• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(3)
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• pp.265-270
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• 1996

The temperature distribution in the pellet was obtained from beginning the general heat conduction equation. The thermal conductivity of pellet used the SIMFUEL data that made clear the effect of burnup on the thermal conductivity degradation. Since the pellet rim acts as the thermal barrier to heat flow. the pellet was subdivided into several rings in which the outer ring was adjusted to play almost the same role as the rim. The local burup in each ring except the outer ring was calculated from the power depression factor based on FASER results. whereas the rim burnup at the outer ring was achieved by the pellet averaged burnup based on the empirical relation. The rim changed to the equivalent Xe film so the predicted temperature shooed the thermal jump across the rim. The observed temperature profiles depended on linear heat generation rate. fuel burnup. and power depression factor. The thermal conductivity degradation modelling can be applied to the fuel performance code to high burnup fuel,

• Progress in Superconductivity
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• 제3권2호
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• pp.247-251
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• 2002

In general, the bubbling, generated during the fabrication of the tapes, breaks the superconducting filament, and critical current of the tapes will be decreased. Heat-treatment schemes of Bi-2223/Ag HTS tapes were modified, such as pre-annealing of multi-stacked billet, 2-step main sintering and ramp rate etc. The generation of bubbling was drastically decreased from 20 bubbles/m to 0 ~ 1 bubble/m by the modified heat-treatment. Therefore, the value of critical current of the tapes without bubbling was increased almost twice higher than that of already existing tapes. Critical current up to 42 A in 40 m length Bi-22231Ag tapes have been measured at 77K, self-field, 1$mutextrm{V}$/cm criterion. It could be confirmed that elimination of bubbling is effective to maintain the superconducting property along the tape length.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.726-731
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• 2001

A thermal design software is developed for the heat recovery steam generator(HRSG) of combined cogeneration systems. The heat transfer is calculated by using the element method to account for the varying thermal properties across the heat transfer elements. The circulation balance is computed for the evaporator to accurately estimate the steam generation rate and to check the proper circulation of the boiler water through the tubes. The software developed can be used to simulate HRSG systems with various combinations of auxiliary burner, wall superheater, superheater, reheater, evaporator, and economizer. Systems with several different combinations of the system components are successfully tested. And it is concluded that the developed software can be used for the design of heat recovery steam generators with various combinations of heat transfer components.

• Nuclear Engineering and Technology
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• 제33권2호
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• pp.241-253
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• 2001

Under severe accidents, the pressure and temperature response has an important role for the integrity of a nuclear power plant containment. The history of the pressure and temperature is characterized by the amount and state of steam/air mixture in a containment. Recently, the heat transfer rate to the structure surface is supposed to be increased by the wavy interface formed on condensate film. However, in the calculation by using CONTAIN code, the condensation heat transfer on a containment wall is calculated by assuming the smooth interface and has a tendency to be underestimated for safety. In order to obtain the best- estimate heat transfer calculation, we investigated the condensation heat transfer model in CONTAIN 1.2 code and adopted the new forced convection correlation which is considering wavy interface. By using the film tracking model in CONTAIN 1.2 code, the condensate film is treated to consider the effect of wavy interface. And also, it was carried out to investigate the effect of the different cell modelings - 5-cell and 10-cell modeling - for KNGR(Korean Next Generation Reactor) containment phenomena during a severe accident. The effect of wavy interface on condensate film appears to cause the decrease of peak temperature and pressure response . In order to obtain more adequate results, the proper cell modeling was required to consider the proper flow of steam/air mixture.

• 한국태양에너지학회 논문집
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• 제30권3호
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• pp.33-38
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• 2010

The evaporative desalination system using solar thermal energy would be the efficient and attractive method to get fresh water from brine due to low carbon dioxide generation. In this research the solar desalination system as a heating source of refrigerant R123 in the evaporator was considered. The circulation of refrigerant in the evaporator can reduce the energy consumption of the system, because of using the latent heat of the refrigerant 123 instead of the sensible heat of present hot water. The system was comprised of the single-stage fresh water production unit on the capacity of 1ton/day with shell and tube type evaporator, heaters instead of solar collector to supply the proper heat to refrigerant, and refrigerant and brine circulation systems. Various operating flowrate and temperature ranges were varied in the experiments to get the optimum design data. The results showed that the optimum flow rate of brine feed rate to evaporator was 1.2Liter/min, and the yield of fresh water was increased as higher temperature of feed brine. It was confirmed that the circulation flowrate of heating source of refrigerant was decrease of one fifth of the present warm water system, and very efficient system for solar desalination.

• 동력기계공학회지
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• 제21권3호
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• pp.30-36
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• 2017

Carbon fiber shows excellent heat generation value and thermal efficiency comparing with the metallic materials because of its far infrared-rays and radiant heat. So, high performance and economic steam boiler system for the industry can be manufactured by using the carbon fiber heater. The far infrared ray radiation rate was more than 90 % of carbon fiber. Steam boiler system with carbon fiber heater in this study is made up of heating section. In the proof test of steam boiler, the aimed temperature and dwelling time were at $500^{\circ}C$ for 8,000 hours, $600^{\circ}C$-3,000 hours, and $700^{\circ}C$-1,000 hours. The temperature rise rate of steam boiler with carbon fiber heater was about 40% faster than that of the conventional boiler.

