Scanning electron microscopic investigations of particles produced by cavitation erosion and fracture surfaces revealed that the dominant mode of cavitation erosion is fatigue failure in 304 stainless steel. In addition, the surface roughness facilitates the fall-off particles, especially the longitudinal particles. The particles gathered can be classified into three types according to their shapes, namely longitudinal, triangular and mixed quadrangular hexagon. The spherical particles, which were observed previously in some reports on cavitation erosion, were not observed in this work.

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The relation between cavitation phenomena and three-dimensional boundary-layer transition on a 45-degree yawed cylinder was investigated using both wind tunnel and water tunnel facilities. Regularly arranged appearance of the cavitating bubbles on the cylinder surface seems to be caused by the crossflow vortices in the transition region of the same boundary layer. Physical properties like wavelengths are compared, and the results are in good agreement. Details of the two different phenomena are compared and discussed.

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Experimental investigations on the unsteady characteristics of the flow around a rectangular cylinder were carried out over a wide range of angle of attack and cavitation number. The width-to-height ratio d/h of the test cylinder is 2.8, which is called the critical value. Flow patterns have been observed by a highspeed camera and by pressure measurements. Notable features of various characteristics such as flow pattern, cavity length, periodic wake, surface pressure distribution, lift and drag are discussed.

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An investigation was made of the motion of a cavitation bubble in the vicinity of a free surface experimentally as well as theoretically. A bubble was produced by focusing a ruby laser into water, and subsequent behavior was observed with a high speed camera. The deformable nature of both a bubble and a free surface becomes significant when a bubble behaves relatively close to the surface. Immediately after the bubble rebound a secondary cavitation occurs, at around zero dynamic pressure region, which was developed in water between a rising free surface and a re-expanding bubble due to lower pressure caused by the interaction of reflected expansion waves from the surface. Some aspects of the bubble motion were compared with image theory with good agreement.

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To determine the optimal conformation of gate slots to suppress cavitation erosion, systematic experiments were carried out on the effects of the width-to-depth ratio ranging from 1 to 4 and of the offset mounted at the downstream edge of the slot on erosion: by using techniques of pressure-sensitive film and soft aluminium. Major cavitation takes place at three locations: vortex cvaitation within the shear layer spearated from the upstream edge of the slot (CAV-1), vortex cavitation within the slot (CAV-2), and attached cavitation within the shear layer separated from the downstream edge (CAV-3). "CAV-3" is directly related to the erosion around the slot. While "CAV-1" and "CAV-2" play important roles in the development of "CAV-3" as marked upstream cavitators. Finally, the suitable conformation of the slot is found to reduce the marked effects of the upstream cavitators on erosion.

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Steady and 2D-driven cavity flows were numerically simulated using the finite difference method. Pseudo-Liapunov exponents were obtained by measuring distances between particles initially located nearby. In the case where the moving lid was oscillated at a certain frequency, the particle paths showed a "folding and stretching" pattern and gave a positive exponent. We found that the pseudo-Liapunov exponent has its maximum at the oscillating period of 1.5T for Re=50.

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The motion of particles in a two-dimensional impinging jet is studied numerically. The fluid is assumed to be ideal. The motion of particles is governed by three dimensionless parameters: the Stokes number, the aspect ratio (the ratio of the distance between the nozzle and the wall to the half width of the nozzle) and the initial position of the particles. The critical conditions at which the particles first collide with the wall are obtained in the form of the function of these three parameters. The collision characteristics, namely, the location of collision, the collision frequency, the collision velocity and the force exerted on the wall due to collision, etc., are obtained. When the aspect ratio is larger than about 5, the collision characteristics are identified with those for the case of infinite aspect ratio. When the aspect ratio is smaller than about 1.3, no particle collides with the wall in regions near the stagnation point, and the locations of collision are focused at a point apart from the stagnation point. In the case where the distance between the nozzle and the wall is small, whether the particle collides with the wall or not is determined by the behavior of particles on the streamline, which do not pass through the stagnation point.

