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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 22, Issue 7 - Jul 1998
Volume 22, Issue 6 - Jun 1998
Volume 22, Issue 5 - May 1998
Volume 22, Issue 4 - Mar 1998
Volume 22, Issue 3 - Mar 1998
Volume 22, Issue 2 - Feb 1998
Volume 22, Issue 1 - Jan 1998
Volume 22, Issue 10 - 00 1998
Selecting the target year
An experimental study of hot filament chemical vapor deposition for diamond films
Kim, Yeong-Jae ; Han, Dong-Cheol ; Choe, Man-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 563~572
DOI : 10.22634/KSME-B.1918.104.22.1683
An experimental study of hot filament chemical vapor deposition(HFCVD) has been carried out for the fabrication of diamond thin film. Of particular interest is the measurement of deposition uniformity on large substrates. Experimental apparatus including a vacuum chamber, heating elements, etc. has been designed and manufactured. Deposition profiles for different pretreatment powders and different flow rates have been measured in conjunction with the measurement of substrate temperature distribution on a large substrate surface. As the flow rate increases, deposition rate increases, however, the crystallinity becomes worse. Higher growth rate has been found on the region closer to the center location where substrate temperature is higher. The crystallinity has been improved as gas flow rate decreases. The growth rate and morphology of deposition were identified by SEM and the existence of diamond phase was proved by Raman spectroscopy.
A numerical study of vortex shedding and lock-on behind a square cylinder in a laminar flow
Jeong, Yeong-Jong ; Jo, Sang-Hyeon ; Choe, Hae-Cheon ; Gang, Sin-Hyeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 573~583
DOI : 10.22634/KSME-B.1922.214.171.1243
Effects of the oscillating incoming flow on vortex shedding and lock-on behind a square cylinder are investigated using numerical simulations at a Reynolds number of 100. Vortex shedding occurred at low forcing frequencies of the incoming flow similar to the natural vortex shedding. As the forcing frequency further increases, the shedding frequency decreases to the half of the forcing freqnency. For a sufficiently large frequency, vortex shedding returns to the natural vortex shedding irrespective of the forcing amplitude. Also, the lock-on region becomes wider with higher forcing amplitudes. The phase diagram between the drag and lift shows a simple periodic behavior in the lock-on region, while a complicated periodic phase relation is observed when there is no lock-on.
Thermal conductivity measurements of non-Newtonian fluids in a shear field
Lee, Dong-Ryeol ; Irvine, Thomas F. ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 584~595
DOI : 10.22634/KSME-B.19126.96.36.1994
An investigation was carried out to determine experimentally the thermal conductivities of non-Newtonian fluids in a shear field. Both time independent purely viscous and viscoelastic fluids were considered. A coaxial cylinder apparatus with a rotating outer cylinder was used to establish the velocity field in the test fluid. First, the thermal conductivity of distilled water measured to validate the instrument. The experimental water data agreed within 1% of literature values and there was no effect of outer cylinder rotation (shear field). However, for non-Newtonian fluids such as aqueous CMC and Separan solutions, there were significant increases in thermal conductivities of up to 70% for CMC and 50% for Separan depending on the shear rate, polymer concentration and temperature. Considering the shear rate dependent thermal conductivity in the study of heat transfer in non-Newtonian fluids could be important. As in natural convection, the momentum and energy equations could no longer be solved separately but would have to be solved simultaneously.
