The small particle on a liquid surface near a vessel wall tends to approach the wall spontaneously. Such behavior of the particle on the liquid meniscus near the wall was theoretically investigated. Because of the solid-liquid wettability, an unbalanced force is caused in the tangential direction to the liquid surface and the particle moves toward the wall. Since the particle is excessively drawn into the liquid due to the wettability, the excessive buoyant force acts on the particle in the perpendicular direction. The force caused by the wettability is directed in the normal downward direction to the liquid surface and is balanced with that component of the buoyant force. Then the tangential component of the buoyant force is not balanced and the particle is moved upward along on the meniscus surface. The particle trajectory calculated following the above theoretical consideration agrees with the experimental one observed by a high-speed video camera.

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In this study, the unsteady characteristics of an air entraining vortex and a submerged vortex in a suction sump are investigated. The period of their appearance and their existing time are measured for various submergence of the suction opening under the condition of a constant suction flow rate in two suction sumps of different types. As a result of the present study, it is confirmed that the continuously air entraining vortex and the submerged vortex appear intermittently, while the suction flow rate and the submergence are kept constant. Moreover, it is known that the unsteady characteristics of the air entraining vortex are divided into three features in connection with the submergence.

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Angular distributions of molecular flux effusing into vacuum from various circular nozzles are measured by means of the Bayard-Alpert ionization gauge. The range of the Knudsen number is approximately from 0.01 to 10. The experimental data are summarized into a best-fit equation. The dependence of angular distributions on the Knudsen number and the nozzle length-to-diameter ratio l/d is discussed through the coefficients in this equation. Collimation of molecular flux is remarkable when the Knudsen number and l/d are large.

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The characteristics of an air jet issuing from two kinds of exit shapes with an aspect ratio of 5 were measured by using hot-wire anemomers. Emphasis was placed on the measurement of the flow field of the two bilaterally symmetric planes of the jet. The measured quantities include mean velocity, turbulence intensity, Reynolds stress and the production term of turbulence energy. It is found that the axial component of turbulence becomes larger than the other components. It is also found that the position of maximum mean velocity gradient, that of maximum Reynolds stress and that of velocity half-width differ from each other on the two symmetric planes, and that the distributions of the Reynolds stress and the production of turbulence energy show a remarkable change according to the exit shapes. In addition, it is interesting that the relative magnitude of the Reynolds stress changes in the planes for the orifice-type jet.

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A modified one-dimensional mathematical model is presented to describe unsteady separated-flow in a two-dimensional elastic channel made of a pair of membranes supported from the outsides by distributed nonlinear springs. Modified governing equations are derived from the two-dimensional flow equations of continuity and momentum from a mathematical point of view, assuming that the flow in the diverging region downstream of the separation point is characterized by a parallel-sided jet surrounded by dead water. Numerical calculations have been performed to compare the present model to the previous one. A numerical example shows that the amplitude of the self-excited oscillation predicted by the former model is smaller than that by the latter. The rapid change of the pressure distribution downstream of the throat of the channel is suppressed by the correction term introduced in the momentum equation.

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The three-layer model has been proposed for the analysis of a two-phase critical flow through a converging nozzle. Most of the previous analyses on a two-phase flow hae been based on a homogeneous or a separated model in their fundamental conservation equations. These results were found with large deviations in the actual measurements for two-phase critical flows. The presented model is assumed to be three-layer flow with a mixing region between gas and liquid phase layers. The numerical results on our proposed model have revealed the effects of the mixing layers on the critical flow. The measurements of the critical flow rate and the pressure profiles were conducted with air-water flow through a converging nozzle. The calculation results of these models have been discussed in comparison with the experimental data for the flow rates and the pressure distributions under the critical condition.

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Derivation of constitutive equations for interfacial momentum transfer between two phases in three-phase flow was carried out in this study. For a preparation of this derivation, the validity of Andersen's equation for the interfacial momentum transfer in two-phase flow was examined. This examination clarified that Andersen's equation cannot be applied when the density difference of two phases or a body force is small. A new constitutive equation for the interfacial momentum transfer in two-phase flow, which can be applied even to the above-mentioned case, was derived from the area-averaged momentum equations. Then, similar constitutive equations for the interfacial momentum transfer between two phases in three-phase flow were derived using drift-flux correlations for hypothetical two-phase flows which are conceived by excluding one phase from the three phases. Constitutive equations for drag coefficients between two phases were also proposed.

