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Coupled simulation of BES-CFD and performance assessment of energy recovery ventilation system for office model

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Journal of Central South university 2012年第3期19卷 633-638页

作者： Yunqing FAN T.Hayashi K.Ito interdisciplinary graduate school of engineering Science(IGSES) Kyushu University

Thermal comfort and indoor air quality as well as the energy efficiency have been recognized as essential parts of sustainable building assessment. This work aims to analyze the energy conservation of the heat recovery ventilator and to investigate the effect of the air supply arrangement. Three types of mixing ventilation are chosen for the analysis of coupling ANSYS/FLUENT （a computational fluid dynamics （CFD） program） with TRNSYS （a building energy simulation （BES） software）. The adoption of mutual complementary boundary conditions for CFD and BES provides more accurate and complete information of indoor air distribution and thermal performance in buildings. A typical office-space situated in a middle storey is chosen for the analysis. The office-space is equipped with air-conditioners on the ceiling. A heat recovery ventilation system directly supplies flesh air to the office space. Its thermal performance and indoor air distribution predicted by the coupled method are compared under three types of ventilation system. When the supply and return openings for ventilation are arranged on the ceiling, there is no critical difference between the predictions of the coupled method and BES on the energy consumption of HVAC because PID control is adopted for the supply air temperature of the occupied zone. On the other hand, approximately 21% discrepancy for the heat recovery estimation in the maximum between the simulated results of coupled method and BES-only can be obviously found in the floor air supply ventilation case. The discrepancy emphasizes the necessity of coupling CFD with BES when vertical air temperature gradient exists. Our future target is to estimate the optimum design of heat recovery ventilation system to control CO2 concentration by adjusting flow rate of flesh air.

关键词： building energy simulation computational fluid dynamics (CFD) FLUENT TRNSYS energy saving

Effect of lower bainite/martensite/retained austenite triplex microstructure on the mechanical properties of a low-carbon steel with quenching and partitioning process

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International Journal of Minerals,Metallurgy and Materials 2016年第3期23卷 303-313页

作者： Wan-song Li Hong-ye Gao Zhong-yi Li Hideharu Nakashima Satoshi Hata Wen-huai Tian school of Materials Science and engineering University of Science and Technology Beijing interdisciplinary graduate school of engineering Sciences Kyushu University

We present a study concerning Fe-0. 176C-1.31Si-1.58Mn-0.26Al-0.3Cr （wt%） steel subjected to a quenching and partitioning （Q＆P） process. The results of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tensile tests demon- strate that the microstructures primarily consist of lath martensite, retained austenite, lower bainite （LB）, and a small amount of tempered martensite; moreover, few twin austenite grains were observed. In the microstrucmre, three types of retained austenite with different sizes and morphologies were observed： blocky retained austenite （-300 nm in width）, film-like retained austenite （80-120 nm in width）, and ul- tra-fine film-like retained austenite （30-40 nm in width）. Because of the effect of the retained austenite/martensite/LB triplex microstructure, the specimens prepared using different quenching temperatures exhibit high ultimate tensile strength and yield strength. Furthermore, the strength effect of LB can partially counteract the decreasing strength effect of martensite. The formation of LB substantially reduces the amount of retained austenite. Analyses of the retained austenite and the amount of blocky retained austenite indicated that the carbon content is critical to the total elongation of Q＆P steel.

关键词： low-carbon steel quenching partitioning retained austenite rnicrostructure mechanical properties

Microstructural evolution and mechanical properties of a low-carbon quenching and partitioning steel after partial and full austenitization

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International Journal of Minerals,Metallurgy and Materials 2016年第8期23卷 906-919页

作者： Wan-song Li Hong-ye Gao Hideharu Nakashima Satoshi Hata Wen-huai Tian school of Materials Science and engineering University of Science and Technology Beijing interdisciplinary graduate school of engineering Sciences Kyushu University

In this work, low-carbon steel specimens were subjected to the quenching and partitioning process after being partially or fully austenitized to investigate their microstructural evolution and mechanical properties. According to the results of scanning electron microscopy and transmission electron microscopy observations, X-ray diffraction analysis, and tensile tests, upper bainite or tempered martensite appears successively in the microstructure with increasing austenitization temperature or increasing partitioning time. In the partially austenitized specimens, the retained austenite grains are carbon-enriched twice during the heat treatment, which can significantly stabilize the phases at room temperature. Furthermore, after partial austenitization, the specimen exhibits excellent elongation, with a maximum elongation of 37.1%. By contrast, after full austenitization, the specimens exhibit good ultimate tensile strength and high yield strength. In the case of a specimen with a yield strength of 969 MPa, the maximum value of the ultimate tensile strength reaches 1222 MPa. During the partitioning process, carbon partitioning and carbon homogenization within austenite affect interface migration. In addition, the volume fraction and grain size of retained austenite observed in the final microstructure will also be affected.