Measured data of thermophysical properties of concrete for a temperature range of
Sin, Gi-Yeol ; Jeong, Mo ; Kim, Jong-Cheol ; Kim, Sang-Baek ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 596~606
DOI : 10.22634/KSME-B.19188.8.131.526
Thermophysical properties and the compressive strength of concrete used in nuclear power plants in Korea were measured. The chemical composition of the concrete was also analyzed. The measured thermophysical properties include the density, the thermal conductivity, the thermal diffusivity and the specific heat for a wide temperature range of 20.deg. C to 1100.deg. C. The chemical composition of Korean concrete is similar to that of US basaltic concrete and the thermophysical properties are strongly temperature dependent. The density, the conductivity and the diffusivity decrease with an increase in temperature, and particularly the conductivity and the diffusivity are a 50-perdent decrease at 900.deg. C as compared with these values at room temperature. The specific heat increases until 500.deg. C, decreases from 700.deg. C to 900 .deg. C, and then increases again when temperature is above 900.deg. C. The measurement beyond 1100.deg. C is not acceptably accurate because the concrete decomposes to a liquid phase from a solid phase at that temperature. The results of this study can be applied, for example, to an analysis of the molten core-concrete interaction (MCCI) phenomenon of concrete structures at high temperature will also require those property data, especially for high temperature ranges.
Joint probability density function of droplet sizes and velocities in a transient diesel spray
Kim, Jong-Hyeon ; Gu, Ja-Ye ; O, Du-Suk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 607~617
DOI : 10.22634/KSME-B.19184.108.40.2067
Comparisons of joint probability density distribution obtained from the raw data of measured droplet sizes and velocities in a transient diesel fuel spray with computed joint probability density function were made. Simultaneous droplet sizes and velocities were obtained using PDPA. Mathematical probability density functions which can fit the experimental distributions were extracted using the principle of maximum likelihood. Through the statistical process of functions, mean droplet diameters, non-dimensional mass, momentum and kinetic energy were estimated and compared with the experimental ones. A joint log-hyperbolic density function presents quite well the experimental joint density distribution which were extracted from experimental data.
Fundamental stuyd on reflection phenomenon of weak pressure-wave from an open end of a pipe
Kim, Hui-Dong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 618~626
DOI : 10.22634/KSME-B.19220.127.116.118
This paper describes a series of fundamental studies on reflection and emission of weak pressure waves from an open end of a pipe. Acoustical theories which have been employed in the plane pressure waves inside a pipe are applied to the present study. The objective of the present study is to investigate the reflection or emission coefficient of pressure wave at an open end of a pipe, the length of open end correction, and the directivity characteristics of the pressure waves emitted from the pipe. The results show that the reflection coefficient of pressure wave at an open end and the length of open end correction decrease for the wave length of pressure wave to increase. It is also found that the reflection coefficient for a baffle plate at the exit of pipe is larger than that for no baffle plate.
The study on the combustion model and combustion characteristics for stoker type incinerator
Kim, Ho-Yeong ; Hwang, Ho-Yeong ; Jeon, Cheol-Gyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 627~639
DOI : 10.22634/KSME-B.1918.104.22.1687
A combustion model for the incineration of municipal solid waste(MSW) in the stoker type incinerator was developed by considering the variation of physical composition of MSW. Theoretical analysis and numerical simulation for the combustion characteristics in incinerator were conducted by using the present model and the effects of compositional variation on the incineration characteristics of MSW was examined theoretically. It is found that large excess air enhances drying, but depresses volatilization. For the large value of moisture content, pyrolysis is fast but drying is slow. As the value of plastic content increases, devolatilization becomes slower. Larger amount of primary air supply to the rear side of stoker leads to increase the possibility of delaying the combustion.
A numerical study on the molecular transition flow for the rotating blades
Heo, Jung-Sik ; Hwang, Yeong-Gyu ; Kim, Dong-Gwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 640~650
DOI : 10.22634/KSME-B.1922.214.171.1240
Pumping performances of a helical molecular drag dump(MDP) and of a radial MDPs are numerically analyzed by using the direct simulation Monte Carlo (DSMC) method. A helical- and radial-MDP have rotating pumping channels cut on a cylinder and on a disk, respectively. For a helical MDP, the present results agree quantitatively with the previously known numerical results. For radial MDPs, both of the Type 1 (having pumping channels cut on the stationary disk) and of the Type 2 (having pumping channels cut on the rotating disk) are analyzed to predict their performances for various parameters, i.e., the radius of curvature center of the channel wall, the depth of the channel, the clearance between housing and disk, and the rotating speed. The results show that the performance of the Type 2 is superior to that of the Type 1, and that for all types the pumping efficiency decreases as the clearance increases. Also, the radial type MDP has larger leakage losses in the direction of pumping channel than does the helical one.