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Allievi's formula is well khown for approximately calculating the maximum pressure rise in a conduit caused by a water hammer. This formula is obtained, neglecting the elasticity of the conduit, the compressibility of the Fluid, linear closure of the valve, and the head loss of the conduit. The object of this paper is to discuss analytically the effect of the head loss of a conduit on the pressure variation. As a result, a formula for linear closure of the valve, and a method approximately calculating the maximum pressure variation caused by a water hammer not only of cases considering the effect of head loss but also for a system having a conduit downstream from the valve, are obtained.

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The standard k-ε two-equation model fails to predict turbulent swirling flow in a pipe rotating around its axis. In this study, the k-ε model is modified with the aid of the Reynolds stress model and is applied to the swirling flow. The laminarization phenomenon and the circumferential velocity profile in the swirling flow are predicted by the model proposed. The Richardson number is introduced to the ε-equation to take the curvature effect into account; however, this common method appears to fail in this type of swirling flow.

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A numerical method employing physical components of the tensorial quantity as dependent variables on boundary-fitted curvilinear grids is applied to the simulation of flow in arbitrary cross-section curved pipes for an imposed pressure gradient of oscillatory nature. The basic equations are formulated for Stokes fluid. The computation for a Newtonian incompressible fluid in curved concentric annuli and curved eccentric annuli was carried out for the range 10³ ≤ De ≤ 10⁵, 1 ≤ Wo ≤ 10², where De is the Dean number and Wo is the Womersley number. It is found that, at very low or very high Womersley number, the amplitude of the wall shear stresses derived numerically is in good agreement with that of the zero-th order of the asymptotic expansions of the solution of concentric annuli as the curvature parameter δ tends to zero, and that 2 pairs of secondary flow appear for even low Womersley number, contrary to the case of the circular coiled tubes.

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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 Reynolds numbers, based on hydraulic diameters, were 1200 (Case 2) and 11500 (Case 1). The air flow Reynolds number was varied from 0 to 5000. In experiments, velocity distribution was measured by hot-film and hot-wire probes. In Case 2, when the interface was smooth, it behaved like a solid wall. However, in the other cases, the behavior was different from a solid wall. In numerical analysis, the k-ε model was modified to satisfy asymptotic behavior of k, ε and Reynolds stress to the interface. The numerical results agreed well with the results of Case 1 qualitatively.

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An analytical study of oscillatory flow of a magnetic fluid in a circular pipe in a nonuniform magnetic field is conducted. The numerical calculations are carried out to clarify the effect of a magnetic field on the flow characteristics. It is clarified that the effects of fluid compressibility and applied magnetic field on the fluctuating pressure appear in the higher-frequency range. However, the calculated values in the low-frequency range only qualitatively explain the experimental results.

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An experimental study is presented for the subsurface phenomena and the splashing produced by the impacts of magnetic fluid drops against immiscible liquid layers under nonmagnetic and magnetic fields. Magnetic fluids used in the experiments were water-based ferricolloid W-35 and its dilution with distilled water, and a target liquid was kerosene. It was found that the subsurface phenomena and the splashing of magnetic fluid drops depended on the magnetization of magnetic fluids. In the case of higher magnetized drops, the size of the subsurface cavity was very small, and the splashing was scarcely observed. On the other hand, the compound Rayleigh jet was formed during the splash of a magnetic drop on a kerosene under nonmagnetic field. It was also found that the bubbles made of thin magnetic fluid film were formed in the target liquid at a certain value of mass concentration in magnetic fluid.