关键词： low-carbon steel quenching partitioning microstructure mechanical properties interfaces

Wastewater degradation by iron/copper nanoparticles and the microorganism growth rate

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Journal of Environmental Sciences 2018年第12期30卷 19-31页

作者： Tareq W.M.Amen Osama Eljamal Ahmed M.E.Khalil Nobuhiro Matsunaga Earth System Science and Technology Interdisciplinary Graduate School of Engineering Sciences Kyushu University Department of Chemical engineering Faculty of Engineering Cairo University

Nowadays, trends in wastewater treatment by zero-valent iron（ZVI） were turned to use bimetallic NZVI particles by planting another metal onto the ZVI surface to increase its reactivity. Nano size zero-valent iron/copper（NZVI/Cu0） bimetallic particles were synthesized in order to examine its toxicity effects on the wastewater microbial life, kinetics of phosphorus, ammonia stripping and the reduction of chemical oxygen demand（COD）.Various concentrations of NZVI/Cu0 and operation conditions both aerobic and anaerobic were investigated and compared with pure NZVI experiment. The results showed that addition10 mg/L of NZVI/Cu0 significantly increased the numbers of bacteria colonies under anaerobic condition, conversely it inhibited bacteria activity with the presence of oxygen. Furthermore,the impact of nanoparticles on ammonia stripping and phosphorus removal was also linked to the emitted iron ions electrons. It was found that dosing high concentration of bimetallic NZVI/Cu0 has a negative effect on ammonia stripping regardless of the aeration condition. In comparison to control, dosing only 10 mg/L NZVI/Cu0, the phosphorus removal increased sharply both under aerobic and anaerobic conditions, these outcomes were obtained as a result of complete dissolution of bimetallic nanoparticles which formed copper-iron oxides components that are attributed to increasing the phosphorus adsorption rate.

关键词： Iron bimetallic Wastewater biodegradation Bacterial life Contaminants removal

Initial testing of ohmic heating through double flux swing during electron cyclotron start-up in the QUEST spherical tokamak

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Plasma Science and Technology 2023年第5期25卷 31-36页

作者：张逸凡 Takumi ONCHI Kazuo NAKAMURA 岳其霖 Takahiro NAGATA Shoji KAWASAKI Kengoh KURODA Makoto HASEGAWA Ryuya IKEZOE Takeshi IDO Kazuaki HANADA Hiroshi IDEI interdisciplinary graduate school of engineering Sciences Kyushu UniversityKasuga 816-8580Japan Research Institute for Applied Mechanics Kyushu UniversityKasuga 816-8580Japan

A power-supply system was developed for Ohmic heating(OH)to double×10^(18)the amount of change magnetic flux in the primary central solenoid(CS)on the QUEST spherical *** power supplies are connected with stacks of insulated-gate bipolar transistors,and sequentially operated to generate positive and negative CS *** bipolar power-supply system is controlled via a field-programmable gate array,which guarantees the safety of the entire system *** new OH system,assisted by electron cyclotron heating,enables the stable generation of plasma currents exceeding 100 k ***,the achieved electron density over the wide range in the major radial direction exceeds the cut-off density for one of the highpower microwave sources in *** strategy yields target plasmas for future experiments with the electron Bernstein wave.

关键词： spherical tokamak ohmic heating electron cyclotron heating FPGA

Investigation of transient and heterogeneous micro-climate around a human body in an enclosed personalized work environment

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Energy and Built Environment 2020年第4期1卷 423-431页

作者： Chong Wang Sung-Jun Yoo Shin-ichi Tanabe Kazuhide Ito interdisciplinary graduate school of engineering Sciences Kyushu UniversityJapan Faculty of engineering Sciences Kyushu UniversityJapan Faculty of Science and engineering Waseda UniversityJapan

Heterogeneous distribution of indoor environmental quality is known to have a great impact on human health,comfort,and productivity.A personalized work environment,that creates a localized and independent environ-ment with capsules or partitions,is being developed worldwide to provide workers with a space that enables undisturbed concentration on studying and ***,the minimized interior space of a personalized work environment can immediately cause adverse health impacts for occupant if the air quality and thermal en-vironment in the personalized work environment is not controlled ***,constant breathing can sharply increase the CO 2 concentrations in an interior space with an insufficient ventilation *** order to design a healthy and comfortable indoor environment,especially in a personalized work environment,it is important to predict precisely and comprehensively the transient and heterogeneous structure of the indoor envi-ronment formed around a human *** this background,we have developed an in silico human model that integrates a computational human model(virtual manikin combined with thermoregulation models)and respi-ratory model(virtual airway)for estimating indoor environmental quality,targeting the microclimate around a human body and breathing zone with high *** this study,we report the applicability of a comprehensive in silico human model to estimate the environ-mental quality in a personalized work environment.A coupled analysis of heat and contaminant transfer with computational fluid dynamics was conducted targeting the space around the in silico human model installed in a virtual personalized work *** informative data including human thermal comfort and breathing air quality were obtained,potentially forming the basis for the development of a digital twin of the personalized work environment and contributing to the design of a healthy,comfortable,and productive personalized work environme