Thermal analysis of the wafers in LPCVD process
Kim, Il-Gyeong ; Jeong, Min-Cheol ; Yu, Seung-Il ; Chae, Seung-Gi ; Kim, U-Seung ; Nam, Gi-Heum ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 651~660
DOI : 10.22634/KSME-B.19126.96.36.1991
In the LPCVD reactor the temperature variations within the wafer load are the most important factor to maintain the thickness of the materials deposited on the surface of the wafer constant and to affect the deformation of each wafer. In this study the temporal variations of radial and axial temperature nonuniformities of each wafer in the LPCVD reactor are numerically estimated by assuming diffuse reflection. To verify the validity of the present numerical results, the present results obtained from the transient analysis are compared with those of Badgwell's work in which a steady-state condition was assumed. The main objective of this work is to determine the temporal variations of the temperature of each wafer in the LPCVD process since the wafers experience severe change in temperature in the early stage of the process.
Numerical study for the characteristics of diesel spray impinging on a wall
Yang, Hui-Cheon ; Jeong, Dong-Hwa ; Yu, Hong-Seon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 661~671
DOI : 10.22634/KSME-B.19188.8.131.521
It is unavoidable that the fuel spray impinges on the wall of piston cavity in a compact high-pressure D.I. diesel engine. Therefore the characteristics of impinging spray are the very significant information on the consideration and the simulation of its combustion processes including the formation mechanism of exhaust emission and the design of the combustion chamber. In this paper, the numerical simulation was performed to study the characteristics of impinging spray. The spray-wall impingement model used is Watkins and Park's model. Calculation parameters are the inclination angles and the ambient pressures. As the inclination angle increases, the impinging spray develops mainly to the direction of the downstream and scarcely flows to that of the upstream. The shape on the wall of the impinging spray is the circle in the case of the normal impingement, while it is the ellipse in that of the oblique impingement. As the ambient pressure increases, the growth of impinging spray on the wall in the radial direction decreases owing to the increase in the resistance of the ambient.
Three-dimensional mixed convection heat transfer characteristics in horizontal chemical vapor deposition reactor
O, Seong-Jin ; Park, Gyeong-U ; Park, Hui-Yong ; kim, Gi-Mun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 672~684
DOI : 10.22634/KSME-B.19184.108.40.2062
The three dimensional mixed convection heat transfer characteristics in an idealized horizontal CVD reactor with a tilted susceptor is investigated numerically. The governing equations are transformed into a general curvilinear systems. For computing fluid flow and heat transfer in a irregular shaped domain, the SIMPLE algorithm is extended to the present curvilinear coordinate, and a nonstaggered grid system is adopted. The Cartesian velocity components are used as the dependent variables in the momentum equations. The effects on heat transfer rate uniformity of the susecptor are investigated for various input flow rate and channel height. Furthermore the formation of return flow induced by transversal rolls is studied as a function of dimensionaless parameters
Developing of low Reynolds number k-.epsilon. model with improved .epsilon. equation
Song, Gyeong ; Yu, Geun-Jong ; Jo, Gang-Rae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 685~697
DOI : 10.22634/KSME-B.19220.127.116.115
Series of recent k-.epsilon. model modification have been carried out with the aid of DNS data to include the effect of near wall. Though these methods opened new way of turbulence modelings, newly developed turbulence models of its kind had yet shortcomings in prediction for the turbulent flows with various Reynolds numbers and various geometric conditions. As a remedy for these shortcomings, a new k-.epsilon. model proposed here by improving the dissipation rate equation and the damping function for eddy viscosity model. The new dissipation rate equation was modeled based on the energy spectrum and magnitude analysis. The damping function for eddy viscosity was also formulated on the ground of distribution of dissipation rate length scales near a wall and the DNS data. The new k-.epsilon. model was applied to the fully developed turbulent flows in a channel and a pipe with a wide range of Reynolds numbers. Prediction results showed that the present model represents properly the turbulence properties in all turbulent regions over a wide range of Reynolds numbers.
