• Nuclear Engineering and Technology
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• 제25권1호
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• pp.166-177
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• 1993

사용후 핵연료 건식 저장 캐니스터의 핵연료 바스켓 안에 있는 CANDU 37소자 핵연료 다발의 최대 온도를 계산하기 위한 단순화된 열해석 방법과 함께 대기 조건 인자들이 캐니스터 내부의 최대 핵연료 온도에 미치는 영향을 조사하기 위해 수행한 표본 해석 결과를 제시하였다. 3가지 모우드(mode)의 열전달이 공존하는 캐니스터 내부핵연료 다발의 복잡한 기하학적 구조에 대한 다차원열전달 문제를 풀기 위하여 건식저장 캐니스터에 저장된 CANDU 사용후 핵연료 다발들을 등가 및 동심의 핵연료 실린더(cylinder)로 대치하였다. 추가적인 입력 자료 및 열전달 상관식을 이용하여 등가 핵연료 실린더의 단순화된 축대칭, 2차원, 복수 모우드(multi-mode)의 열전달 문제를 기존의 컴퓨터 코드인 HEATING5로 해석하였다. 예측한 온도 분포와 식물 모형 실험 결과의 비교는 만족스러울 정도로 일치함을 보여주고 있다.

• 조명전기설비학회논문지
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• 제22권8호
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• pp.82-88
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• 2008

본 논문은 전해액에 의해 양전극 사이에 형성되는 브리지가 트래킹에 미치는 영향을 기술하고 있다. IEC(International Electrotechnical Commission) 60589의 방법으로 만들어진 1, 3, 5[wt%] NaCl 용액을 이용하여 KS C IEC 60112의 전극에서 트래킹 실험을 하였다. 트래킹 진전과정 중에서 브리지가 형성되었을 때의 전압, 전류, 저항 및 열화상을 측정하여 분석하였다. 그 결과 전해액의 전도율이 커짐에 따라 브리지에서 발생되는 줄열도 커졌다. 하지만 전해액의 기화열로 인해 전해액의 끓는점을 넘지는 못했다. 다만, 전해액의 전도율이 커짐에 따라 건조대 형성에 소요되는 시간이 짧아졌다. 따라서 다음 적하까지 보다 긴 시간동안 건조대를 유지함으로써, 방전 기회가 증가하기 때문에 트래킹 진전이 빨라짐을 알 수 있었다.

• 설비공학논문집
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• 제19권1호
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• pp.1-9
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• 2007

Water condensate accumulated on the surface of a fin-and-tube heat exchanger significantly affects its thermal and hydraulic performance. The purpose of this study is to investigate the effect of condensate retention on the air-side heat transfer performance and flow friction. Total 12 samples of slit and plate fin-and-tube heat exchangers with varying fin spacing and number of tube rows are tested under dry and wet conditions. The thermal fluid measurements are made using a psychometric calorimeter. Frontal air velocity varies in the range from 0.7 m/s to 1.5 m/s. Using the experimental data, presented are the heat transfer coefficients in terms of Colburn j-factor and friction factor.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 추계학술발표회논문집(1)
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• pp.230-235
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• 1996

The new concept of dry area formation based on Poisson distribution of active nucleation sites and the concept of the critical active site density is presented. A simple statistical model is developed to predict the change of slope of the boiling curve up to critical heat flux (CHF) quantitatively. The predictions by the present model are in good agreement with the experimental data. Also it turns out that the present model well explains the mechanism on how the surface wettability influences CHF.

• 대한한방내과학회지
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• 제12권1호
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• pp.98-104
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• 1991

I studied some important medical Literatures in order to examine the cause of Hoarse Voice and found out some facts of follows ; 1. The exogenous cause of disease in wind. 2. Wind-cold, Wind-fire, Wind-heat, Summer-heat, Heat. 3. The endogenous cause of disease is deficiency of Yin and dificiency of blood leads fire-evil was lung-dry stool dificiency of body fluid. 4. The non-exo-endogenous causes of disease is sing ballads and call out.

• 한국조리학회지
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• 제24권1호
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• pp.24-30
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• 2018

This study investigated the quality of characteristics of high-protein RTD coffee using domestic and imported skim milk powder with different heat treatment. Skim milk powders (A, B) had high-heat treatment, C had medium-heat, and D and E had low-heat treatment. The transmittance of A and B were higher than that of C, and that of C were higher than that of D and E (p<0.05). The precipitate attached on bottom of container of RTD coffee using A and B were 2.993~3.053% and higher than those (0.753~0.803%) of RTD coffee using C, D and E (p<0.05), but there was no difference between those of RTD coffee using C, D and E (p<0.05). The centrifuged precipitate of RTD coffee using A and B were 1.987~2.040% and higher than those (0.820~0.830%) of RTD coffee using C, D and E (p<0.05), but there was no difference between those of RTD coffee using C, D and E (p<0.05). The proximate composition of precipitate attached on bottom of container of RTD coffee using A, which showed the highest amount of precipitate, showed 65.7% of carbohydrate, 19.0% of protein, 4.8% of fat and 4.8% of ash in dry basis, that of RTD coffee being 72.7%, 15.1%, 7.9% and 4.3% in dry basis respectively. Protein and fat content of precipitate were lower and protein and ash content were higher than those of RTD coffee. But seeing that the most increased portion was protein, precipitation of RTD coffee appears to be attributed to heat-denatured proteins.

