• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.12
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• pp.633-639
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• 2006

High temperature superconductor (HTS) winding coil is one of the key component in superconducting device fabrication. Double-pancake style coils are widely used for such application. High resistance between pancake coils greatly affects the machine design, operating condition and thus the stability. In order to reduce such resistance, experimentalists are looking for efficient and damage free coil connecting methods. In this respect, here we proposed parallel joining method to connect the coils. This is to do crossly joining with HTS tapes on two parallel HTS tapes. Joint samples between two parallel HTS tapes were prepared by using HTS tapes and current-voltage (I-V) characteristic curves were investigated at liquid nitrogen temperature i.e., 77.3 K. A 20 cm length joint connected between two parallel HTS tapes shows $32.5n{\Omega}$, for currents up to 250 A. A small HTS magnet, having two double pancake sub-coils connected together through new parallel joint method was fabricated and their current-voltage (I-V) characteristic curve was investigated. At 77.3K, critical current(Ic) of 97 A and resistance of $55n{\Omega}$ for currents upto 130 A were measured. At operating current 86 A lower than Ic, Joule heats generated in whole magnet and at joint region between sub-coils were 226 mW and 0.4 mW, respectively. Low Joule heat generation suggests that this joining method may be used to fabricate HTS magnet or windings.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.91-91
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• 2008

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.1032-1037
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• 2011

In this study, simulation and optimization works for a demethanizer column have been performed to obtain ethane and heavier products from a pretreated natural gas stream. Pretreated natural gas feed stream was partially condensed after being precooled by exchanging heat with demethanizer top vapor stream and by using an external refrigeration cycle with a propane refrigerant. Vapor stream was cooled further and partially condensed through a turbo-expander. The power generated from the expansion of turbo-expander was delivered to the compressor for the residue gas compression. Liquid stream was cooled by Joule-Thomson expansion valve and was fed to the middle section of the demethanizer. Recovery percent of ethane for feed natural was set to 80% and methane to ethane molar ratio was fixed as 0.0119. On the other hand, some of the cold heat could be recovered by splitting the feed stream and by exchanging heat with side reboiler in order to reduce the heat duty in the propane refrigeration cycle.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1302-1308
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• 2006

The unsteady Hartmann flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer taking the Hall effect into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.60-63
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• 2009

Most J-T (Joule-Thomson) refrigerators use a Giaque-Hampson type heat exchanger due to its excellent thermal performance and compactness. The cryoprobe (cryosurgical probe) treating prostate cancer usually has a dimension of 17 gauge (1.6 mm diameter), so it does not have enough space to bear a Giaque-Hampson type heat exchanger. In this paper, the triplet heat exchanger is adopted as the heat exchanger of cryoprobe, and the performance is investigated with an experimental test. The result shows that the triplet heat exchanger can be substituted for Giaque-Hampson type heat exchanger in the application of cryosurgery.

• Progress in Superconductivity and Cryogenics
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• v.12 no.4
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• pp.41-45
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• 2010

Miniature Joule-Thomson refrigerators have been widely used for rapid cooling of infrared detectors, optoelectronic device, and integrated circuits of micro electronics. The typical J-T refrigerator consists of the recuperative heat exchanger with the double helical tube and fin configuration, J-T nozzle, a mandrel, Dewar and a compressed gas storage bottle. In this study, to predict the thermodynamic behaviors of the refrigerator with a compressed gas storage bottle during the cool-down time, numerical study of transient characteristics for a J-T refrigerator was developed. A simplified transient one.dimensional model of the momentum and energy equations was simultaneously solved to consider the thermal interactions of the each component of the refrigerator. To account for effects of the thermal mass of the solid, the heat capacities of the tube, fins, mandrel and Dewar are considered. The results show the charged gas pressure of the gas storage bottle has significant effects on the performance of the J-T refrigerator. At the elevated gas pressure of the gas storage bottle, the large capacity of the compressed gas storage does not need to get the fast cool-down performance of the J-T refrigerator in the cool-down stage.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.94-97
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• 2005

For the fabrication of poly-crystalline silicon ingot, CCCC (Cold Crucible Continuous Casting) method under a high frequency alternating magnetic field, was utilized in order to prevent crucible consumption and ingot contamination and to increase production rate. In order to effectively and continuously melt and cast silicon, which has a high radiation heat loss due to the high melting temperature and a low induction heating efficiency due to a low electric conductivity, Joule and pinch effects were optimized. Throughout the present investigation, poly-crystalline Si ingot was successfully produced at the casting speed of above 1.5 mm/min under a non-contact condition.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.18 no.2
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• pp.121-129
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• 1989

헬륨을 이용한 극저온 냉동기는 압축기(compressor)을 통하여 압력을 10-20 기압 정도로 높혀준후 여러 단계의 열교환기(heat exchanger)를 통하여 상전위온도(maximum inversion temperature) 이하로 떨어뜨린후 Joule-Thomson 밸브를 통하면 4K까지 온도가 떨어진다. 이때 압력은 1기압 정도이며 헬륨가스는 액체로 변한다. 본 연구의 목적은 Gifford-McMahon 냉동기와 Joule-Thomson 냉동기의 혼합형인 극저온 냉동기를 설계, 제작하여 죠셉슨(Josephson) 소자를 이용한 SQUID(초전도양자 간섭장치), 여러 종류의 탐지기, 컴퓨터 소자 개발 등을 위한 냉동기로 사용하는데 그 목적이 있다. 개발되는 법동기의 용량은 1 W이며, 최저온도는 4K 정도가 된다.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.131-136
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• 2001

In this paper, a high-temperature superconductor(HTS) current lead operating in current sharing mode is described. The minimum heat dissipation and the optimum safety factor(cross-sectional area) is obtained analytically for partial current sharing HTS leads. It is assumed that the current lead is in conduction cooled state, and the sheath material is the alloy of silver and gold. The reduced cross-sectional area results partial current sharing state, and consequently reduces conduction heat transfer, but the Joule heat generation is increased. The optimized HTS current lead is different from the conventional copper leads. In the copper leads, the minimum heat dissipation is obtained for the zero gradient of temperature at warm end. However, the temperature gradient at warm end is not zero when the HTS lead operates at minimum dissipation state.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1473-1478
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• 2011

In this study, simulation and optimization works for a demethanizer column have been performed to obtain ethane and heavier products from a pretreated natural gas stream. Pretreated natural gas feed stream is partially condensed after being precooled by exchanging heat with demethanizer top vapor stream and by using an external refrigeration cycle with a propane refrigerant. Vapor stream is furtherly cooled and partially condensed through a turbo-expander and the power generated from the expansion of turbo-expander was delivered to the compressor for the residue gas compression. Liquid stream is being cooled by Joule-Thomson expansion valve and is fed to the middle section of the demethanizer. Ethane recovery percent for feed natural gas was set to 75% and methane to ethane molar ratio was fixed as 0.015. Propane refrigeration heat duty was reduced by splitting the feed stream and to exchange heat with side reboiler.