Authorship：Lead author   Language：Japanese  

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/jtst.2018jtst0014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.proci.2016.06.180

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.expthermflusci.2014.11.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.1088/0960-1317/25/10/104004

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Other Link： http://stacks.iop.org/0960-1317/25/i=10/a=104004?key=crossref.bad5d8e3b3e75c3d0f17778afc37805c

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11322/tjsrae.31.207

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/mej.2014tep0047

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

We investigate diffusion and mixing in a microchannel by using luminol chemiluminescence (CL) to estimate the local chemical reaction rate. The degree of mixing in micromixers is generally evaluated from the deviation of concentration profiles measured by fluorescence from a uniform concentration profile. The degree of mixing measured by this method is a macroscopic estimate, which is inappropriate for investigating diffusion and mixing in microchannels. In this study, the luminol CL reaction is used to visualize and quantitatively measure local diffusion and mixing at an interface between two liquids in a microchannel. Blue CL is observed where luminol reacts with hydrogen peroxide at the mixing layer. Diffusion and mixing in a microchannel are investigated by sequentially measuring the CL and fluorescence. The experimental results are compared with the results of a numerical simulation that involves solving transport equations including the chemical reaction term. By calibrating the CL intensity with the chemical reaction rate estimated by the numerical simulation, the local chemical reaction can be quantitatively estimated from the CL intensity profile.

DOI： 10.1299/jtst.8.448

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaib.77.1688

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER  

This paper covers a wide spectrum of thermal flow behavior, including flow patterns, heat transfer, pressure drop, critical heat flux of flow boiling carbon dioxide at high pressure in horizontal mini-channels. The presented experimental data covers relatively wide ranges: tube diameters from 0.51 mm to 3.0 mm, mass flux from 80 kg/m(2)s to 900 kg/m(2)s, heat flux from 5 kW/m(2) to 40 kW/m(2), pressure/saturation temperature from 4.0 MPa/5.30 degrees C to 7.0 MPa/28.7 degrees C. The carbon dioxide at high pressure has small density difference between vapor and liquid and low surface tension, and shows a slightly different structure of the flow pattern from so far observed conventional two-phase flow with air and water and/or larger diameter tubes. So far proposed transition criteria of flow pattern are as a whole ineffective in the present range of experiment, and the discrete bubble model developed by the authors demonstrates its high potential in predicting flow patterns. The phase mal-distribution in the cross-section becomes rather significant beyond a critical Bond number, while less significant or almost axi-symmetric below the critical Bond number. This significant phase mal-distribution leads to the intermittent dryout at the upper wall of the tube, while below the dryout heat flux the boiling heat transfer is dominated by the nucleate boiling mode, being well predicted with conventional correlations. (C) 2010 Elsevier Masson SAS. All rights reserved.

DOI： 10.1016/j.ijthermalsci.2010.04.017

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

This paper describes the flow patterns of carbon dioxide two-phase flow at high pressure observed in horizontal minichannels ranging from 0.51 to 3.0 mm in diameter, together with the flow pattern maps and related boiling heat-transfer characteristics. The observed flow patterns are mainly classified into bubbly, slug, slug-annular, and annular flows, similar to conventional pipes, while phase stratification tendency is still significant even in a 1.0 mm tube, so that heat transfer at high pressure shows significant differences in the upper and lower walls, especially in 2.0 and 3.0 mm tubes. Such phase stratification with reference to heat transfer is roughly scaled by means of boiling number and Bond number. The newly developed simulation model by the authors for conventional-sized tubes is successfully applied to 2.0 and 3.0 mm pipes, but not to 0.51 and 1.0 mm tubes. This model suggests that thermal flow behavior at higher Bond number Bo than 8.2 is similar to that of conventional-sized tube, and cases less than Bo = 8.2 show minichannel behavior. The heat transfer in these minichannels is well-predicted with Schrock-Grossman type correlation with nucleate and forced-convective effects, while in larger tubes, e.g., 2.0 and 3.0 mm, the heat transfer is mainly dominated by nucleate boiling in the present experimental ranges. © 2010 by Begell House, Inc.

