• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.250-253
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• 2008

최근 석탄 가스화 기술은 화석연료인 석탄을 기존의 공해물질 발생을 90%이상 줄이면서 고효율로 활용할 수 있는 방법으로 각광받고 있다. 본 연구는 당 센터에서 보유하고 있는 습식 석탄 가스화기의 성능 향상을 위하여 버너의 형태에 따른 미립화 특성을 파악하였으며, 가스화기의 버너로 적용하여 가스화 특성 실험을 실시하였다. 미립화 특성을 파악하기 위하여 개발되어진 3가지 형태의 버너를 Cold Test장치를 이용하여 $O_2$/Fuel Ratio 및 버너의 내부 혼합 방식, 분사각도에 따른 미립화 특성을 관찰하였으며, 입도 분석은 심파텍사의 입도 분석기를 이용하여 측정하였다. 실험 결과 이중혼합식 버너가 미립화 특성이 가장 우수하게 나타났으며, 외부혼합식 버너와 환형 버너의 경우 비슷한 미립화 특성을 나타내었다. 가스화기에 적용하여 실험한 결과 미립화 특성이 우수하게 나타나는 경우 가스화 특성 또한 우수하게 나타남을 확인하였다.

• Journal of the Korean Society for Heat Treatment
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• v.6 no.4
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• pp.243-248
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• 1993

A Circulating Fluidized-Bed (CFB) with an internal nozzle and a partition wall was proposed. The technique of fluidization is related to operations first used commercially in the fields of metallurgical and mechanical engineering such as the heat treatment of metals and power station combustors. In the modified CFB, an internal nozzle and a partition wall were additionally set in the main bed. This cold mode CFB apparatus made of acrylic resin; the main bed is 1,500mm high and 100mm in the inner diameter, the internal nozzle is 130mm high and 10mm in the inner diameter, and the partition wall is 7mm thick and 100mm in the diameter. Glass beads of $89{\mu}m$ in the mean diameter were employed as bed materials.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.63-67
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• 2002

In this study, the performance of the Stirling type orifice Pulse tube refrigerator (OPTR) with a linear compressor was investigated by experiment. The dynamic pressures at three points and a temperature at the cold heat exchanger are measured to explore the dependency of the orifice on the performance of the OPTR. The experimental results show that the opening of the orifice has significant effects on the no load temperature and cool down characteristics. The Pressure amplitude in Pulse tube decrease as the opening of the orifice increase, but the mass flow rate through the orifice and the electric input Power to the compressor increase. The results show that the operating frequency and charging Pressure does not affect on the no load temperature. The pressure amplitude in pulse tube decrease as the operating frequency increase or the charging Pressure decreased.

• Nuclear Engineering and Technology
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• v.29 no.3
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• pp.186-195
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• 1997

When asymmetric thermal-hydraulic conditions occur between cold legs, the core inlet temperature will be nonuniform if the coolant is not mixed perfectly in the lower plenum. These uneven core inlet conditions may induce the change in core power distribution. Thus realistic prediction of thermal mixing is important in such abnormal conditions. In this study, reactor internals, which are scaled down as to conserve the flow area ratio, are set up in the model of KORI Unit 1 with the scaling factor of 1/710 by volume and coolant temperatures are measured beneath the lower core plate. Based on experimental results, the ability of COMMIX-1B code to simulate the coolant mixing phenomena in the lower plenum is estimated. The results show that complete mixing never occurs in any conditions and the mixing pattern is characterized according to the plant type.

• Journal of the Semiconductor & Display Technology
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• v.6 no.3
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• pp.47-53
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• 2007

Ultra thin Si p-n junctions shallower than $300{\AA}$ were fabricated and biased to the avalanche regime. The ultra thin junctions were fabricated to be parallel to the surface and exposed to the surface without $SiO_2$ layer. Those junctions emitted white light and electrons when junctions were biased in the avalanche breakdown regime. Therefore, we could observe the avalanche breakdown region visually. We could also observe the influence of electric field to the current flow visually by observing the white light which correspond to the avalanche breakdown region. Arrayed diodes emit light and electrons uniformly at the diode area. But, the reverse leakage current were larger than those of ordinary diodes, and the breakdown voltage were less than 10V.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.2
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• pp.122-128
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• 2006

In this paper, frosting experiments were conducted with variations of frosting parameters in order to obtain the correlations of frost properties. As a result, the local thickness, density, and surface temperature of the frost layer were presented. The dimensionless correlations for the frost thickness, frost density, frost surface temperature and heat transfer coefficient were derived as functions of dimensionless frosting parameters by using a dimensional analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.7
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• pp.468-473
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• 2010

This paper deals with approximate integral solutions to the one-dimensional model describing the charging process of stratified thermal storage tanks. Temperature is assumed to be the form of Fermi-Dirac distribution function, which can be separated to two sets of cubic polynomials for each hot and cold side of thermal boundary layers. Proposed approximate integral solutions are compared to the previous works of the approximate analytic solutions and show reasonable agreement. The approach, however, has benefits in mathematical difficulties, complicated solution form and unstable convergence of series solution founded in the previous analytic solutions. Solutions for a semi-infinite region, which have simple closed form solutions, give close agreement to those for a finite region. Thermocline thickness is obtained in closed form and shows proportional behavior to the square root of time and inverse proportional behavior to the square root of flow rate.

• 연구논문집
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• s.30
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• pp.15-23
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• 2000

In this study, develop the thermal pump using water evaporation and condensation. Vapor from heating room moves up to pumping room and press the water of pumping room. Consequently water is pumped out to water tank. Then hot vapor direct contact with cold water in condensing room after pumping process. At this time, pressure of condensing room is down to-5kPa and suck in water of tank. This pump executes self ping and good durability because of no mechanical moving parts. Thermal pump is pumped cyclic so that, this pump is not used single. Therefore thermal pump of hot water boiler used to multi-stage for stable pumping rate. As the result of performance test, the developed thermal pump proves pumping action of water evaporation/condensation. And total volume flow rate is 500liter during one hour. If three thermal pump is installed parallel, this pump can use to the hot water boiler in the 300,000kcal/h class.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.437-442
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• 1998

Film boiling is the heat transfer mechanism that can occurs when large temperature differences exist between a cold liquid and hot material. In the nuclear reactor safety analysis, film boiling has become an important issue in recent years. During severe accident, hot molten corium fall into relatively cool water, and fragment into spheres or sphere-like particles. If the steam explosion is triggered, the thermal energy of corium is converted into the mechanical energy that can threaten the integrity of reactor vessel or reactor cavity. One of the important concerns in the heat transfer analysis during pre-mixing stage is the film boiling heat transfer between the corium and water/steam two-phase flow. Until now, considerable works on film boiling heat been performed. However, there is no available correlation adequate for severe accident analysis. In this study, boiling heat transfer correlations have been developed, and their applicable ranges heat been enlarged and their prediction accuracy has been enhanced.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.8
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• pp.384-391
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• 2001

The insulation strength between contacts after current interruption to the transient recovery voltage i.e., the dielectric recovery strength should be estimated for the evaluation of the small capacitive current interruption capability. Many authors have used theoretical and semi-experimental approaches to evaluate the transient breakdown voltage after the current interruption. Moreover, an empirical equation, which is obtained from a series of tests, has been used to estimated the dielectric recovery strength. Un this paper, the theoretical method which is generated from the streamer theory has been applied to real circuit breakers in order to evaluated the interruption capability. The results of analysis have been compared with the test results and the reliability has been investigated.