Experimental study has been conducted to examine the heat transfer characteristics of fuel and water emulsion. Water in fuel emulsion with alcohol additives were prepared with base fuel, distilled water and regent grade of alcohol with small amount of surfactant. Heat transfer experiments were carried out on an electrically heated horizontal thin Pt wire. It is concluded that the heat transfer coefficient decrease with an increase of ethanol contents. This tends to be similar to the case of methanol additive in the emulsions. Effects on heat transfer of ambient emulsion temperature was also revealed.

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Improvement of the oil recovery rate is of great importance for carbon dioxide enhanced oil recovery (CO_2EOR). Mixing phenomena of oil/CO_2 under high pressure is one of the most fundamental mechanisms in CO_2EOR, however, the mixing process is still not completely understood because of complexity of swelling, reduction of kinetics and interface tension. In this study, fundamental mixing process of decane/CO_2 was observed under high pressure. As the result, different mixing behavior was observed by changing concentration gradient of CO_2 in oil phase with a stirrer. Raman spectra which indicated dissolution process of oil in CO_2 phase were also obtained.

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Simultaneous measurement of temperature and velocty has been carried out for natural convective oscillatory flow in a forizontal concentric annulus by using Two-color LIF and PIV. The outer and inner diameter ratio of the annulus was 2.0 and the Rayleigh number was 1.0×10^<-7>. A counter-rotating eddy comes into existance near the oscillatory buoyant plume and the heat transport mechanism has been discussed based on the characteristics of temperature and velocity fields.

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Inflow phenomenon in near field of buoyant jet issuing into still surrounding of water is studied experimentally and numerically. The experimental visualization is carried out using 3D LIF technique, which visualizes the three-dimensional inflow phenomenon in the near field of buoyant jet. It is found from the experiment that the inflow phenomenon starts in the near field of buoyant jet when the Froude number becomes lower than the critical inflow condition. In order to understand the physics of inflow phenomenon, numerical simulation is carried out. The numerical result reproduces well the critical inflow condition observed by experiment. With further decrease in Froude and Reynolds numbers, the vigorous fluid mixing is found in the experiment, which is due to the appearance of turbulence in the jet caused by the inflow phenomenon.

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Heat transfer enhancement for a laminar natural-convection boundary layer along a vertical flat plate with short flat plates standing in line at fixed intervals (split heat transfer promoter) has been numerically analyzed to comprehend the mechanism originating the increase in heat transfer rates. The calculated results shows that remarkable heat transfer enhancement is due to the synergetic effect of low temperature fluid flow detouring the inclined plates and the longitudinal vortexes generating at the edge faces of inclined plates. For the heated surface of 0.3 m height, the use of 7 column split heat transfer promoters conduces to an increase in average heat transfer rate of approximately 50 % compared with that without promoter.

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The present study proposes an estimation model for free convection heat transfer in a stably stratified layer, where a lot of free convection cells are formed and each cell contributes the total heat transfer. Since the over-all heat transfer coefficient can be estimated by the heat transfer coefficient of each small cell, the present study developed a correlation formula of free convection heat transfer coefficient in an enclosed chamber. The heat transfer coefficient was numerically analyzed for free convection in a rectangular cavity and the correlation formula was developed over a wide range of the aspect ratio Ar=0.1-20 and Rayleigh number Ra=10^3-10^7.

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The purpose of this study is to clarify effects of micro-bubble injection on the heat transfer enhancement of natural convection along a vertical heated plate. We use thermocouples for the temperature measurement. We also use an image processing technique for obtaining the diameter of bubbles. The working fluid used is tap water, and hydrogen bubbles generated by electrolysis of the water are used as the micro-bubbles. The temperature measurements show that for all regions, the heat transfer enhancement is caused by the micro-bubble injection and that the maximum heat transfer gain with micro-bubble injection is approximately 24 when the bubble mean diameter and the bubble flow rate are, respectively, 50 μm and 39 mm^3/s.

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Suspension is a fluid which is mixed with insoluble materials. The suspension's natural convection is a complicated phenomenon. The natural convection is affected by fluid temperature and particle concentration distribution, which is caused by particle sedimentation. However, the formation mechanism of the convection has not been clarified. In a previous study, the natural convection of suspension was observed in rectangular cell with a heated bottom wall and cooled side walls experimentally. In this study, the numerical analysis under the same condition was carried out. As a result, the formation and breaking of convection layers can be expressed. I was found that the boundary of convection layer is broken when the Rayleigh number of temperature at the boundary becomes larger than that of concentration.

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Concerning on hot wire type temperature and velocity measuring equipments, the effects of thermal properties change on forced convection heat transfer was examined precisely through the measurements of heat transfer ratio from thin metal wire heated in various heat ratio. The results of experiments show that the normalized heat transfer coefficients increases slightly with increase of flow temperature. These results indicate that the variations of thermal properties with large temperature deference alternate the forced convection heat transfer ratio intricately.

