• 한국산업융합학회 논문집
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• 제12권4호
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• pp.179-186
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• 2009

Electronic components in an enclosure have been investigated to prevent undesired thermal problems. The electronic devices, such as ECUs of automotive engines, are operated under the contaminated environments, so that they rely on the passive cooling without any fluid-driving methods. Therefore the radiation heat dissipation plays more important role than the conduction and convection heat transfer. Hence their combined heat dissipation phenomena have been simulated by a numerical model to reveal the effects of supplied heat flux, emissivity of material, geometry of enclosure, charging gas and pressure. The result showed that the radiation had a significant effect on the heat dissipation of module in an enclosure, and some space above the module should be reserved to prevent its thermal problem. In addition, the higher thermal conductivity and pressure of gas in an enclosure could be necessary to improve the thermal dissipation from the electronic devices.

• 한국태양에너지학회 논문집
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• 제38권6호
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• pp.1-14
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• 2018

The shading device on the window of the building can be an passive solution to reduce the cooling load and lighting energy, as well as improving the indoor comfort. It is also an architectural element that must be considered for building energy-efficient buildings such as eco-buildings and zero-energy buildings. However, due to various building environments and various shading devices, the installation of excessive shade may lead to the risk of losing the effectiveness of windows. In this study, we propose a method for optimal automatic control of shading device and evaluate its effectiveness by energy analysis of several shading devices.

• 천문학회보
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• 제42권2호
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• pp.87.3-88
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• 2017

한국천문연구원은 차세대소형위성 1호의 근적외선 영상분광기 NISS (Near-infrared Imaging Spectrometer for Star formation history) 탑재체를 개발하여 2017년 6월 30일에 최종 비행모델을 납품하였고, 이 발표는 탑재체 NISS 구조체의 비행모델 개발 결과를 보고한다. NISS는 0.9 - 2.5um (R~20) 근적외선 파장에서 관측을 해야 하기 때문에, 구조체의 배경잡음을 없애기 위해서 200K까지 passive cooling으로 냉각되며, H2RG 검출기는 소형 냉동기에 의해 약 88K에서 운영된다. NISS 구조체의 passive cooling을 효율적으로 수행하기 위해서 방열판, Kevlar 지지대, MLI, 표면제어용 필름 등을 조립하였고, 실제 지상 시험을 통해서 그 성능을 확인하였다. NISS 구조체는 최종 시스템 조립 과정에서 전자부 하네스 조립을 함께 수행했으며, 온도 모니터링 센서를 부착하고 소형 냉동기 피드백 온도를 반복 시험을 통해서 결정하였다. NISS 구조체는 미러 및 렌즈를 지지하는 광기계부를 함께 포함하기 때문에 발사 및 우주환경에서 광학 성능을 유지하기 위한 설계를 거쳐서 제작 되었으며, 최종 시스템 검교정 시험, 진동 및 열진공 시험을 통해서 그 성능을 확인하였다. NISS를 탑재한 차세대소형위성 1호는 2018년 상반기에 미국의 Falcon 9 발사체에 실려서 발사될 예정이다.

• 에너지공학
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• 제27권4호
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• pp.27-35
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• 2018

피동원자로건물냉각계통(PCCS)은 사고 발생 시 원자로건물로 방출된 열을 제거하여 원전의 건전성을 보장하기 위해 설계되었다. PCCS의 열제거 성능은 증기-공기 혼합물의 응축열전달에 의해 결정된다. 본 연구에서는 응축열전달계수의 예측 정확도를 향상시키기 위해 새로운 상관식을 이식한 MARS-KS 코드를 사용하여 PCCS의 열제거 성능을 평가하였다. MARS-KS 코드에 사용된 새로운 상관식은 압력, 벽면과냉도, 비응축성 기체 질량분율 및 응축튜브의 종횡비와 같은 열전달계수에 영향을 미치는 변수들을 이용하여 개발하였고, 이는 MARS-KS코드의 기본 응축 모델인 Colburn-Hougen 모델을 대체하여 적용되었다. 대형파단 냉각재상실사고 발생 시 PCCS의 운전에 따른 다양한 열수력학적 변수들을 분석하였고, 열제거 성능 평가를 위해 새로운 상관식이 적용된 MARS-KS 코드의 원자로건물 압력거동 계산결과와 기존의 응축모델을 이용한 해석결과를 비교하였다.

