Electromagnetic field and its energy density around a nano-sized gap between two pillar array structured surfaces were numerically calculated using a three-dimensional Finite Difference Time Domain (FDTD) method. The simulation results show that a normalized spectral radiation flux became significantly higher and the wavelength at the peak of normalized radiation flux was shifted from a short regime to a long regime with decreasing pillar width. In addition, the results also show that the near-field radiation transfer was limited and concentrated in a narrow area in the nano-sized gap with decreasing pillar width. As a result, the near-field radiation transfer was enhanced by decreasing width of pillar.

Spectral Control of near-field radiation transfer by Metal-Insulator-Metal (MIM) structured emitter made of Au for a thermophotovoltaic (TPV) power generation system is studied using a Finite Difference Time Domain (FDTD) method. As a result, the radiation flux was enhanced within a wavelength range from visible to a near infrared (up to about 2 microns) compared with the case of parallel plane configuration due to the electric field in the narrow channel between metal islands made of Au.

In the present study, we numerically demonstrate wavelength-selective thermal radiation emitter made of graphene-covered Ag grating and it filled with silicon. Underlying physical mechanism is clarified by rigorous coupled-wave analysis. We find that the emission peaks associated with magnetic polariton (MP), whose resonance wavelength can be dynamically tuned by varying graphene chemical potential. This study could facilitate the new tunable thermal radiation sources in the infrared region.

We investigated the radiation properties of a plasmonic-photonic microstructure using micro-particles. This diameters of the micro-particles are 5 mm. We measured and numerically calculated spectral normal absorptance of it. From measurement result and numerical calculation result shows absorptance peak at about 5 mm. we investigated the electric field distribution of the absorption peak by numerical calculation. From the calculation result of the electric field distribution, we confirmed that electric field is generated on the surface of gold and electric field is propagated along the periodic structure. Therefore absorption peak at about 5 mm is considered to be due to the periodic structure.

For precise thermal control in satellites under varying internal heat dissipation and thermal boundary condition, we have proposed a MEMS radiator enhanced by near-field effect. Here, we analyse the near-field effect in multi-layered structure in order to estimate the effect of the dielectric layer on the device performance. It is shown that the ON/OFF heat flux ratio of 4.1 can be achieved with a 50 nm-thick SiO₂ layer sandwiched between the electrodes. Also, it is experimentally shown that, with our prototype radiator, 2.4 times enhancement in the radiation heat flux has been obtained.

In this study, we tried to measure spectral hemispherical transmittance of piling quartz glass plates with double-layer anti-reflection coatings in order to verify the spectral control performance for diffuse irradiation. In the wavelength longer than 2.1μm, the measured spectral transmittance was consistent with numerical simulation result based on one-dimensional model. Meanwhile, the experimental value was less than the numerical one especially in the wavelength range from 1.5 to 2μm. In order to reduce this difference, numerical simulation included multiple reflections at the surface of mirror within wave guide was effective.

We performed direct numerical simulations of a spectral method of a plane Poiseuille flow under stable stratification. The friction Reynolds number is Re_τ = u_τδ/ν = 1000 and Prandtl number is Pr = ν/α = 0.71 , where u_τ , δ , ν , and α are friction velocity, the channel half width, the kinetic viscosity and thermal diffusivity, respectively. The Grashof number was systematically increased. From the calculation results, we could observe the attenuation of turbulent. In the channel center, the mean velocity was increased because of the attenuation of large scale turbulent by stable stratification.

The objective of this study is to investigate and observe characteristics of heat transfer phenomena in a spatially-developing wall jet turbulent flow by means of direct numerical simulation, where the wall is heated from midstream of field by an iso-thermal or an iso-heat flux boundary conditions, i.e., an entrance region of thermal field is formed. In the velocity field, the maximum mean velocity in the streamwise direction decreases in the downstream region, and Reynolds shear stress in the outer region remarkably increases in comparison with that in the inner region. As for the thermal field, distributions of mean temperature and Nusselt number in the entrance region of thermal field are clearly shown by DNS, in which it is clearly observed that the thermal boundary layer of the iso-thermal wall condition rapidly develops as compared with that of the iso-heat flux wall condition. Developments of wall-normal turbulent heat fluxes in the entrance region of thermal field are also revealed.

Direct numerical simulations of a spectral method were performed in order to study turbulent structure and heat transfer in Couette flows at transitional region with/without stable system rotation in spanwise direction. The Prandtl number is 0.71 to assume air. Our objectives in the study were turbulent stripes observed at low Reynolds number without the system rotation and at high Reynolds number with the system rotation. We confirmed that the thermal fields well corresponded to the velocity fields. Appearance of the stripe makes the turbulent Prandtl number lower. As the turbulent region enhances friction and heat transfer, the temporal and spatial oscillations were occurred.