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This paper describes a new device for measuring the flow rate in a pipeline. The device has a bow-shaped constrictor similar to a segmental orifice. Experiments were carried out for three opening area ratios from 0.50 to 0.75 and over the range of the diametral Reynolds number of Re=(1.5∼15)×10⁴. The results are summarized as follows: (1) It is recommended that the pressure tappings be located (0∼0.25)d upstream of and (0.25∼1.0)d downstream of the constrictor, respectively. (2) The curves of the discharge coefficient are shown to be flat for Re=(2.2∼5.0)×10⁴. Compared with pipe orifices of the same opening area ratio, the critical Reynolds numbers of this flowmeter are found to be reduced to one-eighth of those of the orifice.

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An analytical method for the partially cavitating wing in spanwise shear flow between two parallel plane walls is proposed. An equation of motion with respect to disturbance pressure is transformed into two problems by separation of variables. One of them is that of the spanwise direction and the other is that of the wing sectional plane. For the former, an existing analytical solution is adopted and the latter is reduced to a simultaneous integral equation with respect to singularity distributions and solved by introducing an analytical method previously proposed by the author for the noncavitating wing in spanwise shear flow. These two kinds of solutions corresponding to the individual eigenvalues are combined linearly, and the expressions for the wing and cavity characteristics are obtained. Numerical calculations are carried out to clarify the notable effects of cavity length, main stream velocity profile, and aspect ratio on the cavity and wing characteristics of the partially cavitating wing in spanwise shear flow between two parallel plane walls.

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This paper describes a study on the development of a proper airfoil section for the vertical axis wind turbine (VAWT). We aim to abtain pitching moment in the negative direction without losing the excellent characteristics of a symmetrical-type airfoil section. Thus, we propose an increase of the thickness of the symmetrical-type airfoil by giving a meanline reversal, that is, negative meanline near leading edge and positive one near trailing edge, measured from blade chord line. Thus, the airfoil section can be designed by setting the parameters of a reverse meanline and basic airfoil section, and this airfoil section will be called the TW series airfoil section. From the three component force characteristics measured in wind tunnel experiment, TW series airfoil section is regarded to preferable for VAWT, thus, validity of design concept of TW series airfoil section using reverse meanline was demonstrated.

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An S-type tubular turbine is used for a low-head hydraulic turbine. The S-type draft tube plays an important role in the S-type tubular turbine. The S draft tube has two bend portions, first and second bends. Separation occurs here. The pressure recovery becomes low because of the separation. The paper proposes a new-type S draft tube which has the highest pressure recovery coefficient. One of the characteristics of the new draft tube is a twisted portion in the middle of the S draft tube. Asymmetrical secondary flow is generated in the twisted portion of the new S draft tube. The pressure recovery coefficient Cpo is largely improved because such asymmetrical secondary flow prevents the separation on the bend portion of the S draft tube. Such phenomena are assured by measuring the velocity distribution in the draft tube.

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A numerical analysis was carried out to determine the effects of vertical finned surfaces on the characteristics of water vapor absorption into aqueous lithium bromide falling films. The temperature of the wall including the fin was assumed to be of constant, and the fully-developed laminar film was assumed to have a constant thickness. Calculations were performed for several combinations of fin height and fin pitch. It was shown that the absorption rate was greatly enhanced by the fin's cooling effect within a certain distance from the inlet. It was also shown that the absorption rate was further increased by mixing the film, after the film had flowed a reasonable distance down from the inlet.

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The entrainment rate of liquid droplets in a two-phase annular mist flow is investigated in the helically ribbed and wired tubes with the aim of suppressing the droplet entrainment to improve evaporative heat transfer in various steam generators of the one-through type. The results show that the entrainment rate in the tubes is lower than that in smooth ones. An experimental correlation is introduced between the suppression rate of the entrainment and the parameters including liquid and gas flow rates and the shape of the ribs or wires. The decrease in number of disturbance waves is supposed to be the main cause of the entrainment suppression and is brought about by the direct interaction between the disturbance waves and the helical ribs or wires.

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In order to realize the higher performance heat pump, an electro-hydrodynamical (EHD) condenser utilizing the combination of two kinds of EHD phenomena has been researched. In this study, to maximize the augmentation effect, experimental study has been carried out to clarify the details of an EHD pseudo-dropwise condensation. The diameter of the drops has decreased according to the increase of the electric field. The condensation heat transfer coefficients have increased in proportion to the electric field strength to realize the maximum local heat transfer coefficients of over 9000 W/m²K in CFC 113 and over 11000 W/m²K in HCFC 123. Furthermore, the heat transfer coefficients have become of the same order under the condition of the the same quantity of falling condensate.

