This study has been investigated the development of a high heat-flux cooling device. The subcooled flow boiling performance of a dielectric liquid (Novec-7000, C₃F7OCH₃) was experimentally characterized. An electrode fabricated with ten 1000 μm slits was placed at 600 μm above a heated surface, and was energized to generate a high electric field in the gap between the heated surface and the electrode. The heat performance of the heated wall surface was evaluated at various electric fields (0, 1.6, -3.3, -5.0 kV/mm ), inlet flow rates (1.83, 3.33, and 4.83 g/s), and subcooling temperatures (5, 9, 15, 25 K). A predictive equation derived from the sensible and latent heats successfully predicted the experimental results.

In this study, we investigated the effect of rapid cooling using ice slurry on the metabolic activity of biological tissue by a numerical simulation. In this study, we simulated the melting heat transfer of ice slurries being placed on the biological tissue. We examined the optimum cooling method by changing the IPF (ice packing factor) and amount of ice slurry. As a result, rapid cooling using ice slurry is effective in preventing ischemic damage due to ischemia during surgery, and it suggested that there is a thermally optimal amount of ice slurry and IPF depending on the purpose.

In this paper, a lattice structure was fabricated using a 3D printer employing a selective laser melting method, and its heat transfer characteristics were evaluated experimentally. The lattice discussed in this paper is BCC (Body Centered Cubic) structure, which was made of an aluminum alloy (AlSi10Mg). The BCC structure can enhance the heat exchanging property, and decrease the wall temperature Finally, it is found that the heat transfer coefficient of BCC structure was confirmed to be 2.5 to 4 times higher than that of the flat plate.

A non-uniform stress distribution forms within the composite electrode layers of sulfide all-solid-state lithium-ion battery due to the variation in Young's moduli. In this study, the effect of stress distribution on lithium-ion transportation is investigated using a composite consisting sulfide solid electrolyte and zirconia. By considering stress distribution in our ion conductance simulation, we have succeeded in obtaining an ion conductivity value about fourfold closer to a value measured experimentally than the case when stress distribution was not considered. Additionally, the non-linear compressive behavior of solid electrolyte displayed limitations of utilizing finite element method.

To investigate the flame propagation characteristics under a high efficiency spark ignition engine condition, a direct numerical simulation (DNS) of forced ignition of premixed mixtures in a constant volume vessel with a tumble flow has been performed for a lean Toluene Reference Fuel (TRF)-air mixture at a high exhaust gas recirculation (EGR) rate at high pressure. The wall heat flux evolution during flame-wall interaction is discussed based on DNS results.

Wall chemical effect for a premixed H₂/air flame was investigated in a quartz micro flow reactor. Two-dimensional O atom distributions of this stationary normal flame near the quartz and Inconel wall surfaces were measured by the two-photon absorption laser induced fluorescence (TALIF). It is found that the shape and the streamwise position in the reactor of the flame are significantly affected by the wall surface material. The O atom concentration near the Inconel surface is lower than that near the quartz surface, indicating a stronger adsorption of O atom over the Inconel surface. (93 words)

The object of this study is to investigate the effect of Prandtl number in heat transfer phenomena of turbulent boundary layer with various external forces by means of direct numerical simulation (DNS). In this study, DNS of turbulent boundary layer with an adverse pressure gradient (APG) or a buoyancy is carried out under conditions of three different Prandtl number. In the boundary layer of thermal field which develops in the entrance region due to the boundary condition of wall, the effect of Prandtl number is clearly observed in all cases, though the thermal boundary layer is not fully developed. However, in the case of lower Prandtl number, the effects of APG or buoyancy cannot be much seen. As for the boundary layer of velocity field, it can be slightly observed the effect of Prandtl number due to the undeveloped thermal boundary layer. Therefore, DNSs of this study reveal characteristics and structures of turbulent boundary layer with various external forces in various Prandtl number.

In this study, flow and heat transfer characteristics of erythritol slurry, which is suitable as heat transfer medium, were investigated experimentally. The pressure drop and the heat transfer coefficient were measured in a circular tube with the diameter of 7.5mm and 10.2mm. Erythritol slurry with an initial concentration of 5-30 mass% was used as a sample. As the results, it is found that the ratio of pipe friction coefficient increases with the solid fraction. In addition, the ratio of Nusselt numbers increases with the solid fraction at less than 20 mass% of solid fraction. In contrast, for 30 mass% of solid fraction, the ratio of Nusselt number decreased greatly.

Electrochemical activity of the triple-phase boundaries in GDC (gadolinia-doped ceria)-infiltrated LSCF (lanthanum strontium cobalt ferrite) cathode is evaluated using numerical simulation by fitting the predicted overpotential characteristics of the cathode to the corresponding experimental data. Microstructure model of the GDC-infiltrated LSCF cathode is developed to estimate the triple-phase boundary density and the double phase boundary density in the cathode, and the microstructural parameters are applied to the numerical model to eliminate arbitrary fitting parameters except for the electrochemical activity. It is found that the total electrochemical activity is significantly increased by the newly formed TPBs.

