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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
Editor in Chief :
Volume & Issues
Volume 38, Issue 12 - Dec 2014
Volume 38, Issue 11 - Nov 2014
Volume 38, Issue 10 - Oct 2014
Volume 38, Issue 9 - Sep 2014
Volume 38, Issue 8 - Aug 2014
Volume 38, Issue 7 - Jul 2014
Volume 38, Issue 6 - Jun 2014
Volume 38, Issue 5 - May 2014
Volume 38, Issue 4 - Apr 2014
Volume 38, Issue 3 - Mar 2014
Volume 38, Issue 2 - Feb 2014
Volume 38, Issue 1 - Jan 2014
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Quantitative Method to Measure Thermal Conductivity of One-Dimensional Nanostructures Based on Scanning Thermal Wave Microscopy
Park, Kyung Bae ; Chung, Jae Hun ; Hwang, Gwang Seok ; Jung, Eui Han ; Kwon, Oh Myoung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 957~962
DOI : 10.3795/KSME-B.2014.38.12.957
We present a method to quantitatively measure the thermal conductivity of one-dimensional nanostructures by utilizing scanning thermal wave microscopy (STWM) at a nanoscale spatial resolution. In this paper, we explain the principle for measuring the thermal diffusivity of one-dimensional nanostructures using STWM and the theoretical analysis procedure for quantifying the thermal diffusivity. The SWTM measurement method obtains the thermal conductivity by measuring the thermal diffusivity, which has only a phase lag relative to the distance corresponding to the transferred thermal wave. It is not affected by the thermal contact resistances between the heat source and nanostructure and between the nanostructure and probe. Thus, the heat flux applied to the nanostructure is accurately obtained. The proposed method provides a very simple and quantitative measurement relative to conventional measurement techniques.
Effect of Ash Content on Unburned Carbon and NOx Emission in a Drop Tube Furnace
Kim, Sang-In ; Lee, Byoung-Hwa ; An, Ke-Ju ; Kim, Man-Cheol ; Kim, Seung-Mo ; Jeon, Chung-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 963~969
DOI : 10.3795/KSME-B.2014.38.12.963
Four coal sources that had different ash contents were evaluated in a drop tube furnace (DTF). Combustion experiments were conducted by using several sources with different particle sizes and excess air ratios under air-staging conditions to determine the optimized combustion conditions of high-ash coal, with an emphasis on the combustion efficiency and NOx emissions. The results show that the higher ash content results in a large amount of carbon remaining unburned, and that this effect is dominant when the largest particle size is used. Furthermore, the ash content of coal does affect the Char-NOx concentration, which decreases with the particle size. The results of this study suggest that an air-staged system can be useful to reduce the NOx emissions of high-ash coal and that control of the air stoichiometric ratio of the primary combustion zone (SR1) is effective for reducing NOx emissions, especially by considering unburned carbon contents.
Estimation of Stroke Volume Based on Air Pressure in Air Tube with Pneumatic Pulsatile Ventricular Assist Device
Kang, Yu Min ; Lee, Jin Hong ; Her, Keun ; Choi, Seong Wook ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 971~974
DOI : 10.3795/KSME-B.2014.38.12.971
A ventricular assist device (VAD) is used for bridge to heart transplantation and heart diseases. Knowing the status of a pneumatic pulsatile VAD when implanting it into the body is important: when the velocity of blood flow through the VAD is slow, a thrombus may occur, and thrombosis can be fatal to a patient. In order to determine the state of a VAD, various sensors need to be implanted. Because this introduces the risk of infection and difficulties with sensor management, we developed a method for estimating the state of a VAD indirectly via the pressure in an air tube that can be measured in vitro. We compared the measured values to in vitro experimental results. The estimated and measured values showed some errors, but the accuracy can be improved by refining the estimation process to minimize the risk of infection.
