• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1213-1224
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• 2024

The liquid lead-bismuth cooled fast reactor has been in a single-phase, low-pressure, and high-temperature state for a long time during operation. Considering the requirement of calculation efficiency for long-term transient accident calculation, based on a homogeneous hydrodynamic model, one-dimensional heat conduction model, coolant flow and heat transfer model, neutron kinetics model, coolant and material properties model, this study used the fully implicit difference scheme algorithm of the convection-diffusion term to solve the basic conservation equation, to develop the transient analysis program NUSOL-LMR 2.0 for the lead-bismuth fast reactor system. The steady-state and typical design basis accidents (including reactivity introduction, loss of flow caused by main pump idling, excessive cooling, and plant power outage accidents) for the ABR have been analyzed. The results are compared with the international system analysis software ATHENA. The results indicate that the developed program can stably, accurately, and efficiently predict the transient accident response and safety characteristics of the lead-bismuth fast reactor system.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.893-898
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• 2014

Recently, the interior permanent synchronous motor (IPMSM) has been applied to an integrated starter and generator (ISG) for hybrid electric vehicles. In the design of such a motor, thermal analysis is necessary to maximize the power density because the loss is proportional to the power of a motor. Therefore, a cooling device as a heat sink is required internally. Generally, a cooling system designed with a water jacket structure is widely used for electric motors because it has advantages of simple structure and cooling effectiveness. An effective approach to analyze an electric machine with a water jacket is a thermal equivalent network. This network is composed of thermal resistance, a heat source, and thermal capacitance that consider the conduction, convection, and radiation. In particular, modeling of the cooling channel in a network is challenging owing to the flow of the coolant. In this paper, temperature prediction using a thermal equivalent network is performed in an ISG that has a water cooled system. Then, an experiment is conducted to verify the thermal equivalent network.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.623-626
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• 2005

Toward the practical applications, on operation of conduction-cooled HTS SMES at temperatures well below 77 K should be investigated, in order to take advantage of a greater critical current density of HTS and considerably reduce the size and weight of the system. Recently, research and development concerning application of the conduction-cooled HTS SMES that is easily movement are actively progressing in Korea. Electrical insulation under cryogenic temperature is a key and an important element in the application of this apparatus. Using multi wrapped copper by polyimide film for HIS SMES, the breakdown characteristics of models for turn-to-turn, that is surface contact model, were investigated under ac and impulse voltage at 77 K. A material that is Polyimide film (Kapton) 0.025 mm thickness is used for multi wrapping of the electrode. Statistical analysis of the results using Weibull distribution to examine the wrapping number effects on breakdown voltage under ac and impulse voltage in $LN_2$ was carried.

• 태양에너지
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• 제9권3호
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• pp.44-54
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• 1989

Heat transfer phenomena during inward melting process of the phase change material were studied experimentally. N-docosane paraffin [$C_{22}H_{46}$] is used for phase change material and its melting temperature is $42.5^{\circ}C$. Experiments were performed for melting of an initially no-sub cooled or subcooled solid in a horizontal cylinder, in order to compare and investigate the radial temperature distribution, ratio of melting and melted mass, various energy components stored from the cylinder wall, figure of the melting front in the horizontal cylinder. The solid-liquid interface motion during phase change was recorded photographically. The experimental results reaffirmed the dominant role played by the conduction at early stage, by the natural convection at longer time during inward melting in the horizontal cylinder. Ratio of melting and melted mass are more influenced by wall temperature, rather than by the initial temperature of solid. The latent energy is the largest contributor to the total stored energy.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.35-38
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• 2000

A preliminary design of gas-gp thermal switch is presented to reduce the cooldown time of superconducting system conduction-cooled by a two-stage refrigerator without liquid cryogens. The switch connects thermally the first and the second stages (ON) to take advantage of the larger refrigeration capacity at the first stage during the beginning period. After the cryogenic temperature is reached, the switch should isolate thermally the two stages (OFF) in order to reduce the heat leak to the cold end. In this paper, a new concept for the performance index is introduced to evaluate the reduction of the cooldown time and the increase of the cooling load at the same time. In addition, the design of a gas-gap switch is discussed as a closed container of several staggered concentric tubes filled with gas, which is frozen at low temperatures for the shut-off of heat without any mechanical actuation. Some of the detailed features in the design is quantitative investigated by the gas convection model in the continuum or the rarefied gas region.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.266-268
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• 2003

