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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers B
Journal Basic Information
Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 35, Issue 12 - Dec 2011
Volume 35, Issue 11 - Nov 2011
Volume 35, Issue 10 - Oct 2011
Volume 35, Issue 9 - Sep 2011
Volume 35, Issue 8 - Aug 2011
Volume 35, Issue 7 - Jul 2011
Volume 35, Issue 6 - Jun 2011
Volume 35, Issue 5 - May 2011
Volume 35, Issue 4 - Apr 2011
Volume 35, Issue 3 - Mar 2011
Volume 35, Issue 2 - Feb 2011
Volume 35, Issue 1 - Jan 2011
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Study on PEM-Fuel-Cell Humidification System Consisting of Membrane Humidifier and Exhaust Air Recirculation Units
Byun, Su-Young ; Kim, Beom-Jun ; Kim, Min-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 337~344
DOI : 10.3795/KSME-B.2011.35.4.337
The humidification of reactant gases is crucial for efficiently operating PEM (polymer electrolyte membrane) fuel cell systems and for improving the durability of these systems. The recycle of the energy and water vapor of exhaust gas improves the system performance especially in the case of automotive application. The available humidification methods are steam injection, nozzle spray, humidification by enthalpy wheel, membrane humidifier, etc. However, these methods do not satisfy certain requirements such as compact design, efficient operation and control. In this study, a hybrid humidification system consisting of a membrane humidifier and exhaust-air recirculation units was developed and the humidification performance of this hybrid humidifier was analyzed. Finally, a new practical method for optimal design of PEM-fuel-cell humidification system is proposed.
Numerical Study on Aerodynamic Lift on Windshield Wiper of High-Speed Passenger Vehicles
Lee, Seung-Ho ; Lee, Sung-Won ; Hur, Nahm-Keon ; Choi, Woo-Nyoung ; Sul, Jin-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 345~352
DOI : 10.3795/KSME-B.2011.35.4.345
In the present study, a three-dimensional CFD simulation on aerodynamic lift acting on windshield wiper blades was performed to improve the wiping performance of a vehicle moving at a high speed. To predict the reliable flow characteristics around the windshield wiper system, the computational domain included the full vehicle model with detailed geometry of wiper blades in the wind tunnel. From the numerical results, the drag and lift coefficients of wiper blade were obtained for the performance of windshield wiper. With this aerodynamic characteristics of windshield wiper, the effects of wiping angles and hood tip angle on the wiping performance of the windshield wiper were evaluated.
A Numerical Analysis of the Binary Droplet Collision by Using a Level Set Method
Lee, Sang-Hyuk ; Hur, Nahm-Keon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 353~360
DOI : 10.3795/KSME-B.2011.35.4.353
The prediction of binary droplet collisions is important in the formation of falling drops and the evolution of sprays. The droplet velocity, impact parameter, and drop-size ratio influence the interaction between the droplets. The effect of these parameters results in complicated collision phenomena. Droplet collisions can be classified into four types of interactions: bouncing, coalescence, reflexive separation, and stretching separation. In the present study, the interfacial flow problem of the droplet collision was numerically simulated by using the level set method. 2D axisymmetric simulations on the head-on collisions and 3D simulation on the off-center collisions were performed. The numerical results of droplet behavior after the collision agreed well with the experimental and analytical results. The mixing of the mass of the initial droplets after the collision was also predicted by using different species index of colliding droplets.
Study on Effect of Increase in Inlet Temperature on Nafion Membrane Humidifier
Hwang, Jun-Young ; Chang, Hyo-Sun ; Kang, Kyung-Tae ; Kang, Heui-Seok ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 361~369
DOI : 10.3795/KSME-B.2011.35.4.361
The effect of an increase in the temperature of inlet air on the performance of a membrane humidifier for a PEMFC (Polymer Electrolyte Membrane Fuel Cell) vehicle was investigated both experimentally and numerically. A shell-and-tube type gas-to-gas humidifier with Nafion membrane was tested. The experimental result showed that water transfer varies nonlinearly with the temperature elevation. Numerical analysis based on detailed modeling was also conducted in simplified geometry of a single tube to explain this nonlinear behavior. The simulation revealed that the local water flux varies nonlinearly and dramatically along the tube. The analysis was based on the inverse relationship between the increase in temperature and decrease in relative humidity, both of which seriously affect the water conductivity of the membrane.
Effects of Aromatics and T90 Temperature for High Cetane Number Fuels on Exhaust Emissions in Low-Temperature Diesel Combustion
Han, Man-Bae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 371~377
DOI : 10.3795/KSME-B.2011.35.4.371
The aim of this study is to investigate the effects of aromatics and T90 temperature for high cetane number (CN) of diesel fuels on combustion and exhaust emissions in low-temperature diesel combustion in a 1.9 L common rail direct injection diesel engine at 1500 rpm and 2.6 bar BMEP. Four sets of fuels with CN 55, aromatic content of 20% or 45% (vol. %), and T90 temperature of
were tested. Given engine operating conditions, all the fuels showed the same tendency of decrease of PM with an increase of an ignition delay time. At the same ignition delay time, the fuels with high T90 produced higher PM. At the same MFB50% location the amount of NOx was similar for all the fuels. Furthermore, at the same ignition delay time the amounts of THC and CO were similar as well for all the fuels. The amount of THC and CO increased with an extension of the ignition delay time mainly because of the increase of fuel-air over-mixing.
