DOI： 10.1016/j.ijheatmasstransfer.2022.122950

Web of Science

Language：Japanese   Publisher：The Heat Transfer Society of Japan  

This paper describes a study on 10 kW-class Loop Heat Pipe (LHP) which is a two-phase heat transfer device. In this study, the 10 kW-class LHP was designed, fabricated, and tested. Condenser was cooled under stagnant water condition and forced water convection, and we evaluated steady state temperature. It was experimentally confirmed that this LHP can transport 9.5 kW heat in the steady state under stagnant water condition, a temperature of heater blocks being within 300°C. Then the thermal resistance at 9.5 kW was 0.006 °C/W. Finally, the steady experimental results were compared with calculation results and the maximum absolute error of heater blocks temperature was 22°C.

DOI： 10.11368/tse.30.13

CiNii Research

Language：English  

DOI： 10.1016/j.enconman.2021.114081

Web of Science

Language：Japanese   Publisher：THE JAPANESE SOCIETY FOR MULTIPHASE FLOW  

<p>This paper describes the design, fabrication, and the heat transfer performance of a miniature loop heat pipe (mLHP) aiming for cooling a small and high heat flux devices. For the design process, a one-dimensional numerical model was developed. Based on the numerical model, an mLHP was fabricated. The mLHP comprises an evaporator (15×16×t3 mm^₃), a condenser (12×12.5×t2 mm³) and transport lines (O.D.=1.6 mm, L=100 mm). The mLHP uses Shirasu porous glass (SPG) as a wick and is mainly made of stainless steel. The heat transport performance was investigated in horizontal attitude, anti-gravity (top heat mode) and gravity-assisted (bottom heat mode) with working fluid of water. When the condenser was dissipated by natural air convection, the mLHP performed 5-W (20-W/cm²) heat transport at 170-℃ heat source temperature in horizontal attitude. The thermal resistance was 7.9℃/W. In the bottom heat mode, the lowest thermal resistance of 2.6℃/W was obtained due to the gravity assist. Additionally, the mLHP was tested under the condition that the evaporator side was kept horizontal but the condenser side was bent upwards by 90 degree around the middle of transport lines. Consequently, in low heat load condition the bent mLHP showed the same performance with the bottom heat mode, but shifted to the horizontal mode as the heat load increased. Thus, the heat transport performance was comprehensively investigated for considering various uses.</p>

DOI： 10.3811/jjmf.2021.021

CiNii Research

Language：English  

DOI： 10.1016/j.applthermaleng.2020.116169

Web of Science

Language：English  

DOI： 10.1063/1.5143561

Web of Science

Language：English  

DOI： 10.1016/j.enconman.2019.112431

Web of Science

Language：English  

DOI： 10.1016/j.ijheatmasstransfer.2019.01.121

Web of Science

Language：Japanese   Publisher：The Heat Transfer Society of Japan  

A loop heat pipes is a highly efficient two-phase fluid loop utilizing latent heat. In recent years, due to the miniaturization and high performance of electronics, the heat density of the equipment has been increasing remarkably, so thermal demand is increasing in the terrestrial field. In this study, we developed a high heat flux loop heat pipe aiming to be mounted in electronics and conducted experiments under an atmospheric environment. It shows that heat transport is performed up to a maximum heat flux of 42.5 W/cm2 at a heat transport distance of 400 mm, and it is confirmed that it operates normally in three positions of horizontal, top heat, and bottom heat.

DOI： 10.11368/tse.27.25

CiNii Research

Language：English  

DOI： 10.1016/j.ijheatmasstransfer.2016.09.104

Web of Science

DOI： 10.1016/j.ijheatmasstransfer.2014.04.041

Web of Science

DOI： 10.1080/00223131.2013.773161

Web of Science

DOI： 10.1080/00223131.2013.750055

Web of Science

Language：English   Publisher：The Japan Society of Mechanical Engineers  

The measurement error when calculating the bubble volume by using image analysis was estimated by taking a single bubble of known volume (0.02 × 10<SUP>-6</SUP>-2.00 × 10<SUP>-6</SUP> m<SUP>3</SUP>, or the volume equivalent diameter of 3.37-15.63 mm) and using a stereo visualization system with a high-speed camera. Previous studies calculated the bubble volume from images observed by the one-way photography method using the short-axis rotation of the bubble shape, which was assumed to have short-axis symmetry for approximation of the bubble shape to a spheroid. This study clarified the measurement accuracy for bubble volumes using one- and two-way image analysis methods. The results showed that the one-way method tended to underestimate the bubble volume when using the long-axis rotation, which approximates the bubble depth diameter by using the short-axis diameter, and overestimate the volume when using the short-axis rotation, which approximates the bubble depth diameter by the long-axis diameter. The measurement accuracy of the calculated bubble volume degraded for large bubble volumes. A one-way volume measurement method using a correlation equation was developed, and its accuracy was equivalent to the measurement accuracy of the two-way method using stereo visualization.

