• 제목/요약/키워드: Metal Fuel

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Numerical study on conjugate heat transfer in a liquid-metal-cooled pipe based on a four-equation turbulent heat transfer model

  • Xian-Wen Li;Xing-Kang Su;Long Gu;Xiang-Yang Wang;Da-Jun Fan
    • Nuclear Engineering and Technology
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    • v.55 no.5
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    • pp.1802-1813
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    • 2023
  • Conjugate heat transfer between liquid metal and solid is a common phenomenon in a liquid-metal-cooled fast reactor's fuel assembly and heat exchanger, dramatically affecting the reactor's safety and economy. Therefore, comprehensively studying the sophisticated conjugate heat transfer in a liquid-metal-cooled fast reactor is profound. However, it has been evidenced that the traditional Simple Gradient Diffusion Hypothesis (SGDH), assuming a constant turbulent Prandtl number (Prt,, usually 0.85 - 1.0), is inappropriate in the Computational Fluid Dynamics (CFD) simulations of liquid metal. In recent decades, numerous studies have been performed on the four-equation model, which is expected to improve the precision of liquid metal's CFD simulations but has not been introduced into the conjugate heat transfer calculation between liquid metal and solid. Consequently, a four-equation model, consisting of the Abe k - ε turbulence model and the Manservisi k𝜃 - ε𝜃 heat transfer model, is applied to study the conjugate heat transfer concerning liquid metal in the present work. To verify the numerical validity of the four-equation model used in the conjugate heat transfer simulations, we reproduce Johnson's experiments of the liquid lead-bismuth-cooled turbulent pipe flow using the four-equation model and the traditional SGDH model. The simulation results obtained with different models are compared with the available experimental data, revealing that the relative errors of the local Nusselt number and mean heat transfer coefficient obtained with the four-equation model are considerably reduced compared with the SGDH model. Then, the thermal-hydraulic characteristics of liquid metal turbulent pipe flow obtained with the four-equation model are analyzed. Moreover, the impact of the turbulence model used in the four-equation model on overall simulation performance is investigated. At last, the effectiveness of the four-equation model in the CFD simulations of liquid sodium conjugate heat transfer is assessed. This paper mainly proves that it is feasible to use the four-equation model in the study of liquid metal conjugate heat transfer and provides a reference for the research of conjugate heat transfer in a liquid-metal-cooled fast reactor.

Corrosion Assessment of Al/Fe Dissimilar Metal Joint (Al/Fe 이종금속 접합부의 부식특성)

  • Kang, Minjung;Kim, Cheolhee;Kim, Junki;Kim, Dongcheol;Kim, Jonghoon
    • Journal of Welding and Joining
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    • v.32 no.4
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    • pp.55-62
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    • 2014
  • The use of light-weight Al alloys in the automotive industry is increasing to meet requirements for fuel efficiency and emission reduction. Joining Al alloy to the conventional steel sheet is also very important issue with the increased use of Al alloy, and several joining processes have been introduced to enhance joining strength between dissimilar metals. This paper deals with a galvanic corrosion in the dissimilar metal joining. Salt spray tests up to 2000 hours were conducted on a self-piercing rivet, spot welded, adhesive bonded and weld-bonded joints, and cross-sections and tensile shear strength according the salt spray duration were analyzed at every 500-hour. Self-piercing rivet joint had relative low initial strength but the joint strength did not change regardless of the salt spray duration. The strength of other joints (spot welded, adhesive bonded and weld-bonded joints) decreased with the increase of salt spray duration and the corrosion behaviour of each joint was discussed.

A Study on Performance Improvement of PEMFC Using Wire Mesh Cell Structure (Wire Mesh 적용을 통한 PEMFC 성능 향상에 관한 연구)

  • Jin, Sang-Mun;Beack, Suk-Min;Heo, Seong-Il;Yang, Yoo-Chang;Kim, Sae-Hoon
    • Journal of Hydrogen and New Energy
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    • v.21 no.4
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    • pp.295-300
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    • 2010
  • Metal bipolar plate applied to Polymer Electrolyte Membrane Fuel Cell is getting most attractive due to their good feasibility of mass production and low cost. But it is one of the immediate causes of performance decline because it is difficult to reduce channel pitch of metal bipolar plate. In this study, mesh was inserted in between bipolar plate and GDL to obtain uniform contact pressure without reducing channel pitch. The section measuring and performance test were carried out to confirm the mesh structure distributes contact pressure equally in reacting area. The performance of 3 type mesh structures developed in this study were higher than the normal cell at all over the current range. Especially, it showed that the mesh cell performance was increased and pressure drop was decreased with diminishing mesh gap size. The Mesh structure was more sensitive to humidification and contact pressure change than the normal cell.