Comparison of Electro-Osmotic Pumps with Two Different Types of Porous Glass Frits
Kwon, Kil-Sung ; Park, Chul-Woo ; Kim, Dae-Joong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 379~383
DOI : 10.3795/KSME-B.2011.35.4.379
Electro-osmotic pumps were fabricated by using two types of porous glass frits. The performance of these pumps was characterized in terms of maximum flow rate, current, and pressure using deionized water and 1 mM sodium tertraborate decahydrate buffer. Maximum flow rate and current when ROBU porous glass frits were used were higher than those when DURAN porous glass frits were used because of the high porosity of the ROBU glass frits. However, the maximum pressure when ROBU glass frits were used was similar to that when DURAN glass frits were used. The therrmodynamic efficiency of a pump with ROBU porous glass frits is approximately twice that of a pump with DURAN porous glass frits. Further, the maximum flow rate at maximum current in the case of ROBU porous glass frits is high. However, it is lower than the maximum pressure at maximum current in the case of DURAN porous glass frits. Further, in this study, we also verified the effectiveness of ROBU glass frits when high flow rate is required and of DURAN glass frits when a high pressure is required.
Simple Fabrication of Micromixer Based on Non-Equilibrium Electrokinetics in Micro/Nano Hybrid Fluidic System
Yu, Samuel ; Kim, Sun-Min ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 385~390
DOI : 10.3795/KSME-B.2011.35.4.385
In this study, we developed a micromixer based on the non-equilibrium electrokinetics at the junction of a microchannel and nanochannel. Two fluid streams were mixed by an electro-osmotic flow and a vortex flow created as a result of the non-equilibrium electrokinetics at the junction of the microchannel and nanochannel. Initially, the microchannel was fabricated using Polydimethylsiloxane (PDMS) by the general soft lithography process and the nanochannel was created at a specific position on the microchannel by applying a high voltage. To evaluate the mixing performance of the micromixer, fluorescent distribution was analyzed by using the fluorescent dye, Rhodamine B. About 90% mixing was achieved with this novel micromixer, and this micromixer can be used in microsystems for biochemical sample analysis.
Experimental Study on Autothermal Reformation of Methanol with Various Oxygen to Methanol Ratios for Fuel Cell Applications
Hwang, Ha-Na ; Shin, Gi-Soo ; Jang, Sang-Hoon ; Choi, Kap-Seung ; Kim, Hyung-Man ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 391~397
DOI : 10.3795/KSME-B.2011.35.4.391
The use of Hydrogen as a fuel is receiving considerable attention and as a result, research on novel methods of hydrogen production is necessary so that the hydrogen demands in the future can be satisfied. This study presents experimental data on methanol Autothermal Reformation that quantifies the relationship between the oxygen-to-methanol ratio (
) and reformer efficiency. For each catalyst configuration, the
was varied from 0.1 to 0.4, with an increment of 0.05, to investigate the effects of
on the reactor performance, including temperature profile, conversion, and efficiency.
was increased from 0.15 to 0.20, and the catalyst bed temperature increased by
. The catalyst bed temperature increased with increasing
as the reaction shifted from endothermic to exothermic reaction and as a result, excess heat, which raised the reactor temperature, was generated. The reactor performance was shown to be highly dependent on
. The optimum
= 0.30 found in the experimental tests is 30% higher than the theoretical optimum of 0.23. This is attributed to a combination of factors such as the concentrations of the
gas, reaction rate, catalyst effects, heat loss from the reactor, and the difference between the actual amounts of reaction products formed and the theoretical amounts of the reaction products.
Analysis of Performance of SOFC/GT Hybrid Systems Considering Size-Dependent Performance of Gas Turbines
Myung, No-Sung ; Park, Sung-Ku ; Kim, Tong-Seop ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 399~407
DOI : 10.3795/KSME-B.2011.35.4.399
This study analyzes the performance of hybrid power systems combining a solid oxide fuel cell (SOFC) and a gas turbine (GT). Research focus is given to the influence of the size-dependent gas turbine performance on hybrid system performance. Three hybrid systems adopting different gas turbines (kW, sub-MW, multi-MW classes) are designed. As the gas turbine power increases (i.e. as the gas turbine performance enhances), the gas turbine power portion increases and the hybrid system efficiency increases. The hybrid system shows efficiency improvement over the SOFC only system even in the case where the gas turbine net power is nearly zero. The increase of gas turbine pressure ratio contributes to the net hybrid system power output in all of the three cases, while system efficiency is almost independent on the pressure ratio.