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This paper describes the detailed study of the flow structure over rows of two-dimensional square ribs on a ground plane for various values of S/D, and the optimum value of S/D to augment the turbulence of the free stream. The pitch between the centers of two adjoining square ribs was varied at S/D=2, 3, 4, 5, 7, 9, 13 and 17. The time-mean velocity, static pressure and the velocity vectors were measured by the Pitot and static pressure tubes, and a cylindrical yawmeter of 6mm in diameter having three pressure holes. The turbulence intensities and autocorrelation were obtained using the data processing system and the F. F. T. analyzer connected to the hot-wire anemometer. As a result, it is concluded that the pitch ratio S/D=9 is optimum to augment the turbulence intensity.

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Super-critical flow in spherical Couette system with only inner sphere rotating is investigated for clearance ratio 0.2 in terms of structures of disturbances and their wave speeds. Interior waves, ring vortices, Stuart vortices, shear waves, twists and wavy outflow boundary were observed. Ring vortex has four waves on it, and moves towards pole for one wave length (λ_φ=10°) in the meridian direction while it rotates for one wave length (λ_φ=90°) in the azimuthal direction. Rotational direction of Stuart vortex observed in the present experiment is opposite to the rotation of inner sphere. Iterior waves and twists have same character, and their wave speeds are same as that of oscillating inflow boundary of secondary flow. Both wave speeds of shear waves and oscillating outflow boundary are also same. The wave speed of traveling wave on outflow boundary is about two times of that on inflow boundary.

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An experimental and analytical investigation on flow separation in a two-dimensional closed channel has been carried out. In the experiment, one of the channel walls was moved by indentation from the outside to make a variable throat. The separated boundary layer was observed using flow visualization, and the pressures along the flow direction were measured using five pressure transducers. In the analysis, governing equations were formulated using a one-dimensional flow theory, taking into account the pressure loss due to flow separation. Comparison between the results of the experiment and the analysis shows that analytical and experimental values for the pressure loss due to flow separation agree only in a flow region where the flow is characterized by a parallel-sided jet. Observations on the flow separation and reattachment by flow visualization suggest the necessity of improvement for the one-dimensional flow theory used in order to predict the separation characteristic more accurately.

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Momentum transfer through an air-water interface was studied in a horizontal rectangular channel through experimental and numerical analysis. The liquid flow Reynolds numbers, based on hydraulic diameters, were 11500 and 17000. The air flow Reynolds number varied from 0 to 3260. In experiments, velocity distribution was measured by hot-film and hot-wire probes. The effect of the liquid flow Reynolds number and the direction of interfacial shear stress was investigated by performing the cocurrent and countercurrent experiments. The modified k-ε model was able to reproduce these experimental results qualitatively. The range of applicability of the modified k-ε model was also discussed.

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A numerical analysis has been performed for three-dimensional developing turbulent flow in a triangular duct by using a modified Reynolds stress equation model. Govering equations are transformed from the physical plane to the calculation plane by boundary-fitted coordinate systems. The calculated results are compared with the experimental data available. The present method can predict the generation of the secondary flow of the second kind which is a characteristic phenomenon for anisotropic turbulent flow. Moreover, we have shown that the measured normal stress, which is in the perpendicular direction to the base of the triangular duct, contains experimental error.

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The effect of a coating layer on the apparent viscosity of water in a tube is evaluated experimentally over a wide range of Reynolds-numbers (200-2000). In this study, a gelatin-coated glass tube, a paraffin-coated glass tube and a glass tube without a coating are used. The conclusions are summarized as follows: 1) At a low Reynolds-number region (20-500), the gelatin layer has the effect of decreasing the apparent viscosity by about 4%, but the paraffin layer does not have an effect on the apparent viscosity. 2) At a high Reynolds-number region (1000-2200), the gelatin layer suppresses the increase in the apparent viscosity due to the turbulent transition and a similar effect occurs in case of the paraffin layer.

