In this study, we focused on the strong adhesion of ice to the metal surface, and examined the possibility of adapting to the “freezing chuck”. The freezing chuck is a technology to fix the work piece to the work table by freezing water. In this study, two kinds of anionic surfactant-pure water mixture were frozen on the surface of the copper plate constituting the DC condenser, and the ice adhesion force was measured while changing the applied voltage to the DC condenser. From the results of ice adhesion, the effects of changes in the properties of the surfactants and the applied voltage on the ice adhesion ware compared.

The authors group focused on adsorption of non-ionic surfactant molecules to an interface and examined active control of supercooling degree. Then it was clarified that it can be actively controlled supercooling degree by variation of surfactant concentrations. In this paper, an amphoteric surfactant that exhibit cationic property was used by fixing the pH of the surfactant-pure water mixture (surfactant mixture) for the purpose of further improving the controllability of the supercooling degree. And then The supercooling degree of the surfactant mixture was measured by varying of surfactant concentration. And the characteristics of the supercooling degree when an amphoteric surfactant that exhibit cationic property was used were clarified by comparing with the results when a non-ionic surfactant was used.

In recent years, in-vehicle electrical components have been increasing in performance and density. For this reason, the temperature gradient of the board used in the ECU has become larger. A thermistor is often used as a heat sensor for electronic equipment, but the standard guarantees only a uniform temperature condition A temperature difference began to occur between the thermistor electrodes, and a temperature greatly deviating from the original temperature was detected. In this paper, first, it was clarified how the thermistor shows the error due to the temperature difference between the electrodes. It shows that accurate temperature detection is possible by modeling with VHDL-AMS.

We investigated prediction accuracy of an identification method using sensitivity analysis of CFD software developed by us named as “FlowDesigner”. We applied the identification method to predict the thermal conductivity of TIM with 0.1mm thickness set in between upper and lower base plates by using the measured temperature of targets located in the center of both upper and lower base plates. We clarified that the thermal conductivity of TIM was able to be predicted as 0.2W/m·K within prediction error band of ±10% under the condition of targets temperature measurement error was in between -1 and +0.8 K and heat flow ratio of in-plain direction against thickness direction was in between -1 and +0.8.

To reduce the weirght of thermosiphon, we focus on the aluminum heat transfer surface for saturated pool boiling. Considering the matching of aluminum surface with working fluid, fluorine refrigerant HFE7000 is used as a working fluid. And, we have used two types of heat transfer surface (smooth surface and curl-skive fin surface). Absolute pressures cited are 0.10MPa, 0.12MPa, 0.14MPa, 0.16MPa, respectively. As a result, under high pressure, boiling curve shows high performance at lower heat flux area compared with that of atmospheric pressure, regardless of type of heat transfer surface. And, under 0.10MPa with heat flux of 120kW/m2, degree of superheat of curl-skive fin surface is about 0.5times compared with that of smooth surface. Furthermore, under 0.16MPa with heat flux of 120kW/m2, degree of superheat of curl-skive fin surface is about 0.4times compared with that of smooth surface.

This paper describes dynamic transition behavior of single buoyant flames and interacting twin jet flames subjected by buoyancy. Single buoyant jet flame exhibits two modes of periodic flame behaviors; such as (axisymmetric) varicose and (asymmetric) sinuous modes. Similar behavior is observed when twin jet flames interacted at certain separation distance. Experimental observation of time-sequential imaging of thermal layer during this periodic event was made and data analysis of flame dynamics was proceeded to summarize their behavior and find the key parameter to determine its characteristics. The potential mechanism to lead the mode transition is discussed.

The wall chemical effect caused by radical adsorption and recombination on the wall surface under flame-wall interaction is investigated by using an atmospheric-pressure non-equilibrium plasma jet (APPJ). To evaluate radical generation in the APPJ, radical chemiluminescence are obtained. It is found that OH and H radicals are successfully formed and issued in open space when water vapor is added into the Argon/Helium APPJ. Then, the OH and H jets are irradiated onto quartz and alumina walls. The reactivity of radical on the quartz wall is decreased with increase in the wall temperature T_w, showing that radical desorption is promoted at higher T_w.

Coaxial jet mixing and combustion are actively controlled through manipulation of the vortical structures and the associated mixing with twelve micro jet actuators installed on the annular nozzle. The different azimuthal mode examined here are the fundamental axisymmetric mode and the alternative mode. In the alternative mode, six adjacent micro jets are driven out-of-phase with the other six. The alternative mode provides a phase difference in the generation of the left and right side vortices and avoids interference between these vortices, so that larger vortices are developed if compared to the axisymmetric mode. The effect of the different azimuthal modes on the mixing and the exhaust gas characteristics are discussed.

