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A Parametric Study for High-Efficiency Gas-Liquid Separator Design

journal of Thermal Science 2008年第3期17卷 238-242页

作者： S.Nagdewe j.K.Kwoon H.D.kim D.S.kim K.M.Kwak Toshiaki Setoguchi School of Mechanical Engineering Andong National University FMTRC Daejoo Co. Department of Mechanical Engineering Saga University

A gas liquid centrifugal separator is widely used in industry on account of its simple geometry and little maintenance. These separators have considerable advantages over filters, scrubbers or precipitators in term of compact design, lower pressure drop and higher capacity. A gas liquid centrifugal separator is a device that utilizes centrifugal forces and low pressure caused by rotational motion to separate liquid from gas by density differences. Efficient and reliable separation is required for the optimum operation. These separators are often operated at less than peak efficiency due to the entrainment of separated liquid through an outlet pipe which is closely associated with the very complicated flow phenomena involved. Design parameters such as length of the separation space, vane exit angle, inlet to outlet diameter ratio, models for separation efficiency and pressure drop as a function of physical dimensions are not available in literature. This leaves the designer with very little to go on except known designs and experimentation. The aim of present study is to perform a parametric study to get higher efficiency for gas-liquid separator. A parametric study has been carded out with the help of CFD tools to analyze a separation performance of a centrifugal separator by varying the length of separator space. The best design parameters are analyzed based upon obtained results, tangential velocities, vortices, total pressure losses. From the present study several attempts are made to improve the performance of conventional centrifugal separators.

关键词： Centrifugal separator Gas-liquid two-phase flow Swirl vane k-c RNG turbulence model Tangentialvelocity

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APPLICATION OF Ct-PARAMETER FOR CREEP-FATIGUE CRACK GROWTH WITH SLOW LOAD RISING CONDITION

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Acta Metallurgica Sinica(English Letters) 1999年第1期12卷 22-30页

作者： Lee, j.H. Yoon, K.B. kim, Y.j. Back, U.B. Korea Inst of Nuclear Safety Taejon South Korea

Most of the assessment equations for Ct which is a wellknown fracture parameter characterizing high temperature crack growth rates, have limited applicability to constant load conditions after sudden loading. However, crack growth due to creep can also occur under load varying conditions when load rising time is so long that accumulated creep deformation near the crack tip is not *** this paper, the estimation equation of the Ctparameter which can be applied to the case of slow load rising, i.e., (Ct)r, is explained. And the correlation between (Ct)r at the end of the load increasing period and Ct at the beginning of the succeeding load hold period is discussed. Finite element analyses of several cases with various loading conditions were performed and results were presented to show the effectiveness of the proposed Ct estimation scheme. The general applicability of the equation is also discussed.

关键词： creep fatigue crack time dependent fracture mechanics Ctparameter,C*integral

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Enhanced thermoelectric performance of spark plasma sintered p-type Ca_(3-x)Y_(x)Co_(4)O_(9+δ)systems

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journal of Materials Science & Technology 2020年第20期52卷 212-222页

作者： j.S.Cha D.H.kim H.Y.Hong K.Park Faculty of Nanotechnology and Advanced Materials Engineering Sejong UniversitySeoul05006Republic of Korea

Highly textured dense Ca3-xYxCo4 O9+δ(0≤x≤0.3)samples were fabricated by combining sol-gel process with spark plasma sintering(SPS).Y^3+substitution for Ca^2+simultaneously increased the Seebeck coefficient and reduced the thermal *** latter was attributed to the increase in lattice anharmonicity,structural distortion,and grain boundary area,which enhanced the phonon ***2.7Y0.3Co4 O9+δshowed the largest dimensionless figure-of-merit(ZT=0.194)at 1073 K because it had the largest Seebeck coefficient and the lowest thermal *** ZT value was 55%larger than that of undoped Ca3 Co4 O9(0.125 at 1073 K).Therefore,Y^3+substitution,sol-gel powder synthesis,and SPS are highly effective for enhancing the thermoelectric prope rties of Ca_(3)Co_(4)O_(9).

关键词： Electrical conductivity Ca_(3)Co_(4)O_(9) Thermoelectric properties Seebeck coefficient Thermal conductivity Spark plasma sintering

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In-situ electrochemical functionalization of carbon materials for high-performance Li–O2 batteries

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journal of Energy Chemistry 2020年第9期29卷 7-13,I0001页

作者： jungwon Kang jin Min kim Do Youb kim jungdon Suk jaekook kim Dong Wook kim Yongku Kang Department of Advanced Materials Science and Engineering Mokpo National University61 dorim-ri1666 Yeongsan-roCheonggye-myeonMuan-gunJeonnamSouth Korea Center for Advanced Battery Materials Advanced Materials DivisionKorea Research Institute of Chemical Technology(KRICT)141 Gajeong-RoYuseong-GuDaejeon 305-600South Korea Department of Materials Science and Engineering Chonnam National University300 Yongbong-dongBukguGwangju 500-757South Korea

