An air bubble separation and removal system is necessary, especially in space, for fluid processing devices. We have developed a new bubble separator for microgravity environments in which bubbles are pushed through a hydrophobic membrane by an electromagnetic body force. Our ground experiments using the separator model confirmed that air bubbles can be removed efficiently by an electromagnetic force. Subsequently, we carried out microgravity tests of 10-second duration in a drop shaft. In these tests, the effect of the electromagnetic force on bubble behavior was visually investigated and successfully recognized.

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The dynamics of a laser-induced bubble in liquid nitrogen is studied experimentally. The motion of an almost spherical bubble, formed under appropriate control of optical conditions, is visualized by high-speed photography. Low subcooled liquid nitrogen at 78.0 K is used ; the resulting high vapor pressure inside a bubble causes motion different from that in water at normal temperatures. Pressure is applied to liquid nitrogen to increase the degree of subcooling. An induced bubble grows similarly to a Rayleigh bubble under the effect of liquid inertia. The high vapor pressure, however, retards the collapse from the Rayleigh solution, and makes the bubble surface rough by Taylor instability coupled with themodynamical effect. Estimation of the cavitation parameter in experiments of liquid nitrogen and water enables us to understand the transition from the motion being heat transfer dominant to that being liquid inertia dominant.

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The diffusion velocity method for the vortex model was applied to simulations of unsteady flows about a circular cylinder. Our method successfully simulates flow patterns which depend on the Reynolds number, such as symmetrical flow patterns at Re=0.1 and 1, creation of a vortex pair behind the circular cylinder at Re=1 and of a Karman vortex street at Re=1200, and a separation point which goes backward at Re=10⁶. The drag coefficients obtained by our method are in good agreement with experimental data.

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Irregularity of vortex shedding from a circular cylinder is studied experimentally. The study is based on a spectral analysis of local rms value of velocity fluctuation behind the circular cylinder. Spectral analysis of circulation of vortices obtained by both PIV and image processing of the streak line visualized by hydrogen bubbles extending from the location near the separation point of shear layer is made in order to investigate the relationship between velocity fluctuations and circulation fluctuations. From this study, long time scale periodic fluctuation, approximately 20 times the vortex shedding periodicity, is clarified. Also a good correlation between the time variation of the local rms value and that of the circulation was obtained.

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In a heated pipe, free convection is caused by the buoyancy forces of laminar flow. However, it was shown in a previous paper that free convection in a steady flow occurs when the temperature differences between air in a room and water in an unheated pipe are large. Under such experimental conditions in the case of pulsating flow, cross-sectional distributions of axial velocities are measured for water over a frequency range of 0.313 Hz to 2.1 Hz by means of a hot-wire anemometer in the present investigation. The cross-sectional distributions of instantaneous axial velocities are not the same as the Poiseullian velocity distribution. Furthermore, both the magnitude and the phase angle distributions of oscillating axial velocities are also presented.

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In detergent engineering and polymer processing, it is important to study the force exerted on an obstacle placed near a wall. In the present study, we numerically analyze the flow of viscoelastic fluids past a minute cylinder which is set at or near an inside wall of a two-dimensional channel. The upper convected Maxwell model and the finite-element method are used as the constitutive equation and the numerical method, respectively. Drag and lift of the cylinder are calculated for low Reynolds numbers (Re) and various Weissenberg numbers (Wi) of positive and negative values. Drag coefficient (C_D) slightly changes with Wi. Lift coefficient (C_L) monotonously decreases with increasing Wi irrespective of the sign of Wi. C_L is greatly changed with Wi and is more sensitive to the elasticity of the fluid than C_D. C_D and C_L decrease as the cylinder is separated from the wall.

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A compressible viscous two-phase flow of SF₆ and Ar with condensation in a supersonic nozzle is calculated. The flow field is solved with a 3rd-order MUSCL type TVD scheme. The calculation of condensate mass fraction and nucleation rate was based on Becker-Doring's condensation theory. The development of velocity and thermal boundary layer is discussed in detail from the point of view of the interaction between the boundary layer and condensation. Distribution of pressure along the nozzle axis obtained from the numerical calculation is in good accordance with the experimental one in the case of the stagnation pressure region from 20 kPa to 100 kPa. It was found from the result that the condensation takes place in a limited region under relatively high stagnation pressure, which spreads downstream as the stagnation pressure decreases. The temperature and velocity gradients in the boundary layer increase due to the latent heat release of condensation. Consequently, development of the velocity and thermal boundary layers was suppressed by the condensation.

