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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 25, Issue 12 - Dec 2001
Volume 25, Issue 11 - Nov 2001
Volume 25, Issue 10 - Oct 2001
Volume 25, Issue 9 - Sep 2001
Volume 25, Issue 8 - Aug 2001
Volume 25, Issue 7 - Jul 2001
Volume 25, Issue 6 - Jun 2001
Volume 25, Issue 5 - May 2001
Volume 25, Issue 4 - Apr 2001
Volume 25, Issue 3 - Mar 2001
Volume 25, Issue 2 - Feb 2001
Volume 25, Issue 1 - Jan 2001
Selecting the target year
Performance Analysis of the Rectangular Fin
Gang, Hyeong-Seok ; Yun, Se-Chang ; Lee, Seong-Ju ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 1~8
DOI : 10.22634/KSME-B.2001.25.1.1
Performance of a rectangular fin is investigated by a three dimensional analytical method. Heat loss and the temperature obtained from the three dimensional analysis are compared with those calculated from a two dimensional analysis. Fin effectiveness, fin resistance and fin efficiency for the rectangular fin are presented as a function of non-dimensional fin length and fin width. The results are obtained in the following : (1) heat loss calculated from the two dimensional analysis is the same as that obtained from the three dimensional analysis with adiabatic boundary condition in z-direction, (2) heat loss obtained from the two dimensional analysis approaches the value for the three dimensional analysis as the non-dimensional fin width becomes large, (3) fin effectiveness increases as non-dimensional fin length increases and non-dimensional fin width decreases, and vice versa for fin efficiency.
Analysis of Electrical Coagulation of Unipolar Charged Particles in an Alternating Electric Using Moment Method
Ji, Jun-Ho ; Hwang, Jeong-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 9~17
DOI : 10.22634/KSME-B.2001.25.1.9
A numerical study has been carried out on the evolution of the particle size distribution for unipolar charged particles that experience coagulation in an alternating electric field. The collision frequency function of charged particles was analytically derived. The log-normal size distribution function is utilized for representing a poly-disperse size distribution and the moments of the particle size distribution are used to solve the general dynamic equation considering only AC electric force effect. The results are compared with the effects of brownian coagulation.
Wall Shear Stress Between Compliant Plates Under Oscillatory Flow Conditions: Influence of Wall Motion, Impedance Phase Angle and Non-Newtonian Fluid
Choe, Ju-Hwan ; Lee, Jong-Seon ; Kim, Chan-Jung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 18~28
DOI : 10.22634/KSME-B.2001.25.1.18
The present study investigates flow dynamics between two dimensional compliant plates under sinusoidal flow conditions in order to understand influence of wall motion, impedance phase angle (time delay between pressure and flow waveforms), and non-Newtonian fluid on wall shear stress using computational fluid dynamics. The results showed that wall motion induced additional terms in the streamwise velocity profile and the pressure gradient. These additional terms due to wall motion reduced the amplitude of wall shear stress and also changed the mean wall shear stress. The trend of the changes was very different depending on the impedance phase angle. As the impedance phase angle was changed to more negative values, the mean wall shear stress decreased while the amplitude of wall shear stress increased. As the phase angle was reduced from 0°to -90°under
4% wall motion, the mean wall shear stress decreased by 12% and the amplitude of wall shear stress increased by 9%. Therefore, for hypertensive patients who have large negative phase angles, the ratio of amplitude and mean of the wall shear stress is raised resulting in a more vulnerable state to atherosclerosis according to the low and oscillatory shear stress theory. We also found that non-Newtonian characteristics of the blood protect atherosclerosis by decreasing the oscillatory shear index.