DOI： 10.1615/MultScienTechn.v22.i2.20

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC MECHANICAL ENGINEERS  

Viscous flows in a concentric annulus with rotating inner cylinder was characterized by Taylor-Couette flow. When the inner cylinder is replaced with a truncated conical rotor, the effect of imbalanced centrifugal force induces the meridional circulation flow with a single toroidal vortex. Under non-isothermal condition at cooling the rotor and heating the vessel wall, the flow pattern is drastically changed with the thermal conditions and the rotating speed. This paper describes the vortex flow-pattern transition and related heat transfer of the mixed convection in such a system. The temperature and flow field were visualized by means of thermo-sensitive liquid-crystal tracers. At the same time, the local heat transfer distributions on the cylindrical vessel wall were measured under a uniform heat flux by the electrically-conductive transparent film. Based on the experimental findings is described the interaction between the heat transfer and the thermal flow field during the unsteady mixed convection in the annular gap.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Increasing attention has been focused on carbon dioxide (CO2) heat Pump system where the temperature level is rather low, while the operating pressure is rather high. in this system, the density difference between vapor and liquid becomes rather small, which significantly affects flow patterns. Low tension and latent heat also have significant influence on two-phase flow patterns and heat transfer. This paper describes experimental and numerical investigation on flow patterns and heat transfer characteristics of boiling flow CO2 at high pressure in horizontal small-bore tubes ranging from 1.0 mm to 3.0 mm I.D. Even though the density difference is rather small at high pressure, phase stratification takes place, which leads to the intermittent dryout at the upper wall. So far developed discrete bubble model by the authors for vertical flows is modified so as to include horizontal flow mechanisms. The predicted flow patterns with this new model agree on the whole with the experimental observation. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijmultiphaseflow.2009.04.003

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/jpes.2.1074

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ZHEJIANG UNIV PRESS  

This study focuses on the fundamental characteristics of DME (Dimethyl Ether) combustion aiming at development of low-NOx combustion technology with flue-gas recirculation, FGR. The flue gas is recirculated into the combustion chamber to reduce the 02 concentration and to suppress the combustion gas temperature and the concentration Of 02, so that NO, emission is significantly reduced. The fuel gas recirculation at high mixing ratio, however, may lead to unstable combustion of conventional fuels, methane or city gas. On the other hand, DME has, however, very high potential of applicability of the flue-gas recirculation even at high mixing ratio because of its high burning velocity and low ignition temperature. Combustion tests were conducted with laboratory-scale 11kW combustor. The maximum FGR ratio is 8.5% at the initial air ratio of 1.5 with preheated diluted air about 600K. The NOx emission reduced to 13ppm at 0%-O-2, which corresponds to about 9% of NOx emission at FGR=0%. The stable combustion is sustained even in the low oxygen concentration by preheating diluted-air up to near the auto-ignition temperature of DME. Finally, an effect of the flue-gas recirculation on the NOx and CO emission is discussed with reference to the industrial-scale water-tube boilers.

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Language：English  

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC MECHANICAL ENGINEERS  

Increasing attention has been given to the development of low-NOx combustion technology for DME (Dimethyl Ether). The present paper describes a R&D study for water-tube boiler carried out in Kansai University and Hirakawa Guidam Co. Ltd. under the support of DME project from METI. The main problem arisen in DME use is a difficulty in an application of premixed flame owing to low ignition temperature and rather high burning velocity. Then the previously developed lube-nested combustor, i.e. water-tubes are installed in the empty furnace, becomes effective means to overcome such difficulty in realizing low-NOx combustion. This paper begins with a brief review of R&D study of the tube-nested combustor specifically designed for city gas. Then further development for DME-fired water-tube boiler is described.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC MECHANICAL ENGINEERS  

