• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.294-295
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• 2018

유도가열은 전자기 유도 현상을 이용하여 금속체를 직접 가열하는 방식이며 높은 변환 효율로 전기에너지를 열에너지로 변환할 있다. 이로 인해 금속의 단조, 용해, 표면경화, 풀림 등 여러 응용분야를 통해 철강 및 기계 산업에 기여하고 있다. 단조용 유도가열기 전원장치는 높은 전력용량을 사용하여 주로 SCR을 이용한 위상제어 정류기를 적용한다. 하지만 입력단의 저 역률 및 전류의 THD가 높은 단점을 가진다. 따라서 본 논문에서는 이러한 단점을 보안하기 위해 단조용 유도가열 작업에 맞는 인터리브드 방식의 벅 컨버터와 전류원 인버터를 사용한 고효율 유도가열 전원장치를 제안한다.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.638-644
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• 2010

Numerical predictions of a fully developed turbulent flow through a square duct ($30mm{\times}30mm$) with twisted tape inserts and with twisted tape plus interrupted ribs are respectively conducted to investigate regionally averaged heat transfer and flow patterns. A rib height-to-channel hydraulic diameter(e/$D_h$) of 0.067 and a lengthto-hydraulic diameter(L/$D_h$) of 30 are considered at Reynolds number ranging 8,900 to 29,000. The interrupted ribs are axially arranged on the bottom wall. The twisted tape is 0.1 mm thick carbon steel sheet with diameter of 28 mm, length of 900 mm, and 2.5 turns. Each wall of the square channel is composed of isolated aluminum sections. Two heating conditions are investigated for test channels with twisted tape inserts and rib turbulators: (1) electric heat uniformly applied to four side walls of the square duct, and (2) electric heat uniformly applied to two opposite walls of the square channel. The results show that uneven surface heating enhances the heat transfer coefficient over uniform heating conditions, and significant improvements can be achieved with twisted tape inserts plus interrupted ribs.

• Journal of Power System Engineering
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• v.15 no.3
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• pp.31-37
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• 2011

직조 금속 스크린 리브(rib) 이 바닥에 설치된 사각 덕트에서 열전달과 유체유동의 압력강하를 측정하기 위해 실험적 연구를 수행하였다. 시험부의 치수는 200 mm(W) ${\times}$ 40 mm(H) ${\times}$ 712 mm(L)이고 수력직경은 66.6 mm이다. 입구영역에는 1.72m 길이의 가열되지 않은 동일한 치수의 채널을 설치하였다. 메쉬가 다른 4가지의 직조금속 스크린 리브에 대해 측정하였다. 그리고 비교를 위해 일체형 리브에 대해서도 측정하였다. 국부 열전달 계수의 측정에는 스테인레스 강제 포일(foil) 히터와 T형 열전대률 이용하였다. 레이놀즈 수는 23,000에서 58,000의 범위이다. 덕트의 수력직경($D_h$)에 대한 직조 금속 리브의 높이(e)의 비($e/D_h$)는 0.075 이고 리브 간격(p)과 높이의 비(p/e)는 10이다. 실험 결과 메쉬가 없는 일체형 리입에서 가장 누셀트 수와 마찰계수가 컷다.

• Proceedings of the Korean Society of Food and Cookery Science Conference
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• 2003.10a
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• pp.83-83
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• 2003

대두유, 올리브유 및 채종유에 대한 정향추출물(clove extract)의 항산화 효과를 알아보고자 대두유, 올리브유 및 채종유에 정향추출물을 0.02%의 농도로 첨가한 후 180$\pm$2$^{\circ}C$에서 48시간동안 가열산화 시키면서 산가(acid value) 및 공액이중산가(conjugated diene value)를 측정하였다. 대두유, 올리브유, 채종유의 초기 산가는 0.13, 0.75, 0.11이었으며, 가열산화 후 0.52, 1.31, 0.51로 증가하였다. 또한 대두유, 을리브유, 채종유의 초기 공액이증산가는 0.57, 0.43, 0.35에서 가열산화 후 1.93, 1.04, 1.08으로 대두유보다 채종유나 올리브유의 산화안정성이 높았다. (중략)

• Journal of the Korea Institute of Building Construction
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• v.23 no.5
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• pp.509-517
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• 2023

The surge in FRP(Fiber Reinforced Plastic) research signifies the industry's pursuit to counteract the longstanding issue of rebar corrosion. Notably, Carbon Fiber Reinforced Plastic(CFRP) emerges as a commendable alternative, given its superior resistance to both corrosion and chemical interactions, thus positing itself as a potential replacement for traditional steel rebars. However, the layered composition of fibers and resin in CFRP flags a notable susceptibility to elevated temperatures. Despite its promise, comprehensive studies elucidating the full spectrum of CFRP properties remain ongoing. In this investigative study, we meticulously assessed the bond strength of CFRP post-exposure to high thermal conditions. Our findings underscored a parity in bond strength amongst silica sand-coated CFRP, rib-type CFRP, and Glass Fiber Reinforced Plastic(GFRP).

• Journal of Korean Society of Steel Construction
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• v.28 no.1
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• pp.23-34
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• 2016

Concrete filled steel tube system has two major advantages. First, the confinement effect of steel tube improves the compressive strength of concrete. Second, the load capacity and deformation capacity of members are improved because concrete restrains local buckling of steel tube. It does, however, involve workability problem of using stud bolts or anchor bolts to provide composite effect for larger cross-sections. While the ribs inside the columns are desirable in terms of compressive behavior, they cause the deterioration in load capacity upon in-plane deformation resulting from thermal deformation. Since the ribs are directly connected with the concrete, the deformation of the ribs accelerates concrete cracking. Thus, it is required to improve the toughness of the concrete to resist the deformation of the ribs. Welding built-up tubular square columns can secure safety in terms of fire resistance if the problem are solved. This study focuses on mixing steel fiber in the concrete to improve the ductility and toughness of the columns. In order to evaluate fire resistance performance, loaded heating test was conducted with 8 specimens. The behavior and thermal deformation capacity of the specimens were analyzed for major variables including load ratio. The reliability of heat transfer and thermal stress analysis model was verified through the comparison of the results between the test and previous study.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2277-2288
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• 1996

This study was performed to analyze the cooling effect of heated ribs which are frequently used for cooling of electronic parts, using the numerical method. To prevent the excessive pressure drop due to turbulence promoters for the enhancement of heat transfer rate especially, the effect of the angle of turbulence promoter was investigated by the numerical analysis. Heat transfer rate with turbulence promoters with rectangular cross-section increased by 13% in average, but the coefficient of pressure drop increased by 1.68 times than that without them. In the present study, triangular cross-sectional shape turbulence promoters were suggested and numerically tested. Pressure drop of turbulence promoter with the 30 degree triangular cross-sectional shape decreased by 30% from that of rectangular cross-section promoters while heat transfer rate was almost the same. While with 4 turbulence promoters, the heat transfer rate increased by 21%, the pressure drop increased 4 times. It means that the higher capacity of cooling fan should be needed. With the triangular cross-sectional shape, the size of vortex region at the rear of promoters became considerably smaller, so pressure drop became smaller. The effect of the change of cross-sectional shape was not found in the flow pattern near the ribs, so that heat transfer characteristics in the ribs were not changed.