The development of effective synthetic routes is important to manifest proper nature of specific ***-situ electrochemical functionalization possesses great advantages over conventional routes,especially facile way and leading to reaching elaborate sites of functional ***,we demonstrate the preparation of functionalized carbons by in-situ electrochemical reduction in an argon atmosphere for application in low-cost,environmentally benign,and high-performance oxygen-electrodes for non-aqueous Li-O2 batteries.A Li-O2 battery with functionalized carbon shows a high discharge capacity(100 times that of pristine carbon),high power and cycling *** outstanding performance is attributed to the high O2 affinity of the functionalized carbon surface that facilitates the formation of soluble and diffusible superoxide intermediates by the reduction of the remaining O2 competing with surface growth for Li2O2 formation.

关键词： Lithium-oxygen battery High areal capacity Functionalization of carbon Electrochemistry

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Peroxidase-like properties of Ruthenium nanoframes

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Science Bulletin 2016年第22期61卷 1739-1745页

作者： Haihang Ye jacob Mohar Qingxiao Wang Massimo Catalano Moon j.kim Xiaohu Xia Department of Chemistry Michigan Technological University Department of Materials Science and Engineering University of Texas at Dallas

This work reports the inherent peroxidase-like properties of Ruthenium （Ru） nanoframes. After templating with Palladium （Pd） seeds, Ru nanoframes with an octa- hedral shape, average edge length of 6.2 nm, and thickness of 1.8 nm were synthesized in high purity （〉95 %） and good uniformity. Using the oxidation of 3,3t,5,5＇-tetram- ethylbenzidine （TMB） by H202 as a model catalytic reac- tion, the Ru frames were demonstrated to be approximately three times more active than natural peroxidases in cat- alyzing the formation of colored products. As compared to their natural counterparts, Ru frames have a stronger binding affinity to TMB as well as a weaker binding affinity to hydrogen peroxide during the catalysis. The Ru frames as peroxidase mimics proved to be chemically and thermally stable. This work represents the first demonstration of Ru nanostructure-based peroxidase mimics and is therefore expected to inspire future research on bio-applications of Ru nanomaterials.

关键词： Ruthenium Nanoframes Peroxidase Enzyme mimic Catalysis

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Modeling Ionic Polymer-Metal Composites with Space-Time Adaptive Multimesh hp-FEM

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Communications in Computational Physics 2012年第1期11卷 249-270页

作者： David Pugal Pavel Solin Kwang j.kim Alvo Aabloo Mechanical Engineering Department University of NevadaReno RenoNV 89557USA Department of Mathematics and Statistics University of NevadaReno RenoNV 89557USA Institute of Thermomechanics PragueCzech Republic Institute of Technology University of TartuNooruse St 150411 TartuEstonia

We are concerned with a model of ionic polymer-metal composite(IPMC)materials that consists of a coupled system of the Poisson and Nernst-Planck equations,discretized by means of the finite element method(FEM).We show that due to the transient character of the problem it is efficient to use adaptive algorithms that are capable of changing the mesh dynamically in *** also show that due to large qualitative and quantitative differences between the two solution components,it is efficient to approximate them on different meshes using a novel adaptive multimesh *** study is accompanied with numerous computations and comparisons of the adaptive multimesh hp-FEMwith several other adaptive FEM algorithms.

关键词： Ionic polymer-metal composites IPMC Nernst-Planck equation Poisson equation finite element method FEM adaptive multi-mesh hp-FEM

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Simulation of electron behavior in PIG ion source for 9 MeV cyclotron

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Chinese Physics C 2014年第12期38卷 70-76页

作者： X.j.Mu M.Ghergherehchi Y.H.Yeon j.W.kim j.S.Chai College of Information & communication Engineering School of Electronic and Electrical EngineeringSungkyunkwan University Department of Energy Science Sungkyunkwan University

In this paper, we focus on a PIG source for producing intense H-ions inside a 9 MeV cyclotron. The properties of the PIG ion source were simulated for a variety of electric field distributions and magnetic field strengths using a CST particle studio. After analyzing the secondary electron emission（SEE） as a function of both magnetic and electric field strengths, we found that for the modeled PIG geometry, a magnetic field strength of 0.2 T provided the best results in terms of the number of secondary electrons. Furthermore, at 0.2 T, the number of secondary electrons proved to be greatest regardless of the cathode potential. Also, the modified PIG ion source with quartz insulation tubes was tested in a KIRAMS-13 cyclotron by varying the gas flow rate and arc current, *** capacity of the designed ion source was also demonstrated by producing plasma inside the constructed 9 MeV cyclotron. As a result, the ion source is verified as being capable of producing an intense H-beam and high ion beam current for the desired 9 MeV cyclotron. The simulation results provide experimental constraints for optimizing the strength of the plasma and final ion beam current at a target inside a cyclotron.

