This paper is concerned with the three-dimensional thermal lattice Boltzmann BGK model which can be applied to the numerical analysis of fluid motions. In the model proposed here, the local equilibrium distribution of microscopic particles is represented more simply than some previous lattice BGK models. In the numerical simulations of three-dimensional fluid flows to examine the feature of this model, the viscosity and the one-dimensional propagation of shock wave appear appropriately, compared with the other numerical results. In the unsteady shock wave flow around the cubic body, the reflection can be observed. These results show that it is possible to apply the lattice Boltzmann method to practical analysis of fluid motions with the compressibility.

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Numerical investigations are made of establishment of two-dimensional selective withdrawal through a line sink of a linearly stratified Boussinesq fluid in a finite-depth duct. The flow is mainly characterized by a Froude number. When the Froude number is small, the internal wave modes of horizontal wavenumber and frequency 0 which are also called columnar disturbances propagate horizontally upstream against the induced uniform velocity and the selective withdrawal is established. We introduce the new method to specify the propagation of internal wave mode from numerically obtained velocity distribution. Using this method, we investigate its behavior especially focusing our attention on its vertical structure, amplitude and horizontal group velocity. The numerical results show that the amplitude becomes smaller as the Froude number or the mode number increases, and the group velocity of higher modes is inversely proportional to the mode number.

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It is the most important problem for the valve performance whether fluid is shut off or not, but sealing mechanism of valves has not been analyzed theoretically taking account of relationship between a sealing device and a valve disc even no flow in valves. Sealing devices used in valves have been designed basing on only experience and experiment whenever materials and/or size of parts were changed. In this work, taking up the seal of cylindrical type used in cam flex valves and some butterfly valves and considering numerical relationship in sealing devices, discs, shafts and fluid in valves, an applicable method based on thin cylinder theory and experimental results is proposed. This method yields results which are consistent with behavior of sealing devices, enables theoretical design of valve parts, especially, seals, discs, shafts and bearing devices in a standpoint of the strength and sealing behavior, and gives one-step anaysis of the valve behavior itself even in bidirectional flows.

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In the previous paper or analysis of a valve seal, it was shown that sealing mechanism of some valves which have a seal of cylindrical type can be analyzed theoretically by using the cylinder theory on condition that a valve is in the pressure of normal flow and the valve shaft has no influence on performance of valves. But it is recognized distinctly from experiment that the valve shaft and its bearing have great influence on shutoff-performance of valves. In this work, taking account of the valve shaft, the method is applied to analyze sealing mechanism of a valve seal in no flow and bidirectional flow, and developed for analysis of the behavior of a valve itself. This method yields results which are consistent with behavior of a sealing device, besides it gives good explanation for the particular behavior of a valve.

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Evaluation of champagne effect is indispensable for successful commercialization of a compressed air energy storage (CAES) system which is one of the most promising candidates of energy storage system. In the present study, we examined optimum design of the CAES system through numerical calculations of the champagne effect based on a two-fluid model. As a result, the following conclusions were obtained. (1) Charging rate of air into a lower reservoir should be gradually changed during startup and shutdown periods to avoid pressure oscillation in the lower reservoir. (2) If the water level in the lower reservoir is too low when the charging is finished, the inertial force makes the water level enter into the U-bend, which also induces the pressure oscillation in the lower reservoir. (3) If appropriate procedures are adopted during the startup and shutdown period of air charging system, the water level in the lower reservoir does not enter into the U-bend. The construction cost can hence be reduced by shortening the U-bend.

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A new Lagrangian numerical simulation technique to calculate concentration fluctuation fields by a non-buoyant plume in grid generated turbulence has been developed. Lagrangian velocities of the fluid particles in the downstream decaying turbulence are simulated by the summation of unsteady random Fourier modes. Then, the backward diffusion technique of particle-pair is applied to the prediction of scalar statistics. Simulations of two types of scalar fluctuation fields (of a point source plume and of a line source plume in a grid-generated turbulence) have been made and the simulation results are compared with the experimental data. As a whole, the pressent new model gives good predictions of the actual scalar fluctuation statistics in both cases, although near the line source there still exists some inevitable deviation caused by meandering effect between simulation and experimental results.

