Improvements in energy source are required for small electronic devices equipped with lithiumion batteries. Liquid hydrocarbon fuels have a much higher energy density than lithium-ion batteries, and therefore micro-combustors with liquid fuels are drawing attention. Since the evaporation of liquid fuel in a narrow space is required for micro-combustors, we use electrospray techniques. Combustion of liquid fuel in meso-scale combustor with wire mesh has been studied experimentally. The flame is stabilized behind the mesh without external heating. In this study, the inner diameter of combustor is almost equal to the quenching diameter. The flame stabilization condition for different inner diameters and fuel fractions is investigated.

To measure the high-speed temporal and spatial fluctuation of convective heat transfer, there is a method of measuring the temperature distribution of thin film heater formed on a window material with a high-speed infrared camera. However, due to the thermal inertia and heat conduction of the window material, the temperature fluctuation of the thin film is attenuated temporally and spatially, and the resolution of the measurement deteriorates. In this study, we conducted a heat conduction analysis of the heat transfer surface when heat transfer fluctuated temporally and spatially, and derived a general relationship of the upper limit of fluctuation frequency and the lower limit of spatial wavelength detectable.

In order to reduce the temperature difference between the heat source and the working fluid, twophase expansion steam cycle or trilateral cycle in which the working fluid enters the expander with gas liquid two phase or single liquid phase is demanded. In the present study, the effect of inlet quality on the efficiency of two-phase expansion is investigated. By measuring the pressure volume (P-V) diagram, the dependence of adiabatic efficiency of the two-phase expander on inlet quality is obtained. From the results, technical issues of the two-phase expander are discussed.

Stability of autonomous power unit by Micro-combustor was investigated from the temperature of the heat sink and the heat receiver and the fuel and air supply pressure. According to the non-autonomous and the autonomous power generation experiment, it was found that the amount of power generation required for autonomous power generation was obtained. We have found a policy to improve the autonomous power unit with higher performance such as power consumption increase, heat reciver temperature rise, and fuel flow decrease.

In this study, a method is proposed to enhance heat transfer in a wide range of Rayleigh numbers by impinging a low flow rate planer jet onto the low Rayleigh number natural convection region. The control of the thermal boundary layer in the high Rayleigh number natural convection region is demonstrated. To evaluate the heat transfer enhancement by the impinging jet, a numerical simulation and optical measurements of the temperature field were conducted. The analysis and measurements found that the heat transfer in both the low and high Rayleigh number natural convection regions was enhanced when the jet with a range of specific Reynolds number impinges on the low Rayleigh number natural convection region.

In this study, the relationship between the deterioration rate of protein in a preservative solution and the molecular mobility of the preservative solution was experimentally investigated by the dielectric spectroscopy and the enzymatic analysis. Dielectric spectroscopy was used to measure the molecular mobilities of water in preservative solutions at 40^oC. We also measured the enzymatic activity of L Lactate dehydrogenase (LDH) in the same preservative solution at 40^oC for 40 days to obtain the deterioration rate of LDH. Our experimental results reveal the scaling law between the deterioration rate of LDH and the molecular mobilities of water.

Recently, totally enclosed fan motor dominates the market due to its low maintenance frequency. The promotion of power output in a certain size, meanwhile, the preceding of miniaturization and lightweighting engineering are followed by huge thermal generation, thus, the demand of an improvement on cooling performance rises. Specifically, in terms of enclosed fan cooled motor, the difficulty of motor inner temperature reduction is a core issue since the cooling air primarily flowing the outer of motor. Therefore, a heat exchange structure between inner and outer air is proposed to duel with the aforementioned issue. In this report, we applied thermal fluid analysis to evaluate the heat exchange structure, and further assessments on its performance in real working environment were conducted by adaptation this structure in a motor as well.

In order to understand the effect of velocity boundary layer on the heat loss in a tumble enhanced engine, simultaneous measurements of high-speed microscopic particle image velocimetry (PIV) near the piston top and a micro electro mechanical systems (MEMS) heat flux sensor on the piston surface was conducted in the motored optical engine with enhanced tumble flow. This engine was rotated at2000 rpm. Experimental results show the correlation between the velocity fluctuation and the peak value of heat flux, and the correlation coefficient shows higher value at 0.50 mm from the piston wall rather than 0.27 mm and 0.12 mm.

