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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 36, Issue 12 - Dec 2012
Volume 36, Issue 11 - Nov 2012
Volume 36, Issue 10 - Oct 2012
Volume 36, Issue 9 - Sep 2012
Volume 36, Issue 8 - Aug 2012
Volume 36, Issue 7 - Jul 2012
Volume 36, Issue 6 - Jun 2012
Volume 36, Issue 5 - May 2012
Volume 36, Issue 4 - Apr 2012
Volume 36, Issue 3 - Mar 2012
Volume 36, Issue 2 - Feb 2012
Volume 36, Issue 1 - Jan 2012
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Numerical Simulation of the Fully Developed Flow and Heat Transfer of a Plate Heat Exchanger Taking into Account Variation in the Corrugation Height
Moh, Jeong-Hah ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 1~8
DOI : 10.3795/KSME-B.2012.36.1.001
Numerical analysis has been carried out to investigate the fully developed flow and heat transfer characteristics of a plate heat exchanger. Multi-cell models with an inlet part and outlet part are used to perform the numerical simulation. The plate heat exchanger is characterized by a chevron angle of
and a P/H ratio of 2.0~4.0. The working fluid is water and the Reynolds numbers range from 300 to 1,500. The correlation is given in the form of
for the friction factor and
for the Colburn factor. It is found that the fully developed flow starts from the third cell and the Nusselt number increases with decreasing P/H ratios.
Measuring Convective Heat Transfer Coefficients of Nanofluids over a Circular Fine Wire Maintaining a Constant Temperature
Lee, Shin-Pyo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 9~16
DOI : 10.3795/KSME-B.2012.36.1.009
This paper describes a measuring apparatus that can be used to appraise the effectiveness of nanofluids as new heat-transfer-enhancing fluids. A couple of apparatuses using fine hot wires as sensors have been proposed for this purpose; however, they have a technical weakness related to the uncertain working conditions of the sensor. The present method uses the convective heat transfer coefficient from a hot wire as an indication of the heat transfer effectiveness of the nanofluid, where the temperature of the wire remains constant during the experiment. The operating principle and experimental procedure are explained in detail, and the validity of the system is tested with pure base fluids. The effects of particle concentration, velocity, and temperature on the heat transfer coefficients of the nanofluids are discussed comprehensively using the experimental data for graphite nanolubrication oil.
Simulation Study on the Cooling Performance of the Two-Stage Compression CO
Cycle with the a Flash Intercooler and Flash Gas Bypass
Kwak, Myoung-Seok ; Cho, Hong-Hyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 17~24
DOI : 10.3795/KSME-B.2012.36.1.017
There has been little study on the performance characteristics of the effective heat pump systems in the cooling mode using the two-stage compression cycles have hardly performed. In this study, the performance of the two-stage compression
cycle with an FI (flash intercooler) and the FGB (flash gas bypass) was investigated by using a theoretical method. The performance analysis was carried out with aby varyingiation (the indoor temperature, outdoor temperature, and 1st- and 2nd-stage EEV openings. As of a result, the coefficients of performance (COPs) of the Bbasic, FI, and FGB cycles were decreased by 28.5%, 22.1%, and 24.5%, respectively, for various outdoor temperature conditions. In addition to, the performance variation of the two-stage compression cycle was smaller than that of the single-stage compression cycle. The performance of the FI and FGB cycles was improved by 13.5%, and 6.9%, respectively, when the 1st-stage EEV opening was increased from 32% to 48%, and by 0.9%, and 2.6%, respectively, when the 1st- andthe 2nd-stage EEV opening was increased from 32% to 48%, andwas increased from 42% to 58%, respectively. The FI cycle showed anthe most improved performance for any given operating conditions.