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Hydrous electrorheological (ER) fluid was filled in between two coaxial cylinders : the outer cylinder can rotate on its axis and the inner stationary one is connected to a torquemeter. Upon application of an electric field and rotation, measurements of velocity distributions of ER fluid in the annular region were taken by a laser velocimeter and those of shear stress exerted on the inner cylinder surface were taken by the torquemeter. When the rotational speed was very low, the flow was observed directly. Since high-water-content ER fluid requires high electric current, a counter-plan to reduce the current was also examined. It was found that the ratio of electrical force to viscous force plays an important role in determining the flow pattern of ER fluid and, upon increasing the magnitude of the ratio, the flow pattern varies from couette flow to plug flow. Insulation of the inner cylinder surface with thin polyethylene film could reduce the electric current and the magnitude of the generated shear stress decreased to one-tenth of that without insulation film.

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Direct numerical simulation of three-dimensional compressible homogeneous isotropic turbulence was conducted by a spectral method to verify SGS stress models of large eddy simulation. A linear combination model and dynamic SGS model were compared with the exact SGS stress evaluated from the DNS data. From this study, the following conclusions are obtained. (1)Correlation coefficients between the exact cross-term and the modeled ones predicted by the linear combination model and the model following the original scale-similarity hypothesis show values as high as 90%. (2) The SGS-Reynolds stress predicted by the assumption of scale similarity shows the highest correlation, whereas the correlation between the exact one and the linear combination model is low. (3) The dynamic SGS model and the exact stress show low correlation which depends on the kind of filter and the averaging volume.

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A fully developed turbulent flow in a rectangular duct with rib-roughened short-side walls has been measured by hot-wire anemometers. Detailed results obtained in two cross sections, the midpoint between two ribs and on top of a rib, are presented for quantities such as coefficient of flow resistance, local wall shear stress, primary and secondary flow velocities, turbulence kinetic energy, and turbulent shear stresses. It has been found that only one large longitudinal vortex appears in a quadrant cross section of the present rough duct, which causes strong distortions in the contours of the primary flow velocity. The turbulent shear stress that is normal to the rough wall becomes much larger than that of the smooth duct, but that parallel to the rough wall shows almost the same distribution as the smooth duct, qualitatively and quantitatively. The distribution of the secondary flow vectors changes depending on the distance between the rib and the measuring cross section. However, the distributions of the turbulent stresses are independent of the streamwise location of the measuring cross section.

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This paper presents an experimental investigation of the turbulent boundary layer flow along rows of streamwise square ribs on a plane surface for various spacings of rows. The spacing between the centers of two adjoining square ribs was varied at S/D=2, 3, 4, 5, 7 and ∞, i.e., a single square rib. The time-mean velocity was measured by the Pitot and static pressure tubes. The turbulence intensities and auto-correlation were obtained using the data processing system and the F.F.T. analyzer connected to a hot wire anemometer. The Velocity vectors of secondary flow were measured by LDV. As a main result, the secondary flow becomes offset as the spacing between two ribs becomes small, since the directions of the secondary flow near the edges between the marked rib and the adjoining rib are opposite

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Conventional turbulence models have a single time scale of turbulence which is determined by turbulent energy k and its dissipation rate ε (i.e., k/ε). This fact implicitly assumes that the shape of the turbulent energy spectrum is universal. Therefore, they cannot predict the flows that are influenced by a lot of time scales of turbulence. In simulating such flows it is neccessary to introduce some information about scales of turbulence. In order to overcome this problem, multiple-time-scale turbulence models have been proposed. However, most of them are based on the k-ε model and the eddy viscosity hypothesis restricts the universality. In the present study the basic form of a multiple-time-scale Reynolds stress model was proposed, based on the transport equation for a two-point velocity correlation. In addition, this model was applied to a grid turbulent flow. By introducing some restrictions and assumptions, the model coefficients were determined analytically and numerically. It was shown that the model is satisfactory.

