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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 24, Issue 12 - Dec 2000
Volume 24, Issue 11 - Nov 2000
Volume 24, Issue 10 - Oct 2000
Volume 24, Issue 9 - Sep 2000
Volume 24, Issue 8 - Aug 2000
Volume 24, Issue 7 - Jul 2000
Volume 24, Issue 6 - Jun 2000
Volume 24, Issue 5 - May 2000
Volume 24, Issue 4 - Apr 2000
Volume 24, Issue 3 - Mar 2000
Volume 24, Issue 2 - Feb 2000
Volume 24, Issue 1 - Jan 2000
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Critical Heat Flux of an Impinging Water Jet on a Heated Surface with Boiling
Lee, Jong-Su ; Kim, Heuy-Dong ; Choi, Kuk-Kwang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 485~494
DOI : 10.22634/KSME-B.2000.24.4.485
The purpose of this paper is to investigate a critical heat flux(CHF) during forced convective subcooled and saturated boiling in free water jet system impinged on a rectangular heated surface. The surface is supplied with subcooled or saturated water through a rectangular jet. Experimental parameters studied are a width of heated surface, a height of supplementary water and a degree of subcooling. Incipient boiling point is observed in the temperature of 6
of superheat of test specimen. CHF depends on jet velocity for various boiling-involved coolant system. CHF also is proportional to the nozzle exit velocity to the power of n, where n is 0.55 and 0.8 for subcooled and saturated boiling, respectively. CHF is enhanced with a higher jet velocity, higher degree of subcooling and smaller width of a heated surface.
Numerical Analysis on Heat Transfer of Viscoelastic Fluid including Buoyancy Effect
Sohn, Chang-Hyun ; Ahn, Seong-Tae ; Jang, Jae-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 495~503
DOI : 10.22634/KSME-B.2000.24.4.495
The present numerical study investigates flow characteristics and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The combined effect of temperature-dependent viscosity, buoyancy and secondary flow caused by second normal stress difference are all considered. The Reiner-Rivlin model is used as a viscoelastic fluid model to simulate the secondary flow and temperature-dependent viscosity model is adopted. Three types of thermal boundary conditions involving different combinations of heated walls and adiabatic walls are considered in this study. Calculated Nusselt numbers are in good agreement with experimental results in both the thermal developing and thermally developed regions. The heat transfer enhancement can be explained by the combined viscoelasticity-driven secondary flow, buoyancy-induced secondary flow and temperature-dependent viscosity.
Combustion Fluid Field Visualization Using PIV and Related Problems
Kim, Young-Han ; Yoon, Young-Bin ; Jeung, In-Seuk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 504~511
DOI : 10.22634/KSME-B.2000.24.4.504
PIV(Particle Image Velocimetry) is a recently developed technique for visualizing the fluid velocity fields. Because it has several advantages over the LDV(Laser Doppler Velocimetry), it became one of the most popular diagnostic tools in spite of its short history. However, its application to combustion is restricted by some problems such as flame illumination, scattered light refraction, particle density variation due to heat release, the combined effect of abrupt change in particle density and fluid velocity on flame contour, and thermophoresis which is particle lagging due to temperature gradient. These problems are expected to be originated from the non-continuous characteristics of flames and the limitations of particle dynamics. In the present study, these problems were considered for the visualization of the instantaneous coaxial hydrogen diffusion flame. And the instantaneous flame contour was detected using particle density difference. The visualized diffusion flame velocity field shows its turbulent and meandering nature. It was also observed that the flame is located inside the outer shear layer and flame geometry is largely influenced by the vorticity.