Fabrication and Analysis of a Free-Standing Carbon Nanotube-Metal Hybrid Nanostructure
Chang, Won-Seok ; Hwang, Jun-Yeon ; Han, Chang-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 25~29
DOI : 10.3795/KSME-B.2012.36.1.025
The properties of carbon nanotube-metal hybrid nanostructures are critically dependent on the structure and chemistry of the metal-carbon nanotube interface. In this study, the interface between nickel and multi-walled carbon nanotubes (CNTs) has been investigated using physical vapor-deposited (sputter-deposited) nickel onto the surface of freestanding carbon nanotube arrays processed by nano-imprint lithography (NIL). These interfaces have been characterized by transmission electron microscopy and 3D atom probe tomography. In the nickel nanocrystals growing on the CNT surface, a metastable hexagonal
-types phase appears to be stabilized. The structural stability of the nickel-CNT interface is also discussed and related to potential implications for the properties of these nanocomposites.
Comparison of Control Strategies for Military Series-Type HEVs in Terms of Fuel Economy Based on Vehicle Simulation
Jung, Dae-Bong ; Kim, Hyung-Jun ; Kang, Hyung-Mook ; Park, Jae-Man ; Min, Kyoung-Doug ; Seo, Jung-Il ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 31~36
DOI : 10.3795/KSME-B.2012.36.1.031
Military vehicles, compared to conventional vehicles, require higher driving performance, quieter operation, and longer driving distances with minimal fuel supplies. The series hybrid electric vehicle can be driven with no noise and has high initial startup performance, because it uses only a traction motor that has a high startup torque to drive the vehicle. Moreover, the fuel economy can be improved if the vehicle is hybridized. In series hybrid electric vehicles, the electric generation system, which consists of an engine and a generator, supplies electric energy to a battery or traction motor depending on the vehicle driving state and battery state of charge (SOC). The control strategy determines the operation of the generation system. Thus, the fuel economy of the series hybrid electric vehicle relies on the control strategy. In this study, thermostat, power-follower, and combined strategies were compared, and a 37% improvement in the fuel economy was implemented using the combined control strategy suggested in this study.
Experimental Study on Development of Air Leakage Model and Performance Characteristics of a Desiccant Rotor
Kang, Byung-Ha ; Pi, Chang-Hun ; Chang, Young-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 37~45
DOI : 10.3795/KSME-B.2012.36.1.037
This study investigates the pressure leakage characteristics of a desiccant rotor with a brush-type air seal. Through a pressure leakage experiment, a correlation equation for the leakage air flow rate is obtained as a function of the air seal area and pressure difference. Using this equation, an air leakage model for the desiccant rotor is developed. By comparing simulation results with the experimental results for the desiccant rotor, the accuracy of the air leakage model is demonstrated. A performance test of a desiccant rotor with various air flow rates is carried out. Using the air leakage model, the effective mass flow rate and air leakage rate are found. In addition, the characteristics of the air leakage are analyzed for a desiccant cooling system using the developed air leakage model.
Drag Force on Bubbles for Fluidic Self-Assembly
Im, Hyeon-Seung ; Lee, Sung-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 47~54
DOI : 10.3795/KSME-B.2012.36.1.047
We developed a novel method of fluidic self-assembly to replace the conventional pick-and-place method. This method is cheaper and more effective than the previous method. For this research, we compared mathematical models with experimental results using the parameters of the drag force, the capillary force, and the restoring force for effective chip assembly, and the results for the alignment to the substrate. We obtained a 96.5% attach rate and
-misalignment to the substrate in a 500
Flow-induced Vibration Characteristics of Two Circular Cylinders in a Side-by-Side Arrangement and the Vibration Mechanism
Kim, Sang-Il ; Lee, Seung-Chul ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 55~60
DOI : 10.3795/KSME-B.2012.36.1.055
This experimental study investigated the characteristics of flow-induced vibration of two elastically supported circular cylinders in a side-by-side arrangement. In particular, the characteristics of the flow-induced vibration of the two cylinders are investigated by changing the flow speed at each spacing ratio L/D (L is the space between two cylinders and D is the diameter of the cylinder). To clarify the mechanism generating the flow-induced vibration of the cylinders, the flow patterns around the two vibrating cylinders are also investigated using a flow visualization test that reproduces the flow-induced vibration of the cylinders with a forced vibration apparatus. As a result, it is clarified that the flow-induced vibration characteristics of the two cylinders arranged side-by-side switch among four patterns as the flow between the two cylinders is switched. Among the three arrangements considered (tandem, staggered, and side-by-side), the arrangement that generates flow-induced vibration of the two cylinders most easily is the side-by-side arrangement.