This study focuses on fundamental characteristics of DWE combustion, aiming at the development of low-NOx multi-ports burner. Multi-ports burner consists of a fuel-port and surrounding multi-air-ports. The strong re-circulation flow is formed by the small air jets, thus the short flames form a cluster on every burner unit so that the thermal NOx generation is significantly suppressed to a very low level. The NOx emission of the DME from the co-axial diffusion burner was over 130ppm beyond the level of the other fuels. On the other hand, NOx emission of DME from the newly advanced multi-ports burner was reduced to 60ppm at 0% O-2. With the help of the low-NOx combustion system, referred to as the tube-nested combustion, NOx emission of DME was further reduced to 20ppm at 0% O-2.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

An advanced-type compact water-tube boiler has been designed on the basis of the new concept of cooling flame by water-tube bank in the furnace, and is referred to as "tube-nested combustor". It realized drastic reduction in boiler size as well as in the NOx emission. In this present study, aiming at further improvement of boiler efficiency and reduction of NOx emission, the combustion characteristics in the furnace were investigated by using the test boiler of 0.5 t/h steam output. Experimental results indicated that the NOx formation was restricted in the narrow area close to the burner exit, and that the CO-concentration decreased drastically with the combustion gas stream through the tube-bank. These facts were closely related to the experimental evidence of the cross-sectional distribution of gas temperature being rather uniform owing to the agitation by the tube-bank. These experimental results verified the soundness of the boiler design and, in addition, gave relevant information on local combustion characteristics available for the R&D of the next generation tube-nested combustor.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

This study focuses on fundamental characteristics of DME (Dimethyl Ether) combustion, aiming at the development of low-NOx combustion. DME is one of the most promising new alternative fuels owing to its cleanness of the exhaust gas and wide applications. Combustion experiments using a diffusion burner were conducted for characterizing DME through the comparison with the results of LPG and 13 A-city gas. Experimental results demonstrated a high potential of DME for a boiler and a gas-turbine fuel. DME has a wide stable-combustion range compared with those of the other fuels. In this study, the concept of the low-NOx combustion, referred to as the tube-nested combustion, was applied to the DME combustion. This tube-nested combustor consists of tube banks to cool the burning flame leading to NOx reduction. Then, the NOx emission of the DME combustion was successfully reduced to a level suitable for practical applications.

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Language：English  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

Numerical and experimental studies of natural convection in a single-phase, closed thermosyphon were carried out, using a vertical, rectangular enclosure model. Two vertical plates, each 100 x 100 mm(2) in dimension, and placed symmetrically play the role of heat transfer surfaces. These symmetrical heat transfer surfaces are separated into three horizontal zones of equal height; the top and bottom thirds of these surfaces are the zones of, respectively, cooling and heating, the intermediate section being an adiabatic zone. Silicon oil is used as the working fluid. Variable parameters are the distance, D, between the two heat transfer surfaces, and temperature difference, DeltaT, between the heating and cooling zones. By changing both D and DeltaT, three regimes of natural convection flow; steady, quasi-two-dimensional, steady, three-dimensional, and unsteady flows were found in experiment. Converged solutions obtained by numerical simulation agreed well with experimental results with regard to the temperature and velocity of the fluid as visualized by means of thermo-sensitive liquid crystal powders. (C) 2002 Elsevier Science Inc. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

The effect of a single row of oblique pin fins on the end-wall heat transfer is investigated experimentally in the two types of pin fin arrangements. One is the "single row" arrangement, in which all of the pin fins are inclined toward the same direction and the other is the "cross row" arrangement, in which the pin fins are alternately inclined toward the upstream and downstream directions. Pin fins are inclined toward the streamwise direction from 0 = -60 degrees (upstreamwise) to +60 degrees (downstreamwise), where 0 is an angle between the axis of the pin fin and the normal of the endwall surface. The averaged Nusselt number of the oblique pin fins for the single row arrangement is smaller than that of the perpendicular pin fins, because the endwall heat transfer in the downstream region of the pin fins is not enhanced. In the case of the cross row arrangement of - 30 less than or equal to 0 less than or equal to + 30, the heat transfer shows almost the same value at the perpendicular pin fins. The cross row arrangement of 0 = 30 degrees shows about 25% less pressure loss than that of the perpendicular pin fins in spite of having almost the same averaged Nusselt number.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG  