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A Twin-fluid atomizer of the film impingement type exhibits a good performance in spray characteristics. For application to the twin-fluid atomizer, we propose a new film generation method which is greatly liquid-jet-impingement-on-the-wall type. In this type of atomizer, the liquid film thickness influences the spray characteristics. In this report, the thickness distributions of liquid films formed by obliquely impinging jet on the wall have been calculated and compared to the measurements. According to the calculation, as the Reynolds number of the liquid jet increases, the film thickness decreases. The greater the distance between the stagnation point on the wall and the measuring point, the more uniform the film thickness becomes. The calculations of film thickness are slightly thinner than measurements. But the calculations of thickness distribution are qualitatively coincident with measurements.

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In a previous paper, we proposed to apply the liquid jet impingement method to the twin-fluid atomizer. This type of atomizer is expected to have good performance on the spray characteristics. On the other hand, liquid film (upwash) is formed by the interaction between liquid films which are generated by two impinging jets on the wall. This upwash has great influence on atomizer performance. Firstly, thickness distributions of liquid film generated by the impingement of a single jet on the wall at a right angle have been calculated and compared to the measurement. By comparison, calculations show a slightly smaller film thickness than do the measurements. Also, influences of several factors on film thickness were investigated. Secondarily, calculation results of thickness distribution were applied to the calculation of thickness distributions and the contour of upwash. Concerning the contour of upwash, calculations were compared to the measurement. The calculations are qualitatively coincident with the measurements.

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Solid/liquid phase change heat transfer in porous media is more complicated than the heat transfer in ordinary materials. Although several studies have been made on the heat transfer in a rectangular cell, no systematic experiments appear to have been conducted on the effects of various parameters. especially the eftect of the orientation of the test cell, for the melting and solidification processes. The purpose of the present study is to clarify the effects of the orientation of the test cell, the size and material of the solid particles, and the wall temperature on the heat transfer.

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Entrainment behavior on a density interface of stratified fluids is very important for the design of innovative nuclear reactors. In the present study, the turbulent energy in the upper stratified fluid was supplied by an injection and extraction flow. The turbulent intensity in the upper fluid was proportional to the injection and extraction velocity at the nozzle. The entrainment was done by liftup of filaments from peaks of the interfacial wave. The entrainment velocity was inversely proportional to a overall Richardson number. These results could be obtained when the turbulent energy released from the energy-containing eddy was proportional to the energy consumption by the entrainment.

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The Kutateladze correlation (1948) is widely used to predict critical heat flux (CHF) for various geometries of heated surfaces. A reasonable model which gives the correlation is not yet known. In this paper, the physical implications of the correlation are discussed and a model giving the correlation has been proposed. This model is derived on the basis of the measured diameters of various bubbles and the photographic records of boiling in higher pressures by Semeria (1963). In the model, a macrolayer δ₁ is formed by the coalescence of the secondary bubbles formed by the primary bubbles. Tertiary bubbles formed by the secondary bubbles determine the frequency f of the macrolayer formation. The CHF is determined by the following relation: q_CHF=δ₁ρ_lH_fgf, where ρ_l is the density of liquid and H_fg is the latent heat of evaporation. One of the formulations of the model gives the Kutateladze or Zuber correlation.

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Natural-convection film boiling heat transfer from a horizontal flat plate facing downward has been analyzed by assuming the liquid-vapor interface to be smooth because the interface is expected to be stable from viewpoint of the Rayleigh-Taylor instability. However, experimental results show that these analyses considerably underpredict the heat transfer coefficient. In the present study, an experimental study is conducted to examine such discrepancy. The results otained can be summarized as follows. The liquid-vapor interface remains smooth for film boiling in small wall-superheat region, but the interface becomes to be wavy as wall-superheat increases. The transition superheat increases with increasing subcooling and decreasing intensity of external disturbance. The heat transfer coefficient of film boiling with wavy interface is larger than that with smooth interface. A simple analytical model is developed to predict the saturated film boiling heat transfer with smooth interface. The agreement between the analytical model and the experimental data is good as long as the interface is smooth.