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Conventional turbulence models have a single time scale of turbulence. Therefore, they cannot predict the flows that are influenced by many time scales of turbulence. In simulating such flows it is neccessary to introduce some information about the scales of turbulence. In order to overcome this problem, I proposed a multiple-time-scale Reynolds model and the model coefficients were deter-mined for a grid turbulent flow. In this study, the model was applied to a variety of grid turbulent flows to verify the model performance. The numerical results for turbulent energy, Reynolds stresses and second and third invariants were compared with the experimental data. The temporal change of large and small-scale conponents for Reynolds stresses and energy transport rates were also verified. It was found that the model can satisfactorily predict a wide range of grid turbulent flows. In addition, it was verified that the method used in setting initial conditions is reasonable.

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The performance of four relaxation methods for the compressible Euler equations is examined. The Euler equations are cast into the Euler implicit delta form. Four spatial discretization methods, the central difference (CD), total variation diminishing of Yee and Harten (TVD), flux difference splitting of Roe (FDS) and flux vector splitting of Van Leer (FVS), are applied to the spatial derivatives of the right-hand side. Flux splitting Gauss Seidel (FSGS), approximate flux splitting Gauss Seidel (AFSGS-I and AFSGS-II), and lower-upper symmetric Gauss Seidel (LU-SGS) methods are tested for the solution of the implicit equations. Numerical results are presented for a two-dimensional flow about a circular arc bump. Compatibility and efficiency of the numerical solutions are analyzed for all combinations between relaxation methods and spatial discretization methods. Steady-state solutions are independent of the relaxation methods. The AFSGS-II method gives the best efficiency for all spatial discretization methods.

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The laminar separated flow through a two-dimensional symmetric and asymmetric sudden-expansion channel has been investigated numerically. As a computational model of the expansion channel, the two-dimensional channel with backward-facing steps on both upper and lower walls was considered, and steps of both upper and lower walls were placed at different locations with distance L_D in the flow direction for step asymmetric expansion channel. A stream function-vorticity formulation was used and solved by the finite difference method using the pseudo-unsteady technique. The calculations were performed for the range of low Reynolds number Re≤160, and for the cases of six different distances L_D in the region of O≤L_D≤1. In this work, particular attention was paid to the effect of distance L_D on the behavior of separated recirculating flow. The results showed that the recirculating flow changed with variations of both the distance L_D and Reynolds number Re.

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In the fundamental experiments of a classifier with an injection port at the collecting mouth, the diameters of muddy deposits (relatively small particles) are kept constant and the diameters of sand grains (relatively large particles) are varied. It was found from the experiment using a spherical glass bead as a particle, that as the diameter of larger beads increases, the classification finishes within a shorter time but the final classified volume becomes smaller. On the contrary, in the case of smaller bead diameter, it takes a long time to classify but the final classified volume becomes larger. Furthermore, from these results the gravitational force acting upon the beads and the apparent viscosity affects the classified volume and the classifying time. The relations between the classified volume and the classifying time become similar and independent with larger bead diameter.

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The usefulness of the so-called e^N-method for predicting the point of transition to turbulence in a radial liquid-film flow is established. The spatial linear stability of the flow was investigated, including the effect of the radial spreading of vortices. The non-homogeneous Orr-Sommerfeld equation was solved numerically. It was found that the calculated result which included the effect of the radial spreading of vortices is more unstable than that neglecting the effect ; the effect increases with decreasing radius. The frequency of the most amplified disturbance, which was estimated from the evolution of disturbances with fixed frequency, was in good agreement with that detected through wall pressure measurement. It was found, from the comparison of the stability theory with experimental results, that the exponent N is about 9 when the transition to turbulence occurs.

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In the two-dimensional convection-diffusion finite-element analysis, various kinds of elements are adopted for practical uses, such as a triangular element and a rectangular element. However, there seems to be no research on the computational error estimation of these various kinds of elements. In this paper, we estimate the numerical error for four different triangular elements and a rectangular element using the error analysis technique. The Galerkin Method (GL) and our previously proposed modified Galerkin Method (MGM) were investigated at the same time. From the error analysis results, we found that MGM offered greater effectiveness than GL and higher accuracy of a rectangular element or a regular triangular element than other triangular elements. Through numerical experiments using these five different elements, we confirmed the general correspondence between the error analysis results and the numerical simulation ones.

