• Journal of Advanced Marine Engineering and Technology
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• 제32권1호
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• pp.131-136
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• 2008

The double-walled steel vessel with powder insulation in the space between the walls is used to minimize heat transfer by radiation and conduction in cryogenic storage tank. The vacuum required the insulation is much less extreme than with high-vacuum or multilayer insulations. The solid supports are used to bear the weight of the inner container. Thermal and structural analysis of the tank have been carried out to study the effect of vacuum and weldment geometry of the internal supports. Heat flux in wall is increased with increasing of thermal conductivity of perlite. Heat flux and stress of support is not affected by weldment geometry.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.670-676
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• 2014

The objective of this research is to utilize the ultrasonic method to analyze the property of partial discharge (PD) which is generated by the winding of the insulation stator in the generator. Therefore, a PD measurement system is built based on ultrasonic and virtual instruments. Three types of PD models (internal PD model, surface PD model and slot PD model) have been constructed. With the analysis of these experimental results, this research has identified the ultrasonic signals of the discharges which were produced by three types of PD models. This analysis shows the different features among these PD types. Both the time domain and frequency domain of the ultrasonic signals are obviously different. In addition, an experiment based on a large rotating machine has been done to analyze ultrasonic noises. The result indicates that the ultrasonic noises can be wiped off by the filters and algorithms. The application of this system is convenient for the detection of early signs of insulation failure, which is an effective method for diagnosis of insulation faults.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.441-444
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• 2004

In the sound insulation measurements, the influence of background (extraneous) noise is often serious problem and how to reduce its effect and to improve the signal-to-noise(S/N) ratio is an important theme. As the background noise, such extraneous noises as road traffic noise and machine noise often disturb the measurement. In laboratory measurements on specimens with high sound insulation performances, even the internal noise of the measurement system can become a problem. To improve the signal-to-noise ratio and to improve the measurement accuracy, various kinds of digital signal processing techniques can be applied. In this paper, four kinds of digital signal processing techniques are applied and their effectiveness is examined through field measurements.

• 한국태양에너지학회 논문집
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• 제37권4호
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• pp.35-47
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• 2017

Energy efficiency solutions are being pursued as a sustainable approach to reducing energy consumption and related gas emissions across various sectors of the economy. Vacuum Insulation Panel (VIP) is an energy efficient advanced insulation system that facilitates slim but high-performance insulation, based on a porous core material evacuated and encapsulated in a barrier envelope. Although VIP has been applied in buildings for over a decade, it wasn't until recently that efforts have been initiated to propose and adopt a global standard on characterization and testing of VIP. One of the issues regarding VIP is its durability and aging due to pressure and moisture dependent increase of the initial low thermal conductivity with time; more so in building applications. In this paper, the aging of commercially available VIP was investigated experimentally; thermal conductivity was tested in accordance with ISO 8302 standard (guarded hot box method) and long-term durability was estimated based on a non-linear pressure-humidity dependent equation based on study of IEA/ECBCS Annex 39, with the aim of assessing durability of VIP for use in buildings. The center-of-panel thermal conductivity after 25 years based on initial 90% fractile with a confidence level of 90 % for the thermal conductivity (${\lambda}90/90$) ranged from 0.00726-0.00814 (W/m K) for silica core VIP. Significant differences between manufacturer-provided data and measurements of thermal conductivity and internal pressure were observed.

• 한국건축시공학회지
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• 제16권6호
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• pp.595-601
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• 2016

현재 건축구조물에 사용되는 단열재의 단열성능은 초기성능을 기준으로 설계 시에만 반영하고 있으며, 장기 내구성 저하에 따른 단열성능 감소는 반영되고 있지 않다. 본 연구에서는 가속내구성 시험을 통해 단열재의 내구성 저하에 따른 단열성능 저하를 검토하였다. 연구결과, 발포폴리스티렌 단열재 비드법의 경우 표준환경 조건 및 실험실 가속 시험 조건에서는 경시변화에 따른 성능저하가 나타나지 않았으나, 동결 융해 시험 조건에는 성능이 저하하는 것으로 나타났다. 반면, 압출법의 경우 동결 융해 시험 조건에서는 단열성능 저하가 작았지만, 경시변화 초기에 내부 가스의 방출로 급격한 성능저하를 나타내었다. 또한, 경질 폴리우레탄 폼 단열재의 경우 다른 단열재에 비해 초기 단열성능이 매우 뛰어났으나, 실험실 가속 시험조건 및 동결 융해 시험 조건에서는 성능이 다소 저하하는 것으로 나타났다.