Effect of Inner Circular Cylinder Size on Three-Dimensional Natural Convection in Cubical Enclosure
Seo, Young Min ; Choi, Changyoung ; Ha, Man Yeong ; Park, Sang Hu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 975~982
DOI : 10.3795/KSME-B.2014.38.12.975
This study evaluates the effect of a heated circular cylinder's size on three-dimensional natural convection in a cubical enclosure. The Rayleigh number was varied between
, and the Prandtl number was maintained at 0.7. In this study, the radius of the circular cylinder was changed by 0.1 L within a range of 0.1-0.4 L. The thermal and fluid flow characteristics were regarded to be independent of time in the range of the Rayleigh number and cylinder radius considered in this study. The surface-averaged Nusselt numbers of the cylinder and the enclosure were found to increase with the increase in the radius of the cylinder. The effect of the cylinder's size on natural convection in the enclosure was analyzed across the thermal and flow fields, and the distributions of the Nusselt numbers.
Development of Thermocouple Sensor for Thermal Boundary Layer Measurement
Seo, Jongbeom ; Han, S. ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 983~990
DOI : 10.3795/KSME-B.2014.38.12.983
This research focused on designing an appropriate thermocouple sensor for a thermal boundary layer with a large temperature gradient. It was designed to minimize the conduction error from a constant temperature wall in a boundary layer. A
thermocouple was chosen, and a five-axis device jig was developed to fabricate a butt-welded thermocouple, which is different from arc-welded junction thermocouples. This was used to minimize the size of the thermocouple junction. In addition to fabricating butt-welded thermocouples, a thorough calibration was conducted to decrease the internal error of a multimeter to ensure that the data from the butt-welded and regular thermocouples were almost the same. Based on this method, a butt-welded thermocouple with a small junction was found to be suitable for measuring the temperature in a thermal boundary layer with very large thermal gradients. Using this thermal boundary layer probe, the thermal boundary layers in a turbine cascade were measured, and the Nusselt numbers were obtained for the turbine endwall.
Measurements of Five-Hole Pressure Probe on Swirling Flow Fields of Gun-Type Gas Burner for Furnace
Kim, Jang Kweon ; Oh, Seok Hyung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 991~997
DOI : 10.3795/KSME-B.2014.38.12.991
This study investigated the swirling flow fields of a gun-type gas burner (GTGB) without a combustion chamber under cold flow conditions. Three velocity components and the static pressure were measured with a straight-type five-hole pressure probe (GHPP) using a non-nulling calibration method and compared with the results of an X-type hot-wire probe (X-probe) and computational fluid dynamics (CFD). The GHPP measured the velocity and static pressure for the swirling flow of the central region of the GTGB better than the X-probe but produced slightly worse results than the CFD.
Heat Transfer Enhancement in Channel Flow by a Streamwise-Periodic Array of Rotating Circular Cylinders
Jeong, Taekyeong ; Yang, Kyung-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 999~1008
DOI : 10.3795/KSME-B.2014.38.12.999
In this study, we consider the heat transfer characteristics of channel flow in the presence of an infinite streamwise array of equispaced identical rotating circular cylinders. This flow configuration can be regarded as a model representing a micro channel or an internal heat exchanger with cylindrical vortex generators. A numerical parametric study has been carried out by varying Reynolds number based on the bulk mean velocity and the cylinder diameter, and the gap between the cylinders and the channel wall for some selected angular speeds. The presence of the rotating circular cylinders arranged periodically in the streamwise direction causes a significant topological change of the flow, leading to heat transfer enhancement on the channel walls. More quantitative results as well as qualitative physical explanations are presented to justify the effectiveness of varying the gap to enhance heat transfer from the channel walls.
