Ice accretion causes serious problems, such as low visibility of windshield of vehicles and low performance of aircraft wings. In these examples, impinging water droplets are often in the state of supercooled. However, the impinging water droplets in many previous studies were not in the actual state. Thus, we carried out experiments of supercooled water droplets impinged on cold specimens. We adopted glass plates with micro-scale lattice-patterned grooves as the specimens because they can attenuate the frost layer growth. It was found from the experiments that the completion time of the droplet freezing was prolonged compared with that for a bare glass plate, irrespective of the droplet temperature.

Herein, the effect of heating rate on Palm Oil Mill Effluent (POME) conversion was studied under supercritical condition. A continuous flow reactor was employed at a temperature of 600 °C and a pressure of 25 MPa. Three preheater lengths (1, 2, and 4 m) were employed along with a flow rate of 2 g/min to control the feedstock heating rate. The result shows that longer preheaters affect to the slower heating rate. The slowing of heating rate caused the decrease of carbon gasification efficiency (CGE). The preheater length affects the precipitation of phosphorus in the reactor wall during reactions.

Thermoacoustic engine utilizing evaporation and condensation of liquid is one of promising device for utilization of unused thermal energy at low temperature level. In this paper, cascade thermoacoustic engine composed of a wet-type prime mover using phase change and a dry-type prime mover has been proposed. Experiments were performed in a vertical cylinder system with evaporator, by varying temperature at hot side T_H2 and cold side T_C2 in dry stack. As the results, it was found that the acoustic power was amplified with increasing temperature ratio T_H2/T_C2. The characteristics of gas oscillation was also discussed in relation to input heat in evaporator and length of resonance tube.

A thermoelectric generation system (TEG) is well known as an exhaust heat recovery system. Also, a thermosiphon type heat exchanger is known that it has higher heat transfer performance using circulation of refrigerant with evaporation and condensation cycle. In case of using the heat exchanger for TEG, it is important to optimize refrigerant amount. In this study, the effect of refrigerant amount on heat transfer and the electric output has been investigated in the TEG with the thermosiphon type heat exchanger.

The charge/discharge characteristics were evaluated focusing on the mixing ratio of the active material, conductive additive, electrolyte, and electrode thickness that constitute the slurry electrode for semi-solid redox flow batteries in order to explore appropriate conditions for cell performance. It was found that the electrochemical reaction in the slurry electrode was biased to the current collector. It was also shown that increase in the amount of conductive additive leads to less overpotential, suggesting better electron transport pass established in the slurry electrode, while increase in the amount of active material deteriorated capacity retention presumably due to the volume change under the charge and discharge cycle.

This study describes effects of deceleration period of pulsating flow on the level of the heat transfer enhancement around a rectangular heating element. Our recent study has reported that the application of the pulsating flow enhances heat transfer around heating elements mounted in thermal equipment such as high-density packaging electronic equipment. In this report, we investigated the heat transfer performance around the heating element mounted in two parallel plates while changing the time of the deceleration period of the pulsating flow through 2-Dimenstional Computational Fluid Dynamics analysis using OpenFOAM 4.1. It is found that the time of the deceleration period affects the whole heat transfer performance around the heating element.

Smoldering spread along a horizontally-oriented thin cellulosic solid in a narrow channel is a representative near-limit fire phenomenon. Because of the narrowness of the domain, the phenomenon allows reduced-dimensional modeling. This paper presents a one-dimensional model, which considers two reactions, i.e., cellulose pyrolysis that produces char (and gaseous species) and char oxidation. Traveling-wave solutions are numerically obtained by a shooting method.

We investigate experimentally natural convection heat transfer between vertical parallel plates in water with bubble injection. The heat transfer coefficient with bubble injection increases by approximately 20 % when a vertical unheated plate is placed near a vertical heated plate. Near the heated wall, the concentration and rise velocity of bubbles are higher with the unheated plate than without the plate. In addition, for the case with the unheated plate, a large-sized vortex does not appear. Hence, we speculate that for the case with the unheated plate, upward liquid flow induced by bubbles at higher speeds makes a major contribution to the heat transfer enhancement by bubble injection.

