• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.4
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• pp.94-103
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• 2016

A regeneratively-cooled channel in a liquid rocket engine is used to effectively cool a combustion chamber inner wall from hot combustion gas, and the heat transfer/pressure loss characteristics should be predicted in advance to design cooling channels. In the present research, five cooling channels with different geometric dimensions were designed and the channels were respectively manufactured using cutter and endmill. By changing coolant velocity and downstream pressure, the effects of manufacturing method, channel shape, and flow condition on pressure losses were experimentally investigated and the results were compared with the analytical results. At same channel shape and flow condition, the pressure loss in the channel machined by the cutter was lower than that by the endmill. It was also found that the pressure loss ratio between the experimental result and the analytical data changed with the channel shape and flow condition.

• Journal of the Korean Electrochemical Society
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• v.25 no.3
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• pp.119-124
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• 2022

Because high power with large size cell is used for the battery pack of hybrid electric vehicles and electric vehicles (HEV and EV), average temperature in a battery cell is the important criteria of the thermal management of the battery pack. Furthermore, fast charging technology is required to reduce battery charging time. Since battery pack performance and lifespan are deteriorated due to the heat of cells and electronic components caused by fast charging, an effective cooling system is required to reduce performance deterioration. In this study, a cooling system and module design applied to a pouch-type for fast charging battery cell are investigated, and the cooling performance that can maximize the efficiency of the battery was analyzed. The result shows that the vapor chamber cooling system has better cooling performance, the temperature drop in the module was 5.82 ℃ compared with aluminum cooling plates.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.596-602
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• 2020

Blending process of adhesive production has a cooling process to cool down the temperature of the solution which was heated up to 76 ℃ with a mineral insulated (MI) cable by 30 ℃ at room temperature. Using a MI cable in the adhesive production process makes the production inefficient because it takes about 10 h for the cooling process. If a jacketed vessel is used instead of the MI cable, it would shorten the cooling downtime without any additional cooling system by using cold water. However, there are various types of jacketed vessels, and thus the most suitable type should be found before set up. In this study, we designed the optimized jacketed vessel for the adhesive production process by calculating the cooling downtime, which impacts production efficiency, as a function of the jacket types using computational fluid dynamics. As a result, the cooling performance of the plain jacket was 32.7% superior to that of the half-pipe coil jacket with the same height. In addition, the plain jacket with 60% spiral baffle reduced the cooling downtime and operating time by 80.4% and 25.1%, respectively.

• Journal of the KSME
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• v.33 no.11
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• pp.979-984
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• 1993

압축기는 냉동 . 공조 사이클에서 냉매를 압축하여 순환시키는 기능을 한다. 냉동 . 공조 사이클 에서 압축기의 효율 COP는 압축기 모터 입력에 대한 증발기에서의 냉각 능력의 비로서 정의 된다. 따라서 압축기 자체의 특성도 중요하지만 냉매의 열역학적 물성도 중요한 역할을 한다. 압축기의 효율향상문제가 최근에 대두되게 된 것은 첫 째, 몬트리올 협정에 의해 CFC의 사용이 제한되면서 새로 검토하게 된 대체냉매들의 열물성이 CFC보다 불리한 점과 둘째, 에너지 소비를 줄이려는 인식이 환경 측면에서 확산되고 있기 때문이다. 이 글에서는 압축기 효율을 결정하는 주요요소에 대하여 알아보고 최근 국내외에서 이루어지고 있는 효율향상 성과에 대하여 소개하 기로 한다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.183-186
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• 2009

The crystalline silicon solar cell was one of the first to be developed and it is still the most widely used type. The photovoltaic cells will exhibit long-term degradation if the temperature exceed a certain limit. The purpose of this study is to investigate the possible of improving the performance of a photovoltaic cooling system. According to the results of the experiment, the thermal degradation of 44.63degrees was observed by cooling on the surface of photovoltaic cells. It is a decrease of 22.215percent of generating power. It is shown that photovoltaic cooling system is effected on improving the effectiveness of a photovoltaic out of power.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.365-368
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• 2001