A Numerical Study on Radiation-Induced Oscillatory Instability in CH
/Air Diffusion Flames
Son, Chae-Hun ; Jeong, Seok-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 29~35
DOI : 10.22634/KSME-B.2001.25.1.29
Radiation-induced oscillatory instability in CH
/Air diffusion flames is numerically investigated by adopting detailed chemistry. Counterflow diffusion flame is employed as a model flamelet and optically thin gas-phase radiation is assumed. Attention is focused on the extinction regime induced by radiative heat loss, which occurs at low strain rate. Once a steady flame structure is obtained for a prescribed value of initial strain rate, transient solution of the flame is calculated after a finite amount of strain-rate perturbation is imposed on the steady flame. Depending on the initial strain rate and the amount of perturbed strain rate, transient evolution of the flame exhibits various types of flame-evolution behaviors. Basically, the dynamic behaviors can be classified into two types, namely oscillatory decaying solution and diverging solution leading to extinction.
Finite Element Analysis for Drying Process of Ceramic Electric Insulator Considering Heat and Moisture Transfer
Geum, Yeong-Tak ; Jeong, Jun-Ho ; Kim, Jun-Han ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 36~46
DOI : 10.22634/KSME-B.2001.25.1.36
Finite element analyses of the ceramic drying process are performed. The heat and moisture movements in green ceramics caused by temperature gradient, moisture gradient, conduction, convection and evaporation are considered. The finite element formulation for solving the temperature and moisture distributions which not only change the volume but also induce the hygro-thermal stress is carried out. In order to verify the formulation, the drying process of a ceramic electric insulator is simulated. Temperature distribution, moisture distribution, and hygro-thermal stress are compared with those of other researcher. Good agreements are achieved.
Thermal Diffusivity Measurement for Metal Using Phase Curve of Photothermal Displacement
Lee, Eun-Ho ; Lee, Gwang-Jae ; Yu, Jae-Seok ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 47~53
DOI : 10.22634/KSME-B.2001.25.1.47
As the technology has developed and new materials have been produced, it is important to measure the thermal diffusivity of material and to predict the heat transfer in the solid subject to thermal processes. This measurement can be done in a non-contact way using photothermal displacenent spectroscopy. In this study, photothermal displacement method was used to measure the thermal diffusivity quantitatively. The specimens used in this study were the pure materials. The Ar-ion laser was used as an energy source and the periodical deformation induced by this pump laser was detected by the He-Ne laser. The magnitude and the phase angle of deformation gradient were measured. The thermal diffusivity was obtained by analyzing the phase angle of deformation gradient. As the result, comparing with the literature value, the thermal diffusivities of materials measured were showed about 2% error.
Condensing Heat Transfer Characteristics of R-22 and R-134a in Small Diameter Tubes
Hong, Jin-U ; No, Geon-Sang ; Jeong, Jae-Cheon ; O, Hu-Gyu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 54~61
DOI : 10.22634/KSME-B.2001.25.1.54
Condensing heat transfer coefficients of R-22 and R-134a were measured in smooth, horizontal copper tubes with inner diameters of 1.77mm, 3.36mm, and 5.35mm, respectively. The experiments were conducted in the closed loop, which was driven by a magnetic gear pump. Data are presented for the following range of variables : mass velocity from 200 to 500kg/
.s and quality from 0 to 1.0. The heat transfer coefficients in the small diameter tubes (ID < 7mm) were observed to be strongly affected by various diameters and the heat transfer characteristics in the small diameter tubes differed from those in the large diameter tubes. Heat transfer coefficients in the small diameter tubes are higher than those in the large diameter tubes at the same experimental condition. It was found that some well-known previous correlations(Shahs correlation and Cavallini-Zecchins correlation) were not suitable for small diameter tubes.
Numerical Analysis of Three Dimensional Dynamic Stall of an Oscillating Wing
Go, Seong-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 62~70
DOI : 10.22634/KSME-B.2001.25.1.62
Three-dimensional dynamic stall over an oscillating wing has been analyzed by using a compressible Navier-Stokes code. The code solved the thin-layer Navirer-Stokes equations with a second-order time accuracy for a semispan wing with 0.3048m chord, a NACA 0015 airfoil section, and zero twist Computations were made for a freestream Mach number of 0.29, a chord Reynolds number of 1.95
10(sup)6 and a reduced frequency equal to 0.1. Numerical results were compared with experimental data which include the hysteresis of lift, drag and moment at various wing span. The comparison reveals the quantitative as well as qualitative nature of the three-dimensional dynamic stall.