The interface between stearyl trimethylammonium (STAC) and palmitic acid (PA) vibrates spontaneously because of chemical nonequilibrium. This dynamic motion of the interface is often referred as “blebbing,” and explained as the gel formation and the change in its thickness with time. In this paper, the influence of gel formation by the chemical reaction and blebbing at the interface on the displacement process has been investigated in Hele-Shaw cells. Gel formation at the interface stabilizes the fingering with an increase in the injection rate, in contrast to normal viscos fingering associated with the viscosity ratio. At the concentration of 20 mmol/L of PA and the 20 mmol/L of STAC, the high sweep efficiency was achieved due to suppression of the fingering. In injected aqueous phase, unique residual oil blobs which grow from the web-like structure at the interface was found.

In this study, the characteristics of fingering of miscible fluids associated with gel formation reaction between skimmed milk and citric acid solution have been studied. Mixing of skimmed milk and citric acid solution leads to form viscoelastic gel at interface of two fluids causing the instability of interface. we observed this instability in a Hele-Shaw cell. We changed the injection rate and citric acid solution concentration, and observed flow pattern of each condition. At high citric acid solution concentration, mixing of two fluids is suppressed and unique fingering patterns appear. With an increase in the gap width, the width of fingers widens. We found distinctive structure like connected bubbles appears on the fingers and considered the relation between the structure and film thickness of interface gel. Last, we measured the film thickness of interface gel over time and calculated diffusion coefficient from that data.

This paper describes conjugate radiation-convection-conduction simulation of a porous solar receiver irradiated by beam-down concentrated light. Simulation was made for three cases where cell sizes and porosity were changed in each of two steps. It was demonstrated that receiver efficiency increased when cell size decreases and porosity increases. Heat transfer losses were analyzed to probe mechanisms of receiver efficiency enhancement. It was found that the thermal radiation losses were attenuated when cell size decreases or porosity increases. The attenuation of thermal radiation increased convection heat transfer by air stream to enhance receiver efficiency.

Diffusers are extensively used in many industrial aspects. So, diffusers with high efficiency are desired under both spatial and cost’s limitations. In our previous studies, we proposed a flow deflector inside the diffuser-part of an automotive catalytic converter, in order to reduce energy loss and to improve thermal uniformity. In this study, we experimentally and numerically investigate the influence of the downstream substrate upon the effectiveness. As a result, it is revealed that the flow deflector is effective for diffusers as well as catalytic converters. By computation, we have shown the flow inside the diffuser with the flow deflector.

Regarding semiconductor package models used for thermal analysis of electronic devices. For example, the DELPHI model is specified in JEDEC JESD15-4, but the detailed model has no standard. Therefore, model abstraction depends on the manufacture of the semiconductor device you are creating. Users using it cannot compare and validate their models under the same conditions. On the other hand, semiconductor device manufacturers need to hide as much as possible internal structures and materials that are competing fields. In this research, in order to solve this subject, the parameter that influences a thermal-analysis result was specified, and the highly precise JTAM model (JEITA Thermally Accurate Model) was developed by the minimum input. This improves the distribution of thermal analysis models and creates an environment where users can easily compare parts.

In this study, HFO (Hydrofluoroolefin)-based insulating mixed refrigerant is proposed for liquid cooling systems of electronics. To improve the cooling performance, the mixing solvents and their mixing ratios were determined by optimizing thermophysical properties such as thermal conductivity and specific heat of the mixed refrigerant. The optimized properties were obtained by employing the Digital Annealer (DA), which is a new technique for solving combinatorial optimization problems at a high speed using digital circuits. It was experimentally verified that the heat transport performance of the liquid cooling system incorporating the proposed mixed refrigerant can improve by 12% or more compared with the base HFO. This work demonstrates the possibility of applying DA to the fields of chemical and thermal engineering.

The purpose of this study is to observe TBAB hydrate crystals growing on a cooling surface, and to reveal the effect of initial aqueous solution concentration and degree of supercooling on crystal shape and growth rate．From the observation, we confirmed that the crystal shape of TBAB hydrate differed depending on the initial aqueous solution concentration and the degree of supercooling. Additionally, we confirmed that the growth rate did not change significantly with the initial aqueous solution concentration and was almost proportional to the power of the degree of supercooling.

