To clarify the flow domain of erosive cavitation arising in typical bounded flows through a butterfly valve, the spatial distributions of cavitation-induced pressure pulses, which are directly related to the occurrence of cavitation erosion, are precisely studied by using pressure-sensitive films in the downstream region of the valve where extremely erosive vortex cavitation takes place predominantly. It is found that the erosive pressure pulses are distributed in a small limited part of the whole cavitating region which corresponds to the highly shear layers separated from the valve disc on the orifice side.

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To clarify the capacity effect by cavitation bubbles, the cavitation aspects and the vibrational acceleration were studied experimentally in pulsating flows through a branch duct. When the pulsation is given on the upstream side, the wall pressure and the flow velocity fluctuate in phase, while when the pulsation is given on the downstream side, there is a phase difference of 900 between them. The incipient and the desinent cavitation number have approximately the same value. The characteristics of such pulsations are independent of the pulsating conditions and the types of cavitation.

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The purpose of this study is to investigate the mechanism of various flow patterns of falling liquid film flow observed near an obstacle on a flow channel. In this report, a bend on the channel was chosen as the obstacle and the behavior of a ring-shaped swelling of the liquid film, which appears near the obstacle at a low flow rate, is considered. The Weber number at which the swelling shifts from the upside to the downside of the bend is theoretically estimated. The experimental results for the swelling behavior agree well with those of the above theory. Moreover, in order to investigate the characteristics of the stationary wave observed in the upstream side of the swelling, the wavelength and the damping rate of the amplitude were measured by the needle contact method. The measured results agree with the theoretical ones which were considered by the authors in the preceding report.

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This paper describes the flow past two perforated plates placed perpendicularly on a ground plane. The experiment was carried out in the N. P. L.-type wind tunnel with a 40cm×40cm working section of 2m length at the Reynolds number of 6.32×10⁴. The distribution of velocity in the flow field, the recirculation region between the two perforated plates, and the surface pressure on the ground plane were measured. The results were discussed for various values of porosity and spacing between the two perforated plates. As a result, it was found that the windbreak is practically effective for the perforated plate of porosity ratio λ=0.3.

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The problems of axially symmetric boundary layer flow over a rotating cone with uniform suction or injection in forced flow have been theoretically investigated. The nonlinear partial differential equations along a cone are transformed into ordinary differential ones by means of the difference-differential method. The solutions of the resulting equations are expressed in a form of integral equations, and the equations are numerically calculated by iterative numerical procedures. The results indicated that the axial and tangential velocity profile and the temperature profile shrink as the suction or injection parameter s increases. The drag and torque coefficient and the heat transfer coefficient increase as s increases.

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Accurate estimation of area-averaged volumetric fractions is required when we evaluate two-phase flow characteristics such as pressure drop and heat transfer. A two-phase flow model based on a local relative velocity is proposed in this study. The effects of distribution of local phase velocities and local volumetric fractions on the area-averaged volumetric fractions are also taken into account in this model by introducing new distribution parameters. In order to examine the applicability of this model to the estimation of the area-averaged volumetric fractions, measured area-averaged volumetric fractions of solid-liquid flow and gas-liquid bubbly flow in vertical pipes were correlated based on the basic equation of this model. The area-averaged volumetric fractions calculated by the correlation agreed well with the experimental data. Therefore, it was confirmed that this model is a useful two-phase flow model.

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In the design of high performance local exhaust ventilation systems, it is of great importance to maintain the capture velocity as high as possible at a certain distance from the hood opening. To meet this demand, the effects of hood geometry on the suction performance were investigated experimentally in a two-dimensional flow field for the flare-and the flange-type hoods of various flare angle, hood length and flange width. In the far region from the opening, higher centerline velocity is achieved by the hood of large opening ratio both for the flare-type and the flange-type hood, regarding the outer edge of flange as flange opening width. In the near region, however, the reversed result is obtained for the flare-type hood, and the flange-type hood is superior than the flare-type one. On the nondimensional diagram, all the data of centerline velocities are distributed on a single curve, including the case of the flange-type hood, when the values (velocity and area) at the opening are adopted as normalizing parameters. This curve, however, deviates gradually from a hyperbolic curve proposed by Silverman and this is a reason that the suction performance is affected by the hood geometry. It is also shown from the study on the head loss at the hood inlet that there is an optimum flare angle of about 25°.