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The scattering of an oxygen gas molecule from a clean graphite surface is simulated using the molecular dynamics method. According to our previous report, the numerical simulation has shown quantitative agreement with experimental results, indicating that the method can simulate the trajectory of a scattering gas molecule with high accuracy. Here, the translational and rotational energy distribution after the first collision is analyzed. The translational energy distribution is fitted to a gaussian distribution. The parameters obtained by the fitting process obey the model equation that was obtained by assuming that the gas-surface collision is an ellipse hitting a hard-cube. The rotational energy distribution is fitted to the Boltzmann distribution and the non-Boltzmann distribution. The parameters for rotation also obey the model equation. Also, the vibration of the potential energy surface was analyzed and it was found that the amplitude can be defined as a function of surface temperature.

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The Multi-Stage model for diatomic molecules scattering from solid surfaces is presented, which is based on the large body of data obtained from molecular dynamics calculations and molecular beam experiments. The molecular dynamics method is used for the numerical analysis on the scattering of an oxygen gas molecule from a clean graphite surface. The angular and velocity distribution agrees well with experimental results, which was shown in our previous report. The scattering direction, translational energy and rotational energy of the gas molecule after each collision is saved for the data base. The basic idea of the model is to separate the collision into different stages. At each stage, the energy loss, the scattering direction and the trapping probability of the gas molecule will be determined. The angular and velocity distribution of the model agrees with those of molecular beam experiments.

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The oscillatory motion of a nonspherical gas bubble near a plane rigid wall is investigated using the boundary element method combined with the finite volume method. Heat transfer inside the bubble is taken into account in the analysis. We compare the present numerical results with both theoretical ones using a series expansion of spherical harmonics and numerical ones using an effective polytropic index. It is shown that when the bubble oscillation is moderate, the theoretical results are in good agreements with the present numerical ones. However, the results of polytropic analysis overestimate the amplitude of bubble oscillation. It is also shown that the temperature distribution inside the bubble is much dependent on the initial bubble radius. The thermal damping is important in dealing with the nonlinear oscillations of the bubbles. When the initial bubble radius is small and the driving frequency is out of resonant one, the thermal damping affects surface oscillations as well as radial oscillations more strongly.

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This paper describes the effect of the spacing between two adjoining circular cylinders on the flow around two-dimensional circular cylinder bundles of three rows in forced vibration. The experiment was carried out in an N. P. L. blow-down-type wind tunnel with a working section of 400×400×2000mm, at the Reynolds number 9.4×10³. The flow visualization experiment was done in water channel. The cylinders were then forced to oscillate sinusoidally in the lift direction. The time-mean and fluctuating surface pressure distribution on the circular cylinder were measured for the displacement in the vibration. The present results were compared with those for the case of fixed circular cylinder, the first report and the existing results. Consequently it was found that (i) the phase lead occurs between fluctuating lift and vibrating displacement in an in-phase mode vibration and an out of phase lead occurs between fluctuating lift and vibrating displacement in an in-phase mode vibration and an out of phase one, and (ii) the fluid-elastic vibration is due to the wake switch phenomenon for three rows circular cylinder bundles.

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We describe the unsteady flow around two-dimensional circular cylinder row supported by the leaf spring in the fluid-elastic vibration. The experiment was carried out in a circuit-type wind tunnel having a 200mm×200mm working section of 2000mm length at the Reynolds number Re of 8820. Two-dimensional circular cylinders with diameter D=20mm were aligned at regular spaces S in a single row normal to the main stream. The spacing ratio between two adjoining circular cylinders was constant as S/D=1.5 for the unsteady flow measurement. The time-mean velocity was measured by use of a laser Doppler velocimeter. The unsteady flow pattern around an oscillating cylinder was observed by the flow visualization in a water channel. Consequently, it was found that the occurrence of the fluid-elastic vibration is caused by the phenomenon of jet-switch for the circular cylinder row.

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Velocities of particles composing a plug front end have been measured at cross-sectional grids in a pipeline by means of Laser Doppler Velocimeter (LDV) to discuss the movement patterns of the particles. As a result, the velocities at the upper part of the plug front end are higher than those at the lower part. The velocities of the upper particles are higher than the plug movement velocity. These results indicate that the particles composing plug at the front end are discharged toward the front air phase. Moreover, according to the particles movement observations, the particles on the central stationary layer near pipe wall move up to the top part of the plug. The discharged particles are originally lied on the parts. Previous researchers observed the plug particles and calculated the particles velocity in a plug by means of dynamic numerical simulation. Our results qualitatively agree with the simulation results.