This study is the research and development of the tubeless boiler with hydrogen combustion. This boiler is structured by spraying water into the oxy-hydrogen diffusion combustion gas. Steam is produced by the reaction of the oxy-hydrogen combustion and the spray evaporation, thus, the water tubes used in the conventional boiler are not required to produce the superheated steam. Oxygen is diluted by the steam recirculation from the exhaust gas to suppress the combustion speed. This paper reports the development tubeless boiler of 5kW heat release rate with 80g/min steam generation with the intermitted spraying evaporation and by the Diesel jet nozzle.

To enhance the performance of thermosiphon, boiling heat transfer under low pressure is examined experimentally. We focus on the size effect of heat transfer surface. Thus, four kinds of pyramid type heat transfer surface and six kinds of dimple type heat transfer surface with size of 25mm×25mm are used in this experiment. Optimal size of pyramid surface is pitch of 2.5mm. This is the same result with 10mm×10mm surface. Therefore, there is no size effect for optimal pyramid type except degree of heat transfer enhancement. On the other hand, optimal diameter of dimple surface is 2.0mm~3.0mm. And, dimple surface shows higher performance with narrower pitch. Performance of pyramid 2.5mm type is higher by about 1.78 times compared with that of dimple pitch 4.0mm type at the heat flux of 100kW/m².

We conducted an experimental study on gas-liquid distributions of refrigerant flow in multi-pass channels with vertical headers and horizontal multiport flat tubes, which simulated parallel-flow type evaporators for air conditioners. In particular, the influence of a spraying nozzle, which was inserted in the header to improve the liquid-distribution uniformity, on the pressure loss characteristics of the channel was examined. We measured pressure losses of the channel and each branch tube, and pressure distributions in headers. The pressure loss of the nozzle amounted to 90 – 95% of the total pressure loss of the channel. The pressure loss coefficient of the nozzle could be correlated by Reynolds numbers defined with the superficial velocities of gas and liquid at the nozzle outlet.

In the present study, we conducted nonequilibrium molecular dynamics simulations in order to investigate influences of the adsorption layers of the liquid around a nanoparticle on the effective thermal conductivity of liquid with nanoparticle suspension. We adopted liquid systems with nanoparticle suspension between two solid walls and obtained the effective thermal conductivity based on the Fourier’s law imposing a temperature difference between the two solid walls. Contributions of the adsorption layer to the effective thermal conductivity were investigated quantitatively, and the results showed that the thermal conductivity in the adsorption layer increases with the increase of the interaction intensity between the nanoparticle and the liquid.

This study is a basic research to enhance heat transfer between two immiscible liquids by dropping a water droplet between a wire electrode and a cylindrical electrode in silicone oil and applying an electric field. The purpose of this paper is to clarify a part of the motion behavior of the water droplet under non-uniform electric field. As a result, the water droplet apparently reciprocated between a pair of the electrodes, in case of a wire and a cylindrical electrode under the Coulomb force. The droplet stopped at a distance from the wire electrode. At that time, when a part of the water droplet extended and contacted the wire electrode, charge exchange occurred.

Thermal management has become a big problem with the increasing performance and miniaturization of electronic devices. In particular, in-vehicle electronic devices are not only subjected to high temperatures but also have to sustain impact loading, thus there has to be a gap between the heat-generating component and its enclousure. As such, there is a need to improve the heat transfer characteristics of heat dissipating materials which have adequate elasticity. In this study, a Thermal Interface Component (TIC) was prepared by impregnating an open-cell type copper foam with a hardenable gap filler, and the effective thermal conductivity was measured. We also compared the effective thermal conductivity culculated with existing models and previously measured data.

It is important to understand the liquid-vapor phase interface shape developed by vapor generation on the porous body for the performance prediction of the loop heat pipe. A visualization experiment device, in which a porous body is immersed in the working liquid and its top surface is in contact with a viewing windows with a pore, was constructed to observe the vapor-liquid interface behavior between the porous body and the wall. Drainage process in which vapor invades into the porous body and grows was observed using different porous body materials, working fluids. The liquid-vapor phase interface shape was evaluated from displacement pattern, saturation, and vapor-liquid interline length.

This paper describes new compact thermal model for microprocessor packages, which can be used as a component of thermal network and three-dimensional computational fluid dynamics simulation. First, new compact thermal model is briefly introduced as a thermal network with three thermal resistances. Second, the compact thermal model creation and temperature prediction example by a thermal network with the compact thermal model is explained. And finally, methodology to implement the compact thermal model into three-dimensional computational fluid dynamics simulation tools is investigated.