In this study, we evaluate the boiling and evaporation heat transfer performance of the uni-directional porous media that have been proposed as a heat removal device in the high heat flux environment. Uni-directional porous media have effects such as direct supply of coolant to a heat transfer surface, promotion of evaporation and vapor discharge, high effective thermal conductivity and reduction of thermal contact resistance. As a result, we achieved a high heat removal performance of 10 MW/m² at the low flow rate and the low subcooling.

Experiments were carried out to investigate the characteristics of high-heat-flux heat removal using a porousmicro-channel under the condition of high liquid subcooling and high mass flux. The working fluid was water and the main experimental parameters were insertion of porous plate and channel size. It was shown that fluctuation of heating surface temperature and flow oscillation are mitigated if the porous plate is placed in the flow channel. Another finding was that the sound production in the flow channel under the high heat flux condition is also mitigated in the porous-micro-channel. These results indicate that the porous-micro-channel is advantageous for the high-heat-flux heat removal from high-power-density devices.

This paper reports the characteristics of thermo-fluid behavior in a wick that is fine porous structure and the effect of wick’s wettability improvement on the heat transfer coefficient. In this study, visualization of liquid-vapor interface behavior on the surface of the wick with microscopic infrared thermography and microscope was conducted. 2 wicks were made by stainless steel (SS). The acid treatment with hydrochloric acid was processed to one wick in order to improve the wettability. Contact angle changed from 10.7° to 0 ° after acidizing. As results, heat transfer coefficient of the wick with acid treatment became higher at 5.0~5.5W/cm². The reason of this trend is discussed based on the observation results.

Recent advances in mathematical modeling of heat and fluid flow in porous media were discussed starting from an introduction of volume averaging theory and leading to various engineering applications. Mathematical interpretations of tortuosity, thermal dispersion and interstitial heat transfer are provided with their models based on solvable volume averaged quantities. A useful concept “effective porosity” was introduced to account for the tortuosity. Moreover, an inverse relationship between the interstitial heat transfer coefficient and thermal dispersion coefficient was explained, which enables us to estimate the thermal dispersion simply by measuring the interstitial heat transfer using a single blow method. Engineering applications based on the local space sharing concept will be discussed ranging from bioheat transfer to ion transport through a membrane.

Large eddy simulation (LES) of turbulent heat transfer in isothermal porous media is performed by the lattice Boltzmann method (LBM) to discuss on modeling unknown terms of the double averaged energy equation. In this study, the regularized D3Q19 SRT model is applied to the thermal fields whilst the D3Q27 MRT model is applied to the flow fields. Using the LES data, a priori tests are carried out and it is confirmed that the sum of the volume averaged turbulent and dispersion heat fluxes can be reasonably modeled by gradient diffusion models.

Substantial heat transfer enhancement is possible using a passage filled with a nanofluid saturated metal foam, because of its high specific surface area, high thermal conductivity and comparatively low pressure drop. In addition to the Brownian diffusion and thermophoresis associated with nanofluids, one must fully understand both thermal dispersion and particle mechanical dispersion, so as to elucidate their combined effects on the heat transfer enhancement mechanism. Microscopic numerical calculations were conducted using a numerical model describing a structural unit of a passage filled with nanofluid saturated metal foam. The results were integrated over a local control volume, to evaluate the mechanical dispersion terms, purely from the theoretical basis. The present study reveals that the effect of the particle volume fraction on the thermal dispersion correlation is only minor, so that the correlations obtained for the base fluid can be used universally. On the other hand, the nanoparticle mass flux is found rather sensitive to the interstitial heat transfer rate from the metal to nanofluid, since it increases with the interstitial heat transfer rate.

Understanding of natural convection of miscible two phases in a porous medium is of great importance to issues of geological storage of carbon dioxide (CCS). We consider fingering instabilities between two miscible fluids of saltwater and freshwater in a porous medium. Plastic resin particles were packed in a tube with the inter diameter of 70 mm. Development of the fingering due to instabilities and natural convection between freshwater and saltwater in porous media have been imaged by means of micro-focused X-ray computer tomography (CT). At early stages of convective mixing, ripples appear on the contour surface of the concentration of sodium iodine and grow to be fingers which extend vertically downwards with time. The dispersion strongly impacts on the reduction in the onset time as well as the enhanced mass transport. Finally, we discussed about the effect of the thickness of the initial diffusion layer on the structure of fingering.

