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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
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Volume & Issues
Volume 37, Issue 12 - Dec 2013
Volume 37, Issue 11 - Nov 2013
Volume 37, Issue 10 - Oct 2013
Volume 37, Issue 9 - Sep 2013
Volume 37, Issue 8 - Aug 2013
Volume 37, Issue 7 - Jul 2013
Volume 37, Issue 6 - Jun 2013
Volume 37, Issue 5 - May 2013
Volume 37, Issue 4 - Apr 2013
Volume 37, Issue 3 - Mar 2013
Volume 37, Issue 2 - Feb 2013
Volume 37, Issue 1 - Jan 2013
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Numerical Investigation of Urea Freezing and Melting Characteristics Using Coolant Heater
Lee, Seung Yeop ; Kim, Nam Il ; Park, Yun Beom ; Kim, Man Young ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 717~724
DOI : 10.3795/KSME-B.2013.37.8.717
Urea-SCR technology is known as one of the powerful NOx reduction systems for vehicles as well as stationary applications. For its consistent and reliable operation in vehicle applications, however, the freezing and melting of the urea solution in cold environments have to be resolved. In this study, therefore, a numerical study of three-dimensional unsteady problems was analyzed to understand the urea freezing and heating phenomena and heat transfer characteristics in terms of urea liquid volume fraction, temperature profiles, and phase change behavior in urea solutions with time by using the commercial software Fluent 6.3. As a result, it was found that the freezing phenomenon proceeds with a phase change from the tank wall to the center, whereas the melting phenomenon occurs faster in the upper part of the storage tank by natural convection and in the adjacent part of the coolant pipe than in other parts. Furthermore, approximately 190 s were required to obtain 1L of urea solution using a 4-coiled coolant heater under conditions of
and 200 L/h.
Measuring Convective Heat Transfer Coefficient of Nanofluids Considering Effect of Film Temperature Change over Heated Fine Wire
Lee, Shinpyo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 725~732
DOI : 10.3795/KSME-B.2013.37.8.725
This study examined the convective heat transfer characteristics of nanofluids flowing over a heated fine wire. Convective heat transfer coefficients were measured for four different nano-engine-oil samples under three different temperature boundary conditions, i.e., both or either variation of wire and fluid temperature and constant film temperature. Experimental investigations that the increase in the convective heat transfer coefficients of nanofluids in the internal pipe flow often exceeded the increase in thermal conductivity were recently published; however, the current study did not confirm these results. Analyzing the behavior of the convective heat transfer coefficient under various temperature conditions was a useful tool to explain the relation between the thermal conductivity and the boundary layer thickness of nanofluids.
Combustion Characteristics of Landfill Gas in Constant Volume Combustion Chamber for Large Displacement Volume Engine (I) - Fundamental Characteristics -
Ohm, Inyong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 733~741
DOI : 10.3795/KSME-B.2013.37.8.733
This is the first paper on the combustion characteristics of landfill gas in a constant volume combustion chamber for a large displacement volume commercial engine, and it discusses the fundamental characteristics of fuel from the viewpoint of thermochemistry and thermodynamics and compares these results with experimental ones. The results show that the final pressures obtained from theoretical analysis vary under the same heating value owing to the change in the constant volume specific heat owing to the difference in the burned gas composition according to the fuel gas compositions; furthermore, the stoichiometric ratios and trends of analytical and experimental pressures coincide very well, although some minor differences are observed between the two. The root cause of the difference is the heat transfer, which changes the specific heat and lowers the temperature considerably, in the real combustion process. In addition, the large chamber volume and ignition position promote the heat transfer to the wall. Finally, the fuel conversion efficiency increases as the methane mol fraction decreases, and it is maximum when the stoichiometric ratio ranges from 0.8 to 0.9. These increases due to the composition and stoichiometric ratio could sufficiently compensate the decrease due to the specific heat ratio drop, LFG might be more advantageous than pure methane in a real engine.
Combustion Characteristics of Landfill Gas in Constant Volume Combustion Chamber for Large Displacement Volume Engine (II) - Combustion Analysis -
Kwon, Soon Tae ; Park, Chanjun ; Ohm, Inyong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 743~752
DOI : 10.3795/KSME-B.2013.37.8.743
This is the second paper on the combustion characteristics of landfill gas in a constant volume combustion chamber for a large displacement volume commercial engine, and it discusses the combustion process on the basis of pressure measurements. The results show that the bimodal peak pressure phenomenon, which is caused by the interaction of the heat release and the heat transfer, is more apparent as the mixtures are more favorable to combustion, and the magnitudes of the pressures depend on the unburned fraction. In addition, there exist four main inflection points during heat release owing to variations in the heat transfer area related to flame propagation from the ignition point. Furthermore, the number of inflection points increases as the mixture quality worsens because of the extended burn duration. Consequently, the sophisticated interactions between the heat transfer area changing pattern due to flame propagation and transfer duration might cause very peculiar heat release patterns.
