• 대한기계학회논문집B
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• 제29권7호
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• pp.805-813
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• 2005

The thermal performance of a flat-strip heat pipe with inner grooves and the screen mesh cover was investigated experimentally. The heat pipes were made of 2024 aluminum alloy of which the dimensions were 30 (W) $\times$ 4 (T) $\times$ 150 (L) mm. The cross sectional dimensions of inner groove were 0.4$\times$0.9 mm and the space between grooves was 0.6 mm. To enhance the capillary force, foe screen meshes were attached to cover the grooved inner surface. In the grooved heat pipes without screen mesh cover, the maximum thermal load of 180 W (12 W/$cm^2$) was achieved for operating temperature below $130^{\circ}C$ at horizontal position. The heat pipes with screen mesh cover showed the thermal resistances less than one third of those without screen mesh cover, and showed less fluctuation in the thermal resistance values. Furthermore, the thermal performance of the former exhibited less dependence on the tilt angle and the fill charge ratio.

• 한국해양공학회지
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• 제26권6호
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• pp.66-73
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• 2012

A pressure compensated chamber of a pilot mining robot isolates and protects an electrical-electronic system from the ambient highly pressured water. Since the inner pressure of the chamber is compensated with outer water pressure using hydraulic oil and pressure compensator, there exists a pressure difference, less than 1 bar, between outer and inner surface. The structural safety of the chamber is obtained relatively easier than the canister type which inner pressure is kept as the atmospheric pressure. However, due to the adoption of box shape for space efficiency and usage of the transparent engineering plastic viewport for checking inner circumstance, the viewport can be largely deformed. This large deformation can cause an additional tensile force, called the prying force, to the bolt-flange connection parts of the viewport. In this paper, we suggest the structural design equation considering the prying action for designing the structure of a box-shape pressure compensated chamber.

• 환경위생공학
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• 제18권3호통권49호
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• pp.27-34
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• 2003

An objective of local exhaust hood design is to design the hood to operate as efficiently as possible. The greatest loss normally occurs at the entrance to the duct, due to the vena contracta in the throat of the duct. This can be accomplished by minimizing the loss that results from the vena contracta. There have been little studied to be cost-effective approach as installing simple instrument inside the throat of the hood. The aims of this paper were to minimize entry loss using inner square, and to measure the effect of inner square when installed inside hood throat. The results of this study were as follows; First, the magnitude of vena contracta could be considered as the difference between direct measured velocity and calculated velocity, which is from Bernoulli theory. In circle hood, calculated velocity and direct measured velocity were 10.7m/sec and 10.3n/sec, respectively. And the calculated velocity and direct measured velocity in square hood were 7.7m./sec and 6.5m/sec, respectively. Second, effect of inner square by width was carried out. The widths of inner square were L/1(18cm), L/2(9cm), L/3(6cm) and L/6(3cm). In case inner square was installed with 3cm width, the entry of coefficient was 0.93, comparing with 0.85 of entry of coefficient of general hood. Third, effect of inner square by distance from hood inside surface to inner square was carried out. The distances were L/3(6cm), L/6(3cm), L/9(2cm) and L/l8(1cm). In case the distance was 3cm the best efficiency was shown (Ce= 0.93). Fourth, effect of inner square by location from hood entry to duct inside was carried out. The locations of inner square were entry(0cm), L/6(3cm), L/3(6cm), L/2(9cm) and L/l(12cm). In case the location was 0cm, 3cm and 6cm the entry of coefficients were 0.93, 0.92 and 0.90, respectively.

• 대한기계학회논문집B
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• 제38권11호
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• pp.943-950
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• 2014

본 연구는 다양한 위치의 원형 실린더가 존재하는 사각 밀폐계에서 Prandtl 수 변화에 따른 밀폐계 내부의 자연대류 현상에 대한 수치해석을 수행하였다. Rayleigh 수가 $10^3$, $10^4$, $10^5$ 그리고 다양한 위치의 내부 원형 실린더에 대해서 Prandtl 수를 0.1, 0.7, 7 로 변화시키며 Prandtl 수의 영향을 분석하였다. 내부 원형 실린더의 위치는 -0.2 에서 0.2 까지 0.1 간격으로 변화시켰다. Prandtl 수의 변화에 따른 밀폐계 내부의 자연대류 현상은 밀폐계 내부의 온도장과 유동장 및 표면 평균 Nusselt 수의 분포를 바탕으로 분석하였다. Rayleigh 수가 $10^5$ 일 때 내부 실린더의 위치에 상관없이 Prandtl 수가 증가할수록 평균 Nusselt 수는 증가하였다.

