In this paper, characteristics of fluid flow and heat transfer of a drag-reducing dilute cationic surfactant solution in a channel and a tube are investigated to realize a highly efficient thermal transportation system. The addition of small amount of surfactant to water can reduce turbulent factional drag considerably, but many investigations, which are of full drag-reducing flow without disturbance, have showed that the heat transfer is reduced simultaneously. In order to recover the reduced heat transfer, the effect of some turbulent promoters and a row of delta winglets that generates the longitudinal vortices were tested in a two-dimensional channel. Further, the examination on the relation on the relation between heat transport and momentum one was carried out; it was found that the critical velocity corresponding to the critical Reynolds number at which the drag-reduction effect reaches a maximum value only depends on the concentration of the surfactant solution.

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We carry out an experiment for the simultaneous visualization of flowing polymer lumps, coherent structure and near wall temperature fluctuation in turbulent water duct flow by using the fluorescence color particles, the hydrogen bubbles and planer laser-induced fluorescence (PLIF) technique, respectively. The images of the color particles, the bubbles and the fluorescence dye have been captured by two video cameras. It is found that the polymer lumps attenuate the turbulent heat transfer associated with the outward motion of warm fluid due to the quasi-streamwise vortices.

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Drag reduction with CTAC surfactant solution will be one of the promising candidates to reduce pumping energy and heat loss in far-district heating/cooling energy transport systems. The investigation on the heat transfer performance of an inclined impinging jet in the drag-reducing flow was performed with the heat transfer and flow velocity measurements. The results obtained in the present study reveals the jet impingement will be one of the effective methods to control the local enhancement of the heat transfer.

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Heat transfer characteristics of a dilute surfactant/water solution in a two dimensional channel has been experimentally investigated. It is known that surfactant solutions do show a large sensitivity of their drag reduction and heat transfer reduction effectiveness on temperature. In the present experiment, profiles of mean temperature and that of fluctuation intensity were measured relating heat transfer coefficient in the thermal boundary layer. It was found that high diffusivity layer exists near the wall in the drag reducing thermal boundary layer. The relation with high diffusivity layer and heat transfer coefficient is discussed.

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The present experiment study is conducted to examine the near field characteristics of the axisymmetric jet discharged from circular pipe for a dilute drag-reducing surfactant solution (Ethoquad O/12). The temperature effect on the jet behavior is studied for a fixed Reynolds number of 10000. It is found that the turbulence suppression effect reduces with the development of jet and strongly depends on the temperature.

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Brine flow characteristics with drag reduction surfactant are important to reduce energy consumption in a pipeline system. Oleyldihydroxyetyl Arhine Oxide (ODEAO) reported as an effective drag reduction surfactant additive was add to Ethylene Glycol (EG) solution at 40wt% as the brine in the present study. The friction factor and heat transfer coefficient of the Ethylene' Glycol solution with ODEAO were measured as a function of various solution temperatures. It was found that the solution temperature has exerted an influence on the flow drag and heat transfer reduction rate of the EG solution with the ODEAO surfactant.

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In this paper, we suggest a novel technique of heat taransfer augmentation in a complex duct, using a viscoelasticity of fluid. The heat transfer measurements and flow visualization experiments have been performed for a periodically contracted/expanded duct flow of surfactant/water viscoelastic fluid system. From the results, the recirculating regions behind backward-facing steps are observed to be markedly depressed when viscoelasticity is added to the fluid by surfactant addives. This causes successful heat transfer augmentation in a cavity of the expanded region, especially just behind a backward facing step, compared with the results of water flow. From this, the present method for heat transfer augmentation is found to be at least effective on heat transfer augmentation from bottom walls of a cavity in a periodically contracted/expanded duct flow.

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It is known that drag reducing additive reduce turburent friction drag and heat transfer in tube flow simultaneously. Then, the reducing chracteristics of drag and heat transfer of surfactant(Ethoquard 0/12) solution flow in the finned-tube heat exchanger (pipe di. 9.3mm) for air-conditioning were measured in the experimental room controlled temperature and humidity, before field test. The following results were obtained. (1)As cooling, it was not showed the reducing chracteristics of drag and heat transfer. Conversely, it was showed the increasing chracteristics of drag. (2)As heating, the reducing chracteristics of drag and heat transfer depended on the type of heat exchanger.