DOI： 10.1299/jfst.8.30

CiNii Research

Language：English   Publisher：The Japan Society of Mechanical Engineers and The Heat Transfer Society of Japan  

For predicting the void fraction distribution in subcooled flow boiling, it is necessary to measure the interfacial heat transfer coefficient—which determines the amount of condensation rate of vapor bubble—with high accuracy. In this study, the relationship among the bubble number distributions, void fraction, bubble collapse rate and phase change rate was clarified through measurement of the average interfacial heat transfer coefficient using image analysis under the condition of forced convectional subcooled flow boiling. The bubble number distributions were measured by translating bubble images observed by a high-speed camera. The bubble collapse rates were obtained by the process of bubble number. The obtained bubble collapse rates were possible to predict the decrease rate of the void fraction in low subcooling condition with high accuracy. The average heat transfer coefficient was shown to depend on the interfacial area concentration, via calculation of the average interfacial heat transfer using the obtained bubble number distribution. The developed experimental correlation of the interfacial heat transfer with the interfacial area concentration was compared with the measured value, and the interfacial heat transfer using the developed correlation equation corresponded to the measured one. A comparison with previous correlation equations for interfacial heat transfer coefficients and consideration of the bubble number distribution confirmed the applicability of the experimental correlation of the interfacial heat transfer coefficient to a boiling channel.

DOI： 10.1299/jtst.8.74

Web of Science

CiNii Research

Language：English   Publisher：The Japan Society of Mechanical Engineers  

In the joint research and development of treatment systems of cooling water for cutting asphalt pavement surface with our authors' group, the liquid-solid separation technology by flocculating and settling technology, and the flocculants for the use of systems were developed. In this paper, the developed flocculating and settling technology and the flocculants are discussed first. Next, the demonstration tests of decontamination technology on the contaminated water in swimming pools in an elementary school located at Motomiya City, Fukushima Prefecture had been conducted by use of the stationary purification system of contaminated water and the flocculants compounding with or without iron ferrocianide developed by the preliminary test. It was clarified from the results that ionized cesium (Cs) rarely exists in the stagnant water in pools, ponds, lakes and so on at the time when nine months have passed since Fukushima Dai-ichi nuclear power plant accidents. Further, it is necessary to use the flocculants compounding iron ferrocianide in the case where ionized Cs exists in water. From the above-mentioned results, the following problems were pointed out: One problem was cyanide dissolution in the purified water and the other one was the dissolution from the dehydration sludge. Finally, the high-performance mobile purification units of contaminated water which is capable for carrying with trucks have been developed, and the demonstration test was performed in Minami-soma City, Fukushima Prefecture to purify the contaminated water in a pond and generated by the high-pressure water washing in a Public Hall. From the test results, it was made clear that the dehydration sludge separated by liquid-solid settling of the contaminated water of around 1,000Bq/<I>l</I> became a high radiation dose of about 185,000Bq/<I>l</I>.

DOI： 10.1299/jpes.6.412

CiNii Research

DOI： 10.3327/jnst.48.135

Web of Science

DOI： 10.3327/jnst.45.160

Web of Science

Language：English   Publisher：The Japan Society of Mechanical Engineers  

The purpose of the study is to experimentally investigate driving mechanism of major instabilities simulated in a natural circulation experimental loop, under a predetermined range of system operating pressure and inlet subcoolings. Pressure range of 0.1 up to 0.7MPa, input heat flux range of 0 up to 577kW/m², and inlet subcoolings of 5, 10 and 15K respectively, are applied in the experiments. The objective of the study is to formulate a rational startup procedure, in which major thermohydraulic instabilities can be detected and prevented. The study clarifies that four (4) kinds of thermohydraulic instability might occur even up to a higher pressure of 0.7MPa. The instabilities' sequence is as follows: (1) geysering induced by condensation accompanied by flashing, (2) oscillation induced by hydrostatic head fluctuation, (3) density wave oscillations, and (4) flashing accompanying those instabilities. The experiments confirmed that the geysering region gets narrower and suppressed with the increased system pressure. With chimneys, natural circulation can be achieved reliably and more easily. However, the flashing in the chimney cannot be avoided at low system pressure. Stable two-phase natural circulation can be established if the system pressure is increased beyond 0.7MPa, after the high frequency density eave oscillation thoroughly suppressed. The experiments were analyzed based on frequency domain of each instability phenomenon.

DOI： 10.1299/jsmeb.47.277

Web of Science

CiNii Research

DOI： 10.3327/jnst.40.918

Web of Science

Event date： 2023.5

Language：Japanese  

Venue：福岡   Country：Japan