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To elucidate fascinating nonlinear phenomena of waves on a film in detail, spatial temporal knowledge of the interfacial waves is essential. This paper presents a new method for measuring waves on a film flowing down a vertical tube inner wall using a laser focus displacement meter. The purposes of the study were to clarify the effectiveness of the new method for obtaining detailed information of film thickness or wave characteristics and to investigate the effect of entry length down from the film entrance on the phenomena. With this method, accurate measurements of film thickness in real time with sensitivity of 0.2 microns and 1 kilohertz were achieved. The error caused by the refraction of the laser beam passing through acylic tube, whose outer wall surface was flat, and water was estimated. As the entry length increased, the ripple on the flowing film grew to a solitary wave of about 0.5mm in height then the wave became a two-wave system. In the entry region, the wave amplitude decreased as the flow rate increased in the same manner as that in a film flowing down a plate wall.

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In this study, a method for two dimensional temperature measurement based on O₂-LIPF (laser-induced predissociative fluorescence) using a broad band ArF excimer laser is proposed. In this method, temperature is measured by use of temperature dependence of ratios between fluorescence intensities integrated in two spectral region including peaks. To reduce the measurement time and improve the measurement accuracy, we develop a stereo-viewer which can put two images passed through two different filters on a picture frame. This method is applied to heated air jet, and radial temperature profile at x/D=6 (x : distance from nozzle ; D : nozzle diameter) is compared with that obtained with a thermocouple. Two-dimensional temperature image of the jet is also measured successfully.

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An experimental investigation aimed at controlling the separated-and-reattaching flows over either a backward-facing step or a cavity is carried out. Thin film actuators, attached to the step surface at the edge, are used for the control. Experimental results show that this system is capable of controlling the separation flow of a backward-facing step when the freestream velocity is under 15 m/s. The phase of the separation can be altered in the spanwise direction. The effect of the control is preserved past the reattachment point. However, the systematic pattern of velocity fluctuation cannot be maintained when the freestream velocity is higher. For the flow over a cavity, the flow is controllable when the freestream velocity is low. However, at a high freestream velocity (20 m/s), the uniform phase mode becomes dominant and the flow becomes difficult to control.

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The magnetic flow control characteristics of magnetic fluid two-phase slug flow in a vertical pipe was examined from measured void fractions and pressure drops together with the two-fluid model. The axial pressure distribution was primarily dominated by magnetic pressure rise and drop, and acceleration loss both of which depended on the axial distribution of void fraction. As the interaction between gas and liquid flows, the virtual mass force was remarkably large near the position of maximum magnetic field strength. The drag force acted on gas phase greatly due to large slip ratio which was caused by the magnetic force.

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The aim of this study is to elucidate experimentally the effect of chemical reaction on the diffusion process in a turbulent liquid jet. The second-order and irreversible reaction (R+B→S) of which kinetics is well known was used here. The instantaneous concentrations of two species (R and S) were measured simultaneously by the light absorption spectrometric method, then the conserved scalar was determined by using the conserved scalar theory. To ascertain the validity of the concentration measuring system, a comparison between statistics of conserved scalar and those of non-reactive scalar was made. It was found that the radial and axial distributions of the statistics of conserved scalar show good agreements with those of non-reactive scalar and past other researcher's data. So, it is concluded that reactive scalars can be measured accurately by the present measuring system of multiple species.

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The aim of this study is to elucidate experimentally the effect of chemical reaction on the diffusion process in a turbulent liquid jet. The chemical reaction in this study is second-order and irreversible reaction, R+B→S, of which kinetics is well known. The instantaneous concentrations of two species (R and S) were measured simultaneously by light absorption spectrometric method, and concentration of species B was determined by the mass conservation equation. A comparison between statistics of reactive concentration field and those of frozen and equilibrium limit deduced from the conserved scalar theory was made. It was found that the mean concentration of reactive species is closer to the frozen limit because of the relatively small Damkohler number. The r.m.s. value of the jet reactant R becomes smaller than that of frozen limit by the effect of chemical reaction, whereas that of the ambient reactant B becomes larger in the region of measurement.

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An analytical investigation for radiation phenomena in the shock induced boundary layer along a flat plate is presented.The Navier-Stokes equations coupled with thermochemical nonequilibrium are numerically solved for a strong shock wave propagating in air between parallel plates. The two temperature model is used as thermal nonequilibrium model and the plates are assumed as adiabatic and noncatalytic. The shock Mach number is 30.0 in the initial pressure 13.3 Pa. A velocity slip condition is applied on the plate surface. The radiation is evaluated by a numerical code based on the NEQAIR. The result shows the existence of intence nonequilibrium radiation in the shock induced boundary layer.

