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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 21, Issue 12 - Dec 1997
Volume 21, Issue 11 - Nov 1997
Volume 21, Issue 10 - Oct 1997
Volume 21, Issue 9 - Sep 1997
Volume 21, Issue 8 - Aug 1997
Volume 21, Issue 7 - Jul 1997
Volume 21, Issue 6 - Jun 1997
Volume 21, Issue 5 - May 1997
Volume 21, Issue 4 - Apr 1997
Volume 21, Issue 3 - Mar 1997
Volume 21, Issue 2 - Feb 1997
Volume 21, Issue 1 - Jan 1997
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Experimental study on nucleate boiling heat transfer enhancement using an electric field
Gwon, Yeong-Cheol ; Kim, Mu-Hwan ; Gang, In-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1563~1575
DOI : 10.22634/KSME-B.19220.127.116.113
To understand EHD nucleate boiling heat transfer enhancement, EHD effects on R-113 nucleate boiling heat transfer in a non-uniform electric field were investigated. The pool boiling heat transfer and the dynamic behavior of bubbles in d.c./a.c. electric fields under a saturated or subcooled boiling were studied by using a plate-wire electrode and a high speed camera. From the pool boiling heat transfer study, the shift of the pool boiling curve, the increase of the heat transfer and the delay of ONB and CHF points to higher heat fluxes were observed. From the dynamic behavior of bubbles, it was observed that bubbles departed away from the whole surface of the heated wire in radial direction due to EHD effects by a nonuniform electric field. With increasing applied voltages, the bubble size decreased and the active nucleation site and the departure number of bubbles showed the different trend. The present study indicates that the EHD nucleate boiling heat transfer is closely connection with the dynamic behavior of bubbles and the secondary flow induced near the heated surface. Therefore, the basic studies on the bubble behavior such as bubble frequency, bubble diameter, bubble velocity and flow characteristics are necessary for complete understanding of the enhancement mechanism of the boiling heat transfer using an electric field.
Combustion and Microexplosion of Al/Liquid Fuel Slurry Droplets(I)-Ewperimental Study-
Byeon, Do-Yeong ; Jo, Ju-Hyeong ; An, Guk-Yeong ; Baek, Seung-Uk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1576~1585
DOI : 10.22634/KSME-B.1918.104.22.1686
The microexplosive combustion of a slurry droplet was investigated experimentally. The microexplosion has been approximately considered to be caused by pressure build-up in the shell and to be promoted by heterogeneous nucleation of liquid carrier, which is due to the suppression of evaporation and subsequent superheating of liquid carrier. To closely investigate the pressure build-up and the heterogeneous nucleation, the experiments were conducted in an electric combustor, of which temperature was controllable (400 K-900 K). And the effects of two aligned droplets on the interactive combustion and microexplosion were found in a hot post region of a flat flame burner. Transient internal temperature distributions for slurry droplets were measured. And the shell formation and the microexplosion of suspended A1/JP-8 and Al/n-heptane slurry droplets were examined with various surfactant concentrations (0.5-5 wt%) and solid loadings (10-50 wt.%). The microexplosion time of binary array of droplets was found to be less than that of the isolated droplet due to radiative interaction between droplets.
Numerical analysis of turbulent flow around a small propeller fan operating at the inlet of open chamber
O, Geon-Je ; Gang, Sin-Hyeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1586~1594
DOI : 10.22634/KSME-B.1922.214.171.1246
Performance characteristics of a small propeller fan are numerically investigated solving the continuity and Reynolds-averaged Navier-Stokes equations. The Reynolds stresses for turbulent transport are modelled using a k-.epsilon. turbulence model. The present numerical procedure is constructed using the Finite Volume Method with the SIMPLE algorithms. The performance parameters obtained from the calculations are compared with the measured values for the various flow rates. A performance test of the fan shows different characteristics between a radial type at small flow rates and an axial type at large flow rates. Comparisons between the predictions and the measurements show that the predicted results are in good agreement with the measured values and reasonably reproduce the sharp variations of the power and head coefficient around a flow coefficient .PHI.=0.3. These comparisons indicate that the present numerical method is capable of resolving the performance characteristics with reasonable accuracy. At low flow rates, it is found that the flow enters the fan in an axial direction and is discharged radially outward at the tip which happens in the centrifugal fan. The centrifugal effect makes a significant difference in the characteristics of a fan at the low and high values of flow coefficient.
The natural convection in a three dimensional enclosure using color capturing technique and computation
Lee, Gi-Baek ; Kim, Tae-Yeong ; Yang, Jang-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1595~1607
DOI : 10.22634/KSME-B.19126.96.36.1995
The natural convection of a horizontal layer heated from below in a three-dimensional rectangular enclosure was dealt with both numerically and experimentally. The aspect ratios are 1:2:3.5 and Boussinesq fluid is water with the Prandtl number of 5.0. This experimental study showed how to measure the variation of temperature field in a 3-D rectangular enclosure with small aspect ratios by using TLC(Thermochromic Liquid Crystal) and color capturing technique. The experimental temperature field had periodic characteristics of 75 sec at Ra=2.37*10
. But the numerical convection flow had periodic characteristics of 79 sec at the same Rayleigh number. In three dimensional computation it was found that the convection roll structure bifurcated from four rolls to two rolls as the Rayleigh number is increased.
