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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Energy Engineering
Journal Basic Information
Journal DOI :
The Korea Society for Energy Engineering
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Volume & Issues
Volume 14, Issue 4 - Dec 2005
Volume 14, Issue 3 - Sep 2005
Volume 14, Issue 2 - Jun 2005
Volume 14, Issue 1 - Feb 2005
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The Effect of Pyrolysis Pressure on Combustion Reactivity of Coal Char
Park Ho Young ; Kim Young Ju ; Kim Tae Hyung ; Seo Sang Il ;
Journal of Energy Engineering, volume 14, issue 1, 2005, Pages 1~10
The combustion reactivity of char depending on the pyrolysis pressure was investigated with Pressurized Thermogravimetric Analyser. The amounts of volatiles released at pyrolysis pressure of 1, 8 and 15 atm were, first, measured with Alaska, Adaro and Denisovsky coals. Reactivities of chars produced at var-ious pyrolysis pressure were evaluated at atmospheric pressure and 500℃, and analysed in terms of char crystal structure, surface area, pore characteristics and chemical composition of char. Finally, the combustion reactivities of three chars were examined at pressure of 1 atm, 8 atm and 15 atm. From this study, it was recognized that the amount of volatiles released decreases with increase in pyrolysis pressure, and reaction rate of char produced at higher pyrolysis pressure was lower than that at lower pyrolysis pressure. It might be resulted from the difference in char surface area and pore characteristics rather than char crystal structure and chemical characteristics. At 15 atm, kinetic parameters of Alaska char were obtained with the grain model, and these were 56.8 KJ/mole for activation energy and 222.34 (1/min) for frequency factor.
A Theoretical Approach on the Pressure Drop in Two-phase Particle-laden Flows
Kim Seyun ; Lee Kye-Bock ;
Journal of Energy Engineering, volume 14, issue 1, 2005, Pages 11~17
The purpose of this research is to develop the model of pressure drop per unit pipe length due to the turbulence modulations in particle-laden flows which can be applied to various fluid conditions. The wake behind a particle, particle size, loading ratio and density difference between two phases of particle-laden flow was considered. The frictional pressure drop was modeled with the force balance in control volume. The numerical results show good agreements with available experimental data and the model success-fully predicted the mechanism of the pressure drop in particle-laden flows.
A Study on Cooling Characteristics of Clathrate Compound with Concentration of TMA
Kim Jin-Heung ; Chung Nak-Kyu ; Kim Chang-Oh ;
Journal of Energy Engineering, volume 14, issue 1, 2005, Pages 18~23
This study is investigated the cooling characteristics of the TMA clathrate compound including TMA (Tri-methyl-amine, (CH₃)₃N) of 20～25 wt％ as a low temperature storage material at -5℃ heat source. The results showed that as the concentration of TMA is increased, phase change temperature and specific heat are increased, but the supercooling and retention time of liquid phase are decreased. Especially, low temperature storage material containing TMA 25 wt％ has the average of phase change temperature of 5.8℃, supercooling of 8.0℃, retention time of liquid phase for 10 minutes and specific heat of 4.099 kJ/kg℃ in the cooling process. From the results of this study, TMA clathrate compound showed higher phase change temperature than water md supercooling repression effect.
Thermal Characteristics of Eire-Protection Aqueous Film Forming Foams for Various Expansion Ratios
Kim Hong-Sik ; Kim Youn-Jea ; Hwang In-Ju ;
Journal of Energy Engineering, volume 14, issue 1, 2005, Pages 24~29
In order to evaluate the performance of fire-protection foams used to protect structures from heat and fire damages, the thermal characteristics of them are experimentally investigated. This research focuses on the destruction of a fire-fighting foam subjected to heat radiation. A simple repeatable test apparatus for fire-protection foams subjected to fire radiation is developed. It involves a foam generation equipment, a fire source for heat generation, repeatable test procedures, and data acquisition techniques. Results of the experimental procedure indicated that each thermocouple within the foam responded in a similar manner and gradually to a temperature of 115℃～20℃. At this point, each trace generally rises to a temperature of approximately 90℃. The temperature gradient in the foam as time passes increases with increasing the foam expansion ratio. In addition, it is found that the temperature gradient along the foam for depth decreases with increasing the foam expansion ratio.