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In order to improve the efficiency of a canned motor, it is important to reduce the fluid friction drag of the rotor. In this study, co-axial cylinders which were the model of a canned motor were examined. To reduce the fluid friction drag of the rotor, six kinds of rotor with riblet were used. The riblet height of rotors was from 0.05 to 0.4 mm and the riblet pitch of rotors was from 0.1 to 0.8 mm. The fluid friction drag of rotors was determined by the measured torque of rotors. The reduced ratio of the rotors with riblet to the rotor with smooth in the fluid friction drag was obtained in the range from 500 to 5000 of the gap Reynolds number Re_w. The reduced ratio was also discussed for the rotor with triangular riblets like a screw.

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Tribological characteristics between the piston and cylinder wall are very important for piston pumps and motors, especially for swash plate-type, to realize high efficiency and reliability. In this paper the solid contacting forces and power losses under medium and high speed operations are theoretically analyzed. Then, three calculating methods in relation to cavitation of the fluid film are discussed. The effects of mass of the pistons, difference between the male and female pistons, and the rotating cylinder block-types and rotating swash plate-types are also given.

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Transosic characteristics of three similar turbine cascades (designed for same condition, but with slightly different curvature of blade suction surface after throat) were tested by high-speed cascade wind tunnel. Experimental data showed small difference of curvature of blade suction surface after throat affected loss coefficient in transonic region. Only one cascade with straight suction surface after throat showed additional loss in the region of outlet Mach number near unity. Numerical simulation using Compressible Navier-Stokes TVD scheme was applied to these cascades. Computed loss characteristics were very similar to experimental results. The computed Mach number distribution showed the correlation between the difference of loss coefficient and the difference of the strength of shock wave from the wake of cascades. There was also difference of boundary layer growth on the suction surface after throat in two types of cascades, one had additional loss and others didn't.

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A foraging bee is one of the most actively working insects. The bee's abdomen is well equipped with muscles for both contraction and extension. Besides, the bee has well developed air sacs not only in the abdomen but in the thorax. From view of the respiratory organ, a worker bee is a good example of a high oxygen consumed living thing. Here the gas transport system was investigated by measuring the oxygen partial pressure, Po₂, in the bumble bee thorax. The measurement was made by directly inserting a needle electrode into a wing muscle. Results show the Po₂ in a resting bee fluctuates with typically 70-120 sec interval. At phase of Po₂ increase, the bee moved an abdomen repeatedly to ventilate air inside the body. The discontinuous ventilation should be beneficial for reducing water/heat loss but not necessary for oxygen supply at resting condition, therefore thermal effect to the ventilation pattern was examined, by which coiling a body changes the respiration from shallow to deep. In most case of the flight experiment, the bee started flying after elevating Po₂ in the muscle by the abdominal movement, in that Po₂ in the muscle decreased at onset of the flight. However, Po₂ during flight gradually approaches the certain Po₂ level which is much higher than the lowest value in the discontinuous ventilation. When the flight started without the preflight movement and Po₂ was low in the muscle, Po₂ inversely increased by the flight. To increase the oxygen supply during flight, the bee continuously contracted and extended the abdomen. The bee effectively uses the well equipped abdomen to take an advantage of the convective transport.

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A method is developed to solve 3-dimensional inverse load problem on radiation heat trasfer. In the present study, the heat flux and temperature distributions of many heater elements arranged along inside a rectangular furnace walls are shown to be estimated from the boundary conditions assigned to the heated objects in the furnace by using the newly developed solution method using singular value decomposition (SVD) technique. The statistical error contained in READ values that represent the radiative heat exchange between elements in the system and are calculated by using the Monte Carlo method are corrected by using smoothing technique. This reduces the scatter of the results contained in the inverse calculation and also reduces the computation time remarkably.

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A new equation of state for aqueous ethanol mixtures is proposed in the temperature range from 270 K to 420 K at pressures up to 200 MPa. The equation is expressed in a form of excess molar Gibbs free energy as a function of temperature, pressure and mole fraction of ethanol. The equation has been formulated based on the experimental data of excess molar volume measured by the present authors. Comparisons with the experimental data are reported in detail. Behaviors of excess molar Gibbs free energy and excess molar enthalpy as a function of mole fraction of ethanol are discussed in a wide range of temperatures and pressures.

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A numerical analysis based on the finite difference method was made on a three-dimensional separated and reattached flow around a surface-mounted hexahedron in a channel with two parallel walls, and the heat transfer characteristics therein were also analyzed. Reynolds numbers treated are 100∼1000 and Prandtl number 0.7, respectively. It is clarified from the numerical results that the flow around the hexahedron is very complicated, forming a horseshoe vortex around it, and also producing the separation and reattachment of flow on and downstream of it. The heat transfer characteristics over the hexahedron greatly depend on the flow behavior. These flow and heat transfer features vary with the Reynolds number.

