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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
The Effect of Turbulence Intensity on the NOx Formation of Hydrogen Coaxial Jet Turbulent Diffusion Flames
Han, Ji-Ung ; Jeong, Yeong-Sik ; Lee, Chang-Eon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 147~155
DOI : 10.22634/KSME-B.2001.25.2.147
Experimental investigations were conducted for two hydrogen-nitrogen coaxial jet diffusion flames. A flame was a conventional coaxial jet diffusion flame and the other was a coaxial jet diffusion flame of which ambient air-jet turbulence was intensified. In this study, firstly two kinds of NOx measuring system were campared by using different convertors, secondly the NOx formation characteristics were investigated in order to examine the effect of turbulence intensity. In this study it is known that stainless convertor has some problem in the converting process from NO
to NO in fuel rich region but molybdenum convertor can detect the amount of NOx correctly. The increase of turbulence intensity reduces the thermal NOx less than a half in our experiment and this effect is conspicuous near the nozzle. The conversion rate from NO to NO
and the portion of NO
among NOx are increased with turbulence intensity. These NOx measurements will help to understand the influences of turbulence intensity on NOx formation.
Experimental Study for the Mixing Effect of the Driven Bar on Rotating Flow in a Closed Cylinder
Kim, Yu-Gon ; Kim, Dong-Gyu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 156~163
DOI : 10.22634/KSME-B.2001.25.2.156
The experiment is conducted on the rapidly rotating incompressible flow within a confined cylinder using LDV(Laser Doppler Velocimetry). The configurations of interest are the flows between a rotating upper disk with a bar and a stationary lower disk enclosed within a cylinder. The flow is considered to be an axisymmetric undisturbed basic flow. The results show that the flow is strongly dependent on the radius and the shape of bar but is negligibly affected by the Reynolds number in turbulent flow. It is observed that in the lid-driven case the main forms near the wall as the Reynolds number increases. The thin bar causes the second axial flow due to the suction effect and the thick bar causes the main flow to be pulled toward the surface of the bar. The step bar shows the dual effect of the two. 1:2 tilt bar shows that the main flow distributes wider than the other cases in which interference occurs due step bar.
Influence of the Unsteady Wake on the Flow and Heat Transfer in a Linear Turbine Cascade
Yun, Sun-Hyeon ; Sim, Jae-Gyeong ; Kim, Dong-Geon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 164~170
DOI : 10.22634/KSME-B.2001.25.2.164
The influence of unsteady wake on the flow and heat transfer characteristics in a four-vane linear cascade was experimentally investigated. The unsteady wake was generated with four rotating rectangular plates located upstream of the cascade. Tested inlet Reynolds number based on chord length was set to 66,000 by controlling free-stream velocity. A hot-wire anemometer system was employed to measure turbulent velocity components. For the convective heat transfer coefficients measurement on turbine blade surface, thermochromic liquid crystal and gold film Intrex were used. It was found that the unsteady wake enhances the turbulent motion in the cascade passage and accordingly promotes the development and transition of boundary layer. It was found that the heat transfer coefficients on the blade surface increase as the plate rotating speed increases. However, the increasing of heat transfer coefficients is not significant in the case that Strouhal number is higher than 0.503.
Study on Condensation Heat Transfer and Pressure Drop Characteristics of R-22 in Brazed Plate Heat Exchanger
Jeon, Chang-Deok ; Gwon, O-Gap ; Lee, Jin-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 171~179
DOI : 10.22634/KSME-B.2001.25.2.171
Experimental study has been carried out on the characteristics of pressure drop and heat transfer of brazed plate heat exchangers using R-22. Data are presented for the following range of variables: the mass flux (40∼90kg/
s), chevron angle (
) and inlet pressure of the refrigerant (1.4 and 1.6MPa). For both subcooled and two-phase flow, as chevron angle increases, pressure drop and heat transfer coefficient decrease. Condensation heat transfer coefficient and pressure drop were compared with the previously proposed correlations. Among therm, Traviss correlation agreed with experimental results within -40%∼-84% for heat transfer coefficient and -59%∼62% for pressure drop.
