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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
Experimental Study for Development of Air Eject Defrost Equipment
Han, In-Geun ; Kim, Chang-Yeong ; Kim, Jae-Dol ; Yun, Jeong-In ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 277~284
DOI : 10.22634/KSME-B.2001.25.3.277
One of the problems in a refrigerator operation is the frost formation on a cold surface of the evaporator. The frost layer is formed by the sublimation of water vapor when the surface temperature is below the freezing point. This frost layer is usually porous and formed on the cold surface of the evaporator. The frost layer on the surface of a evaporator will make side effect such as thermal resistance. However, these important factors have not been used in determining the defrosting period. Therefore, the proper defrosting operation period based on the new defrosting method is very important, and make a comparison between conventional method like electric defrost and new method in compression work, evaporation pressure, evaporation temperature.
Analysis of the Coupled Turbulent Flow and Macroscopic Solidification in Twin-Roll Continuous Casting Process
Kim, Deok-Su ; Kim, U-Seung ; Jo, Gi-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 285~295
DOI : 10.22634/KSME-B.2001.25.3.285
The transport phenomena in a wedge-shaped pool of twin-roll continuous caster are affected by the various operating parameters such as the melt-feed pattern, roll-gap thickness, melt-superheat, and casting speed. A computer program has been developed for analyzing the two-dimensional, steady conservation equations for transport phenomena during twin-roll continuous casting process in order to estimate the turbulent melt-flow, temperature fields, and solidification in the wedge-shaped pool. The turbulent characteristics of the melt-flow were considered using a low-Reynolds-number K-
turbulence model. Based on the computer program, the effects of the different melt-feed patterns, roll-gap thicknesses, and superheats of melt on the variations of the velocity and temperature distributions, and the mushy solidification were examined. The results show that the liquidus line is located considerably at the upstream region, and in the lower region appear the well-mixed melt-flow and most widely developed mushy zone. Besides, the variation of melt-flow due to varying melt-feed patterns, affects mainly the liquidus line, and scarcely has effects on the solidus line in the outlet region.
Measurement of Thermal Diffusivity Using Minimum Phase Based on the Photothermal Displacement
Lee, Eun-Ho ; Lee, Gwang-Jae ; Jeon, Pil-Su ; Yu, Jae-Seok ; Kim, Gi-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 296~304
DOI : 10.22634/KSME-B.2001.25.3.296
A new method of measuring the thermal diffusivity of solid material at room temperature using photothermal displacement is proposed. The influence of the parameters, such as radius and modulation frequency of the pump beam and the sample thickness, was studied. From the minimum position of phase of measured deflection with respect to the pump beam, the thermal diffusivity of the materials can be obtained. The position where phase has the minimum value is determined using multiparameter least-square regression fitting. The experimental values for different samples obtained by applying the new method are in good agreement with the literature values.
A New k-
Model for Prediction of Transitional Boundary-Layer Under Zero-Pressure Gradient
Baek, Seong-Gu ; Im, Hyo-Jae ; Jeong, Myeong-Gyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 305~314
DOI : 10.22634/KSME-B.2001.25.3.305
A modified model is proposed for calculation of transitional boundary layer flows. In order to develop the eddy viscosity model for the problem, the flow is divided into three regions; namely, pre-transition region, transition region and fully turbulent region. The pre-transition eddy-viscosity is formulated by extending the mixing length concept. In the transition region, the eddy-viscosity model employs two length scales, i.e., pre-transition length scale and turbulent length scale pertaining to the regions upstream and the downstream, respectively, and a universal model of stream-wise intermittency variation is used as a function bridging the pre-transition region and the fully turbulent region. The proposed model is applied to calculate three benchmark cases of the transitional boundary layer flows with different free-stream turbulent intensity (1%∼6%) under zero-pressure gradient. It was found that the profiles of mean velocity and turbulent intensity, local maximum of velocity fluctuations, their locations as well as the stream-wise variation of integral properties such as skin friction, shape factor and maximum velocity fluctuations are very satisfactorily predicted throughout the flow regions.
