• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.78-82
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• 2003

우주발사체의 2단용 엔진으로 10톤급 케로신 재생 냉각 방식의 액체로켓엔진에 대한 보조 냉각 기구로서, 막냉각을 고려한 냉각특성에 대한 해석적 연구를 수행하였다. 연소기내에서 연소가스의 유동이 축방향으로 층류화되어 있다는 개념하에, 엔진 단면을 서로 독립적인 중심부와 외곽부로 나누며, 외곽부에는 여분의 연료를 분무시킴으로써 연소가스 온도를 낮추어 냉각채널로 전달되는 열유속량과 벽면 온도를 감소시킬 수 있었으며, 엔진의 열적 안정성을 향상시킬 수 있었다.

• 설비공학논문집
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• 제23권8호
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• pp.562-570
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• 2011

In this research, an experimental study is performed to investigate the effects of system operating variables on the cooling and heating characteristics of heat pump system using geothermal heat source and carbon dioxide as a refrigerant. System variables analyzed include compressor frequency, electronic expansion valve opening, refrigerant charge, secondary fluid temperature and flow rate. Results show that optimum refrigerant charge and electronic expansion valve opening position exist at the maximum point of COP curve, and both cooling and heating capacity increase but COPs decrease with the increase of compressor frequency. The change of a secondary fluid temperature leads to variation of overheat area and enthalpy difference in the evaporator and gas cooler. which again results in considerable variations of cooling and heating capacity and COP. In the case of effects of secondary water fluid flow rate, both cooling capacity and COP increase with the increase of secondary flow in evaporator or gas cooler, whereas heating capacity and COP decrease with the increase of flow rate in gas cooler.

• Metals and materials international
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• 제24권6호
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• pp.1422-1431
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• 2018

We investigated the additional (secondary) cooling effect of casted strips on the magnetic properties of Nd-Fe-B sintered magnets. The Nd-Fe-B sintered magnets were fabricated with the casted strips prepared without and with additional cooling. Additional cooling was achieved by blowing Ar gas at various pressures (0.1, 0.3, and 0.6 MPa) on the free-side surface of the strips during the strip-casting process. The higher magnetic properties of $H_c$, $B_r$, and $(BH)_{max}$ of the final Nd-Fe-B sintered magnets were obtained for 0.1 MPa rather than for 0.0 MPa. The best microstructure of the columnar grains in the casted strips was produced with the aid of a lower pressure of gas on the free-side surface. It was found that the microstructure of the strips affects the distribution of grains grown in the sintered magnets. This report demonstrates that the improved magnetic performance of Nd-Fe-B sintered magnets was achieved via additional gas cooling.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3518-3523
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• 2007

An analysis program of specific impulse has been developed for a gas generator cycle rocket engine. The program has been verified by comparing the published performance data of the same cycle engine with RP-1 as fuel. A model for pressure drop of regenerative cooling and film cooling mass flow rate has been suggested to satisfy the necessary cooling condition with Jet-A1 as fuel. The engine mixture ratio is defined by the film cooling mass flow rate and the core mixture ratio. The optimal condition of the combustor pressure and engine mixture ratio has been found for maximum specific impulse.

• 전자공학회논문지 IE
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• 제46권4호
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• pp.25-30
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• 2009

용광로는 외피 부분에 내부 내화물의 온도를 낮추기 위하여 냉각수를 공급하는 냉각판 또는 스테이브를 사용하고 있다. 주변 조업 조건의 열악으로 냉각수를 공급하는 배관의 부식으로 냉각수가 내화물에 침투하여 내화물의 수명을 떨어뜨리고, 노황을 악화시키는 원인이 되고 있다. 이에 본 연구는 용광로 냉각설비장치에 이상 현상이 발생하였을 때 위치를 정확히 확인함에 따라 신속하게 누수된 부위를 파악하여 대처할 수 있는 기능을 갖춘 냉각관 누수 자동감지장치를 개발하였다. 주된 연구는 전자제어 장치인 마이크로프로세서를 응용한 전자변 제어장치를 이용하여 냉각설비의 파손으로 발생되는 누수현상으로 인한 고열과 분진 일산화탄소 등의 산출로 작업환경의 재해를 자동방지 하고자 하였으며, 작업환경이 친환경적이며 작업의 가치를 재창출할 수 있는 방법들이 연구되고 있다. 용광로 분위기의 일산화탄소 자동 감지장치와 그에 따른 출력신호를 자동 전송하는 무선중계기 장치를 개발함으로 용광로 냉각설비 장치의 분위기 작업환경을 수동방식에서 무인자동화방식으로 개선하였다.

