• 대한안전경영과학회지
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• 제13권2호
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• pp.61-66
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• 2011

Fire disasters have frequently happened in concrete structures, which resulted in severe structural damages and unsafety. In this case, the method which had evaluated the safety of damaged structures was often unaccepted from most of stakeholders and engineers. The objective of this study is to develope the procedure and method to be able to determine the safety. Numerical simulation was applied to produce the maximum temperature and temperature distribution. Nextly, temperature propagation analysis was performed to plot temperature gradients at each depth and location. The material strength curve versus temperature was applied to determine the safety of concrete structures damaged by fire. The maximum temperature should be calibrated considering real fire records ; magnitude, intensity, situation etc. The results shows that the selected procedure and method was applicable and practical.

• 한국산업융합학회 논문집
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• 제24권4_1호
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• pp.411-419
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• 2021

In this study, IGBT_Total_Loss and DIODE_Total_Loss were used to analyze the slope of the junction temperature for each section for temperature and duty variables in order to simply calculate the junction temperature of the power semiconductor (IGBT). As a result of the calculation, IGBT_Max_Junction_Temp and DIODE_Max_Junction_Temp form a proportional relationship with temperature for each duty. This simulation data shows that the power loss of a power semiconductor is calculated in a complex manner according to the current dependence index, voltage dependence index, and temperature coefficient. By applying the slope for each condition and section, the junction temperature of the power semiconductor can be calculated simply.

• 한국분말재료학회지
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• 제20권5호
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• pp.332-337
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• 2013

Recently, self-propagating high-temperature synthesis (SHS), related to metallic and ceramic powder interactions, has attracted huge interest from more and more researchers, because it can provide an attractive, energy-efficient approach to the synthesis of simple and complex materials. The adiabatic temperature $T_{ad}$ and apparent activation energy analysis of different thermit systems plays an important role in thermodynamic studies on combustion synthesis. After establishing and verifying a mathematic calculation program for predicting adiabatic temperatures, based on the thermodynamic theory of combustion synthesis systems, the adiabatic temperatures of the NiO/Al aluminothermic system during self-propagating high-temperature synthesis were investigated. The effect of a diluting agent additive fraction on combustion velocity was studied. According to the simulation and experimental results, the apparent activation energy was estimated using the Arrhenius diagram of $ln(v/T_{ad}){\sim}/T_{ad}$ based on the combustion equation given by Merzhanov et al. When the temperature exceeds the boiling point of aluminum (2,790 K), the apparent activation energy of the NiO/Al aluminothermic system is $64{\pm}14$ kJ/mol. In contrast, below 2,790 K, the apparent activation energy is $189{\pm}15$ kJ/mol. The process of combustion contributed to the mass-transference of aluminum reactant of the burning compacts. The reliability of the simulation results was experimentally verified.

• 한국해양공학회지
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• 제29권6호
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• pp.418-426
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• 2015

Recently, shipping operators have been making efforts to reduce the fuel cost in various ways, such as trim optimization and bulb re-design. Furthermore, IMO restricts the hydro-dioxide emissions to the environment based on the EEDI (Energy Efficiency Design Index), EEOI (Energy Efficiency Operational Indicator), and SEEMP (Ship Energy Efficiency Management Plan). In particular, ship speed is one of the most important factors for calculating the EEDI, which is based on methods suggested by ITTC (International Towing Tank Conference) or ISO (International Standardization Organization). Many shipbuilding companies in Korea have carried out speed trials around the Korea Straits. However, the conditions for these speed trials have not been exactly the same as those for model tests. Therefore, a ship’s speed is corrected by measured environmental data such as the seawater temperature, density, wind, waves, swell, drift, and rudder angle to match the conditions of the model tests. In this study, fundamental research was performed to evaluate the ship resistance performance due to changes in the water temperature and salinity, comparing the ISO method and numerical simulation. A numerical simulation of a KCS (KRISO Container ship) with a free-surface was performed using the commercial software Star-CCM+ under three conditions that were assumed based on the water temperature and salinity data in the Korea Straits. In the simulation results, the resistance increased under low water temperature & high salinity conditions, and it decreased under high water temperature & low salinity conditions. In addition, the ISO method showed the same result as the simulation.

• 한국항공우주학회지
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• 제49권1호
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• pp.53-61
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• 2021

본 논문은 고온 환경의 화력발전소 보일러 내부 점검용 드론 개발을 위한 선행연구로 AirSim을 이용한 고온 환경에서의 시뮬레이션을 통해 드론이 정상적인 비행이 가능한지 검증 하였다. 고온의 비행 환경에서는 공기 밀도, 점성계수 등이 상온과 달라 공력특성이 달라지며 이에 따라 드론의 비행성능 또한 달라진다. 따라서 온도 변화에 따른 프로펠러의 공력 특성의 변화를 확인하기 위해 JBLADE를 통한 프로펠러 해석과 추력 테스트, 전기추진계통 성능예측모델을 통한 동작특성예측을 수행하였다. 그리고 해석 및 성능예측 결과를 AirSim에 적용해 시뮬레이션을 진행하고 결과 분석을 통해 기체 재설계를 진행하였다. 재설계 결과 80℃의 환경에서 호버링 시 필요한 추력을 얻기 위해 재설계 전 최대 출력의 약 65% 사용하던 것이 52%로 감소함을 확인하였다.