On-Road Investigation of PM Emissions of a City-Buses Fuelled by Diesel, CNG, and LPG Using a Mobile Emission Laboratory
Lee, Seok-Hwan ; Kim, Hong-Suk ; Park, Jun-Hyuk ; Yoon, Jun-Kyu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 409~416
DOI : 10.3795/KSME-B.2011.35.4.409
A mobile emission laboratory (MEL) was designed to measure the amount of traffic pollutants with high temporal and spatial resolution under real conditions. Equipment for gas-phase measurements of quantity of CO, NOx,
, and THC and for the measurement of the number density and size distribution of fine and ultra-fine particles by a FMPS and a CPC were placed in a mini-van. The exhaust of different type of vehicles can be sampled by MEL. This paper describes the construction and technical details of the MEL and presents data from the experiment in which a car chases city buses fuelled by diesel, CNG, and LPG. The diameters of most particles in the exhaust of the diesel city bus were less than 300 nm and most of the particles had a diameter of 30-60 nm. However, most particles in the exhaust of the CNG and LPG city buses were nanoparticles (diameter: less than 50 nm).
The Effect of Pitch-to-Diameter Ratio on Natural Convection Heat Transfer of Two In-Line Horizontal Cylinders
Chae, Myeong-Seon ; Kang, Gyeong-Uk ; Chung, Bum-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 417~424
DOI : 10.3795/KSME-B.2011.35.4.417
Natural convection heat transfer experiments from two parallel horizontal cylinders were performed varying the Pitch-to-Diameter ratio (P/D) of 1.02-9 at Sc of 2,014 to 8,334 and
. Mass transfer experiments that are analogous to the heat transfer experiments were performed using copper electroplating system. In all cases, the measured heat transfer rates for the lower cylinder agreed well with the existing heat transfer correlations developed from a single cylinder. For laminar flows, the measured heat transfer rates of the upper cylinder were less than those of the lower cylinder at P/D less than about 1.5. However, as the P/D increased, the heat transfer rates of the upper cylinder increased. For turbulent flows, the heat transfer rates of the upper cylinder were considerably similar to those of the lower cylinder when the P/D is approximately unity. In contrast, as the P/D increased, the heat transfer rates of the upper cylinder were always higher than those of the lower cylinder.
Numerical Simulation on the Spreading and Heat Transfer of Ex-Vessel Core Melt in a Channel
Ye, In-Soo ; Ryu, Chang-Kook ; Ha, Kwang-Soon ; Song, Jin-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 425~429
DOI : 10.3795/KSME-B.2011.35.4.425
In the unlikely of nuclear reactor meltdown, the leaked core melt or corium must be contained in a device called core-catcher so that the corium can be cooled and stabilized. The ex-vessel behavior of corium involves complex physical and chemical mechanisms of flow propagation, heat transfer, and reactions with sacrificial substrates. In this study, the detailed characteristics of corium flow and heat transfer were investigated by using a commercial CFD code for VULCANO VE-U7 test reported in the literature. The volume-of-fluid (VOF) model was used to predict the interfacial surface formation of corium and the surrounding air, and the discrete ordinate model was adopted to calculate radiation between corium and the surroundings. It was found that cooling via radiation through the top surface of corium had a dominant effect on the temperature and viscosity profiles at the front of the corium flow.
Basic Study on Lift-off Characteristics of Non-Premixed Flames of Methane-Air Jet in a Tube
Kim, Go-Tae ; Kim, Nam-Il ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 431~438
DOI : 10.3795/KSME-B.2011.35.4.431
Flame lift-off conditions determine the operating conditions of burners. It is known that a flame can be lifted when the Schmidt number (Sc), which is the ratio of the dynamic viscosity to the mass diffusivity, is greater than unity. In this study, the flame lift-off characteristics of non-premixed flames of propane (Sc > 1) and methane (Sc < 1) in a coaxial outer air tube were experimentally compared. The experimental results indicated that stable lifted flames could be obtained even when Sc < 1 in a confined air tube. On the basis of the results of a simple numerical analysis, it was confirmed that a new flame stabilization mechanism exists in the tube. A velocity field is preferentially developed upstream of the flame, and it results in a new stabilization condition. This result can be very useful in explaining the stabilization of the flames of ordinary burners in which a flame is produced in a confined space.
Test Gases for Gas Burning Appliances of New Gas Group
Ha, Young-Cheol ; Kim, Sung-Min ; Lee, Chang-Eon ; Choi, Kyoung-Seok ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 4, 2011, Pages 439~444
DOI : 10.3795/KSME-B.2011.35.4.439
To determine the test gases for gas appliances of new gas group, the interrelation between gas interchangeability, including thermal efficiency, of 13A gas appliances and present 13A test gases was experimentally investigated. The test results show that the Wobbe indices in the case of incomplete combustion and the flame lifting limit gas for the new gas group are respectively 2% higher than the upper limit and 1% lower than the lower limit of the Wobbe index range. The most suitable composition of R gas is 96 mol% of methane and 4 mol% of propane; LNG could be also used as R gas. Further, analysis results showed that the hydrogen concentration of flash back limit gas could be lowered from 30 vol% to 23 vol%.