• 한국지하수토양환경학회지:지하수토양환경
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• 제8권2호
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• pp.1-8
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• 2003

Chlorofluorocarbons(CFCs) 조사를 위한 지하수 시료 채취 방법 중 cold-welded copper tube method(구리관법)과 flame-sealed borosilicate glass ampule method(유리앰퓰법)의 두 방법을 비교하고 검토하였다. 구리관법에 의해 채취된 시료의 CFCs 농도는 중복시료간에 재현성이 불량한 반면, 유리앰퓰법은 상대표준오차가 5％ 이내로 좋은 재현성을 보여주었다. 이것은 구리관법을 적용할 때, 관정의 출수구와 구리관의 연결의 밀봉성이 좋지 않았기 때문인 것으로 추정된다. 또한 구리관법에 의한 CFCs 농도는 전체적으로 유리앰퓰에 의한 값보다 높았으며 이러한 특징은 CFC-11이 CFC-12보다 더 두드러졌다. 구리관법의 경우에 플라스틱 관이나 관정에 설치된 출수구에 포함된 고무 패킹 등이 시료를 CFCs로 오염시켰을 것으로 평가된다. 유리앰퓰법을 적용했을 때에는 이러한 가능성을 제거하기 위해 stainless steel과 nylon 재질만을 이용하고, 시료채취장비를 관정의 주배수관에 직접 연결하였다. 인위적인 공급원에 의한 CFCs가 없을 것으로 예상되는 시료에서 유리앰퓰법에 의해 매우 낮은 수준의 CFCs농도가 측정됨으로써 이 시료채취과정의 유효성이 검증되었다.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.530-537
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• 2020

This study investigates the effect of an included angle and heat flux on heat transfer of V-shape tube array having a horizontal upper tube. The test uses two stainless steel tubes with a smooth surface submerged under the water at atmospheric pressure. The angle varies from 2° to 24°. The heat transfer coefficient gets decreasing in consequence as the angle increases. The enhancement due to the lower tube is distinct as the heat flux is lower than 60 kW/㎡, where the effect of the convective flow is dominant. The present study and the published results show a similar tendency. Although the heat transfer coefficient for the present study is smaller than the symmetry case, enhanced heat transfer is observed compared to the tube array having a lower horizontal tube as the included angle is less than 10°.

• 설비공학논문집
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• 제13권9호
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• pp.845-852
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• 2001

The phenomena of energy separation in vortex tubes was investigated experimentally to see the effects of the conductivity of a tube and convective heat transfer on the outer surface of a tube. The experiment was carried out with different conductivity (pyrex, stainless steel and copper) of a tube and three kinds of convective heat transfer modes (adiabatic condition, natural convection (air) and forced convection (water) on the outer surface of a tube. the results were obtained that hot exit fluid temperature was highly affected by a change of conductivity of a tube when the outer surface was cooled by the forced convection of water. However, the cold exit temperature was little affected by heat transfer modes on the outer surface in vortex tubes.

• Journal of Welding and Joining
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• 제8권4호
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• pp.27-34
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• 1990

Integranular corrosion behaviors of KAL (Knife Line Attack) and mechanical properties such as tensile and creep rupture were investigated for the tube material used for nearly 20 years under the condition of 463.deg. C and 28 $kg/cm^2$. Based and weld metal were austenitic stainless steel AISI 321 containing Ti, AISI 347 containing Nb, respectively. KLA is a kind of the intergranular corrosion which often occurs just near the HAZ (heat affected zone) of AISI 321 and AISI 347 stainless steel due to the grain boundary sensitization. In KLA zone, intergranular corrosion crack has propagated outwards from the inner surface and carbides of white and narrow band type assuming as (Cr, Fe) carbide were confirmed. All the delta-ferrite formed in the weld metal during weld solidification has been transformed into sigma-phase since delta-ferrte was exposed for 20 years at 463.deg. C. Elongation was very low at the range from room temperature to 600.deg. C and it was confirmed that creep-rupture properties were not consideralbly affected.

• Journal of Mechanical Science and Technology
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• 제15권11호
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• pp.1533-1540
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• 2001

A high-temperature sodium stainless steel heat pipe was fabricated and its performance has been investigated. The working fluid was sodium and it was sealed inside a straight tube container made of stainless steel. The amount of sodium occupied approximately 20% of the total volume of the heat pipe and its weight was 65.7gram. The length of a stainless steel container is 1002mm and its outside diameter is 25.4mm. Performance tests were carried out in a room air condition under a free convective environment and the measured temperatures are presented. The start-up behavior of the heat pipe from a frozen state was investigated for various heat input values between 600W and 1205W. In steady state, axial temperature distributions of a heat pipe were measured and its heat transfer rates were estimated in the range of vapor temperature from 50$0^{\circ}C$ to 63$0^{\circ}C$. It is found that there are small temperature differences in the vapor core along the axial direction of a sodium heat pipe for the high operating temperatures. But for the range of low operating temperatures there are large temperature drops along the vapor core region of a sodium heat pipe, because a small vapor pressure drop makes a large temperature drop. The transition temperature was reached more rapidly in the cases of high heat input rate for the sodium heat pipe.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2002년도 High Temperature Superconductivity Vol.XII
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• pp.33-33
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• 2002