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A decompression suction system is often installed in front of a compressor to reduce the compressor drive power in the case of large compressor test rigs. In such cases the surge behavior is different from that in the absence of a decompression facility. This paper reports numerical results by an extended analysis based on Greitzer's model and compares to surge experimental results of an axial compressor with the decompression chamber, and shows that a critical resistance coefficient dependent on the suction throttle setting divides the surge patterns into two groups: one is limited to the maximum period with rather high frequency. and the other is similar to the relaxation type with low frequency. Further, an explanation is given for the difference in behavior between the surge in the installation with a decompression chamber and the one with no chamber.

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The flow mechanism of two-phase confined vortex flow in a vortex chamber has been investigated experimentally. The control technique for the swirling bubbly flow along the outer wall was established experimentally. It was confirmed that the annular liquid flow was formed by controlling the separated liquid flow rate from the exhaust holes of the outer wall and by adjusting the location of the annular exhaust slit. It was also found that the scale of bubbles was larger at the middle part of the swirling liquid region, and that the distribution of the impact pressure was disturbed near the exhaust slit. The data obtained here could be useful for developing various vortex chambers accompanying the gas-liquid two-phase swirling flow.

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The effect of vortex chamber height on the characteristics of gas-liquid centrifugal separation in a vortex chamber has been investigated experimentally. It was made clear that the stable swirling liquid flow could be formed along the outer wall of the vortex chamber with the height of 20mm to 40mm. However, the unstable radial drop flow was observed in the height of 80mm over the range where the separated liquid fraction dropped steeply. In the shorter chamber, the radial width of separated liquid flow and the separated liquid fraction became larger. The data obtained here could be useful for designing a short vortex chamber.

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This paper describes the formation and decay of vortex shedding and turbulent eddies from a circular cylinder of finite length placed on a ground plane. The experiment was carried out in an N. P. L. blowdown-type wind tunnel having a working section of 500mm×500mm×2000mm in size at the Reynolds number 2.5×10⁴. The power spectrum, auto-correlation and space-correlation were measured and the Strouhal number was determined. The vortices of two types shed from a circular cylinder have also been observed. As a result, it was found that (i) the vortices shed from a circular cylinder are arch vortices for H/D=1 and 2, and change into Karman vortices at H/D=4∼7; (ii) the number of turbulent eddies of a large scale contained in the turbulent near wake increases as the downstream distance increases, and the scale of eddies in the near wake enlarges with an increase in the value of H/D.

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The paper describes hydraulic loss and secondary flow in wavy bend pipes of rectangular section. Hydraulic loss and secondary flow in those pipes changes in a complex way with the aspect ratio of the rectangular section. Hydraulic losses are measured. Also, velocity distributions are measured by LDV and flow patterns are visualized. Turbulent intensity in wavy pipes is investigated.

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Cylindrical duct flow with swirling is applied frequently to the combustor, furnace, etc. This paper describes the formation of a recirculation zone in the cylindrical duct with swirling flow. Some numerical computations and experiments have been performed on the change of contraction of the area and the location of the outlet of the cylindrical duct for Reynolds numbers up to 1000. The experimental values agree well with the calculated ones. These results have clarified the flow pattern, the size and shape of the recirculation zone for the change of Reynolds number, the ratios of contraction and the location of the outlet.

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A numerical investigation of the flows in a pipe with varied area is reported. As the governing equations, the three dimensional compressible Navier-Stokes equations written in a quasi conservation law form on general curvilinear coordinates are used. The numerical method is based on the method of lines using the rational Runge-Kutta time integration scheme combined with the central finite difference approximation for the spatial discretization. In order to comfirm the reliability of the present approach, low Reynolds number flow in a sudden pipe expansion is considered as a test problem. The computed reattachment length is in good agreement with other established results. Next calculations of the flows in a pipe with a valve are carried out. The results are compared with those of Bicen's experiments. Flow coefficient and flow patterns for each valve lift are accurately obtained.

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Oscillatory flow is examined experimentally in a two-dimensional furrowed channel. We show the transition of two-dimensional to three-dimensional flow due to instability of the flow at moderate Reynolds numbers. The critical value of the Reynolds number at the onset of three-dimensional flow strongly depends on the Strouhal number. The fluid motion is found to be most unstable in the limited Strouhal number range of 0.02 to 0.03. Two distinct three-dimensional flows are discovered and their boundary is determined only by the Strouhal number, i. e. St≒0.02.