Effect of Non-Equilibrium Condensation on Force Coefficients in Transonic Airfoil Flow
Jeon, Heung Kyun ; Choi, Seung Min ; Kang, Hui Bo ; Kwon, Young Doo ; Kwon, Soon Bum ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 1009~1015
DOI : 10.3795/KSME-B.2014.38.12.1009
The present study investigated the effects of non-equilibrium condensation with the angle of attack on the coefficients of pressure, lift, and drag in the transonic 2-D flow of NACA0012 by numerical analysis of the total variation diminishing (TVD) scheme. At
, the lift coefficients for
and 0.81 decreased monotonically with increasing
. In contrast, for
corresponding to the Mach number of the force break,
increased markedly as
increased. However, at
, which corresponded to the case of the condensation having a large influence,
increased slightly as
increased. The decrease in profile drag by non-equilibrium condensation grew as the angle of attack and stagnation relative humidity increased for the same free stream transonic Mach number. At
, the coefficient of the wave drag increased with the attack angle and free stream Mach number. When
> 50%, the coefficient of the wave drag decreased as
increased the maximum Mach number.
Study on NOx Reduction with Multi-Perforated Tube Geometry in Integrated Urea-SCR Muffler
Moon, Namsoo ; Lee, Sangkyoo ; Ko, Sangchul ; Lee, Jeekeun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 1017~1026
DOI : 10.3795/KSME-B.2014.38.12.1017
A multi-perforated tube is generally installed between the muffler inlet and in front of selective catalytic reduction (SCR) catalysts in the integrated urea-SCR muffler system in order to disperse the urea-water solution spray uniformly and to make better use of the SCR catalyst, which would result in an increase nitrogen oxide (
) reduction efficiency and a decrease in the ammonia slip. The effects of the multi-perforated tube orifice area ratios on the internal flow characteristics were investigated analytically by using a general-purpose commercial software package. From the results, it was clarified that the multi-perforated tube geometry sensitively affected the generation of the bulk swirling motion inside the plenum chamber set in front of the SCR catalyst and to the uniformity index of the velocity distribution produced at the inlet of the catalyst. To verify the analytical results, engine tests were carried out in the ESC and ETC modes. Results of these tests indicated that the larger flow model in the longitudinal direction showed the highest NOx reduction efficiency, which was a good agreement with the analytical results.
Design of Reduced Shear Stress with High-Viscosity Flow Using Characteristics of Thin Film Flow on Solid Surfaces
Park, Boo Seong ; Kim, Bo Hung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 1027~1034
DOI : 10.3795/KSME-B.2014.38.12.1027
The shear stress on a surface due to the thin film fluid flow is an important issue. In case of a rotating disk, the fluid is delivered to the edge of the disk by centrifugal force, which acts as a body force on the fluid. Wear of a surface is affected by the shear stress acting on the surface and curvature. In this study, we utilize computational fluid dynamics software to model the ratio of curvature and local shear stress on solid surfaces. The key goal of the study is to determine an optimized curvature for the thin film fluid flow on a solid surface in order to minimize the local shear stress affecting the wear of this surface. Our results on the effects of curvature will be utilized for the design of devices that utilize thin film fluid flow on a solid surface, such as rotating-disk spray systems and thin film coating.
A Study on Friction Loss of Engine using Microfluidics Approach
Park, Cho Hee ; Kim, Bo Hung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 1035~1042
DOI : 10.3795/KSME-B.2014.38.12.1035
Reducing the friction of engine parts is an important issue in engine design. The loss of energy in the piston assembly due to mechanical friction ranges from 40 to 55%, and there is an increase in the total energy of about 5% if the friction of the piston can be removed. In order to reduce the friction loss at the level of each engine part, it is necessary to perform a comparative analysis with other engines to determine the important factors affecting the energy loss. Several studies have been performed to analyze the lubrication based on hydrodynamic modeling, since a piston lubrication system has dimensions in the nanoscale to microscale domain. Therefore, it is necessary to determine the correlations between the molecular and continuum systems. In this study, we investigated the friction changes due to the various interactions between molecules in the wall/fluid interface, where a microscopic movement of the oil film occurs along the cylinder liner of the engine.