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Bingham plastic fluid flows through pipes of circular cross sections coiled in circles were experimentally studied. In the investigations, kaoline clay slurries were used as the Bingham plastic fluid. The effects of the Reynolds number Re or the Dean number De on the friction factor λ_c in the laminar steady flow of the Bingham plastic fluid flowing through coiled pipes were clarified. The apparent Reynolds number Re_ap, expected to play the equivalent role of Re in Newtonian fluids, was introduced using the similarity law of energy dissipation which was derived from a generalized equation of non-Newtonian fluid. It was clarified that the effects of the curvature of the pipes are greater in the case of greater concentration of the slurry, and that there exists a good correlation between the friction factor and the apparent Dean number De_ap (defined according to Re_ap).

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Experimental study was carried out to examine the effects of pressure gradient for the fluid flow and heat transfer in the duct flow. Air flow in a fully developed turbulent state was decelerated through a linearly diverging section, and then accelerated through a linearly converging section. Experiments were performed with two different ducts, whose acceleration parameter K in the accelerating section was 2.2×10^-6 and 4.5×10^-6. The wall static pressure, the heat transfer coefficient and fluctuations of streamwise velocity as well as the time-averaged velocity profiles were measured. The heat transfer coefficient and turbulence intensity in the converging section were considerably lower than these in the diverging section and the viscous sublayer expanded in the converging section. The behavior of the increase or decrease of the heat transfer coefficient was similar to that of the turbulence intensity in the near-wall region.

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The velocity distribution, turbulence shear-stress distribution and static pressure of the fully developed turbulent flow through a circular pipe were numerically calculated and compared with the measured data. Numerical calculation was achieved by means of the momentum equation, the zero equation model for turbulence shear-stress and the integrated turbulence-energy production. The results show the superior reliability of this method.

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This research aimed to clarify the disturbance by a sphere in a point-source diffusing plume developing in grid-generated turbulence. Special concerns are given to the effect of the distortion of the mean stream near the forward stagnation point on the diffusion. Some results from statistical processing of experimental data are given. It is found that because of the strong distortion of the mean stream, the molecular diffusion in the vicinity of the stagnation point is accelerated to a great extent, and as a result, as the stagnation point is approached, the conditioned probability density function for near-zero concentration shows a remarkable slump. This result is explained qualitatively with the help of the pdf budget equation. A new concept, "smeariness", is defined and used to explain the experimental results effectively.

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A new technique of an active attenuator for pressure pulsation in liquid piping systems, which detects the progressive wave component of fluid-borne vibration and then controls the second source feed-forwardly by this detected signal so as to eliminate the progressive wave in its downstream pipe completely by producing the cancelling fluid vibration, has been presented, together with experimental results. As preliminary investigation in this study, the experiment on its attenuation characteristics has been carried out for only the harmonic fluid vibration, though the present active attenuator using the transfer-function-based control method is applicable to the wide-band random fluid vibration too. A general-purpose digital signal processor has been used for the high-speed operation of converting the pressure difference signal produced by two pressure transducers into the progressive wave signal of fluid vibration and for the successive operation of producing the control signal to the electrohydraulic servo cylinder (second source). It could be confirmed by the test in a model experimental pipeline that, when the present control system was operated, the pressure pulsation in a downstream pipe of the second source was reduced, as expected, to about 1/10 to 1/15 of that in the case where the control system was off (that is, transmission loss of about 20 to 25 decibels) over the frequency range of 20 to 250Hz.

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The free expansion of a spherical flow generated from a spot source can be described in terms of the polytropical process. It is well known that electron beam injection to the spot source is quite effective measure of raising the temperature of the limited surface. Namely, the energy demand to accelerate the freely expanding flow is supplied from the electron energy. In this paper, the heat transfer into the spot source due to electron beam injection, the driving force of the expanding rarefied gas, was calculated. In terms of the entropy-increase model, the polytropic coefficient was nearly 4/3, which corresponds to that of the homogeneously expanding flow, whereas the specific heat of the monoatomic viscous gas is 5/3. Hence, the flow velocity in the presence of electron beam heating was evaluated to be larger than that of the isentropic flow by a factor of nearly two. Furthermore, the dependence of the accelerated flow velocity upon the electron energy, current density and atomic number density at the source was discussed here.