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This paper reports how heat transfer can be augmented by inserting a micelle squeezer at the inlet of the turbulent pipe flow drag-reduced by surfactant additives. The micelle squeezer gives very high shear to the flow and the rod-like micelles formed with surfactant molecules, which remarkably reduce both drag force of the flow and heat transfer, are broken by the high flow shear at the flow inlet. From this, the drag force is recovered in the very limited region below the micelle squeezer, but also heat transfer is recovered in the enough regions required for exchanging heat. This strategy can be applied for heat exchangers, which occupy the small part of district cooling flow system.

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The secondary flow of the second kind exists in turbulent flow through a straight duct with a non-circular cross section. This secondary flow driven by gradients of the Reynolds stresses makes the flow field complex very much, although its velocity is at most 1 or 2% of the primary flow velocity. Therefore heat transfer in such a duct are also influenced by this secondary flow. In this paper various characteristics on temperature field measured in a square duct with one rib-roughened wall are compared with those in a smooth-walled duct. The distributions of the turbulent Prandtl number obtained from those of the turbulent heat flux are also shown.

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Calculations have been performed for fully developed turbulent flow and heat transfer in a square duct with one roughened wall. This paper focuses on the application of three algebraic models of the turbulent heat flux transport equation to predict turbulent heat flux component behavior. The pressure-temperature gradient term is simulated by means of three models: one a composite based on the "slow" and "rapid" interaction models proposed by Lumley and Launder, respectively, and another model proposed by Shih and Lumley and the other model proposed by Craft and Launder. These three models lead to predict mean temperature distributions in the duct cross plane that are in relatively good agreement with experimentally measured distributions. Calculated turbulent heat flux component distributions in the cross plane show that all models predict experimentally observed features in the flow, without the Craft and Launder model providing the best overall accuracy.

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Experimental study has been conducted on flow and local heat/mass transfer characteristics in rectangular cross-sectioned serpentine channels with a sharp turn having an inclined partition wall. Detailed distributions of local Sherwood numbers are presented that are obtained on all the walls of the channels by the naphthalene sublimation method, and the influence of the inclination angle of the partition wall on the local heat/mass transfer are discussed. Then, the flow characteristics in the channels such as flow separation and reattachment around the turn section are examined based on the mean flow vectors obtained in the planes parallel to the long-side wall using the PIV.

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A passive containment cooling system (PCCS) is under planning to use in a next-generation-type BWR for long-term cooling by condensing steam using horizontal heat exchangers. Heat transfer behavior in a secondary water pool is one of important phenomena governing heat removal performance of the PCCS. Boiling and condensation can be supposed under high heat flux regions and the characteristics of the two-phase natural circulation should be evaluated. This study investigated effects of pool size on the characteristics by multi-dimensional two-fluid model code ACE-3D. It was found from the analyses that the pool size gives no significant influences for the characteristics in tube bundle under local-boiling mode.

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For serrated fin tubes, the analytical solution, the approximate equation, and the correction factor of fin efficiency are reported by Hashizume et. al. However, they are based on the data using staggered tube bundles. Therefore, this paper studied whether it can be applicable for inline tube bundles and shallow bundles. As a result, it was found the followings; Regardless of the fin tube in the rear, the fin efficiency of the 1st row is possible to calculate with the accuracy of ±5% by the method for staggered tube bundles. Regardless of the fin tube in the front, the fin efficiency of after the 2nd row became possible to calculate with the accuracy of ±5% by the method that was proposed there. And also these became clear with that these are valid both plain and serrated fin tubes.

