Maromu Ohtaka

Central Research Institute of Electric Power Industry

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Hiroaki Watanabe

Kyushu University

Jun INUMARU

Central Research Institute of Electric Power Industry

Kazuhiko Kudo

Kyushu University

Akiyoshi Kuroda

RIKEN Center for Computational Science

Peng Li

University of Alabama at Birmingham

Haruo Matsumura

Kindai University

Hiroshi Kakota

Hiroshi Taniguchi

University of the Philippines Open University

Masahiro KURIHARA

Hitachi (Japan)

Kiyoshi Sakuragi

Central Research Institute of Electric Power Industry

Cooperative Institutions

Hokkaido University

Kyoto University

Central Research Institute of Electric Power Industry

Kyushu University

Energy Research Institute

Mie University

Jichi Medical University

University of the Philippines Open University

Kumamoto University

Tokyo Institute of Technology

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Improvement of analytical method on radiative heat transfer in nongray media by Monte Carlo method

Heat Transfer (1993)

Kazuhiko Kudo Hiroshi Taniguchi Akiyoshi Kuroda Maromu Ohtaka Hiroshi Kakota

An accelerated method is developed for radiative heat-transfer analysis in nongray media by the Monte Carlo method. Instead of deciding all the parameters of each energy particle used in the Monte Carlo procedure by a stochastic method, the wave number assigned to each energy particle is determined by a deterministic method in the present study. This change in the Monte Carlo algorithm reduces the computation time to one-ninth of the original time. To reduce the amount of iteration required to converge the temperature profile in a nongray media layer, an acceleration factor is incorporated to determine the new values of temperature in each iterational loop. The value of the acceleration factor is found to be related to the optical thickness of each media element. By using an appropriate acceleration factor, the amount of iteration is reduced to one-fourth of the original. Moreover, the total computation time becomes 1/36 of the original by the two improvements.

Thermal Radiation

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Citations (4)

O-401 Simultaneous production of bio-solid fuel and lipids from coffee grounds using liquefied dimethyl ether

Peng Li Kiyoshi Sakuragi Maromu Ohtaka Hisao Makino

Dimethyl ether

10.20550/jiebiomassronbun.9.0_32

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Citations (0)

Inception Criteria for Entrainment of Molten Slag Droplet in an Entrained Flow Coal Gasifier(Fluids Engineering)

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B (2009)

Jun INUMARU Hiroaki Watanabe Maromu Ohtaka Masami Ashizawa Kazuyoshi ICHIKAWA

Experimental studies using 2t/d and 200t/d coal gasifier were carried out to investigate the inception criteria for entrainment of molten slag droplet in an entrained flow coal gasifier. It was clarified that average gas dynamic pressure P_d and liquid film Reynolds number Re_f influenced strongly the phenomenon of entrainment of molten slag. The formula of the critical gas dynamic pressure P_ and the critical Weber number We_c=1.73, which could be applied to the large-scale gasifier, were obtained as inception criteria for the phenomenon. It was clearly shown that the flow pattern in the large-scale gasifier could be different from the smaller gasifier by means of numerical simulation analysis and that the critical velocity U_ decreases relatively along with the scaling-up of the gasifier.

Wood gas generator

Entrainment (biomusicology)

Slag (welding)

10.1299/kikaib.75.756_1576

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Citations (2)

3-8-3 Analysis Procedure of Road Distance based on the Fundamental Geospatial Data to Make Decision on Transportation of Thinned Wood

日本エネルギー学会大会講演要旨集 (2015)

Masahiro KURIHARA Haruo Matsumura Masanao Iuchi Maromu Ohtaka

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Parallelization of 3-D Radiative Heat Transfer Analysis in Non-gray Gas.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B (1993)

Kazuhiko Kudo Hiroshi Taniguchi Akiyoshi Kuroda Akeno Mochida Maromu Ohtaka

A parallel computational method is developed for the Monte Carlo analysis of radiative heat transfer in three-dimensional nongray gas enclosed by gray walls. The highly parallel computer AP1000 is used for the analysis. For the nongray gas, a mixture of water vapor and carbon dioxide is chosen as the absorbing-emitting medium. Three types of parallelization are studied: type (1), event parallelization; type (2), combination of event parallelization and algorithm parallelization, and type (3), memory-saving algorithm of type (2). When 512 cells are used, values of the speed-up ratios of 395, 430, and 370 are obtained for types (1), (2), and (3), respectively. The maximum number of elements which can be treated is increased from 1200 for type (1) to 140000 for type (3).

Thermal Radiation

10.1299/kikaib.59.3610

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Citations (0)

Study on Droplet Entrainment of High-Viscosity Falling Liquid Film

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B (2008)

Jun INUMARU Maromu Ohtaka Hiroaki Watanabe

An experimental study of counter-current annular two-phase flow of high-viscosity liquid and air in a large diameter pipe was carried out to investigate the inception criterion for entrainment of molten slag droplet in an entrained flow coal gasifier. Liquid film thickness was measured using a high-speed camera for 4 types of liquid with various viscosities and surface tensions. It was clearly shown that the measured average wave amplitude had a good correlation with the gas Reynolds number, and that the predicted critical gas velocity for droplet inception using new formula of wave amplitude had a good agreement with the experimental results under the condition of very low fluid Reynolds number (Ref≤10). The critical Weber number Wec=1.73 was obtained as inception criterion of droplet entrainment.

Entrainment (biomusicology)

Weber number

10.1299/kikaib.74.2279

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Citations (0)

Study on Droplet Entrainment of High-Viscosity Falling Liquid Film

Journal of Fluid Science and Technology (2010)

Jun INUMARU Maromu Ohtaka Hiroaki Watanabe

An experimental study of counter-current annular two-phase flow of high-viscosity liquid and air in a large diameter pipe was carried out to investigate the inception criterion for entrainment of molten slag droplet in an entrained flow coal gasifier. Liquid film thickness was measured using a high-speed camera for 4 types of liquid with various viscosities and surface tensions. It was clearly shown that the measured average wave amplitude had a good correlation with the gas Reynolds number, and that the predicted critical gas velocity for droplet inception using new formula of wave amplitude had a good agreement with the experimental results under the condition of very low fluid Reynolds number( Ref ≤10). The critical Weber number Wec =1.73 was obtained as inception criterion of droplet entrainment.

Entrainment (biomusicology)

Weber number

10.1299/jfst.5.169

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Citations (3)