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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 20, Issue 12 - Dec 1996
Volume 20, Issue 11 - Nov 1996
Volume 20, Issue 10 - Oct 1996
Volume 20, Issue 9 - Sep 1996
Volume 20, Issue 8 - Aug 1996
Volume 20, Issue 7 - Jul 1996
Volume 20, Issue 6 - Jun 1996
Volume 20, Issue 5 - May 1996
Volume 20, Issue 4 - Apr 1996
Volume 20, Issue 3 - Mar 1996
Volume 20, Issue 2 - Feb 1996
Volume 20, Issue 1 - Jan 1996
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Three-dimensional flow and pressure loss of a film-cooling jets injected in spanwise direction
Lee, Sang-U ; Kim,Yong-Beom ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1363~1375
DOI : 10.22634/KSME-B.19220.127.116.113
Oil-film flow visualizations and three-dimensional flow measurements using a five-hole probe have been conducted to investigate three-dimensional flow characteristics and total pressure losses of a row of film-cooling jets injected in spanwise direction. For several span-to-diameter ratios, experiments are performed in the case of three velocity ratios of 0.5, 1.0 and 1.5. The flow measurements show that downstream flow due to the injection is characterized by a single streamwise vortex instead of a pair of counter-rotating vortices, which appear in the case of streamwise injection, and the vortex strength strongly depends on the velocity ratio. Regardless of the velocity*y ratio, presence of the spanwise film-cooling jets always produces total pressure loss, which is pronounced when the velocity ratio is large. It has also been found that the production of the total pressure loss is closely related to the secondary vortical flow. In addition, effects of the span-to-diameter ratio on the flow and total pressure loss are discussed in detail.
Theoretical study of flow and heat transfer around silicon bridge in a flow sensor
Hwang, Ho-Yeong ; Kim, Ho-Yeong ; Jeong, Jin-Taek ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1376~1384
DOI : 10.22634/KSME-B.1918.104.22.1686
Measuring the velocity of fluid flow, semiconductor flow sensors are widely used in the various fields of engineering and science such as the semiconductor manufacturing processes and electronic control engines for automobiles. In the near future, this type of sensors will replace present hot wire type sensors or other type flow sensor due to its low price, easy handling and small size. To develop the advanced semiconductor flow sensor, it is necessary to obtain characteristics of the flow and the heat transfer around the sensor in advance. In the present study, the theoretical analysis including mathematical modeling and numerical calculation to predict the characteristics of heat transfer and flow field around the sensor was carried out. The main parameters for optimum design of the flow sensor are the free stream velocity, the heat generation rate of silicon arm and the distance between arms. Effects of these parameters on flow and heat transfer around the sensor and the temperature difference between arms are examined.
Heat transfer analysis on the heat exchanger of a stirling cycle machine
Lee, Dae-Yeong ; Jo, Gwan-Sik ; No, Seung-Tak ; Kim, Byeong-Ha ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1385~1394
DOI : 10.22634/KSME-B.1922.214.171.1245
A theoretical analysis was performed on the heat transfer by laminar oscillating flow in a simplified heat exchanger of a Stirling cycle machine and the results were compared with the experiment of Hwang. In the analysis the general solution to the temperature field obtained by Lee et. al was applied and extended to a more realistic situation. The results show that the heat transfer is influenced by the ratio of the swept distance of the fluid to the length of the heat exchanger as well as the oscillation frequency. This is well consistent with the result of Hwang's experiment. It is also revealed that there exist three distinct regimes having different heat transfer mechanisms. Through the scale analysis the main parameters governing the heat transfer in each regime are reduced and the dependency of the heat transfer on the parameters are examined.