입사면에서 발생하는 열을 효율적으로 제거하기 위하여 Yb:YAG 결정의 표면에 sapphire 창을 부착하여 레이저를 발진 시켰다. Yb:YAG 결정에서 발생하는 열이 sapphire 창을 통하여 구리판으로 전달되는 경우 와 Yb:YAG 결정의 측면에서 냉각하는 경우의 레이저 출력을 측정하여 각각의 레이저 발진 특성을 비교하여 보았다. 여기면을 sapphire 창으로 냉각하는 micro-chip Yb:YAG 레이저의 레이저 에너지 전환 효율은 38%였으며 레이저 발진 문턱값은 4 kw/mm$^2$, slope efficiency는 56%로 측정되었다. Sapphire 창을 사용하는 경우 표면에서의 열전달도는 10 W/mm$^2$이상으로 관측되었다. Yb:YAG의 도핑율, 출력경의 반사율 등을 레이저 변수를 최적화할 경우 같은 구조에서 50 W급 레이저도 발진 가능할 것으로 예상된다.

• The KSFM Journal of Fluid Machinery
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• v.17 no.2
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• pp.12-23
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• 2014

A parametric study on anti-vortex holes for turbine blade cooling was investigated numerically. Three-dimensional Reynolds-averaged Navier-Stokes equations and shear stress transport turbulence model were used for analysis of anti-vortex film cooling. Validation of numerical results was carried out comparing with experimental data. The cooling performance of anti-vortex holes was assessed by two geometric variables, the ratio of diameters of holes and the lateral distances between the primary hole and anti-vortex hole at blowing ratios of 0.5 and 1.0. The results showed that the spatially-averaged film-cooling effectiveness increases as the ratio of the diameters increases and the distance between the primary hole and anti-vortex hole decreases.

• Journal of Energy Engineering
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• v.9 no.1
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• pp.1-9
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• 2000

공정연계를 최소호하는 IGCC 시스템에 대한 개념설계를 수행하였다. 공정분석은 상용코드인 ASPEN PLUS를 이용하였다. 가스화기의 적절한 운전조건을 찾기위하여 가스화기를 경계조건으로 하는 액서지 민감도분석을 통하여 투입되는 슬러리와 산소의 조건을 결정하였다. 또한 , 생성가스 냉각시 현열을 최대한 회수학 ldn하여 , 열교환망을 통하여 급수를 에열하고 가스화플랜트의 각 부분에 공급하도록 공정을 구성하였다. 여분의 가열된 급수는 갑압증발시켜 복합사이클에서 동력을 생성시키는데 사용되어진다. 이와 같은 시스템은 , 가스터빈 -ASU-가스화플랜트의 공기에 의한 공정연계와, HRSG-가스냉각 및 정제시스템 간의 증기연계를 가능한 적게함으로써 공정의 운전성과 경제성을 최적으로 유지할 수 있다. 본 연구에서 제시하는 공정의 경우에, 열효율이 약 39%(고위발열량 기준)으로 나타났으며, 단위 기기 및 단위공정들의 최적화를 통하여 40%의 효율달성이 가능할 것이다.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1999.11a
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• pp.91-94
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• 1999

1. 가열과정과 냉각과정의 열매체 입출구 온도차는 초기에 6$^{\circ}C$이상이었으나 후기의 온도차는 3$^{\circ}C$정도로 나타났으며, 가열과정 중 상변화가 이루어지는 시간은 약 2시간, 3$0^{\circ}C$에서 상변화과정이 이루어지며, 냉각과정은 3$0^{\circ}C$에서 1차 28$^{\circ}C$에서 2차 상변화과정이 진행되는 것으로 나타났으나 30-28$^{\circ}C$에서 계속적인 상변화과정이 나타났으며 진행시간은 약 3시간으로 나타났다. 2. 축열재를 700kg 주입하여 축열성능과 방열성능을 측정한 결과 축열재의 축열량은 37,818㎉, 방열량은 36,228㎉로 나타났다. 이상의 결과로 볼 때 축열시스템의 효율은 95.8%로 나타났다.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.377-381
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• 2001

Film cooling characteristics has been investigated numerically with the aid of FLUENT software for the sunk or the lifted upstream wall from the slot injection exit. In this study, with the fixed blowing ratio of 1 and the fixed coolant injection angle of $30^{\circ}$, the downstream flow field and the downstream temperature field were examined in terms of velocity vector, turbulent kinetic energy, temperature contours, and downstream wall temperature. Upstream wall was sunk or lifted from 1d to 5d(d=slot width). The result shows that the up-Id upstream wall has the best film cooling performance. This is due to the fact that the up-1d upstream wall configuration reduces velocity gradient just enough to minimize the turbulent mixing between the mainstream and the coolant just off the slot exit.