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This paper describes a method for estimating the position of a detected leak by applying a fluid transient model to a real-time pipeline system. The method takes account of flow rate and pressure profiles along a pipeline in a transient condition based on an assumption of quasi-steady-state flow. The result of casestudies using a hypothetical gas pipeline system shows that, even in a transient condition, the method gives a more accurate estimation of a leak position than conventional methods which do not consider flow rate or pressure profiles along a pipeline. The method is also applicable to a pipeline having consumer stations which cause abrupt changes of flow rate profile along the pipeline. Furthermore, the influence of instrument errors on the result of the method is discussed. The result also shows that the method is more accurate than the conventional methods.

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A test sphere 100mm in diameter with programmable built-in processors was constructed to make surface pressure measurements at its free fall. The pressure data were stored in the body and transmitted to an external host computer after the landing for further processing. The tests were performed under the smooth-suface condition and were compared with the existing experimental data taken in windtunnels, up to the Reynolds numbers of about 105. The results showed that the gravitational acceleration was of little importance here, and that the apparatus worked with sufficient accuracy.

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A pressure gauge of the diaphragm type of high sensitivity has been developed to measure small differential pressures. Low and high pressures are each led to chambers which are separated with a membrane; the differential pressure between the two chambers give a displacement to the membrane, and the displacement is detected by a small laser displacement sensor through a glass window in the chamber wall. Tested membranes are permanently deformed in advance to a wavy form in order to give high sensitivity or are otherwise used in the flat condition. Easy exchange of the kinds of membranes makes it possible to widen the range of differential pressures measured. Calibration is made by means of a simple method using water heads. This type of pressure gauge can measure the pressure of magnitude from 0.1 Pa to 10 Pa.

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Laser Doppler velocity measurements were performed on developing pulsatile flow in a strongly curved tube under fllow conditions characteristic of the blood flow in the internal carotid artery called the siphon portion (curvature ratio of 1/2, Womersley parameter of 5.5 and peak Dean number of 750). The isovelocity contours of the axial direction show the flow development which is similar to the steady flow in a strongly curved tube with a fully developed inlet profile. However it is dissimilar to the steady flow in which imbedded secondary-flow helical motions occur within a large clockwise vortex (Dean type). During the deceleration phase, the reverse axial flow occurs near the inner side of the curvature. The appearance of reverse axial flow contributes to the oscillatory shear index (OSI). The values of OSI, which evaluate the reversed wall shear stress, increase with flow development at the inner side of the curvature and approach zero at the outer side of the curvature. These results show that the values of OSI are higher at the site of the atherosclerotic regions (fibrous plaques or localized cloudy thickening) found in the human internal carotid artery.

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The objective of this paper is to gain insight into the process of chemical reaction in turbulent mixing layers. To achieve this purpose, we have performed a direct numerical simulation of a three-dimensional chemically reacting mixing layer by using a spectral method. The results are reported for the case of velocity fields with initial periodic excitation. From these results, we have obtained the following conclusions: 1) On the streamwise vortical structures (ribs) in the braid region, the peak of the chemical production term exist; and 2) The core region have a large contribution to the total production in the mixing layer, whereas local production rate is not so high.

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In order to obtain information on vortical structures of noncircular jets, this paper describes the results of a vortex dynamics simulation on deformation of a pseudoelliptic vortex ring which consists of two parallel line segments of the same length connected by two semicircles of the same radius R. The cross section of the pseudoelliptic vortex ring was represented by one vortex blob to determine the evolution of its topology as a function of the aspect ratio L/(2R), where L is the length of the major axis. In a range of aspect ratio L/(2R)=2.0∼20.0, the vortex ring was found to have four fundamental patterns of deformation: pseudoperiodic axis switching; splitting into two vortex rings after axis switching; splitting into two vortex rings and their reconnection into a distorted vortex ring; splitting into three distorted vortex rings. Elimination of two antiparallel vortex blobs in close proximity was a useful means of extending the range of calculation of the deformation without having divergence of vorticity of the vortex blobs. Dynamical invariants of three-dimensional inviscid vortical motion were actually conserved within 10% of the corresponding initial values until the divergence of vorticity took place.