Visualization of Vortical Flow Around the Free End Surface of a Finite Circular Cylinder Mounted on a Flat Plate
No, Seong-Cheol ; Park, Seung-O ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 71~77
DOI : 10.22634/KSME-B.2001.25.1.71
A flow visualization study using the oil film method and the smoke-laser light sheet arrangement is carried out to investigate the three-dimensional flow pattern around the free end surface region of a finite circular cylinder (aspect ratios of 1.25 and 4.25) mounted on a flat plate. The experiment is performed for the cases of two Reynolds numbers: 5.92
10(sup)5. Various kinds of singular points on the free-end surface are disclosed from the oil surface flow visualization. The smoke-laser light sheet visualization, to aid in understanding the oil streak-line patterns, clearly demonstrates that a pair of tornado-like vortices marched along the downstream together with a pair of side tip vortices. A topological sketch to characterize the surface flow and the four vortices emanating from the top surface is included.
Development of Gasoline Direct Swirl Injector
Park, Yong-Guk ; Lee, Chung-Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 78~86
DOI : 10.22634/KSME-B.2001.25.1.78
The Gasoline Direct Injection(GDI) system has been highlighted due to the improvement of fuel consumption and the control of exhaust emission from gasoline engines. The GDI system includes a high injection pressure, smaller mean diameter, good spray characteristics and stability. We were interested in the development for gasoline direct swirl injector(GDSI) in which the swirler is specially designed with an incident angle. Nymerical analysis was utilized to investigate the internal flow of GDSI with a goal to determine the swirl incident angle and needle lift. Accordingly, it describes characteristics of a GDSI in which the flowrate and spray characteristics are satisfied. especially the spray tip penetration decreases, compared with other type GDI, mean diameter of droplets is from 20
and spray angle ranges from 64
Numerical Simulation of Turbulent Heat Transfer in Locally-Forced Separated and Reattaching Flow
Ri, Gwang-Hun ; Seong, Hyeong-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 87~95
DOI : 10.22634/KSME-B.2001.25.1.87
A numerical study was made of heat transfer in locally-forced turbulent separated and reattaching flow over a backward-facing step. The local forcing was given to the flow by means of sinusoidally oscillating jet from a separation line. A Rhee and Sung version of the unsteady
-f(sub)u model and the diffusivity tensor heat transfer model were employed. The Reynolds number was fixed at Re(sub)H=33,000 and the forcing frequency was varied in the range 0
2. The condition of constant heat flux was imposed at the bottom wall. The predicted results were compared and validated with the experimental data of Chun and Sung and Vogel and Eaton. The enhancement of heat transfer in turbulent separated and reattaching flow by local forcing was evaluated and analyzed.
Numerical Simulation of Locally-Forced Turbulent Boundary Layer
Ri, Gwang-Hun ; Seong, Hyeong-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 96~107
DOI : 10.22634/KSME-B.2001.25.1.96
An unsteady numerical simulation was performed to analyze flow structures behind a local suction/blowing in a flat-plate turbulent boundary layer. The local forcing was given to the boundary layer flow by means of sinusoidally oscillating jet. A version of the unsteady
-f(sub)u model (Rhee and Sung 2000) was employed. The Reynolds number based on the momentum thickness was about Re(sub)
=1700. The forcing frequency was varied in the range 0.011
0.044 with a fixed forcing amplitude A(sub)o=0.4. The predicted results were compared and validated with the experimental data. It was shown that the unsteady locally-forced boundary layer flow is predicted well by the
-f(sub)u model. The effect of the pitch angle of local forcing on the reduction of skin friction was also examined.