A porous Ni-YSZ (yttria-stabilized zirconia) anode of solid oxide fuel cells (SOFCs) is fabricated with pore former and its effect on gas transport property is investigated using microstructural analysis and two-dimensional numerical analysis of gas diffusion. It is found that the structural scale of the pores formed in the porous anode is reasonable for the particle size of the added pore former and that the smaller the scale of the pores, the more liner and uniform the partial pressure distribution generated in the structure.

Ground source heat pumps (GSHPs) use buried pipes to extract heat from the ground and to release heat to the ground. In a conventional GSHP system, which uses an indirect heat exchange method, vertical systems use two long pipes connected by a U-shaped fitting at the bottom of a hole bored in the ground. In contrast, a GSHP that uses a direct expansion method circulates a mixed refrigerant through the ground loop. In the experiment, the depth of the borehole was 30 m, and the refrigerant was R410A. The heat exchanger of a ready-made air-conditioner was replaced by an underground heat exchanger. The underground heat exchanger consisted of narrow copper tubes inserted into the bottom end of a long pipe filled with water. This paper describes experimental results of the GSHP that uses the direct expansion method with various underground heat exchangers.

We investigated droplet evaporation characteristics of two diesel surrogate fuels under several ambient temperature and pressure. One has 4 components, and the other has the same 4 components plus low volatile substance, Eicosane. Droplet lifetime of diesel fuel was longer than that of these surrogate fuels. Because of Eicosane, droplet lifetime of the surrogate fuel which has 4 components plus Eicosane was longer than that of another surrogate fuel which has 4 components. Instantaneous evaporation rate of the surrogate fuel which has 4 components plus Eicosane decreased at low ambient temperature.

A temperature visualization method using Temperature Sensitive Paint (TSP) was used to measure the temperature distribution on the heat transfer surface with high temporal resolution during flow boiling. A heat transfer surface was fabricated by forming PtTFPP, a TSP sensor material, on the heat transfer surface, and high-speed visualization measurement was performed at 1 kHz in forced flow boiling. It was confirmed that the change rate of the temperature distribution calculated based on the TSP emission intensity followed the bubble flow rate confirmed by the bubble behavior observation. The temperature rise of the dry patch at the bottom of the bubble was captured, suggesting a high thermal response to changes in the temperature distribution of the boiling bubble.

This paper presents the thermodynamic analysis of an existing thermal power plant repowered with the heat recovery from solid oxide fuel cell (SOFC) exhaust gas. As a bottoming of SOFC，steam turbine (ST) is placed. To generate the steam for the ST, heat is recovered from the SOFC exhaust gas using the existing boiler facility with additional installation of convective evaporator and burner. The effects operational parameters of the SOFC, degrees of fuel utilization, current density and operating temperature on the entire system performance are investigated.

A heat pipe is an important heat transport element that is required to work in various environments. In this study, in order to visualize evaporation and condensation phenomena, we prepared a visualization device that models a heat pipe. The dependence of the behavior of internal working fluid and heat transfer with water and ethanol was measured using thermography. We compared the pure water and ethanol under 30% sealing ratio and 20% sealing ratio conditions. The heat transfer amount was larger in pure water in both cases. Also, the amount of heat transport was larger when the enclosure ratio was higher for both pure water and ethanol.

The flow field around concentric cylinders for oxygen sensor was visualized by particle image velocimetry and CFD. Two different size of transparent acrylic models were used and measurements were carried out by room temperature air with micro-capsule as tracer. The quantitative visualization resulted that the flow direction within the internal shrouds is opposed to the external main flow while that of within the external shrouds is not. The velocity magnitude of the internal flow was significantly lower than that of the main flow. The throughput of the concentration fluctuation is enhanced by the higher velocity fluctuation around the side apertures that contribute to the quick response of the entire sensor module. And the numerical simulation also showed the similar mean flow field with experimental result.

A unique measurement technique for visualizing the spatial temperature distribution of a non-isothermal flow field has been developed. This technique named a “fluid temperature-field scanner (FTS)” enables us to visualize the two-dimensional temperature profile by tracking the trajectory of a rod-type temperature probe using a high-speed CMOS camera and superimposing the measurement results on the photograph of a measurement object taken with the same CMOS camera. In the present study, ten fine cold-wires (5 mm in diameter), which were operated at a constant current mode, were used as the temperature sensors for the rod-type probe. As a result, it is demonstrated that a nonuniform mean and rms temperature distributions of a heated airflow can be visualized readily and quantitatively by the FTS together with the moving- and ensemble-averaging techniques for the response-compensated temperature signals of the cold-wires.

