocities are measured by rotating a probe with an inclined hot wire. Flow pattern of mean and secondary stream in cross section and distribution of Reynolds stress are shown, and physical explanations are offered for phenomena peculiar to the wall jet with swirl. The experimental results are compared with the existing ones on the air jet with swirl coming into stagnant-air surroundings, and the effects of the solid surface on the jet are elucidated.

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Experimental study is carried out to clarify the flowfield of the duct flow with an inclined jet injection, as the model test of a tunnel ventilation facility. A 7700 mm long duct with a 230 mm×230 mm square cross section is constructed, and an injection nozzle with 20 mm×230 mm outlet with the angle of 30° is installed at 2100 mm from the inlet. In addition to full span injection cases, the nozzle with 40% span (symmetric) or 50% span (one side) is installed to observe the effect of the outlet span on three dimensionality of the flowfield. Measured pressure gains under various flow ratios showed good agreement with the theory based on the law of momentum. The velocity distribution with full span injection showed the flowfield in which high speed regions are confined at the ceiling due to Coanda effect, while the partial injection cases revealed stronger down wash.

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Aerostatic journal bearings are employed in a lot of engineering fields because of the high endurance under severe conditions in current technology. However, it is difficult to investigate the flowfield experimentally, since the flow region of an aerostatic journal bearing is formed by a clearance of micron order. The present study numerically clarifies the flow in a pressurized journal bearing with a circular slot restrictor and the effect of a slit which is used to measure the static pressure. In this study, the flowfield is assumed to be laminar and compressible, and thus the compressible Navier-Stokes equations, equation of continuity and energy equation are solved. The static pressure distributions obtained by our computations are in good agreement with the experimental data, especially under the conditions of small bearing clearances. Furthermore, it is shown that a shock wave is formed around the impinging region at large mass flow rates, and the influence of a static pressure slit should be taken into account to estimate the static pressure reasonably.

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Numerical studies of establishment of selective withdrawal from a point sink of a linearly stratified Boussinesq fluid in a reservour of uniform depth have been performed. The flow, which is axisymmetric with respect to the vertical axis passing through the point sink, is mainly characterized by the Froude number (Fr). When the Froude number is small, the columnar disturbance modes propagate upstream in the same manner as in the line sink flow (two dimensional) case and that the selective withdrawal is established. We have found, however, the major difference in the large Froude number flows, where in the two dimensional case the columnar disturbances can not propagate upstream, while in the axisymmetric case these can propagate upstream for any finite Froude number except infinity. Amplitude of these columnar disturbances relative to a basic current velocity becomes smaller as the Froude number increases so that the selective withdrawal ceases to occur at Fr=1.5.

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A liquid film flow field on a roll coater consists of the upstream bank and film split region. In this paper, the behavior of a liquid film flow inside the upstream bank is analyzed. An approximate formula and numerical simulation including the effect of surface tension are used. A two-dimensional finite volume method is adapted for the numerical simulation. The marker and cell method is used in order to calculate the free surface of the liquid film. Velocity and pressure distributions are shown. Two counter-rotating eddies exist in the upstream bank between the substrate and roll. The pressure gradient inside the liquid film depends on the size of the upstream bank. The surface tension around the upstream bank decreases the pressure gradient. The relationship between the size of the upstream bank and coating film thickness is made clear.

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Numerical simulations with two way coupling were performed for downward particle-laden turbulent flows in a vertical channel. The effect of inter particle collision on the motion of particles and the turbulence modification was studied. Fluid motion was calculated by using LES with the same models as in single phase flows and the motion of individual particles by the Lagrangian method. Some results were compared with measurements by Kulick et al. (1994). It was found that the effect of inter-particle collision on particle diffusion manifests itself even at low particle volume fraction of the order O(10^<-4), and that the inter particle collision makes the particle fluctuation intensity and the profile of mean particle velocity aproach to experimental measurements.

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The turbulent drag reduction by means of polymer coating was investigated in a rectangular channel flow. The wall surface was coated with a water-soluble polymer that exhibited turbulent drag reduction as a solution. Two coating method were applied to the channel wall. In the first method, a binding polymer solution was mixed with an additive solution, and the mixed solution was applied and dried on the wall. The additive molecules were anchored on the wall by the binding polymer. This coating method produced the drag reduction of 7% at Re-4000. The drag reduction disappeared in high Reynolds number, and its mechanism was supposed to be different from normal Toms effect. In the second method, the additive power was stuck with paste on an adhesive vinyl tape, which was fixed on the wall surface. The drag reduction obtained was dependent on time. The reducing rate was 4.5% after 10 minutes, and 0% after 60 minutes. In this method, the solved polymer played an important role in the drag reduction. These coating methods are expected to open new additive application for outer flow.