• 대한화상학회지
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• 제21권1호
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• pp.17-21
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• 2018

Purpose: This study aimed to evaluate the thermal protective function of firefighter clothes and gloves through real scale fire simulations. Methods: Firstly, the fire simulation by real scale flame was performed for firefighter clothes. A manikin equipped with firefighter clothes was directly exposed to flames which energy average is 84 Kw/m². for 22 seconds. Heat flux gauges attached on the body measured surface temperature elevation. Secondly, we also performed the other fire simulation by hot plate exposure to firefighter gloves. Firefighter gloves with heat flux gauges exposed hot plate which temperature is 300℃ in both dry and moist conditions. Primary outcome was surface temperature change of manikin body (first simulation) and hand (second simulation) over times. Results: In the first flame simulation, the surface temperature of face and shoulders elevated more rapidly comparing with the other body surface area when initial period of flame shutter open. After 18sec of shutter open, the surface temperature of upper trunk elevated rapildy. After shutter closure, high surface temperature kept continuously on right side of face and left shoulder. In the second hot plate simulation, fingers and palms showed higher surface temperature than the other areas of hands in the both dry and wet conditions. Conclusion: This study suggests that the real scale flame enables firefighter clothes to lose their heat protective function suddenly after 18 seconds. Additionally, the protective function of firefighter gloves were relatively weaker in the palmar side of fingers than the other parts of hand. There should be additional study for evaluate thermal protection performance of firefighter clothes. And, further effort for reinforce palmar side of fingers of firefighter gloves should be done.

• 한국초전도ㆍ저온공학회논문지
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• 제6권1호
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• pp.33-38
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• 2004

This paper presents an effective simulation method for the high temperature superconducting (HTS) transformer using PSCAD/ EMTDC. Although researches and developments are performed for the HTS technologies, problems such as AC loss and quench phenomenon need to be solved for efficient design of HTS transformer. In addition, pre-study on the HTS transformer is a sort of time and cost consuming work, thus it is very worthy or being analyzing the characteristics of the HTS transformer in advance through a proper simulation method. It is very important to analyze the HTS devices by the simulation for seeking suitable and reasonable parameters for the practical application of those apparatuses in advance. A software- based component is suggested for- the simulation of the HTS transformer using PSCAD/ EMTDC and the numerical results are analyzed in detail in this paper.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.74.2-74.2
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• 2011

A simulation study on synthesis gas process in GTL process was carried out in order to find optimum operation conditions for GTL (gas-to-liquid) pilot plant design. Optimum operating conditions for synthesis gas process were determined by changing reaction variables such as feed temperature and pressure. During the simulation, overall synthesis process was assumed to proceed under steady-state conditions. It was also assumed that physical properties of reaction medium were governed by RKS (Redlich-Kwong-Soave) equation. The effect of temperature and pressure on synthesis gas process $H_2$/CO ratio were mainly examined. Simulation results were also compared to experimental results to confirm the reliability of simulation model. Simulation results were reasonably well matched with experimental results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.847-852
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• 2001

A thorough understanding of the transient behavior during load following and start-up is essential in the design and operation of an heat recovery steam generator(HRSG). During this period of time, material that is exposed to high temperature and experiences a large temperature variation is subject to high thermal stress. APESS(Advanced Plant Engineering & Simulation System) is a dynamic simulation software for power plant which is under being developed by Doosan Heavy Industries & Construction Co., Ltd. This paper present the introduction of APESS and the result of simulation for an heat recovery steam generator.

• KIEAE Journal
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• 제8권5호
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• pp.11-16
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• 2008

This research has established CFD model on pit's cool-tube system through heat and air movement simulations, of which data was based on experimental and verification. This research work verified the effectiveness of the cool-tube system by analysing temperature, humidity and air current of the actually installed case. Also, we analysed heat transfer through air current simulation and the results are as followings. Firstly, we experiment on temperature, humidity and speed of air currents of the cool tube system with pit space during the month of May (spring). The average exterior temperature was $16.1^{\circ}C$, and $18.2^{\circ}C$ for the pit, $24.7^{\circ}C$ for the compressor room. Secondly, based on measured data of real case, we have analysed heat transfer through air current simulation and verified our proposed model. The actual measurement of average temperature of exhaust air of the pit's area is $19.7^{\circ}C$ with tolerance of $-0.33^{\circ}C{\sim}-0.6^{\circ}C$ compared to above simulations. Thirdly, having verified air current simulation model with formation of 260,000 and 1,000,000 cells, we could get reasonable near values with 260,000 cells. Lastly, the next step of research would be focused on proposing the best possible pit's cool-tube system after analysis of heat transfer of the air current simulation based on verified CFD model.