The thickness characteristics of a liquid film formed during the liquid column oscillations within pulsating heat pipes were experimentally investigated. In order to simulate the flow phenomena, the liquid column was oscillated sinusoidally under various oscillating conditions in a horizontally located circular glass tube with an inner diameter of 2 mm. The average thickness of the liquid film formed due to the liquid column oscillations on the channel wall was determined by comparing the oscillation amplitudes of the tip of the liquid column obtained with and without the liquid film. According to the experimental results, empirical correlations are proposed for the average liquid film thickness.

This paper introduces D²ELPHI (Dynamic DELPHI), a transient thermal network model for semiconductor packages that has been standardized and published by JEITA (ED-7800). This model is supposed to be used in the time order of 1msec or more. If an assembly manufacturer wants to predict junction temperature of a semiconductor package by computer simulation for an electronic device, a thermal model of that package is required. However, the model cannot be easily created by themselves and must be obtained from the package manufacturer. Thermal resistance network model DELPHI, standardized by EU manufacturers in the mid-1990s, is limited to use for steady-state simulations. The D²ELPHI model is based on the DELPHI model and includes heat capacities to support transient simulation. When setting heat capacities of D²ELPHI model, it is important to reflect heat path of the target package.

This paper presents effect of filling ratio on the transient and steady thermal performance for a long vertical heat pipe. This heat pipe consists of three sections: cooling section, heating section and sub-heating section. Sub heating section helps to increase the flow volume of working fluids and prevents lack of it in heating section during start-up. The experimental results show increasing fill ratio causes cyclic temperature variation in steady and transient performance and prevents temperature overshoot in transient performance.

This study measured the critical heat flux on a bottom surface for bottom and volume heated particulate beds, where small spherical metal particles were placed on a 75mm diameter heating surface and internally heated by induction heating. The data were obtained by varying the particle size and the volumetric heated rates in the particulate beds. The CHF on the bottom surface decreases with decreasing the particle size and is unaffected by the volumetric heated rates of the particulate beds. The previously proposed CHF correlations, which were derived based on the assumption that the CHF is triggered by hydrodynamic phenomena of liquid and vapor flows through the particulate beds, are not applicable to the CHF for bottom and volume heated particulate beds.

In this study, experiments were carried out using a 1-turn pulsating heat pipe having a visualization flow channel. Deionized water, ethanol and ethanol aqueous solution were used as the working fluid. As a result, it was found that by using ethanol aqueous solution, the effective thermal conductivity increased compared with deionized water and ethanol. Vapor pressure, vapor temperature and wall temperature were measured. Liquid column oscillation in the channel was recorded by a high-speed video camera. Based on these measurements, the effects of working fluids and inclination angle (horizontal, vertical) on the liquid column oscillation and heat transport characteristics were discussed.

The vapor-liquid interface behavior in the loop-heat-pipe (LHP) capillary evaporator is related to the thermal performance, but has not been sufficiently investigated. In this study, a visualization evaporator close to a practical environment is constructed using a sapphire tube, and the vapor-liquid interface behavior at the contact surface between the wick and casing is observed. After nucleate boiling take place at middle heat flux, the vapor phase region generated and was scattered throughout the wick, and the heat-transfer coefficient increased.

Paramagnetic fluid is weakly attracted toward a magnet depending on the inverse of the absolute temperature. When non-uniform temperature field is formed in an enclosure, colder fluid receives stronger attractive force than hotter fluid. This characteristic can be used in thermal flow control. In this study, numerical simulation of Rayleigh-Bénard convection under a magnetic field from permanent magnets have been performed by the lattice Boltzman method (LBM). The working fluid is assumed as incompressible paramagnetic fluid of which Prandtl number is 13.0. Buoyancy and magnetothermal forces in the LBE are considered by using the Boussinesq approximation. It is found that the shape of steady convection roll cell is affected by the magnetothermal force and the corresponding local heat transfer is enhanced.