The Condensation Heat Transfer of Alternative Refrigerants for R-22 in Small Diameter Tubes
Son, Chang-Hyo ; Jeong, Jin-Ho ; O, Jong-Taek ; O, Hu-Gyu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 180~186
DOI : 10.22634/KSME-B.2001.25.2.180
The condensation heat transfer coefficients of pure refrigerants R-22, R-134a, and a binary refrigerant mixture R-410A flowing in a small diameter tube were investigated. The experiment apparatus consists of a refrigerant loop and a water loop. The main components of the refrigerant loop consist of a variable-speed pump, a mass flowmeter, an evaporator, and a condenser(test section). The water loop consists of a variable-speed pump, an isothermal tank, and a flowmeter. The condenser is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The test section consists of smooth, horizontal copper tube of 3.38mm outer diameter and 1.77mm inner diameter. The length of test section is 1220mm. The refrigerant mass fluxes varied from 450 to 1050kg/(㎡
s) and the average inlet and outlet qualities were 0.05 and 0.95, respectively. The main results were summarized as follows ; in the case of single-phase flow, the heat transfer coefficients increase with increasing mass flux. The heat transfer coefficient of R-410A was higher than that of R-22 and R-134a, and the heat transfer for small diameter tubes were about 20% to 27% higher than those predicted by Gnielinski. In the case of two-phase flow, the heat transfer coefficients also increase with increasing mass flux and quality. The condensation heat transfer coefficient of R-410A was slightly higher than that of R-22 and R-134a. Most of correlations proposed in the large diameter tube showed significant deviations with experimental data except for the ranges of low quality and low mass flux.
Modeling of Spray Impingement and Fuel Film Formation in HSDI Diesel Engines
Kim, Man-Sik ; Min, Gyeong-Deok ; Gang, Bo-Seon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 187~194
DOI : 10.22634/KSME-B.2001.25.2.187
Spray impingement and fuel film formation models were developed and incorporated into the computational fluid dynamics code. STAR-CD. The spray/wall interaction process was modeled by considering the change of behaviour with surface temperature conditions and the fuel film formation. We divided the behaviour of fuel droplets after impingement into rebound, spread and splash using the Weber number and the parameter K. The Spray impingement model accounts for mass conservation, energy conservation and heat transfer to the impinging droplets. The fuel film formation model was developed by integrating the continuity, Navier-Stokes and energy equations along the direction of fuel film thickness. Validation of the models was conducted using previous diesel spray experimental data and the present experimental results for the gasoline spray impingement. In all the cases, the prediction compared reasonably well with the experimental results. The spray impingement and fuel film formation models have been applied to the spray/wall impingement in high speed direct injection diesel engines.
Real Time Estimation in 1-Dimensional Temperature Distribution Using Modal Analysis and Observer
An, Jung-Yong ; Park, Yeong-Min ; Jeong, Seong-Jong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 195~201
DOI : 10.22634/KSME-B.2001.25.2.195
An inverse heat conduction problem(IHCP) arises when unknown heat fluxes and whole temperature field are to be found with temperature measurements of a few points. In this paper, observers are proposed as solution algorithm for the IHCP. A 1-dimensional heat transfer problem is modeled with modal analysis and state space equations. Position of the heat source is estimated through test heat inputs and the autocorrelation among a few of temperature data. The modified Bass-Gura method is used to design a state observer to estimate the intensity of heat source and the whole temperature field of a 1-dimensional body. To verify the reliability of this estimator, analytic solutions obtained from the proposed method are compared.