In this study we used a phenolic resin substrate with a micro-pore size because of its high water permeability. We measured evaporation ratio for three cases (Pore diameters: 5, 25 micro-meter). A droplet is 5 micro-liter generated by a micro pipet. As a result, it became clear that the evaporation speed of the substrate with a pore size of 25 micro-meter was faster than the other cases. This is because the water permeability is low. We believe that this advantage of a phenolic resin substrate extend the range of application of the pool boiling for IC chip cooling.

In this study, I observed the behavior of fingering of immiscible two phase flow visualized three dimensional in porous media by utilizing an X-ray computer tomography (CT) scanner. I evaluated the behavior of the substituted interface by using the dimensionless capillary number (Ca). For the experiments, I observed crossover from capillary to viscous fingering for oil-water displacement in packed bed glass beads for logCa = -4.0 to logCa = -3.0. I discussed about characteristics of crossover from capillary to viscous fingering by using distribution of wetting phase saturation for the height.

Carbon dioxide flooding, which is one of enhanced oil recovery schemes, improves oil recovery due to the miscibility between supercritical carbon dioxide and oil. When a less viscous fluid displaces a more viscous one, however, viscous fingering reduces oil recovery. In this study, the there-dimensional development of viscous fingering in miscible two-phase flows in porous media is visualized using an X-ray CT scanner. Interaction among the fingers such as shielding, merging, and tip splitting is observed. Three-dimensionally involved structure of the fingers results in low sweep efficiency compared with two-dimensional viscous fingering.

The use of metal foams is one of the recent popular passive heat transfer enhancement methods due to their remarkable increase in effective thermal conductivity. In order to analyze heat and fluid flow in metal foams in the manner of volume averaged quantities, macroscopic transport parameters such as permeability, inertia and interfacial convective heat transfer coefficients should be well-known. In this study, determination of macroscopic transport parameters is done by using x-ray micro-tomography images. A metal foam with pore density of 20 PPI is considered in this study. The flow simulations are conducted for air flow at steady state and in laminar flow regime.

Microwave has been often used for nano-particle synthesis because rapid growth and mono-dispersed particle size are obtained. However, superheat behavior causes larger bubble size and disorders temperature distribution when higher power of microwave is irradiated. Accordingly, superheat must be prevented for stable operation of nano-particle process. In previous study, we found that bubble formation happened during particle formation at the same time when FeCl₃ aqueous solution is heated by microwave. According to the results through in-situ particle size measurement during the irradiation, superheat behavior occurred at the condition of the higher power and lower suspension density. In this study, ethylene glycol with lower electric constant was added to promote particle nucleation and to enlarge particle number density. Moreover, the solute is not dissolved in ethylene glycol as anti-solvent although ethylene glycol is dissolved in water. The results showed that bubble size during the irradiation and particle size after the irradiation became smaller by the ethylene glycol addition. As a result, operation by higher power became possible, and higher particle number density was obtained as synergy effect of anti-solvent effect and quick thermal response by microwave. Finally, addition of alcohol became good method for nano-particle formation process to prevent superheat behavior during higher power irradiation.

We conducted measurements on unidirectional freezing and circular dichroism for preheated solution and unheated solution of a polypeptide based on winter flounder antifreeze protein. The interface temperature were measured with a thermocouple. The secondary structure of this polypeptide was measured with circular dichroism spectrophotometer. It was found from the circular dichroism spectra that the polypeptide had a β-sheet structure. Although the interface temperature for the unheated solution of the polypeptide did not drop, the interface temperature for the preheated solution showed significant dropped.

Ice adhesion to a cooling solid surface occurs in various situations and sometimes results in a serious accident. Thus, it is essential to clarify phenomenon of ice adhesion, especially, ice adhesion force. The ice adhesion force to a metal surface has been always measured in a macro-scale, but the measured ice adhesion force is an apparent value including a force to break the ice. To measure the correct ice adhesion force, one of the authors developed the measurement method in a nano-scale using scanning probe microscope (SPM). In this study, the correct ice adhesion forces to the copper surface at different temperatures were measured by the SPM, and then, validity of the temperature-dependency on the ice adhesion force is investigated.

An adjoint-based shape optimization scheme for solidification problem has been extended to take into account the wall heat conduction. In comparison to the case for the isothermal condition, the shape modification rule formulated in the present study includes an additional term originating from the thermal coupling between the solidification fluid and the solid fin. It is shown through meshless analyses that, under the isothermal condition, tree-like fin shapes of which the topological nature depends on the node density are obtained. On the other hand, the shape modification under the present conjugate condition exhibits a tendency to mitigate the generation of high aspect-ratio structures and regularize the optimization.