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With speeding up in high-speed boats and hydraulic machinery, it becomes an important issue to reduce the drag of the hydraulic elements. The computational fluid dynamics are very useful in precisely simulating the details of the local flow characteristics concerning the vorticity and the flow separation around a hydrofoil. We therefore investigate the flow characteristics in the steady inflow around a hydrofoil in an experiment with subcavitation and in computation with free-cavitation. Our computational results agree well with the experiments for the power spectra of the lift and the drag fluctuation, as well as the time-averaged values of the lift and the drag. The separation bubble calculated by the computation is visualized by the attached cavitation near the leading edge.

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A numerical technique for the computation of two-dimensional unsteady inviscid flows through an oscillating cascade is presented. To consider the oscillational phase difference between two blades, a concept of time phase shift is introduced on the periodic boundaries. A finite volume method is used to obtain the spatially discretized governing equations, while the second-order accurate Adams-Bashforth method is employed for the time integration. The example problems are the unsteady flows through oscillating cascades of the lens-type blades and compressor blades, and oscillational phase difference is chosen as a computational parameter. The present method gives unsteady periodic flow fields including the aerodynamic forces and moments acting on the blade clearly, and the positive damping energies are obtained in both test problems through all oscillational phase differences.

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Unsteady aerodynamic responses of a mistuned cascade subjected to incoming wakes from the upstream cascade are investigated in this study, here the extended Nishiyama-Funazaki method (1984) is used. Numerical calculations are made, focussing on the effects of restaggering of the cascade. It is accordingly found that there is some possibility of reducing wake-induced unsteady forces by controlling stagger angles without severe expense of cascade performance deterioration. In addition, quasi-steady flow analysis for the unsteady forces is proven to be adequate only in the case of the in-phase incoming condition of the wakes.

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We carried out 2-D cascade tests of multiple-circular-arc (MCA) blades with a relatively high camber angle of 56 deg. in the inlet Mach number (M₁) region of 0.4≤M₁≤1.2, and with systematic variations of cascade geometry and incidence angle. Systematic data with respect to inlet Mach number characteristics of the cascade of MCA blades were obtatained. We discussed the effect of inlet Mach number on the relationship between incidence angle and parameters of cascade performance (incidence angle characteristics) in the constant space/chord ratio of 0.6 in the third report. In the present report, the following items are discussed on the basis of experimental results in the constant stagger angle of 10 deg.: 1. the effect of space/chord ratio on inlet Mach number characteristics.; 2. the effect of space/chord ratio on the relationship between incidence angle and parameters of cascade performance (incience angle characteristics); 3. the effect of space/chord ratio on stall incidence angle, and reference incidence angle; 4. the relationship between incidence angle and critical inlet Mach number in the set of space/chord ratios of 0.4, 0.6 and 0.8; 5. optimal incidence angle and effective working range of incidence angle on the basis of critical inlet Mach number which was deduced from the above mentioned relationship of (4).

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The problem of noise generation due to the interaction between flows and plate edges is treated analytically. In uniform flow containing vorticity waves, two semi-infinite flat plates are placed with the trailing edge of one plate and the leading edge of the other being tandemly situated a finite distance apart. This flow field is considered to be a simplified model for self-excited tones such as edge tone and cavity noise. An approximate solution to the sound pressure is obtained by the Wiener-Hopf technique, and the calculated acoustic field shows the characteristics of the trailing edge noise and the Jeading edge noise. The sound pressure level varies with peaks and troughs as the wave number increases, especially in the region upstream from both edges, and these peaks show a frequency dependence similar to edge tones. Such a selective response mechanism will be explained by the phase relationship between vortex and sound.