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A study is made to clarify the effect of magnetic field on the boiling two-phase flow characteristics of magnetic fluid. At first, the basic equations of one-dimensional boiling two-phase flow are solved. It is confirmed that heating and boiling of magnetic fluid in the downstream side of the applied magnetic field are effective for pressure rise in a nonuniform magnetic field. Feasibility of the development of a new energy conversion system using boiling two-phase flow of magnetic fluid is confirmed by the experimental study which shows reasonable agreement with the analytical result.

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Basic study is conducted on the oscillating motion of a magnetic fluid pulg and a piston in a U-tube with an exciting periodic magnetic field as a simple example of the magnetic fluid plug actuators. Assuming that the effect of a magnetic field on a pipe friction is constant, frequency-response curves for the displacement of the piston are obtained by the numerical calculation. Furthermore, the experimental study is carried out for comparison with the theoretical analysis. The theoretical analysis shows good agreement with the experimental results of the resonance frequency. However, prediction of the maximum amplitude requires the correction for a piston seal friction.

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In the present paper, the dynamic behavior of magnetic fluid surfaces in containers were experimentally examined. Experiments were carried out for rectangular, cylindrical and spherical containers. These containers were horizontally oscillated. The vertical nonuniform magnetic field was applied by permanent magnets which were set underneath the containers. The test liquid was a magnetic fluid with fine magnetite particles in a water carrier. It was found that the harmonic wave motion, swirling waves and flow pattern of surface waves were influenced by the magnetic fields. The resonant frequency of the liquid-container system moved toward the high-frequency region with increase of the magnetic field intensity. This behavior was also studied by the linear theory. Theoretical results were qualitatively in good agreement with experimental results.

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A supercavitating hydrofoil is approximated to a lifting-line, along which an up-wash velocity distribution is derived by introducing the separation of variables into an equation of motion with respect to disturbance pressure. After considering the dependence of lift coefficient upon other physical quantities, the expression taking account of the non-linear relation between lift coefficient and attack angle peculiar to cavitating hydrofoil is shown. A lifting-line equation is derived from an assumption that two dimensionality holds at any spanwise position, and the method of solution of the lifting-line equation, in which a eigenvalue problem of the Sturm-Liouville type should be solved, is presented. The method to obtain the cavity spanwise distribution, in which the solution of the lifting-line equation is used, is proposed, and effects of main stream velocity profile, aspect ratio and cavitation number on cavity spanwise distribution and its three dimensional effect are clarified.

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Mass separation in the interacting region of opposed two-dimensional free jets of argon-helium mixture is investigated by use of the direct simulation Monte-Carlo method. The mixture ratio of argon in helium is set at 10%. Spatial distributions of argon mole fractions are obtained for the upstream inverse Knudsen numbers, 1/Kn, in the range of 0.62 to 61.2. Outward flow from the stagnant region is collected by a skimmer, which has the same width as the slit, W, and is located at a distance 2W from the centerline. For this condition, argon is enriched effectively and the optimum separation effect is observed at 1/Kn=25.

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The wake-rotor interaction analysis code, which was originally developed for the inviscid flow case by the author (1983), was improved by introducing a newly proposed wake decay model. This model utilizes the Reichardt's semi-empirical correlations for the wake decay behind the cylinder. From a comparison between experiments and the predictions obtained by original and modified versions of the code, it is found that the incorporation of that model could make the analysis code to provide better results.

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Turbulent energy spectra in a stably stratified shear flow were studied experimentally using a laser Doppler velocimeter and thin wire thermocouples. The energy spectra were compared with those of isothermal shear flow, and a buoyancy effect was estimated. The following results were obtained. (1) The energy spectra of a stably stratified shear flow approached those of isothermal shear flow as the wave number increased. (2) The intensity of energy spectra of the stably stratified shear flow dropped from the isothermal level owing to the buoyancy effect in a low wave number range. (3) The difference in energy spectra between stratified and isothermal flows was directly proportional to the -3rd power of the wave number.

