Both theoretical and experimental investigations were conducted to analyze defrosting behavior of a window heater operating in the low outdoor temperature(-20℃). To achieve this purpose, first a warm-chamber experiment(23℃) were performed to measure inner and outer surface temperature of the rear window as functions of both time and position. Secondly, a cold chamber experiment was made to continuously record defrosting process of the frosted window. Therefore this study was carried out to presume for mutual relation of analysis condition to get the optimum temperature distribution by three-way layout. The results shown that coefficient of determination has a fine reliability over 99.77%, 99.85% and temperature distribution is made by three-way layout.

In this study, the heat flow characteristics of natural convection was theoretically analyzed with time by changing various locations of heat trace with tube surface about enclosed circular tube by applying nominal tube diameter 90 mm of KS D 3507. Before carrying out CFD (Computational Fluid Dynamics) analysis, it is presumed that the boundary condition is the tube’s inside and outside fluid temperature of 273 °K, the tube surface heat flux according to the heat trace location of 16 W/m. The result confirmed that water of inside tube is occurred natural convection caused by density difference depending on temperature profile. Additionally, in case of heat trace location, the heat transfer and flow characteristics showed clearly that two-heat trace location =135° and 180° was more favorable distribution than one-heat trace appropriate location =135°.

This study aims to examine the risk of electrical fire in places where electric heat wires are used. In general, the use of electric heating wires is becoming more common and prevalent in a bid to prevent increasing damage caused by freezing and bursting in residential water pipes, factory pipes and irrigation pipes in vinyl greenhouse and a variety of heat wire products are available in market with legal safety requirements imposed on them. However, the widespread use of anti-freezing burst heat wire products has caused increasing incidents of fire, which often fail to be incorporated into statistics due to quick onsite extinguishing and insignificant damage although damage is gradually on the rise. Against this backdrop, this study aims to look into the possibility of ignition caused by electric heat wires and the mechanism of how it turns into catching fire through overheat and short circuit tests for anti-freezing burst electrical heat wires (hereinafter called the ‘heat wire’) and expects to serve as the basis for further observations and analyses on the cause of fire and the process of ignition in a scientific manner.

The a-Si:H/c-Si hetero-junction (HJ) solar cells have a variety of advantages in efficiency and fabrication processes. It has already demonstrated about 23% in R&D scale and more than 20% in commercial production. In order to further reduce the fabrication cost of HJ solar cells, fabrication processes should be simplified more than conventional methods which accompany separate processes of front and rear sides of the cells. In this study, we propose a simultaneous deposition of intrinsic thin a-Si:H layers on both sides of a wafer by dual hot wire CVD (HWVCD). In this system, wafers are located between tantalum wires, and a-Si:H layers are simultaneously deposited on both sides of the wafer. By using this scheme, we can reduce the process steps and time and improve the efficiency of HJ solar cells by removing surface contamination of the wafers. We achieved about 16% efficiency in HJ solar cells incorporating intrinsic a-Si:H buffers by dual HWCVD and p/n layers by PECVD.

열선유속계를 이용하여 디이젤 기관 연소실내의 한점에서 유속을 측정한 결과는 다음과 같은 결론을 얻었다. 1. 연소실내의 유동은 cylinder의 원주방향의 속도 성분이 크며, 유속변화는 밸브 timing과 피스톤 속도등에 밀접한 관계가 있다. 2. 유속은 흡입시부터 증가하여 압축행정중 흡입밸브가 닫히는 60˚ABDC에서 최대치를 갖고 이후 피스톤의 속도가 감소함에 따라 유속도 감소하여 팽창행정중 배기 밸브가 열리는 120˚ATDC에서 다시 증가하였다. 3. 평균유속은 shroud 밸브 사용시가 no shroud 밸브 사용시보다 낮지만 shroud 밸브 사용시 흡입행정에서 난류강도가 가장 크게 나타났다. 4. 90˚shroud 밸브 사용시가 120˚shroud 밸브 사용시보다 난류강도는 더 크고, 90˚shroud의 180˚위치에서 난류강도가 제일 크게 나타났다.(이 논문의 결론부분임)