• Nuclear Engineering and Technology
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• 제38권4호
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• pp.343-352
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• 2006

Convenient analytical tools for evaluation of the aperiodic and the fluctuating instabilities of the passive residual heat removal system (PRHRS) of an integral reactor are developed and results are discussed from the viewpoint of the system design. First, a static model for the aperiodic instability using the system hydraulic loss relation and the downcomer feedwater heating equations is developed. The calculated hydraulic relation between the pressure drop and the feedwater flow rate shows that several static states can exist with various numbers of water-mode feedwater module pipes. It is shown that the most probable state can exist by basic physical reasoning, that there is no flow rate through the steam-mode feedwater module pipes. Second, a dynamic model for the fluctuating instability due to steam generation retardation in the steam generator and the dynamic interaction of two compressible volumes, that is, the steam volume of the main steam pipe lines and the gas volume of the compensating tank is formulated and the D-decomposition method is applied after linearization of the governing equations. The results show that the PRHRS becomes stabilized with a smaller volume compensating tank, a larger volume steam space and higher hydraulic resistance of the path $a_{ct}$. Increasing the operating steam pressure has a stabilizing effect. The analytical model and the results obtained from this study will be utilized for PRHRS performance improvement.

• 한국건설순환자원학회논문집
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• 제3권3호
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• pp.237-243
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• 2015

본 연구에서는 알칼리 활성화 슬래그 결합재의 반응성을 정량적으로 살펴보기 위해 미소수화열을 분석을 수행하였다. 알칼리 활성화 슬래그 결합재의 반응성 및 작업성 확보를 위해 다양한 알칼리 자극제의 종류 및 농도에 대해서 실험을 수행하였다. 알칼리 자극제 및 $SO_3$ 질량비를 변화하면서 미소수화열을 측정하였으며, 응결시간 제어를 위해 sodium tripolyphosphate ($Na_2P_3O_{10}$)와 hydrated sodium borate ($Na_2B_4O_710H_2O$)를 적용하였다. 그 결과, 알칼리 활성화 슬래그 결합재는 알칼리 활성에 의해 calcium silicate hydrate(C-S-H)를 촉진하는데 4~5% 농도의 알칼리가 필요한 것으로 나타났으며, $SO_3$ 함량이 높아질수록 누적 발열량이 작아지면서 전반적으로 발열이 지연되는 것으로 나타났다. 또한, 응결 지연제로서 hydrated sodium borate를 사용하였을 경우 발열을 억제하여 지연된 효과를 나타내며, 전체적인 누적 발열을 지연시키는 효과를 보이는 것을 확인할 수 있었다.

• 한국화재소방학회논문지
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• 제33권2호
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• pp.1-8
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• 2019

본 연구는 화학공장에서 원료 및 제품으로 사용되는 Butadiene popcorn polymer에 자연발화가 일어날 수 있는지를 평가하기 위하여 성분분석, 열중량분석, 열안정성분석, 자연발화점 측정 및 가속속도열량측정분석을 실시하였다. 분석결과 성분분석에서는 다양한 종류의 가연성 성분이 측정되었고, 열중량 분석을 통해 공기중에서 95.6%, 질소중에서 89.2%의 중량감소가 측정되었다. 열안정성분석 결과, 공기분위기에서 $88^{\circ}C$에서 발열이 시작되었으며, 자연발화점 부근($220^{\circ}C$)에서는 발열속도가 급격히 증가하였다. 질소분위기에서 $70^{\circ}C$ 부근에서 발열이 시작되었으며, $450^{\circ}C$까지 두 단계의 분리된 발열 Peak값이 관측되었다. 가속속도열량측정결과 발열현상은 나타나지 않았으며, 자연발화점을 분석한 결과 최저발화온도는 $211.7^{\circ}C$ 였다. 열안정성 평가에서 산출된 결과를 토대로 반응열에 의한 Column의 열적변형을 유발시킬 수 있는 가능성은 충분한 것으로 판단되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.113.1-113.1
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• 2010

IGCC(Integrated Coal Gasification and Combined Cycle) plants can be among the most advanced and environmental systems for electric energy generation from various feed stocks and is becoming more and more popular in new power generation fields. In this work, the performance of IGCC plants employing Shell gasification technology and a GE 7FB gas turbine engine was simulated using IPSEpro open-equation modeling environment for different operating conditions. Performance analyses and comparisons of all operating cases were performed based on the design cases. Discussions were focused on gas composition, syngas production rate and overall performance. The validation of key steady-state performance values calculated from the process models were compared with values from the provided heat and material balances for Shell coal gasification technology. The key values included in the validation included the inlet coal flow rate; the mass flow rate, heating value, and composition of major gas species (CO, H2, CH4, H2O, CO2, H2S, N2, Ar) for the syngas exiting the gasifier island; and the HP and MP steam flows exiting the gasifier island.