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This paper presents an investigation on the configuration of the particles of a magnetic fluid and its magnetization characteristic based on Monte Carlo method. The interparticle interactions caused by the magnetostatic energy, the repulsion energy, the van der Waals energy and the external magnetic field energy are calculated. In the calculation, the distribution of magnetic particles is assumed to be a lognormal distribution estimated from that of a magnetic fluid under the investigation. The calculation results for a magnetization characteristic and for the orientation of magnetic particles of a magnetic fluid are compared with magnetization curves constructed from measured values and with an electron micrograph of magnetic particles, respectively.

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Parallel processing for the DSMC method (direct simulation Monte Carlo method) using a multiprocessor computer is discussed in this paper. Rarefied gas flows through a finite length circular tube, over a flat plate, and in aclosed cavity were simulated by the DSMC method. The performance of parallel processing with a dynamic domain decomposition technique is evaluated in terms of parallel processing efficiencies and acceleration. An estimation method of parallel processing for evaluation of the DSMC method is proposed.

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Fluidelastic vibration of tube bundles is one of the most important factors that needs to be considered in the design of heat exchangers. As this phenomenon is caused by the interaction between flow and structure, hence, very complex and sensitive in nature, the design criteria established through many experiments, based on envelops of the scattered data, have been the only reliable tools for the designers. The authors have developed an accurate CFD technique to solve this moving boundary problem. The fluidelastic vibration problems of Two cylinders and a cylinder row are simulated using the CFD technique. The characteristic phenomena of vortex shedding, coupled Two cylinder motion and fluidelastic instability of a cylinder row are successfully simulated.

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An experimental study was conducted to suppress self-excited oscillation of collapsible tubes, where a steel rod was inserted from the downstream bend into a silicone rubber tube. It was found that rod insertion along the tube center was effective in suppressing self-excited oscillation and that insertion with offset from the center was ineffective in suppression. The principal effect of rod insertion is that the rod contacts the internal surface of the tube and prevents collapse when located at the tube center. This was clearly indicated in the measured tube law. Secondary effects are the release of negative pressure impulse and the reduction of jet velocity at the throat.

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An upward plane jet, impinging on the free surface of water in a rectangular tank, oscillated Without external oscillation force. The occurrence condition and frequency of this oscillation which we called "jet-flutter" depended on the distance from the jet inlet to the free surface and the jet inlet velocity. We performed experiments varying several geometric conditions of the jet : thickness of the jet, height of inlet from tank bottom and the ratio of length of the jet inlet to the tank width. The dependence of occurrence condition and frequency varied widely with the ratio of length of the jet inlet to the tank width. In particular, when the ratio was 1, i.e., the tank was completely divided by the jet, the frequency corresponded to the natural frequency of the water column in a U-tube which had the same depth as the distance from the jet inlet to the free surface.

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Analytical solutions of the wave equation for pressure fields generated by reflection of plane waves from symmetric V-shaped reflectors consisting of two triangles are expressed as three combinations of a function which represents pressure field induced around a wedge or a corner. In order to compare the analytical results of the wave equation with numerical results of gasdynamics, simulations are conducted for reflection of a plane shock wave at the incident shock Mach number of 1.05 from several V-shaped reflectors employing an explicit TVD scheme. Comparisons of pressure fields between the computed and the analytical results show good agreement.

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Three-dimensional swept shock wave/turbulent boundary layer interaction is computed using an explicit numerical algorithm for the compressible Navier-Stokes equations. The flow configuration which is simulated as a flow field in a supersonic air intake consists of a wedge of 15 deg attached normal to the flat plate. The computed results are obtained at freestream Mach numbers of 3.25 and 3.11 using the turbulent eddy viscosity model with and without boundary layer bleed at the interaction region. The computations are executed on a supercomputer NWT at the National Aerospace Laboratory. The results with the boundary layer bleed show generally good agreement with the experimental results of the surface pressure profiles. The prediction also provides important information about the effective arrangement of the bleed region.