Modeling of Liquid Fuel Behavior to Control Air/Fuel Ratio in the Intake Port of SI Engines
Cho, Hoon ; Min, Kyoung-Doug ; Hwang, Seung-Hwan ; Lee, Jong-Hwa ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 512~518
DOI : 10.22634/KSME-B.2000.24.4.512
A wall fuel-film flow model is developed to predict the effect of a wall-fuel-film on air-fuel ratio in an SI engine in transient conditions. Fuel redistribution in the intake port resulting from charge backflow and a simple liquid fuel behavior in the cylinder are included in this model. Liquid fuel film flow is calculated of every crank angle degree using the instantaneous air flow rate. The model is validated by comparing the calculated results and corresponding engine experiment results of a commercial 4 cylinder DOHC engine. The predicted results match well with the experimental results. To maintain the constant air-fuel ratio during transient operation. the fuel injection rate control can be obtained from the simulation result.
The Effect of Nozzle Diameter on Heat Transfer to a Fully Developed Round Impinging Jet
Lee, Dae-Hee ; Won, Se-Youl ; Lee, Young-Min ; Cho, Heon-No ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 519~525
DOI : 10.22634/KSME-B.2000.24.4.519
The effect of nozzle diameter on the local Nusselt number distributions has been investigated for an axisymmetric turbulent jet impinging on the flat plate surface. The flow at the nozzle exit has a fully developed velocity profile. A uniform heat flux boundary condition at the plate surface was created using gold film Intrex. Liquid Crystal was used to measure the plate surface temperature. The experiments were made for the jet Reynolds number (Re) 23,000, the dimensionless nozzle to surface distance (L/d) from 2 to 14, and the nozzle diameter (d) from 1.36 to 3.40 cm. The results show that the Nusselt number at and near the stagnation point increase with an increasing value of the nozzle diameter.
A Study of Fly Ash Resistivity Characteristics Generated from the Coal Fired Power Plant as a Function of Water Concentration and Temperature
Ku, Jae-Hyun ; Lee, Jung-Eun ; Lee, Jae-Keun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 526~532
DOI : 10.22634/KSME-B.2000.24.4.526
Recent studies have been directed toward obtaining a better understanding of the application of electrostatic precipitators to collect fly ash particles produced in a coal-fired power plant. Electrical resistivity can be described as the resistance of the collected dust layer to the flow of electrical current and is an important property for the collection efficiency in the electrostatic precipitator. In this paper, fly ash resistivity as a function of temperature up to
has been experimentally investigated using the resistivity meter consisted of the movable electrode, dust cup, and furnace. Resistivity was found to increase with increased temperature up to
due to the reduction of water concentration and then gradually decrease with increased temperature due to the activation of electrons. As the resistivity of fly ash in the flue gas temperature of
was measured >
ohm cm, the efficiency of fly ash removal in the electrostatic precipitator might be expected to be low due to back-corona phenomenon. Flue gas conditioning in the electrostatic precipitator to reduce the resistivity of fly ash as required.
Application of Temperature Inversion by Using Spectral Radiation Intensities
Yang, Soo-Seok ; Song, Tae-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 533~542
DOI : 10.22634/KSME-B.2000.24.4.533
Analytical experiments to determine the line-of-sight temperature distribution is conducted by using spectral radiation intensities. For this study, fourteen narrow bands of
) are selected. The applied system is a one-dimensional gas slab filled with 100%
gas at 1 atm. Two types of temperature profile are tested; parabolic and boundary layer types. Three kinds of radiation calculation are used in the iteration procedure for the temperature inversion; LBL(Line by Line), SNB(Statistical Narrow Band) and WNB(WSGGM. based Narrow Band) models. The LBL solution shows perfect agreement while some error of temperature prediction is caused by radiation modeling error when using SNB and WNB models. The inversion result shows that the WNB model may be used more accurately in spectral remote sensing techniques than the traditional SNB model.