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The effects of inner rotating plate with horizontal axis on the heat transfer in a differentially heated vertical enclosure were investigated experimentally. The aspect ratio of the enclosure height/width was 1 throughout the experiments. An acrylic plate with small thermal conductivity was installed horizontally at the center of the square enclosure, and was rotated at various speeds for normal and reverse rotations by using the motor attached outside of the enclosure. Purified water was used for the working fluid. The flow pattern was sketched by a visualization experiment using aluminum powder. The heat transfer results were also compared with those for previous paper of rotating cylinder. It is clarified here that the heat transfer rate of the enclosure depends largely on the parameter Gr_w/Re²_w, and is characterized by three regions. The heat transfer rate of enclosure with rotating plate is fairly larger than that of rotating cylinder in the forced convection region. The rotating plate used here will be useful for regulation of wide-ranging heat transfer.

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Heat transfer in a rotating rectangular rib-roughened duct was numerically simulated by using the second order finite difference method. In order to investigate the effect of the Coriolis force and the cross-sectional aspect ratio on the turbulence, the large eddy simulation was adopted with a dynamic subgrid scale model. The rotation number (0 and 1.0) and the cross-sectional aspect ratio (1.0, 2.0, 4.0) were varied while the turbulent Reynolds number was set to be a constant value, 350. The present results clearly showed the locally high heat transfer coefficient at two location : in front of the rib on the rib-roughened walls and around the rib on the side walls. The effect of rotation was seen in the increased and decreased heat transfer on pressure and suction surfaces, respectively. The heat transfer enhancement caused by the rotation was larger for the higher aspect ratio case.

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This paper deals with theoretical analysis of turbulent film condensation on a vertical surface. To solve the governing equations-continuity equation, momuntum equation and energy equation, a new model for eddy diffusivity on turbulent film condensation is assumed. The dimensionless variables are introduced to nondimensionalize the governing equations. The dimensionless governing equations are numerically solved by using finite-difference method. Using the numerical results, the correlations to predict local Nusselt number, average Nusselt number, local condensation number and average condensation number are obtained for Pr_L=0.01∼100. The correlations for local and average condensation number are in agreement with experimental data.

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This study was researched by a numerical analysis and experiment, on a natural convection heat transfer in a horizontal cylindrical eccentric annuli, which heated outer tube and cooled inner tube. The inner tube shifted to vertical upper side, slant upper side 45 degrees, horizontal side, slant lower side 45 degrees and vertical lower side, respectively. The numerical analysis was performed by changing the shift direction, eccentricity 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 on the total heat transfer were affected by shift direction and eccentricity.

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The longitudinal vortices were artificially generated by a single winglet vortex generator in a pipe. The longitudinal vortex enhances the heat transfer compared to other vortices produced by protrusions, because this longitudinal vortex does not decay until relatively further downstream. The purpose of this study is to know the informations about the flow motion of longitudinal vortex and the influence of vortices on heat transfer enhancement. The flow pattern was visualized by means of both fluorescein and rhodamine B, as a tracer of the water flow in a water table. The main vortex was spirally moved along the circumference and the behavior of other vortices was observed. Streamwise and circumferential heat transfer coefficients on the wall, wall static pressures, and velocity distribution in the overall cross section were also measured for air flow in the range of Reynolds number from 18 800 to 62 400. The distributions of streamwise heat transfer coefficients had a periodic pattern, and the peaks in the distribution moved circumferentially due to the spiral motion of the main vortex. Relation of the iso-velocity distribution and the wall static pressure to the heat transfer characteristics was shown. Moreover, the thermal performance was calculated under the condition of fixed pumping power, and it was found that the performance ratio is almost larger than unity.

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The effect of liquid subcooling on the convective film boiling heat transfer from a finite-size horizontal downward-facing surface was investigated both theoretically and experimentally. The approximate solution with some simplified assumptions was obtained by solving the two-phase boundary layer equations including the energy equation for the liquid boundary layer. The average Nusselt number, Nu_co, derived from the solution may be expressed in a simple form with the parameters of Grashof number, density ratio, (density-viscosity) ratio, liquid Prandtl number, dimensionless degree of wall superheating and dimensionless degree of liquid subcooling. The theoretical results were compared in terms of a ratio of the average Nusselt number for the case of subcooled liquid to that for the case of the saturated liquid, Nu_co/Nu_{co, sat}, with the experimental data obtained by Nishio et al. under the steady-state condition and those obtained by the present authors using a quenching methed. For the case of subcooled liquids, a correlation equation of heat transfer was proposed to effectively correlate the experimental data obtained under both quenching and steady-state conditions within ±15 percent.

