• 설비공학논문집
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• 제18권8호
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• pp.664-671
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• 2006

We propose the correlation to predict the spreading thermal resistance on a plate with symmetrical four heat sources. The correlation transforms four heat sources to a single equivalent heat source and then the spreading thermal resistance can be obtained with the existing equation for a single heat source. When the four heat sources are mounted on a square base plate, the correlation is expressed as a function of the heat source size, the length of base plate, the plate thermal conductivity and the distance between heat sources. Compared to the results of three-dimensional numerical analysis, the spreading thermal resistance by the proposed correlation is in good agreement within 10 percent accuracy.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.40.2-40.2
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• 2005

• 한국화재소방학회논문지
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• 제7권1호
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• pp.5-10
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• 1993

Flame spreading over liquid fuel surface has been investigated using thermocouple and schlieren photograph. Without forced convection, it was clearly found that the flame spreading is mainly controlled by surface flow which is maybe generated by change of surface tension. Furthermore, the radiative heat transfer is dominant over a conductive heat transfer in kerosene. But the latter was found more influential than the former in diesel. Oscillation of flame spreading was found. It maybe cause of surface flow.

• Nuclear Engineering and Technology
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• 제45권1호
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• pp.21-28
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• 2013

The flow and heat transfer characteristics of the ex-vessel core melt (corium) were investigated using a commercial CFD code along with the experimental data on the spreading of corium available in the literature (VULCANO VE-U7 test). In the numerical simulation of the unsteady two-phase flow, the volume-of-fluid model was applied for the spreading and interfacial surface formation of corium with the surrounding air. The effects of the key parameters were evaluated for the corium spreading, including the radiation, decay heat, temperature-dependent viscosity and initial temperature of corium. The results showed a reasonable trend of corium progression influenced by the changes in the radiation, decay heat, temperature-dependent viscosity and initial temperature of corium. The modeling of the viscosity appropriate for corium and the radiative heat transfer was critical, since the front progression and temperature profiles were strongly dependent on the models. Further development is required for the code to consider the formation of crust on the surfaces of corium and the interaction with the substrate.

• 대한기계학회논문집
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• 제13권2호
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• pp.271-276
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• 1989

본 실험에서는 액체연료인 석유와 등유을 사용하여 전도, 복사, 대류, 연료의 표면유동 등이 각각 어느 정도 화염확장에 영향을 주는 가를 예측하기 위하여 위의 각각을 제어할 수 있는 장애물을 설치하였으며, 연료의 깊이에 의한 화염확장의 영향을 알아보기 위하여 3가지 종류의 깊이에 대하여 실험을 수행하였다.

• 한국수소및신에너지학회논문집
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• 제32권5호
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• pp.365-373
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• 2021

In this study, evaporation of LN2 non-spreading pool on concrete plate was dealt with experimentally. The thermophysical properties of concrete, which is a composite material, were obtained by minimizing the difference between the numerical analysis results obtained from the assumed properties and the results from experiments. The thermal energy required for evaporation of the liquid pool is supplied from the concrete plate and the wall of the container. As a result of the measurement, the thermal energy flowing in from the wall was negligible compared to the one supplied from the concrete plate. It was found that the measured evaporation rate of the liquid pool by the heat energy supplied through the concrete plate agrees well with the PTC model except for the initial section of the experiment. The validity of the semi-infinite assumption and the one-dimensional assumption, which are the main conditions of the PTC model, was also verified through experiments. The evaporation rate model in the non-spreading pool discussed in this study can provide a basic frame for the one in the spreading pool, which is a meaningful result considering that the spreading pool is very realistic compared to the non-spreading pool.

• 한국레이저가공학회지
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• 제3권3호
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• pp.21-29
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• 2000

For the direct metal shape processing the powder feed device which is different from the widely used in rapid prototyping. is developed, The three dimensional object is shaped with the melting metal powder. The developed research has applied to rapid prototyping in ultraprecision for MEMS and medical science fields required of rapid manufacture of complex shape. The goal of this study make 3D model which has precision accuracy. Powder spreading apparatus has been more improved because that the control of powder spread is very important in layer manufacturing. It consists of the vibration motor, nozzle and tube which supplies various metal powder. This apparatus could control the spreading velocity that could control powder spreading thickness. Laser on/off switch was adapted because laser scanning velocity must be preserved constantly to prevent heat transformation of laser overheating. The error between sintered thickness md experimental one occurred by shrinkage in sintering melting process. The problem of heat transformation was solved by On/Off switching system.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.201-201
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• 2012

Using materials with high thermal conductivity is a matter of great concern in the field of thermal management. In this study, we present our experimental results on an important physical property of carbon nanotube (CNT) films, two-dimensional thermal conductivity obtained by using an optical method based on Raman spectroscopy. We prepared four kinds of CNT films to investigate the effect of CNT type on heat spreading performance of films. This first comparative study using the optical method shows that the arc-discharge single-walled carbon nanotubes yield the best heat spreading film. And we observed thermal conductivity values of CNT films with various transmittances and found that the Raman method works as long as the sample is a transparent film. This study provides useful information on characterization of thermal conduction in transparent CNT films and could be an important step toward high-performance carbon-based heat spreading films.

• 펄프종이기술
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• 제37권5호통권113호
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• pp.1-7
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• 2005

The objective of this work was to investigate the effect of spreading behavior of the sizing agents (AKD or dialkyl ketone) on the sizing development of AKD-sized paper. There was a direct relationship between the spreading behavior of the sizing agents and their melting points. Both AKD and dialkyl ketone showed no substantial spreading until the temperature reaches to their melting points. Consequently, dialkyl ketone did not provide sizing development when the paper was heat-treated below $75^{\circ}C$, while AKD provided sizing effect even the paper heated at $50^{\circ}C$. The ketone, however, provided rather higher sizing effect than that of AKD, when the paper was heat-treated over $100^{\circ}C$. This result means that the ketone also gives sizing development to paper, moreover the ketone could give higher sizing effect to paper than AKD when it was melted and well spreaded on the fiber surface. While the ketone introduced to papers from hydrolyzed AKD emulsion could not contribute to sizing development.

• 설비공학논문집
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• 제18권6호
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• pp.477-485
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• 2006

A study on frost prevention of fin-tube heat exchanger is experimently performed by spreading antifreezing solution on heat exchanger surface. It is desirable that the antifreezing solution spreads completely on the surface forming thin liquid film to prevent frost nucleation and crystal growth and to reduce the thermal resistance across the liquid film. A small amount of antifreezing solution falls in drops on heat exchanger surface using two types of supplying devices, and a porous layer coating technique is adopted to enhance the wettedness of antifreezing solution on the surface. It is observed that the antifreezing solution liquid film prevents fin-tube heat exchanger from frosting, and heat transfer performance does not degrade through the frosting tests. The concentration of supplied antifreezing solution can be determined by heat transfer analysis of the first row of heat exchanger to avoid antifreezing solution freezing due to dilution by moisture absorption.