In this study, density difference convection during the neutralization reaction in hydrochloric acid-sodium hydroxide system or in acetic acid-sodium hydroxide system has been investigated using the laser speckle method. Some plumes generated at the region between the product solution and the acid solution and progressed with time because Rayleigh Talor instability could be observed in the region. Propagating speed of the plumes in hydrochloric acid-sodium hydroxide system were almost constant along the horizontal axis. On the other hand, the ununiform plumes in acetic acid-sodium hydroxide system were more than that in acetic acid-sodium hydroxide system. Furthermore, the propagating speed in acetic acid-sodium hydroxide system was lower than that in acetic acid-sodium hydroxide system. These facts could be occurred by the difference of the dissolution degree of the acid.

Non-aggregated SiO₂ nanoparticles formation was investigated using a premixed flame. The hexamethyldisiloxane as precursor material and the ethanol as solvent were mixed in the stainless-steel tank. When the vapor of the low concentration of the precursor material was fed into the premixed flame by using air bubbling, the non-aggregated nanoparticles could be formed. On the other hand, the shape of the non-aggregated particles does not change with increase of the bubbling flow rate.

In this study, we measured the temperature distribution of the horizontal cross section on the heated substrate when the simulated source material gas was supplied using an experimental device with a double circular tube structure for desiring of the chemical vapor deposition reactor. Mainly the total gas flow rate and the distance between the tip of the nozzle and the substrate H were changed. As a result, it was found that the average Nusselt number at H = 20 mm was higher than that at H = 5 mm. The Nusselt number distribution was considered to be the most uniform at Re = 7.6 and H = 5 mm. On the other hand, at H = 20 mm, the higher the gas flow rate got the more uniform the Nusselt number distribution.

This paper reports a new manufacturing method of a membrane electrode assembly (MEA) for polymer electrolyte fuel cell using an inkjet printer. This method enabled manufacturing a thin catalyst layer of 5μm or less, and a reduction of the amount of Pt catalyst of 36wt% from a conventional MEA made by a doctor blade method. Moreover, the performance of the cell with a MEA made by an inkjet printer was better than that of a conventional MEA regardless of the presence of humidifying the supply gas. The introduction of an inkjet printer into a catalyst layer manufacturing suggested being able to reduce a production cost of PEFC greatly.

In this study, we developed a measurement method for convective heat transfer of phase change material in rectangular cavity using an infrared thermography. As phase change materials melt in a cavity, the number and size of natural convection plumes varies depending on the Rayleigh number and aspect ratio of the liquid phase. An effort was made to quantify the time-dependent phenomena of the plumes in the cavity based on spatio-temporal temperature measurements of a heated surface using an infrared thermography. To evaluate the heat transfer characteristics in the cavity, we also calculated the heat flux distribution of heated surface based on the heated thin-foil technique. In addition, an image processing was performed to evaluate quantitatively the number and movement of natural convection plumes in the cavity.

In this study, we developed a MEMS heat flux sensor to measure surface local heat transfer in flow boiling in a minichannel. The MEMS heat flux sensor has stacked structure of two thin film temperature sensors, and the local heat flux can be analyzed by 1-D transient heat conduction simulation using the measured two temperatures as boundary conditions. The measured heat flux clearly shows thin film evaporation with a high heat flux over 1MW/m², dry-out of the thin liquid film and rewetting of the dried surface. The developed sensor was confirmed to be a powerful tool to explore the boiling heat transfer mechanisms.

At the decommissioning of the Fukushima Daiichi Nuclear Power Station, it is necessary to store seawater containing spent radioactive wastes such as cesium adsorbents safely. Since the increased seawater concentration with temperature affects the corrosion rate of vessel materials as a part of drying phenomena, a two-dimensional drying-process simulation code which installed experimentally correlations of capillary action etc. has been improved in order to predict above-mentioned momentary situations caused by drying. Trial analytical results obtained with the code agreed well with the experimental results obtained under simple experimental conditions using an electric heater and a zeolite column.