Model for the Inertial Focusing of Particles Using an Atmospheric Aerodynamic Lens
Lee, Jin-Won ; Lee, Min-Yeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 315~321
DOI : 10.22634/KSME-B.2001.25.3.315
Aerodynamic lenses are widely used in generating particle beams of high density and small diameter, but analytical or modeling studies are limited only in the free molecular regime. In this study, it is shown that generating particle beam is also possible in atmospheric pressure range, and the mechanism of generating particle beam using an orifice is analysed into three different parts : fluid dynamic contraction, diffusional defocusing, and inertial focusing. In laminar flow conditions, the diffusional defocusing effect can be neglected, and the effects of inertial focusing can be expressed in terms of the orifice size and Stokes number. Numerical experiments are done for two different orifices, d/D=1/5 and 1/10 and particle diameter d(sub)p=1-10 ㎛. The results for two different orifices can be made into a single curve when a modified Stokes number is used. The inertial focusing effect diminishes when the modified Stokes number becomes smaller than 10(sup)-2.
A Numerical Study on Shock Wave Turbulent Boundary Layer Interactions in High-Speed Flows
Mun, Su-Yeon ; Son, Chang-Hyeon ; Lee, Chung-Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 322~329
DOI : 10.22634/KSME-B.2001.25.3.322
A study of the shock wave turbulent boundary layer interaction is presented. The focus of the study is the interactions of the shock waves with the turbulent boundary layer on the falt plate. Three examples are investigated. The computations are performed, using mixed explicit-implicit generalized Galerkin finite element method. The linear equations at each time step are solved by a preconditioned GMRES algorithm. Numerical results indicate that the implicit scheme converges to the asymptotic steady state much faster than the explicit counterpart. The computed surface pressures and skin friction coefficients display good agreement with experimental data. The flowfield manifests a complex shock wave system and a pair of counter-rotating vortices.
Experimental Study on the Effects of Upstream Wakes on Cascade Flow
Kim, Hyeong-Ju ; Jo, Gang-Rae ; Ju, Won-Gu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 330~338
DOI : 10.22634/KSME-B.2001.25.3.330
This paper is concerned with the effect of cylinder wakes upstream on blade characteristics of compressor cascade(NCA 65 series). At first, it is found that the velocity defect ratio of cylinder wake varies according to the acceleration and deceleration in a flow field but, is conserved nearly constant at flow downstream the cascade, irrespective of the flow path in the cascade. When a cylinder wake flows along near the suction surface of the blade, or impinges on the leading edge, the turbulent velocities are supplied on or inside the outer edge of boundary layer near the leading edge of suction surface, and the transition to a transitional or turbulent boundary layers is induced, so that the laminar separation is prevented, but the profile loss increases. The transition of boundary layer to a transitional or turbulent one is strongly related with the strength of added turbulent velocities near the leading edge on the suction surface, which is influenced by the flow path of a cylinder wake.
The Study for an Impulsive Spin-Up Flow in a Shallow Rectangular Container
Im, Gwang-Ok ; Gwon, Tae-Jong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 339~346
DOI : 10.22634/KSME-B.2001.25.3.339
The impulsive spin-up flow in a shallow rectangular container is analyzed numerically by quasi 3-D unsteady laminar flow. In the non-inertia coordinates, the flow is generated by the virtual forces as Coriolis force, etc.. After the boundary layers grow up near sidewalls, primary vortexes separate from the sidewalls. As the Reynolds number increases, the subsidiary vortexes take place in the boundary layer. The rigid body rotation is started from the inner region and propagated to the outer region, finally all the fluid reaches the rigid body rotation. According to the Reynolds number and the aspect ratio, the development of vortex pattern is symmetric or asymmetric.