This paper presents the CFD modeling of phase change process in a thermosyphon. Lee model is used to simulate phase change process. Boiling and condensation are clearly solved. As a result of comparison with experiment, good agreement of wall temperature with the evaporator and the condenser is obtained. Furthermore, temperature differences between the evaporator and the condenser are also showed same tendency as a function of input power.

In this paper, a heat transfer enhancement technique is proposed using porous materials with micropores. To eliminate the binding process between a heating surface and a fabricated porous body, the porous material is directly fabricated on a copper heating surface using a coating method. The starting material is liquid state. After coating and curing, a porous resin body with micropores is obtained. Then, the evaporation speed of water droplet is investigated with or without the porous. As a result, the experimental result found that the evaporation speed is enhanced by using the fabricated porous material.

This study focuses on the evaluation of the influence of membrane structure on protein mass transfer through membranes with micro-pore. Transient diffusion fields of protein through three types of micro porous membranes of which have different pore size and same pore cross-sectional area ratio were quantitatively visualized by phase shifting interferometer, and penetrated mass and mass flux were evaluated. Numerical simulations were also performed for varying the pore size. Even under the condition that the channel area for protein transfer was the same, penetrated mass and mass flux were affected by the pore size.

In a bipropellant thruster, a part of the liquid fuel is injected onto the combustion chamber wall to form a liquid film, which protect the wall from combustion gases. Particularly in the pulse operation, the fuel is injected onto a heated wall with temperature gradient formed by heat soak back from the nozzle throat. In this study, the transient processes of film formation and of wall temperature distribution were visualized by a high-speed imaging and an infrared camera, respectively. The behavior of wetting front propagation and the heat transfer characteristic were analyzed and found that mass flow rate of the liquid was an important factor for wetting front propagation and heat flux between the liquid film and the wall.

In this study, the flame propagation experiments of ammonia/methane/air were conducted using a fan-stirred constant volume vessel in order to clarify the effect of turbulence on the propagation limits of the ammonia/methane/air. Results show that the ammonia/methane/air mixture with a 0.9 equivalence ratio can propagate at the highest turbulence intensity and flames can propagate in larger turbulence Karlovitz number at smaller Markstein number. These tendencies are considered to be due to the diffusional-thermal instability of the flame surface.

This paper describes the feasibility of dynamic thermal control using solid-solid phase change heat storage materials. Vanadium dioxide VO2, which is one of the solid-solid phase transition materials, has a large latent heat and can be used as a temperature leveling element for electronic devices. In this study, the temperature change of the heat generating element coupled with VO2 was evaluated by a heat transfer simulation and a verification experiment. As a result, it became clear that the time required for the heating element to reach an arbitrary critical temperature can be lengthened by coupling VO2.

Cooling losses must be reduced to improve the thermal efficiency of automobile engines. The purpose of this study is to develop a generic measurement method for investigating the relationship between flow and heat transport to quantitatively evaluate cooling lose. We developed a thin film resistance temperature sensor using MEMS and conducted an experiment to measure the wall heat flux at four adjacent points. The time delay was obtained from the four heat flux fluctuation waveforms, and the advection velocity near the wall surface could be extracted. Assuming a vortex model, the vortex scale was calculated from the estimated changes in velocity and heat flux. The estimated flow velocity and vortex models were evaluated by measuring the flow velocity near the wall a hot wire anemometer.

A spectral emittance of Metal/Insulator/Metal (MIM) structured emitter was optimized for a spectrally controlled Metal/Semiconductor/Metal (MSM) structured thermophotovoltaic (TPV) cell using a Bayesian optimization method. Corresponding to the spectral absorptance of MSM cell around the bandgap wavelength of GaSb semiconductor, an emittance with an almost unity only around the bandgap could be achieved by selecting the adequate structure of MIM emitter.