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In order to grasp the heat transfer characteristics on the bottom wall downstream of a 3-D backward-facing step, heat transfer coefficient was measured by making use of a thermo sensitive liquid crystal sheet. Reynolds numbers based on the step height were varied from 1000 to 10000 in 30 steps keeping expansion ratio and aspect ratio constant. Obtained local Nusselt number showed quite unique distribution and it suggested the strong three dimensionality of flow and thermal structures. Peak Nusselt number appears near the sidewall for every Reynolds number, namely it does not vary in the spanwise direction. However, its streamwise location moves upstream toward the step as Reynolds number increases from 1000 to 2300, and they again moves downstream as Reynolds number increases from 3000 to 10000.

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A two-dimensional jet-impinged on a target plate vertically placed for the jet axis. The target plate was mounted at a distance from the jet exit of 3 times the jet slot width. A circular cylinder was installed on the jet central plane between the target plate and the jet exit. Characteristics of flow field and heat transfer in changing the diameters and the locations of the circular cylinder were examined. The maximum local Nusselt number attained around the stagnation point was augmented by about 76% and the average Nusselt number increased by about 30% compared to the ones for normal impinging jet without the insertion of a cylinder.

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Numerical simulation on the flow and heat transfer of sinusoidal wavy channel was conducted to investigate the effect of phase-difference between upper and lower wall. The difference was varied from 0 to π. The phase difference induces the dynamic change of flow and heat transfer characteristics. The critical Reynolds number at which flow changes its state from steady to unsteady was found to be lower for a larger phase difference. The heat transfer performance evaluation at constant pumping power base showed that the largest phase difference case(π) was the most preferable among five cases studied.

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Direct numerical simulation was performed for turbulent heat transfer from wavy surfaces. Treated surface geometry was symmetric sine curve and asymmetric curve, the latter of which was generated by the coordinate transformation of the symmetric sine. Following conclusions are obtained: (1) There is similar trend of heat transfer between wavy surfaces and sand roughness when equivalent sand roughness is used for data arrangement. (2) Forward-bent deformation of wavy surface can enhance heat transfer from the wall.

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Flow visualization and heat transfer experiment were carried out for the three different variations of ribs mounted on the channel duct. In all cases, strong three-dimensional flow thermal structures due to the effect of the side walls and rib gaps were observed. Especially for the ribs with gaps, flow field was characterized by high seed gap flow and tornado like vertical vortices downstream the rib. Such flow structures were found to be effective to recover heat transfer deterioration occurring just behind the full-span rib presently used in the blade cooling system. It was also found that a rib having a gap in the middle of the duct effectively increases heat transfer on the side wall surface.

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The effect of a sphere on the local heat transfer to a turbulent boundary layer was examined. The diameters of the sphere used in this experiment were D = 12, 20, 30, 40, 50, 60, 70, and 80 mm. The boundary layer thicknesses where the sphere was placed were 60, 70, and 75 mm, corresponding to main flow velocity of U = 7.5, 10.0, and 12.0 m/s, respectively. The freestream turbulence level was less than 0.5%. The local heat transfer coefficient, mean velocity and turbulent intensity were measured. Surface temperature and surface flow pictures were obtained. The results showed (1) The local heat transfer coefficient distribution has a peak at 1.5D downstream of the sphere. (2) The peak value has a relation with Re number based on the sphere diameter. (3) Flow periodicity was not found behind the sphere on the plate.

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This study tries to estimate flow behavior around a semi-cylindrical turbulence promoter in parallel plates using a low-Reynolds-number one-equation turbulence model proposed by Pei et al. (1999). To take account the effect of multiple walls on the flow field, an effective distance developed by Aragaki et al. (1999) is adopted to modify the normal distance from wall. The equations are solved using finite element method and results are compared with the wall shear stresses measured by using the electrochemical method in the same conditions.