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In order to clarify the effects of thermal properties change on forced convection heat transfer, the heat transfer ration from thin plate settled in parallel to the cross flow and heated in various heat ratio was examined by precise experiments and numerical analysis. The experimental results show that the normalized heat transfer coefficients increases slightly with increase of flow temperature. The numerical analysis indicate similar tendency. These consistent results suggests that the effects of thermal property changes with large temperature deference should be considered on forced convection heat transfer ratio.

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Spatio-temporal characteristic of heat transfer accompanied by the flow separation and reattachment was investigated by using a high-speed infrared thermograph that recorded the temperature fluctuation on a heated thin-foil. In this study, the heat transfer behind a backward-facing step, a forward-facing step, and a blunt plate were investigated. In each configuration, the heat transfer in the flow reattaching region had spot-like characteristics, which spread with time and overlapped with others to form a complex feature in terms of spatio-temporal characteristics of the heat transfer. The mean Nusselt number distribution behind the reattaching region was approximately proportional to 2/3 power of Reynolds number, as indicated in the previous researches. The instantaneous heat transfer distribution had a spanwise periodicity in the flow reattaching region, the wavelength of which seems strongly dependent on the step height.

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This paper presents observations and investigations of the turbulent heat-transfer structures in boundary layers with separation and reattachment by means of direct numerical simulation (DNS). Flow separation and reattachment are caused by step or obstacle of the wall. Thus, in order to observe effects of shape of wall for the turbulent heat-transfer in boundary layer, various heights and widths of 2D hill and various heights of forward-facing step are arranged in DNS. Also, the wall thermal condition is set by constant wall temperature in all cases. The results of DNS reveal the turbulent statistics, characteristics and structures of turbulent heat-transfer in boundary layers with with separation and reattachment, i.e., the detailed phenomena of turbulent heat-transfer in boundary layer with separation and reattachment are obviously demonstrated.

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Direct numerical simulation was performed for the coexistent convection in a channel affected by the heat radiation. Four kinds of numerical condition were targeted by changing the Grashof number, Gr, and the optical thickness, T; the pure forced convection (Gr=0, τ=0), only buoyancy (Gr/10^6=1.3, τ=0) and the buoyancy with radiation (Gr/10^6=1.3, τ=0.01), (Gr/10^6=1.3, τ=0.1). According to the numerical result, buoyancy effects created the large-scale organized vortex flow all over the channel, which enhanced dramatically heat transfer. The effect of the radiation weakens the large-scale organized vortex and reduces the heat transfer by the buoyancy.

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Even in these days, the better the efficiencies of gas turbines are required to be, the higher the temperature of turbine inlet gas becomes. Turbine vanes and blades exposed to hot gas must be cooled, therefore film cooling is widely applied to the recent gas turbines because of its high cooling effectiveness. However the prediction methodology of the film cooling effectiveness has not been established well until now. In this study, the film cooling flow on the flat plate from cylindrical holes which is most typical and basic test case is numerically simulated by LES. Blowing Ratio is set to 0.5 and 1.0, Density Ratio is set to 2.0, which are generally equivalent to those in actual engines. The results of the simulations show that LES calculation has good prediction capability for film cooling flows.

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For the Large Eddy Simulation (LES) of film cooling flows with multiple coolant jets, a film-hole model based on a RFG (Random Flow Generation) technique was proposed to simulate turbulent fluctuating flows at the exit plane of film cooling hole as a boundary model. The proposed film-hole model for LES was validated by the comparison of predicted center-line film effectiveness with a known experimental result. In addition, the present LES was confirmed to predict correctly the effect of a swirling motion in a coolant jet on the film cooling effectiveness, by comparing it with experimental results. The spatial structure of the film cooling effectiveness at a cross section was also predicted well.

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Adding droplets to air is used to improve the cooling efficiency for warm surfaces. When the surfaces are horizontal, the liquid film is generated by the droplets. If the heat flux is low, the film becomes a thermal resistance. In order to reduce this thermal resistance, we have created a new functional surface, which consists of hydrophilic bare part and super-hydrophilic part covered with nano-pin structure. Our experimental results show that the water droplet deposited onto the plate move promptly from the edge of the hydrophilic part to the super-hydrophilic part. Furthermore, the local, instantaneous heat transfer coefficient in the case of the new surface is found to be higher than that of hydrophilic surface.

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We studied experimentally the impingement heat transfer from the circular orifice jet with nano-sized water mists. When the nano-sized water mists with initial velocity was added, the jet was bent and the location of the maximum pressure coefficient and Nusselt number on the target plate was shift from the center of the orifice. And the iso-Nusselt number profile on the target plate became the elliptic shape. However, the enhancement of the heat transfer was not observed, because the local temperature of the free jet corresponding to the place of the target plate was not varied from that without mists.

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For the developments and designs of the supercritical water cooled reactor (SCWR) which is an advanced nuclear reactor, it is necessary to accurately estimate heat transfer to supercritical pressure water in the superheated vapor region. In this study, a numerical analysis is carried out using the commercial CFD code STAR-CD, and compared with the experimental data obtained under the superheated vapor region. HCFC22 is used as a test fluid, which flows upward in a uniformly heated vertical circular tube. The k-co model is selected as the turbulence model and the effect of property variation on heat transfer is investigated.

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