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Enhancement of heat transfer was investigated experimentally on a natural convection adjacent to a vertical, heated plate. A V-shaped diverter plate was attached on the surface of the vertical plate and was utilized as a heat transfer promoter. The flow and temperature fields around the diverter plate were visualized to grasp the mechanisms of heat transfer enhancement. The local heat transfer coefficients were also measured using water as a test fluid. The results show that the high-temperature fluid ascending the vertical plate branches at the edge and flows away to both sides of the diverter plate. The low-temperature fluid enters the region behind the diverter plate instead. Thus, the heat transfer coefficients are increased markedly here. The optimum height and inclination angle of the diverter plate were also investigated.

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An experimental study was conducted on the heat transfer under the condition of constant heat flux around a circular cylinder with a single tripping-wire for various diameters, which was affixed at various positions from the forward stagnation point of the cylinder. The testing fluid was air and the Reynolds number Re, based on the cylinder diameter, ranged from 1.2×10⁴ to 6.2×10⁴. Especially investigated are the relations between the heat transfer around the rear face of the cylinder and the flow of the near wake. It is found that the heat transfer around the rear face decreases with increasing of the length of the vortex formation region.

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An experimental study was performed to investigate the effects of oblique rib angle on forced convection evaporation in a vertical upward flow of refrigerant R12. Heat transfer coefficients and pressure drops were measured for four channels with different rib angles (θ=30, 45, 60, and 90°) at mass velocities between 50 to 130kg/m²s and mass qualities between 0.2 and 0.8. Flow observation was also conducted to clarify the differences of heat transfer performance and pressure drop among these channels. The results show that the rib angle has a significant effect on the heat transfer and pressure drop, and the heat transfer performance of the channel with θ=45° is most excellent under the conditions of the same mass flow rate and the same pumping power. Higher heat transfer of this channel is due to the accelerated flow without stagnation along the oblique rib, and the lower pressure loss is due to little collision with the intersection of ribs.

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Condensation of steam on a subcooled water layer was studied in a cocurrent horizontal channel at atmospheric pressure through experimental and numerical analysis. The liquid and vapor Reynolds numbers, based on hydraulic diameters, were varied experimentally from 6900 to 21900 and from 7700 to 19700, respectively. The experimental results showed promotion of heat transfer by the existence of interfacial waves. The numerical analysis predicted a heat transfer coefficient lower than the experimental results. This discrepancy can be explained by the fact that the numerical results showed decay of turbulent viscosity near the interface because of severe restriction of turbulent values.

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Two-dimensional numerical computation has been performed for unsteady flow appearing in a channel obstructed by an inserted square rod. The computation was made for several cases of different rod sizes and of different inlet velocity profiles. The rod was located on the center plane of the channel and the flow Reynolds number was kept constant (Re=1000). Two additional cases were also studied. One of them is the case where the channel walls move at a speed of induced channel Reynolds number to be 1, 000. Another is the case when the rod was located in a uniform flow. The performed computation and the grid point system used were validated by comparing the Strouhal number calculated for the latter of the additional cases with available experimental data. The present computation made for several cases reveals that the behavior of the vortex street formed downstream of the rod can differ from the counterpart of the vortex street formed by the rod placed in a uniform flow. In the latter case, the vortices shed from the upper half of the rod remain in the upper half of the flow area, and the vortices shed from the lower half remain in the lower half of the flow space. However, in several calculated cases, it was found that the vortices shed from the rod move laterally in a remarkable fashion. The vortices shed from the upper half cross the center plane of the channel as they move downstream, and those from the lower half of the rod move towards the upper half of the flow space. In order to confirm this strange numerical result, flow visualization was also performed for flow in a channel obstructed by a square rod.

