• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.87-94
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• 1992

Film boiling heat transfer characteristics in liquid-liquid systems are studied experimentally. Liquid gallium as a heating liquid, n-pentane, freon-113, and ethanol are used as boiling liquids. In gallium-n-pentane and gallium-freon-113 systems the minimum film boiling point occurred at higher temperature than those observed in copper-boiling liquid systems. However MFB point occurred almost at the same temperature for the case of ethanol. This difference are due to the effects of contact angle and interfacial agitations in gallium-boiling liquid systems. Film boiling heat transfer rate, for the gallium-boiling liquid systems considered in this work, found to be approximately 10% higher than those in copper-boiling liquid systems, whose main cause is believed to be gallium-boiling liquid interfacial agitations affected by the density ratio between gallium and boiling liquid.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.9
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• pp.597-603
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• 2017

In this study, experiments were conducted on the MFB(minimum film boiling) point of highly heated vertical metal rod quenched in aqueous surfactant solution at various temperature conditions. The aqueous Triton X-100 solution(100 wppm) and pure water were used as the liquid pool. Their temperatures ranged from $77^{\circ}C$ to $100^{\circ}C$. A stainless steel vertical rod of initial center temperature of $500^{\circ}C$ was used as a test specimen. In both liquid pools, as the liquid temperature decreased, the time to reach the MFB point decreased with a parallel increase in the temperature and heat flux of the MFB point. However, over the whole present temperature range, in the aqueous Triton X-100 solution, the time to reach the MFB point was longer, while the temperature and heat flux of the MFB point were reduced when compared with pure water. Based on the present experimental data, this study proposed the empirical correlations to predict the MFB temperature of a high temperature vertical metal rod in pure water and in aqueous Triton X-100 solution.

• Journal of Korea Soil Environment Society
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• v.4 no.2
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• pp.137-147
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• 1999

Fluidized-bed thermal desorber coupled with a heat pipe was investigated for the remediation of soil contaminated with diesel oils. Thermal gravimetric analysis by Cahn-balance indicated that the desorption of diesel oils from the soil particles was mainly governed by the internal diffusion at low concentration of less than 0.5 wt. % of oils in the soil particles. In fluidized-bed experiments. increase of fluidizing gas velocity reduced the residual oils of the contaminated soils, the increase of soil feed rate decreased efficiency of fluidized-bed desorber. A mathematical model was developed by incorporating Fickian diffusion kinetics into the Kunii-Levenspiel model Simulation results showed reasonable agreement for the performance of fluidized-bed thermal desorber.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.107-107
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• 2016

표면영상유속계는 영상분석을 이용하여 홍수시 하천 수표면 유속을 측정하는 비접촉식 유속측정장치이다. 때문에 안전하고 편하게 홍수시 유속을 측정할 수 있으나, 이를 위해서는 영상과 실세계와의 좌표변환을 위한 참조점 측량이 반드시 필요하였다. 좌표 변환에 8-변수 사영변환을 이용할 경우 최소한 4개의 참조점이 필요하다. 그러나 홍수시 참조점 측량은 불가능에 가까우며, 홍수전후의 측량도 매우 번거로운 일이다. 본 연구에서는 참조점을 이용하지 않고, 좌표변환 관계를 구성할 수 있는 카메라 모형(camera model)을 구성하였다. 여기서 카메라 모형은 실세계 좌표(world coordinates)를 영상좌표(image coordinates)로 변환해 주는 관계를 말한다. 이 카메라 모형에 필요한 외부 변수는 하천수표면과 카메라와의 높이 및 카메라의 두 가지 경사각뿐이다. 여기에 일반적인 카메라 보정에 이용하는 방법으로 구한 카메라 내부 변수를 결합하면 된다. 이 모형은 표면영상유속계 장비로 스마트폰을 이용할 때 간편하게 적용할 수 있으며, 별도의 경사계만 부착하면 일반적인 CCTV나 캠코더를 이용할 때도 적용할 수 있다. 이 카메라 모형과 종래 사용하던 8-변수 사영변환에 의한 좌표변환관계를 비교한 결과 상호간 오차가 거의 없이 적용할 수 있었다. 또한, 스마트폰 표면영상유속계와 열영상 표면영상유속계에 적용한 결과 종전보다 훨씬 적용이 간편하며, 정확도 또한 거의 차이가 없이 적용할 수 있었다.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.175-180
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• 2001