Preparation of NiO/YSZ Ultra-Fine Powder Composites Using Self-Sustaining Combustion Process (Self-Sustaining Combustion Process를 이용한 NiO/YSZ 초미세 복합분말 제조)

  • 김선재;정충환;김경호;김영석;국일현
    • Journal of the Korean Ceramic Society
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    • v.33 no.4
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    • pp.411-417
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    • 1996
  • Ultrafine NiO/YSZ (Yttria Stabilized Zirconia) powders were made by using a glycine nitrate process which is used as anode material for solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal nitrates occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized powders were examined with X-ray diffraction(XRD) Brunauer Emmett Teller with N2 absorption. scanning electron microscopy (SEM). and transmission electron microscopy (TEM). Ultrafine NiO/YSZ powders of 15-18 m2/g were obtained through GNP when the content of glycine was controlled to 1 or 2 times the stoichiometric ratio in the precursor solutions. Strongly acid precursor solution increased the specific surface area of the synthesized powders. This is suggested to be the increased binding of metal nitrates and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of {{{{ { NH}`_{3 } ^{+ } }}. After sintering and reducing treatment of NiO/YSZ powders synthesized by GNP the Ni/YSZ pellet showed ideal microstructure where very fine Ni particles of 3-5 ${\mu}{\textrm}{m}$ were distributed uniformly and fine pore around Ni metal particles was formed. leading to anincrease of the triple phase boundary among gas Ni and YSZ.

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The First-principles View of Nanometal Alloy Catalysts

  • Ham, Hyung Chul;Hwang, Gyeong S.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.129-129
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    • 2013
  • Nanometal alloy catalysts have been found to significantly increase catalytic efficiency, compared to the monometallic counterparts. This enhancement can be attributed to various alloying effects: i) the existence of uniquemixed-metal surface sites [the so called ensemble (geometric) effect]; ii) electronic state changes due to metal-metal interactions [the so called ligand (electronic) effect]; and iii) strain caused by lattice mismatch between the alloy components [the socalled strain effect]. In addition, the presence of low-coordination surface atoms and preferential exposure of specific facets [(111), (100), (110)] in association with the size and shape of nanoparticle catalysts [the so called shape-size-facet effect] can be another important factor for modifying the catalytic activity. However, mechanisms underlying the alloying effect still remain unclear owing to the difficulty of direct characterization. Computational approaches, particularly the prediction using first-principles density functional theory (DFT), can be a powerful and flexible alternative for unraveling the role of alloying effects in catalysis since those can give us quantitative insights into the catalytic systems. In this talk, I will present the underlying principles (such as atomic arrangement, facet, local strain, ligand interaction, and effective atomic coordination number at the surface) that govern catalytic reactions occurring on Pd-based alloys using the first-principles calculations. This work highlights the importance of knowing how to properly tailor the surface reactivity of alloy catalysts for achieving high catalytic performance.

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Options Manageing for Radioactive Metallic Waste From the Decommissioning of Kori Unit 1 (고리1호기 해체시 발생할 방사성금속폐기물 관리 옵션 연구)

  • Kessel, David S.;Kim, Chang-Lak
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.15 no.2
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    • pp.181-189
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    • 2017
  • The purpose of this paper is to evaluate several leading options for the management of radioactive metallic waste against a set of general criteria including safety, cost effectiveness, radiological dose to workers and volume reduction. Several options for managing metallic waste generated from decommissioning are evaluated in this paper. These options include free release, controlled reuse, and direct disposal of radioactive metallic waste. Each of these options may involve treatment of the metal waste for volume reduction by physical cutting or melting. A multi-criteria decision analysis was performed using the Analytic Hierarchy Process (AHP) to rank the options. Melting radioactive metallic waste to produce metal ingots with controlled reuse or free release is found to be the most effective option.