• 한국포장학회지
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• 제27권3호
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• pp.175-180
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• 2021

Although it has recently been regulated for use as an eco-friendly policy in Korea, the use of EPS (Expanded Polystyrene) cooling boxes, which are used as cold chain delivery insulation boxes for fresh agricultural and livestock products, is also increasing rapidly as e-commerce logistics such as delivery have increased rapidly due to COVID-19. Studies were conducted to optimize the EPS cooling container through internal air heat flow of CFD (Computational Fluid Dynamics) analysis and FEM (Finite Element Method) random vibration analysis using domestic PSD (Power Spectral Density) profile of the EPS cooling box to which the refrigerant is applied in this study. In the analysis of the internal air heat flow by the refrigerant in the EPS cooling box, the application of vertical protrusions inside was excellent in volume heat flow and internal air temperature distribution. In addition, as a result of random vibration analysis, the internal vertical protrusion gives the rigid effect of the cooling box, so that displacement and stress generation due to vibration during transport are smaller than that of a general cooling container without protrusion. By utilizing the resonance point (frequency) of the EPS cooling box derived by the Model analysis of ANSYS Software, it can be applied to the insulation and cushion packaging design of the EPS product line, which is widely used as insulation and cushion materials.

• 전기학회논문지P
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• 제58권4호
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• pp.541-545
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• 2009

This study evaluated the contact resistance, insulation resistance, withstand voltage characteristics and insertion force, etc., of the wire connector used inside an integrated LITE WAY lighting fixture developed for efficient installation. Since the connector connecting the lighting fixture's internal wires is housed, it is easily connected and separated and has a structure enabling a close-fitting connection. The temperature and time applied to the high temperature characteristics test of the connector are $105^{\circ}C$ and 16 hours, respectively. The measured contact resistance of the high temperature tested connector was 3.258 mV/A, and its measured insulation resistance was greater than $10\;G{\Omega}$ All specimens demonstrated uniform insulation characteristics, which could be seen to be in good condition. From the withstand voltage test results found before and after performing the high temperature operation test on the connector for cable connection, it was confirmed that the withstand voltage characteristics between all terminals were good. The insertion force of the connector connecting the internal wiring averaged 9.67 kgf. It was observed that the insertion force between the plug housing and the female terminal, and that between the plug housing and the male terminal, were 0.680 kgf and 1.27 kgf on average, respectively.

• 한국터널지하공간학회 논문집
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• 제13권4호
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• pp.319-345
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• 2011

한랭지에 건설된 터널의 경우 터널 주변지반 지하수의 동결은 동절기 터널 배수 장애의 원인이 되며 라이닝을 내공 측으로 압출시키는 원인으로 작용하기도 한다. 노르웨이 등 해외에서는 이미 한랭지에 건설되는 터널의 동해방지를 위한 단열기준을 가지고 있으나 국내에서는 아직까지 터널 라이닝 동해방지를 위한 단열설계가 도입되어 있지 않은 실정이다. 본 연구에서는 국내 도로터널의 동결 사례를 고찰하여 터널 라이닝 동해방지 대책이 필요함을 파악하였다. 또한 터널 주위의 온도분포를 파악하기 위해 화악터널에서 터널 종단길이에 따른 온도분포, 라이닝 내부의 온도, 포장면 하부지반의 온도 분포를 계측하였으며 이로부터 외기 온도변화에 따른 터널 내부 온도 분포 특성을 분석하였다. 화악터널의 온도분포 계측 결과를 바탕으로 단열재의 성능시험을 위해 인공기후실에서 단열재 설치 유무에 따른 암석시편의 열유동 실험을 수행하였다. 또한 터널 라이닝 동해를 방지할 수 있는 적정 단열재 두께를 제안하기 위해 3 차원 수치해석을 실시하였다. 수치해석 결과로부터 터널배면 지하수 동결기준으로 동결지수를 약 291$^{\circ}C{\cdot}$ Hr로 제안하였다.

• 청정기술
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• 제28권1호
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• pp.18-23
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• 2022

에너지 절약을 위한 연구 중 단열 기술 분야에서는 공기의 낮은 열전도도를 활용한 연구가 이뤄지고 있으며 널리 상용화 되고 있다. 본 연구에서는 입자 내부에 공기층을 갖는 중공형(hollow) 형태의 실리카 나노 입자를 제조하여 공기층 크기가 단열 성능에 미치는 영향에 대해 고찰하였다. Polystyrene 주형법을 이용하여 졸-겔공정을 통해 속이 빈 중공형 실리카 나노 입자(Hollow silica nanoparticles)를 제조하였고, 입자를 5 wt %로 도료에 첨가한 후 열전달 실험을 통해 단열 성능을 확인하였다. 기존 페인트에 입자를 혼합하여 약 15 %이상의 단열효율을 나타냈으며, 내부 공기층의 크기가 큰 입자가 작은 입자에 비해 5% 높은 단열 성능을 나타냈다. 이번 연구를 통해 내부 크기에 따른 단열효과의 차이를 보여줌으로써, 중공형 형태의 입자를 첨가제나 도료 제조에 사용하는 경우 단열효과를 높이기 위해 매질 내에서 입자가 공기층을 최대로 이룰 수 있도록 입자의 크기를 고려해야함을 제시한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.857-859
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• 1992

The molten carbonate fuel cell is a new method for generating power which uses coal gasification gas and reformed liquid natural gas for fuel at very high efficiency and with minimal pollution. The purpose of this research is to investigate principle, properties and research status of internal reforming molten carbonate fuel cell.