• 박물관보존과학
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• 제25권
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• pp.1-8
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• 2021

국립중앙박물관 소장품 청화백자투각연당초팔괘문연적(수정147)을 대상으로 CT 조사를 실시하고 복제품을 제작하여 구조와 제작방법에 대해 살펴보았다. CT 조사를 실시한 결과, 접합선이나 기공이 없는 것으로 보아 하부 동체부 틀을 사용하여 한 번에 찍어 빼낸 후 상부 틀로 찍어 뽑아낸 상부 뚜껑을 서로 접합하였음을 알게 되었다. 특히 하부 동체부의 내기 상면과 연접한 뚜껑 하단면이 서로 접합이 잘 되도록 내면 가운데를 대나무 칼로 거칠게 돌려 깎아 접합면이 누수 되지 않도록 처리하였다. 처음 제작할 당시 물을 담는 연적의 내기(內器)는 도량형 규격에 맞고 틀을 뽑아내기에도 용이한 원통형(圓筒形)으로 만들었을 것으로 짐작되나 상부면과 동체부를 붙이는 과정에서 형태가 사다리꼴로 변형되었을 것으로 여겨진다. 또한 실리콘 복제를 이용하여 원통형 내기로 다시 제작한 후 내기의 용량을 비교 측정한 결과, 3D프린팅을 이용해 복제한 유물 내기의 용량이 152.5㎖인데 반해 원통형 내기의 용량은 대략 168.6㎖로 조선시대 도량형 기준인 '량(量)'의 단위로 3홉(약 174㎖)과 유사하다는 것을 확인 할 수 있었다. 원통형 내기의 용량이 조선 후기 도량형 기준과 부합하므로 실제 도공이 팔괘문연적을 제작할 당시 원통형내기를 가진 연적으로 제작하였을 것으로 생각된다.

• 한국해양학회지:바다
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• 제24권4호
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• pp.519-534
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• 2019

여름철 인공호수(간월호, 부남호)로 부터의 담수방류시 천수만 수질(영양염, 유기물, 미량금속)에 미치는 영향을 평가하기 위해 2011년 6, 7, 8, 10월에 평상시와 담수방류 시기 각 2회씩의 해수를 채취하였다. 담수가 방류되면 용존 무기 질소(DIN)의 농도가 만내의 모든 수층에서 약 3-4배 증가하였고, 평상시 암모니아성 질소(NH₄⁺-N)가 우세하다가 담수방류시 질산성 질소(NO₃^--N)가 우세하였다. 용존 무기인(DIP)의 경우 내만 표층에서 절반으로 감소하였고 저층에서는 1.5배 증가하였으며 규산염(Si(OH)₄)은 내만 저층에서 2배 증가하는 모습을 보였다. Redfield ratio는 담수 방류시 인 제한 환경으로 바뀌었다. 용존 유기 탄소(DOC) 및 질소(DON)는 약 2배 증가하였고, 입자상 유기 탄소(POC), 질소(PON), 인(POP) 및 생물기원 규소(Bio-SiO₂)는 내만 표층에서 약 2배 이상 증가했다. 용존 금속(Fe, Co, Ni, Cu)은 내만의 표층에서 증가하였으나, 용존 Cd의 경우 만의 표층에서 절반으로 감소하였다. 이와 같은 결과로 미루어 볼 때 영양염, 유기물 및 금속 농도가 높은 인공호수의 물이 만으로 유입되면, 천수만 내의 영양염 및 용존 유기물, 금속농도가 증가하고, 식물플랑크톤 대증식이 발생하여 표층에서 산소 과포화, 저층에서 빈산소를 발생시킨다. 빈산소와 함께 내만의 저층에서는 매우 높은 농도의 영양염(DIN, DIP, Si(OH)₄) 농도가 존재하였다. 수질 평가 지수값을 통해 천수만의 부영양화 정도를 평가한 결과, 평상시에는 3등급 이하로 나타나다가 방류시 5등급으로 바뀌게 됨을 알 수 있었다.

• 한국항공우주학회지
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• 제32권8호
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• pp.54-63
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• 2004

2002년 11월 28일 발사된 KSR-III 과학로켓에서 공력가열로 인한 온도상승을 측정하였으며, 로켓 외피의 온도 및 공력가열량을 계산하였다. 계산에 사용된 소프트웨어는 이론식에 기초한 경계층을 해석하여 비행시간동안 비정상 공력가열량을 계산하는 MINIVER 코드이며, 비행체 내부로의 일차원 고체 열전도까지 고려하였다. 계산 결과 비행체 내부 페이로드 장착부분의 열전달은 대부분 복사로 이루어지고, 공력가열로 인한 KSR-III 외피 최고온도는 핀에서 $223^{\circ}C$이며 최대 공력가열은 노즈캡에서 $133kW/m^2$이었다. 중요부분에서 재질의 허용온도를 만족하였으며 외피 단열재 설계가 적절히 이루어졌음이 확인되었다.

