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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
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 40, Issue 9 - Sep 2016
Volume 40, Issue 8 - Aug 2016
Volume 40, Issue 7 - Jul 2016
Volume 40, Issue 6 - Jun 2016
Volume 40, Issue 5 - May 2016
Volume 40, Issue 4 - Apr 2016
Volume 40, Issue 3 - Mar 2016
Volume 40, Issue 2 - Feb 2016
Volume 40, Issue 1 - Jan 2016
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A Momentum-Exchange/Fictitious Domain-Lattice Boltzmann Method for Solving Particle Suspensions
Jeon, Seok Yun ; Yoon, Joon Yong ; Kim, Chul Kyu ; Shin, Myung Seob ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 6, 2016, Pages 347~355
DOI : 10.3795/KSME-B.2016.40.6.347
This study presents a Lattice Boltzmann Method (LBM) coupled with a momentum-exchange approach/fictitious domain (MEA/FD) method for the simulation of particle suspensions. The method combines the advantages of the LB and the FD methods by using two unrelated meshes, namely, a Eulerian mesh for the flow domain and a Lagrangian mesh for the solid domain. The rigid body conditions are enforced by the momentum-exchange scheme in which the desired value of velocity is imposed directly in the particle inner domain by introducing a pseudo body force to satisfy the constraint of rigid body motion, which is the key idea of a fictitious domain (FD) method. The LB-MEA/FD method has been validated by simulating two different cases, and the results have been compared with those through other methods. The numerical evidence illustrated the capability and robustness of the present method for simulating particle suspensions.
Study on the Performance of a Centrifugal Compressor Using Fluid-Structure Interaction Method
Lee, Horim ; Kim, Changhee ; Yang, Jangsik ; Son, Changmin ; Hwang, Yoonjei ; Jeong, Jinhee ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 6, 2016, Pages 357~363
DOI : 10.3795/KSME-B.2016.40.6.357
In this study, we perform a series of aero-thermo-mechanical analyses to predict the running-tip clearance and the effects of impeller deformation on the performance using a centrifugal compressor. During operation, the impeller deformation due to a combination of the centrifugal force, aerodynamic pressure and the thermal load results in a non-uniform tip clearance profile. For the prediction, we employ the one-way fluid-structure interaction (FSI) method using CFX 14.5 and ANSYS. The predicted running tip clearance shows a non-uniform profile over the entire flow passage. In particular, a significant reduction of the tip clearance height occurred at the leading and trailing edges of the impeller. Because of the reduction of the tip clearance, the tip leakage flow decreased by 19.4%. In addition, the polytrophic efficiency under operating conditions increased by 0.72%. These findings confirm that the prediction of the running tip clearance and its impact on compressor performance is an important area that requires further investigation.
Numerical Study of Aggregation and Breakage of Particles in Taylor Reactor
Lee, Seung Hun ; Jeon, Dong Hyup ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 6, 2016, Pages 365~372
DOI : 10.3795/KSME-B.2016.40.6.365
Using the computational fluid dynamics (CFD) technique, we simulated the fluid flow in a Taylor reactor considering the aggregation and breakage of particles. We calculated the population balance equation (PBE) to determine the particle-size distribution by implementing the quadrature method-of-moment (QMOM). It was used that six moments for an initial moments, the sum of Brownian kernel and turbulent kernel for aggregation kernel, and power-law kernel for breakage kernel. We predicted the final mean particle size when the particle had various initial volume fraction values. The result showed that the mean particle size and initial growth rate increased as the initial volume fraction of the particle increased.
Characteristics of Flowfield of a Circular Cylinder Having a Detached Splitter Plate with High Reynolds Number
Ro, Ki Deok ; Lee, Han Gyun ; Lee, Jong Ho ; Lee, Jeong Min ; Shin, Jin Ho ; Cheon, Kang Bin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 6, 2016, Pages 373~381
DOI : 10.3795/KSME-B.2016.40.6.373
In this study, we investigate the characteristics of the drag reduction of a circular cylinder having a detached splitter plate at the wake side. We measure the fluid force on a circular cylinder and visualize the field using particle image velocimetry (PIV) with a high Reynolds number, Re = 10,000. The experimental paraeters used were the width ratios (H/B = 0.5~1.5) of splitters to the prism width and the gap ratios (G/B = 0~2) between the prism and the splitter plate. The drag-reduction rate of the circular cylinder increased with H/B in the case of the same G/B, and it increased and then decreased with G/B in the case of the same H/B. The vortices of the opposite direction on the upper and lower sides of the detached splitter plate were generated by installing the plate. Reverse flow was caused by the vortices at the wake region of the circular cylinder, and the drag of the circular cylinder was decreased by the reverse flow.