Numerical Analysis of New Proposals to Enhance Heat Transfer in MCFC'S Preconverter
Sohn, Chang Hyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 753~758
DOI : 10.3795/KSME-B.2013.37.8.753
In this study, two proposals for the wall heating preconverter of an MCFC are numerically studied to resolve hot temperature generation near the wall by the low thermal conductivity of the catalyst. The numerical results show that the inserted porous cupper plates on the catalyst evidently improve heat transfer and realize more uniform reforming in the preconverter. The calculated results for the preconverter with a circumference empty space of catalyst located at center, 1/2 and 4/5 from center line are compared. The circumference empty space located at 1/2 position shows better results than other cases, but the positive effect on the uniform reforming process is less than in the case of inserted cupper porous plates on the catalyst.
Experimental Study of Pressure Drop in Compressible Fluid through Porous Media
Seo, Min Kyo ; Kim, Do Hun ; Seo, Chan Woo ; Lee, Seoung Youn ; Jang, Seok Pil ; Koo, Jaye ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 759~765
DOI : 10.3795/KSME-B.2013.37.8.759
This study proposes the characteristics of the pressure drop in a compressible fluid through porous media for application to a porous injector in a liquid rocket engine in order to improve the uniformity of the drop size distribution and the mixing performance of shear coaxial injectors. The fluid through the porous media is a Non-Darcy flow that shows a Nonlinear relation between the pressure drop and the velocity at high speed and high mass flow rate. The pressure drop of the Non-Darcy flow can be derived using the Forchheimer equation that includes the losses of viscous and inertia resistance. The permeability and Ergun coefficient represented as a function of the pressure drop and pore size can be applied to the porous injector, where the fluid through the porous media is compressible. A generalized correlation between the pressure drop in relation to the pore size was derived.
Variation of Porosity and Gas Permeability of Gas Diffusion Layers Under Compression
Lee, Yongtaek ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 767~773
DOI : 10.3795/KSME-B.2013.37.8.767
This study suggested the variations of porosity and gas permeability of gas diffusion layers (GDLs), which are easily deformed among the components of a highly compressed PEMFC stack. The volume change owing to compression was measured experimentally, and the variations in the porosity and gas permeability were estimated using correlations published in previous literature. The effect of polytetrafluoroethylene (PTFE) which is added to the GDLs to enhance water discharge was investigated on the variations of porosity and gas permeability. The gas permeability which strongly affects the mass transport through GDL, decreases sharply with increasing compression when the GDL has high PTFE loading. As a result, the mass transport through the pore network of GDL can be changed considerably according to the PTFE loading even with the same clamping force. The accuracy of modeling of transport phenomena through GDL can be improved due to the enhanced correlations developed based on the results of this study.
Thermal Analysis of Lithium-ion Cell Using Equivalent Properties and Lumped Capacitance Method
Lee, Hee Won ; Park, Il Seouk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 775~780
DOI : 10.3795/KSME-B.2013.37.8.775
In general, the battery module of an electric vehicle (EV) consists of lithium-ion cells. A lithium-ion battery is a secondary rechargeable battery, and it consists of numerous stacked plates that serve as electrodes and separators. Owing to these microstructural features, its numerical analysis is very expensive. Therefore, this study aims to present a simplified thermal analysis model using equivalent thermal properties, and we compare the experimental results with numerical results for 185.3Ah and 20Ah cells. Furthermore, we show the thermal behavior of cells without the finite element method (FEM) or finite volume method (FVM) by adopting the lumped capacitance method (LCM).
Temperature Prediction of Cylinder Components in Medium-Speed Diesel Engine Using Conjugate Heat Transfer Analysis
Choi, Seong Wook ; Yoon, Wook Hyoen ; Park, Jong Il ; Kang, Jeong Min ; Park, Hyun Joong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 781~788
DOI : 10.3795/KSME-B.2013.37.8.781
Predicting the engine component temperature is a basic step to conduct structural safety evaluation in medium-speed diesel engine design. Recent trends such as increasing power density and performance necessitate more effective thermal management of the engine for achieving the desired durability and reliability. In addition, the local temperatures of several engine components must be maintained in the proper range to avoid problems such as low- or high-temperature corrosion. Therefore, it is very important to predict the temperature distribution of each engine part accurately in the design stage. In this study, the temperature of an engine component is calculated by using steady-state conjugate heat transfer analysis. A proper approach to determine the thermal load distribution on the thermal boundary area is suggested by using 1D engine system analysis, 3D transient CFD results, and previous experimental data from another developed engine model. A Hyundai HiMSEN engine having 250-mm bore size was chosen to validate the analysis procedure. The predicted results showed a reasonable agreement with experimental results.
Development of Programs to Analyze Mechanical Load Data of Wind Turbine Generator Systems and Case Studies on Simulation Data
Bang, Je-Sung ; Han, Jeong-Woo ; Gil, Kyehwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 37, issue 8, 2013, Pages 789~798
DOI : 10.3795/KSME-B.2013.37.8.789
The procedures and relevant programs developed for analyzing mechanical load data of wind turbine generator systems, which are obtained through type certification tests, are verified. The following issues according to IEC 61400-13 are covered in the developed programs: data validation, time series analysis, summary load statistics, generation of fatigue load spectra, and estimation of equivalent loads. A capture matrix for normal power production is generated to determine whether the collected data sets are sufficient to carry out fatigue analysis. Fatigue load spectra are obtained through the rainflow counting method using 50 load ranges; finally, equivalent loads are calculated using different S-N curve slopes, m, according to the relevant materials. Case studies are performed using aero-elastic simulation data of the NREL 5 MW baseline wind turbine with a monopile foundation.