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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 35, Issue 12 - Dec 2011
Volume 35, Issue 11 - Nov 2011
Volume 35, Issue 10 - Oct 2011
Volume 35, Issue 9 - Sep 2011
Volume 35, Issue 8 - Aug 2011
Volume 35, Issue 7 - Jul 2011
Volume 35, Issue 6 - Jun 2011
Volume 35, Issue 5 - May 2011
Volume 35, Issue 4 - Apr 2011
Volume 35, Issue 3 - Mar 2011
Volume 35, Issue 2 - Feb 2011
Volume 35, Issue 1 - Jan 2011
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Analytical Study on the Heat Transfer Characteristics of a Spirally Coiled Circular Fin-Tube Evaporator Operated Under Non-Frosting Conditions
Lee, Moo-Yeon ; Kang, Tae-Hyung ; Kim, Yong-Chan ; Park, Jae-Jung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 105~112
DOI : 10.3795/KSME-B.2011.35.2.105
The objective of this study is to predict the heat-transfer performance of a spirally coiled circular fin-tube evaporator in which either R134a or R600a was used; this heat-transfer performance was predicted by varying the mass flow rate, inlet air temperature, air flow rate, and tube thickness. Mean deviation for the analytical model from the measured data was
. Simulation results revealed that at a given mass flow rate, the heat-transfer rate of the evaporator using R600a was higher than that usingR134a because the enthalpy of the former is higher than that of the latter at the given conditions. The heat-transfer rate of both refrigerants increased with an increase in the air flow rate and inlet air temperature but decreased with an increase in the tube thickness.
An Experimental Study of Transient Hot-wire Sensor Module for Measuring Thermal Diffusivity of Nanofluids
Lee, Shin-Pyo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 113~120
DOI : 10.3795/KSME-B.2011.35.2.113
A technique for measuring the thermal diffusivity of nanofluids is proposed in this study. In theory, it has been well known that the transient hot-wire method can be used to measure the thermal conductivity and diffusivity of fluids simultaneously. However, when traditional methods were employed, the accuracy of the calculated thermal conductivity was considerably higher than that of diffusivity. The proposed method has two advantages for practical use: it only needs a simple data-conversion process for calculating the diffusivity, and it can skip the tedious calibration process involved in the case of a wire sensor. A validation experiment for the new system has been performed with the basic fluids, and the comparison experiment to compare the change in diffusivity of the base oil and the change in diffusivity of the nano oil has been carried out. It is expected that the present system will provide numerous methods for investigating the variation in the thermal properties other than thermal conductivity.
Study on the Optimal Injection Condition for HC-LNT Catalyst System for Diesel Engines with a Gasoline PFI Type Injector
Oh, Jung-Mo ; Mun, Woong-Ki ; Kim, Ki-Bum ; Lee, Jin-Ha ; Lee, Ki-Hyung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 121~127
DOI : 10.3795/KSME-B.2011.35.2.121
NOx (Nitrogen Oxide) reduction system periodically needs a rich or stoichiometric operating condition to reduce NOx. A new method that optimizes the control of external HC injection into a diesel exhaust pipe for HC-type LNT (Lean NOx Trap) catalyst system has been developed. In this paper, these catalysts are called HC-LNT catalysts. The concentration and amount of HC can be controlled by controlling the external injection. In this study, we investigated the relationship between the spray behavior of hydrocarbons injected into the transparent exhaust pipe and NOx reduction characteristics. From the results of this experiment, we obtained useful information about the optimum injection and position of HC injector to the exhaust pipe. Further, we obtained useful information about the optimal injection condition for an HC-LNT catalyst system with a gasoline PFI (port fuel injection) typeinjector.
Ice Formation on the Outer Surface of a Vertical Tube with Inside Refrigerant Boiling
Nguyen, Minh Phu ; Lee, Geun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 129~135
DOI : 10.3795/KSME-B.2011.35.2.129
An ice-making model has been developed and analyzed in this study. The effects of the following on the ice formation on the outer surface of a tube in which a refrigerant flows and boils are numerically investigated: thermal resistance of the refrigerant and thermal resistance of the ice formed on the outer surface of the tube. The ice thickness and related variables are analyzed in the case of the refrigerants R22 and R134a by using the expressions for phase-change heat transfer and boiling heat transfer coefficient. Vapor qualities of the refrigerants range from 0 to 0.8. As a result, up to the first 30 min, the internal convection resistance is higher than the thermal resistance of the ice on the external surface of the tube. However, after about 30 min, the thermal resistance of the ice increases remarkably due to the increase in the ice thickness. Thus, the heat flux to the refrigerant decreases, and further, the refrigerant quality and the boiling heat transfer coefficient also decrease. As the heat transfer coefficient of R22 is higher than that of R134a, the mass of the ice formed when R22 is used is higher than that formed when R134a is used.