Experiments are performed to examine the heat transfer performance of aluminum surface with fine tunnel structures. The smooth and the seven tunnel surfaces are tested in this study. Fluorine-based refrigerant HFE-7000 was selected as a working fluid. Experimental absolute pressure rang used are 0.10,0.14 and 0.18MPa. The obtained boiling curve indicates that type C has the highest heat transfer performance among the tested surfaces. The heat transfer is higher than seven times of smooth surface at 20kW/m² of 0.14MPa, and five times at 80kW/m² of 0.18MPa. Furthermore, the number of nucleation points of type C at the low superheat is more than 300, while those of type A and smooth surfaces are approximately 40 and 10, respectively.

To analyze the boiling mechanism with dimple type heat transfer surface in low pressure boiling cooling, effect of dimple diameter and pitch on heat flux and void fraction is examined. Six dimple type surfaces are used, and pure water is used as the working liquid with the liquid height of 40 mm and saturation pressure of 15 kPa. The heat transfer surface with a dimple diameter of 5 mm shows the highest performance. Also, the diameter of detached bubbles is about 5 ~ 8mm which is close to the dimple diameter. Furthermore, the heat transfer surface with a dimple diameter of 5 mm shows an intermediate value of corrected void fraction compared with other heat transfer surfaces.

This work aims to clarify the spherical turbulent flame propagation behavior of the pulverized coal particle clouds/ammonia co-combustion under different ammonia/oxygen/nitrogen equivalence ratios. Experiments were conducted under various turbulence intensities (u ^'=0, 0.32, 0.65, 0.97, 1.29 m/s) and in ammonia-lean conditions (ϕ = 0.4, 0.6, 0.8) with a common bituminous coal by using a constant volume spherical chamber. The result indicated propagation velocities of the luminous flame front and the reaction front in co-combustion increased with increasing turbulence intensity. The turbulent flame propagation velocity of the pulverized coal/ammonia co-combustion was higher than that of the pure pulverized coal combustion and that of the pure ammonia combustion under all conditions.

For polymer electrolyte fuel cell (PEFC), it is important to control water drainage to supply oxygen to catalyst layer (CL) in high current density. Gas diffusion layers (GDLs) have a critical role of water drainage and gas distribution in PEFC. Our previous researches showed that hydrophilic treatment of GDL surface decreases water accumulation in GDLs. This study investigated water behavior in the cell channel using CCD camera with normal GDLs and hydrophilic treatment GDLs. By observing the water behavior and measuring the cell voltage stability, the effect of hydrophilic treatment for the cell performance was discussed.

One of the problems of thermoelectric power generator is the fluctuation of output due to a temperature fluctuation of the heat source. To solve this problem, we propose a thermoelectric generator that uses vanadium dioxide (VO2), which is a latent heat storage material, as a thermoelectric material. VO2 is a solid-solid phase transition material and has a large latent heat associated with the phase transition. Therefore, the thermoelectric generator using VO2 may reduce the temperature fluctuation of the heat source and realize constant output. In this study, a VO2 sintered body was prepared and the thermoelectric properties of the VO2 sintered body was measured. The power factor, which is a measure of power generation performance of thermoelectric materials, of the VO2 sintered body increased significantly after the phase transition into the metallic phase, and reached 6 μWm^-1K^-2 at maximum.

In the nanotechnology including microfluidics, thermocapillary convection is useful to manipulate suspended micro/nano particles, bubbles, and droplets in liquid, because it enables less-invasive control of fluid motions by local heating due to a focused laser light. We focused on a fabrication method for a ring structure of assembled nanoparticles on a gold substrate using laser light that produces micro bubble on the substrate. Since the flow measurement around a micro bubble is difficult in practice, the accumulation of nanoparticles is still not sufficiently understood. We numerically investigated the thermocapillary-driven flow of bubble on locally heated wall by using the Volume-of-Fluid method to track liquid-vapor interface. An axisymmetric steady flow field was found to become non-axisymmetric and unsteady even with a small temperature difference.