• 한국유체기계학회 논문집
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• 제19권4호
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• pp.13-18
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• 2016

The various film cooling hole shapes have been proposed for effective external cooling of gas turbine blade. In this study, the film cooling effectiveness by three different hole shapes (cylindrical hole, $15^{\circ}$ angle anti-vortex hole, 30-7-7 fan-shaped hole) were examined experimentally. Pressure Sensitive Paint (PSP) technique was used to measure the film cooling effectiveness. The coolant to mainstream density ratio was 1.0 and three blowing ratios of 0.5, 1.0, and 2.0 were considered. Results clearly showed that the effect of hole shape on the distribution of film cooling effectiveness. For the cylindrical hole case, the film cooling effectiveness decreased remarkably as the blowing ratio increased due to the jet lift off. Because of large hole exit area and low coolant momentum, the 30-7-7 fan-shaped hole case showed the highest film cooling effectiveness at all blowing ratio, followed by the anti-vortex hole case.

• 수산해양기술연구
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• 제34권3호
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• pp.346-351
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• 1998

The purpose of this study is analyzing the performance of sea water cooling system under various refrigerant pipe length. In sea water cooling system, the increase of refrigerant pipe length cause increases of pressure drops. These pressure drops cause fresh gas in liquid pipe and increase specific volume in gas pipe outlet, so sea water cooling system capacity is decreased by decrease of refrigerant mass flow rate. Sea water cooling system capacity in refrigerant pipe length 70m is decreased more than 30% when compared with pipe length 10m and the decrease of the coefficient of performance is nearly 20%.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.763-764
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• 2012

• 한국주거학회논문집
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• 제17권4호
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• pp.101-109
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• 2006

The purpose of this study was to suggest ways on reducing the cooling and heating energy cost of the officetel building with the multiple glazing windows according to Life Cycle Costing. This study consisted of an hour-by hour energy simulation program and further data from the EnergyPlus V1-2-2 to the four pane type windows that were applied with 2 low-e polyester film and krypton gas to the officetel model building. It was determined that the four panes type windows that had 2 low-e polyester film and krypton gas applied to, them showed a cooling and heating cost reduction over traditional double glazed windows that were filled with air. According to this study, as well as the information from chart 4.5 and the LCC it was determined that the present value of the four panes of windows that had 2 low-e polyester film and krypton gas applied to them showed. a 11.4% reduction in heating and cooling in comparison to the traditional double glazed windows that were filled with air.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권1호
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• pp.19-27
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• 2006

The characteristics of heat transfer and pressure drop have been investigated experimentally during gas-cooling process of carbon dioxide. The results of this study are useful information in the design of a heat exchanger of $CO_2$ refrigerator. The test section consists of 6 series of copper tube, 4.15 and 2.18mm ID, respectively. The inlet temperature, the operating pressure, and the mass flux are varied in the range of $80{\sim}120^{\circ}C,\;{7\sim}10MPa,\;and\;400{\sim}1,900kg/m^2s$, respectively. The heat transfer coefficient of $CO_2$ is affected by temperature, inlet pressure, and mass flux of $CO_2$. At the maximum HTC, the temperature of $CO_2$ nearly accords with the psuedocritical temperature. It is found that the pressure drop is substantially affected by mass flux and inlet pressure of $CO_2$ . The results have been compared with those of previous work. The heat transfer correlation at the gas-cooling process has been also suggested which predicts within the error of 20%.