• 설비공학논문집
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• 제8권1호
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• pp.1-12
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• 1996

In lots of application to heat exchanger systems, closed two-phase thermosyphons are tilted from a horizontal. If the tilt angle, especially, is less than 30$^{\circ}$, the operational performances of thermosyphon are highly dependent on tilt angle. The present study was conducted to better understand such operational behaviors as mech-anni는 of phase change, and flow patterns inside a tilted thermosyphon. For experiment, an ethanol thermosyphon with a 35% of fill charge rate was designed and manufactured, using a copper tube with a diameter 19mm and a length 1500mm. Through a series of test, the tilt angle was kept constant at each of 4 different values in the range 10~25deg. and the heat supply to the evaporator was stepwisely increased up to 30㎾/$m^2$. When a steady state was established to the thermosyphon for each step of thermal loads, the wall temperature distribution and vapor temperature at the condenser were measured. The wall temperature distributions demonstrated a formation of dry patch in the top end zone of the evaporator, with a values of temperature 20~4$0^{\circ}C$ higher than the wetted surface for a moderate heat flux q≒20㎾/$m^2$. Inspite of the presence of hot dry patch, however, the mean values of boiling heat transfer coefficient at the evaporator wall were still in a good agreement with those predicted by Rohsenow's formula, which was based on nucleate boiling. For the condenser, the wall temperatures were practically uniform, and the measured values of condensation heat transfer coefficient were 1.7 times higher than the predicted values obtained from Nusselt's film condensation theory on tilted plate. Using those two expressions, a correlation was formulated as a function of heat flux and tilt angle, to determine the total thermal resistance of a tilted thermosyphon. The correlation formula showed a good agreement with the experimental data within 20%.

• 태양에너지
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• 제11권1호
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• pp.69-77
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• 1991

파라핀 왁스에 열에너지를 저장하기 위해 열전달 기구로 원판형 핀이 달린 열싸이폰을 사용하였다. 실험은 4, 6, 8개의 핀에 대해 수행되었으며 각각의 경우 왁스의 초기온도와 주입열량을 변화시키면서 실험을 반복하였다. 실험을 통하여 특히 잠열 축열계의 전열경로의 주요지점에서의 열전달 특성을 규명하고자 하였으며 주요 결론은 다음과 같다. (1) 열싸이폰의 열관류율과 총합열관류율은 핀의 수가 증가함에 따라 커지나 핀과 왁스사이의 열전달계수는 감소하였다. (2) 핀에 의해 열전달이 촉진됨으로서 핀이 없는 열싸이폰에서 일어나는 dry-out 현상이 제거되었다. (3) 수평형의 핀은 왁스의 큰 규모의 대류를 억제하며 핀의 수가 증가함에 따라 핀 사이에서의 국소대류도 더욱 억제되었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.627-632
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• 2006

An experimental study is conducted to investigate the effect of the tube row and fin spacing on the air-side heat transfer and friction characteristics of fin-tube heat exchangers with slit fin pattern. A total of twelve samples of fin-tube heat exchangers with the nominal tube diameter of 7 mm, transverse tube pitch of 19 mm and longitudinal tube pitch of 12.5 mm are tested. The thermal fluid measurements are made using a psychometric calorimeter. The raw data are reduced to the desired heat transfer coefficient in terms of j-factor and friction factor of f for various frontal air velocities, fin pitches and number of tube rows.

• 한국공작기계학회논문집
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• 제14권1호
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• pp.8-14
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• 2005

The purposes of using cutting fluid during cutting have been cooling, lubricating, chip washing, and anti-corroding. However, the present manufacturing industry restricts the use of cutting fluid because cutting fluid contains poisonous substances which are harmful to the human body. Therefore dry cutting becomes an unavoidable assignment and a lot of researches have studied cutting methods without using cutting fluid. Because dry turning is a continuous work, tools life is reduced by continuous heat generation and surface gets rough due to reduced lubrication, so it is important to consider these situations. In this paper, the way of selecting the optimal machining condition by the minimum number of experiments and the effectiveness of using compressed air in high hardness materials through Taguchi method have been found. Dry cutting using compressed air showed better cutting characteristics than normal dry cutting with respect to by cutting force, tool wear, and surface roughness. Also, the optimal machining condition f3r dry cutting using compressed air could be selected through Taguchi method.