• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2008년도 High Temperature Superconductivity Vol.XVIII
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• pp.91-91
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• 2008

• 대한기계학회논문집
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• 제16권11호
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• pp.2196-2202
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• 1992

본 연구에서는 초전도 양자 간섭장치(SQUID, superconductiong quantum inte- rference device)를 냉각시킬 수 있는 정도의 소용량(3.995K에서 0.1W)의 GM/J-T 냉동 기에 대하여 요구되는 냉각용량을 만족시키면서 최대의 성능을 나타낼 수 있는 열교환 기의 면적배분 조건을 구하였다. 즉 냉동 성능을 알고 있는 상용 2단 GM 냉동기와 소형 극저온 냉동기에 널리 사용되는 열교환기로 이루어진 복합적인 GM/J-T 냉동기에 대하여 열교환기 총면적이 주어졌을 때, J-T 회로내의 냉매(헬륨)의 유량과 각 열교환 기 전열 면적의 비를 변수로 최적설계를 행하였다.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권2호
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• pp.39-50
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• 2000

Thermodynamic cycle analysis is presented to estimate the maximum liquefaction rate of hydrogen for various systems using a Gifford-McMahon(GM) cryocooler. Since the present authors` previous experiments showed that the gaseous hydrogen was liquefied approximately at the rate of 5.1 mg/s from the direct contact with a commercial two-stage GM refrigerator, this study has been proposed to predict how much the liquefaction rate can be increased in different configurations using the GM cooler and with improved heat exchangers. The optimal operating conditions have been analytically sought with real properties of normal hydrogen for the Linde-Hampson(L-H) system precooled by single-stage GM, the direct-contact system with two-stage GM, the L-H system precooled by two-stage GM, and the direct-contact system with helium GM-JT (Joule-Thomson). The maximum liquefaction rate has been predicted to be only about 7 times greater than the previous experiment, even though the highly effective heat exchangers may be employed. It is concluded that the liquefaction rate is limited mainly because of the cooling capacity of the commercially available GM cryocoolers and a practical scale of hydrogen liquefaction is possible only if the GM cooler has a greater capacity at 70-100 K.

• 설비공학논문집
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• 제6권1호
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• pp.11-19
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• 1994

An optimal design for Gifford-McMahon/Joule-Thomson(GM-JT) refrigerators was performed by a numerical method. The design goal was to meet the cooling requirement for MRI systems, which was 3 Watt at 4 K. A general cycle analysis program was written to calculate the cooling capacity of the GM-JT refrigerators for the givenstage GM refrigerator. The program was executed for a specific refrigerator with various design parameters. The optimal values for the maximum cooling were found for the sizes of the heat exchangers, the mass flow rate of helium, and the compression pressure.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.118-122
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• 2003

Pulse tube refrigerator, which has no moving parts at its cold section, is attractive fer obtaining higher reliability, simpler construction and lower vibration than Stilting refrigerator or Gifford-McMahon refrigerator. Commonly used means to achieve optimum performance of Stilting type pulse tube refrigerator is an inertance tube. The use of inertance tube is a simple way to generate the phase shift needed to make pulse tube refrigerator operate as efficiently as Stilting refrigerator. In this study, the performance of the inertance pulse tube refrigerator (IPTR) was investigated experimentally. An in-line type IPTR consists of a linear compressor with two reciprocating pistons driven by linear motors, which makes pressure waves, a regenerator a pulse tube with the inertance tube, and a reservoir, The dynamic pressures (the compressor, pulse tube, reservior) and the temperature at the cold heat exchanger are measured to explore the dependence of the inertance tube on the performance of the IPTR. The experimental results show the dependency of cool-down characteristics, no-load temperature and amplitude of the pressures on the length and diameter of the inertance tube.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.194-197
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• 1999

Thermodynamic cycle analysis has been performed to maximize the liquid amount for two hydrogen liquefaction systems using two-stage GM(Gifford-McMahon) refrigerator. the optimal operating conditions have been analytically sought with real properties of normal hydrogen for the two-stage GM direct contact system and the two-stage GM precooled L-H (Linde-Hampson) system. In the precooled system, there existed optimal values for compressed mass flow and compressed pressure to maximize the liquefied mass. It was recommended to use a cryocooler, which had a large precooling capacity between 70 and 100K.