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Occurrence of periodic self-rotation of an orbiting scroll in scroll compressors having orbital mechanisms composed of a ball coupling and an eccentric bushing was indicated in our previous paper. This paper investigated successively the self-rotational motion of the orbiting scroll in detail. Complex motion of the orbiting scroll and the eccentric bushing was analyzed theoretically based on equations of motion about them. The motion was also measured experimentally with an optical method by changing operating pressure and magnitude of clearance at the ball coupling of the compressor. As a result, positive and negative self-rotation of the orbiting scroll during one revolution of the compressor was clearly demonstrated and the tendency was supported by the theoretical analysis.

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Refrigeration oil is used for lubrication, sealing and cooling in refrigerant compressors, and mixing of the oil with refrigerant has great influences on compression characteristics in the compressors. In the past there were some studies in which the effect of the oil on the compressor performance was analyzed theoretically, but most of them did not discuss well the propriety of the oil treatment in the analysis. In this study, we developed the mathematical compressor model including the effect of the oil on leakage, heat transfer and flow resistance in vane compressors and examined the influence of the ways of treating the oil on the calculated results. When the model employed a quality of two-phase leakage flow equal to that in the compression chamber and a coefficient of heat transfer reflecting thermophysical properties of the oil and the refrigerant, it showed better agreement with experimental results.

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Refrigeration oil is used for lubrication, sealing and cooling in refrigerant compressors, and mixing of the oil with refrigerant has complicated effects on operating characteristics of the compressor. In this study, we measured operating performance of a vane compressor under various conditions of oil supply, and the experimental results were analyzed in detail using a mathematical compressor model developed in our previous study. With increasing ratio of the oil mixed in the suction refrigerant, volumetric efficiency of the compressor increased at lower rotational speed because of decreased losses of leakage and heat transfer, and it decreased at higher rotational speed due to increased pressure drop in a suction port. On the other hand, indicated efficiency increased slightly with increasing oil rate due to the cooling effect of the oil.

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The purpose of this paper is to investigate how one can control and suppress cascade flutter by means of sound waves. The model considered herein is a three-dimensional linear cascade of flat plates oscillating in a subsonic uniform flow between parallel walls. A sidewall of the model is partially made of actuator surface like a loudspeaker which generates sound waves with the same frequency as that of the blade vibration. The aerodynamic work exerted on a blade due to oscillating motion of the cascade itself and due to the motion of the actuator wall surface are calculated. The required amplitude of the actuator wall surface (i.e., the loudspeaker membrane) to suppress the cascade oscillation is also estimated. Numerical results show that the loudspeaker can work most effectively when the center line of the membrane is located just upstream of the leading edge line of the cascade or when the leading edge line of the membrane is located near the trailing edge line of the cascade. The phase difference between vibrations of the cascade and the actuator surface is also an important parameter.

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Numerical simulation of the velocity and temperature distribution in a finned heat exchanger was performed. The simulation was carried out by taking into account the temperature dependence of physical properties of air. In order to observe a velocity field, visualization experiments on flow through large-scale models of a louvered fin array were conducted using hydrogen-bubble and dye injection techniques. We found a good agreement between the numerical simulation and the flow visualization. We also note that an appreciable difference in the average Nusselt number for a parallel louvered fin has been found between the numerical simulation which includes the temperature dependence of physical properties and the same simulation without temperature dependence.

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To clarify the effect of the inertia moment on the starting and running characteristics of an axisymmetric cross-flow turbine in oscillating flow, experiments are carried out using turbine test equipment in which wavelike up-and-down oscillating flow conditions are simulated. On the other hand, the dynamic characteristics of this turbine are calculated numerically on the basis of experimental data obtained from experiments in the steady one-way flow condition. The experimental results are compared with the numerical ones and fairly good agreement between them is demonstrated. Furthermore, using the nondimensional equation of motion for the rotating system, the effects of the wave height and the inertia moment of turbine on the running characteristics are investigated.