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A linear stability analysis of vapor film in forced-convection film boiling on a horizontal cylinder is presented that considers the effects of liquid inertia, viscosity and compressibility of vapor, and periodic heat conduction. The theoretical prediction of the critical vaper film thickness compared well with the measured mean vapor film thickness at the minimum-heat-flux point that was obtained from the rapid quenching experiments of thin horizontal wires in water and ethanol. However, while the theoretical prediction was about 20% higher than the experiment for water, the former was about 15% lower than the latter for ethanol. Discussion was given to the cause of this difference between the water and ethanol results.

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Heat transfer from column wall to liquid-fluidized beds was investigated experimentally. The diameter ratio of particle to column was changed from 0.089 up to 0.332, using 11 sizes of particles and two sizes of columns. It was found from the experiment, that the critical diameter ratio of particle to column is 0.2, below this value a good fluidizing condition is maintained for any flow rate and heat transfer coefficient changes smoothly from the minimum fluidization to the liquid singlephase flow. Based on the experimental data, a correlation was derived to predict heat transfer coefficient for the case affected by column wall.

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This paper describes conduction model based numerical simulation technique for portable computers. A numerical analysis was carried out on the basis of thermal conduction treatment for the whole domain of a subnotebook computer which has a cooling fan. In this work, thermal conduction analysis was employed to estimate the temperature distribution of a computer. To treat the airflow caused by the cooling fan, a lump model was used in addition to the thermal conduction model. The numerical model includes silicon chips, LSI packages, printed wiring boards, enclosure, etc., and excludes the liquid crystal display portion. Temperature rise of LSI packages obtained by the numerical analysis showed a good agreement with measured values, and this indicates the effectiveness of the present analysis method for the design of portable computers.

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This paper describes the outline of thermal design technology used for MITSUBISHI ultra-slim notebook Personal Computer "Pedion". As of September 1997, "Pedion" is the world's thinnest at 18 mm thick among A4-size notebook computers. We have developed innovative thermal solutions for ultra-slim Notebook Pc where only natural convection cooling can be used for heat rejection. The first solution is cooling system for CPU by using the bottom chassis (Mg die-cast) as a heat spreader combining with A1 heat transfer plate. And the size and the thickness of A1 plates were optimized by thermal analysis using Finite Volume Method. As the second solution, a new coating which can reduce touching warmth of Mg die-cast enclosure have developed and already been reached the stage of practical use.

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An experimental study has been made to elucidate the characteristics of critical heat flux (CHF) in a concentric tube thermosyphon. The experiment has been done by using saturated water, ethanol and R 113 over the experimental range of configuration : inner diameter of heated tube D_i=9-17 mm, outer diameter of inner tube d_o=3-15 mm and heated tube length L=100-1 000 mm. The experiment shows that the CHF is enhanced with an increase in the inner tube diameter, and then the CHF is reversely decreased beyond a certain diameter of inner tube for each heated tube diameter. The maximum CHF is about two or eight times as large as that without inner tube depending on the condition of the inner and outer tubes. For larger inner tube, the characteristic of CHF is similar to that of natural convective boiling in a vertical annular tube.

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In this paper, the boiling in single and layered packed beds filled with Freon-113 has been investigated experimentally and theoretically. Boiling phenomenon in packed bed under the capillary action was characterized by a formation of two-phase region composed of liquid and vapor phases. In layered packed bed composed of different particle beds, the liquid content becomes discontinuous at the interface because of the difference of the liquid characteristics between two layers. It was found that the dryout heat flux strongly depends on the structure of layered packed bed. The predicted results for the dryout heat flux were compared with the experimental results using a packed bed composed of glass beads.

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The characteristics of a heat exchanger composed of plate and tube operating with melting of piled and falling snow have been investigated theoretically and experimentally. In case of the melting of falling snow, the perfect melting condition and the melting efficiency were related to dimensionless parameters for the heat exchanger and the surrounding conditions. The calculated results for the perfect melting condition and the melting efficiency were in agreement with the results obtained from the field experiments. In case of the melting of piled snow, a quasi-state model of two dimensional snow melting was presented. The melting efficiency becomes higher with a higher inlet brine temperature for the melting of subcooled snow. The melting efficiency of piled snow is higher than that of the falling snow, because the piled snow remaining on the plate acts as an insulator during melting.