An Experimental Study on Quantitative Interpretation of Local Convective Heat Transfer for the Fin and Tube Heat Exchanger Using Lumped Capacitance Method
Kim, Ye-Yong ; Kim, Gwi-Sun ; Jeong, Gyu-Ha ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 205~215
DOI : 10.22634/KSME-B.2001.25.2.205
An experimental study has been performed to investigate the heat transfer characteristics of fin and tube heat exchanger. The existing transient and steady methods are very difficult to apply for the measurements of heat transfer coefficients of a thin heat transfer model. In this study the lumped capacitance method was adopted. The heat transfer coefficients were measured by using the lumped capacitance method based on the liquid crystal thermography. The method is validated through impinging jet and flat plate flow experiments. The two experiments showed that the results of the lumped capacitance method with polycarbonate model showed very good agreements with those of the transient method with acryl model. The lumped capacitance method showed similar results regardless of the thickness of polycarbonate model. The method was also applied for the heat transfer coefficient measurements of a fin and tube heat exchanger. The quantitative heat transfer coefficients of the plate fin were successfully obtained. As the frontal velocity increased, the heat transfer coefficients were increased, but the color-band shape showed similar patterns regardless of frontal velocity.
An Experimental Study on Evaporative Heat Transfer Characteristics in a Small Diameter Tube
Hwang, Yun-Uk ; Kim, Min-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 216~224
DOI : 10.22634/KSME-B.2001.25.2.216
Experiments have been performed to investigate evaporative heat transfer characteristics of R-134a flowing in a small diameter tube. Test section was made of stainless steel tube with an inner diameter of 2.2mm and was uniformly heated by electric current which was applied to the tube wall. The local saturation temperature of refrigerant flowing in a tube is calculated from the measured local saturation pressure by using an equation of state. Inner wall temperature was calculated from measured outer wall temperature, accounting for heat generation in the tube and one dimensional heat conduction through the tube wall. Mass quality of refrigerant flowing in a tube was calculated by considering energy balance in the pre-heater and the test section. Heat flux was varied from 19 to 64kW/
, and mass flux was chanted from 380 to 570kg/
s for each heat flux condition. From this study, heat transfer in a small diameter tube is affected by heat flux as well as mass flux for a wide range of mass quality. Heat transfer coefficient in a small diameter tube is much greater than that in medium sized tubes. Test results in this study are compared with Gungor and Winterton correlation, which gives an absolute average deviation of 27%.
An Experimental Study on the Three Dimensional Turbulent Flow Characteristics of Swirl Burner for Gas Furnace
Kim, Jang-Gwon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 225~234
DOI : 10.22634/KSME-B.2001.25.2.225
This paper represents the vector fields, three dimensional mean velocities, the turbulent intensities, the turbulent kinetic energy, and the Reynolds shear stresses in the X-Y plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rates 350 and 450ℓ/min respectively, which are equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. The vector plot shows that the maximum axial mean velocity component exists in the narrow slits situated radially on the edge of gas swirl burner, for that reason, there is some entrainment phenomena of ambient air in the outer region of burner. Moreover, mean velocities in the initial region are largely distributed near the outer region of burner at Y/R≒0.97, but they diffuse and develop into the center flow region of burner according to the increase of axial distance. The turbulent intensities and the turbulent kinetic energy due to large inclination of mean velocity and swirl effect show that the maximum value in the initial region of burner is formed in the narrow slits situated radially on the edge of gas swirl burner and large values are mainly formed in the entire region of burner after X/R=2.4358, hence, the combustion reaction is anticipated to occur actively near this region. And the Reynolds shear stresses are also largely distributed from slite to vanes of gas swirl burner in the intial region, but their values largely disappear after X/R=3.2052.
A Study on the Development of Low NOx Condensing Gas Boiler(I) -Design of Cylindrical Multi-Hole Premixed Burner-
Lee, Chang-Eon ; Geum, Seong-Min ; Jeong, Yeong-Sik ; Lee, Gyu-Yeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 235~243
DOI : 10.22634/KSME-B.2001.25.2.235
This paper describes a design study of the cylindrical multi-hole premixed burner to be used for condensing gas boiler which can raise performance and reduce NOx emission. In this study, specifications of the multi-hole burner (hole diameters and arrangement) are investigated using model flat burners in terms of flame stability, and combustion characteristics for stability and NOx emission are examined for cylindrical multi-hole burner. As a result, the equivalence ratio for optimum operation condition of the cylindrical burner is around 0.72(0.7∼0.75). In this condition, turn-down ratio becomes 3 : 1 at least which is suitable for proportional control. The NOx and CO emission is less than 40ppm and 25ppm(0
0% basis), respectively. This burner can be applied LPG as well as NG because there is no difference for stable combustion region.