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Two-dimensional numerical computation has been made for unsteady flow in a channel obstructed by an inserted square rod. The results of the computation made for the inlet flow with a parabolic velocity profile and for specific values of channel Reynolds number and rod size are studied in detail. In particular, the statistical features and the time variation of the flow are discussed based on the obtained results. From the statistical viewpoint, the flow is demonstrated to be highly periodical, therefore almost free from randomness or irregularity so that it is quite different from turbulent flows. However, the obtained results reveal that the momentum transfer is enhanced due to the apparent shear stress resulting from the nonzero value of cross correlation between the streamwise and lateral components of fluctuating velocity. Two characteristic features are discussed in detail for the time variation of the flow. One is related to the lateral motion of the vortices shed from the rod highlighted in the previous study. It is discussed in terms of the periodical variation of the separation vorticity layers formed from both sides of the rod. Another is the formation of a 'wall vortex', which affects the wall heat transfer, as will be described in the next paper, and is formed under the lifted tip of the wall vorticity layer.

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Two-dimensional numerical computation has been made for unsteady velocity and thermal fields realized in the channel obstructed by an inserted square rod. The previous papers were devoted to the discussion of the obtained velocity fields. The present paper deals with the thermal field and wall heat transfer. The streamwise distribution of time-mean local Nusselt number reveals that heat transfer is augmented by the flow unsteadiness in the region downstream from the rod. Its peak at x/H=1.6 is caused by the peak of instantaneous Nusselt number, which first appears at x/H=0.8 and moves downstream accompanying the value of peak height. At this peak position, instantaneous wall shear stress takes the value lower than its time-mean value. Therefore, dissimilarity between the heat transfer and the momentum transfer exists there instantaneously. The peak position also corresponds to the position inside a wall vortex. Above this wall vortex, another isolated vortex, which is a disconnected tongue of the separated wall layer, can be identified. The latter vortex induces a clockwise circular fluid motion around itself. This fluid motion causes the reduction of wall friction, the formation of wall vortex and the washing action of the wall. The washing action entrains fresh fluid from the downstream side under the isolated vortex, maintains the instantaneous Nusselt number larger there, and contributes to generate the instantaneous dissimilarity.

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A study was conducted to see if it is possible to enhance the heat transfer in the downstream region of a backward-facing step, where heat transfer is normally deteriorated, by the insertion of a cylinder near the top corner of the step. The flow Reynolds number, cylinder size and streamwise position of the cylinder were kept constant but the cross-stream position of the cylinder was changed in three steps. The results of the heat transfer experiment, flow visualization and measurement of the averaged and fluctuating flow fields were reported. When the cylinder was mounted in a position a little higher than the step top surface, a jetlike flow pattern appeared in the averaged velocity profile beneath the cylinder, and the recirculating flow was intensified. Therefore, the velocity of recirculating flow near the wall is increased at some streamwise positions. Additionally, velocity fluctuation is intensified, not only in the shear layer between the jetlike flow and the recirculating flow regions but also in the near wall region. These intensifications result in the effective augmentation of heat transfer in this case. Therefore, it is concluded that the mounting of a cylinder is effective if it is mounted in the proper position.

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An experimental study was made on heat transfer and flow characteristics behind slightly heated circular cylinders with various cylinder diameters under lower constant free-stream turbulence. The examined range of the cylinder diameter tested was from 10mm to 14mm. The obtained Nusselt number increased as either the Reynolds number or the cylinder diameter becomes larger, which definitely occurred in the case of 12mm. The laminar-to-turbulent transition region in the separated shear layer moved in the upstreamwise direction in the relatively large cylinder diameter case. It was found, therefore, that the variation of cylinder diameter has an effect on the transition phenomenon in the separated shear layer, so that the heat transfer characteristics behind circular cylinders are also influenced.

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Laminar heat transfer in separating and reattaching flow was numerically studied by simulating flow and heat transfer behind a backward-facing step, in which the temperature field was investigated in a very wide range of Prandtl number to elucidate its influence on heat transfer. It was demonstrated that the heat-transfer enhancement, usually assumed around the flow reattachment point, is not consistently realized. It occurred for the cases of Prandtl numbers greater than 0.1, but was by no means observed for lower Prandtl number cases.