It is important that people make the life comfortable. One of the methods for human comfort in living environment is to utilize clothing. The microclimate of clothing is a small gap space between the human body and clothing. Since the clothing microclimate greatly influences the comfortability of a human during when wearing clothing, weinvestigated the air flow and heat transfer characteristics in clothing microclimate. Normally parameters such as air temperature, air humidity and air flow are measured. Among them, air flow would be most important for heat and humidity dissipation, therefore, we mainly focused on investigated air flow characteristics in clothing microclimate of simulated human body by the Particle Image Velocimetry (PIV) analysis. In this study, the results of PIV analysis showed that the air flows upward in the gap because of the natural convection of the human body. The air velocity and heat transfer in the clothing microclimate were influenced by the opening rate. We finally clarify a mechanism of air field formation in clothing microclimate.

In recent days, thermal design engineers of electronic devices in Automotive industry and electrical industry need to analyze a complex geometry consisting with a hundred/a thousand parts for thermal as well as structural analysis simulation. The modelling method has been achieved "Digital Twin" concept, and that simulation software are thus significantly required high performance gridding and processing capabilities. This paper describes the current trend of thermal simulation tools for thermal design engineer with some examples as well as the latest Computational Fluid Dynamics (CFD) features and demands are shown.

In this study, a heat balance model is developed to evaluate the heat transfer phenomena in single PEFC cell operated at high temperature such as 90℃. The impact of MPL on the temperature distribution under the high temperature operation condition was investigated. As a result, it is revealed that the temperature on reaction surface rises from the inlet to the outlet of the cell by approximately 1 – 2℃ at T_ini = 80, 90℃ with MPL, while it becomes relatively flat at T_ini = 100℃. The temperature for relative humidity of anode of 40 %RH and cathode of 40 %RH is the highest among all relative humidity conditions irrespective of T_ini.

The role of water cooling is important in the steel making process. In order to obtain a desired material, temperature control in the water cooling zone, which is the final stage of the manufacturing process of thin plates and thick plates, is important. The quench point is one of the factors that determine the cooling characteristics of steel. Because the quench point is influenced by many parameters, the mechanism for determining the quench point remains unclear. In this study, we observed the elementary process of cooling using multiple droplet temperatures. The influence of droplet temperature on cooling was investigated.

The present study experimentally investigated the thermal response of heat storage made of porous silicon carbide, for comparison with dense alumina, in a simple system in which three heat storage were vertically aligned in a square duct. Those heat storages were heated with high-temperature air (900℃) and then cooled with room-temperature air. The temperature histories of “upstream and downstream air” and “the center and surface of each heat storages” were measured by a K-type thermocouple. As a result, porous silicon carbide heat storage bodies at all position showed low Biot number and higher thermal response than dense alumina heat storage.

From the viewpoint of environmental and energy problems, there is a need to improve the thermal efficiency of internal combustion engines. We have developed a single-layer heat flux sensor using MEMS technology to quantitatively evaluate the cooling loss inside the engine. However, while this sensor succeeded in capturing high-speed heat flux fluctuations, it is not capable of measuring the DC component due to the lack of ability to measure the temperature at back surface of the sensor substrate. In this study, we proposed a double-layer thin film RTD sensor that measures the heat flux including the DC component. In this report, verifying the validity of proposed method, we conducted a preliminary experiment of the measurement of the wall heat flux using a collision jet with a commercially available Pt RTD sensor. We present the results of comparison with the single-layer sensor.

Lithium ion battery cells are installed in a limited volume to ensure the high energy density as the battery module or pack. Each battery temperature is varied by the position to be installed in the module or pack. The generated heat by cell is formulated to the sum of battery reaction heat and Joule heat⁽⁶⁾. Through the cell heat and temperatures, the electrical equivalent circuit model⁽⁶⁾ is directly connected to a heat circuit(3) to describe a structural heat transfer for the module. This paper studies a heat transfer path from the cell coil as an anisotropic heater to supplies in the module, and the out of module by utilizing the thermal and electrical circuit. This paper investigates the heat transfer types for circumstances of cells and modules, and the simulation result is shown.

In this paper, we examined the heat transfer enhancement of a pulsating pipe flow generated by opening and closing the electric valve. The temporal variation of the pressure loss was evaluated by measuring temporal variations of the pressure difference and the flow rate in the pipe. The pressure loss defined here means the loss caused by viscous dissipation, which can be calculated by subtracting the power required for acceleration/deceleration from the power required to drive the flow. As a result of the pulsation between Re = 900 and 9000, heat transfer was enhanced by 16-42% by applying the pulsation under the condition at the same average Reynolds number. Also, under the condition of the same average pressure loss, the heat transfer enhancement due to the pulsation was small, but there was a tendency to enhance the heat transfer by 3-10% at the longest valve opening time of 3.4 s in this pulsation condition.