A Study on the Development of Low NOx Condensing Gas Boiler(II) -Design of Heat Exchanger and Performance of Boiler-
Lee, Chang-Eon ; Geum, Seong-Min ; Jeong, Yeong-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 244~251
DOI : 10.22634/KSME-B.2001.25.2.244
This paper describes a design study of heat exchanger assembly to be used for low NOx condensing gas boiler. In this study, specifications of each heat exchanger components(upper and lower fin-type HEX, coil-type HEX, baffle) were investigated experimently by using model apparatus and analytical model, and comprehensive performances of the pilot gas boiler were examined. As a result, the boiler efficiency for heating and hot-water reached 90% and 94%, respectively. NOx and CO emission are less than 50ppm and 200ppm (0
0% basis), respectively, which are very improved results than those of conventional bunsen-type boiler. But it is considered that supplementary investigations necessary for CO emission improvement and optimum design with boiler capacity.
Flow Analysis for the Geometry Optimization of Combustion Chamber of Central Flow Type Waste Incinerator
Lee, Jin-Uk ; Kim, Seong-Bae ; Yun, Yong-Seung ; Kim, Hyeon-Jin ; Heo, Il-Sang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 252~259
DOI : 10.22634/KSME-B.2001.25.2.252
Computational study has been performed to observe the flow characteristics of combustion chamber for geometrical modification in municipal solid waste incinerator. A series of geometrical modification has been carried out as an attempt to reduce the size of recirculation zone, to obtain uniform flow field in the secondary combustion chamber and to improve the mixing of combustion gas. Two dimensional non-reacting turbulent flow has been studied as the first step to get such goals and the result of design optimization is presented. In addition, three dimensional non-reacting and reacting flow analyses were performed to verify the validity of two dimensional approach.
An Experimental Study on Drag Reduction of Grooved Cylinders
Im, Hui-Chang ; Lee, Sang-Jun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 260~268
DOI : 10.22634/KSME-B.2001.25.2.260
Wake structures behind two circular cylinders with different groove configurations(U and V-shape) have been investigated experimentally. The results were compared with those for the smooth cylinder having the same diameter D. The drag force, mean velocity and turbulent intensity profiles of wake behind the cylinders were measured with varying the Reynolds number in the range of Re(sub)D=8,000∼14,000. As a result, the U-shaped groove was found to reduce the drag up to 18.6%, but the V-shaped groove reduced drag force only 2.5% compared with the smooth cylinder. As the Reynolds number increases, the vortex shedding frequency becomes a little larger than that of the smooth cylinder. The visualized flow using the smoke-wire and particle tracing methods shows the flow structure qualitatively.
Computations of the Bleed-Pump Type Subsonic/Sonic Ejector Flows
Choe, Bo-Gyu ; Gu, Byeong-Su ; Kim, Hui-Dong ; Kim, Deok-Jul ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 2, 2001, Pages 269~276
DOI : 10.22634/KSME-B.2001.25.2.269
This paper dipicts the computational results for the axisymmetric subsonic/sonic ejector systems with a second throat. The numerical simulations are based on a fully implicit finite volume scheme of the compressible Reynolds-Averaged Navier-Stokes equation in a domain that extends from the stagnation chamber to the ejector diffuser exit. In order to obtain practical design factors for subsonic/sonic ejector systems, the ejector throat area, the mixing section configuration, and the ejector throat length were changed in computations. For the subsonic/sonic ejector systems operating in the range of low operation pressure ratio, the effects of the design factors on the flow are discussed.