关键词： Microclimate Indoor environment Digital twin Personalized work environment Computational fluid dynamics in silico human model

Non-Inductive Start up of QUEST Plasma by RF Powert

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Plasma Science and Technology 2011年第3期13卷 307-311页

作者： K. HANADA H. ZUSHI H. IDEI K. NAKAMURA M. ISHIGURO S. TASHIMA E. I. KALINNIKOVA M. SAKAMOTO M. HASEGAWA A. FUJISAWA A. HIGASHIJIMA S. KAWASAKI H. NAKASHIMA H. LIU O. MITARAI T. MAEKAWA A. FUKUYAM Y. TAKASE J. QIAN Research Institute for Applied Mechanics Kyushu University Japan interdisciplinary graduate school of engineering Science Kyushu University Japan school of Industrial engineering Tokai University Japan graduate school of Energy Science Kyoto University Japan graduate school of Technology Kyoto University Japan graduate school of Frontier Science University of Tokyo Japan Institute of Plasma Physics Chinese Academy of Sciences China

Both start-up and sustainment of plasma were successfully achieved by fully non- inductive current drive using microwave with a frequency of 8.2 GHz. Plasmas current of 15 kA was implemented for 1 s. Magnetic surface reconstruction exhibited a plasma shape with an aspect ratio of below 1.5. The plasma current was dependent significantly on the launched microwave power and vertical magnetic field, while not affected by the mode of launched wave and the toroidal refractive index. Hard X-ray （HXR） emitted from energetic electrons accelerated by the microwave was observed, and the discharge with a plasma current over 4 kA followed the same trend as the number of photons of 10 keV to 12 keV. This suggests that the plasma current may be driven by energetic electrons. Based on the experimental conditions, alternative explanations of how the plasma current could be driven are discussed.

关键词： steady-state operation of spherical tokamak non-inductive current drive QUEST

Effect of Boundary Layer Trip on Reduction of Jet Noise in Over-Expanded Nozzle Flow

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Journal of Thermal Science 2017年第5期26卷 448-452页

作者： Masayuki ANYOJI Issei TABARU interdisciplinary graduate school of engineering Sciences Kyushu University 6-1 Kasuga-koen Kasuga-city Fukuoka Japan Department of Energy and Environmental engineering Kyushu University 6-1 Kasuga-koen Kasuga-city FukuokaJapan

A flow resonance accompanied by the emission of acoustic tones occurs in an over-expanded convergent-divergent(C-D) nozzle when operated at comparatively low pressure ratios. This phenomenon is distinguished from conventional screech tones and is referred to as "transonic tones". In contrast to screech tones, the peak resonant frequency for transonic tones increases with pressure ratio; the peak sound pressure level exceeds 110 d B. In this study, we investigated the basic characteristics of transonic resonance and tones using a circular C-D nozzle in an anechoic room. The effects of the boundary layer trip were also evaluated using a tripping wire for the suppressing transonic resonance and tones. The results of acoustic measurements show that several predominant peaks correspond to transonic tones. However, the boundary layer trip inside the nozzle effectively eliminated these tones and suppressed the unsteadiness of the flow inside the nozzle.

关键词： Transonic tones convergent-divergent nozzle noise reduction boundary layer trip

Characterization of chlorine and heavy metals for the potential recycling of bottom ash from municipal solid waste incinerators as cement additives

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Frontiers of Environmental Science & engineering 2016年第4期10卷 43-51页

作者： Boran WU Dongyang WANG Xiaoli CHAI Fumitake TAKAHASHI Takayuki SHIMAOKA State Key Laboratory of Pollution Control and Resources Reuse Tongji University Shanghai 200092 China Department of Environmental Science and Technology Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology Yokohama 226-8502 Japan Department of Urban and Environmental engineering Graduate School of Engineering Kyushu University Fukuoka 819-0395 Japan

Bottom ash is an inevitable by-product fi＇om municipal solid waste （MSW） incineration plants. Recycling it as additives for cement production is a promising disposal method. However, the heavy metals and chlorine are the main limiting factors because of the potential environmental risks and corrosion of cement kilns. Therefore ,investigating heavy metal and chlorine characteristics of bottom ash is the significant prerequisite of its reuse in cement industries. In this study, a correlative analysis was conducted to evaluate the effect of the MSW components and collection mode on the heavy metal and chlorine characteristics in bottom ash. The chemical speciation of insoluble chlorine was also investigated by synchrotron X-ray diffraction analysis. The results showed that industrial waste was the main source of heavy metals, especially Cr and Pb, in bottom ash. The higher contents of plastics and kitchen waste lead to the higher chlorine level （0.6 wt.%-0.7 wt.%） of the bottom ash. The insoluble chlorine in the MSW incineration bottom ash existed primarily as AlOCl, which was produced under the high temperature （1250℃） in incinerators.

关键词： Bottom ash ChlorineHeavy metals Waste inputs Synchrotron X-ray diffraction AlOCl