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The experimental study has been conducted on the influence of the periodic perturbation on the separated flow over a backward-facing step. In order to investigate the large-scale eddy motion, which is evolved from the step edge due to the periodic suction and injection, the Particle Image Velocimeter has been introduced. The effect of the perturbation is obvious in reduction of the reattachment length, providing at most the reduction by over 30% against that of the steady flow condition. The investigation on the turbulent transport term in the mean momentum equation reveals the increase in the individual components of Reynolds stress is responsible for the activated momentum transfer across the shear layer, which in turn results in the earlier flow reattachment. The general tendency is in good accordance with other studies in past, though the relative level of the turbulent shear stress is somewhat low. Further investigation on this point is necessary.

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The effect of tangential blowing on the performance of subsonic diffuser for a supersonic air-intake was experimentally investigated in order to develop a high performance subsonic diffuser with short length. The results show that remarkable improvement of diffuser performance can be achieved by tangential blowing into flow separation region. In particular, with a blowing mass flow ratio of 0.063 from both-side blowing a gain in the pressure recovery of 11.5% and an improvement in distortion of 68.7% are obtained. Therefore, a technology potential of the tangential blowing for shortening of diffuser which leads to weight reduction of the air-intake is demonstrated.

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A new measurement system for velocity distribution based on a low-coherent interferometry is examined. A low-coherent source has a broad spectrum in the oscillating frequency. That is, an interference output with the low-coherent source is obtained only when the path lengths of both a reference light and a scattered light are coincident in an interferometer. Therefore, a depth with the scattered light can be specified by adjusting a path difference in the interferometer. A superluminescent diode (SLD) provides an optical source with a low temporal coherence. In the present paper, the measurement system with interferometric technique by use of SLD has been successfully developed to be an anemometer which is capable of travers measuring a velocity distribution along a depth in a flow passage. The light beam emitted from the SLD forms a Michelson type interferometer, in which to move a mirror reflecting the reference light means to traverse a velocity profile along the depth at each chosen location. A fluctuation of the interference output is detected and is Fourier-processed. A flow velocity is calibrated by the width of the half peak value of the Fourier spectrum. The measurement result agrees well with the theoretical velocity profile.

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In order to clarify the attenuation and distortion of a pressure wave propagating in a constant area tube, experimental study has been carried out. Weak shock waves (M_s<1.1) were created using an open end shock tube. Experimental results show that the strength of a shock wave decreases exponentially with distance. The attenuation rate of wave strength is affected by the initial strength of the shock wave and by the unsteady boundary layer induced by the wave front. The shape of a weak shock wave becomes different with the propagation distance; that is, a compression wave appears just behind the shock wave front. And an overshoot is observed behind the shock wave front, because of the transition of the boundary layer.

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The purpose of this work is to clarify nonequilibrium condensation of alternative Freon on the cold wall behind the incident shock wave. Experiments have been carried out with a diaphragmless and low temperature shock tube to measure the growth of condensed liquid film. The time dependent thickness of condensing liquid film is measured by an optical interferometric method based on multiple reflections of a He-Ne laser beam. By simultaneous measurements at two different locations, it is experimentally confirmed that the liquid film grows uniformly on the same temperature cold wall. It is also found that growth of the liquid film thickness depends on the nonequilibrium degree of pressure (p^*₂=p₂/p_sat) that includes informations of P₁ and Mi, under the same temperature conditions. From these results, we can clarify the tendency of liquid film growth on the value of nonequilibrium degree of pressure.

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The aim of the present study is to investigate the nonequilibrium condensation of alternative Freon on cold wall behind the incident shock wave. To clarify the tendency of temperature increase of liquid film, one dimensional unsteady heat conduction equation has been solved using theorem of Duhamel. It has been found that except in the very beginning of nonequilibrium condensation, the temperature rise of liquid film is not influenced by initial experimental conditions. As a result of our simultaneous observations of interferometric signal from liquid film growth and flow/liquid film visualization, it is observed that many ripple and tiny disturbances have occurred on the condensed liquid film surface after the range when the interferometric light signal presenting the liquid film growth is terminated. It is thought that the disturbances strongly scatter the interfering laser beam. We consider these disturbances are originated from an instability on the film interface between vapor and liquid.

