• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.343-348
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• 1996

한국원자력연구소에서는 광범위한 열유동조건에서 CHF 실험을 수행하기 위해 고온, 고압으로 운전할 수 있는 RCS 열수력 Loop를 제작하고 기초 실험자료를 얻기 위해 환상 유로에서 CHF 측정실험을 수행하였다. 실험은 압력 1.82Mpa, 질량유속 300~566kg/$m^2$.s Test Section입구 Subcooling 18$^{\circ}C$ 및 47$^{\circ}C$의 범위에서 수행되었다. CHF 실험자료와 Doerffer의 CHF 상관식을 비교한 결과 상관식은 실험치 보다 최고 160% 크게 예측하였고 Doerffer 상관식은 저유량 영역에서 적용이 어려워질 것으로 예상되었다. 따라서 저유량 영역의 체계적인 CHF 실험자료가 필요하다.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.4
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• pp.355-363
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• 2022

Development of supersonic flying vehicle is one of the most latest issue in modern military technology. Specifically, structural integrity of supersonic flying vehicle can be verified by high temperature structural test. High temperature structural test is required to consider thermal load caused by aerodynamic heating while applying structural load simultaneously. Tubular quartz lamps are generally used to generate thermal load by emitting infrared radiation. In this study, modified heat flux model of tubular quartz lamp is proposed based on existing model. Parameters of the proposed model are optimized upon measured heat flux in three dimensions. Finally, thermal load of plate specimen is designed by the heat flux model. In conclusion, it is possible to predict heat flux applied on plate specimen and desired thermal load of high temperature structural test can be obtained.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.719-726
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• 2017

An experimental study was performed to investigate the combined effects of the pitch and heat flux of nearby tubes on boiling in a pool as well as the heat transfer from a horizontally-installed tube bundle. For this test, two smooth stainless steel tubes (19 mm outside diameter) were used, and the water was at atmospheric pressure. The pitch of these tubes was varied between 28.5 mm and 95 mm, and the heat flux of the nearby tube altered between 0 and $90kW/m^2$. Enhancements in heat transfer were clearly observed when the heat flux of the nearby tube increased while the heat flux of the test section remained below $40kW/m^2$. The tube pitch was found to have a negligible effect on heat transfer when the pitch was greater than four times larger than the tube diameter. The circulating flow, convective flow, and liquid agitation were all seen to enhance heat transfer; however, the interaction between the flow and coalescence of bubbles was detrimental to heat transfer.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.9
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• pp.737-744
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• 2012

The finite volume method for radiation is applied for the analysis of radiative base heating by SE and PE of the aircraft exhaust plume. The exhaust plume is considered as an absorbing, emitting, and scattering medium, while the base plane is assumed to be cold and black. The radiative properties of non-gray gases are obtained through the WSGGM, and the particle is modelled as spheres. The present method is validated by comparing the results with those of the backward Monte-Carlo method and then the radiative base heating characteristics are analyzed by changing such various parameters as particle concentration, temperature, and scattering phase function. The results show that the radiative heat flux coming into the base plane decreases with altitude and distance, but it increases as the particle temperature increases. The forward scattering of particles increases PE while it decreases SE.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.25-32
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• 2000

In this paper, experiments investigating the high-temperature region heat transfer coefficients for the spray cooling of hot flat plates were performed by down spray water using flat spray nozzles. The heat transfer surface is made of copper and is 100mm in length and 40mm in width and 15mm in thickness. The experimental condition of spray are as follows: temperatures of the water droplets are T=20~$80^{\circ}C$ and droplets volume fluxes are D=0.001565~0.010438$m^3/m^2s$. Next, correlating equations for the heat transfer characteristics of spray cooling in the high temperature region are developed from the effects of droplets volume flux and the surface temperature of heat transfer plate.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.05a
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• pp.137-137
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• 2003

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.397-402
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• 2012

The objective of this study is the estimation of the two unknown thermal conductivity and thermal diffusivity by an inverse heat conduction analysis using the Levenberg-Marguardt method. One dimensional formulation of heat conduction problem in the model was applied. Two point transient temperature of test pieces and heat flux of inflow were measured under the high enthalpy flow environment. Estimated thermal conductivity and thermal diffusivity by an inverse analysis were compared with the known values of graphite test piece. It showed the effectiveness of proposed experimental inverse analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.92.1-92.1
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• 2015

열전소재의 열전성능을 평가하기 위해서는 샘플 내 상하부 온도구배가 필요하다. 하지만 진공챔버 내에서는 대류효과가 제한되어, 1 mm 이하 두께의 얇은 샘플은 상하부 방향으로 온도 구배를 조성하기 어렵다. 온도 구배를 조성하기 위해서는 샘플의 두께 방향을 관통하는 열유속이 필요하며, 진공 분위기에서 열유속을 조성하기 위해서는 히터뿐만 아니라 별도의 열배출기가 요구된다. 본 연구에서는 열전특성 측정 장비 내 수냉식 열배출기의 설계를 위해, 열배출기의 층수를 달리하며 열전달거동을 수치해석적인 방법으로 연구하였다. 열배출기의 층수에 따른 영향을 평가하기 위해서 동일한 채널길이를 유지시키면서 층수를 달리하는 기하학적인 구조들을 설계하였다. 수치해석을 용이하게 진행하기 위해, 열배출기의 형태는 단순한 bar 형태를 가진 1-5층의 다층 구조 로 설계하였다. 열배출기들 각각의 열전달 효율을 평가하기 위해, 수냉식 열배출기의 열배출량에 가장 큰 영향을 미치는 질량유량을 0.1-1 g/s로 변화 시키면서 열전달 거동을 확인하였다. 또한 냉각수의 기화 현상을 방지하기 위해 발열체의 온도를 290-370 K로 바꿔 가며 열전달 거동을 확인하였다. 수치 해석결과, 5층의 열배출기가 최대 120 W/cm2 로 높은 단위면적당 열배출량을 가지는 것을 확인하였으나, 열배출기 전체의 열배출량을 기준으로하는 열배출효율은 0.6 정도로 낮은 효율을 가짐을 확인하였다. 반면에 3층의 열배출기의 경우, 열배출 효율이 0.8에 달하며, 2층의 열배출기 보다 열배출 효율이 좋다는 것을 확인할 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.71-75
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• 2005

An experimental study was carried out to investigate the effect of film cooling in the lab-scale dump-cooled liquid rocket engine using LOX and kerosene as propellants. The nozzle of the rocket engine was film cooled with water as coolant. A special film cooling adapter was fabricated to introduce the film-coolant into the thrust chamber. The flow rates of film coolant was approximately 15~19 percent of the total propellant. The nozzle heat flux was determined from the measured temperature rise and flow rate of the coolant(water). Large reductions in the nozzle heat flux was resulted when film cooling adapter located directly upstream of the nozzle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.453-456
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• 2011

An experimental investigation of the heat transfer characteristics of stretched premixed flames using Synthetic gas has been performed. Hydrogen and carbon mon-oxide which could be extracted from coal gasification process are the main fuel of synthetic-gas. Heat flux at the stagnation point was increased as global strainrate was increased, then the heat flux was decreased when a global strainrate reached a sudden point. Heat flux at the stagnation point is also affected by nozzle to impingement distance. Heat flux was increased as nozzle to impingement place distance was increased. This study is a foundation study of practical use of secondary gases from coals.