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An investigation of flow and heat transfer characteristics in a two-phase double-tube thermosyphon was performed experimentally using water, ethanol and R113 as the working fluids. A theoretical study was also made on the circulation mass velocity. As the heat flux increased, the circulation mass velocity measured experimentally first increased and then decreased. After that, for ethanol and R113, the mass velocity increased again at a certain heat flux where the heat transfer coefficients also increased stepwise. It is considered that this particular behavior was caused by a change in the flow pattern. For water, the calculated circulation mass velocity agreed well with the experimental results. For ethanol and R113, however, the agreement was not good enough because the change in the flow pattern was not taken into consideration in the theoretical calculation. However, the calculated mass velocity indicated the average line passing through the experimental data.

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An efficient explicit-implicit finite difference algorithm for the transient heat conduction problem is developed. The algorithm is based on the alternative use of the explicit and implicit scheme for the time integral of the transient heat conduction equation depending on the total heat conductance of mesh elements. The algorithm has so simple a structure that it can be applicable to a variety of transient heat conduction problems. Particularly, the algorithm is effective for multi domain problems and strongly irregular mesh problems. In this paper, the basic idea of the algorithm and a method to determine an optimum time increment are described. Also, the evaluated results of accuracy and acceleration of the calculation by the application to the one-dimensional transient heat conduction problems are described.

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In transferring heat energy by fluid, it is well known that heat capacity of piping affects the heat loss at the transient state. Above all, heat loss from the piping of a solar collector system is one of the most important subjects from the viewpoint of increasing the performance of a system utilizing solar thermal energy. For reducing heat loss from the piping, we manufactured a piping made of only thermal insulation material, which we called a thermal insulation pipe; i.e., TIP. In order to demonstrate its effectiveness, we performed experiments of transient temperature response of the outlet of a piping system in comparison between a TIP and a piping which is composed of a metal pipe covered with thermal insulation material which we called ordinary insulation piping; i.e., OIP. Furthermore, numerical calculations and simple analysis of transient heat loss in both piping system were performed. This paper describes the effectiveness of the TIP from the comparison of the major results of experiments and calculations.

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A new measuring method of solid-liquid contact angles is proposed. The well-known phenomena that the liquid meniscus formed under a downward solid surface spontaneously falls down at a certain height of the solid is applied to the measurement of the contact angles. The relation between the contact angle and the critical height of the solid surface at which the instability occurs was theoretically obtained considering the solid-liquid wetting behavior from a thermodynamic view-point. Applying the theoretical results, the contact angles can be obtained by measuring the critical height of the solid. The validity and the usefulness of the method were experimentally confirmed for various solid surfaces and test liquids.

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As a first step for analyses of the air flow behavior in a fire tunnel, a k-ε model is applied for a two-dimensional and unsteady turbulent flow to predict velocity and temperature distributions in a ventilated tunnel with a local electric heater. Buoyancy effects are included in both the vertical momentum and the turbulence equations. Convective and radiative heat losses are accounted for. A version assuming C₃ to be an empirical function of the ventilation Reynolds number and the densimetric Froude number at the heat source has been tested. The predictions are compared with experimental data and shown to be in reasonable agreement.

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In order to examine the structure of a high-intensity turbulent premixed flame to a further extent, an attempt has been made to examine the dependence of the characteristics of ion current on the flame configuration, i.e., the local flame curvature. When the curvature is smaller than the critical value, the maximum value of the ion current decreases and the half value period of the ion current increases as the flame curvature decreases. Even though the local flame curvature is constant, the ion current fluctuation changes its shape significantly as the flame path across the probe changes.

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The two-dimensional distribution of soot particles in an unsteady free spray flame in a rapid compression machine was visualized using the laser sheet scattering technique. Scattered light from soot particles was taken by a CCD camera via a high-speed gated image intensifier. The scattered light image of a 40 mm x 50 mm cross section taken at 70 mm and 90 mm downstrem from the nozzle tip showed that the soot concentration is the highest in the periphery of the flame tip region. The soot concentration in the center of the flame is low and homogeneous at the early stage of the combustion, but later it becomes uneven and higher. As the fuel injection pressure is increased from 55 MPa up to 134 MPa, the soot concentration is considerably reduced, but the uneveness of the soot distribution does not change much.