Combustion and Emission Characteristics of 4 Cylinder Common-Rail DI Diesel Engine with Biodiesel Blended Fuel
Lee, Dong-Gon ; Roh, Hyun-Gu ; Choi, Seuk-Cheun ; Lee, Chang-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 137~143
DOI : 10.3795/KSME-B.2011.35.2.137
This paper describes the effects of biodiesel blended fuel on the engine combustion and emission characteristics in a four cylinder CRDI(Common-rail direct injection) diesel engine. In this work, the biodiesel-diesel blended fuel(20% of biodiesel and 80% of ULSD(ultra low sulfur diesel) by volume ratio, BD20) and ULSD fuel are used under the various injection pressures and engine speeds. The experimental results of BD20 and ULSD fuel show that NOx emissions were increased and soot emissions were decreased with the increase of injection pressure. In particular, NOx emissions were slightly increased for the BD20 fuel, however, soot emissions were significantly reduced compared to the ULSD fuel. When the engine speed is increased from 1000rpm to 2000rpm, NOx emissions are decreased at all tested conditions, and soot emissions are largely increased at lower injection pressure.
A Numerical Study of the Effects of Heat Transfer and Fluid Flow on Tube Insertion Length in Computer-Cooling Radiators
Choi, Jin-Tae ; Kwon, Oh-Kyung ; Yun, Jae-Ho ; Kim, Yong-Chan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 145~152
DOI : 10.3795/KSME-B.2011.35.2.145
The performance of flat-tube radiators with louvered fins was numerically investigated for different tube insertion lengths. The results of numerical analysis using CFX-11 were compared with experimental results. In this study, three types of flat-tube radiators with louvered fins were considered. An experiment was conducted to validate the numerical results. Flow rate ratio (FR) and Stotal were introduced to understand the uniformity of flow distribution easily. The results of numerical analysis revealed that the heat transfer rate and pressure drop increased as the mass flow rate increased. Further, the results showed that the heat transfer rate of sample 3 with h/D = 0.5 was higher than that of the other samples. The pressure drop increased as the insertion length toward the header part increased, and the pressure drop in the case of sample 3 appeared to be the highest. The factor Stotal showed that the uniformity of the flow distribution in the case of sample 1 with h/D = 0 was higher than that in the case of the other samples.
Study of Characteristics of Assist Gas in Laser Machining Using Flow Visualization Techniques
Son, Sang-Hyuk ; Lee, Yeol ; Min, Seong-Kyu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 153~160
DOI : 10.3795/KSME-B.2011.35.2.153
The characteristics of supersonic coaxial/off-axis jet impingements on a slanted kerf surface were experimentally studied, to investigate the role of the assist gas that removes molten materials from cut zone formed by laser machining. In this parametric study, hundreds of high-resolution schlieren images were obtained for various gas pressures, distances between nozzle exit and kerf surface, kerf widths, and alignments of off-axis nozzle. It was noticed that simply increasing the assist gas pressure was not effective in eliminating the flow separation that occurs downstream of the kerf surface. However, it was also observed that by increasing the kerf width and utilizing off-axis nozzles, the separation of the assist gas on the kerf surface can be weakened. The effect of the distance between the nozzle exit and the kerf surface on the characteristics of separation occurring on the kerf surface was found to be lower in the case of supersonic nozzles than that in the case of sonic nozzles.
Numerical Study on the Performance Assessment for Defrost and De-Icing Modes
Kim, Yoon-Kee ; Yang, Jang-Sik ; Kim, Kyung-Chun ; Ji, Ho-Seong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 161~168
DOI : 10.3795/KSME-B.2011.35.2.161
The heating, ventilating, air conditioning (HVAC) system is a very important part of an automotive vehicle: it controls the microclimate inside the passenger's compartment and removes the frost or mist that is produced in cold/rainy weather. In this study, the numerical analysis of the defrost duct in an HVAC system and the de-icing pattern is carried out using commercial CFX-code. The mass flow distribution and flow structure at the outlet of the defrost duct satisfied the duct design specification. For analyzing the de-icing pattern, additional grid generation of solid domain of ice and glass is pre-defined for conductive heat transfer. The flow structure near the windshield, streakline, and temperature fields clearly indicate that the de-icing capacity of the given defrost duct configuration is excellent and that it can be operated in a stable manner. In this paper, the unsteady changes in temperature, water volume fraction, and static enthalpy at four monitoring points are discussed.
Numerical Investigation of Pollutant Dispersion in a Turbulent Boundary Layer by Using Lattice Boltzmann-Subgrid Model
Shin, Myung-Seob ; Byun, Sung-Jun ; Kim, Joon-Hyung ; Yoon, Joon-Yong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 169~178
DOI : 10.3795/KSME-B.2011.35.2.169
The dispersion of a pollutant in a turbulent boundary layer has been described in this study by using a two-dimensional lattice Boltzmann method (LBM) and the Smagorinsky sub-grid-scale (SGS) model. The scalar transport equation corresponding to the pollutant concentration is adopted; the pollutant is considered to be in a continuous phase. The pollutant source is classified as ground-level source (GLS) and elevated-point source (ES). Air velocity and particle concentration profile for the pollutant are compared with the respective results and profiles obtained in the experiments of Fackrell and Robins (1982) and Raupach and Legg (1983). The numerical results obtained in this study, i.e., the simulation and the experimental data for the mean flow velocity profiles and the pollutant concentration profiles, are in good agreement with each other.