Local Heat Transfer Characteristics in the Wake Region of a Circular Cylinder
Chang Byong Hoon ;
Journal of Energy Engineering, volume 14, issue 1, 2005, Pages 30~36
This paper reports the experimental study of the heat transfer characteristics of the wake region behind a cylinder in cross flow. Local heat transfer coefficient was measured from the stagnation point (θ=0°) to 180°, and the variation of Nu in the axial direction along the cylinder was also studied. The results show that the heft transfer rate at the rear (θ=180°) near the duct wall can increase as much as 58% over the 2 dimensional value at the center of the duct. The heat transfer profiles in the wake region also show distinct effects of the aspect ratio and the heat transfer boundary condition.
Analysis and Improvement of Power Quality for A Fuel Cell System Based on Multi-level Converters
Kim Yoon-Ho ; Moon Hyun-Wook ; Kim Soo-Hong ; Jeong Eun-Jin ;
Journal of Energy Engineering, volume 14, issue 1, 2005, Pages 37~45
The fuel cell system is one of very useful energy sources. The system has advantages as renew-able and environmental sources. To obtain AC electricity from fuel cells, inverters are necessary. A multilevel converter is used as an inverter for a high power fuel cell system. Through harmonic analysis, it is shown that the harmonic components and THD increase while fundamental component decreases as voltage sag increases. To solve the voltage sag problems, three different approaches are investigated in this paper; installation of a boost converter at the fuel cell output, control of pulse widths, and use of ultracapacitors. The proposed three approaches are analyzed and compared using simulation and experimental results.
Determination of Incentive Level of Direct Load Control using Probabilistic Technique with Variance Reduction Technique
Jeong Yun-Won ; Park Jong-Bae ; Shin Joong-Rin ;
Journal of Energy Engineering, volume 14, issue 1, 2005, Pages 46~53
This paper presents a new approach for determining an accurate incentive levels of Direct Load Control (DLC) program using probabilistic techniques. The economic analysis of DLC resources needs to identify the hourly-by-hourly expected energy-not-served resulting from the random outage characteristics of generators as well as to reflect the availability and duration of DLC resources, which results the computational explosion. Therefore, the conventional methods are based on the scenario approaches to reduce the computation time as well as to avoid the complexity of economic studies. In this paper, we have developed a new technique based on the sequential Monte Carlo simulation to evaluate the required expected load control amount in each hour and to decide the incentive level satisfying the economic constraints. In addition, we have applied the variance reduction technique to enhance the efficiency of the simulation. To show the efficiency and effectiveness of the suggested method, the numerical studies have been performed for the modified IEEE 24-bus reliability test system.
Computational Study for the Performance of Fludic Device during LBLOCA using TRAC-M
Chon Woochong ; Lee Jae Hoon ; Lee Sang Jong ;
Journal of Energy Engineering, volume 14, issue 1, 2005, Pages 54~61
The APR1400 is an Advanced Pressurized Water Reactor with 3983 MWt power, 2×4 loops, and direct vessel injection system. The Fluidic Device (FD) is adopted to regulate the safety injection flow rate in a Safety Injection Tank (SIT) of APR1400. The performance of a newly designed fluidic Device is evaluated by analyzing a Large Break Loss-of-Coolant Accident (LBLOCA) using TRAC-M/F90, version 3.782. The analysis results show that the TRAC-M code reasonably predicts the important phenomena of blowdown, refill and reflood phases of LBLOCA. The sensitivity studies about gas/water volume changes in a SIT and K factor changes in a SI system were also done to understand the important phenomena with a Fluidic Device in APR1400.
An Experimental Study of Thermal Mixing of Steam Jet Condensation through an I-Sparser in a Quench Tank
Kim Yeon-Sik ; Jun Hyeong-Gil ; Song Chul-Hwa ;
Journal of Energy Engineering, volume 14, issue 1, 2005, Pages 62~71
An experimental study on thermal mixing of steam jet condensation through the I-Sparger of APR1400 design using B&C (Blowdown and Condensation) test facility. Due to the limit of the steam supply capability of the pressurizer, transient thermal mixing experiments were conducted. Temperature distributions in the quench tank were measured using thermocouples located at various positions. From the experimental data, local temperature variations for various locations and vertically cross-sectional temperature distributions for several times were depicted and presented. The result shows the characteristics of thermal mixing of the I-Sparger depending on the design features of the I-Sparger.