关键词： PIG ion source CST particle studio electromagnetic field secondary electron gas flow rate arc

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Boosting overall water splitting by incorporating sulfur into NiFe(oxy)hydroxide

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journal of Energy Chemistry 2022年第1期31卷 364-371,I0010页

作者： Chiho kim Seong Hyun kim Seunghun Lee Ilyeong Kwon Seong Hyun kim Shinho kim Changgyu Seok Yoo Sei Park Yangdo kim Department of Materials Science and Engineering Pusan National UniversityBusan 46241Republic of Korea BK21 Four Innovative Graduate Education Program for Global High-tech Materials&PartsPusan National UniversityBusan 46241Republic of Korea Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH).Pohang 37673Republic of Korea

Developing highly active and cost-effective electrocatalysts for enhancing the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)is a significant challenge for overall water ***-incorporated nickel iron(oxy)hydroxide(S-NiFeOOH)nanosheets were directly grown on commercial nickel foam using a galvanic corrosion method and a hydrothermal *** incorporation of sulfur into NiFeOOH enhanced the catalytic activity for the HER and OER in 1 M KOH *** enhanced catalytic activity is attributed to the change in the local structure and chemical states due to the incorporation of *** performance for overall water splitting was achieved with an alkaline water *** was realized by employing S-NiFeOOH as a bifunctional electrocatalyst,thereby outperforming a water electrolyzer that requires the usage of precious metal electrocatalysts(i.e.,Pt/C as the HER electrocatalyst and IrO_(2) as the OER electrocatalyst).Moreover,when driven by a commercial silicon solar cell,an alkaline water electrolyzer that uses S-NiFeOOH as a bifunctional electrocatalyst generated hydrogen under natural *** study shows that S-NiFeOOH is a promising candidate for a large-scale industrial implementation of hydrogen production for overall water splitting because of its low cost,high activity,and *** addition,the solar-driven water electrolyzer using S-NiFeOOH as a bifunctional electrocatalyst affords the opportunity for developing effective and feasible solar power systems in the future.

关键词： Overall water splitting Hydrogen production Sulfur incorporated NiFe(oxy)hydroxide Electrocatalysts Solar-driven water splitting

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Transient analysis of diffusive chemical reactive species for couple stress fluid flow over vertical cylinder

引用

Applied Mathematics and Mechanics(English Edition) 2013年第8期34卷 985-1000页

作者： H.P.RANI G.j.REDDY C.N.kim Department of Mathematics National Institute of Technology Department of Mechanical Engineering College of Advanced Technology (Industrial Liaison Research Institute) Kyung Hee University

The unsteady natural convective couple stress fluid flow over a semi-infinite vertical cylinder is analyzed for the homogeneous first-order chemical reaction effect. The couple stress fluid flow model introduces the length dependent effect based on the material constant and dynamic viscosity. Also, it introduces the biharmonic operator in the Navier-Stokes equations, which is absent in the case of Newtonian fluids. The solution to the time-dependent non-linear and coupled governing equations is carried out with an unconditionally stable Crank-Nicolson type of numerical schemes. Numerical results for the transient flow variables, the average wall shear stress, the Nusselt number, and the Sherwood number are shown graphically for both generative and destructive reactions. The time to reach the temporal maximum increases as the reaction constant K increases. The average values of the wall shear stress and the heat transfer rate decrease as K increases, while increase with the increase in the Sherwood number.

关键词： couple stress fluid chemical reaction natural convection vertical cylinder,finite difference method

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Effect of 1Al addition on deformation behavior of Mg

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journal of Magnesium and Alloys 2021年第2期9卷 489-498页

作者： ji Hyun Hwang A.Zargaran Gyeongbae Park O.Lee B.-j.Lee Nack j.kim Center for Advanced Aerospace Materials Pohang University of Science and Technology(POSTECH)PohangSouth Korea

Deformation behavior of 1 Al containing Mg alloy has been investigated in the present *** annealing,the Mg-1 Al alloy shows a typical basal *** compared to the pure Mg having a similar texture and grain size,the Mg-1 Al alloy shows much higher strength and larger *** trace analyses of the tensile strained specimens show that non-basal slips such as pyramidal I and II slips can be easily activated at an early stage of deformation in the Mg-1 Al alloy and the grains in the Mg-1 Al alloy are seen to accommodate a larger degree of deformation than those in the pure Mg at a given *** increasing tensile strain,however,there is a strain localization along the initially formed slip lines of non-basal slips,forming surface steps without activating multiple slip lines.

关键词： Deformation behavior Slip trace analysis Non-basal slip Strain localization Ductility

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