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In this paper, We measured the details of three-direction velocity components, U,V,W, fluctuating velocity u,v,w and turbulent shear stress -uv, -wv by means of the inclined hot-wire probe. The object of this paper is to examine the influence of these flow structure on heat transfer enhancement in a pipe. Moreover, shear stresses on the wall and local heat transfer coefficients were measured, and the non-analogy phenomena between the shear stresses and local heat transfer coefficients were discussed

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A numerical study was conducted to investigate the heat transfer performance when a wing type vortex generator is installed in the laminar and turbulent channel flows. The turbulence induced by the wing enhances the turbulent heat transfer more effectively than the Reynolds stress. This is caused by the fact that the apparent eddy diffusivity of momentum transfer is remarkably reduced in the back flow of wing. In that region, a strong inward flow exists because of the longitudinal vortices induced by the wing and of the flow from the hall on the bottom wall of upper channel. The Reynolds stress is suppressed noticeably since the fluid with small momentum is transferred to the wall by the inward flow, which results in the effective heat transfer enhancement with small turbulent drag.

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Flows in porous media can exhibit steady, time-dependent, chaotic and turbulent behaviors, despite the highly dissipative effects of viscosity and thermal conductivity. The phenomena intrinsic to porous media are brought about by the presence of porous matrix, basically through the short distance interaction of fluid with the adjacent inner walls, which exist everywhere in porous media. To describe such microscopic effects in porous media, proper averaging techniques are needed, taking characteristic length scales into consideration. Particularly, a discussion is made on the nature of Forchheimer resistance in close relevance with turbulent dissipation in porous media, concentrating on the roles of large-scale and small-scale vortices. Discussions are also made on recent turbulence models. It is hoped that future studies reexamine the macroscopic governing equations, considering microscopic and unsteady nature of the chaotic and turbulent behaviors.

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In this paper, a novel technique for evaluating the mixing situation of particles in a fluidized bed is proposed by using a concept of the apparent deffusion coefficient of the fluidized particles. Mixing motion of the particles was visualized in an experimental fluidized bed; the bed contained spherical particles covered with a photochromic dye, and the fluidized particles in a small portion were "marked" with an UV laser irradiation. In order to evaluate the apparent diffusion coefficient, the visualized increase with increasing the superficial gas velocity. The authors therefore concluded that the technique proposed in this paper is feasible for evaluation the mixing situation of the fluidized particles.

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In this paper, the drying of layered packed beds due to convective heating has been investigated theoretically and experimentally. An one-dimensional drying model in layered packed beds has been presented, accounting for the water transport, the diffusion of water vapor and the latent heat transfer due to vaporization. The effect of the structure of packed beds affecting the mass of drying was clarified in detail. It was found that the mass of drying strongly depends on the water saturation at the boundary surface on convective heating side. The predicted results were in good agreement with experimental results using packed beds composed of glass beads.

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Effect of Reynolds number on the flow characteristics in a simply packed bed of spheres is measured by using an MRI technique. The flow in the packed bed tends to penetrate through the center of void space without the velocity change along the stream with the increase in the Reynolds number. Three-dimensional circulation is observed in the tail area between the spheres.

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In order to develop the simple network model of interstitial flow trough a packed bed, three-dimensional void images measured by magnetic resonance imaging (MRI) were divided into polyhedrons as fluid pass. By assuming that flow resistance through one plane of a polyhedron is the inverse square of its plane area, closed circuits of flow resistances in the packed bed were constructed. By solving the matrix of circuits, flow rate through each polyhedron was calculated and compared with the velocity map measured by MRI.

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PIV measurements have been conducted for flows through a two-dimensional porous medium of high porosity, namely, a spatially periodic array of square rods. A series of instantaneous velocity vector plots are presented to investigate the transition from laminar to turbulence in the porous medium. The corresponding turbulence energy spectra at a selected point are also presented. It has been found that the flow remains laminar within the Reynolds number range studied, namely, 150 to 1500.

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The environmental load of co-generation systems (CGS) is evaluated from the LCA-ESS method proposed by the authors (LCA: Life Cycle assessment, ESS: Eco-load Standardization Scheme). This ESS software has easy operation and high flexibility for different kinds of CGS. (Eco-load standardization Scheme) In the impact evaluation, three kinds of fuels of natural gas, heavy oil and coal and two types systems of gas turbine and gas engine are applied, and compared. Computer software minimizing the environmental load is built by using a combined simplex and branch-bound technique. It enables to easily evaluate from the input demand data to optimize the eco-load of CGS in a very short time. As the results, the LCA-ESS method is found to be useful to evaluate the environmental load and eco-operation scheme.