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A cigar-shaped axisymmetric turbulence field is experimentally investigated. The equivalent integral scale and the scale of the maximum energy-dissipation rate estimated for the axisymmetric turbulence were almost equal to the scales of isotropic turbulence, which shows that they are valid for determining the characteristic wavenumber range in the spectrum of nonisotropic turbulence, such as the range of energy-containing eddies, the inertial subrange and the energy dissipation range. Energy spectra were measured and the energy dissipation spectra and energy transfer spectra were calculated. The aspects of their streamwise evolutions suggest that it is indispensable to recover the isotropy of the large energy-containing eddies before the turbulence energy begins to be steadily supplied into the dissipation range from the inertial subrange.

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In this paper, the numerical analyses on the behavior of the heavy monoatom beam are presented. Some numerical methods for the analysis of rarefied flow have been proposed so far, which have been successful as applied to the flow Kn<1 such as in the semiconductor manufacturing processes and other vacuum technologies. However, since the atomic number density of the beam is extremely low, the flow is categorized as the molecular flow (kn>1) in which the molecular free path is rather large compared with the representative scale of the beam. Hence the probability density function of the atomic free path in the nonequilibrium field was considered in the numerical simulation of the beam propagation. Consequently, the calculated results on the beam diffusion due to mutual atomic scattering agreed well with the measured data by means of the gadolinium vapor.

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To investigate the motion of fluid particles round a cylinder in turbulent flows, we have developed a new model simulating the trajectory of particles: the combined model of Kinematic Simulation (KS) and Random Flight (RF). The large-scale turbulence is simulated by a sum of random Fourier modes varying in space and time, and the small-scale turbulent fluctuation is simply modelled by ITO type of stochastic differential equation with a memory time comparable to a Lagrangian integral time scale T^L_S of small-scale motion. The Lagrangian properties of fluid particles in homogeneous isotropic turbulence with uniform mean flow has been examined. Some new results have been obtained using this new model: (a) the cross-correlation of the displacements by the large and small scale motions is negligibly small; (b) the random small-scale motion causes the decorrelation of the large-scale velocity; (c) the value of T^L_S used in RF is estimated from pure KS.

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When a partial differential equation is solved numerically, it is usual to discretize the calculating domain into many elements by elaborate handwork. For this discretizing, we devised a new method with which the three-dimensional domain can be divided automatically into Voronoi polyhedron elements around arbitrary nuclear points. This method is described in detail giving an example. When Voronoi polyhedron elements are used, the various differential equations can be easily transformed into simultaneous algebraic equations for each of the nuclear points, for which parallel processing can be done more speedily and accurately. Moreover, the Voronoi polyhedron element table has possibilities of future growth; it can be used directly as an analytical method of solving a partial differential equation and it can be transformed into an ordinary tetrahedron element table.

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For swash plate-type piston pumps and motors, because of the large radial loads, fluid film lubrication is difficult to establish between the piston and cylinder wall only with hydrodynamic effects. In this paper, the design method of the piston with hydrostatic pads around which the fluid film can be formed is derived, and the effects of operational conditions and pad dimensions on the film formation are numerically shown.

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A unique approach was developed in this study to investigate some effects of the rotor-stator axial spacing on the aerodynamic excitation by the incoming wakes. This approach utilized the wake decay models which were derived from the preceding experimental correlations for the wakes behind the airfoil (Silverstein's model). Numerical results are presented in the paper which showed the axial spacing on the magnitude of the unsteady fluid forces clearly. Moreover, it is found that the incorporated wake decay model can yield better prediction of the unsteady pressure distribution on the airfoil.

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Abrasive wear patterns of materials were studied using experimental apparatuses of an impinging jet in air, an impinging jet in water and a rotating disk. These were also compared with patterns obtained with prototype turbines. Ploughing was main type, with some wedge type observed in the prototype turbine. These patterns resembled those observed for some test results with the impinging jet. Test results on the impinging jet could be shown on the abrasive wear mode diagram, applying the maximum degree of penetration D_pmax and shear strength f at the contact interface.

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In order to produce a desired time variation of the pressure and the flowrate independently in a pulsatile pipe flow, the method of controlling the pump speed and valve opening simultaneously is proposed taking the inertia effect into account. Here the following two examples are presented. One is the flowrate pulsation along a sine curve with maintaining the pressure constant, and the other is the pressure pulsation with constant flowrate. Any variation of pressure and flowrate can be produced by the combination of these two cases. The possibility of the present method and the limit of the pulsatile period are determined by comparing the nonsteady control with the quasi-steady control.