Pool Boiling Characteristics on the Microstructured surfaces with Both Rectangular Cavities and Channels
Kim, Dong Eok ; Park, Su Cheong ; Yu, Dong In ; Kim, Moo Hwan ; Ahn, Ho Seon ; Myung, Byung-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 6, 2016, Pages 383~389
DOI : 10.3795/KSME-B.2016.40.6.383
Based on a surface design with rectangular cavities and channels, we investigated the effects of gravity and capillary pressure on pool-boiling Critical Heat Flux (CHF). The microcavity structures could prevent liquid flow by the capillary pressure effect. In addition, the microchannel structures contributed to induce one-dimensional liquid flow on the boiling surface. The relationship between the CHF and capillary flow was clearly established. The driving potentials for the liquid supply into a boiling surface can be generated by the gravitational head and capillary pressure. Through an analysis of pool boiling and visualization data, we reveal that the liquid supplement to maintain the nucleate boiling condition on a boiling surface is closely related to the gravitational pressure head and capillary pressure effect.
Analytic Model for Predicting the Permeability of Foam-type Wick
Ngo, Ich-Long ; Byon, Chan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 6, 2016, Pages 391~396
DOI : 10.3795/KSME-B.2016.40.6.391
Wicks play an important role in determining the thermal performance of heat pipes. Foam-type wicks are known to have good potential for enhancing the capillary performance of conventional types of wicks, and this is because of their high porosity and permeability. In this study, we develop an analytic expression for predicting the permeability of a foam-type wick based on extensive numerical work. The proposed correlation is based on the modified Kozeny-Carman's equation, where the Kozeny-Carman coefficient is given as an exponential function of porosity. The proposed correlations are shown to predict the previous experimental results well for an extensive parametric range. The permeability of the foam-type wick is shown to be significantly higher than that of conventional wicks because of their high porosity.
A Study on the Air Vent Valve of the Hydraulic Servo Actuator for Steam Control of Power Plants
Lee, Yong Bum ; Lee, Jong Jik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 6, 2016, Pages 397~402
DOI : 10.3795/KSME-B.2016.40.6.397
To produce adequate electricity in nuclear and thermal power plants, an optimal amount of steam should be supplied to a generator connected to high- and low-pressure steam turbines. A turbine output control device, which is a special steam valve employed to supply or interrupt the steam to the turbine, is operated using a hydraulic servo actuator. In power plants, the performance of servo actuators is degraded by the air generated from the hydraulic system, or causes frequent failures owing to an increase in the wear of the seal. This is due to the seal being burnt as generated heat using the produced compressed air. Some power plants have exhausted air using a fixed orifice, and thus they encounter power loss due to mass flow exhaust. Failures are generated in hydraulic pumps, electric motors, and valves, which are frequently operated. In this study, we perform modeling and analysis of the load-sensing air-exhaust valves, which can be passed through very fine flow under normal use conditions, and exhaust mass flow air at the beginning stage as with existing fixed orifices. Then, we propose a method to prevent failures due to the compressed air, and to ensure the control accuracy of hydraulic servo actuators.
Numerical Investigation of Cooling Performance of Liquid-cooled Battery in Electric Vehicles
Kwon, Hwabhin ; Park, Heesung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 6, 2016, Pages 403~408
DOI : 10.3795/KSME-B.2016.40.6.403
Lithium-ion batteries are commonly employed in hybrid electric vehicles (HEVs), and achieving high energy density in the battery has been one of the most critical issues in the automotive industry. Because liquid cooling containing antifreeze is important in automotive batteries to enable cold starts, an effective geometric configuration for high-cooling performance should be carefully investigated. Battery cooling with antifreeze has also been considered to realize successful cold starts. In this article, we theoretically investigate a specific property of an antifreeze cooling battery system, and we perform numerical modeling to satisfy the required thermal specifications. Because a typical battery system in HEVs consists of multiple stacked battery cells, the cooling performance is determined mainly by the special properties of antifreeze in the coolant passage, which dissipates heat generated from the battery cells. We propose that the required cooling performance can be realized by performing numerical simulations of different geometric configurations for battery cooling. Furthermore, we perform a theoretical analysis as a design guideline to optimize the cooling performance with minimum power consumption by the cooling pump.
Experimental Study of Energy-Saving Realized with the Improvement of Inner Roughness in Double-Entry Centrifugal Pump
Lim, Sung-Eun ; Sohn, Chang-Hyun ; Ryu, Jung-Yup ;
Transactions of the Korean Society of Mechanical Engineers B, volume 40, issue 6, 2016, Pages 409~415
DOI : 10.3795/KSME-B.2016.40.6.409
In this study, we test the effects of the surface roughness on the hydro efficiency of double-suction centrifugal pumps (
, H = 87 m). The original surface of the impeller and inner casing were coated, resulting in surface-roughness reductions ranging from
. We conducted experimental studies to measure the efficiency of the pumps and operating-pump electro energy variations with different surface roughness values. The experimental results showed that the efficiency of the pumps increased by about 0.8~1.79% and the electric energy of the operating pump was reduced by around 4.38 ~ 6.08%. These results indicate that the performance of the pumps depend largely on the surface roughness of the impeller and inner casing, and by reducing the surface roughness, we can improve the efficiency of the pump and reduce costs by reducing the electric energy consumption.