Heat Transfer Analysis in a PDP Ventilation Chamber
Park, Hyeong-Gyu ; Jeong, Jae-Dong ; Kim, Chan-Jung ; Lee, Jun-Sik ; Park, Hui-Jae ; Jo, Yeong-Man ; Jo, Hae-Gyun ; Park, Deuk-Il ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 347~355
DOI : 10.22634/KSME-B.2001.25.3.347
A heat transfer analysis in a ventilation chamber of Plasma Display Panel(PDP) has been conducted. The process requirement is to precisely follow prescribed temperature trajectory while maintaining temperature uniformity for each panel. Firstly, experiment in a test chamber has been carried out and the results are compared with the unsteady 3D numerical data. Reasonable agreement was found, which suggested that the employed numerical model had its credibility in actual PDP ventilation processes. On this ground, a tact-type heating/cooling system was analyzed. The panel temperature in the 40
tact-type system was more uniform than that in the 80
one. For improving the uniformity of panel temperature, relocation of ventilation head to the rear part and inlet flow control are required. Comparison of full simulation of a cart and simplified simulation of one panel indicates the optimized panel pitch can also be predicted.
Measurements of Endwall Heat(Mass) Transfer Coefficient in a Linear Turbine Cascade Using Naphthalene Sublimation Technique
Lee, Sang-U ; Jeon, Sang-Bae ; Park, Byeong-Gyu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 356~365
DOI : 10.22634/KSME-B.2001.25.3.356
Heat (mass) transfer characteristics have been investigated on the endwall of a large-scale linear turbine cascade. Its profile is based on the mid-span of the first-stage rotor blade in a industrial gas turbine. By using the naphthalene sublimation technique, local heat (mass) transfer coefficients are measured for two different free-stream turbulence intensities of 1.3% and 4.7%. The results show that local heat (mass) transfer Stanton number is widely varied on the endwall, and its distribution depends strongly on the three-dimensional vortical flows such as horseshoe vortices, passage vortex, and corner vortices. From this experiment, severe heat loads are found on the endwall near the blade suction side as well as near the leading and trailing edges of the blade. In addition, the effect of the free-stream turbulence on the heat (mass) transfer is also discussed in detail.
An Experimental Study for the Liquid Freezing Phenomena in a Pipe During Ice Plugging
Park, Yeong-Don ; Jo, Hyeon-Cheol ; Choe, Byeong-Ik ; Kim, Gwi-Sun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 366~372
DOI : 10.22634/KSME-B.2001.25.3.366
The ice plugging process consists of placing liquid nitrogen around a pipe and removing heat until the water in the pipe freezes and provides a solid plug or seal against fluid movement. This technique enables us to repair or inspect a pipe system without shutdown of entire system. A set of test apparatus for investigation of the liquid freezing phenomena during ice plugging is prepared. This study shows the characteristics of the liquid freezing and the heat transfer with various pipe and freezing jacket conditions. And in case there is flow of the fluid inside the pipe, the flow rate which can be able to form the ice plug is identified with the effect of the pipe diameter and freezing jacket length on the plug formation. The permissible maximum flow rate for the complete plug formation is approximately proportional to the freezing jacket length at the same pipe diameter condition.
Numerical Simulation of a Taylor Bubble Rising in a Vertical Tube
Son, Gi-Heon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 373~380
DOI : 10.22634/KSME-B.2001.25.3.373
In this study, a single Taylor bubble and a train of Taylor bubbles rising in a vertical tube were simulated numerically. A finite difference method was used to solve the mass and momentum equations for the liquid-gas region. The liquid-gas interface was captured by a level set function which is defined a signed distance from the interface. For a train of Taylor bubbles repeated periodically in space, the periodic conditions were imposed at the boundaries normal to the gravitational direction and the pressure boundary conditions were iteratively determined so that the computed flow rate should be equal to a given flow rate. Based on the numerical simulation, the calculated shape and rise velocity of a Taylor bubble were found to be in good agreement with the experimental data reported in the literature.
