• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.918-919
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• 2015

Because of environmental regulations in emissions control area, the demand for ships to use LNG as fuel is increasing. Orders for domestic shipbuilders to produce LNG carriers are steadily increasing. However, major appliances such as spray pump, main cargo pump and others have been relied on imports. Therefore, development of pump motor using at cryogenic temperature is necessary. Operating temperature of an induction motor is at $-163^{\circ}C$. At this low temperature, the resistivity of a motor coil is quite different from normal ones, and so does the torque characteristics of motor. This paper presents a designing method of a cryogenic induction motor for LNG pump. The variation of resistivity of motor coil is considered in the design process. The heat source such as core-loss, hysteresis-loss and copper-loss are analyzed to prevent the LNG evaporation which may cause the motor failure.

• 설비공학논문집
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• 제5권3호
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• pp.226-233
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• 1993

Thermosyphons are simple devices that can passively transport thermal energy over relatively large distance with little temperature degradation. Especially, the thermosyphon system requires no costly energy input and is completely maintenance free. These attributes permit the use of low grade thermal energy for thermal control of structures including the stabilization of highway foundations. This paper presents the experimental results of the snow melting system in which thermosyphon was utilized to ransfer the earth energy to the pavement to remove snow and ice. The test facility, three earth heated and one unheated test panels, is designed to investigate the variables associated with removing snow and ice from pavement surfaces. The results of these test show that the earth heated panel surface temperature is higher $2{\sim}6^{\circ}C$ than unheated panel when the ambient air temperature is $-7^{\circ}C$. The thermal performance of this earth source thermosyphon system for road heating showed that there was no snow on the heated test panels when the snowfall was 5cm average for the region.

• The Korean Journal of Ceramics
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• 제2권4호
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• pp.221-225
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• 1996

In diamond synthesis by metal film growth method under high pressure and high temperature, the nucleation and growth of diamond was observed dependent on the carbon source variation from graphite powder to the heat treated powders of lamp black carbon. At the low driving force condition near equilibrium pressure and temperature line, nucleation of diamond did not occur but growth of seed diamond appeared in the synthesis from lamp black carbon while both nucleation and growth of diamond took place in the synthesis from graphite. Growth morphology change of diamond occurred from cubo-octahedron to octahedron in the synthesis from graphite but very irregular growth of seed diamond occurred in the synthesis from lamp block carbon. Lamp black carbon transformed to recrystallized graphite first and very nucleation of diamond was observed on the recrystallized graphite surface. Growth morphology of diamond on the recrystallized graphite was clear cubo-octahedron even at higher pressure departure condition from equilibrium pressure and temperature line.

• Journal of Advanced Marine Engineering and Technology
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• 제33권7호
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• pp.987-993
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• 2009

An experimental study is performed to investigate unsteady mixed convection in a horizontal channel with a heat source. Particle image velocimetry (PIV) with thermo-sensitive liquid crystal (TLC) tracers is used for visualization and analysis. This method allows simultaneous measurement of velocity and temperature fields at a given instant of time. Quantitative data of the temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. It is found that the periodic flow of mixed convection in a cavity appears at very low Reynolds numbers (Re<0.4), and the period decreases with increasing Reynolds numbers and increases with increasing aspect ratio.

• 한국과학교육학회지
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• 제10권1호
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• pp.95-118
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• 1990

This students ideas in science are diverse and unique It is realized that children's preconceptions and misconceptions established before lessoning hgve a crucial in fluence on the following education. so it is meaningful to analyse the children's concept of temperature for the better teaching strategy in this study. This survey of the Elementary school children's concept is designed for the subtopics of temperature as the relation between heat and temperature, He relation between volume(size) and temperature, the temperature of change of state on water, the temperature of substances in the condition of thermal equilibrium. Using Clinical method, this research was executed to 306 children at elementary school. The network method or the analyse of questionnaires were used to analyse the children's response. Findings of this survey are as follow. Students are already familiar with such concept as this increase of temperature by geating, but they think every substance is not the case. Many students appears to believe that the temperature of an object(substance) is related to its size(vloume) Qualitative tasks are difficult than qualitative ones. This trend appear highly in the low grade students. Don't know the temperature of change of state on water and it's stability They think that the temperature is determined by the heating time(period) and the temperature of heating source. Students think, in general that temperature of substance in the condition of thermal equilibrium is different.