Due to a miniaturization of electronic devices, an improvement of temperature measurement techniques for miniaturized electrical components is strongly needed in order to insure the operation guaranteed temperature. Several types of thermocouples are widely used for measuring temperature. However, when temperature of the miniature devices is evaluated by thermocouples, temperature of the measurement points may decrease because the thermocouples dissipate heat like a pin fin. Therefore, in order to improve the measurement accuracy of temperature of the miniaturized devices by using thermocouples, an evaluation of heat transfer around thermocouples becomes important. In this report, a heat transfer experiment around thermocouples installed on the surface of the PCBs was conducted while changing the type and the mounting angle of thermocouples. Through the temperature measurement, the decrease of the temperature around the thermocouples was confirmed.

This study presents a novel thermal energy harvester design with standalone field-enhanced pyroelectric cycle. An electret is introduced to apply the electrical field on the ferroelectric to replace the external voltage source. With synchronized electrical fields with the temperature fluctuations, a novel electret-enhanced pyroelectric generation mode can be achieved with higher harvesting performance than the electrostatic mode and pyroelectric mode. Up to 8.95 μW/cm³ power output has been obtained with less than 3 °C temperature fluctuation in our prototype with KTN crystal.

This paper aims to investigate the effect of heat transfer enhancement and tube shortening in the evaporator of the air conditioner by using twisted-tape insert. The evaporator is a counter-flowing tube-in-tube heat exchanger and a refrigerant R410A in an inner copper tube is heated by water in an annular passage. Experiments have been conducted in a 17.05mm ID and 1 m length test section containing twist-tape for twist-ratios of 3.3, 3.9 and 5.1 under various conditions of the refrigerant mass flux, the heat flux in the heat exchanger and the vapor quality. Data on heat transfer and pressure drop coefficients in the test section were obtained to discuss the effectiveness of twisted tape insert in the evaporator of the air conditioner. Furthermore, in order to show the effect of the twisted tape on the flow pattern of the refrigerant, the flow was visualized at the inlet and outlet of the test section.

This paper describes the experimental result of a large capacity loop heat pipe (LHP). A LHP is a two-phase heat transfer device that utilizes capillary force. The LHP with several kW heat transport capability was fabricated and tested. Water was used as the working fluid and SUS316 was used as the wick. The condenser was cooled under four conditions: natural air convection and forced air convection, natural water convection, and forced water convection. It was confirmed experimentally that this device can transport the 4.0 kW heat in the steady state under the forced water convection.

Since the boiling heat transfer is much affected by the nucleation of bubble and its growth, estimation of such process is essential for the accurate prediction of the heat transfer. In this study, molecular dynamics simulation was performed in order to clarify the effect of the wall condition on the bubble growth. The simulation results show that the evaporation near the contact line effects on bubble growth ratio, which may be due to wall slip condition and bubble interface shape.

The heat flow characteristics of forced convection subcooled boiling greatly depend on the bubble diameter. For this reason, many studies on the bubble diameter have been conducted, but most studies are on the average bubble diameter and the effect of nucleation site shape on the bubble has not been considered. In this study, a visualization experiment is conducted for low-pressure forced convection subcooled boiling using water as a working fluid. The bubble diameter distribution generated in the nucleation site is explored by image analysis, the nucleation site shape is examined by microscopic observation, and the relationship between the generated bubble size and the nucleation site shape was considered. A great correlation between them was indicated.

In this study, heat transfer characteristics of emulsion type thermal storage material which a phase change material is emulsified and dispersed inside water in a horizontal circular tube was investigated. It was found that Nusselt number of emulsions reasonably agreed with that of single phase fluid when its dispersoid keep solid or liquid phase during heating. On the other hand, Nusselt number of emulsions was higher than the values when dispersoid were melting. Furthermore, Nusselt number in lower side of circular tube was higher than that of upper side. This result indicates that secondary convection was induced by melting of dispersoid.