• 한국도로학회논문집
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• 제17권2호
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• pp.31-37
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• 2015

PURPOSES : To design a pre-heater for warm in-place recycling equipment, three different heating systems were evaluated to determine their thermal efficiency. METHODS: In this study, a $30cm{\times}30cm{\times}15cm$ wheel-tracking specimen was used to measure the inner temperature as a function of the heating system. The inner temperature of the specimen was measured with a data logger at the surface, and at depths of 1cm, 2cm, 3cm, 4cm, and 5cm. To evaluate the thermal efficiency, the researchers used three different types of equipment, namely, IR, a heating wire, and a gas burner. RESULTS: The IR heating system exhibits a higher level of performance than the others to achieve the target temperature at a depth of 5cm in the specimen. The gas burner system was capable of heating the surface to a temperature of up to $600^{\circ}C$. The other types, however, cannot heat the surface up to 600. The thermal efficiencies were measured based on the laboratory conditions. CONCLUSIONS: To find the most effective system for application to the development of a pre-heater for warm in-place recycling, various systems (IR, heating wire, gas burner) were examined in the laboratory. As a result, it was found that the hot plate of a gas burner system provides the highest temperature at the surface of the asphalt but, of all the systems, the IR system provides the best internal temperature increase rate. Furthermore, a gas burner can age the asphalt binder of the surface layer as a result of the high temperature. However, the gas burner cannot attain the target temperature at 5cm. The IR system, on the other hand, is effective at increasing the internal temperature of asphalt.

• Journal of Mechanical Science and Technology
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• 제19권4호
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• pp.1044-1051
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• 2005

The isothermal characteristics of a rectangular parallelepiped sodium heat pipe were inves­tigated for high-temperature applications. The heat pipes was made of stainless steel of which the dimension was $140\;m\;(L)\;{\times}\;95m\;(W)\;{\times}\;46 m\;(H)$ and the thickness of the container was 5 mm. Both inner surfaces of evaporator and condenser were covered with screen meshes to help spread the liquid state working fluid. To provide additional path for the working fluid, a lattice structure covered with screen mesh wick was inserted in the heat pipe. The bottom surface of the heat pipe was heated by an electric heater and the top surface was cooled by circulating coolant. The concern in this study was to enhance the temperature uniformity at the bottom surface of the heat pipe while an uneven heat source up to 900 W was in contact. The temperature distribution over the bottom surface was monitored at more than twenty six locations. It was found that the operating performance of the sodium heat pipe was critically affected by the inner wall temperature of the condenser region where the working fluid may be changed to a solid phase unless the temperature was higher than its melting point. The maximum temperature difference across the bottom surface was observed to be $114^{\circ}C$ for 850 W thermal load and $100^{\circ}C$ coolant inlet temperature. The effects of fill charge ratio, coolant inlet temperature and operating temperature on thermal performance of heat pipe were analyzed and discussed.

• 한국표면공학회지
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• 제48권6호
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• pp.260-268
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• 2015

The thermal barrier coating (TBC) for inner wall of liquid-fuel rocket combustor consists of NiCrAlY as bonding layer and $ZrO_2$ as a top layer. In most case, the plasma spray coating is used for TBC process and this process has inherent possibility of cracking due to large difference in thermal expansion coefficients among bonding layer, top layer and metal substrate. In this paper, we suggest crack-free TBC process by using a precise electrodeposition technique. Electrodeposited Ni-P/Cr double layer has similar thermal expansion coefficient to the Cu alloy substrate resulting in superior thermal barrier performance and high temperature oxidation resistance. We studied the effects of phosphorous concentrations (2.12 wt%, 6.97 wt%, and 10.53 wt%) on the annealing behavior ($750^{\circ}C$) of Ni-P samples and Cr double layered electrodeposits. Annealing temperature was simulated by combustion test condition. Also, we conducted SEM/EDS and XRD analysis for Ni-P/Cr samples. The results showed that the band layers between Ni-P and Cr are Ni and Cr, and has no formed with heat treatment. These band layers were solid solution of Cr and Ni which is formed by interdiffusion of both alloy elements. In addition, the P was not found in it. The thickness of band layer was increased with increasing annealing time. We expected that the band layer can improve the adhesion between Cr and Ni-P.