• 설비공학논문집
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• 제10권5호
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• pp.569-580
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• 1998

In this study, condensation heat transfer coefficients(HTCs) of a plain tube, low fin tube, and Turbo-C enhanced tube for CFC-11, HCFC-123, CFC-12, HFC-l34a are measured and compared against each other. All data are taken at the vapor temperature of 39$^{\circ}C$ with a wall subcooling temperature 3~8$^{\circ}C$. Test results show that HTCs of a low vapor pressure refrigerant, HFC-123, for a plain, low fin, and Turbo-C tubes are 10.5~20.5%, 8.2~12.2%, 16.5~19.2% lower than those of CFC-11, respectively. On the other hand, HTCs of a medium vapor refrigerant, HFC-l34a, for a plain, low fin, and Turbo-C tubes are 20.6~31.8%, 0.0~8.0%, 13.2~20.9% higher than those of CFC-12, respectively. For all refrigerants tested, HTCs of Turbo-C tube are the highest among the three tubes showing almost 8 times increase in HTCs as compared to those of a plain tube. Nusselt's prediction equation for a plain tube yielded 12% deviation for all plain tube data while Realty and Katz's prediction equation for a low fin tube yielded 20% deviation for all low tube data.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1107-1112
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• 2006

The purpose of this study is a heat transfer coefficient test of evaporator tube in shell and tube heat exchanger by shapes, using R-404A. The experimental apparatus is designed to simulate the real heat transfer rate in one shell and tube heat exchanger. The test section is formed four type tubes that are Inner ridged tube, Corrugated tube, Turbo-C tube, Inner fin tube and shell type is formed by electrical heater. All tests were performed at a fixed refrigerant evaporator temperature at $1.5^{\circ}C,\;-3^{\circ}C$ and with mass fluxes of 29, 25 kg/hr. Heat transfer rate is calculated a enthalpy difference in test section. In experiment, heat transfer coefficient measured one by one and electrical heaters are supplemented by evaporator.

• 수산해양교육연구
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• 제7권1호
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• pp.31-43
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• 1995

For the fuel saving in the fish farm, the heat transfer performances of various tubes, XL-tube, copper-tube, copper-Nikel-tube and Al-brass-tube, were compared. The XL-tube, which is most commonly used for heating water, showed the poorest heater transfer performance, while the Al-Brass tube shows the best performance. As far as average temperature difference of four tubes concerns, XL-tube is $3.34^{\circ}C$, Copper tube is $10.34^{\circ}C$, Copper-Nikel tube is $11.3^{\circ}C$, Al-Brass-tube is $12^{\circ}C$, The best heat transfer performance of Al-Brass tube results from the enhancement of heat transfer coefficient caused by fin effect and good conductivity of the material.

• Nuclear Engineering and Technology
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• 제51권7호
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• pp.1822-1827
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• 2019

Mechanical responses and failure behaviors of advanced C/C composite tube are very important for structural component design in nuclear reactor. In this study, an experimental investigation was conducted to study mechanical properties of C/C composite tube. Quasi-static compression loading was applied to a type of advanced composite tube to determine the response of the quasi-static load displacement curve during progressive damage. Acoustic emissions (AE) signals were captured and analyzed to characterize the crack formation and crack development. In addition, the crack propagation of the specimens was monitored by imaging technique and failure mode of the specimen was analyzed. FEM is appled to simulate the stress distribution. Results show that advanced C/C composite tube exhibits considerable energy absorption capability and stability in load-carrying capacity.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.657-662
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• 2006

The present paper dealt with an experimental study of condensation heat transfer coefficients with refrigerant R-22, R-407C and R-410A, and was focused on pressure gradient and heat transfer coefficient in horizontal tube-in-tube heat exchangers using inner diameter of 4 mm, 3 mm and 2 mm in a 16.91 mm tube and length of 3,000 mm. Experiments were performed at inlet saturation temperature of 35 to $45^{\circ}C$ and mass flux ranges from 200 to $600 kg/m^2s$. The pressure gradient with inner tube diameter of 4.0 mm is higher 2.5 times than that of 8.0 mm. In tube-in-tube HEX, the pressure gradient of R-410A were lower than those of R-22 and R-407C. The condensation heat transfer coefficients increased with mass flux increase, but they decreased with saturation temperature increased. Condensation heat transfer coefficients of R-410A were a little higher than those of R-22 and R-407C. The condensation heat transfer coefficients of tube-in-tube HEX were about 40% higher than those of double tube HEX.

• 한국콘텐츠학회논문지
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• 제11권9호
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• pp.453-458
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• 2011

본 연구는 C-arm의 각도 변화에 따라 술자의 피폭선량의 변화를 알아보고자 시행 하였다. 실험방법은 101kvp, 4.9mA로 고정하고 조사시간을 3초와 5초로 나누어 시행 하였으며 C-arm Tube를 under와 over로 위치시켜 각각 -30도에서 0, 30, 60, 90도로 변화를 주어 5회 측정하여 평균값을 구하였다. 검출기는 C-arm을 조작하는 방사선사의 위치에서 지면으로부터 160cm의 높이에서 측정하였다. 결과는 -30도에서 측정치가 가장 높았고 0, 30, 60, 90도 순으로 낮았으며 under보다 over tube 방식에서 높았다. 그러므로 방사선사의 피폭선량 저감을 위해서는 over tube 방식보다는 under tube 방식을 사용하고 각도에 변화를 줄 때에는 tube가 술자로부터 멀어지는 각도를 사용하고 가능하다면 조사시간을 단축하는 것이 같은 영상을 만들 수 있으면서도 피폭을 줄일 수 있는 방안이다.

