• 기계와재료
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• v.23 no.3
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• pp.156-163
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• 2011

쥴톰순 냉동기는 스터링 냉동기, GM 냉동기, 스터링형 및 GM형 맥동관 냉동기 등 기계적 극저온냉동기에 비해 단순한 구조, 수 초의 급속한 냉각특성을 장점으로 중대형의 가스액화사이클 뿐만 아니라 적외선검출기의 급속냉각, 저온수술 등 다양한 분야에서 널리 사용되어지고 있다. 일반적으로 100K 이하의 작동온도 및 수 초 수준의 빠른 냉각을 요구하는 적외선검출기의 냉각을 위해서는 수 백기압 이상 고압의 질소 및 아르곤 가스를 사용하는 쥴톰슨 냉동기가 주로 사용되고 있다. 쥴톰슨 냉동기는 핀-관(fin-tube) 형태의 열교환기와 열교환기의 구조적 기반을 제공하는 멘드렐(mandrel), 쥴톰슨 노즐 등으로 구성되며, 열교환기의 열전달 성능 및 유량조절기구의 특성은 냉동기 저온부의 냉각온도, 냉각시간 및 운전시간에 큰 영향을 미친다.

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.56-63
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• 2001

The thermal stability conditions are investigated for superconducting magnet systems cooled conductively by cryocooler without liquid cryogens. The worst scenario in the systems is that the heat generation in the resistive state exceeds the refrigeration. causing a rise in the temperature of the magnet winding and leading to the burnout. It is shown by an analytical solution that in the continuous resistive state, the temperature may increase indefinitely or a stable steady-state may be reached, depending upon the relative size of the magnet with respect to the refrigeration capacity of the cryocooler. The stability criteria include the temperature-dependent Properties of the magnet materials and the refrigeration characteristics of the cryocooler. A useful graphical scheme is Presented and discussed to demonstrate the physical importance of the results.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.171-173
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• 2003

The cryostat or dewar have been widely used for making and maintaining cryogenic and vacuum environments. The thermal performances of such cryogenic vacuum system mainly depend on the radiation heat transfer between hot and cold surface The characteristics of radiation heat transfer are complicated, because amounts of heat transfer depend on view factor, emissivities, and areas of thermal elements. In this study, the analysis of the radiation heat transfer in the small cryogenic vacuum system was performed using the surface to surface radiation model for evaluation of the required cooling capacity of the cryocooler.

• 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.

• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.65-68
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• 2009

The Stirling cryocoolers have been widely used for the cooling of the infrared detector(InSb, HgCdTe, and etc,) and HTS(High Temperature Superconductor) to the cryogenic temperature. The monobloc Stirling cryocoolers with the rotary compressor are applicable to the cooling device for the compact mobile thermal imaging system, because the cryocoolers have the compact structure and light weight. The typical performance factors of the Stirling cryocooler are the cool-down time, cooling capacity at the desired temperature (80 K), the electric input power and COP. The above performance factors depend on the operating conditions such as the charging pressure of the helium gas, the thermal environment and etc.. In this study, the effects of the thermal environment (temperature of 241, 293, and 333 K) on the performance of the cryocooler were investigated by experiments. The results show the effects of the temperature of the thermal environment on the cooling capacity and input power.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.3
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• pp.141-148
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• 2015

The cryogenic cooling system should maintain the HTS power cable below 77 K. As the length of HTS power cables has increased, there have been many efforts to develop large capacity cryocoolers. Brayton, Joule-Thomson, and Claude refrigerators were considered for the large capacity cryocooler. Among the various cryocoolers, the Brayton refrigerator is the most competitive in terms of the HTS power cable. At present, it is thought that a 10-kW class refrigerator will be able to be used as a unit cooling system for the commercialization of HTS power cables in the near future. The Brayton refrigerator is composed of recuperative heat exchangers, a compressor, and a cryogenic turbo expander. Among the various components, the cryogenic turbo expander is the part that decreases the temperature, and it is the most significant component that is closely related with overall system efficiency. It rotates at high speed using high-pressure helium or neon gas at cryogenic temperatures. This paper describes the design of a 300-W class Brayton refrigeration cycle and the cryogenic turbo expander as a downscale model for the practical 10-kW class cycle. Flow and structural analyses are performed on the rotating impeller and nozzle to verify the efficiency and the design performance.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.141.2-141.2
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• 2014