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In the present work, a numerical scheme for the unsteady motion of shock waves in gases is developed based on Whitham's rule of geometrical shock dynamics (GSD). To investigate the effect of the initial shock strength on the shock reflection and diffraction on a wall, the two-dimensional focusing of cylindrical blast waves reflected from a concave elliptic wall is analyzed under various initial conditions. The results are compared with the finite difference solutions based on the piecewise linear method (PLM) as well as the experimental results. It is found that the geometrical shock dynamics is a practical and economical method to analyze the shock focusing process of the blast waves produced by exploding wires. Pressure change along the major axis of the ellipse shows good agreement when the present computations are compared with the experimental results as well as with PLM solutions.

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Detailed experimental analysis was made on the shock reflection over a wedge with surface roughness in a shock tube. The roughness was made by gutters carved on the wedge. The incident shock Mach number was M_s=1.43. The experimental parameters were the wedge angle and size of gutters. The wave configuration in the neighborhood of the triple point on the wedge is found to be nearly similar between model wedges. Detailed insight into the triple point trajectory shows that it is not a straight line but a slowly varying curve with a kink point where the slope of the tangent to the curve increases discontinuously and that the kink point coincides with the location where the secondly developed shock wave from the gutters overtakes the triple point. The local trajectory angle was found to decrease monotonously from the leading edge to the kink point, where it increases discontinuously. It then begins to decrease again, but not as steeply as the first decreasing region. The effective incident and reflective angles differ much from the ones obtained from the three-shock theory in front of the kink point. The angles coincide fairly well after this point. It is concluded that the secondary shock wave developed from gutters plays an important role for the structue of the reflected waves in the region investigated.

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The oscillatory characteristics of a pseudo-shock wave with a Mach number of 1.75 in a rectangular straight duct are experimentally investigated by static pressure measurements both on the duct axis and on the wall surface. The aspects of the pressure oscillation in the pseudo-shock region are analyzed from the treatment based on the intermittent characteristics, root-mean square, probability density function and cross correlation of the pressure signals. The correlation between the oscillatory characteristics and the flow mechanism of the pseudo-shock wave is also discussed in detail in the last part of the present paper.

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A theoretical and experimental investigation has been conducted on the vertical sloshing of a liquid metal induced by an unsteady electromagnetic force. The condition of stability is dominated by the Stuart number, the Weber number and the Reynolds number. It has been clarified that an increase of the Reynolds number or of the Weber number will make the system unstable, but an increase of the Stuart number will stabilize the system. It is also known that in the case where the amplitude of the electric field is kept constant, strengthening the magnetic field will cause an increase of the force of excitation but will damp out the disturbance, and that there exists an optimum magnetic field for excitation of the disturbance for a given wave number.

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The axial fan used for a pusher-type condenser cooling system of automotive air conditioners is one of the major sources of noise in an engine room, and many efforts have been made to reduce the noise emitted from the fan. In this paper, mechanism of the noise generation by a fan in the pusher-type cooling system is clarified, and some methods are presented to decrease the turbulent noise from it. Detailed studies on the flow around the fan were carried out both by computer simulations and LDA (Laser Doppler Anemometer) measurements. A considerable reduction in the noise level of the pusher-type cooling system has been achieved without any deterioration in the performance for different resistances in the condenser cooling system.

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In order to clarify the unsteady characteristics of an impulse turbine with self-pitch-controlled guide vanes in a reciprocating flow, an experimental investigation has been made by a turbine equipment in which the sinusoidal flow conditions are simulated. The results have been compared with those of a Wells turbine and the analytical results that are calculated on the basis of the experimental data obtained by the model testing of a turbine rotor with fixed guide vanes under steady unidirectional flow conditions. As a result, it has been clarified that the impulse turbine presented here is superior to the Wells turbine both in starting characteristics and speed reduction of rotor. The quasi-steady analysis is available for this turbine.

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To estimate the blade performance of a Darrieus-type cross-flow water turbine, differences between the characteristics of a Darrieus blade which moves along a circular path, and that of the blade at rest in a uniform steady flow are examined quantitatively by use of experimental data for three types of blades with different cambers or chord lengths from each other. It is found that a unique stall character strongly effects the drag force acting on the Durrieus blade. A model of the changing pattern of the drag coefficient by a dynamic stall is proposed from the results of measurement for estimating the blade characteristics. As the result, the blade characteristics and performances of the Darrieus-type runner are predicted well by the use of aerofoil data in a uniform steady flow and taking into account the effect of a circling motion, and the dynamic effect of the unsteady flow around the Darrieus blade.