Effects of Hydrocarbon Addition on Cellular Instabilities in Expanding Syngas-Air Spherical Premixed Flames
Vu, Tran Manh ; Song, Won-Sik ; Park, Jeong ; Kwon, Oh-Boong ; Bae, Dae-Seok ; Yun, Jin-Han ; Keel, Sang-In ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 179~188
DOI : 10.3795/KSME-B.2011.35.2.179
Experiments were conducted in a constant-pressure combustion chamber to investigate the effects of hydrocarbon addition on cellular instabilities of syngas-air flames. The measured laminar burning velocities were compared with the predicted results computed using reliable kinetic mechanisms with detailed transport and chemistry. The cellular instabilities that included hydrodynamic and diffusional-thermal instabilities of the hydrocarbon-added syngas-air flames were identified and evaluated. Further, experimentally measured critical Peclet numbers for fuel-lean flames were compared with the predicted results. Experimental results showed that the laminar burning velocities decreased significantly with an increase in the amount of hydrocarbon added in the reactant mixtures. With addition of propane and butane, the propensity for cell formation was significantly diminished whereas the cellular instabilities for methane-added syngas-air flames were not suppressed.
Assessment of Performance of Motor System for City Bus
Lee, Yoon-Ki ; Myong, Kwang-Jae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 189~196
DOI : 10.3795/KSME-B.2011.35.2.189
Recently, research and development of a hybrid system for passenger cars as well as for heavy-duty vehicles has become more intensive. An electric powertrain system using an electric motor can replace conventional gasoline and diesel engines. The electric motor has a higher efficiency, better acceleration performance, and is more comfortable than conventional powertrain systems; however, new methods for assessing power performance and energy convergence efficiency have to be investigated because the characteristics of an electric motor are entirely different from those of an internal combustion engine (ICE). In this study, an experiment was carried out on a motor (PMSM: Permanent Magnet Synchronous Motor) test bench. One simple driving mode and four other driving modes identified from real-world driving data of a city bus were selected to perform the experiment on the motor test bench. Then, methods for assessing the acceleration performance, energy convergence efficiency, regenerative effect, etc., were investigated. It was found that the energy efficiency of PMSM was about 90% and that 40% of demand energy was regenerated.
Experimental Study on Peak-Pressure Variation Due to Compression by Using RCM
Kim, Hye-Min ; Kim, Hak-Young ; Baek, Seung-Wook ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 197~204
DOI : 10.3795/KSME-B.2011.35.2.197
RCM is used to clarify the complex phenomena of engine combustion. In order to describe engine combustion, several significant experimental studies are considered. Prediction of the peak pressure is very important since it has a significant influence on engine combustion. In addition, peak-temperature variation can be calculated from the measured peak pressure by using the fundamental thermodynamic relation. When the RCM is in operation, heat transfer occurs through the cylinder wall. Because of this phenomenon, it is difficult to determine the peak pressure without employing the case by case experimental method. The goal of this study is to evaluate the peak pressure analytically. We conduct an experiment to confirm the relationship between the peak pressure and some parameters. Using the results of the peak pressure variation experiment, we develop a general equation that be used to calculate the peak pressure as a function of operation time and compression ratio.
Characteristics of Flow-Induced Noise in the Suction Nozzle of a Vacuum Cleaner with a Double-Blade Fan
Park, I-Sun ; Sohn, Chae-Hoon ; Oh, Jang-Keun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 205~213
DOI : 10.3795/KSME-B.2011.35.2.205
The characteristics of noise generation in the suction nozzle of a vacuum cleaner are analyzed numerically and experimentally. First, the flow resistance induced by each element in the suction nozzle of a vacuum cleaner with a double-blade rotary fan is investigated numerically and its relation with flow-induced noise and suction performance is examined in an anechoic room. The flow resistance and vorticity in the suction nozzle are calculated, and it is found that they are closely related to flow-induced noise and that the upper limit of noise reduction is only 4 dBA. This upper limit can be achieved by changing the design of the brush nozzle. Two methods for noise reduction by enlargement of flow-inlet area and by optimization of the number of blades are tested. Finally, the effects of each method are verified experimentally.
Heat Transfer Characteristics of 0.5 t/h Class Non-Furnace Boiler with a Metal Fiber Burner
Ahn, Joon ; Kim, Jong-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 35, issue 2, 2011, Pages 215~220
DOI : 10.3795/KSME-B.2011.35.2.215
A 0.5 t/h class non-furnace boiler has been developed with the aim of achieving a high efficiency and compactness. A metal fiber burner has been adopted so that a stable flame can be obtained. The tube banks are installed downstream of the burner. Bare tubes are used upstream, while finned tubes are installed downstream. The heat-transfer characteristics of the non-furnace boiler have been studies on the basis of the results of the numerical simulation as well as those of the experiment. Important design parameters such as the bulk temperature along the streamwise direction and the temperature of the fin tips have been evaluated using the CFD results and compared with the experimental data and the empirical correlations typically used for the design of the boiler.