• 한국화재소방학회논문지
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• 제24권6호
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• pp.76-81
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• 2010

노말헵탄의 안전한 취급을 위해서 $25^{\circ}C$에서 폭발한계와 폭발한계 온도의존성 그리고 하부인화점을 고찰하였다. 또한 발화지연시간에 의한 발화온도를 측정하였다. 공정의 안전을 위해서 노말헵탄의 폭발하한계는 1.0Vol%, 상한계는 7.0Vol%를 추천하였고, 하부인화점은 $-4^{\circ}C$를 추천하였다. ASTM E659-78 장치를 사용하여 발화온도와 발화지연시간을 측정하였고, 여기서 측정된 최소자연발화온도는 $225^{\circ}C$였다. 그리고 노말헵탄의 새로운 폭발한계 온도의존식을 제시하였으며, 제시된 식은 문헌값과 일치하였다.

• 한국분무공학회지
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• 제13권3호
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• pp.149-155
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• 2008

An experimental study was performed to understand spray characteristics of the rotary atomizer for the slinger combustor. In this fuel injection system, fuel is injected and atomized in the combustor by centrifugal forces to engine shaft. The experimental apparatus consists of a high speed rotational spindle, rotary atomizer, pressure tank and acrylic case. The droplet size and velocity were measured by PDPA (phase Doppler particle analyzer), and spray was visualized by using high speed camera and Nd:Yag laser-based flash photography. From the test results, the droplet size (SMD) is largely affected by rotational speed, mass flow rate and the number of orifice. As the experimental results, we could understand the spray characteristics of the rotary atomizer for the slinger combustor and obtain the optimum shape of the rotary atomizer which is suitable for the small gas turbine engine.

• 기술사
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• 제43권6호
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• pp.31-34
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• 2010

Recently, due to localized heavy rain and flash floods in urban areas is becoming more frequent flood damage. To prevent flood inundation damage, to formulate the diverse directions in connection with the drainage system of buildings, roads, sewerage, pump stations, detention (retention) pond, and streams is very important. In addition, it is important for the uniform design criteria, the consistent of hydrologic and hydraulic analysis method, and a flood disaster mitigation systems connected with structural and nonstructural measures. To accomplish this, the method such as installation of storage facilities, infiltration facilities, and underground water tank, the optimal size of the design gutter and grate of the road, ensure the capacity of pumping stations, and the installation of a flood control channel into the deep underground requires comprehensive measures dimension in urban areas.

• 설비공학논문집
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• 제17권11호
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• pp.1005-1013
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• 2005

The use of river water as a heat source of a heat pump has the advantage in the performance compared to the use of atmospheric air because the temperature variation of river water over the year is relatively small. In this study, the performance of the heat pump system using river water as a heat source was numerically investigated. A simulation model for the 2-stage compression heat pump system was developed with each component model composed of compressors, heat exchangers, a flash tank and electronic expansion devices. The peformance of the heat pump system using river water was improved by $50\%$ compared to that using atmospheric air in winter conditions.

• 설비공학논문집
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• 제24권5호
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• pp.377-384
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• 2012

Vapor injection technique has been applied to prevent performance degrdation of a heat pump at low ambient temperatures. In this study, the heating performance of a heat pump with a variable speed injection scroll compressor using R-410A was investigated by applying sub-cooler vapor injection(SCVI) and flash tank vapor injection(FTVI). The heating performance of the heat pump was measured by varying compressor frequency and outdoor temperature. The heating capacity of the FTVI system was 8~10% higher than that of the SCVI system at all operating conditions. On the other hand, the heating performance improvement with the increase in the compressor frequency was more prominent in the SCVI system than in the FTVI system.