Since the Oscillating heat pipe does not have a wick structure in the flow path, it has a high heat transport capacity which is crucial for cooling high heat flux electronic devices. However, due to insufficient understanding of activation mechanism and lack of performance prediction model, experimental studies and theoretical elucidation of activation characteristics have been actively conducted. In this study, we proposed to introduce an novel variable path oscillating heat pipe, with expansion channel in the heating region and a converging channel in the cooling region in order to facilitate the volume change of the vapor slug during the evaporation and condesation. The steady-state operation performance of the variable path oscillating heat pipe were experimentally investigated.

This paper describes the development of a miniature loop heat pipe (mLHP) for the purpose of cooling a small and high heat flux device. The mLHP comprises an evaporator (15×16×t3 mm3 ), a condenser (12×12.5×t2 mm3 ) and transport lines (L=100 mm), with ethanol as working fluid. Heat transport performance of the mLHP under several heat dissipation conditions of the condenser (bare, with copper plate, with copper plate and small fan and with aluminum cold plate) was evaluated. In the case of the aluminum cold plate (35×20×t3 mm3 , coolant: water, inlet temp: 25℃, circulation rate: 1 ml/min), the mLHP performed high heat transport of 15 W (heat flux of 60 W/cm2 ), where the evaporator temperature and thermal resistance were 142.2℃ and 0.72℃/W, respectively.

In recent years, greenhouse horticulture was becoming mainstream for vegetables and fruits. However, the temperature control of these greenhouse was used very expensive fossil fuel. In fact, its cost accounts for 30% of the total expenditure on typical farms. Besides, fossil fuels also emit harmful gases. Therefore, we developed temperature-control system using renewable energy, e.g. grand water. Consequently, the cost of our system was reduced to less than 1/10 of conventional by demonstration experiment. Moreover, its system does not emit harmful gases. Nevertheless, this technology has several problems. Among them, this paper focuses on reduce the cost of implementing this technology by simplification. As the result, the ability of cooling was decreased by only about 4% by applied simplification. Also, this ability did not depend on the difference in the structure of a serial channel.

This study focused on heat transfer in a porous media with high Biot number. Introducing the nunsteady volume averaged Nusselt number, temperature distribution in a porous media with high Biot number was estimated by an analysis of non-thermal equilibrium macroscopic energy equations. Comparison of temperature distributions between the presented analysis and the direct numerical simulation revealed that the presented analysis is reasonable to treat with heat transfer in a porous media with high Biot number.

In the present study, a general two-compartment model that can accurately evaluate the mass balance in the body was mathematically derived by adapting volume-averaging theory to the mass transfer around peripheral tissues. Introducing variable transformation, exact solutions of the proposed two-compartment model during and after dialysis were derived, and the validity of the proposed exact solutions was examined by comparing these solutions with clinical data and the numerical solution. A series of investigations revealed that the proposed two-compartment model can accurately reproduce the behavior of the measured blood urea concentration during and after dialysis.

Binary power generation systems powered by hot springs have issues associated with the deposition of calcium carbonate on transport pipes and heat exchangers. In this study, a numerical simulation based on mass transfer was proposed for reproducing the process of calcium carbonate generation and blockage of the flow channel. A series of numerical simulations, which reproduced previous experiments using a milli-channel heat exchanger, revealed that the proposed method can reproduce the process of clogging of the flow channel by the scale, and the precipitation amount obtained by the proposed method is reasonable.

The PEFC catal\st la\er is generall\ prepared b\ coating the catal\st ink using a slot die, but it is known that streak\ defects occur with high-speed coating. In this stud\, coating e[periments using catal\st inks with different solvent compositions are conducted to elucidate the effect of the solvent composition on coating stabilit\. The results show the coating stabilit\ changed due to the difference in viscosit\ and surface tension when the ethanol/water ratio of the solvent was different.

In this study, we measured the temperature distributions of Ag nano-wire network, which consists of nano-wire with diameter of 100nm and length of 100m, when a constant current was supplied using two-dimensional thermoreflectance imaging method. The temperature of the nanowires increased as the applied current increased. However, the temperature distribution was not uniform and a variation was observed. We believe that this was attributed to the electric resistance variation caused by the nano-wire number density difference and the contact condition between the nano-wires. Weibull distribution was applied to the frequency distribution of the temperature difference from the base value for each applied current. The scale and shape parameters were evaluated to discuss the effects of the current on the Joule heating and heat transfer characteristics of the nano-wire network.