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An axial-flow pump impeller has been designed by authors by means of a fully three-dimensional inverse method to obtain high suction performance. This report presents experimental results of the cavitation tests for the pump designed. The suction specific speed of the pump achieved the maximum value of 2995, which was calculated from the required NPSH defined at 3% head reduction due to cavitations. The leading edge cavitation was distributed uniformly over the blade spanwise location at the shockless entry flow rate. For the impeller with wide tip clearane, the suction specific speed reduced due to strong clearance cavitation. The flow oscillations measured in the low NPSH region are discussed.

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Based on extensive experimentation and observation of condensation on finned tubes with radial ridges on the fin surfaces, a model was developed to predict the condensation performance of that tube. Not only the overall condensation performance, but also the local condensation rates were predicted by this model. The predictions accurately coincide with the experimental data. The ridges on the fin surface play an important role in condensation heat transfer enhancement, because the ridges not only extend the thin condensate film area but also promote convective heat transfer in the film.

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The effect of electrohydrodynamical (EHD) phenomena on the enhancement of condensation heat transfer has been researched to develop the high performance heat pump. The actual proof test of EHD condenser has been performed for the condenser of high temperature heat pump (temperature of about 150°C) by utilizing the heat transferring medium of C₆F₁₄ (perflorohexan) and the influence of the lubricating oil on the performance of EHD condenser (shell-tube condenser) of 50kW capacity which was composed of 102 vertical tube) has also been researched experimentally. Enhancement ratio of condensation heat transfer has been attained up to 6 times by using C₆F₁₄ and we clarified that the lubricating oil has not negative effects on this EHD condenser.

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An experimental study was performed to investigate the characteristics of wall skin friction and heat transfer for a flat plate turbulent boundary layer with an insertion of a LEBU (Large Eddy Break-Up) plate. The measured skin friction coefficient in the downstream region of a LEBU plate was confirmed to be reduced by the insertion of a LEBU plate, and the heat transfer was also found to decrease in the same region. It was also found that the dissimilarity between momentum and heat trasport processes was weak. The reduction of the fractional contributions to Reynold's shear stress in the near-wall region from ejection and sweep was concluded to result in the reduction of the skin friction factor and of the heat transfer coefficient when a LEBU plate was inserted. Unlike the case when a cylinder was inserted, interactive fluid motions were not intensified.

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Heat transfer from a circular cylinder with constant heat flux placed in a saturated porous medium and subjected to cross flows is studied both analytically and experimentally. Order of magnitude analysis reveals two distinct regimes present during the transient process; the heat transfer for small times is dominated by conduction, but it is eventually balanced by convection at a large time. It is also derived analytically that for a given heat flux the mean surface temperature rise at steady state depends on the cross-flow velocities. At steady state the wall temperature is not uniform, but varies along the circular position. Experimental work is conducted in order to verify the analytical results. It appears that the analytical predictions reasonably agree with the experimental results.

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The present paper describes the characteristics of the local heat transfer and the flow around a single cubic-type spacer on a heated surface in a parallel plate duct. Temperature measurements were performed using thermosensitive liquid crystal film. The transformation from the color to the temperature was improved in the RGB method, and the local heat flux was compensated by solving the heat conduction equation with boundary conditions of the detailed temperature distribution. The space between the spacer and the wall affects the onset of alternate vortices and recovery of the local heat transfer behind the spacer.

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Heat transfer characteristics of a spirally finned tube bank with a staggered tube arrangement for waste heat recovery from the hot gas have been experimentally investigated. The finned tube banks used in this study have a tube arrangement, tube dimension, and fin material different to that of air-cooled heat exchangers. It is shown that the heat transfer characteristics of these finned tube banks differs greatly from those of the finned tube with the equilateral triangular tube geometry for the air-cooled heat exchangers. The new heat transfer correlation for the prediction of the heat transfer coefficient of the finned tube banks for waste heat recovery is induced concerning the effect of the nonequilateral tube geometry, which differs from that of anair-cooled heat exchanger.