Effect of Nonequilibrium Condensation on the Oscillation of the Terminating Shock in a Transonic Airfoil Flow
Kim, Jin-Soo ; Lee, Sung-Jin ; Alam, Miah Md. Ashraful ; Kwon, Soon-Bum ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 61~66
DOI : 10.3795/KSME-B.2012.36.1.061
In this study, to find the effect of nonequilibrium condensation on the oscillation of the terminating shock wave in transonic flows, an NACA0014 airfoil flow with nonequilibrium condensation is analyzed using the total variation diminishing (TVD) numerical scheme. Transonic free stream Mach numbers of 0.81-0.87 are tested with variations in the stagnation relative humidity. For the same free stream Mach number and attack angle of
, an increase in the stagnation relative humidity attenuates the strength of the terminating shock and reduces the oscillation of the terminating shock wave. Furthermore, for the same stagnation relative humidity, the larger the free stream Mach number becomes, the shorter the period of the oscillation shock wave is. The excursion distance of the oscillation shock increases with the free stream Mach numbers for the same stagnation relative humidity. Finally, it is found that for the same shock location, the strength of the oscillating shock facing upstream is stronger than that facing downstream.
Numerical Study of Gap Size Ratio Effect for Noncondensable Gas Ventilation in Condensers
Je, Jun-Ho ; Kim, Soo-Jea ; Choi, Chi-Woong ; Kim, Moo-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 67~74
DOI : 10.3795/KSME-B.2012.36.1.067
A numerical analysis was carried out to estimate the effect of the gap size ratio on the performance of condensers under noncondensable gas ventilation using the porous medium approach (PMA). In the PMA, the details of the tube bundle in the condenser are considered to be those of a porous medium, and the flow resistance term is added in the momentum equation. Three-dimensional analysis of the condensation for a McAllister condenser was conducted with the PMA using Fluent and user-defined functions (UDFs). The gap size effect on the condensation was negligible under pure steam conditions. However, the gap size effect was dominant in condensation with noncondensable gas and external venting. As the gap size decreased, the condensation rate increased for noncondensable gas in an external venting system.
Effect of Hydrogen Addition on Autoignited Methane Lifted Flames
Choi, Byung-Chul ; Chung, Suk-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 75~81
DOI : 10.3795/KSME-B.2012.36.1.075
Autoignited lifted flames in laminar jets with hydrogen-enriched methane fuels have been investigated experimentally in heated coflow air. The results showed that the autoignited lifted flame of the methane/hydrogen mixture, which had an initial temperature over 920 K, the threshold temperature for autoignition in methane jets, exhibited features typical of either a tribrachial edge or mild combustion depending on fuel mole fraction and the liftoff height increased with jet velocity. The liftoff height in the hydrogen-assisted autoignition regime was dependent on the square of the adiabatic ignition delay time for the addition of small amounts of hydrogen, as was the case for pure methane jets. When the initial temperature was below 920 K, where the methane fuel did not show autoignition behavior, the flame was autoignited by the addition of hydrogen, which is an ignition improver. The liftoff height demonstrated a unique feature in that it decreased nonlinearly as the jet velocity increased. The differential diffusion of hydrogen is expected to play a crucial role in the decrease in the liftoff height with increasing jet velocity.
