• 해양환경안전학회지
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• 제20권3호
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• pp.304-311
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• 2014

In this study, to apply hydrogen energy to ship engine and to generate effective hydrogen production, we investigated the effects of high temperature $H_2SO_4$ feed rate and cooling water rate to pump parts with fixed frequency needed to reciprocate motion and a simulation was conducted at each condition. In the fixed frequency and cooling water inlet flow rate of 0.5 Hz and 3.9 kg/s, we changed the high temperature $H_2SO_4$ flow rate to 47.46 kg/s (it is 105 % of 45.2 kg/s), 49.72 kg/s (110 %), and 51.98 kg/s (115 %). Also, at 0.5 Hz and 45.2 kg/s of frequency and high temperature $H_2SO_4$ flow, the thermal hydraulic analysis was performed at the condition of 95 % (3.705 kg/s), 90 % (3.51 kg/s), and 85 % (3.315 kg/s). In overall simulation cases, the physical properties of materials are more influential to the temperature increase in the pump part rather than the changes on the feed rate of high temperature $H_2SO_4$ and cooling water. A continuous operation of pump was also capable even if the excess feed of high temperature $H_2SO_4$ of about 15 % or the less feed of cooling water of about 15 % were performed, respectively. When the increasing feed of high temperature $H_2SO_4$ of up to 5 %, 10 %, and 15 % were compared with base flow (45.2 kg/s), the deviation of time period rose to a certain temperature and ranged from 0 to 4.5 s in the same position (same material). In case of cooling water, the deviation of time period rose to a certain temperature and ranged from 0 to 5.9 s according to the decreasing feed changes of cooling water at 5 %, 10 %, and 15 % compared to a base flow (3.9 kg/s). Finally, the additional researches related to the two different materials (Teflon and STS for Pitch and End-plate), which are concerned about the effects of temperature changes to the parts contacting different materials, are needed, and we have a plan to conduct a follow-up study.

• International Journal of Fluid Machinery and Systems
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• 제6권1호
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• pp.25-32
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• 2013

Data centers have been built with spread of cloud computing. Further, electric power consumption of it is growing rapidly. High power cooling small-sized fans; high pressure and large flow rate small-sized fan, are used for servers in the data centers and there is a strong demand to increase power of it because of increase of quantity of heat from the servers. Contra-rotating rotors have been adopted for some of high power cooling fans to meet the demand for high power. There is a limitation of space for servers and geometrical restriction for cooling fans because spokes to support fan motors, electrical power cables and so on should be installed in the cooling fans. It is important to clarify complicated internal flow condition and influence of a geometric shape of the cooling fans on performance to achieve high performance of the cooling fans. In the present paper, the performance and the flow condition of the high power contra-rotating small-sized axial fan with a 40mm square casing are shown by experimental and numerical results. Furthermore, influence of the geometrical shape of the small-sized cooling fan on the internal flow condition is clarified and design guideline to improve the performance is discussed.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.271-278
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• 2020

The investigation into a full-scale 27 m high, by 6 m wide, thermosyphon loop. The simulation model is based on a one-dimensional axially-symmetrical control volume approach, where the loop is divided into a series of discreet control volumes. The three conservation equations, namely, mass, momentum and energy, were applied to these control volumes and solved with an explicit numerical method. The flow is assumed to be quasi-static, implying that the mass-flow rate changes over time. However, at any instant in time the mass-flow rate is constant around the loop. The boussinesq approximation was invoked, and a reasonable correlation between the experimental and theoretical results was obtained. Experimental results are presented and the flow regimes of the working fluid inside the loop identified. The results indicate that a series of such thermosyphon loops can be used as a cavity cooling system and that the one-dimensional theoretical model can predict the internal temperature and mass-flow rate of the thermosyphon loop.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.249-256
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• 2009

The cooling technology of power conversion semiconductors in the propulsion system for the HEMU(High Electrical Multi Unit) are applied in water cooling method and phase change method such as the immersed type and the heat pipe type. This research designs and manufactures the water cooling system that could cool about heat load Q=2kW and performance tests to apply it by an electric power conversion semiconductors(IGBT) cooling technology. Experimental condition made change of a flow rate, an air velocity and a heat load to confirm operation characteristics of water cooling device, and when is heat load 2kW, air velocity 20 m/s, and water flow rate 7kg/s, it is about $80^{\circ}C$ to temperature of cooling plate.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.119-122
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• 2009