A Study on Fuzzy Control Simulator of Naturally Circulated Boiler
Kim, Kwang-Sun ; Kim, Sam-Un ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 543~554
DOI : 10.22634/KSME-B.2000.24.4.543
The engineering equations, which have been used in many engineering companies, were employed for the dynamic modelling part in order to develop the naturally circulated boiler simulator. The fuzzy algorithm, which is similar to the algorithm of making decision by the human being, was developed for the boiler simulator controller and its simulated variables were compared with those of classical PID simulations to verify the stability and the effectiveness of fuzzy controller. The simulator is for the naturally circulated boiler and the main components are the furnace, the drum, the super heater, and the economizer. The combustion and thermal radiation dominant equations were used within the furnace and the mass conservation and the energy rate balance equations were employed for the drum part. The heat transfer rates were calculated using the logarithmic mean temperature differences both for the super heater and for the economizer. The simulations are very useful to understand the boiler operations and the engineering design of the main components. The main program was developed under the PC window condition by linking the fuzzy controller to the main boiler program using the Visual C++ language. The various operational conditions such as the abrupt changes of load, the changes of water supply pipes and the diameter of drum were simulated.
Effect of Injection Pressure on Atomization Characteristics of Fuel Spray in High-Pressure Gasoline Injector
Lee, Chang-Sik ; Choi, Soo-Chon ; Kim, Min-Kyu ; Kwon, Sang-Il ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 555~560
DOI : 10.22634/KSME-B.2000.24.4.555
This paper describes the macroscopic behavior and atomization characteristics of the high-pressure gasoline injector in direct-injection gasoline engine. The global spray behavior of fuel injector was visualized by shadowgraph technique. The atomization characteristics of gasoline spray such as mean diameter and mean velocity of droplet were measured by the phase Doppler particle analyzer system. In order to obtain the influence of fuel injection pressure, the macroscopic visualization and experiment of particle measurement on the fuel spray were investigated at 3,5 and 7 MPa of injection pressure under different surrounding pressure in the spray chamber. The results of this work show that the fuel injection pressure of gasoline injector in GDl engine has influence upon the mean droplet diameter, mean velocity of spray droplet, the spray tip penetration, and spray width under the elevated ambient pressure.
Characteristic Experiment of Swashplate Type Axial Piston Motor (I)
Yum, Man-Oh ; Yoon, Il-Ro ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 561~569
DOI : 10.22634/KSME-B.2000.24.4.561
The purpose of this study is to construct a testing equipment with which several characteristics of the domestically developed swashplate type axial piston motor can be tested and to develop a software with which the data from experiment can be stored and can be applied. The results of the study are as follows; 1) The leakage flow and the torque of the motor being stopped is propotional to supply pressure and their relation can be showed by linear equations. 2) The motor movement is not smooth below 50 rpm but it moves smoothly up 170 rpm. 3) When the motor starts or stops, the pressure rise ratio effects decisively to the max. torque.
Effects of Gap Spacing on Heat Transfer Characteristics for Co-Rotating Disks
Ryu, Goo-Young ; Won, Chung-Ho ; Cho, Hyung-Hee ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 570~577
DOI : 10.22634/KSME-B.2000.24.4.570
Local heat transfer characteristics inside a hard disk driver(HDD) are investigated in this study. The investigation is considered between disks co-rotating in a cylindrical enclosure. The gap spacing, rotating speed and head-arm positions are mainly considered to understand the flow and heat transfer in the co-rotating disks. The naphthalene sublimation technique is used to determine local heat/mass transfer coefficients on the rotating disk. Flow patterns inside the co-rotating disks are investigated using a Laser Doppler Anemometer (LDA) and also analyzed numerically. The results show that the heat transfer coefficients on the disk changed little with the gap spacing between disks. Heat transfer rates in the outer region increases with increasing rotating Renolds number, but the values normalized by that on a free rotating disk give a similar pattern for the tested cases. The head-arm inserted between the rotating disks destroys the inner region resulting in enhancement of heat transfer in that region.
Numerical Simulation of Rotating Channel Flows Using a Second Moment Turbulence Closure
Shin, Jong-Keun ; Choi, Young-Don ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 578~588
DOI : 10.22634/KSME-B.2000.24.4.578
A low-Reynolds-number second moment turbulence closure is improved with the aid of DNS data. For the model coefficients of pressure-strain terms, we adopted Shima's model with some modification. Shin and Choi's new dissipation-rate equation is employed to simulate accurately the turbulence energy dissipation rate distribution in the near wall sublayer. The results of computations are compared with DNS, LES data and experimental data for turbulent plane channel flow with rotation about spanwise axis. The present second moment closure achieves a level of agreement similar to that for the non-rotating. In particular, it accurately captures the distribution of turbulence energy dissipation rate in the near wall region.