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Characteristics of a nozzle-type fluidic pump, which has two nozzles set up opposite each other, were experimentally investigated. The pump performance is influenced by a pump installation level and a delivery pipe volume. The pump operating region controlled by a driving pressure is restricted by the receiver nozzle inlet cavitation. The discharge and the efficiency of the pump increase as the displacement volume increases in a certain operating range; however, a too large displacement volume produces little effect on the pump performance. As for the structural factors, the following is shown. In the case in which a pair of geometrically similar nozzles is adopted as the pump nozzles, the volumetric efficiency of the pump with small diameter nozzles is higher than that with large ones and the discharge is lower reversely. The pump composed of the almost-same-diameter nozzle pair can attain a higher discharge than that of a different diameter nozzle pair in a high head operation region.

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In order to study the possibility of using a vibration pump as a ventricular assist device, the pump performance and hemolytic property of the pump were evaluated. As a result, it was shown that the pump performance varied with the length and elasticity of the suction tube. The tested vibrating pump under discussion met the pump performance requirements of a ventricular assist device. The hemolytic property of the tested vibration pump was determined using goat blood. As a result, it was shown that the tested pump compared favorably with the conventional roller or centrifugal pumps with respect to hemolysis.

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This paper deals with the experimental examination of microscale mechanisms of heat transfer augmentation of fluidized beds; the direct-contact heat exchange from a heat transfer surface to fluidized particles was estimated for particles of various sizes. Contact period and frequency between the particles and heat transfer surface were measured by employing an optical technique, and the heat transfer between them was analytically evaluated. The obtained results showed that unsteady heat conduction to the fluidized particles plays an important role to the heat transfer augmentation, especially under the condition of incipient fluidization while the contribution of direct-contact heat exchange evidently decreases with increasing the particle diameter and fluid velocity.

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Analyses are carried out to study the effects of air velocity, particle circulating rate and fuel/air ratio on the profiles of the temperature and the heat fiux in circulating fluidized bed boilers. The particle density profile in the bed is obtained by solving a set of one-dimensional two-phase flow equations. The radiative heat transfer in the two-phase flow system is solved by using the Monte Carlo method. The following is obtained as the result. When the air velocity is increased, heat fiux to the wall is increased although the average bed temperature does not change appreciably. When the particle circulation rate is increased, the heat flux decreased although the bed temperature increased. When the fuel/air ratio is increased, both the bed temperature and the heat flux are increased.

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In direct contact melting, one of the factors that affect the heat transfer is the size of the heat transfer surface. This means that the shorter the path through which the melted liquid between the heat transfer surface and the solid of PCM (Phase Change Material) is rejected outside, the thinner the melted film, which decreases the thermal resistance between the source and PCM. In this study, how the heat transfer can be promoted by machining slots on the disk-type heat transfer surface and dividing it into several sector-shaped sections was investigated. Experiments were performed changing the number of splits and the width of slots under different surface temperatures and pressures. Numerical analysis shows a good agreement with the experiments. Summarizing these results, the enhancement of heat transfer can apparently be achieved according to the number of splits.

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Experimental investigations on the fluid flow and the heat transfer from a rectangular cylinder at an angle of attack to the air stream were carried out in the range of 2560≤Re≤12800. The width/height ratio c/d of the section was 5.0 and the angle a ranged from 0 to 20°. At α=0°, the separated shear layers reattach to the upper and lower faces intermittently. At α≥5°, the lower shear layer reattaches on the lower face. The reattachment flow becomes turbulent, while the flow is laminar at α>15°. The local heat transfer coefficients around the cylinder become clear in connection with the flow characteristics. The local heat transfers on the reattachment face, and the upper and rear faces are given by the same form as Nu=CRe^2/3. The constant C decrease with an increase in a at α>5°. Finally, the maximum average heat transfer is obtained between 0 and 5°.

