• Superconductivity and Cryogenics
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• v.9 no.1
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• pp.26-30
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• 2007

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2196-2202
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• 1992

The optimum size combination of heat exchangers in a Joule-Thomson(J-T) circuit for small cryogenic systems has been sought analytically, when the circuit is combined with a two-stage Gifford-McMahon(GM) cooler. Full thermodynamic cycle analysis was carried out to predict the performance of the combined refrigeration system. Relevant convective heat transfer coefficients, the computerized properties of helium, and the refrigeration capacity curve of a typical GM cooler have been used in the analysis. The result showed that, by changing the configuration(heat exchanger area ratio) of the system, the performance of the commonly-used GM/J-T refrigerators could be optimized. For the maximum refrigeration performance, the optimum mass flow rate of the refrigerant and the relative size between the heat exchangers have been obtained, when the cooling load was 0.1W at 3.995K with the total heat exchanger area being given.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.457-463
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• 1999

The Joule-Thomson cryocooler with $H_2$gas has been developed. Cool-down characteristics and the cooling performance of a JT cryocooler have been investigated in detail. The JT cryocooler consists of JT expansion valve, heat exchanger, expansion chamber, compressed $H_2$gas storage tank, $LN_2$precooler, heater and a cryostat. The precooling process using both $GN_2$and $LN_2$was peformed to cool down the inside components of cryocooler under the maximum inversion temperature of $H_2$. The $H_2$expansion experiments have been peformed for 2-5MPa of H$_2$pressure to evaluate steady state temperatures of the cryocooler. It is found that the steady state temperatures are decreased as the H$_2$pressures are increased. The effects of cooling temperatures on the performance have been evaluated for various $H_2$and $N_2$pressures. It is seen that the cooling loads are increased, as the cooling temperature and operating pressure are increased.

• 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.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.144-149
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• 2022

A cryogenic Mixed Refrigerant Joule-Thomson refrigeration cycle was designed to be applied to the semiconductor etching process with non-flammable constituents. 3-stage cascade refrigerator, single mixed refrigerant Joule-Thomson refrigerator, and 2-stage cascade type mixed refrigerant Joule-Thomson refrigerator are analyzed to figure out the coefficient of performance. Non-flammable mixture of argon(Ar), tetrafluoromethane(R14), trifluoromethane (R23) and octafluoropropane(R218) were utilized to analyze the refrigeration cycle efficiency. The designed refrigeration cycle was adapted to cool down the coolant of HFE7200(Ethoxy-nonafluorobutane, C₄F₉OC₂H₅) with certain constraints. Maximum coefficient of performance of the refrigeration system is obtained as 0.289 for the cooling temperature lower than -100℃. The detailed result of the coefficient of performance according to the mixture composition is discussed in this study.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.10
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• pp.901-907
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• 2000

The conceptual determination of mixed-refrigerant (MR) for a closed Joule-Thomson cryocooler is described in this paper. The thermodynamic cycle design was mainly considered to develop a cryocooler by using a compressor of domestic air-conditioning unit. The target cooling performance of the designed cryocooler is 10 W around 70 K with less than 5 kJ/kg enthalpy rise. The systematic approach of choosing a proper refrigerant among 20 different kinds of mixture for such cryogenic temperature was introduced in detail. The main components of the cryocooler are compressor, evaporator, oil separator, after-cooler, counterflow heat exchanger, and J-T expansion device. Due to the limitation of the compressor operation range, the temperature after the compression was limited below $117^{\circ}C$ (390 K) and the temperature before compression was restricted above $5^{\circ}C$ (278 K). 20 atm of discharging pressure (high pressure) and less than 3 atm suction pressure (low pressure) were the design conditions. The inlet temperature of a counterflow heat exchanger in the high Pressure side was about 300 K. The proper composition of the mixed refrigerant for the designed J-T cryocooler is 15% mol of$ N_2, 30% mol of $CH_4,\; 30% mol\; of C^2H^ 6,\; 10%\; mol\; of\; C_3H_8\; and \;15%\; mol\; of\; i-C_4H_10$.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.86-90
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• 2007

The cryoprobe used in cryosurgery should be fabricated in milimeter-order size for its practical usage. In general a miniature J-T(Joule-Thomson) refrigerator is applied to a cryoprobe. In case of the miniature J-T refrigerator, the mass flow rate of working fluid is small due to considerable friction in a minute flow path. For that reason, the miniature J-T refrigerator has a limited cooling power. To obtain the large cooling power from the J-T refrigerator, the refrigerator should have large mass flow rate and effective J-T temperature drop. These quantities are closely related to the geometry of the heat exchanger and the expansion nozzle in a cryoprobe, and are contradictory. The large mass flow rate leads to the small J-T temperature drop and vice versa in the miniature J-T refrigerator. Therefore, the optimal design of a cryoprobe to achieve maximum cooling power at fixed tube size and fixed operating temperature is required. This paper presents the design procedure of such case.

• 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 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.

• 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.