Energy Separation of Incompressible Fluid Using Vortex Tube
Yu, Gap-Jong ; Choe, Byeong-Cheol ; Lee, Byeong-Hwa ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 108~116
DOI : 10.22634/KSME-B.2001.25.1.108
The vortex tube is a simple device which separates fluid stream into a cold stream and a hot stream without any chemical reaction. The process of energy separation in the vortex tube has caused a great deal of interest. Although many studies on energy separation in the vortex tube using air as the working fluid have been made so far, few experimental studies treated energy separation for incompressible fluid. So, an experimental study for the energy separation in the vortex tube using the water which is essentially an incompressible fluid is presented. When working fluid is the water, the best geometric values of nozzle area ratio and number of nozzle holes are 0.155, 6 respectively. These geometric values are showed by the similar values which are presented by compressible fluid as working fluid. But hot side mass fraction of which maximum temperature drop is happened are different from compressible fluid.
Optimum Design of Microchannel Heat Sinks
Jo, Yeong-Jin ; Choe, Chung-Hyeon ; Kim, Jae-Jung ; Lee, Jae-Heon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 117~123
DOI : 10.22634/KSME-B.2001.25.1.117
In present study a methodology has been developed and applied for the optimum design and performance evaluation of microchannel heat sinks. The optimum design parameters include channel number and fin thickness. For a trial model of 127mm in length, 52.5mm in width, 16mm in height and 2.5mm in base thickness, the optimum channel number and the fin thinckness have been determined to be of 194 and 0.08359mm, respectively in laminar flow region. Performance of the optimally designed microchannel heat sinks has been compared with those having 50% and 150% of the number of channels. The results showed that the 50% and 150% designs increased the pumping power by 200% and 150%, respectively.
Charge Distribution of Submicron Particles Charged by Spray Electrification or Corona Discharge
Lee, Jae-Bok ; Bae, Gwi-Nam ; Hwang, Jeong-Ho ; Lee, Gyu-Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 124~132
DOI : 10.22634/KSME-B.2001.25.1.124
This paper reports on the charge distribution measurements of submicron particles for three different charging mechanisms, which are spray electrification, bipolar ionization and corona discharge process, respectively. The number of elementary charges per particle was investigated by classifying and counting of a discrete mobility class. Charge distribution measurements were performed with NaCl particles generated from a collision atomizer for 0.01, 0.1, 1% NaCl solutions. Experimental results show than charge level of atomized NaCl particles is high and decreases with increasing the dissolved ion concentration. The charge level of the atomized NaCl particles can be reduced to that o Boltzmann equilibrium conditions by the bipolar ionization(Po(sup)210 bipolar ionizer). The charge level on NaCl particles passing through the corona discharge reactor is much higher than those of atomized or bipolar ionized NaCl particles. The evaluation of these measurements results in charge distribution of the submicron particles.
Effect of Pyrolyzing Fuel Position on Ignition and Flame Propagation in a Cylindrical Enclosure
Han, Jo-Yeong ; Kim, Jeong-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 1, 2001, Pages 133~142
DOI : 10.22634/KSME-B.2001.25.1.133
Investigation on ignition and flame propagation of pyrolyzing fuel in a cylindrical enclosure is accomplished. The pyrolyzing fuel of cylindrical shape is located in an outer cylinder sustained at high-temperature. Due to gravity, the buoyancy motion is inevitably incurred in the enclosure and this affects the flame initiation and propagation behavior. The radiative heat transfer plays an important role since a high temperature difference is involved in the problem. Therefore in all cases presented here, the intrinsic radiation effects are considered. Numerical studies have been performed over various governing parameters, such as Grashof number, overheat ratio, and vertical fuel eccentricity. Depending on the Grashof number, the flame behavior is found to be totally different: a separated visible flame appears as the Grashof number reaches 10(sup)7. The location of flame onset is also affected by the vertical eccentricity of inner pyrolyzing fuel as well as thermal conditions applied.