본 연구는 친환경 추진제인 과산화수소($H_2O_2$)와 케로신을 추진제로 하는 액체 로켓 엔진에서의 막냉 각 장치 개발을 목적으로 이를 위하여 막냉각링을 설계/제작하고, 수류 시험을 통해 분무 특성과 공급 유량을 확인하였다. 또한 설계/제작된 막냉각링의 성능 예측을 위하여 열해석을 수행하였다. 수류 실험 결과 설계 유량(42.25g/s)이 공급됨을 확인하였고, 상대적으로 유속이 빠르고 홀 개수가 많은 막냉각링이 더 좋은 분무패턴을 보임을 확인하였다. 또한 열해석 결과 설계된 막냉각링이 충분한 냉각 성능을 가짐을 확인하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권10호
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• pp.1244-1250
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• 2014

The temperature of the main engine cabin of commercial vessel is very high. The material SS-316L undergoes creep damage at temperatures exceeding $450^{\circ}C$. It is essential to maintain the highly stressed engine cabin below the creep regime. Hence, seawater is employed in this kind of maritime vehicles as cooling liquid. It obtains the thermal energy at the cooling pipe line after passing through main engine cooling system. To harness the energy in the seawater, a turbine can be installed to absorb the energy in the seawater before being released into the sea. In this study, a cooling pipe line is selected to apply the tubular type hydro turbine for transferring the energy. Numerical analysis for investigating the performance and the internal flow characteristics of the tubular turbine is conducted. The results show that the maximum efficiency of 85.8% is achieved although the efficiency drops rapidly at partial flow rate condition. The efficiency descends slowly at the condition of excess flow rate. There is a relatively wide operating range of flow rate of this turbine to keep high efficiency at the excess flow rate condition. For the internal flow of the turbine, there is uniform streamline on the suction and pressure sides of the blade at the design point. However, the secondary flow appears at the suction and pressure sidesat the excess flow rate.In addition, it appears only at pressure side at the partial flow rate condition.

• 한국재료학회지
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• 제22권10호
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• pp.513-518
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• 2012

Recently, automobile parts have been required to have high strength and toughness to allow for weight lightening or improved stability. But, traditional micro-alloyed steel cannot be applied in automobile parts. In this study, we considered the influence of quenching temperature and cooling rate for specimens fabricated by vacuum induction furnace. Directly quenched micro-alloyed steel for hot forging can be controlled according to its micro structure and the heat-treatment process. Low carbon steel, as well as alloying elements for improvement of strength and toughness, was used to obtain optimized conditions. After hot forging at $1,200^{\circ}C$, the ideal mechanical properties (tensile strength ${\geq}$ 1,000 MPa, Charpy impact value ${\geq}\;100\;J/cm^2$) can be achieved by using optimized conditions (quenching temperature : 925 to $1,050^{\circ}C$, cooling rate : ${\geq}\;5^{\circ}C/sec$). The difference of impact value according to cooling rate can be influenced by the microstructure. A fine lath martensite micro structure is formed at a cooling rate of over $5^{\circ}C/sec$. On the other hand, the second phase of the M-A constituent microstructure is the cause of crack initiation under the cooling rate of $5^{\circ}C/sec$.

• 한국추진공학회지
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• 제11권3호
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• pp.1-6
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• 2007

연소기의 성능 향상 연구를 위해 3톤급 고압 축소형 연소기를 설계 제작하였다. 이 연소기는 하드웨어의 열적 손상을 방지하기 위해 막 냉각 및 열차폐 코팅 그리고 축방향 물냉각이 적용된 연소실과 37개의 동축 와류형 분사기를 갖는 연소기 헤드로 구성된다. 연소시험은 막 냉각 유량변화에 따라 설계점에서 수행되었고 시험결과 막 냉각 유량의 증가는 연소성능의 감소를 가져오지만 비슷한 막 냉각 유량이 적용된 시험의 경우 막 냉각 유량을 제외한 주 분사기의 혼합비에 따라 연소성능이 결정됨을 알 수 있었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1231-1236
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• 2008

The flow and heat transfer performance were measured at high temperatures in CFB heat exchanger with multiple risers and downcomers. The theoretical model for predicting heat exchanger performance was developed in this study. The model predictions were compared with the measured heat transfer rates to show relatively good agreement. The maximum gas cooling rate was $20,300^{\circ}C/sec$, and the dioxin reduction rate was 68%.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.33-34
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• 2005

The internal state of an automotive engine is very severe. A piston exposes burnt gas of over $2000^{\circ}$ nd is shocked by high pressure at the time of explosion. Furthermore strong friction is caused by high speed motion. A study on the cooling of the piston requires because the cooling and lubrication of the piston has an effect on the life and efficiency of engine directly. The previous system of oil jet cooled only the bottom of the piston. In order to improve the cooling efficiency, the oil gallery is made inside the piston, and oil flows into the oil gallery. The flow rate of oil at the entrance of oil gallery is important because of the cooling efficiency. The purpose of this study is the investigation of fluid flow characteristics of oil jet and flow rate into the oil gallery.