Effects of geometric parameters of fluidic flow meter on flow rate
Park, Gyeong-Am ; Yun, Gi-Yeong ; Yu, Seong-Yeon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1608~1614
DOI : 10.22634/KSME-B.19188.8.131.528
The fluidic flow meter detects the gas flow rate based on the principle of fluidic oscillation instead of the conventional displacement method. It has many merits: wide rangeability, no moving mechanical parts and calibration insensitive to physical properties of fluids. The width of nozzle, size of oscillation chamber, size of target, width of outlet are tested to obtain the effects of jet oscillation on the fluidic flow meter. As the width of nozzle is too wide compared with the size of target, jet oscillation is unstable. The oscillation frequency decreases as the distance between the nozzle and target increases and also as the distance between target and outlet contraction increases. Two different vortexes exist in the front and the rear regions of the target, and they affect the oscillation frequency. The outlet contraction is very important, because the feedback flow is generated by the blocking of the flow. As the width of outlet increases, the jet oscillation frequency decreases. The linearity of this tested flow meter is quite good.
A numerical study on a chaotic stirring in a model for a single screw extruder
Seo,Yong-Gwon ; Kim,Yong-Gyun ; Mun, Jong-Chun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1615~1623
DOI : 10.22634/KSME-B.19184.108.40.2065
Numerical study on the chaotic stirring of the screw extruder model proposed has been performed. The velocity field was used in obtaining the trajectories of passive particles for studying the stirring effect of the screw extruder. Two nonlinear dynamical tools, that are Poincare sections and Lyapunov exponents, were used in analysing the stirring effect. The Poincare sections and the Lyapunov exponents show that the stirring effect is most satisfactory, when n(the number of flights in a section) is 1, for the case a (aspect ratio ; flight height divided by the spacing between flights) being O.1. It is also required to set n=3, or 5 at a= 0.2, 0.3 for a uniform stirring.
Unsteady cascade flow calculations of using dual time stepping and the k-
Choe, Chang-Ho ; Yu, Jeong-Yeol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1624~1634
DOI : 10.22634/KSME-B.19220.127.116.114
A numerical study on two-dimensional unsteady transonic cascade flow has been performed by adopting dual time stepping and the k-.omega. turbulence model. An explicit 4 stage Runge-Kutta scheme for the compressible Navier-Stokes equations and an implicit Gauss-Seidel iteration scheme for the k-.omega. turbulence model are proposed for fictitious time stepping. This mixed time stepping scheme ensures the stability of numerical computation and exhibits a good convergence property with less computation time. Typical steady-state convergence accelerating schemes such as local time stepping, residual smoothing and multigrid combined with dual time stepping shows good convergence properties. Numerical results are presented for unsteady laminar flow past a cylinder and turbulent shock buffeting problem for bicircular arc cascade flow is discussed.
Characterization of the internal flow and fuel spray from an impinging flow nozzle
Ha, Seong-Eop ; Kim, Heung-Yeol ; Gu, Ja-Ye ; Ryu, Gu-Yeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1635~1646
DOI : 10.22634/KSME-B.1918.104.22.1685
The nozzle length to diameter ratio of real diesel nozzles is about 2-8 which is not long enough for a fully developed and stabilized flow. The characteristics of the flow such as turbulence at the nozzle exit which affect the development of the spray can be enhanced by impinging the flow inside nozzle. The flow details inside the impinging nozzles have been investigated both experimentally and numerically. The mean velocities, the fluctuating velocities, and discharge coefficients in the impinging inlet nozzles, round inlet nozzle, and sharp inlet nozzle were obtained at various Reynolds number. The developing feature of the external spray were photographed by still camera and the droplet sizes and velocities were also measured by laser Doppler technique. The spray angle was greater and the droplet sizes near the spray axis were smaller with the impinging flow inside nozzle.
A study on the cyclic variability as a function of ignition energy in spark ignition engines
Han, Seong-Bin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1647~1655
DOI : 10.22634/KSME-B.1922.214.171.1247
The cyclic variations can be characterized by the variations in different type of parameters. These parameters may be grouped into four main categories: pressure-related parameters, combustion-related parameters, flame front-related parameters, and exhaust gas-related parameters. One of the resultant effects of the cycle-by-cycle variation in the combustion process, which is the most important with regard to the engine performance characteristics, is the cycle-by-cycle variation in IMEP. This paper uses the repetitive discharge igniter, which can change the ignition energy easily, to study on idle stability in a spark ignition engine. From this device, the 6 number of spark and 0.20 ms spark interval, it is very available for the idle stability.