• 한국산학기술학회논문지
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• 제20권4호
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• pp.639-647
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• 2019

최근 전자장비의 소형화 및, 고밀도화가 되는 반도체 집적기술의 발달로 인해 칩과 모듈에서 발생되는 내부발열량을 외부로 적절히 방출시키기 위해서 열 제어시스템 적용에 대한 연구의 중요성을 인식하고 있다. 본 연구는 SST k-${\omega}$ 난류모델을 적용하여 4개의 블록이 부착한 수평채널내에서 열전달 및 압력강하 특성을 고찰하였다. CFD 해석시 적용한 매개변수는 블록 폭, 블록 높이, 열원 및 난류발생기 배치이고, 해석시 기본 경계조건은 채널 입구의 온도 및 유속은 300 K, 3.84 m/s, 열유속은 $358W/m^2$으로 하였다. 그 결과로 블록 폭비율(w/h)이 증가할수록 열전달성능이 감소하는 반면에 블록 높이비(h/w)이 증가할수록 열전달특성은 증가하는 경향을 나타내었으며, 열원의 크기배열은 낮은 열유속에서 높은 열유속으로 증가시킬수록 열원의 영향을 받아 열전달계수는 증가하는 경향을 나타냈고, 난류발생기는 채널 입구에 가까운 블록 1번 위치의 상단에 설치했을 경우가 4개의 가열블록 전체에 가장 영향을 크게 미치게 되고, 압력강하특성을 고려할 때 가장 적절한 위치로 선정할 수 있었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.782-787
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• 2008

The Kalina cycle simulation study was carried out for a preliminary design of a geothermal power generation system. The Kalina cycle system can be used for the utilization of a low-temperature heat sources such as geothermal and industrial waste heat that are not hot enough to produce steam. The sea/river water can be considered as a cooling media. A steady-state simulation model was developed to analyze and optimize its performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump were modelled by an isentropic efficiency, while a condenser, an evaporator and a regenerative heat exchanger were modeled by UA-LMTD method with a counter-flow assumption. The simulation results show that the power generation efficiency over 10% is expected when a heat source and sink inlet temperatures are $100^{\circ}C$ and $10^{\circ}C$ respectively.

• 천문학회지
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• 제29권2호
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• pp.107-117
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• 1996

We have studied the star forming activities and dust properties of Lynds 1251, a dark cloud located at relatively high galactic latitude. Eleven IRAS point sources identified toward Lynds 1251 are discussed. Estimate of stellar masses, and far-infrared lumnosities of the young stars associated with two prominent IRAS point sources imply that these are T-Tauri stars with masses smaller than $0.3 M_\bigodot$. The low dust temperature of 27 K and low ratio of FIR emission to hydrogen column density are probably due to the lack of internal heating sources. Presumably two low mass young stars do not have enough energy to heat up the dust and gas associated. The dust heating is dominated by the interstellar heating source, and the weaker interstellar radiation field can explain the exceptionally low dust temperatures found in Lynds 1251. The estimated dust mass of Lynds 1251 is just $\~1M_\bigodot$, or about 1/1000 of gas mass, which implies that there must be a substantial amount of colder dust. The infrared flux at $100{\mu}m$ is matching well with $^{13}CO$ peak temperature, while the $^{12}CO$ integrated intensity is matching with the boundary of dust emission. Overall, the dust properties of Lynds 1251 is similar to those of normal dark clouds even though it does have star forming activities.

• Journal of Advanced Marine Engineering and Technology
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• 제23권3호
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• pp.311-319
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• 1999

In Korea accelerated industry development and urbanization during the last three decades have led serious water pollution problems in many parts of the nation. Especially in the regions of west and south coast have low fresh water in the dry season of spring and summer. In the place isolated from land it is important to secure the fresh water for drinking and general service. This study is concerned on the thermal system design to develop low-pressure evaporation type fresh water gen-erator of capacity 1 ton/day using the heat source of non-operating boiler in the season of spring and summer. The results obtained from this study are as follows. the water quantitieds generated from experi-mental evaporator showed good coincidence with the calculated values. The maximum production quantity was 1.38ton/day at pressure 40mmHg abs. and temperature $80^{\circ}C$.

• 대한기계학회논문집B
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• 제24권8호
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• pp.1038-1045
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• 2000

An experimental study was carried out to delineate the flow characteristics in a closed countescurrent two-phase thermo syphon with concentric tubes. This is to be installed in the HANARO research reactor as a part of a Cold Neutron Source(CNS). In the present investigation, experiments ata room temperature with Freon-II3 as a moderator were performed. Results show that, based on the magnitude of pressure fluctuation, the flow regimes could be divided into 4 distinct ones in the ($V_f,\;Q_i$) plane, where $V_f$ represents the volume of the charged liquid and $Q_i$ the heat load: a stable flow regime, an oscillatory flow regime, a restablized flow regime and a dryout flow regime. For $V_f$>2.5l, the flow is stable at low $Q_i$. However, as $Q_i$ increases, the flow becomes oscillatory and finally restablizes As $V_f$ increases, the oscillation amplitude decreases, reaching to the restablized flow region at low $Q_i$, and the liquid level in the moderator cell remains high. In the oscillatory flow regimes, for a fixed VI; the oscillating period of time varies with $Q_i$, having a minimum value at a certain value of $Q_i$. The heat load, where the oscillating period of time is minimum, decreases as $V_f$ increases.