• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.953-958
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• 2006

Perimeter zone has been reinforced by active systems, such as fan-coil units, because it causes an increase in heating and cooling loads, dew condensation in winter, or discomfort with cold-draft to residents in buildings, through poor insulation by light-weighed skin due to progressing multi-storied buildings and skyscrapers. However, because these active systems raise Its capacity so that fossil fuel is used as much as they are added, and ultimately, greenhouse effect is urged, we proposed BIPV system functioned as solar collector which can substitute active system. As an early stage, heat balance equation in steady-state by Fortran was used not only for pre-heating effect and electric power capacity during the day in winter, but also for electric power capacity during day in slimmer and sky radiation effect during night in summer. Especially, we should have considered shading on PV, since even a little bit of it makes the efficiency too low for the PV to work. Still, when the flux of pre-heated air was increased to make air-barrier, its temperature was not enough to make it because the speed of heat exchange was too fast to warm up the air, thus the capacity to meet the condition was evaluated, and electric power from PV was made used for it.

• Nuclear Engineering and Technology
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• 제45권4호
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• pp.469-476
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• 2013

In a postulated severe core damage accident in a PHWR, multiple failures of core cooling systems may lead to the collapse of pressure tubes and calandria tubes, which may ultimately relocate inside the calandria vessel forming a terminal debris bed. The debris bed, which may reach high temperatures due to the decay heat, is cooled by the moderator in the calandria. With time, the moderator is evaporated and after some time, a hot dry debris bed is formed. The debris bed transfers heat to the calandria vault water which acts as the ultimate heat sink. However, the questions remain: how long would the vault water be an ultimate heat sink, and what would be the failure mode of the calandria vessel if the heat sink capability of the reactor vault water is lost? In the present study, a numerical analysis is performed to evaluate the thermal loads and the stresses in the calandria vessel following the above accident scenario. The heat transfer from the molten corium pool to the surrounding is assumed to be by a combination of radiation, conduction, and convection from the calandria vessel wall to the vault water. From the temperature distribution in the vessel wall, the transient thermal loads have been evaluated. The strain rate and the vessel failure have been evaluated for the above scenario.

• Nuclear Engineering and Technology
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• 제55권1호
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• pp.144-155
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• 2023

The core catcher is used as a passive safety system in new generation nuclear power plants to create a space in the containment for the placing and cooling of the molten corium under various severe accidents. This research investigates the role of the core catcher in the VVER-1000 reactor containment system in mitigating the effects of core meltdown under various severe accidents within the context of the Ex-vessel Melt Retention (EVMR) strategy. Hence, a comparison study of three severe accidents is conducted, including Station Black-Out (SBO), SBO combined with the Large Break Loss of Coolant Accident (LB-LOCA), and SBO combined with the Small Break Loss of Coolant Accident (SB-LOCA). Numerical comparative simulations are performed for the aforementioned scenario with and without the EX-vessel core-catcher. The results showed that considering the EX-Vessel core catcher reduces the amount of hydrogen by about 18.2 percent in the case of SBO + LB-LOCA, and hydrogen production decreases by 12.4 percent in the case of SBO + SB-LOCA. Furthermore, in the presence of an EX-Vessel core-catcher, the production of gases such as CO and CO2 for the SBO accident is negligible. It was revealed that the greatest decrease in pressure and temperature of the containment is related to the SBO accident.

• 천문학회보
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• 제46권1호
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• pp.28.2-28.2
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• 2021

We investigate the impact of ram pressure stripping due to the intracluster medium (ICM) on star-forming disk galaxies with a multiphase interstellar medium maintained by strong stellar feedback. We carry out radiation-hydrodynamic simulations of an isolated disk galaxy embedded in a 1011 M⦿ dark matter halo with various ICM winds mimicking the cluster outskirts (moderate) and the central environment (strong). We find that both star formation quenching and triggering occur in ram pressure-stripped galaxies, depending on the strength of the winds. HI and H2 in the outer galactic disk are significantly stripped in the presence of moderate winds, whereas turbulent pressure provides support against ram pressure in the central region, where star formation is active. Moderate ICM winds facilitate gas collapse, increasing the total star formation rates by ~40% when the wind is oriented face-on or by ~80% when it is edge-on. In contrast, strong winds rapidly blow away neutral and molecular hydrogen gas from the galaxy, suppressing star formation by a factor of 2 within ~200 Myr. Dense gas clumps with nH≳10 M⦿ pc-2 are easily identified in extraplanar regions, but no significant young stellar populations are found in such clumps. In our attempts to enhance radiative cooling by adopting a colder ICM of T=106K only a few additional stars are formed in the tail region, even if the amount of newly cooled gas increases by an order of magnitude.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.498-505
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• 2024