• 대한건축학회논문집:계획계
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• 제35권11호
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• pp.25-34
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• 2019

It is important to design windows in a reasonable way considering the performance characteristics of the elements of the window rather than just to increase the thermal energy performance of the window. In this study, the Heat-transfer Coefficient as insulation performance of the windows and together with the grade of the glass's SHGC (Solar Heat Gain Coefficient) were analyzed to relate to the energy efficiency performance of the building by azimuth angle. Based on this basic study, the Heat-transfer Coefficient of windows and the SHGC rating of glass were applied to the unit plan of apartment building, and the Heating and Cooling Demand were analyzed by azimuth angle. Apartment plan types were divided into 2 types of Non-extension and extension of balcony. The designPH analysis data derived from the variant of the Heat-transfer Coefficient and SHGC, were put into PHPP(Passive House Planning Package) to analyze precisely the energy efficiency(Heating and Cooling Demands) of the building by azimuth angle. In addition, assuming the 'ㅁ' shape layout, energy efficiency performance and potential of PV Panel installation also were analyzed by floors and azimuth angle, reflecting the shading effects by surrounding buildings. As the results of the study, the effect of Heat Gain by SHGC was greater than Heat Loss due to the Heat-transfer Coefficient. So it is more effective to increase SHGC to satisfy the same Heating Demand, and increasing SHGC made possible to design windows with low Heat-transfer Coefficient. It was also revealed that the difference in annual Heating and Cooling Demands between the low, mid and high floor households is significantly high. In addition to it, the installation of PV Panel in the form of a shading canopy over the window reduces the Cooling Load while at the same time producing electricity, and also confirmed that absolute thermal energy efficiency could not be maximized without controlling the thermal bridge and ventilation problems as important heat loss factors.

• 한국안전학회지
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• 제35권4호
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• pp.84-91
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• 2020

The Korean nuclear industry developed the SPACE (Safety and Performance Analysis Code for nuclear power plants) code and this code adpots two-phase flows, two-fluid, three-field models which are comprised of gas, continuous liquid and droplet fields and has a capability to simulate three-dimensional model. According to the revised law by the Nuclear Safety and Security Commission (NSSC) in Korea, the multiple failure accidents that must be considered for accident management plan of nuclear power plant was determined based on the lessons learned from the Fukushima accident. Generally, to improve the reliability of the calculation results of a safety analysis code, verification work for separate and integral effect experiments is required. In this reason, the goal of this work is to verify calculation capability of SPACE code for multiple failure accident. For this purpose, it was selected the experiment which was conducted to simulate a Multiple Steam Generator Tube Rupture(MSGTR) accident with Passive Auxiliary Feedwater System(PAFS) operation by Korea Atomic Energy Research Institute (KAERI) and focused that the comparison between the experiment results and code calculation results to verify the performance of the SPACE code. The MSGR accident has a unique feature of the penetration of the barrier between the Reactor Coolant System (RCS) and the secondary system resulting from multiple failure of steam generator U-tubes. The PAFS is one of the advanced safety features with passive cooling system to replace a conventional active auxiliary feedwater system. This system is passively capable of condensing steam generated in steam generator and feeding the condensed water to the steam generator by gravity. As the results of overall system transient response using SPACE code showed similar trends with the experimental results such as the system pressure, mass flow rate, and collapsed water level in component. In conclusion, it could be concluded that the SPACE code has sufficient capability to simulate a MSGTR accident.