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Pressure drop characteristics of a spirally finned tube bank with a staggered tube arrangement for waste heat recovary form the hot gas have been experimentally investigated. The finned tube banks used in this study have a tube arrangement, tube dimension, and fin material different to that of air-cooled heat exchangers. It is shown that the pressure dorp characteristics of these finned tube banks differs greatly from these of the finned tube with the equilateral triangular tube geometry for the air-cooled heat exchangers. A new correlation for the prediction of the pressure drop in the finned tube banks for waste heat recovery is induced concerning the effect of the tube geometry, which differs from that of an air-cooled heat exchanger.

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Attention should be paid to the unsteady chracteristics in a fluidized bed in order to clarify the fundamental mechanism of heat transfer in a gas fluidized bed heat exchanger. The unsteady local heat transfer characteristics around a single horizontal heated circular cylinder immersed in a fluidized bed were studied as a problem on a fluidized bed heat exchanger. Firstly, a new heat flux sensor was developed, which was tolerant to the abrasion due to particles in a fluidized bed. The static and frequency characteristics of the heat flux sensor were found to be appropriate. Secondly, instantaneous local heat transfer coefficients around a cylinder were measured by connecting the sensor to a constant temperature anemometer. The signals were analyzed to obtain time-averaged value, variance, probability density function, power spectrum, etc. The local behavior of particles near the cylinder was also observed. The dominant mechanism of heat transfer was discussed on the basis of those results.

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Attention was paid to the unsteady natures in a gas-solid fluidized bed in order to clarify the fundamental mechanism of heat transfer in a fluidized bed heat exchanger. The following unsteady local properties were measured simultaneously around a heated circular cylinder in a fluidized bed: (1) heat transfer coefficient, (2) wall pressure and (3) discrimination between emulsion and void phases. Those unsteady signals were analyzed statistically. The arrival frequency of bubbles on the cylinder surface, the mean contact time of the emulsion and bubble with the cylinder surface, the rate of contribution of the emulsion and bubble to heat transfer coefficient, etc. were obtained. On the basis of these characteristics, a new model of heat transfer around a circular cylinder was developed, in which the effect of the sliding of the emulsion was considered. Finally, the dominant mechanism of heat transfer was made clear quantitatively.

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In this study, the authors studied mechanisms of heat transfer augmentation around the stagnation point of an impinging air jet laden with solid particles. Primary attention was paid to the heat transfer augmentation around the stagnation point of gas-solid two-phase impinging jets due to unsteady heat conduction between the laden particles and heat transfer surface. The unsteady heat conduction to a solid particle was numerically studied and effects of thermal properties of both solid particles and the heat transfer surface were examined. The results clearly showed that the amount of heat conducted to a particle is influenced not only by the thermal properties of a particle but also by the ones of a heat transfer surface. Using the obtained results, the authors introduced an evaluation procedure which can separately assess the contribution of unsteady heat conduction. This procedure utilizes the change of unsteady heat conduction by the thermal properties of heat transfer surface material; the contribution of unsteady heat conduction is inversely evaluated by comparing the numerical results of unsteady heat conduction with the heat transfer augmentation measured for the different heat transfer surface materials.

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In this paper, the authors studied heat transfer augmentation around the stagnation point of an impinging air jet laden with fine solid particles. Heat transfer around the stagnation point was measured for nine combinations of solid particles and the heat transfer surface material so as to examine the effects of the thermal properties of both laden particles and heat transfer surface on the heat transfer augmentation due to unsteady heat conduction between them. The contributions of unsteady heat conduction between the laden particles and heat transfer surfaces were separated from other heat transfer augmentation mechanisms by employing the separation technique reported in our previous paper. The results clearly showed that the contribution of unsteady heat conduction increases with increase of the product of heat capacity and thermal conductivity of the heat transfer surface material as well as of the laden particles. For a given combination of solid particles and heat transfer surface materials, the contribution of unsteady heat conduction is dominated primarily by the contacting frequency between the laden particles and heat transfer surface. This means that the heat transfer augmentation due to unsteady heat conduction becomes evident as the particle diameter decreases.