The neon liquefier by using GM cryocooler is designed and in process of manufacturing for the cooling of 100 hp high temperature superconductor (HTS) motor. It was used the principle of thermosyphon that the rotor of the motor is cooled by the latent heat of liquidized neon. The cold-box was designed to minimize heat loss by conduction, convection, radiation. Two heat exchanger were made to liquefy neon by the direct contact of neon gas on the cold head. As a first stage of our project, evaporation apparatus will be setup in the inner field of the cold-box and then the performance of neon liquefier will be test.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1237-1239
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• 2005

In this study, we estimate the thermal conductivity of stainless steel reinforced Bi-2223/Ag tape which was made from American Superconductor. The equipments for thermal conductivity measurement was set up using conduction cooled cryocooler. Two direction of thermal conductivity was measured. The one is the direction of cut length, and the other is direction of transverse of wounded coil with insulation material. It was observed that the thermal conductivity of transverse direction of coil was extremely lower than that of cut length direction. It was mainly seems that superconducting filaments and insulation material were effected on thermal conductivity in thermal conductivity of transverse direction.

• 한국초전도ㆍ저온공학회논문지
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• 제11권1호
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• pp.20-24
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• 2009

The superconducting property measurement system is used to acquire electrical and thermal properties on short HTS tape samples and the system is composed of specimen holder for mounting HTS tape and a magnet for applying magnetic fields externally. The magnet consists of two split racetrack windings and is designed to produce maximum 3T of center field. The temperature of specimen holder can be varied in range from 10K to 77K. The field homogeneity is required less than 300 gauss stray field contour within 20cm axially and 3cm radially from origin. We have worked on the conceptual designs of the conduction-cooled magnet for the superconducting characteristic measurement system. The measurement system will be fabricated in near future based on the design parameters presented in this paper.

• 한국자기학회지
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• 제8권5호
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• pp.317-332
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• 1998

소자화 랭동법은 전자 또는 핵의 자기 모벤트를 등온적으로 자화시킨 다음 단열상태에서 자화를 없앰으로써 온도를 내리는 방법이다. 전자의 소자화 냉동기는 교석 랭동기의 출현으로 거의 사용되지 않고 있으나 핵의 소자화 냉동기는 ${\mu}K$ 이하의 극저온을 얻을 수 있는 유일한 방법으로 극저온에서의 $^{3}He$액체 또는 $^{3}He$ 고체의 상전이, 극저온 초전도 현상, 핵의 자발질서 현상, 스핀 유리 상전이등의 연구에 많이 사용되고 있다. 핵의 소자화 냉동기는 대개 물체(시료) 전체의 온도를 내리는데 사용하나 빠른 소자화를 통해 핵만의 온도를 내리는데도 사용된다. 핵만의 온도를 내리는 냉동방법은 핵 자기 현상의 연구에 많이 이용되고 있다. 이러한 극저온을 얻기 위한 냉동법은 최첨단 기술이나 현재 국내에서는 극저온을 중점적로 연구하는 곳이 없는 실정이다. 본 논문에서는 소자화 냉동에 관한 현재의 취세를 소개하고 앞으로의 연구방향을 제시하고자 한다.

• 태양에너지
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• 제13권2_3호
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• pp.53-64
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• 1993

본 연구는 용융된 파라핀을 채운 수직원관 내의 상변화물질의 초기온도와 수직원관의 벽면온도를 변화시켰을때 관 내에서 일어나는 열전달현상을 다루었다. 자연대류의 효과는 초기과열된 액상영역 내에서 응고초기 짧은 시간에 걸쳐 일어났고, 그 후 전도열전달이 paraffin 전 영역을 지배하였다. 실험에서 관찰한 응고 형태는 상부표면에서 밀도 증가에 의한 수축공간이 발생하였으며, 그 공간의 크기는 냉각이 진행됨에 따라 증가하였다. 자연대류가 끝나자. 상경계면 상에서 수지상 결정과 mush-zone이 발견되었다. 액상 paraffin의 초기과열은 실험 전반부의 응고질량과 응고두께를 감소시키는 경향을 보였으며, 초기액상과열도와 벽면 과냉도가 큰 경우에 크게 나타났다.