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To realize micro maintenance robots for small diameter pipes of nuclear reactors and so on, high power in-pipe mobile micromachines have been required. The authors have proposed the bellows microactuator using fluid power and have tried to apply the actuators to in-pipe mobile micromachines. In the previous papers, some inchworm mobile machine prototypes with 25 mm in diameter are fabricated and the traveling performances are experimentally investigated. In this paper, to miniaturize the in pipe mobile machine and to make it adaptable to pipe diameters, firstly, a simple rubber tube actuator constrained with a coil-spring is proposed and the static characteristics are investigated. Secondly, a supporting mechanism which utilizes a toggle mechanism and is adaptable to pipe diameters is proposed and the supporting forces are investigated. Finally, an in pipe mobile micromachine for pipes with 4-5 mm in diameter is fabricated and the maximum traveling velocity of 7 mm/s in both ahead and astern movements is experimentally verified.

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Effect of the flow characteristics in a newly developed micro-machined sheath flow chamber on the accuracy of cytometric analysis was investigated. The chamber was formed by laminating three 100-μm-thick photo-etched metal plates. Sample fluid containing cells, which enters the chamber via an axial specimen nozzle, is enveloped by a buffering sheath-fluid and transported to a capillary channel. Microscopic observation and three-dimensional viscous flow analysis predict that the dispersion of cells in the capillary channel is favorably reduced when the Reynolds number is around 500∼750, which is value associated with low deviation of the analytical results. The five classifications of human white blood ceils were determined, and this verified that change of the deviation depends on the Reynolds number. The results confirm Reynolds number of around 500∼750 is a appropriate for good classification.

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Experimental studies were carried out on the performance of three vortex shedders used for vortex flowmeter in a circular pipe: one is a trapezoidal cylinder used as a practical device and the other two are a circular cylinder with a two dimensional slit along the diameter and a triangular-semicylinder which accompanies alternative boundary layer suction and blowing. The vortex shedding frequency was measured by the fluctuating pressure on the surface of the vortex shedder. The pressure loss of the two shedders with a slit is reduced by 50% compared with that of a trapezoidal cylinder, and the two shedder is superior in linearity, regularity, sensitivity and range ability to the trapezoidal cylinder.

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Research was carried out to study the leakage characteristics of pollutants, contained in the exhaust gas emitted by motor vehicles, from exit portals of long road tunnels which have longitudinal ventilation systems with supply and exhaust shafts. Apart from theoretical studies, an actual one-way traffic tunnel, 6200 m in length, was studied as well.

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The flow model and loss model in the rectangular scrolls constructed from the main flow with free vortex flow, the 3D equilibrium boundary layer on the side walls and the 2D boundary layer on the inner and outer walls, and the equation to estimate the loss in it were made in this research. The model is based on the theory of the 3D equilibrium boundary layer. The calculated results of it are shown good coincidence with test results. The flow equations are made from the 3D boundary layer equation with 1/n multiplier law and Mager's equation, and main flow with free vortex flow. Those equations have three unknown variables which are n, boundary layer thickness and radial velocity parameter. The mean outlet flow angles are estimated by using the values of those three variables decided by the measured volocity distributions. It is made clear that the flow rate of main flow is reduced by the flow through the 3D equilibrium boundary layer and the outlet flow angle become small at the main flow, and the loss less main flow is sustained for being main flow.

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In order to develop a high performance air turbine having simple structure for wave energy conversion, an impulse turbine with fixed guide vanes has been presented and investigated experimentally by model testing. As a result, a suitable choice of the design factors has been clarified for rotor blade inlet (or outlet) angle and guide vane setting angle of the turbine. Furthermore, it is found that the running and starting characteristics of the present impulse turbine are superior to those of a Wells turbine under irregular wave conditions.

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In order to improve the performance of a Wells turbine, the porous fences have been equipped on the hub wall upstrem and downstream of the rotor. The effects of the gap between the porous fence and rotor, porosity and height of the porous fence have been investigated by model testing. The results have been compared with those of the case without porous fences. As a result, it is found that the starting characteristics are improved by the porous fences. Furthermore most of the configurations tested have shown improvements in the operation range primarily by postponement of stall. A suitable choice of design parameters for the turbine has been suggested.