A study on the local heat transfer in rectangular impinging water jet cooling system
Lee, Jong-Su ; Eom, Gi-Chan ; Choe, Guk-Gwang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1395~1405
DOI : 10.22634/KSME-B.19126.96.36.1995
The purpose of this experimental research is to investigate the local heat transfer characteristics in the upward free water jet impinged on a downward flat plate of uniform heat flux. The inner shape of rectangular nozzle used was sine curve type and its contraction ratio of inlet to outlet area was five. Experimental parameters considered were Reynolds number, nozzle exit-flat plate distance, and level of supplementary water. Local Nusselt number was influenced by Reynolds number, Prandtl number, supplementary water level, and distance between the nozzle exit and flat plate. Within the impingement region, the Nusselt number has a maximum value on the nozzle center axis and decreases monotonically outward from center. Outside of the impingement region, on the other hand, the Nusselt number has a secondary peak near the position where the distance from nozzle center reaches four times the nozzle width. However if nozzle exit velocity exceeds 6.2 m/s, the secondary peak appears also in the impingement region. The empirical equation for the stagnation heat transfer is a function of Prandtl, Reynolds, and axial distance from the nozzle exit. The optimum level of supplementary water to augment the heat transfer rate at stagnation point was found to be twice the nozzle width.
Pool boiling heat transfer enhancement by perforated plates
Kim, Nae-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1406~1415
DOI : 10.22634/KSME-B.19188.8.131.526
Several recent studies have revealed that boiling heat transfer may be considerably enhanced in a narrow restricted region. In his study, the narrow restricted region was formed by attaching a perforated plate on top of a boiling surface. Through systematic experiments, effects of the hole size, hole pattern, gap width between the perforated plate and the boiling surface were investigated using water or R-113. Results show that perforated plates considerably enhance the boiling of water or R-113. For water, especially, they have outperformed commercial enhanced tubes, which confirms that boiling enhancement mechanism of the perforated plate (thin film evaporation beneath the elongated bubble) is very effective to the boiling of high surface tension liquids such as water. Optimum configuration was found - 3.0 mm hole diameter, 15 mm * 15 mm hole pattern, 0.3 ~ 0.5 mm gap width for water, and 2.0 mm hole diameter, 3.5 mm * 3.5 mm hole pattern, O.5 mm gap width for R-113. A correlation which correlates most of the data within .+-. 30% was also developed.
Multi-block Technique for a duct flow with multiple outlets
Jeon,Yong-Deok ; Lee, Jae-Heon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1416~1425
DOI : 10.22634/KSME-B.19184.108.40.2066
A numerical method has been proposed to predict 3-dimensional flow in a duct system with multiple outlets. For the duct system, it is supposed that the pressure values are given at multiple outlets while the velocity profile is given at a inlet. To maintain the continuity of pressure distribution between main and branch duct, present method allows that the pressure value taken from analysis of branch duct can be converted to the main duct analysis. The result from present method which can handle the pressure boundary condition closely coincided with that from regular method which can handle the velocity boundary condition only. Furthermore the flow distribution from present method showed good agreement with that from the single block method. From the comparison of the present method with the total pressure method used for engineering duct design, 13% of discrepancy in pressure loss was shown between the main duct inlet and the branch duct outlet.
Analysis of effectiveness for a stirling machine regenerator
Jo, Gwan-Sik ; Lee, Dae-Yeong ; No, Seung-Tak ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1426~1436
DOI : 10.22634/KSME-B.19220.127.116.116
The effectiveness of the regenerator pertaining to Stirling cycle machines is studied by analyzing the heat transfer characteristics of the oscillating flow in a tube, and a new consistent definition of the regenerator effectiveness can be expressed by the ratio of the heat transfer in axial direction (Q
axial/) to that in transverse direction (Q/su w/), and its approximate form is obtained as a function of Nusselt number for practical utility. Since an approximate value of the ratio Q
axial//Qsub w/ can be expressed in terms of the time-averaged rather than transient temperatures, this expression is useful to estimate the heat transfer coefficient in the Stirling machine regenerator experimentally.