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Reason of reducinng boiler-efficiency on low-load was analyzed, it became obvious thatit is mainly radiationloss. Then, the best way to be kept high efficiency on low-load is buildup of insulation. But, in case of it is difficult, high efficiency on low-load can be gained by equipping additional cooling-surfaces, for exanple, economizer or air-preheater. If fan is not replaced in this case, available load is limited. This report explaines these calculation.

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An eddy correlation method is usually used to measure latent and sensible heat fluxes above urban surfaces. This method needs to simultaneously measure the fluctuation of specific humidity, air temperature and vertical wind speed about lOHz frequency at the short path length with high accuracy. In the present study, a near-infrared hygrometer with two open optical paths is newly developed in order to measure the fluctuation of specific humidity in the field. The results of indoor experiments indicate the accuracy under 0.2g/kg. The results of field measurements show the necessity of the simultaneous measurement of solar radiation and specific humidity.

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Since the wind-power energy is proportional to wind velocity cubed, it is crucial to predict a correct profile of wind in selecting the best site for a wind-power plant. The effects of the ground are often neglected owing to the very large length scale of the real environment. However, the complex terrain affects a profile of wind near the ground. Therefore, we have to consider the ground effects to obtain an exact profile of wind near the ground. In this study, to evaluate the performance of a low-Reynolds-number type turbulence model in an atmospheric boundary layer, we calculated a stable boundary layer flow with a roughness surface. Also, we proposed a turbulence model including the effects of the roughness and the buoyancy. Moreover, to assess the prediction of the turbulence model on a complex terrain, we carried out a simulation of a forward-facing step flow. In this case, it is well known that the turbulence energy is overpredicted by the k-ε model at the stagnation point; thus, we have improved the model introducing the time scale based on the velocity gradient parameter. The proposed model indicates good agreement with the experimental data.

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A direct numerical simulation (DNS) is performed on the turbulent Ekman boundary layer over two-dimensional wavy terrain. In the upper part of the Ekman boundary layer, the geostrophic wind is driven by the balance between the atmospheric pressure gradient and the Coriolis force. The hills are arranged vertically to the direction of the geostrophic wind. The re-circulation vortex occurs in the valley between the hills. The flow in the direction parallel to the hill is dominant in the valley. The thickness of the Ekman boundary layer is significantly increased compared with the flow on the flat ground owing to the enhanced turbulence induced by the wavy terrain.

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We have performed the direct numerical simulations (DNS) of a homogeneous shear flow to investigate how the Coriolis term affects the vertically collapsed turbulent structure under strong stable stratification. Rogallo method, i.e., a spectral method, is used for simulating a homogeneous shear flow under system rotation around the x_3 axis. Both the mean temperature gradient and the gravitational acceleration g are simultaneously imposed in the x_3 direction to include the effects of both buoyancy and rotation. The isosurfaces of the vertical vorticities become the scattered pancake-shaped vortex patch, strongly indicating the collapse of turbulence. With an increase in the rotation parameter, the effect of the wind shear becomes more intensive and the pancake structures are elongated in the streamwise direction.

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The direct numerical simulations (DNSs) of neutrally and stably stratified turbulent Ekman layer over a smooth surface are performed using the Boussinesq approximation to account for the buoyancy effect The Reynolds number based on the geostrophic wind, the Ekman layer depth and the kinematic viscosity is 410, which is almost equal to that of Coleman et al (1990) The Grashof number is set to be Gr=0, 3.15×10^6, 6.30×10^6 and 3.15×10^7. A temperature field is so introduced that its mean profile is unchanged with time advancement. As the result, statistical quantities are obtained for both velocity and temperature fields The effects of stable stratification upon the direction of the mean velocity, the Reynolds stress and the turbulent heat flux are discussed based on the obtained DNS data.