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A method is developed to analyze the three-dimensional transient Marangoni convection in a liquid droplet heated by a concentric warm rigid sphere set in the center and cooled uniformly from its surroundings. As the system is unstable and the convection is very sensitive to the temperature gradients along the surface, it is required for the scheme to be highly accurate and be free from the effects of the polar singularities. For the purpose, a spherical harmonic spectral method is developed to analyze the flow and temperature fields in the droplet on the three-dimensional spherical coordinate system. The newly developed method gives almost the same pattern of results for two systems with the same pattern of initial temperature disturbances on coordinate systems which are shifted by 90° in each other. This indicates that the present method is free from the effects of the direction of the coordinate system, and shows the validity of the method.

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This paper presents a practical method of numerical analysis for boundary shape design of steady-state heat conduction fields to control temperature distribution to a prescribed distribution. Reshaping was accomplished by the traction method that was proposed by one of the authors as a solution to domain optimization problems in which elliptic boundary value problems were defined. In this paper, we formulated a temperature square error norm minimization problem between prescribed distribution and actual distribution on prescribed boundaries and theoretically derived shape gradient function for this problem. We developed a convenient numerical method using a general-purpose FEM program for the temperature prescribed problem. The successful results for two-dimensional problems of a erosion surface on blast furnace hearth and a coolant flow passage in turbin blade show the validity of the presented method.

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This study was researched by a numerical analysis and experiment, on a natural convection heat transfer in a oriented horizontal elliptical annuli between heated outer tube and cooled inner tube. The outer tube was elliptical tube, and inner tube was cylindrical tube. It was experimented with the outer tube oriented to vertical side, slant upper side 45 degrees, horizontal side, respectively. The numerical analyses were performed by changing the elliptical ratio, inner tube radius, oriented angle, and Rayleigh number as parameters. Results obtained for different conditions are presented as temperature profiles, flow patterns, local Nusselt number, and total heat transfer. It was presented that the heat transfer enhancement effect or heat transfer obstruction effect for the total heat transfer by oriented angle.

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A quantitative estimate of heat transfer enhancement is discussed here based on the measuements of local coefficients of heat transfer and friction for air flow over a range of Reynolds number from Re=9400 to 28200. Pairs of vortex generators consisting of two rectangular blades, increasing linearly in separation downstream, are aligned laterally to the flow with a spacing W. Characteristics of spanwise local heat transfer and pressure coefficients are found to vary differently over two regions of W. For small W, the phase of their distribution is shifted by 180° from the patterns observed just downstream of the blades. For large W, no phase change is observed but changes of the pattern between paired blades are distinctive. Overall heat transfer coefficients are more than double those for a smooth duct without generators. As a result, the performance ratio is greater than unity for all values of W.

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High heat flux far exceeding CHF is accomplished in micro bubble emission boiling (MEB) which appears in transition boiling region under some condition of liquid subcooling and velocity. It is necessary for discussion of heat transfer mechanism in MEB to understand how the liquid is supplied to the heated surface, which should be achieved by sincere observation of bubble motion on the surface. In this study bubble height and diameter are measured from high speed film and analyzed for S-MEB I occurring on a horizontal surface in parallel flow of water. The bubbles collapse against the surface with high collapsing rate. The collapsing rate that is the decreasing rate of the bubble height increases with increasing of the heat flux. This collapsing motion is supposed to carry the liquid to the surface like a micro jet in cavitation. As a result of the analysis using an equivalent bubble radius, the radius tends to decrease along the curve of the Rayleigh solution, which means bubbles collapse under inertia control rather than heat transfer control, ill high heat flux region of S-MEB I.

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The alkali metal thermal to electric converter (AMTEC) system which utlizes the sodium ion conductivity of beta"-alumina solid electrolyte (BASE) is expected to have high conversion efficiency above 30% including practical heat loss. However, the achieved experimental efficiency have been around 15%. In this paper, current voltage characteristics and heat and mass transfer processes on a single cell have been examined experimentally and thermal electrode conversion efficiency has been discussed. Measured electrode conversion efficiency without thermal losses showed that it was about 40% at a power density of 0.3 W/cm². A theoretical analysis on the thermal losses has also been conducted and these losses are estimated 0.3 W/cm² in a practical tube type cell, so it is obtained that the actual cell system efficiency of 30% will be expected.

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R22 (HCFC22) has been widely used as the refrigerant in refrigerators and air conditioners. According to the Montreal protocol for ozone layer protection, the total amount of HCFCs was capped from the beginning of 1996. Zeotropic refrigerant mixture R407C and azeotropic refrigerant mixture R410A have been selected as the promising alternative refrigerants of R22. This paper examined the passage of R407C refrigerant in heat exchangers through simulation, and obtained the following results. In the heat exchangers used in heat pump type room air conditioners, a counter flow configuration when operating as condenser had high efficiency. In outdoor heat exchangers operating as evaporators, a configuration that restrained temperature glide by partly reducing refrigerant passage had not only high efficiency but also reduced the formation of frost on coils.