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In the present study, the effect of the secondary helical flow on the variation of wall shear stress using an asymmetrical branch model has been studied experimentally. The experiment has been carried out for a branch model, such as the inferior mesenteric artery from the abdominal aorta, so that the daughter tube branches out from the parent tube at 45 deg with the radius of curvature at the upstream corner of the daughter tube. In the experiment, the velocity profiles and the wall shear stress have been measured by a laser Doppler velocimeter and the electrochemical method, respectively. The results show that the variation of wall shear stress along the proximal wall strongly depends on the geometry of the proximal wall. Furthermore, the variation of wall shear stress results from the secondary helical motion flowing into the daughter tube from the parent tube. The wall shear stress estimated from the velocity profile is compared with that measured by the electrochemical method.

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Axisymmetric buckling and post-buckling behavior of spherical shells subject to external pressure was investigated using the finite-element method to clarify the reason behind the red blood cell shape. In the present calculation, the effects of non-linear strain and initial dimple were taken into consideration. The calculated results show that the shape of the shell changes from spherical to biconcave with the progress of deformation. This result agrees qualitatively with the change of the red blood cell shape due to osmotic pressure and it is suggested that the shape of the red blood cell can be explained by the buckling and post-buckling theory.

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A molecular dynamics study has been performed for water over wide ranges of temperature and density. The Carravetta-Clementi intermolecular potential model was applied for a system of 256 molecules. The liquid-vapor coexistence, near-critical and supercritical regions, and the region of compressed liquid having high density were extensively studied. The behavior of hydrogen bonds is analyzed in the present report. The number of bonds per molecule, their lifetime, and temperature-and density-dependences are presented in detail.

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The microscopic structures and behaviors of the liquid-vapor interface region are studied through molecular dynamics simulations of a liquid droplet which consists of Lennard-Jones particles (argon) or water (H₂O) molecules. The equilibrium properties of the simulated droplets are compared with the bulk values in the saturation states. A remarkable discontinuity of the local density is observed in the visualized instantaneous liquid-vapor boundary. The surface molecules are defined for each moment according to the number of neighbor molecules. The anisotropic local structures surrounding each molecule in the interface region are represented by two-dimensional pair distribution functions. In the case of water, the pair distribution functions also show the orientation of the surface molecules, which basically agree with the reported trends. The far infrared spectrum of the surface molecules of water is calculated and its relationship to the microscopic structures in the interface region is studied.

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The effect of porosity and void distribution on permeability was investigated, using the DSMC method. The purpose of using this method was to reduce the empirical value as much as possible. Rarefied gas flow through porous media was considered in the simulation. Since there was no difference in permeability upon varying the inlet and the outlet pressure, the adequacy of the method to calculate permeability was confirmed. It was found that the average permeability increases rapidly as porosity increases in a range of porosity greater than 0.4. Furthermore, it was verified that permeability strongly depends not only on the porosity but also on the void distribution. Hence, it was clarified that it is not effective to set a certain regularity in the arrangement for modeling porous media, and that the void in the model should be distributed irregularly.

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A quantitative analysis of critical heat flux (CHF) in both vertical circular tubes and rectangular channels under about 0.1 to 14 MPa was successfully carried out by application of the completely separated two-phase flow model to the comparatively low-velocity, upward-saturated two-phase flow, based on existing model of vapor blanket over the thin liquid sublayer on the heated walls at the CHF point, which was originally proposed by Haramura and Katto [Int. J. Heat Mass Transfer, 26-3 (1983), 389-399]. Over 1000 experimental CHF data were compared with analytical results and it was clarified that the analytical results gave good predictions of the existing experimental results of circular tubes of 3.0 to 7.8 mm in diameter and 0.15 to 0.6 m in length at 0 to 300 K and rectangular channels of 1.03 to 12.7 mm in channel gap and 0.15 to 0.94 min channel length at 4 to 328 K of inlet subcooling. The differences in characteristics of CHF between circular tubes and rectangular channels in upward-saturated two-phase How were also identified.

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It is easy to deduce the temperature in the case of a simple gas from the spectrum of pure rotational CARS (coherent anti-Stokes Raman scattering), but not in the case of gas mixture composed of several species, because the rotational lines of each species overlap at some regions in the spectrum. We propose a relatively easy method to deduce the temperature from the pure rotational spectrum of gas mixture. Air, which consists of oxygen and nitrogen, is selected as an example of gas mixture. In our method, a spectrum is partitioned into some sections and the ratios between line intensity of nitrogen and that of oxygen are calculated theoretically for each section. Once the spectrum of air is separated into those of nitrogen and oxygen, temperature is easily determined using the same method as for the simple gas. To examine the effectiveness of this method, temperature measurements are carried out along the centerline of a supersonic free jet of gas mixture.