Flame spread over a thin paper-disk in concurrent oxidizer flow within narrow channel was observed. The oxidizer flow rate and channel height were varied from 0.02 to 2 L/min and 2 to 16 mm, respectively. After the ignition, the flame initially spreads in radial direction, then it separates into multiple flamelets like conventional fingering pattern formation. The conditions where the fingering pattern formation occurs were identified based on the separation behavior. Under a certain condition, the separated flamelets move in circumferential direction along the solid edge. It indicates the existence of circumferential growth mode of fingering pattern.

A flow channel with finger-stacked structure (FSS) has been proposed for the first wall cooling in a molten salt blanket of a fusion reactor. To evaluate the feasibility of the FSS channel, it is necessary to simulate the condition of the fusion reactor; one-sided heating, rectangle channel, heating of heat transfer promotors, and strong magnetic field. One side heating and rectangle channel conditions were tested in previous studies. To evaluate the influence of the heating of the heat transfer promotor against the heat transfer performance, in this study the heat transfer experiment was conducted. In the experiment, Particle Reynolds number was ranged from 1500 to 5000, heat fluxes from the wall was from 0.03 to 0.07 MW/m2, and averaged heat flux of the finger surface was set at 10 %, 20%, 30 %, and 40 % of the wall heat flux. It was revealed that the heating of the finger did not influence against heat transfer performance.

This study aims to extend a theory of a ignition kernel to a turbulent flow in order to predict a ignition kernel development including minimum ignition energy (MIE) transition. First, we introduce governing equations expressing ignition kernel development in a turbulent flow. Then, a analytical solution is derived by employing asumptions, such as quasi-steady state, a constant density model, and a jump condition at a flame reaction zone. The analytical solution can express a increase in flame propagation due to turbulence. MIE including the MIE transition can also be predicted quantitatively by introducing correlation terms and tuning the model constants.

This study aims to develop a new energy cycle by continuously combusting aluminum with high energy density comparable to petroleum and then recovering the thermal and light energy. A powder feeder was designed and developed, and the combustion behaviors of aluminum powder-oxygen-nitrogen solid-gas two-phase flow were investigated. The transition from steady combustion to unsteady combustion was observed as flow rate was increased, but the steady combustion was realized even at high flow rates by increasing the oxygen concentration. The temperature measurement via the infrared camera showed that the flame temperature was increased with the oxygen concentration. The radiative heat flux from a flame was increased due to the increased oxygen concentration, thereby extending the flame-propagation limit and then achieving the steady combustion at high flow rates.

Cogeneration system is an important factor for improving the efficiency of biomass energy conversion process. However, the development of large-capacity heat storage agents is a breakthrough in order to balance supply and demand for heat utilization. In this study, focusing on the thermal storage effect of lithium bromide / water fine crystal slurry absorbent, the effect of crystal nuclei on the fine crystal slurry formation characteristics was investigated. In addition, the heat storage density was calculated from an equilibrium theory, and it was clarified that not only the heat storage density was higher than that of the conventional PCM heat storage material, but also the heat generation temperature could be controlled widely depending on the operating conditions.(117)

For establishing a new fuel reactivity index, characteristics of separated weak flames (cool, blue and hot flames) of PRF and C5 alkane isomers in a micro flow reactor with a controlled temperature profile at a pressure of 500 kPa were examined. Since cool and blue flames are enhanced compared to hot flame in low-to-intermediate temperatures at elevated pressures, heat and intermediates formed in cool and blue flames were analyzed by numerical simulations. It was confirmed that the ratio of heat formed in the blue flame to the total heat release, named as heat contribution index (HCI), could be a measure that well-described fuel reactivity. A fuel with higher HCI showed lower reactivity. It was also found that the ratio of formaldehyde formed in cool flame of a given fuel to that of n-heptane, named as Formaldehyde index (FAI), was a measure that well-described fuel reactivity and was able to be experimentally obtained using a gas chromatograph. HCI and FAI were in good agreements with each other. Furthermore, FAI showed a linear correlation with the critical compression ratio.

Recently, polymer electrolyte fuel cells (PEFCs) is highlighted by a high energy efficient and eco-friendly. However, it doesn’t spread enough because it have a lot of problems. Therefore, we have developed a membrane electrode assembly with a self-water management catalyst layer (SWMC). The SWMC can keep a three phase interface appropriately by adding a carbon powder as a porous medium to a catalyst layer. A graphite and a carbon black were evaluated as a water control grain. As a result, the performance with the SWHC was equal to the standard MEA in spite of amount of low platinum. Moreover, the SWHC was able to reduce the amount of Pt up to 16.1wt%.