Numerical Study on Draining from Cylindrical Tank Using Stepped Drain Port
Son, Jong Hyeon ; Park, Il Seouk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 1043~1050
DOI : 10.3795/KSME-B.2014.38.12.1043
An air-core vortex is generated during draining after stirring a rotating cylindrical tank or after filling it with water. The formation of the air-core vortex and the time of its formation are dependent on drain conditions such as the dimensions of the tank, the initial rotation or stirring speed, and the shape of the drain port. In this study, a draining process using a two-stage drain port was numerically investigated. The length and radius of the first drain stage located in the lower part of the drain port were kept constant, whereas the radius of the second drain stage was varied for simulating the draining process. The simulation was conducted by considering an axisymmetric swirling flow for all cases. The declining water level was monitored by an interface capturing method. Further, the effects of the radius of the second drain stage on the time of formation of the air-core vortex and the internal flow structure were investigated.
Numerical Analysis of Simultaneous Cooling Process of Upper and Lower Side of Running Hot Steel Strip
Kwon, Myeon Jae ; Park, Il Seouk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 1051~1056
DOI : 10.3795/KSME-B.2014.38.12.1051
After hot rolling, a high-temperature steel plate with a temperature higher than
is rapidly cooled by multiple circular water jets. In this cooling process, because the temperature of the steel plate is much higher than the boiling point of the cooling water, film-boiling heat transfer occurs and a very thin steam layer forms between the plate surface and the cooling water. The steam layer acts as a thermal resistance that prevents heat transfer between the cooling water and the steel plate. In addition to the film-boiling heat transfer, complex physical phenomena such as the free-surface flow of residual water that accumulated on the material and the material's high-speed motion also occur in the cooling process. In this study, the simultaneous cooling process of the upper and lower sides of a running hot steel strip is investigated using a three-dimensional numerical model and the cooling performances and characteristics of the upper-side cooling and lower-side cooling are compared.
Design and Configuration of 200kW Organic Rankine Cycle Turbine
Han, Sangjo ; Seo, JongBeom ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 1057~1064
DOI : 10.3795/KSME-B.2014.38.12.1057
Recently, there has been a growing interest in sustainable energy. One method that has been used is an organic Rankine cycle using conventional turbine technology with a low-temperature waste heat source. A 200-kW organic Rankine cycle (ORC) system was designed for a waste heat recovery application using R245fa as the working fluid. A radial turbine running at 15,000 rpm was employed to generate more than 200 kW with an expansion ratio of nine. Because an ORC turbine uses a refrigerant as the working fluid, the ideal gas law was not employed to design the turbine. In addition, the complexity of the molecular structure of R245fa made it difficult to design the turbine. Because R245fa has an Ma value of one at a low velocity for the working fluid (about 1/3 of the speed of sound in air) at about
, it easily reaches a supersonic flow condition with a small pressure expansion. To increase the efficiency of the turbine, a dual stage radial-type turbine with a subsonic speed was suggested. This paper will describe the design procedure and performance evaluation of the ORC turbine using R245fa.
Performance Enhancement of Dual-Inlet Centrifugal Blower by Optimal Design of Splitter
Lee, Jong Sung ; Jang, Choon Man ;
Transactions of the Korean Society of Mechanical Engineers B, volume 38, issue 12, 2014, Pages 1065~1072
DOI : 10.3795/KSME-B.2014.38.12.1065
The shape of an impeller splitter for a dual-inlet centrifugal blower was optimized to enhance the blower performance. Two design variable, the normalized chord and pitch of a splitter, were used to evaluate the blower performance and internal flow fields based on the three-dimensional flow analysis. The blower performance obtained using this numerical simulation had a maximum error of 4 percent compared to that in an experiment at the design flow condition. The shape optimization of the splitter successfully increased the blower efficiency and pressure by 3.65 and 1.14 percent compared to the reference values. The blower performance was increased by reducing the flow separation near the blade suction surface by optimizing the shape of the splitter, which produced a pressure increase at the outlet of the volute casing.