Concept Design of Hydro Reactive Solid Propellant for Underwater High Speed Ramjet Engine System (수(水)반응성 고체추진제를 이용한 수중고속램제트엔진 시스템 개념 설계)

  • Chae Jae-Ou;Sim Ju-Hyen;Kwak Yong-Whan;Koo Hyung-Joon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2005.11a
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    • pp.121-131
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    • 2005
  • For thrust motion of high speed underwater torpedo the special hydro reactive fuels that burns in vapor water and water supply from aboard is used. The main component of this hydro reactive fuel is the powder of active metal (Mg, Al) that can burn in water vapor with large heat generation in the rocket combustion chamber. The thermodynamic analysis of combustion properties of the burning of the particles of these active metal in the vapor water have been carried out. The conception for the possible content variants of the hydro reactive fuels have been discussed using the geometrical and thermodynamic combustion conditions with the basic recommendation for contents of designed hydro reactive fuels in future.

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Conceptual Design of the Slag Removal Method in the Metal Powder Combustor and Condition Tests for the Water Film Formation (금속분말 연소기의 slag 제거기법 개념 설계 및 Water Film 형성 조건 기초실험)

  • Kim, Kwang-Yeon;Shmelev, V.;Ko, Hyun;Lee, Sung-Woong;Cho, Yong-Ho
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.554-557
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    • 2011
  • One of the issues that occurs in development of a combustor using Metal Powder as a fuel is an alumina slag processing. A water film formed inside the combustor is expected to be able to solve this issue. The experiments about the formation of a water film were carried out as a preliminary study. As the tangential velocity of water jet is increasing, the angle derivation from horizontal is decreasing for the test model. Results of the experiments showed that the thin water film on the inner surface appeared at the velocity of 10~15 m/s.

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Flame Synthesis of Carbon Nanofibers using SUS304 Substrates (촉매금속 기판을 사용한 탄소나노섬유의 연소합성)

  • Lee, Gyo-Woo;Jurng, Jong-Soo;Hwang, JungHo
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1378-1383
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    • 2003
  • Synthesis of carbon nanofibers on a metal substrate by an ethylene fueled inverse diffusion flame was illustrated. Stainless steel plates were used for the catalytic metal substrate. The effects of radial distance and residence time of the substrate were investigated. The role of hydrocarbon composition in the fuel was also viewed. Nanofibers with a diameter range of 30-70 nm were found on the substrate. The carbon nanofibers were formed and grown in the region from 4 to 5.5 mm from the central axis of a flame outside of the visible flame front in the radial direction. The minimum residence time required for the formation of carbon nanofibers were about 20 seconds, and over 60 seconds were required for the full-scale growth. The characteristic time of the formation of carbon nanofibers was much shorter than that of the substrate temperature growth. In this study, the variation in hydrocarbon composition had no significant effect on the formation and growth of the carbon nanofibers.

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Finite Element Analysis and Formability Evaluation for Dimple Forming with Thin Sheet Metal (박판 딤플 성형을 위한 유한요소해석 및 성형성 평가)

  • Heo, Seong-Chan;Seo, Young-Ho;Ku, Tae-Wan;Song, Woo-Jin;Kim, Jeong;Kang, Beom-Soo
    • Transactions of Materials Processing
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    • v.16 no.8
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    • pp.621-628
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    • 2007
  • Nowadays, Exhaust Gas Recirculation(EGR) Cooler is one of the most favorite systems for reducing the generation amount of $NO_x$ and other particle materials from vehicles burning diesel as fuel. Efficiency of the system is mainly dependent on its heat transfer efficiency and this ability is affected by net heat transferring area of the system. For that reason, several types of heat transfer tube such as dimple, wrinkle and spiral types that have large net area are used. However, it is difficult to manufacture the rectangular tube with dimpled type structure because it experiences too much strain around the rectangular tube surface during the forming process. For that reason, in this study, numerical simulation for forming process of non-symmetric dimple shape on a thin sheet metal was carried out. Furthermore, theoretical forming limit curves(forming limit diagram, forming limit stress diagram) were proposed as criteria of formability evaluation. From the results of finite element simulation in view of stress and strain distribution, it is found that the designed process has robustness and feasibility to safely manufacture the dimpled rectangular tube.