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A two-stage entrained bed coal gasifier has the feature that the entire coal gasifier can be operated at a low air content by controlling the coal and air feed rates to the combustor and the reductor section, respectively, independently. This paper describes the results of computer analysis on the different coal feed ratios to the combustor and the reductor before the test with our 2T/D coal gasifier. The main results are as follows: (1) We can expect a higher cold gas efficiency and calorific value at a lower combustor/reductor coal feed ratio, with the temperature of the raw gas at the combustor section kept constant; (2) In general, it is effective to lower the coal feed rate with the entire air feed ratios kept constant, for efficiently gasifying the high ash fusion temperature coal, but we assume that a high temperature cannot be obtained at the combustor section because the heat loss through the 2T/D gasifier wall tends to sharply increase at a lower combustor/reductor feed ratio.

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The aim of this study is to simulate the combustion behavior in a packed bed filled with catalytic balls. The burning of the low-calorific gas composed of hydrogen, carbon dioxide and air was simulated, and the temperature of the catalytic ball and the hydrogen burnout were predicted. From these studies, the following conclusions were obtained. (1) On the catalyst in the combustor, there are a H₂-rich region and an O₂-rich region. (2) With the increase of the excess air ratio, the maximum catalyst temperature increases and the length necessary for complete combustion decreases. (3) With the increase of the velocity, the catalyst temperature is kept constant but the length necessary for complete combustion increases.

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The effect of radiation heat transfer on the transient combustion of a single fuel droplet with a finite rate of chemical reaction and variable physical properties has been clarified under the assumptions of spherical symmetry. Evaporation curves, transient variation of flame location, temperature profiles, and the ratio of flame to droplet radius were compared to the previous results without radiation effect. It was shown that the radiation has at least a 25-percent effect to lower the maximum flame temperature. Further, the present results were compared to the experimental results obtained by several researchers.

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Using an ignition accelerator, some series of heat release progress for the variation in ignition timinng were collected and analyzed to clarify the influence of the burning characteristics of the rapid combustion period on the burning process of the succeeding combustion period of a quiescent chamber D.I. diesel engine. On the basis of clear correlations held between the values relating to the burning process, it was found that the mass of fuel injected in the period after the end of rapid combustion is the fundamental factor which controls the burning process in the controlled combustion period, and it governs such characteristic values of this period as the mass of the burnt fuel, the burnt proportion of fuel, and the burning speed. Discussions on the burning mechanism of the fuel spray are also given.

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New mixture formation technology (OSKA) of a direct fuel injection stratified-charge engine was developed by making a fuel jet against an impingement part provided in the piston cavity. A four-stroke single cylinder spark ignition engine with the OSKA system was examined with gasoline fuel. A single hole nozzle with relatively low opening pressure was used. As the fuel-air mixture is formed mostly in the cavity, it is possible to prevent end-gas knocking, and to employ compression ratio 14.2 higher than that of the conventional premixed SI engine. The test results showed that the high brake mean effective pressure of 1.04 MPa and high brake thermal efficiency of 37.7 % were obtained.

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The coolant and cylinder wall temperatures during warm-up are important factors for car heater capacity and fuel economy. These temperature rises depend on the heat transfer from the combustion gas. However, the exact temperature simulation is difficult in a engine because the heat transfer coefficient, coolant speed, heat capacity and heat transfer area are different depending on places and time. In this paper, these temperatures have been estimated under an assumption that one side of the materials with large heat capacity is heated by constant-temperature gas and another side is cooled. The values calculated by this method indicate a good approximation to the experimental ones.

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To examine the values of constants in submodels such as the k-ε turbulence model, flame kernel ignition model, irreversible reaction model and heat loss model, the two-dimensional combustion process in a spark ignition engine with or without a prechamber is calculated numerically, while changing the constant values in these submodels. Consequently, the reasonable constants in the submodels can be determined by comparing the calculated values of ignition delay, mean velocity, gas pressure and gas temperature with the measured ones.

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