In this paper, a cable-driven endoscopic manipulator (CEM) is designed for the Chinese latest compact fusion reactor. The whole CEM arm is more than 3000 mm long and includes end vision tools, an endoscopic manipulator/control system, a feeding system, a drag chain system, support systems, a neutron shield door, etc. It can cover a range of ±45° of the vacuum chamber by working in a wrap-around mode, etc., to meet the need for observation at any position and angle. By placing all drive motors in the end drive box via a cable drive, cooling, and radiation protection of the entire robot can be facilitated. To address the CEM motion control problem, a discrete trajectory tracking method is proposed. By restricting each joint of the CEM to the target curve through segmental fitting, the trajectory tracking control is completed. To avoid the joint rotation angle overrun, a joint limit rotation angle optimization method is proposed based on the equivalent rod length principle. Finally, the CEM simulation system is established. The rationality of the structure design and the effectiveness of the motion control algorithm are verified by the simulation.

• 생물환경조절학회지
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• 제3권1호
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• pp.58-65
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• 1994

본 시험은 하절기 경제성을 고려한 효율적인 온도하강방법을 구명하고자 차광재료, fog system, 송풍등 복합적 온도하강처리에 따른 비닐하우스의 기상환경변화를 조사하여 다음과 같은 결과를 얻었다. 1. 중형하우스에서 온도하강방법에 따른 환경특성은 처리에 따라 하우스의 고온화를 상당히 효율적으로 억제하였다. 7월31일 하우스냉방처리에 따른 기온의 일중변화를 경시적으로 보면 수분의 증발잠력능력을 이용한 fog system과 은색차광 및 송풍을 혼합하여 처리할 경우 기온과 지온은 외기온에 비하여 최고 각각 1$0^{\circ}C$, 4$^{\circ}C$정도 온도하강효과가 있었으며 그 다음은 은색차광＋fog system, 은색차광＋송풍, 흑색차광＋송풍구 순이였다. 2. 하절기 가장 온도가 높은 시기인 7월20일부터 8월21일까지 하우스냉방처리에 따른 온도하강 효과를 보면 최고기온은 시험처리에 따라 온도차가 인정되며 은색차광＋fog system＋송풍구의 지상, 지표면기온은 외기온에 비하여 각각 약 8$^{\circ}C$, 7$^{\circ}C$정도 온도하강 효과가 있었다. 3. 은색차광＋송풍구와 흑색차광＋송풍구의 일사량은 청명한날 외기일사량에 비하여 각각 약 29.3%, 32.5%이였으며 흐린 날은 각각 약 27.4%, 31.8%이였다.

• 한국태양에너지학회 논문집
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• 제35권2호
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• pp.73-83
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• 2015

When it comes to these buildings for business use, cooling load during summertime was reported to have great importance which, as a result, impressively increased interest in Solar Heat Gain Coefficient (SHGC). Such SHGC is considered to be lowered with the help of colors and functions of glass itself, internal shading devices, insulation films and others but basically, these external shading devices for initial blocking that would not allow solar heat to come in from outside the buildings are determined to be most effective. Of many different external shading devices, this thesis conducted an analysis on Exterior Venetian Blind. As for vertical shading devices, previous researches already calculated SHGC conveniently using concepts of sky-opening ratios. However in terms of the Venetian Blind, such correlation is not possibly applied. In light of that, in order to extract a valid correlation, this study first introduced a concept called shape factor, which would use the breadth and a space of a shade, before carrying out the analysis. As a consequence, the concept helped this study to find a very similar correlation. Results of the analysis are summarized as follows. (1) Regarding SHGC depending on the surface reflectance of a shade, an average of 2% error is observed and yet, the figure can always be ignored when it comes to a simple calculation. (2) As for SHGC of each bearing, this study noticed deviations of 4% or less and in the end, it is confirmed that extraction can be achieved with no more than one correlation formula. (3) When only the shape factor and nothing else is used for finding a correlation formula, the formula with a deviation of approximately 5% or less is what one would expect. (4) Since the study observed slight differences in bearings depending on ranges of the shape factors, it needed to extract a weighted value of each bearing, and learned that the smaller the shape factor, the wider the range of a weighted value. The study now suggests that a follow-up research to extract a simple calculation formula by dealing with all these various inclined angles of shade, solar radiation conditions of each region (the ratio of diffuse radiation to direct radiation and others) as well as seasonal features should be carried out.