크라이오 펌프는 반도체 임플란타 공정, OLED 분야, 신소재 개발, 표면분석 및 처리, 의료분야, 입자가속기, 핵융합 등 다양한 진공분야에 응용되는 고진공용 극저온펌프이다. 특히 향후 디스플레이 분야에서 OLED가 시장을 주도할 것으로 예상되는 가운데, 점점 대형화 되어가는 OLED 장비에 가장 적합한 고진공 펌프로써 크라이오 펌프가 주목을 받고 있다. OLED 디스플레이 제조공정 중에서도 화소형성 공정을 위한 챔버는 특별히 진동특성에 민감하다. 유기물 증착공정을 진행하기 위해서 글라스 전단에 쉐도우 마스크를 설치하는데, 글라스의 크기가 증가하면서 초래된 처짐문제 그리고 장비의 진동특성과 글라스와 마스크 사이의 간섭문제 등이 제품의 수율에 큰 영향을 미치면서 향수 시급히 해결해야 할 필수 과제로 주목 받고 있다. 그러나 대부분의 상용 크리이오 펌프는 G-M형식의 냉동기를 장착하기 때문에 그 원리 상 제조사에 관계없이 일반적으로 큰 진동특성을 가진다. 이에 GVT에서는 OLED 공정에 적합한 보다 정숙하고 진동특성이 개선된 550 mm구경의 크라이오 펌프 개발을 진행하였다. 그 결과 펌프의 성능은 동종 경쟁모델과 동등 이상의 수준을 유지하고 진동성분은 동종모델 대비 50%이상 개선된 펌프를 개발할 수 있었다. 그리고 시장에 보다 좋은 제품을 출시하기 위해서 현재 성능과 진동특성을 계속해서 튜닝 중에 있다. 진동개선은 크게 2가지 방향으로 진행되었는데, 첫째는 펌프 측면에서 진행한 것이고 둘째는 냉동기 측면에서 진행한 것이다. 후자는 현재 대외비로 개발을 진행 중에 있으며 본 발표에서는 전자에 관한 것으로 펌프 측면에서 진동특성을 개선한 부분이다. 결국 크라이오 펌프의 진동은 진동원인 냉동기에서 발생하는 것이므로 냉동기와 펌프를 구조적으로 고립시키는 방법을 사용하였다. 즉, 냉동기와 펌프 사이에 댐핑 시스템 플랜지를 장착하여 진동원인 냉동기로부터 진동성분이 펌프 측으로 전달되는 것을 차단한 것이 본 기술의 핵심이다. GVT에서는 당 기술로 국내특허등록을 완료하였다(특허-10-1289394_진동 저감을 위한 댐핑 플랜지 조립체 및 이를 갖는 크라이오 펌프).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.552-560
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• 1997

Analysis is performed to determine the optimal lengths or cross-sectional areas of refrigerator-cooled current leads that can be applied to the conduction-cooled superconducting systems. The binary current lead is composed of the series combination of a normal metal at the upper(warm) part and a high $T_c$ superconductor(HTS) at the lower(cold) part. The heat conduction toward the cold end of HTS part constitutes a major refrigeration load. In addition, the joint between the parts should be cooled by a refrigerator in order to reduce the load at the low end and maintain the HTS part in a superconducting state. The sum of the work inputs required for the two refrigeration loads needs to be minimized for an optimal operation. In this design, three simple models that depict the refrigeration performance as functions of cooling temperature are developed based on some of the existing refrigerators. By solving one-dimensional conduction equation that take into account the temperature-dependent properties of the materials, the refrigeration works are numerically calculated for various values of the joint temperature and the sizes of two parts. The results show that for given size of HTS, there exist the optimal values for the joint temperature and the size of the normal metal. It is also found that the refrigeration work decreases as the length of HTS increases and that the optimal size of normal metal is quite independent of the size of HTS. For a given length of HTS, there is an optimal cross-sectional area and it increases as the length increases. The dependence of the optimal sizes on the refrigerator models employed are presented for 1kA leads.