• 동력기계공학회지
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• 제16권5호
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• pp.32-39
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• 2012

The study experimented to understand ice-on-coil type ice making characteristics on to 3 kinds of circular tube, oval tube and small diameter tube using ice maker. The experiment were carried out under various conditions, that used brine temperature($-10^{\circ}C$, $-6^{\circ}C$), brine flow rate(1.0m/s, 1.8m/s) and inlet water temperature ($6^{\circ}C$, $12^{\circ}C$) etc. Mass of ice per ice making area increased according to the decrease of the brine temperature and inlet water temperature, but that was increased according to the increase of the brine flow rate. Oval ice making tube produced ice 1.11 to 2.46 times that of 9mm circular ice making tube, and 3mm small diameter ice making tube produced ice 1.06 to 1.51 times that of 9mm circular ice making tube.

• 대한디지털의료영상학회논문지
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• 제11권1호
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• pp.21-26
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• 2009

In operation room, the use of the C-arm unit is increasing. So, the radiation dose of the person who work in operation room was even more increased than before. Thus, this study is shown the measurement of expose dose and the way for decrease of the radiation dose by using the C-arm unit. The experiment was performed with the C-arm unit and used a phantom which is similar to tissue of the human body and fluoro-glass dosimeter for dose measurement. The expose dose were measured by the tube position(over tube, under tube) of the C-arm unit, distance(50, 100$\sim$200cm), direction(I, II, III, IV), runtime(1min, 3min), wearing of the apron. The radiation dose was decreased twice and three times at under tube rather than over tube. The I direction was measured 20$\sim$30% more than the others. The biggest expose dose is 50cm from center on distance. The expose dose is decreased to far from center. In case of Wearing of the apron, the radiation dose was decreased 60$\sim$90% by the distance. But there weren't change of the radiation dose by C-arm tube position. In present, by increasing the usage of the C-arm unit, the radiation dose is inevitable. So, this study recommends us to use the under tube of the C-arm unit. Also, Wearing of the apron is required for minimum of the radiation exposure.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.712-717
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• 2005

When the weight if a concrete member makes problems, or when the cost of the concrete is relatively high, it may be economical to use a hollow concrete member. But a hollow R.C column may have poor ductility because of the brittle failure at the inner face of the hollow R.C column. This brittle failure results from the absence of the confinement at the inner face of the hollow R.C column. To avoid this brittle failure an internally confined hollow R.C column by a steel tube was developed before. In this study, a hollow R.C column is internally confined by a corrugated steel tube instead of a general flat steel tube. And a column ductility is performed. Test results show that the energy ductility ratio of a internally confined hollow R.C column by a by a corrugated steel tube corresponds to $80\%$ of the energy ductility ratio of a general solid R.C column.

• 한국임상수의학회지
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• 제17권1호
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• pp.138-144
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• 2000

The studies were carried out to investigate the effects of esophageal thermal tube for rewarming in the hypothermia in rabbits. Thiry-one rabbits were continuously cooled with femoral arterio-venous bypass circulation to 25.0${\pm}$0.3$^{\circ}C$(profound hypothermia) of rectal temperature. The experiment was consisted with 3 esophageal thermal tube groups perfused with circulation water at 38${\pm}$1$^{\circ}C$(low, n=12), 42${\pm}$1$^{\circ}C$(medium, n=12), and 45${\pm}$1$^{\circ}C$(high, n=7). Esophageal thermla tube specially constructed double-lumen esophageal tube with circulating warm water at respective htermal grade. With this device, rewarming of the rabbits as follows; High-esophageal thermal tube group(45${\pm}$1$^{\circ}C$)had a more effect on mean arterial pressure(MAP), heart rate(HR), esophageal temperature, and rectal temperature than others groups, but the circulation water at 45$\pm$1$^{\circ}C$ may cause thermal injuries in the esophagus because esophageal temperature increased to 41.1$^{\circ}C$. Medium-esophageal thermal tube group(42${\pm}$1$^{\circ}C$) had a more effect on RR than others groups, but the circulation water at 42${\pm}$1$^{\circ}C$ may also cause thermal injuries in the esophagus if the temperature exceeds 42$^{\circ}C$ for an extended period of time because its esophageal temperature increased to 39.4$^{\circ}C$. Low-esophageal thermal tube group(38${\pm}$1$^{\circ}C$) had a more effect on MAP, RR, and esophageal temperature than others groups. In conclusion, rewarming of the central core in the treatment of profound hypothermia using the esophageal thermal tube perfused with circulation water at 38${\pm}$1$^{\circ}C$ appears to be a ideal alternative safety zone of the temperature of circulation water avoiding thermal injury in esophagus causing by out of order or lower precise thermostat of water bath to that of others groups.