Condensing heat transfer characteristics of hydrocarbon refrigerants in a horizontal tube
Jang, Yeong-Su ; Kim, Min-Su ; No, Seung-Tak ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1656~1667
DOI : 10.22634/KSME-B.19126.96.36.1996
Condensing heat transfer characteristics of hydrocarbon refrigerants are experimentally investigated. Single component hydrocarbon refrigerants (propane, isobutane, butane and propylene) and binary mixtures of propane/isobutane and propane/butane are considered as test fluids. Local condensing heat transfer coefficients of selected refrigerants are obtained from overall conductance measurement. Average heat transfer coefficients at different mass fluxes and heat transfer rates are shown and compared with those of R22. Pure hydrocarbon refrigerants have higher values of heat transfer coefficient than R22. It is also found that there is a heat transfer degradation for hydrocarbon mixtures due to composition variation during condensation. Measured condensing heat transfer coefficients are compared with predicted values by available correlations. An empirical correlation for pure and mixed hydrocarbon is developed, and it shows good agreement with experimental data.
Numerical analysis in oscillating flow considering orientation of porous media regenerator
Yang, Mun-Heum ; Park, Sang-Jin ; No, Seung-Tak ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1668~1678
DOI : 10.22634/KSME-B.19188.8.131.528
Numerical analyses were performed to investigate the characteristics of regenerator in oscillating flow by using moving boundary method and Darcy model. In this work, periodic adiabatic boundary condition was suggested as the boundary condition of adiabatic part so that the effects of the thermal inertia of the wall could be considered. In carrying out numerical analyses, two models were applied and compared. One called isotropic model has the same thermal conductivity in radial and axial directions within a porous media. The other called aeolotropic model has different conductivity in each directions. Isotropic model could not show the advantage of energy reduction which needs to maintain constant wall temperature difference between heater and cooler. But aeolotropic model could simulate the reduction of energy consumption.
OD analysis of fluid flows given by one-dimensional shallow water equations
Seo,Yong-Gwon ; Park, Jun-Gwan ; Mun, Jong-Chun ; Kim, Yong-Gyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1679~1689
DOI : 10.22634/KSME-B.19184.108.40.2069
In this paper, a precise description is given to the basic theory as well as the detailed algorithms for the numerical treatment of the method of POD (proper orthogonal decomposition). This method is then applied to analysing the numerical solutions of one-dimensional shallow-water equations to show how the method is affected by various parameters such as the sampling time, sampling numbers, and the spatial resolution for the autocorrelation function. A few curious features associated with this flow model found through the analysis are further explained and discussed.
Gasification characteristics in an entrained flow coal gasifier
Yu, Yeong-Don ; Yun,Yong-Seung ; An, Dal-Hong ; Park, Ho-Yeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1690~1700
DOI : 10.22634/KSME-B.19220.127.116.110
Entrained coal gasification tests with Datong coal were performed to assess the influence of oxygen/coal ration and pressure. When gasification condition in oxygen/coal ratio has changed from 0.5 to 1.0, optimal gasification condition from low pressure runs was oxygen/coal ratio of approximately 0.9 where CO was produced about 40% and H, about 20%. Under the pressure condition of 12-14 atmospheres, optimal oxygen/coal ratio value was in the region of 0.6 where CO was produced about 55% and H2about 25%. From these results, it was found that the oxygen/ coal ratio for the maximum production of CO and H, was decreasing with the increase in gasifier pressure and also, with increasing oxygen content, carbon conversion was increased. For the Chinese Datong coal, cold gas efficiency was in the range of 40-80%.
A study of cycle-to-cycle variations with dwell angle in spark ignition engines
Han, Seong-Bin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1701~1709
DOI : 10.22634/KSME-B.1918.104.22.1681
The diagnostic used to observe the early flame development was a fiber optic spark plug, which enabled measurement of the flame front arrival times on a cycle-to-cycle basis. The data obtained with this fiber optic spark plug were analyzed to obtain two parameters to describe the behavior of the flame kernel : an expansion speed and a convection velocity. In addition, synchronized cylinder pressure data were taken to compare with the fiber optic spark plug data on a cyclic basis. Heat release analysis was performed on the cylinder pressure data to obtain the mass burning profile of the charge for each cycle. There was a significant correlation observed in the initial flame duration and the kernel expansion speed with dwell angle.
An approximate analytical solution for the initial transient process of close-contact melting on an isothermal surface
Yu, Ho-Seon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 12, 1997, Pages 1710~1719
DOI : 10.22634/KSME-B.1922.214.171.1240
An approximate analytical solution for the initial transient process of close-contact melting occurring between a phase change material kept at its melting temperature and an isothermally heated flat surface is derived. The model is so developed that it can cover both rectangular and circular cross-sectional solid blocks. Normalization of simplified model equations in reference to the steady solution enables the solution to be expressed in a generalized form depending on the liquid-to-solid density ratio only. A selected result shows an excellent agreement with the previously reported numerical data, which justifies the present approach. The solution appears to be capable of describing all the fundamental characteristics of the transient process. In particular, dependence of the solid descending velocity oft the density ratio at the early stage of melting is successfully resolved. The effects of other parameters except the density ratio on the transient behaviors are efficiently represented via the steady solution implied in the normalized result. A simple approximate method for estimating the effect of convection on heat transfer across the liquid film is also proposed.