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Since phytoplankton are principal components of lake pollution, we are developing a purification system using a SMS (superconducting magnetic separator) for removing phytoplankton rapidly and energy efficiently. This system includes a new separator called as CSMS (continuous SMS). It has a twin-type superconducting magnet, a reciprocating main filter and a rotating sub-filter. The room-temperature-bore diameter of an experimental separator with this structure is 310 mm. The central magnetic field in the main filter is 1.0 T and that in the sub-filter is 0.6 T. And the lowest temperature of the superconducting magnet is 4.1K. This temperature does not depend on supply current. This system achieved a removal ratio of more than 93% of chlorophyll-a at a treatment speed of 400m³/day. This result shows that CSMS is very useful for separating systems.

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This paper aims to clarify the cooling and freezing processes of water around two horizontal tubes placed in vertical arrangement, as the basic research for an ice-on-coil type of ice thermal storage system. When water is cooled and frozen in this system, natural convection occurs by the difference of local density. This natural convection governs the heat transfer characteristics and much influences the cooling and freezing processes. Especially, the flow pattern of this convection drastically changes on the way of cooling, because water has a maximum density at 4°C. This complex flow pattern was experimentally visualized by the laser measurement techniques, and calculated by the finite difference method with body fitted coordinate system. These experimental flow visualization and calculation were performed with varying the cooling rate. We could acquire some interesting relations among the flow pattern, the heat transfer characteristics, the release of supercooling and the growth of ice.

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Effect of fluid type on wake oscillation and surface value in suppression of the Karman vortex street due to positive buoyancy from a heated circular cylinder submerged in an upward mainstream is elucidated by numerical calculation of the Navier-Stokes equations with buoyant term and the energy equation for mercury, air and water flow. Numerical results are validated. The Strouhal number decreases abruptly at the critical Richardson number Ri_c, which can be regarded as the exact boundary between the regions of the transformed vortex street and the plume flow. The largest Ri_c is for water, the smallest is for air. The mean Nusselt number of water flow decreases abruptly at Ri_c. This is because that the local Nusselt number near the rear stagnant point decreases at Ri_c due to a formation of a twin vortex.

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Polymer ablation by a UV laser irradiation was experimentally investigated to understand the influence of irradiation parameters on the change of polymer. Polyethylene terephthalate sheets of 350μm in thickness were irradiated at 10 Hz with the 193 nm ArF excimer laser pulses of a full width at half maximum of 26 nsec. The polyethylene terephthalate has an extremely high absorption coefficient, 2.3×10⁷l/m, at 193 nm. The number of delivered pulses, fluence, and irradiation angle were changed and, particularly, attention was given to the influence of irradiation angle, which has not been yet systematically investigated so far. The ablation mass and depth as macroscopic characteristics were measured. The morphological microstructure of the surface after irradiation was observed with a scanning electron microscope and an optical microscope as well, and the characteristic length of the microstructure was quantitatively made clear.

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Experiments under microgravity condition were performed to investigate the surface reaction model. A spherical platinum of 1.5 mm in diameter was used and the surface temperature was measured by thermocouple. The mole fraction of nitrogen of the mixture was 0.91. As the effect of natural convection can be neglected under microgravity condition, three based partial differential equations, which govern mass, energy and species concentrations, are stated in one-dimensional polar coordinates. Axial symmetry, zero azimuthal velocity, and no gradient along the axis are assumed. The microgravity condition was obtained by parabolic flight. The equivalence ratio of the mixture was varied. If the equivalence ratio is larger than 0.15, numerical results fitted experimental results successfully. However, if the equivalence ratio is less than 0.15, numerical results did not fitted experimental results well.

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A direct numerical simulation of two-dimensional fuel jet flames developed in a co-flowing air stream was made considering rather complex finite chemistry in order to clarify the role of elementary reactions on flame structure and its unsteady behavior. The governing equations were discretized and numerically integrated by using a finite volume method. The temperature dependence of thermodynamical properties was taken into account and the transport properties were calculated according to the simplified transport model proposed by Smooke et al. Chemical reactions were described by the Smooke's skeletal methane-air reaction mechanism. It was found that large-scale fluctuations were produced in the downstream where a decrease in temperature occurred at some instants leading to local extinction. Comparing with the results of counterflow laminar diffusion flame, it was also found that the hypothesis of laminar flamelet model can be accepted even for the case of the unsteady jet flame with the local extinction. Furthermore, a better understanding of extinction mechanism was obtained : In the turbulent region of the flame, fuel is converted by the large-scale vortices into the reaction zone at high supply rates inducing CH₃, CH₃O, CH₂O and HCO production. At some instant, the increase of mixing rates will results in a decrease of temperature causing the consumption of available active radicals due to the activity of some exothermic reactions, and the slow-down of the reactions producing new OH, O, H radicals. The radical pool is no longer available for chain reactions to proceed, resulting in an extinction.