One of the problems for PEFC spread is its high cost. To cut off the cost, we tried to reduce the amount of Pt in PEFC catalyst layer by introducing graphene as carbon support material because it’s reported that graphene has proton conductivity. If we could make ionomer-free CLs, oxygen transport resistance in CL that impede smooth oxygen transport to Pt would be much reduced and we would be able to use Pt more effectively. We made ionomer-free graphene CLs and conventional type CL and measured their performances. Through these results, using graphene in PEFC CL is beneficial for cutting its cost. However, controlling the structure of graphene CL is difficult. We discussed fabricating method for graphene-based ionomer-free PEFC catalyst layer.

In order to enable high quality cryopreservation of foods and bio tissue, it is necessary to consider the effect of the texture on the formation and melting of ice crystals in the cell and tissue. In addition to the above, it is necessary to clarify the process of melting and regrowth of ice crystals in bio tissue during cryopreservation and control the particle size of ice crystals. In this study, we attempted to observe the internal state of biological samples non-destructively by irradiating a sample with near infrared light, which has high body permeability, and detecting the distribution of water and ice crystals in bio tissue by utilizing the difference in the near-infrared transmittance to blood, lipids, water, and ice.

Recently, the problem of global warming by carbon dioxide has become serious. In order to reduce energy consumption at home, living environment that can reduce the use of cooling and heating equipment is desired. The purpose of this paper is to realize the thermal switching coating that can control radiative absorption of dispersed particles in each temperature conditions by using LSPR. First, the dependence of the clearance distance on the absorption performance of the particles was calculated. Next, thermal switching coating was made of gel and metal nano-particles. The absorption performance of the coating was evaluated by spectrophotometer. As a result, it was shown that the absorption performance of the coating shifts by varying volume fraction of nano-particles.

Recently, it has been reported that a direct absorption solar collector (DASC) using plasmonic nanofluid is usefulness for collecting solar energy. In DASC, nanoparticles in a nanofluid absorb sunlight by localized surface plasmon resonance (LSPR), and the particles are heated by photo-thermal conversion, and the heat is transferred to the fluid. In order to improve the performance of DASC, it is necessary to improve the absorption performance of nanoparticles. Therefore, electromagnetic field analysis was conducted in order to theoretically design nanoparticles with metal stack structure, which are produced by sputtering. As a result, it was found that the plasmonic particles have 2.4 times the absorption performance compared with simple spherical particles. In addition to, the plasmonic particles have 12.5 times the economic performance compared with simple spherical particles. Therefore, the usefulness of plasmonic particles was confirmed.

This study experimentally investigated the boiling heat transfer characteristic of R32 vertical upward flow in a plate-fin heat exchanger. The experiments were carried out for a mass velocity range of 20–50 kgm-2s-1 and heat flux range of 3−6 kWm-2 at a saturation temperature of 15 °C. The heat transfer coefficient decreased with increasing vapor quality at low mass velocities because the dry area expanded with decreasing mass velocity and increasing vapor quality. The heat transfer coefficient increased with increasing vapor quality and heat flux due to enhance the forced convection and nucleate boiling.

Bio-coke is a solid biofuel that uses biomass as a raw material, but it has high density and high strength and maintains its shape even at high temperatures, so it is possible to sustain sluggish combustion. The previous study showed that the combustion time of Bio-coke which aspect ratio is 1 proportional to (V/S)2 . In the present study, Bio-coke with different aspect ratios was used to investigate the effect of sample length on combustion behavior. The direction in which hot air is supplied was set to two patterns, the end face direction or the cylindrical direction by changing the placement of the sample. As a result, we found that the combustion time of Bio-coke was proportional to (V/S)2 in the case of horizontal placement (heated air was supplied from the end-surface direction) even when the aspect ratio was different.