In the previous research, the heat transport experiment was performed by comparing the heat transport device with parallel tubes of thin-type, 1 mm in depth and 4 mm in width, and that of the conventional-type, 2 mm in depth and 2 mm in width, using water. The result was that the heat transport rate of the thin-type was significantly lower than that of the conventional type. This was due to the problem that when certain input of heat flux was exceeded, the working fluid in the evaporator evaporated completely, and a dry-out occurred, therefore the heat transport performance suddenly decreased. In this research, in order to solve this problem, 1-butanol, 2-butanol, 2-propanol and ethanol were used as the aqueous alcoholic solution for the working fluid in the thin-type test pieces. The heat transport experiment was performed at each concentration of aqueous alcoholic solution. Although the physical property values of those four alcohols are inferior to water, the aqueous alcoholic solution had a large influence on the internal flow and heat transport. 25% 2-Propanol had the highest heat transport rate.

Fire whirl, which is generated by swirling flow and buoyant flow, is sometimes observed in a big fire. It is a tornado-like vortex of flame and terrible disaster. In particular, the movement of fire whirl expands the damage of fires. However, there are many unclear points about the fire whirl movement. Most of previous studies on fire whirl movement are investigated on the line fires, but the movement direction is limited on a line. In the present study, the movement of fire whirl is investigated for the case with many possible movement directions, and the movement of fire whirl by side wind is elucidated.

Catalyst layer is the place where electrochemical reaction occurs in PEFC and strongly affects cell performance. Catalyst ink, which is the raw material of the catalyst layer, is known to be directly linked to the catalyst layer structure and performance. In this study, catalyst ink with different ethanol/water ratio was prepared, and the impact of solvent composition of the catalyst ink on the microstructure and the cell performance were investigated. As for structural analysis, cross-sectional structure and pore size distribution was measured. As for electrochemical characteristics, performance, electrochemical surface area and oxygen transport resistance of CLs were investigated. According to these analyses, it is possible to obtain high performance fuel cell by selecting an appropriate ethanol/water ratio.

This paper describes P – Q characteristics of small axial fans mounted in high-density packaging electronic equipment. The correct supply flow rate of the fans in high-density packaging electronic equipment cannot be predicted due to a deterioration of the fan performance. In this study, the P-Q characteristics of the small axial fan in the narrow enclosure, which the inlet flow of the fan was curved, by the enclosure was measured. Furthermore, the relationship between the fan performance and the flow pattern was evaluated through flow visualization. It is found that the supply rate of the fan is deteriorated when the distance between the fan inlet and the enclosure wall becomes narrower and the inlet flow pattern becomes complex by the generation of the pre-rotation flow.

The effect of sample thickness on its limiting oxygen concentration (LOC) was investigated for poly-methyl methacrylate and poly-carbonate with different thickness. For both materials, the LOC was different according to the thickness in microgravity regime although the sample was thin enough to be regarded as thermally-thin. This result implied that there was some heat conduction into the sample although the sample was thin. On the other hand, the LOC of PMMA was almost the same in kinetic regime for each thickness whereas the LOC of PC was different in kinetic regime; the thicker the sample was, the larger the LOC was. It was thought that the difference was resulted from the difference of their pyrolysis temperature.

This study aims to develop a novel water-cooled device that increases heat transfer performance while inhibiting the increase of pressure drop characteristic. The effectiveness of the pulsating flow, which is the unsteady flow that the supply flow rate is periodically changed likes a blood in the body of human beings, on the heat transfer enhancement have been reported from several researchers. The level of the heat transfer enhancement by the pulsating flow can be increased by the combination with the ribs. In this report, in order to optimize the dimensions of the ribs from the viewpoint of the heat transfer efficiency, an investigation of the flow pulsation phenomena around the rib was conducted through 2D-CFD analysis while changing the height of the rib. It was found that the level of the heat transfer enhancement was dependent on the rib height.

Using reactive ion etching, the fabrication conditions of pillar-structure with nm-class high aspect ratio were investigated on the silicon surface. The condensation behavior on the silicon surface with the nano-pillar structure with high aspect ratio was observed, and the spontaneous jumping phenomenon associated with droplet coalescence was observed. It was confirmed that the spontaneous jump phenomenon occurred on the silicon surface having a hierarchical pillar structure, and the occurrence frequency of the spontaneous jump was changed mainly due to the difference in the nucleation density of the condensed droplets.