A purpose of this study is to investigate flow characteristic of propane hydrate slurry (PHS). PHS can be transported in a tube directly. Therefore PHS can be expected reduction of the transportation cost. This experiment used the stirring method for a generation method of the PHS. From the experimental results , it was found that PHS is pseudoplastic fluid . Further, it was found that behaviour index n ' is decreased with the solid phase ratio is increased .

Clathrate hydrates are solid crystalline compounds formed by hydrogen-bonded water molecules enclosing other guest molecules in the water cages. Understanding the phase equilibrium conditions for the three-phase system composed of hydrate, water and guest molecule is crucial for various expected hydrate applications. In this study, we performed NVT (isothermal-isometric) molecular dynamics simulation of methane hydrate/water/methane system to obtain the pressure at equilibrium state. The characteristic of this simulation is that the dissociation or growth of hydrate occurs and equilibrium pressure can be obtained automatically. The result was compared to other previous data from simulations and experiments.

This paper reports the four phase equilibrium conditions and then analyzes thermal efficiency of heat engine using clathrate hydrate as the working medium. The working media was krypton and water plus each of the following substances: Neohexane and Methylcyclohexane. The heat engine was operated in the temperature range between 282 K and 293 K. Thermal efficiency was found to be 2.20% for the Kr hydrate, 2.35% for the Kr + Neohexane hydrate and 2.36 % for the Kr + Methylcyclohexane hydrate systems. The thermal efficiency was increased by 0.16 % when compared to a simple Kr system.

This paper reports the phase equilibrium temperature and dissociation heat of tetrabutylammonium butyrate (TBABu) hydrate. TBABu hydrate is a type of ionic semiclathrate hydrates. This hydrate could potentially be used as thermal energy storage materials. The phase equilibrium temperature was measured by stepwise temperature increasing procedure. The temperature – composition phase diagram of the TBABu hydrate was determined in the mass fractions from 0.20 to 0.40. The highest equilibrium temperature of TBABu hydrate was 15.3 °C at the mass fraction 0.40. On the dissociation heat of DSC measurements, the largest dissociation heat was 172 kJ/kg at the mass fraction 0.40.

Interfacial tension is an important property to closely analyze multiphase-flow dynamics. In this study, interfacial tension between methane + ethane + propane and water was measured. The molar composition methane + ethane + propane gas mixture was 90:7:3. These experiments were performed at temperatures between 283.15 K and 298.15 K and pressures between 1.00 MPa and 9.00 MPa. These conditions were close to hydrate/liquid/gas equilibrium. In these experiments, pendant drop method was used the way. In comparison with the literature data of interfacial tension in water-methane system, we clarified influences of ethane and propane on the interfacial tension.

We have produced new functional surfaces for restraining the solidification of water by adhering antifreezepolypeptides on the surfaces. To examine the effectiveness of the surfaces, we conducted simultaneously themeasurements of temperature inside a water droplet on the cooling surfaces with a fine thermocouple and theobservation of solidification of the droplets with a video microscope. It was found from the results that aglass surface with antifreeze polypeptides showed a remarkable inhibition of ice growth.

We have carried out molecular dynamics analysis for water with an ice wall, winter flounder antifreeze protein and ions to understand mechanism of a ‘synergistic effect’. This effect shows the freezing point of mixed solution is lower than the sum of the freezing point of antifreeze protein solution and the freezing point of salt solution. It is found that movement of water molecules is more inhibited by the interaction of antifreeze protein and ions than the movement of water moleculars in each single-solute solution. This may be due to the fact that the antifreeze protein strengthens hydration shell around sodium ions.

We conducted measurements on unidirectional freezing for antifreeze-protein solution either preheated or pH-controlled in a narrow space. The interface temperature was measured with a thermocouple. The turbidity of the preheated solution was measured with a ultra-violet and visible spectrophotometer. It was found from the results for the turbidity measurement that the preheated antifreeze protein formed aggregates. The interface temperature for the preheated solution was lower than that for the unheated solution. In addition, the interface temperature for the solution with its pH controlled to isoelectric point was lower than that for the solution without control.

Of ice obtained by continuous ice systems using metal foil belt, to measure crystal orientation of ice of unstable state. As a result, α angle of one crystal grain mass was confirmed that substantially matches crystal grain boundaries. In addition, it was confirmed that crystal orientation change is due to mutual change of α angle and β angle. If crystal orientation is changed periodically, it was confirmed that unstable state is maintained relatively long. At that time, crystal grain boundary is formed in a sine wave shape, crystal orientation is at apex of grain boundaries α angle of 0 °, and at inflection point β angle becomes 0 °. In addition, α angle and β angle to the boundary of 0 ° + and - back and forth.