Measurement of the Void Fraction of Slug and Bubbly Flows Using Three-Ring Impedance Meters
Kim, Jong-Rok ; Ahn, Yeh-Chan ; Kim, Moo-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 83~88
DOI : 10.3795/KSME-B.2012.36.1.083
Real slug and bubbly flows were measured using a three-ring impedance meter that can efficiently measure the void fraction of two-phase flows in a tube. First, the fitting curves between the signal from the impedance meters and the void fraction were found. The impedance meter had different fitting curves for slug and bubbly flows that had the same void fraction. An impedance meter should choose one of the two fitting curves according to the flow pattern, and the flow patterns can be recognized using the measured void fraction. The velocities and sizes of the bubbles were calculated using the void fraction curves measured by two impedance meters.
Microchannels for the Flow Control of Two Fluids with Different Volumes
La, Moon-Woo ; Ho, Jae-Yun ; Kim, Dong-Sung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 89~95
DOI : 10.3795/KSME-B.2012.36.1.089
In this paper, microchannels for the flow control of two fluids with different volumes have been designed, fabricated, and verified. The dimensions of the inlets were determined based on the Stokes equation in order to realize that the flow of the two fluids meet at the same time, and to maintain a certain configuration when the flows passed through each inlet channel. The designed microchannels were confirmed using computational fluid dynamics simulation for the incompressible, Newtonian, and transient flows. In addition, a microfluidic system containing the designed microchannels was fabricated by soft lithography, and the pressure-driven flows of the two fluids were characterized by microfluidic experiments.
Thermal Analysis of Vegetable Insulation Oil for Hermetically Sealed Wind Turbine Transformer
Lee, Sung-Won ; Lee, Joon-Yeob ; Kim, Jun-Su ; Woo, Jae-Hi ; Kim, Dong-Hae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 97~102
DOI : 10.3795/KSME-B.2012.36.1.097
A hermetically sealed oil transformer is designed by applying expanding function of the tank due to the volume changes of the insulation oil according to the temperature rises. When the insulation oil expands, an increase in the volume of the corrugated fin prevents a pressure rise of the transformer. For a wind turbine transformer, a vegetable-oil-immersed transformer has the advantages of excellent biodegradation and fire-resistant properties like an exceptionally high fire point. When vegetable oil is substituted for mineral oil, however, the maximum winding temperature rises because of the decrease in the internal circulation flow rate resulting from the variations of the oil's physical characteristics, such as density and viscosity. The purpose of this study is to develop a hermetically sealed vegetable oil transformer that can be applied in a wind turbine and to analyze the thermal stability of the active part of the transformer to deal with pressure variations due to the temperature changes. In addition, thermal tests for the vegetable oil transformer have been performed, and the measured values are compared with the analysis results.
Numerical Study on the Flow and Combustion Characteristics in Swirl-Premix Burners
Lim, Jun-Seok ; Lee, Jong-Hyeok ; Baek, Gwang-Min ; Cho, Ju-Hyeong ; Kim, Han-Seok ; Sohn, Chae-Hoon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 36, issue 1, 2012, Pages 103~110
DOI : 10.3795/KSME-B.2012.36.1.103
The flow field, fuel-air mixing, and behaviors of turbulent flames have been investigated using the large eddy simulation (LES) numerical technique in a premixed swirl combustor equipped with EV double cone burners. Recirculation zones are generated by the swirl burner, and lean premixed flames are formed within a distance of 0.2 m from the tip of the burner. NOx emission of 0.46 ppm is predicted at 1 atm and an air/fuel ratio of 38.7. However, most of the CO generated in a flame front continues to be oxidized as it moves toward the exit, and CO emission of 5.45 ppm is predicted at the exit. The NOx emission can be reduced by decreasing the pressure and air/fuel ratio. The characteristics of NOx emission have been investigated through RANS simulations for various fuel injection types, and it is found thereby that five-lance-hole injection produces the lowest NOx emission rate.