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The enhancement of the saturated pool boiling heat transfer utilizing electric field has been studied. By selecting a small-scale heat transfer surface of 5 mm in diameter, the nucleate boiling heat transfer without the enhancement effect of the movement of boiling bubbles along the heat transfer surface has been realized to quantitatively examine the bubble deformation effect of the applied electric field. The boiling curves which have been experimentally obtained showed the enhancement ratio to be about twice that in the case where no electric field is applied. Therefore, by comparing these data with our previously obtained nucleate boiling curves on the larger heat transfer surface of 50 mm in diameter, which showed the enhancement ratio of about 50 times, it has been clarified that the effect of the deformation of bubbles in the electric field making the larger bottom area would cause the enhancement ratio of about twice and that the effects of violent motion of the bubbles along the surface would cause the additional increase of the enhancement ratio. To measure the thickness of the liquid film on the heat transfer surface under the boiling bubble, a capacitance probe has been devised by use of a heterodyne detector. Based on the results obtained using this capacitance proble, the high wall superheat increases the time of dissipation of liquid film in the case without the applied electric field. However, the liquid film on the heat transfer surface does not dissipate in high wall superheat due to continuous supply of liquid with applied electric field.

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This paper is concerned with the theory of film condensation of vapor on a shock-tube endwall behind a reflected shock wave. One-dimensional gas dynamics equations, together with thermal equations for a liquid film and the endwall, are solved to the first approximation by the method of singular perturbation. An approximate equation of liquid film growth is derived in a simple explicit form. It is clarified that the equation agrees well with computational results with an error of about 3%. The present theory suggests that the condensation coefficient (sticking probability) of vapor should be measured during the time when the growth rate of the liquid film depends on the condensation coefficient. The time, which is called the transition time of condensation, is defined explicitly in a theoretical manner.

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The vapor pressures of ethanol have been measured at temperatures from 310 K to 400 K, which corresponds to the pressure range from 15 kPa to 524 kPa. The uncertainties in the temperature and pressure measurements were estimated to be less than ±6 mK and ±0.4 kPa, respectively. Twenty-seven measurements were obtained at intervals of 10 K. The results were correlated as a function of temperature with a deviation of ±0.3 kPa. The temperature at 101.325 kPa on the vapor pressure curve calculated by the present correlation, i e., the normal boiling temperature, is determined to be (351.42±0.10) K. The effect of remaining water as an impurity in the ethanol sample on the vapor pressure measurements is discussed.

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Heat transfer from a heated wire and a heated vertical plate, which were in contact with the top of liquid surface, was studied experimentally. The curve representing the heat-transfer coefficient as a function of the temperature difference between the heaters and cooled tray could be divided into four parts. The range of each part depended closely upon the size of heaters, the depth of tray and the liquid properties. The mechanism of heat transfer from the heaters in each part was discussed. The following was shown. In the first part, where the temperature difference was the smallest, the heat was mainly transferred by conduction. The heat transfor was mainly due to natural convection in the second part, and was mainly due to Marangoni convection in the fourth part. The third part could be considered a mixed convection regime. Furthermore, it was found that the transition from the second part to the third part was suppressed by the meniscus of liquid surface which contacted with the heaters.

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A new enhancement technique was developed for natural convection heat transfer from a horizontal heated plate. In order to enhance the heat transfer, the grid fins made of copper plates were soldered to the base plate. These grid fins function not only as an extended surface but also as heat transfer promoters. The apparent heat-transfer coefficients of the above enhanced plate were measured and compared with those of a nontreated, flat plate and a conventional plate with vertical straight fins. It was found that the highest performance is achieved for the present plate. By adopting grid fins with appropriate size and height, the heat-transfer coefficient at the central portion of the present plate is increased by 35% compared to that of the conventional finned plate with the same fin area and fin height.