Analysis on the solute redistribution in coarsening dendrite arms during solidification of binary metal alloys
Yu, Ho-Seon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1437~1448
DOI : 10.22634/KSME-B.1918.104.22.1687
This paper presents a simplified model for approximate analysis of the solute redistribution in coarsening dendrite arms during solidification of binary metal alloys. By introducing a quadratic concentration profile with a time-dependent coefficient, the integral equation for diffusion in the solid phase is reduced to a simple differential relation between the coefficient and the solid-liquid interface position. The solid fraction corresponding to the system temperature is readily determined from the relation, phase equilibrium and the overall solute balance in which the liquid phase is assumed to be completely mixed. In order to validate the developed model, calculations are performed for the directional solidification of Al-4.9 mass Cu alloy. The predicted eutectic fractions for a wide range of the cooling rate reasonably agree with data from the well-known experiment as well as sophisticated numerical analyses. Also, the results for the back diffusion limits are consistent with available references. Additional calculations show that the characteristic parameters such as the coarsening, density variation and nonlinarity in the phase diagram significantly affect the microsegregation. Owing to the simplicity, efficiency and compatibility, the present model may be suitable for the micro-macroscopic solidification model as a microscopic component.
Thermal stratification in a horizontal pipe of pressurizer surge line
Jeong, Il-Seok ; Kim, Yu ; Park, Man-Heung ; Yeom, Hak-Gi ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1449~1457
DOI : 10.22634/KSME-B.1922.214.171.1249
In this paper, the unsteady two dimensional model for the thermal stratification in the pressurizer surge line of PWR plant has been proposed to numerically investigate the heat transfer and flow characteristics. The dimensionless governing equations are solved by using the Control Volume Formulation and SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm. The temperature profile of fluids and pipe wall with time are shown when the thermal stratification occurs in the horizontal pipe. The numerical result shows that the maximum dimensionless temperature difference is about O.514 between hot and cold section of pipe wall at dimensionless time 1,632.
A study on fluid flow and heat transfer around the circular cylinder located on a flat plate in crossflow
Lee, Gi-Baek ; Son, Jeong-Ho ; Yang, Jang-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1458~1471
DOI : 10.22634/KSME-B.19126.96.36.1998
The present study is concerned with the heat transfer enhancement associated with a symmetrical or asymmetrical horseshoe vortex in front of and around the circular cylinder centered between the side walls of a wind tunnel. The static pressure measurements and the flow visualization in front of and around cylinders have been performed to determine the existence of horseshoe vortex. The hue-capturing method using the thermochromatic liquid crystals with great spatial resolution was used to obtain the local information of the endwall heat transfer coefficients. In case of one cylinder, the convective heat transfer coefficients of the region where the horseshoe vortex exists are larger than those of any other region. In case of two cylinders with tandem arrangement, the heat transfer rate of gap spacing (d/D= 1.5) is higher than that of gap spacings (d/D=2.0 or 2.5).
A study on the drag reduction in a horizontal two phase flow
Cha, Gyeong-Ok ; Kim, Jae-Geun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1472~1480
DOI : 10.22634/KSME-B.19188.8.131.522
The phenomena of drag reduction using small quantities of a linear macromolecules has attracted the attention of experimental investigations. It is well known that drag reduction in single phase liquid flow is affected by polymer materials, molecular weight, polymer concentration, pipe diameter and flow velocity. But the research on drag reduction in two phase flow has not intensively investigated. Drag reduction can be applied to phase change system such as chemical reactor, pool and boiling flow, and to flow with cavitation which occurs pump impellers. The purpose of the present work is to evaluate the drag reduction by measuring pressure drop, mean liquid velocity, and turbulent intensity and determine the effects of polymer additives on drag reduction in horizontal two phase flow. Experimental results show higher drag reduction using co-polymer comparing with using polyacrylamide. Mean liquid velocities increase as adding more polymer, and turbulent intensities decrease as the distance for the wall in inversed.