In this study, the minimum heat flux conditions are experimentally investigated for the spray cooling of hot plate. The hot plates are cooled down from the initial temperature of about $900^{\circ}C$, and the local heat flux and surface temperatures are calculated from the measured temperature-time history. The results show that the minimum heat flux point temperatures increase linearly resulting from the propagation of wetting front with the increase of the distance from the stagnation point of spray flow. However, in the wall region, the minimum heat flux point temperature becomes independent of the distance. Also, the experimental results show that the velocity of wetting front increases with the increase of the droplet flow rate.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.208-213
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• 2001

The minimum heat flux conditions are experimentally investigated for the subcooled liquid film flow on the horizontal plate. The experimental results show that the minimum heat flux point temperature becomes higher with the increase of the velocity and the subcooling of the liquid film flow. However, the effect of distance from the leading edge of the heat transfer plate on the minimum heat flux is almost negligible. Also, the experimental results show that the propagation velocity of wetting front increase with increasing the velocity and the subcooling of the liquid film flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.960-965
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• 2001

The minimum heat flux conditions are experimentally investigated for the subcooled liquid film flow on the horizontal plate. The experimental results show that the minimum heat flux point temperature becomes higher with the increase of the velocity and the subcooling of the liquid film flow. However, the effect of distance from the leading edge of the heat transfer plate on the minimum heat flux is almost negligible. Also, the experimental results show that the propagation velocity of wetting front increases with increasing the velocity and the subcooling of the liquid film flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.974-981
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• 2001

In this study, the minimum heat flux conditions are experimentally investigated for the spray cooling of hot plate. The hot plates are cooled down from the initial temperature of about$ 900^{\circ}C$, and the local heat flux and surface temperatures are calculated from the measured temperature-time history. The results show that the minimum heat flux point temperatures increase linearly resulting from the propagation of wetting front with the increase of the distance from the stagnation point of spray flow. However, in the wall region, the minimum heat flux point temperature becomes independent of the distance. Also, the velocity of wetting front increases with the increase of the droplet flow rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.554-560
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• 2021

CRUD (chalk river unidentified deposits) is a porous material deposited on the surface of nuclear fuel during nuclear power plant operation. The CRUD is composed of metal oxides, such as iron, nickel, and chromium. It is essential to investigate the effects of the CRUD layer on the wall heat transfer between the nuclear fuel surface and the coolant in the event of a nuclear accident. CRUD only negatively affects the temperature of the nuclear fuel due to heat resistance because the effects of the CRUD layer on two-phase boiling heat transfer are not considered. In this study, the physical property models for the porous CRUD layer were developed and implemented into the SPACE code. The effects of boiling heat transfer models on the peak cladding temperature and quenching were investigated by simulating a reflood experiment. The calculation results showed some positive effects of the CRUD layer.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.1
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• pp.1-9
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• 2016

Optimum cross-sectional shape of an automotive disc brake was developed based on FEM thermal analyses and the Taguchi method. Frictional heat flux and convection heat transfer coefficients were first calculated using equations and applied to the disc to calculate accurate temperature distribution and thermal deformations under realistic braking conditions. Maximum stress was generated in an area with highest temperature under pads and near the hat of ventilated disc and vanes. The SN ratio from Taguchi method and MINITAB was applied to obtain the optimum cross-sectional design of a disc brake on the basis of thermal deformations. The optimum cross-section of a disc can reduce thermal deformation by 15.2 % compared to the initial design.