• 광물과 암석
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• 제36권4호
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• pp.337-343
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• 2023

감람석은 철감람석과 마그네슘감람석의 완전고용체로서 암석형 행성, 운석, 소행성, 행성간 먼지 등에 풍부하게 함유되어 있다. 감람석은 조성범위가 매우 넓기 때문에 감람석 함유 시료의 광물정량분석을 위해서는 다양한 조성의 감람석 표준물질을 구비해야 한다. 감람석 표준물질을 전기로와 스테인리스강관을 이용하여 1000~1100 ℃ 범위의 온도에서 합성하였다. 엑스선회절분석에 의하면 시료에 따라 합성불순물과 미반응물이 있으나 전반적으로 전조성 범위를 포함하는 감람석이 합성되었다. 합성 감람석들은 출발물질의 철감람석 몰비에 비례하여 단위포 치수가 선형으로 증가하는 경향을 보였으며, 회절강도도 자연산 감람석과 부합하였다. 그러나 철 함량이 높은 합성 감람석에서 불순물 함량이 증가하는 경향이 있어 아직 모든 합성 감람석을 표준물질로 사용할 수 없으며, 출발물질의 고순도화, 반응시간 및 온도 조절 등의 합성과정 개선이 필요하다.

• International Journal of Air-Conditioning and Refrigeration
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• 제10권3호
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• pp.138-146
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• 2002

The phenomena of energy separation in vortex tubes was investigated experimentally to see the subsidiary effect of the conductivity of tube material and cooling conditions around the outer surface of the tube. The experiment was carried out with pyrex, stainless steel and copper tubes, and the heat transfer conditions of the tubes were with insulation, without in-sulation and water cooling modes respectively The results were obtained that the hot exit fluid temperature was highly affected by a change of conductivity of a tube when the outer surface was cooled by the water, while the working fluid through the tubes was air. How-ever, the cold exit temperature was little affected by the heat transfer modes on the outer surface of the vortex tube.

• Advances in Energy Research
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• 제8권3호
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• pp.155-163
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• 2022

The current study presents experimental research on a parabolic trough collector with tube and cavity receivers. The primary concentrating parabolic reflector is designed for an aperture area of 2×2 m² with mirror-polished stainless steel sheet reflectors. The cavity receiver consists of a compound parabolic secondary reflector and a copper tube. Both the conventional tube receiver and the cavity receiver tube are coated with black powder. The experiments are carried out to compare the efficiency of the cavity receiver with the tube receiver for fluid temperature rise, thermal efficiency, and overall losses. The experiments showed significantly higher fluid temperature rise and overall efficiency and lower thermal losses for the cavity receiver compared to the tube receiver within the parameters explored in this study.

• 비파괴검사학회지
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• 제28권4호
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• pp.339-345
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• 2008

원자력발전소 열교환기 튜브의 대부분은 구리, 티타늄, 인코넬합금 등의 비자성체로 제작되어 있으나 2차 터빈계통의 습분분리재열기(moisture separator & reheater), 급수가열기 등의 튜브는 고압, 고온 등의 열악한 운전조건에서 상대적으로 고온 강도가 우수한 탄소강 또는 페라이트계열 스테인레스강 등의 자성체로 제작되어 있다. 특히 습분분리재열기 튜브와 같은 열교환 매체가 증기인 경우 열전달 능력을 증가시키기 위해서 핀 튜브를 사용한다. 탄소강 또는 페라이트계열 스테인레스강 등의 자성체 튜브는 고온, 고압에서 강도가 우수하지만 운전 중에 증기 커팅, 침식, 기계적 진동 마모, 응력부식균열 등의 사용 중 결함이 발생하여 발전소 정상운전에 지장을 초래할 수 있기 때문에 전열관의 건전성 평가를 위한 주기적인 비파괴검사의 수행이 필요하다. 하지만 자성체 열교환기 튜브는 투자율이 높은 전기적 특성으로 인하여 기존의 와전류검사기술로는 비파괴검사가 어렵기 때문에 원격장검사기술을 적용해야 한다. 따라서 본 연구에서는 원자력발전소 습분분리재열기세관의 현장적용에 필요한 검사기술을 개발하기 위해서 원격장탐촉자, 인공결함 시험편 및 탐촉자 구동장치를 설계하였으며, 이를 활용하여 발전소 현장 검사에 적용하였다.