• 한국초전도ㆍ저온공학회논문지
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• 제6권2호
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• pp.40-45
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• 2004

The experimental results of the G-M (Gifford-McMahon) type pulse tube refrigerators are presented in this paper. The pulse tube refrigerator, which has no moving parts at its cold section, is attractive in obtaining higher reliability, simpler construction, and lower vibration than any other small refrigerators. The objectives of this study are to develop the design technology of the G-M type pulse tube refrigerator and acquire its application methods for replacing G-M cryocooler. As a preliminary test, the refrigeration performances of the basic, orifice, and double inlet pulse tube refrigerators were investigated. The lowest temperature obtained in the one-stage pulse tube refrigerator was 34.4K and the refrigeration capacity at the optimum operation condition was 23W at 80K. And the lowest temperature of the second stage cold head in the two-stage pulse tube refrigerators was 18.3K and the refrigeration capacities at optimum condition were 0.45W at 20K and 20W at 80K, respectively. Finally, the lowest temperature obtained in the three-stage pulse tube refrigerator was 29.8K and the refrigeration capacity at the optimum operation condition was 1.3W for 40K and 5W for 70K.

• 설비공학논문집
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• 제11권3호
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• pp.349-358
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• 1999

Thermodynamic cycle analysis has been performed to maximize the liquid amount for various hydrogen liquefaction systems using GM(Gifford-McMahon) refrigerator. Since the present authors' previous experiments showed that the liquefaction rate was approximately 5.1mg/s in a direct contact with a commercial GM refrigerator, the purpose of this study is to predict how much the liquefaction rate can be increased in different configurations and with improved heat exchanger performance. The optimal operating conditions have been analytically sought with real properties of normal hydrogen for the single-stage GM precooled L-H(Linde-Hampson) system, the two-stage GM direct contact system, the two-stage GM precooled L-H system and the two-stage helium GM-JT (Joule-Thomson) system. The maximum liquefaction rate has been predicted to be only about 7 times greater than the previous experiment, when the two-stage precooling is employed and the effectiveness of heat exchangers approaches to 99.0%. It is concluded that the liquefaction rate is limited mainly by the cooling capacity of the current GM refrigerators and a larger scale of hydrogen liquefaction is possible with a greater capacity of cryocooler at 60-70 K range.

• 한국초전도ㆍ저온공학회논문지
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• 제12권2호
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• pp.29-33
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• 2010

The experimental results of the 2 stage Gifford-McMahon(GM) type pulse tube refrigerator (PTR) or cryopump are presented in this paper. The objectives of his study are to develop design technology of the integral type 2 stage PTR which rotary valve is directly connected to he hot end of the regenerator and acquire its improved performance. Design of the 2 stage PTR is conducted by FZKPTR(Forschungs Zentrum Karlsruhe Pulse Tube Refrigerator) program for the design of pulse tube refrigerators. The fabricated PTR has U-type configuration and incorporates orifice valve, double-inlet valve and reservoir as phase control mechanism. Rotary valve is used to make pulsating pressure and is directly connected to inlet of $1^{st}$ stage regenerator. From experiments, cooling performance map and pressure waveform at each point were measured for different operating frequencies. Experimental results show the best cooling performance with 2 Hz operation in spite of small pressure amplitude. The lowest temperatures of the 2 stage PTR were 16.9 K at the second stage and 58.0 K at the first stage. The cooling capacities achieved were 14.4 W at 79 K, the first stage and 3.6 W at 29 K, the second stage.

• 대한설비공학회지:설비저널
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• 제18권2호
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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.