Experimental and numerical studies of natural convection in a single phase, closed thermosyphon were carried out using a vertical, rectangular enclosure model. Only one vertical plate plays the role of heat transfer surface having 100 mm height and 100 mm width, and others act as the adiabatic wall made of transparent plexiglass. The heat transfer surface is separated into three horizontal zones with an equal height; top 1/3 and bottom 1/3 of the surface are cooling and heating zones, respectively and intermediate section is an adiabatic zone. Water is used as the working fluid. Variable parameters are distance D between the heat transfer surface and an adiabatic plate opposite to the heat transfer plate, and temperature difference DeltaT between heating and cooling zones. By changing both D and DeltaT, three regimes of the natural convection flow; quasi-two-dimensional steady, three-dimensional steady and unsteady flows are observed by means of thermo-sensitive liquid crystal powder and numerically simulated very well by solving a set of governing equations.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH SCI PUBL LTD  

Effect of a single oblique pin fin on the endwall heat transfer is dealt with in the present paper. Pin fin was inclined to the streamwise direction from theta = -60 degrees (upstreamwise) to + 60 degrees (downstreamwise) in every 15 degrees, where theta is an angle between the axis of the pin fin and the normal of the endwall. Thermosensitive liquid crystal was used to measure the local heat transfer coefficient on the endwall. When the pin fin was inclined upstreamwise at theta = - 45 degrees, the heat transfer coefficient on the endwall and the area of enhanced heat transfer became maximum. From the flow visualization by the smoke wire method, the horseshoe Vortices were observed around the pin fin when the pin fin was inclined upstreamwise. Especially, for the case of theta = - 45 degrees, it was found that the heat transfer was enhanced by the impingement of the wake flow on the immediate downstream endwall of the pin fin. However, for the case of the pin fin inclined downstreamwise, there was no effect on the enhancement of heat transfer on the endwall.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

Experiments were conducted to measure the local heat transfer on an endwall with pin fin array. Heat transfer behavior was examined for the cases of a single pin, a single row, in-line and staggered arrays having six streamwise rows. Thermosensitive liquid crystal film was used to measure the local heat transfer coefficient on the endwall. Neural network was applied for the color-to-temperature transformation of the thermosensitive liquid crystal. Local heat transfer on the endwall having a single row of pin fin was affected by flow acceleration between the pin fins rather than the horseshoe vortex around the pin fin. Therefore, the average Nusselt number exhibited a good correlation to the Reynolds number Re-max, which was based on the average velocity of the minimum flow area, regardless of the pin fin spacing. For in-line and staggered arrays, the average Nusselt numbers correlated with the Reynolds number Re-max decreased with the reduction of the pin fin spacing.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper concerns the condensation of carbon dioxide and its heat transfer on a vertical surface in the subcritical region. In this region, physical properties of carbon dioxide show marked temperature and pressure dependence. In particular, as the pressure increases and approaches the critical pressure, the difference in the properties of liquid and vapor, and surface tension approach zero. Therefore, condensate flow from natural convection decreases and configuration of condensation may differ from that at lower pressure. In this study, the configuration of condensation is observed and at the same time, condensation heat transfer is obtained by measuring the volume of condensate. Heat transfer is discussed in connection with the configuration of condensation.

DOI： 10.1299/kikaib.62.1118

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Venue：熊本  

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Venue：姫路  

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Venue：札幌  

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Venue：Tokyo JAPAN  

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Venue：TOkyo  

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Venue：Delft NETHERLANDS  

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Venue：Delft NETHERLANDS  

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Venue：東京  

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Venue：Fukuoka JAPAN  

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Venue：Osaka JAPAN  

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Venue：Osaka JAPAN  

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Venue：Hamamatsu JAPAN  

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Venue：Denver, USA  

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Venue：大阪  

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Venue：岡山  

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Venue：京都  

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Venue：京都  

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Venue：京都  

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Venue：京都  

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Venue：京都  

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Venue：長岡  

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Venue：Washington DC USA  

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Venue：東京  

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Venue：札幌  

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Country：Japan

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Country：Japan

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Country：Japan

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