• 한국유체기계학회 논문집
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• 제10권2호
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• pp.16-21
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• 2007

Potential advantages of using vapor injection in a two stage rotary compressor for a $CO_2$ heat pump water heater system were addressed in this paper by numerical simulation. Vapor separated from a flash tank in the middle of the expansion process can be used for injection into the second stage suction plenum of the compressor to improve the system performance. Vapor injection increases the intermediate pressure between the two stages, thus increasing the first stage compressor work and reducing that of the second stage. As a whole, however, the compressor input power increases due to injected mass flow rate for the second stage. Computer simulation showed that increment of the cooling capacity by vapor injection exceeded that of the compressor work, thus improving the system performance. COP improvement by vapor injection was calculated to be about 5-14% for normal operating conditions. With vapor injection, a maximum COP was found when the displacement volume of the second stage becomes 90-95% of that of the first stage of the compressor.

• 전기학회논문지P
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• 제64권4호
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• pp.236-240
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• 2015

Natural ester has a higher biodegradability, flash and fire points, and a greater permittivity compared to conventional mineral oils. However, natural ester also has a higher pour point, viscosity, and water content. These characteristics hamper circulation and the electrical properties of oil-filled transformer. Thus, this paper applied electromagnetic-thermal-flow coupled analysis method to predict temperature distribution inside 154kV single phase power transformer using natural ester. It modeled in the actual appearance for the tank and winding of the power transformer to improve the accuracy of analysis and applied heat flow analysis that considered hydromechanics and heat transfer at the same time. It calculated the power loss, the main cause of temperature rise, from winding and core with electromagnetic analysis then used for the heat source for the heat flow analysis. It then compared the reasonability of result of measurement analysis based on the result acquired from temperature rise test using FBG sensor on the power transformer.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.358-363
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• 2007

In this study, experimental study on the heating performance of a $CO_2$ heat pump with gas injection was performed varying gas injection ratio and outdoor temperature to improve the heating performance of $CO_2$ heat pump. The twin rotary compressor having volume ratio of 0.7 was adopted in the $CO_2$ heat pump. From the test results, the heating capacity and COP were increased and the compressor discharge temperature was decreased with the increase of injection ratio. At the outdoor temperature of $-8^{\circ}C$, the heating capacity and COP with the injection were increased by 45% and 24%, respectively, compared with non-injection condition.

• 설비공학논문집
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• 제24권7호
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• pp.585-590
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• 2012

The objective of this study is to investigate the performance of a two-stage compression heat pump system for district heating. The experimental setup of heat pump consists of compressor, condenser, evaporator, expansion device, intercooler, flash tank, oil separator and accumulator. The experimental evaluations on the two-stage compression cycle were carried out under various operating conditions which were heat source temperature, the degree of compressor inlet superheat, and intermediate pressure. The temperature ranges of unutilized energy as the heat source were used in the test conditions. As the heat source temperature increased from $10^{\circ}C$ to $30^{\circ}C$, the COP and heating capacity of the heat pump system increased by 22.6% and 45.8%, respectively. The performance of the two-stage heat pump system increased by 5.2% with the variation of the intermediate pressure in the same heat source temperature conditions.

• 에너지공학
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• 제11권1호
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• pp.18-25
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• 2002

침부식 (FAC, Flow-Accelerated Corrosion)에 의한 감육 문제는 원자력 발전소 배관관리에 있어서 매우 중요하다. 특히 FAC는 배관 내부 유체의 pH, 용존산소 농도, 유체 온도, 유속 및 습증기 분율 등과 배관의 형상 및 재료 등의 특정 조건에서만 발생하므로, FAC 문제를 관리하기 위해서는 체계적인 접근이 필요하다. 본 연구에서는 국내 특정 CANDU원전의 2차계통 배관을 대상으로 관련 데이터베이스 구축, 구축된 데이터베이스를 이용한 FAC감육율의 예측 및 배관 잔여수명의 평가 등을 수행하였다. 또한 FAC 발생기구 및 FAC에 영향을 주는 요인에 대해서도 조사하였다. 습분분리기와 플래시탱크 사이 배관 라인의 해석 예로부터 FAC 문제를 관리하는 방안을 제시하였다. 제시된 방안은 국내 다른 원자력발전소의 배관 관리에도 활용될 수 있을 것이다.