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The heat-transport characteristics for capillary looped pipes are obtained through experiments results. The capillary looped pipes are tested to obtain the flow direction of the vapor and the relation ship between the liquid charge quantity and the temperature. I discuss the motion of the working fluid based on the experimental results. In addition, the heat-transport characteristics were estimated based on the heat-transfer rate. Consequently the circulating direction is decided by setting the evaporator asymmetric with respect to the condenser. It was found that the flow regime changes when the heat density increases. The heat pipe mode changes to the circulation mode.

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When a coiled pipe rotates about the coil axis, the effect of rotation interacts with centrifugal and viscous effects to complicate the flow characteristics beyond those seen in stationary curved pipes. Following a previous paper on the flow characteristics, fundamental characteristics of convective heat transfer are studied for fully developed laminar flows through similarity arguments and computational studies. The variations of temperature contours with body force ratio and Prandtl number are shown for two Dean numbers. Empirical formulae for average heat transfer rate are given for a wide range of Prandtl numbers.

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A method to analyze the radiative energy transmittance through a nickel fibrous layer is developed by using the Monte Carlo method. The validity of the method is shown by comparing the results with the experimental ones obtained by Tong et al. It is also shown that the present analytical method gives more precise results than the two-flux method used by Tong et al. By using the mothod, it is shown that the angular profile of the radiative energy emitted from a black wall which obeys the cosine law is changed into a profile with strong forward transfer. By increasing the size parameter or decreasing the volume density of the fibers, the temperature difference in the layers and the heat flux are shown to be increased.

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Experiments and numerical analysis were carried out to investigate the dye transfer phenomenon induced by semiconductor laser irradiation. First, the dye transfer process was modeled by considering heat conduction and molecular diffusion. The validity of this model was verified by a good agreement between experimental and numerical results. Second, two types of printing media composition were proposed and examined. The results showed that dye-donor-layer absorbing type, in which laser energy was converted into heat in the dye-donor layer, was more advantageous in terms of both higher resolution and higher dye-transfer efficiency in printing images as compared to the surface absorbing type, in which the energy conversion occurred on the surface of the base film. Finally, the case of a moving heat source was examined. In this case there existed an optimum moving velocity at which the amount of dye transferred showed the maximum.

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An experimental investigation was performed on tube bundles in a liquid-fluidized bed. Results and analysis showed that the void fraction in a tube bundle can be calculated by correlations with no tubes when using mean liquid velocity. Also, results on heat transfer revealed that the heat transfer coefficient for a tube bundle can be calculated by the correlation with a single tube, proposed in the 1st report, when using the hydraulic diameter of the tube bundle.

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This paper describes an experimental study of impingement cooling characterisitics of heat sinks with pin-fin arrays. The experiments are performed with a variety of pin-fin arrays. For enhancing impingement cooling, one inlet orifice over the center of the heat sink is found to be the best geometric structure. The optimum orifice diameter is about 1/3 of the heat sink width. The optimum pin-fin diameter is about 0.5 mm for low blower power, and increases to 1.0 mm as the blower power increases. When the pin-fin diameter and the pin-fin number are constant, the heat transfer rate increases with increasing pin-fin height, but becomes almost constant when the pin-fin height is 10 mm or more. If the heat sink area or the pin-fin number is constant, the heat transfer rate reaches an optimum value when the ratio of the pin pitch to the pin-fin diameter reaches approximately 2∼2.5. By increasing the total surface area of the heat sink, the heat transfer rate per unit blower power increases, with a maximum value of about 5 to 6 times the fin base heat transfer rate without a heat sink.

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The Vuilleumier cryocooler is a heat engine which uses heat energy rather than mechanical energy to cyclically pressurize the working gas. The Vuilleumier cryocooler has the potential advantages of long lifetime and low mechanical vibration. This paper describes the specifications required for the machine, and detailes of design based an isothermal thermodynamic cycle. The analytical model can be used to clarity the working gas behavior in the system and determine the performance characteristics of the machine by calculating all losses to be mutually decoupled. As typical performance values from the calculation, the machine has a cooling capacity of 2.03 watts at 80 K under heater input power of 150 watts, charge pressure of 3 MPa and cycle speed of 4 s^-1. The nominal dimensions of the first trial machine are length of 300 mm, width of 150 mm and height of 280 mm. The weight of the complete machine was 6 kg.

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