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This paper describes an analysis of the effects of the specific heat of the regenerator material on the refrigeration capacity of a 4K GM refrigerator. The facts revealed by the analysis are given below. When the specific heat of the regenerator material is changed from 1.5 J/(K·cm³) to 0.01 J/(K·cm³), the no load temperature is changed from 2.11 K to 26.9 K. The lowest temperature that can be theoretically attained in this refrigerator is the temperature around the λ point of helium. The specific heat of the regenerator material reaches a sufficient level at 0.8 J/(K·cm³). The refrigeration capacity is found to be superior over a wide temperature range when the specific heat distribution is uniform than when it has a peak. When regenerator materials of different types are stacked in stratified formation, the material stacked at the cold part of the regenerator may have a small specific heat at high temperatures, but the material stacked at the hot part of the regenerator should desirably have a large specific heat at low temperatures.

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As a Birchley-Riley's fuel droplet consisted of an aqueous core embedded within a liquid fuel shell was heated in the electric furnace, the puffing and the microexplosion were observed. The waiting time for microexplosion was dominated by water content, droplet volume, fuel type and ambient temperature. When the waiting time data plot was fitted by Weibull distribution, its shape parameter was equal to 2 and the microexplosion phenomenon was classified as wear out failure type.

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In direct Internal Reforming Molten Carbonate Fuel Ceils (DIR MCFC) deterioration of catalytic activity takes place in the anode channel since the molten carbonate sometimes leaks and vaporizes there. In order to identify the process in DIR-MCFC, not only the activity of catalysts polluted in practical DIR-MCFC systems is evaluated, but also the important factors to deteriorate the catalytic activity are elucidated by using artificial polluted catalysts manufactured in this study. One of the deterioration factors in the practical systems affect quantitative and/or qualitative sintering. KOH mainly contaminates the catalyst rather than LiOH. The reaction rate constant of methane reforming reaction decrease with increasing the pollution ratio. However, the contamination does not act covering the active sites on the catalyst, and the overall reaction rate is not controlled by diffusion either into the pore or film surrounding the catalyst. If anything, vaporized KOH may enter into the micro pores, and results the decrease of active sites. In addition, the sintering phenomenon does not directly relate to the pollution. If the catalysts sinters, temperature of catalysts raises up since the reforming reaction indicates endothermic reaction. As the results, the temperature of catalyst attains the sintering temperature.

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This study is an attempt to burn pulverized Refuse Derived Fuel (p-RDF) made from municipal solid waste (MSW) with a view point of recycling of waste resources from daily domestic and industrial processes. In order to obtain fundamental data on p-RDF combustion, the ignition and combustion behavior of the particles of RDF and its component materials such as plastics (polypropylene, polystyrene), fiber (nylon) and paper (newspaper) were observed in an electric furnace. The ignition delay and the burning period of particles both p RDF and its component materials were investigated under specified furnace temperatures and particle sizes of each material. The results indicated that each component material of p-RDF had different ignition and combustion mechanism in processes such as volatilization, ignition and visible envelope flame. The values of the ignition delay and the burning period of plastics and fiber were larger than those of paper, and RDF showed medium values between them. The estimated activation energies for plastics and fiber were larger than paper, and RDF showed medium values. Each component material of p RDF showed different activation energies which led to different ignition delay and burning period.

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By incorporating the scalar field variable, G, into the numerical method with the flame sheet model, one of reaction models of simulation of diffusion flames, we have developed a new calculation method of lifted flames. The present method can deal with the flame instabilities including the blowoff, liftoff, and extinction, while the conventional flame sheet model cannot deal with them, because scalar quantities are decided uniquely against the mixture fraction in that model. The burning velocity included in the production term of the equation of scalar field variable, G, is formulated as a function of the scalar dissipation rate. This makes the treatment of the flame instabilities possible. The frozen scalar structure is applied to the upstream of the intersection of isolines of the stoichiometric line and G=1, the transitional structure expressed by a weight function based on the scalar field variable, G, to a small zone behind the intersection, and the diffusion flame structure to the downstream region. Numerical results of a reactive two dimensional mixing layer by the present method are in reasonable agreement with results of direct numerical simulations with a finite reaction rate and irreversible one step reaction model.

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