• 생물환경조절학회지
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• 제28권3호
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• pp.225-233
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• 2019

여름철에 자연환기는 온실의 온도를 낮추는데 중요한 역할을 한다. 온실의 형태, 환기창 종류, 환기창의 위치 등은 자연환기 성능에 큰 영향을 미친다. 본 연구에서는 전산유체역학(CFD)을 이용하여 다양한 천창구조에 대하여 측창에 따른 부력환기 효과를 비교분석 하였다. Boussinnesq 가정을 사용하여 전체 계산영역에 대한 부력효과를 시뮬레이션 하였다. 또한 RNG $K-{\varepsilon}$ 난류모델을 사용하였다. 일사량 효과를 시뮬레이션 하기 위해 Solar ray tracing과 함께 Discrete originates (DO) radiation 모델을 사용하였다. 실험온실 내부의 온도를 측정하여 CFD모델을 검증하였으며, 실험값과 계산값이 잘 일치하는 것으로 나타났다. 7가지의 천창구조에 대하여 온실의 내외부 온도차이와 환기횟수를 비교하였다. 내외부온도의 차이는 $3.2{\sim}9.6^{\circ}C$ 범위로 나타났고, 환기횟수는 $0.33{\sim}0.49min^{-1}$ 범위로 나타났다. 고깔형 천창구조 온실의 경우 내외부 온도차이가 $3.2^{\circ}C$로 가장 낮았고 환기횟수도 $0.49min^{-1}$로 가장 높게 나타나 환기효과가 가장 우수한 것으로 나타났다.

• 한국농림기상학회지
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• 제23권3호
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• pp.141-148
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• 2021

솔라 쉐어링이라고도 불리는 영농형 태양광은 작물의 광포화점 이상의 태양광을 솔라 패널을 이용한 발전에 활용하는 개념으로, 잉여 태양광 차단에 따른 지면에 입사하는 태양복사 에너지의 감소로 인한 증발산량 감소와 함께 지면 냉각 효과로 메탄 배출량도 줄이는 효과를 가져올 수 있어 기후 스마트 농업을 구현할 수 있는 기술로 기대되고 있다. 본 연구에서는 파주 영농형 태양광 시설 하부 및 외부 논에 상/하향 장/단파 복사, 기온, 습도, 지온, 수온, 풍향, 풍속 등을 관측하는 자동기상관측장비를 설치하여 시설 하부와 외부의 농업환경을 관측하고 비교함으로써, 영농형 태양광이 농가에 태양광 발전을 통한 부가적인 수입을 안기면서 재배 시 발생하는 물 소비와 메탄 배출을 줄이는 기후 스마트 농업 실현에 적합한지 그 가능성을 확인해 보았다. 관측 기간 동안 영농형 태양광 시설 하부의 평균 일사량은 노지 일사량의 약 70% 정도였으며, 영농형 태양광 시설 하부 논과 노지 논에서 기온의 차이는 거의 없었지만 지온과 수온은 명확한 차이가 확인되었다. 실제로 이러한 환경의 차이가 물 소비량 및 온실가스 배출량 감소로 이어지는지 플럭스 실측을 통한 확인이 요구된다.

• 생물환경조절학회지
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• 제27권4호
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• pp.277-284
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• 2018

온실의 냉난방부하 산정을 위해 설계자가 선택해야할 주요 변수들에 대하여, 이들 설계 변수가 냉난방부하에 미치는 영향을 평가하기 위해서 각각의 설계 변수값을 변화시키면서 시뮬레이션을 실시하였으며, 이를 바탕으로 특별히 선택에 주의를 기울여야 할 설계 변수를 제안하였다. 난방부하에 가장 큰 영향을 미치는 설계 변수는 피복재의 열관류율이고, 다음으로 설계외기온인 것으로 나타났다. 연동수에 따른 설계 변수의 영향은 차이가 거의 없는 것으로 나타났다. 단동 온실의 경우에는 지중전열 관련 설계 변수의 영향을 무시할 수 없을 것으로 생각되지만, 연동 온실의 경우에는 지중전열 관련 변수 및 틈새환기율의 영향이 미미한 것으로 판단되었다. 냉방부하에 가장 큰 영향을 미치는 설계 변수는 온실내로 유입되는 일사량과 증발산계수이고, 다음으로 실내외 기온차, 환기율인 것으로 나타났다. 설계 변수의 영향은 단동 온실과 연동 온실에서 큰 차이를 보였으나, 연동수에 따른 차이는 거의 없는 것으로 나타났다. 피복재의 열관류율은 단동 온실이나 연동 온실 모두 영향이 미미한 것으로 나타났지만, 실내외 기온차 및 환기율의 경우에는 냉방부하에 미치는 영향을 무시할 수 없을 것으로 생각되며, 특히 연동 온실에서 그 영향이 더 큰 것으로 판단되었다. 냉방부하를 산정할 때 실내 목표온도를 낮게 설정할수록 설계 변수의 선택에 신중해야 한다. 특히, 실내 목표온도를 외기온 보다 낮게 설정하면 환기율 및 열관류율 값이 냉방부하를 증가시키는 방향으로 바뀌므로 더욱 주의해야 한다. 환기율이 낮을 때는 설계 변수 중 설계일사량과 증발산계수의 선택에 주의해야 하고, 환기율이 높을 때는 실내 설정온도와 설계외기온의 선택에 신중을 기해야 한다.