A model for columnar-dendritic solidification of binary alloys accounting for dendrite tip undercooling
Yu, Ho-Seon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 698~707
DOI : 10.22634/KSME-B.1918.104.22.1688
A simplified model for predicting microsegregation during columnar-dendritic solidification of binary alloys is developed, in which back diffusion, dendrite arm coarsening and dendrite tip undercooling are simultaneously incorporated. The inclusion of tip undercooling is accomplished by modifying the initial conditions of the existing solute diffusion model, in such forms that tip undercooling depresses the beginning of solidification below the liquidus temperature, and that the secondary arm spacing evolves in accordance with the minimum undercooling theory. Sample calculations for the well-known benchmark system show that the present predictions not only consist with the extablished limiting cases, but also agree favorably with the available experimental data within a reasonable tolerance. In particular, a typical decreasing trend in the eutectic fraction at high cooling rates is successfully resolved. Comparison of the individual and combined effects of characteristic parameters in reference with the limiting cases reveals the interactions among parameters. Every parameter plays the role of reducing the eutectic fraction, and the degree of influence depends primarily on the cooling rate. Coarsening enhances the effect of tip undercooling, while suppressing that of back diffusion. A vigorous back diffusion seems to restrain the apperance of the undercooling effect. Overall, each contribution of the three parameters to microsegregation is estimated to be of the same order, which suffices to justify the present study.
PTV velocity field measurements of flow around a triangular prism located behind a porous fence
Kim, Hyeong-Beom ; Lee, Sang-Jun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 708~715
DOI : 10.22634/KSME-B.1922.214.171.1248
The shelter effect of a porous wind fence on a triangular prism was experimentally investigated in a circulating water channel. A porous fence of porosity .epsilon.=38.5% was installed in front of the prism model. The fence and prism model were embedded in a turbulent boundary layer. The instantaneous velocity fields around the fence and prism model were measured by using the instantaneous velocity fields around the fence and prism model were measured by using the 2-frame PTV(Particle Tracking Velocimetry) system. By installing the fence in front of the prism, the recirculation flow region decreases compared with that of no fence case. The porous fence also decreases the mean velocity, turbulent intensity and turbulent kinetic energy around the prism. Especially, at the top of the prism, the turbulent kinetic energy is about half of that without the fence.
A Study on the Heat Transfer Enhancement by Mesh
Geum, Seong-Min ; Jeong, Dong-Su ; Kim, Jong-Bo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 5, 1998, Pages 716~724
DOI : 10.22634/KSME-B.19126.96.36.1996
The objective of this research was to investigate the enhancement of heat transfer by mesh in impinging air jet system. The technique used in this research is to place mesh as a turbulence promoter in front of the impinging plate. The heat transfer characteristics with and without mesh, the effect of clearances between impinging plate and mesh, the effect of distance between nozzle exit and impinging plate, and the effect of nozzle exit velocity have been studied experimentally. When mesh was installed in front of the impinging plate, heat transer has been increased due to the acceleration between rectangular holes and divided small jets. When clearances are changed, heat transfer comes to a maximum under the condition of C = 1 mm, irrespective of nozzle exit velocity or H/B. Also the average heat transfer enhancement with mesh has been increased about 44% under the condition of U = 18 m/s, H/B = 2 and C = 1 mm, compared to the result of a flat plate without mesh. And the results of this research are compared with existing heat transfer augmentation method by rectangular or circular rod.