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A method of discretizing a three-dimensional closed space into the Voronoi-polyhedron elements was applied to the numerical analysis of heat-conduction problems in heterogeneous solid mixtures. The computation was done for various mixtures of two randomly distributed components. Thermal conductivity of the two-component mixture is more strongly affected by the arrangement of components with respect to the mean heat flow direction than by the shape of components. The statistical mean of thermal conductivity can be roughly approximated by the geometrical average. Empirical formulae were obtained from the results. In order to accurately predict the thermal conductivity of a mixture of three or more components, the numerical calculating method divised in this study can be employed successfully.

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The convective boiling heat transfer of an immiscible binary liquid mixture has been investigated by using water as a main fluid. R113 and R11 were atomized into the water as volatile material. When the boiling of the volatile material occurs, the heat transfer is cohanced by the bubble formation near the heating surface. The heat transfer enhancement occurs by the addition of a small amount of volatile material, and is insensitive to further increases in its concentration. The enhancement is remarkable in the case of low Reynolds number. The heat transfer enhancement was also observed under the condition that gas bubbles were generated on the heating surface by electrolysis, and it was clarified that the enhancement is caused by the agitation effect of bubbles near the wall.

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An experimental investigation was performed using model packages mounted in five columns and up to twelve rows on the floor of parallel channels. Each package has the base area of 22×22mm², the total height of 17.6mm and is equipped with a finned heat sink. The fin geometries and arrangement, as well as the air velocity, were changed, and their effects on heat transfer from the packages and channel pressure drop were investigated. The difference of the heat transfer coefficient between a variety of finned heat sinks was evident at the upstream portion of the rows. On the other hand it was very small downstream. The heat transfer coefficient from the first package downstream of the missing package was found to increase to the level of complete mixing of cooling air. It was effective to place obstacles between the packages to promote mixing and to increase the heat transfer coefficient. However, the increment of the pressure drop did not change the per-pumping power heat transfer coefficient.

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Boiling heat transfer and flow characteristics were investigated in vertical upward flow of liquid nitrogen. Observed boiling heat transfer was in a nucleate boiling mode. Heat transfer coefficients in the nucleate boiling mode were well correlated by Schrock-Grossman's equation. Flow patterns observed in this experiment were classified mainly into single-phase flow of liquid, bubbly flow, slug flow, annular flow and inverted annular flow. Based on the experimental observation, the flow regime map for LN₂ was presented, and the applicability of the flow-regime transition criteria by Mishima-Ishii was verified.

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An experimental study of void fraction and temperature profiles in nucleate pool boiling of Freon 11 around a horizontal cylindrical copper surface is reported. The results obtained from the amplitude probability distributions of temperature fluctuation show that temperature within the thermal sublayer region fluctuates widely, and beyond this region the distribution curve changes from Gaussian to the chi-squared type distribution function. It is found that the bubble boundary layer near the heated wall has an effect on the thickness of the superheat layer.

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Liquid lump velocities were experimentally determined for vertical upward gas-liquid two-phase flow under a wide range of pressure from near atmospheric pressure to a highly elevated pressure, about 20 MPa. The liquid lumps dealt with here are the liquid slug, huge wave, disturbance wave and ephemeral large wave. Velocities were decided using two sets of signals of time-varying cross-sectional mean liquid holdup which were electrically detected at two axially separated locations of the test tube. The effects of flow parameters such as gas and liquid flow rates as well as pressure on liquid lump velocities are described. The initiation of transition from plug flow to huge wave flow is also discussed in the presentation of the results.

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In our previous study, it was found experimentally by LDV measurements that a large-scale annular vortex is formed during the compression stroke at a swirl case, and this vortex generates and transports turbulence. This report elucidates the above phenomena by means of a mathematical calculation: when an axial stratification of swirl intensity exists, a large-scale annular vortex is formed during the compression stroke by an interaction between the piston motion and the axial pressure gradient. This trend is enhanced when the swirl intensity is the highest at the piston top surface and the lowest at the bottom surface of the cylinder head. Based on this result, a new concept is proposed to control the turbulence generation during the compression stroke.

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The flow pattern of solids in a downcomer of an L-valve was classified mainly into four patterns: packed-bed pattern, coexistence pattern, oscillation pattern and pseudobridge pattern. The solid flow rate and the static pressure distribution were closely related to these flow patterns. Based on the experiments using the small-scale two-dimensional L-valve model, flow pattern maps were presented. Furthermore, simple realationships between the solid flow rate and the gas flow rate in the L-valve were derived.

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