An Experimental Approach to Evaluate the Desulfurization Yield in Spray Drying Sorber
Yang, Hyun-Mo ; Kim, Sang-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 589~598
DOI : 10.22634/KSME-B.2000.24.4.589
A pilot-scale Spray Drying Sorber (SDS) system was set up to evaluate the effect of spray characteristics on the desulfurization yield. The size distribution and the Sauter Mean Diameters of slurry droplets were measured in advance using the optical size measurement system, Malvern 2600. The desulfurization yield of the drying chamber by size was measured for the conditions of inlet gas and spray injection. As a reagent, 10% limestone slurry of
was treated with flue gas containing
, and the combustion gas analyzer and gas detectors were attached to measure the
concentration. With a flow rate of 144 Nm3/h and a temperature range of
, the experiments were performed for the Stoichiometric Ratio (SR) of 1.0 to 3.0 and droplet mean diameter of 6.5 to
. In case of smaller spray droplets, the desulfurization efficiency improved due to the increase of total droplet surface area, while the reduction in evaporation time reduced the contact time between the droplets and
gas. In some typical region of droplet diameter, this negative effect, reduction of contact time, became dominant and the desulfurization yield decreases the desulfurization yield in spite of the expansion in absorption area. These results revealed that there exists the optimal size of spray droplets for a given state, which is determined by the compromise between the total surface area of slurry droplets and the evaporation time of droplets. The measurements also indicated that the inlet temperature of flue gas changes the optimal injection condition by varying the driving force for evaporation. The results confirm that the effect of the evaporation time of slurry droplets should be considered in analyzing the desulfurization yield as well as the total surface area, for it is a significant aspect of the correlation with the capabilities of
absorption in wet droplets. In conclusion, the optimal condition of spray can be determined based on these results, which might be applied to design or scale-up of SDS system.
Determination of Background Gray-level for Accurate Measurement of Particles in using Image Processing Method
Koh, Kwang-Uoong ; Lee, Sang-Yong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 599~607
DOI : 10.22634/KSME-B.2000.24.4.599
In this study, experiments have been performed to examine the effects of background gray-level on the depth-of-field and on the in-focus criteria. The normalized value of contrast(VC) and the gradient indicator(GI) were used as the in-focus criteria for the small and the large size-ranges of particles, respectively. The slightly larger number of pixels were detected with the brighter background. The maximum of the normalized value of contrast(VCmax) is decreased with the brighter background and its deviation from that with the background gray-level of 160 turned out to be about
15% when the background gray-level changes from 100 to 200. However, the maximum gradient indicator(GImax) changes with the background gray-level within only
5%. The depth-of-field for the VC-applicable particle-size range is largely dependent on the background gray-level. On the other hand, the depth-of-field for the GI-applicable particle-size range changes only slightly with the background gray-level. To keep the normalized standard deviation of the particle size within 0.1, the background gray-level should be set 160
20 for both the VC-applicable and GI-applicable ranges which cover the particle size between
An Aerosol CVD Method Using Internal Jet for Optical Fiber Synthesis
Hong, Choon-Keun ; Choi, Man-Soo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 4, 2000, Pages 608~613
DOI : 10.22634/KSME-B.2000.24.4.608
The present study has proposed a novel aerosol CVD utilizing an internal jet in the conventional MCVD reactor for the purpose of enhancing the deposition efficiency(and rate) and the uniformity of deposited film. The use of impingement of high temperature jet through a thin inner tube ensures the reduction of non-uniform particle deposition zone as well as higher thermophoretic particle deposition. It is shown that significant improvements have been achieved for both aspects of deposition efficiency and uniformity. As jet temperatures increase, the tapered length is reduced and deposition efficiency is significantly increased.