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In this study, Direct Numerical Simulation (DNS) of wind-driven turbulent flow with heat transfer was conducted by the direct numerical solution procedure (MARS method) for a coupled gas-liquid flow. The Reynolds number is about 3300 based on the gas layer height and the free stream velocity and the computational grids number is 256×164×256 in streamwise, vertical and spanwise directions, respectively. As the results, interactions between free surface behaviors such as Microscale breaking and turbulent structures, effects of the grid dependency on the near free surface turbulent structures and scalar transfer across the free surface were revealed and discussed.

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Experimental study has been performed on evaporation of water droplet on a TiO_2-coated copper surface. The surface exhibits extremely high affinity for water by exposing the surface to ultraviolet ray and the contact angle decreases nearly to zero. Using this nature, we can change contact angle only without changing other thermal properties. The evaporation time was measured for single water droplet of four different diameters. Especially, the effect of contact angle on wetting limit temperature has been examined. It is found that wetting limit temperature increases as the contact angle decreases.

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Experiments were conducted to study the effect of submicron-scale roughness on the pool boiling of FC-72 on 10×10 mm^2 silicon chips with and without rectangular micro-pin-fins of 50×50×60μm^3. The surface roughness was produced on a smooth silicon chip by : (1) chemical vapor deposition (CVD) of SiO_2, and (2) combination of sputtering of SiO_2 and wet etching of the SiO_2 film. The latter technique was also applied to a silicon chip with micro-pin-fins. While the two kinds of roughness showed different heat transfer characteristics in the nucleate boiling region, the critical heat flux q_<CHF> was fairly close to each other. The value of q_<CHF> was 1.3 to 1.5 times as large as that for a smooth chip. The highest value of q_<CHF> (1.8 to 2.3 times as large as the smooth chip value) was obtained by a chip with etched roughness on the micro-pin-finned surface.

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The purpose of this research is to clarify the miniaturization boiling phenomenon, which intensely scatters with large number of minute liquids particles from the droplet surface to the atmosphere, when the droplet collided on the heating transparent solid surface. Especially, the temperature fall pattern in the solid heating surface at the impact was visualized by the holographic interferometry. It was proven that the temperature fall was not so influenced by the material thinly spattered on the surface. As a transparent solid surface with different thermal property, quartz and quartz with chromium coating were used in this study.

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The concentration dependence of pool nucleate boiling heat transfer coefficients for HFC-134a and Alkylbenzene oil systems has experimentally been investigated. A horizontal Pt wire(φ 0.1 mm) is used. Heat transfer coefficients for HFC-134a/ Alkylbenzene oil systems have been obtained at temperatures of 282.15, 292.15 and 302.15 K for oil concentrations from 0 to 8 mass%. The range of heat flux is between 0.02 and 300 kW・m^<-2>. The present results show that the heat transfer coefficient decreases by about 50% at the oil concentration of 0.5 mass%. At the oil concentrations higher than 2 mass%, the heat transfer coefficients keep constant in spite ofthe increase in oil concentration.

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Experiments of flow boiling of water at 0.11MPa were conducted in a vertical narrow annulus for the inlet subcooling of 10 to 50 K and mass velocity of 100 to 750 kg/m^2s. Measured boiling curves show existence of enhancement regions of heat transfer. Visual observation identified flow patterns peculiar to narrow space. Isolated bubbles generated at lower heat fluxes are deformed and spread rapidly over the whole narrow annulus. At higher heat fluxes, the narrow space are filled with vapor mass and dry patches are seen on the heating tube Flow patterns are different from those in conventional large tubes

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This study is focused on the development of a two-fluid model gas-liquid two-phase flow simulation code (PORTHOS-MHI). This code was developed to analyze thermal-hydraulic behaviors within a steam generator (SG) tube bundle of a Pressurized Water Reactor (PWR) nuclear power plant. The developed code was verified using the interfacial-velocity and the void-fraction distributions obtained from a tube-bundle experiment of a two-dimensionally full-scale model SG with R-123 as secondary working fluid. Good agreements between the prediction of PORTHOS-MHI and the experimental results of low flow rate (30% full load) conditions were obtained.

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