Study on enhancement of evaporating heat transfer in narrow horizontal annular crevices
Bae, Sang-Cheol ; Kim, Jong-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1481~1490
DOI : 10.22634/KSME-B.19184.108.40.2061
This study is intend to improve flow pattern within evaporator, which is low quality and low mass flux, by installing narrow horizontal annular crevice so that enhance heat transfer coefficient. The motive, which made to study heat transfer enhancement by using narrow annular crevice, came from capillary phenomena and pumping force of generating vapor on refrigerant boiling. Tests were run about 5 models of turbulence promoter with CFC-12, in the range of evaporating temperature (15.deg. C), mass flux (50 to 100 kg/m
2/s), heat flux (3.4 to 6.7 kW/m
2/), quality (0.1 to O.5). It is observed that flow pattern within evaporator is changed closely to semi-annular flow or annular flow, of which refrigerant liquid is reached to the upper side of tube by using narrow annular crevice. When the narrow annular crevice is installed in the evaporator tube, local heat transfer coefficient is generally more improved than that of smooth tube. That fact is according to observed result of flow pattern. It is learned that narrow annular crevice has more efficiency at a low mass flux. At the TP-5, enhancement of heat transfer rate is about 170% compare to that of smooth tube on a low mass flux (50 kg/m
2/s), and it is about 134% on a high mass flux (100 kg/M
2/S), so that we know that it is on a very high condition.
The performance and flow characteristics of a small propeller fan with a back-plate
Gang, Sin-Hyeong ; Kim, Jin-Gwon ; Lee, Seung-Bae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1491~1500
DOI : 10.22634/KSME-B.19220.127.116.111
Unstable performance deterioration was found on the performance curve of a small propeller fan with a back plate. To investigate this phenomenon and the effects of the back-plate on the performance of the fan, performance tests and flow measurement using 3-hole pitot tube were carried out. Measurements showed that when the flow rate is small, the radial flow dominates, and when the flow rate is large, the axial flow dominates. Performance characteristic of the propeller fan changes from radial to axial type as the flow rate increases. Unstable performance changes are the result of type change of the flow through the fan.
Discharge and loss coefficients for viscoelastic fluids in differential pressure flow meters
Jeon, U-Cheong ; Jo, Byeong-Su ; Baek, Byeong-Jun ; Park, Bok-Chun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1501~1509
DOI : 10.22634/KSME-B.1918.104.22.1681
Differential pressure devices such as an orifice and Venturi are widely used in the measurement of flow rate of fluid mainly due to cost effectiveness and easy installation. In the current study, the viscoelastic effect on discharge and loss coefficients of those flow meters were investigated experimentally. Aqueous solutions of Polyacrylamide (200, 500, and 800 ppm) as viscoelastic fluids were used. Discharge coefficient of an orifice for viscoelastic fluids increased significantly up to approximately 15-20% when compared with that for water, while loss coefficient decreased up to 10-25% depending on the diameter ratio, .betha.. Also, pressure recovery for viscoelastic fluids was extended much longer than that for water. On the other hand, discharge and loss coefficients of Venturi for viscoelastic fluids were found to be strongly dependent on the Reynolds number. In both flow meters, the concentration effect for discharge and loss coefficients was not observed at more over than 200 ppm of aqueous solution. Conclusively, orifice and Venturi flow meters should be calibrated very carefully in the flow rate measurement for viscoelastic fluids.
Effect of the separating streamline curvature on the axisymmetric backward-facing step flow
Kim, Gyeong-Cheon ; Bu, Jeong-Suk ; Jeong, Ji-Yung ; Yang, Jong-Pil ;
Transactions of the Korean Society of Mechanical Engineers B, volume 20, issue 4, 1996, Pages 1510~1520
DOI : 10.22634/KSME-B.1922.214.171.1240
An experimental study on the flow over the axisymmetric backward-facing step was carried out. The purpose of the present study is to investigate the effect of the separating streamline curvature on the reattachment length and to understand the structure of recirculating flows. Local mean and fluctuating velocity components were measured in the separating and reattaching axisymmetric region of turbulent boundary layer on the wall of convex cylinder placed in a water tunnel by using 2-color 4-beam fiber optics laser Doppler velocimetry. The study demonstrates that the reattachment length increases with increasing separating streamline curvature. It is also observed that the reverse flow velocity and turbulent kinetic energy increase with an increase in the separating streamline curvature. In addition, the behavior of maximum turbulent stresses show that the effect of separating streamline curvature is larger in the region of recirculating zone(X/H<2) than in the region of reattachment point.