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The equations of convective mass transfer are derived from the equations of convective heat transfer by changing Nu_c to Sh and Pr_v to Sc and also (X⁺/ω)Gr to (X/ω)Gr for free-convection condensation. As for forced-convection condensation, the present Rose's and Fujii's equations for mass transfer have almost the same accuracy, although their functional forms are quite different from each other. The accuracy of Rose's equation for heat transfer decreases as the effect of the enthalpy diffusion term increases. As for free-convection condensation, the present equation for mass transfer is more widely applicable in the range of W_R or M than the previous equation of Fujii et al.

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Liquid Lump velocities were experimentally determined for horizontal gas-liquid two-phase flow under a wide range of pressures from near the atmospheric pressure to a highly elevated pressure about 20MPa. The liquid lumps dealt here were liquid slug, huge wave, disturbance wave and ephemeral large wave. Velocities were determined using time-series signals of cross-sectional mean liquid holdup which were electrically detected at two axially separated locations of test tube. It is demonstrated how the mean values of liquid lump velocity and its standard deviation depend on the gas and liquid flow rates and pressure. It is obtained that the liquid lump velocity and its standard deviation are obviously affected by the pressure and are related flow patterns. The comparison of liquid lump velocities between vertical upward flow and horizontal flow are also discussed. The comparison has been also made between liquid lump velocities of vertical upward flow and horizontal flow.

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Absolute and precise measurements have been made of the thermal conductivity of HCFC-123 and HFC-134a (CFC Alternatives) in the liquid phase with a newly developed transient hot-wire apparatus for a low-temperature range. Up to the present, few experimental data about their thermal conductivity have been reported, particularly in the temperature range below 250K. The measurements have been performed on both substances in the temperature range from 193K to 353K, and in the pressure range from 1MPa to 30MPa. The accuracy of the measurements is estimated to be ±0.5%. It is found that the thermal conductivity of HCFC-123 is 12 to 15% smaller than that of CFC-11; on the other hand, in the case of HFC-134a, the thermal conductivity is about 5 to 25% larger than that of CFC-12.

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As a first step to predict the thermophysical properties of natural gases, generalized correlations for the saturated properties such as the vapor pressure, the saturated liquid density, the saturated vapor density, and the heat of vaporization have been formulated on the basis of the three-parameter principle of corresponding states with acentric factor for 9 component substances contained in the natural gases, i. e., CH₄, C₂H₆, C₃H₈, n-C₄H₁₀, i-C₄H₁₀, N₂, CO₂, H₂S, and O₂, and 3 simple fluids of Ar, Kr, and Xe. The present generalized correlation for the vapor pressure reproduces the experimental data within a deviation of ±1.0% in the reduced temperature range T_r>0.4. The present generalized correlation for the saturated liquid density reproduces the experimental data within a deviation of ±1.0% in the temperature range from the triple point to the critical point. The present generalized correlation for the saturated vapor density reproduces the experimental data within a deviation of ±2.0% in the reduced temperature range T_r>0.5. The reliability of the present generalized correlations for the vapor pressure and saturated liquid density was confirmed by the comparison with the experimental data for R22 and R114. The experimental data for the heat of vaporization are reproduced within a deviation of ±2.0% in the reduced temperature range T_r>0.5 by Clapeyron equation with the present generalized correlations for the vapor pressure, the saturated liquid density, and the saturated vapor density.

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This paper reports the measurement of the thermal diffusivity of thin films on substrate by the photoacoustic method. In order to examine the method, we built a new apparatus and proposed (1) a system calibration procedure using thermally thick materials and (2) a data analysis procedure based on the Rosencwaig and Gersho theory (RG theory). As a result of using a transparent photoacoustic cell, the systematic error factors which were caused by stray light have been reduced. With this apparatus, measurements have been performed on platinum, titanium and stainless steel (SUS304) thin foils (thickness: 50-100μm) with three different substrate materials (water, glycerol, and ethyl alcohol). The reproducibility was within ±7% regardless of the film thickness and substrate material.

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