Heat Transfer Characteristics of the Interaction Between Bulk Flow Pulsation and a Vortex Embedded in a Turbulent Boundary Layer
Gang, Sae-Byeol ; Maeng, Du-Jin ; Lee, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 381~388
DOI : 10.22634/KSME-B.2001.25.3.381
Presented are heat data which describe the effect of interaction between bulk flow pulsations and a vortex embedded in a turbulent boundary layer. The pulsation frequencies are 3 Hz, 15 Hz and 30 Hz. A half delta wing with the same height as the boundary layer thickness is used to generate the vortex flow. The convection heat transfer coefficients on a constant heat-flux surface are measured by embedded 77 T-type thermocouples. Spanwise profiles of convection heat transfer coefficients show that upwash region of vortex flow is influenced by bulk flow pulsations. The local heat transfer coefficient increases approximately by 7 percent. The increase in the local change of convection heat transfer coefficient is attributed to the spanwise oscillatory motion of vortex flow especially at the low Strouhal number and to the periodic change of vortex size.
Numerical Simulation of Bubble Motion During Nucleate Boiling
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 389~396
DOI : 10.22634/KSME-B.2001.25.3.389
Direct numerical simulation of bubble growth and merger process on a single nucleation site during partial nucleate boiling is performed. The equations governing conservation of mass, momentum and energy are solved using a finite difference method combined with a level set method for capturing the vapor-liquid interface. The level set method is modified to include the effects of phase change at the interface and contact angle at the wall. Also, a simplified formulation for predicting the evaporative heat flux in a thin liquid micro-layer is developed and incorporated into the level set formulation. Based on the numerical results, the bubble growth and merger pattern and its effect on the heat transfer are discussed.
Numerical Simulations of Unsteady Wakes Using a Discrete Vortex Method
Han, Cheol-Hui ; Choe, Geun-Hyeong ; Jo, Jin-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 397~404
DOI : 10.22634/KSME-B.2001.25.3.397
The behavior of unsteady wake vortices for the two-dimensional flat plate is simulated by a discrete vortex method. The flat plates and their wakes are represented by vortex sheets. The vortex sheets are replaced with discrete vortices. The freely deforming wake sheets are computed as a part of solution and the ground effect is included by a image method. In order to predict wake shapes accurately and to model closely coupled aerodynamic interference, a vortex core model and a vortex core addition scheme are used. The simulated wake shapes convecting behind the plates in unsteady motion are compared to a flow visualization result and other numerical results. The present results agree well with them. The present method is also applied to the aerodynamic analysis of flat plates in tandem configuration in ground effect.
Heat/Mass Transfer Characteristics in A Rotating Duct with
Won, Chung-Ho ; Lee, Sei-Young ; Cho, Hyung-Hee ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 405~413
DOI : 10.22634/KSME-B.2001.25.3.405
The present study investigates convective heat/mass transfer and flow characteristics inside a rotating two-pass rectangular duct. A naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy. The objective of this study is to determine the effects of turning geometry with rotation for 0.0
0.24. The results reveal that the sharp-turn corner has the larger pressure drop and lower heat transfer in the post-turn region than those of the round-turn corner. The strong secondary flow enhances heat transfer for the round-turn corner. Coriolis force induced by the rotation pushes the high momentum core flow toward the trailing wall in the first passage with radially outward flow and toward the leading wall in the second passage with radially inward flow. Consequently, the high heat transfer rates are generated on the trailing surface and the leading surface in the first and second passage, respectively. However, the strong secondary flow due to the turning dominates the flow pattern in the second passage, thus the heat transfer differences between the leading and trailing surfaces are small with the rotation.