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Numerical computations are made of axisymmetric laminar hydrogen jet diffusion flames, focusing on the unsteady behavior under microgravity and the effects of magnetic field. In the computations, multicomponent diffusion and detailed chemical kinetics are considered. In the condition under microgravity without magnetic field, it is revealed that combustion products remain around the diffusion flame because of the lack of natural convection, and that the amount of O₂ diffusing to the flame region becomes retarded. That is the reason why the heat release rate in the diffusion flame decreases with the lapse of time. When a gradient magnetic field is added, convection is induced around the diffusion flame by the magnetic field which induces magnetic buoyancy force due to the inhomogeneity of magnetic susceptibility. The flow configuration formed by the magnetic force under microgravity is similar to that under the normal gravity without the magnetic force. The positive gradient of the magnetic field induces the reverse convection which forms the depressed and flattened flame in the normal gravity field. The negative gradient of the magnetic field accelerates the flow together with the normal gravity.

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We have tried to extend new effective temperature scale to evaluate thermal comfort in an air conditioned vehicle compartment which has uneven and unsteady environment. The equivalent temperature is calculated from measured thermal conditions and physiologic values. Physiologic values are calculated by a simple model of human thermal system, in which human body is divided into 16 components and each component consists of core and skin. The skin temperature calculated by the model and thermal vote expected from the equivalent temperature are in agreement with the experiment.

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Recently, an electrically-controlled throttle valve is gradually being popularized with the appearance of lean-burn gasoline engines. The system used this device, has the freedom to allow different behaviors between the throttle valve and the accelration pedal, and is called "Drive By Wire (DBW)" system. Therefore, DBW system is able to control optionally the dynamic characteristic of the automobile within its hardware limitations. In other words, it is possible to tune up the sensitivity of the acceleration pedal optionally. This paper describes compensation algorithm against changing the automobile weight and road gradient, while the optionally tuning up is carrying on. Principle of the compensation is conducted by comparing the behavior of the reference model which is running at normal load condition, with that of a real automobile which is running at changed load condition. Experiments was carried out using an engine load simulator, and showed good results of the compensation.

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This paper proposes a method to estimate the stable combustion limit in a conventional engine because of its increased importance, and this method is applied to the study of combustion stability in a two-stroke cycle engine fueled with methanol. Fluctuating ratios of indicated mean effective pressure and maximum pressure in the cylinder on a two-stroke cycle engine are defined and applied to estimate the combustion stability. The stable combustion limit can be estimated from maximum pressure versus crank angle diagram, since on the diagram, distribution area of maximum pressure included no misfiring cycles are different from that included misfiring cycles. In case of the stable combustion, fluctuating ratio of maximum pressure is within 10%. This value corresponds to the indicated mean effective pressure fluctuating ratio of about 5%. In consequence of the above, it is shown that the range of excess air ratio for the stable combustion using methanol fuel increases toward lean side in comparison with gasoline. Also at the same excess air ratio, the lower limit of delivery ratio and the upper limit of engine speed for the stable combustion can be improved by using methanol fuel.

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A six-stroke diesel engine which was proposed by authors had second compression and second combustion strokes which were added on a four-stroke diesel engine. Numerical prediction and experiments on six-stroke engine which were carried out previously, showed that a six-stroke diesel engine could reduce NO concentration and shorter ignition delay could be attained in second combustion. Using various fuels on second combustion, it might be possible to improve more the emission characteristics. In this report, Methanol was used in the second combustion to improve the six-stroke engine performance. As the result, NO concentration in the exhaust gas decreased with delaying of the injection timing at second combustion and increased with an increase of the heat allocation ratio of second combustion stroke when the injection timing at first combustion stroke was fixed. Smoke wasn't exhausted at all when Methanol was put into the second combustion stroke. NO concentrations were affected by the heat allocation ratio and related with gas temperature. It was confirmed that the NO concentration of the Diesel fuel-Methanol engine become lower compared with that of the Diesel fuel engine.

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