• KIEAE Journal
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• 제16권4호
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• pp.63-69
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• 2016

Purpose: This preliminary study investigated a potential of the water wall systems that provide heat storage and natural lighting control simultaneously. Method: In order for transparency of the water wall to be controlled, the study first proposed two measures: to adjust transparency of the water wall; to control transparency of water wall surface. The performance of two measures then was verified and compared by experiments. In addition, a trade-off between heat collect and heat storage resulting from using additive for adjusting transparency was investigated. Result: The experiment showed that the two measures are similar in performance. The investigation of trade-off relation showed the additive should have the same heat storage as the water to prevent decrease in thermal performance of the water wall. As an economical measure to control transparency of the water wall, this study suggested a measure of secondary heat transfer systems using shading device that first absorbs solar radiation and then transfers heat to the water wall. The experiment show that performance of the proposed measure is similar to controlling transparency of water wall surface. In conclusion, it is expected that the performance of the water wall can be economically maximized by using the proposed mean in terms of heating, cooling and lighting energy saving.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.696-706
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• 2023

Consequences of an anticipated Beyond Design Basis Accident (BDBA) Long-Term Station Blackout (LTSBO) event with complete loss of grid power in the VVER-1200 reactor of Rooppur Nuclear Power Plant (NPP) of Unit-1 are assessed using the RASCAL 4.3 code. This study estimated the released radionuclides, received public radiological dose, and ground surface concentration considering 3 accident scenarios of International Nuclear and Radiological Event Scale (INES) level 7 and two meteorological conditions. Atmospheric transport, dispersion, and deposition processes of released radionuclides are simulated using a straight-line trajectory Gaussian plume model for short distances and a Gaussian puff model for long distances. Total Effective Dose Equivalent (TEDE) to the public within 40 km and radionuclides contribution for three-dose pathways of inhalation, cloudshine, and groundshine owing to airborne releases are evaluated considering with and without passive safety Emergency Core Cooling System (ECCS) in dry (winter) and wet (monsoon) seasons. Source term and their release rates are varied with the functional duration of passive safety ECCS. In three accident scenarios, the TEDE of 10 mSv and above are confined to 8 km and 2 km for the wet and dry seasons, respectively in the downwind direction. The groundshine dose is the most dominating in the wet season while the inhalation dose is in the dry season. Total received doses and surface concentration in the wet season near the plant are higher than those in the dry season due to the deposition effect of rain on the radioactive substances.

• 한국태양에너지학회 논문집
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• 제39권6호
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• pp.127-135
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• 2019

In this study, we analyzed the relationship between five factors: long-wave radiation, short-wave radiation, cloudiness, SVF and summer shelters. In the previous study, we recognized the correlation between single building SVF and long-wave radiation. Furthermore, this study attempted to confirm the relationship at the summer shelter with high solar radiation blocking rate. The observations are as follows. ① Cooling in summer shelters was not the effect of temperature but the effect of radiation reduction due to short-wave radiation shielding. ② In the case of the canopy tent with low heat capacity, the long-wave radiation was observed to be 16.7% higher per hour than the comparison control point due to the increase in surface temperature. ③ The long-wave radiation increase rate was different according to SVF, but showed very similar pattern according to the material characteristics of the summer shelters. ④ Passive Cooling effect on the type of summer shelters are determined by the size of the total long and short-wave radiation at that point.

• 전력전자학회논문지
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• 제26권5호
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• pp.325-333
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• 2021

A 3 kW grid-tied PV inverter with Gallium nitride high-electron mobility transistor (GaN HEMT) for domestic commercialization was developed using boost converter and full-bridge inverter with LCL filter topology. Recently, many GaN HEMTs are manufactured as surface mount packages because of their lower parasitic inductance characteristic than standard TO (transistor outline) packages. A surface mount packaged GaN HEMT releases heat through either top or bottom cooling method. IGOT60R070D1 is selected as a key power semiconductor because it has a top cooling method and fairly low thermal resistances from junction to ambient. Its characteristics allow the design of a 3 kW inverter without forced convection, thereby providing great advantages in terms of easy maintenance and high reliability. 1EDF5673K is selected as a gate driver because its driving current and negative voltage output characteristics are highly optimized for IGOT60R070D1. An LCL filter with passive damping resistor is applied to attenuate the switching frequency harmonics to the grid-tied operation. The designed LCL filter parameters are validated with PSIM simulation. A prototype of 3 kW PV inverter with GaN HEMT is constructed to verify the performance of the power conversion system. It achieved high power density of 614 W/L and peak power efficiency of 99% for the boost converter and inverter.