Heat/Mass Transfer Characteristics on Shroud with Turbine Blade Tip Clearances
Lee, Dong-Ho ; Choe, Jong-Hyeon ; Jo, Hyeong-Hui ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 414~421
DOI : 10.22634/KSME-B.2001.25.3.414
The present study is conducted to investigate the local heat/mass transfer characteristics on the shroud with blade tip clearances. The relative motion between blade and shroud has little influence on the overall heat transfer characteristics, except some local effects. Therefore, the relative motion between the blade and shroud is neglected in this study. A naphthalene sublimation method is employed to determine the detailed local heat/mass transfer coefficients on the surface of the shroud. The tip clearance is changed from 0.66% to 2.85% of the blade chord length. The flow enters the gap between the blade tip and shroud at the pressure side due to the pressure difference. Therefore, the heat/mass transfer characteristics on the shroud are changed significantly from those with endwall. At first, high heat/mass transfer occurs along the profile of blade at the pressure side due to the entrance effect and acceleration of the gap flow. Then, the heat/mass transfer coefficients on the shroud increase along the suction side of the blade because tip leakage vortices are generated and interact with the main flow. The results show that the heat/mass transfer characteristics are changed largely with the gap distance between the tip of turbine blade and the shroud.
Transient Heat Transfer in Porous Media under Oscillating Flow Condition
Byeon, Su-Yeong ; Lee, Dae-Yeong ; No, Seung-Tak ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 422~432
DOI : 10.22634/KSME-B.2001.25.3.422
An analytical characterization is presented on the transient heat transfer by an oscillating flow through a porous slab. Based on a two-equation model, analytic solutions are obtained for both the fluid and solid temperature variations. Two parameters are identified as the Stanton number for the internal heat exchange and the ratio of the thermal capacities between the solid and fluid phases. The heat transfer characteristics are shown to be classified into four regimes according to the two parameters and physical interpretation is presented on the particular heat transfer processes within each regime. In addition, the condition for the local thermal equilibrium between the phases is examined and the relevant criterion is suggested.
Chaotic Thermal Convection of a Intermediate Prandtl-Number Fluid in a Horizontal Annulus: Pr=0.2
Yu, Ju-Sik ; Kim, Yong-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 433~441
DOI : 10.22634/KSME-B.2001.25.3.433
Natural convection of a fluid with intermediate Prand시 number of Pr=0.2 in a horizontal annulus is considered, and the bifurcation phenomena and chaotic flows are numerically investigated. The unsteady two-dimensional streamfunction-vorticity equation is solved with finite difference method. The steady downward flow with two counter-rotating eddies bifurcates to a simple periodic flow with a fundamental frequency. And afterwards, second Hopf bifurcation occurs, and a quasi-periodic flow with two incommensurable frequencies appears. However, a new time-periodic flow is established after experiencing quasi-periodic states. As Rayleigh number is increased further, the chaotic flow regime is reached after a sequence of successive Hopf bifurcation to quasi-periodic and chaotic flow regimes. A scenario similar to the Ruelle-Takens-Newhouse scenario of the onset of chaos is observed.
Experimental Study on Electrical Agglomeration of Liquid Particles in an Alternating Electric Field
Ji, Jun-Ho ; Hwang, Jung-Ho ; Bae, Gwi-Nam ; Kim, Yong-Gin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 3, 2001, Pages 442~450
DOI : 10.22634/KSME-B.2001.25.3.442
Experiments were carried out on agglomeration of bipolarly charged particles in an alternating current electric field. Laboratory-scale setup was built and experiments were conducted at atmospheric condition. DOS(Di-octyl Sebacate) particles with 100% purity were generated by an atomizer. The particles were branched into two, each of which passed through a wire-to-plate type charging section where a positive or a negative DC high voltage was applied and was charged positively or negatively. These bipolarly charged particles together passed through an agglomeration section where an
20kV AC power was applied between two plates. The resident time in the agglomeration section was adjusted as l sec. Particle sampling was made by a cascade impactor (MOUDI). The effect of agglomeration system on the reduction ratio of particles below l ㎛ was 42∼45%. Effect of AC frequency on the particle size distribution was found insignificant.