• 한국조리학회지
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• 제14권2호
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• pp.286-292
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• 2008

The purpose of this study was to examine the effects of freezing and thawing methods on the quality of pork meat. The freezing methods for pork meat were the cryogenic freezing with liquid nitrogen gas, fast freezing at $-70^{\circ}C$ and normal freezing at $-20^{\circ}C$. The thawing methods were tested on low temperature thawing at refrigerative temperature($4^{\circ}C$), room temperature($20^{\circ}C$), high temperature($60^{\circ}C$) and using microwave. The quality of pork meat frozen by cryogenic methods was better than those of fast and normal freezing methods. The cooking hardness of pork meat frozen by cryogenic method showed the highest value as 1,898 g. In case of fast freezing, the hardness of pork meat was 1,472 g and that of normal frozen pork meat was 1,541 g. The high cooking hardness value of cryogenic frozen pork meat showed that the cryogenic freezing method made less freeze damage like textural softness. The drip-loss of pork meat thawed at refrigerative temperature($4^{\circ}C$), room temperature($20^{\circ}C$), high temperature($60^{\circ}C$) were shown lower than that of microwave thawing. The cooking hardness of pork meat that was thawed by microwave showed the lowest value among the thawing methods. The cryogenic freezing was the most useful freezing method for preserving quality, decreasing the freeze damage of pork meat. And thawing at refrigerative temperature was the most effective method to prevent quality loss and weight loss by drip-loss.

• 반도체디스플레이기술학회지
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• 제20권2호
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• pp.19-24
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• 2021

As the size of semiconductor devices decreases, the etching pattern becomes very narrow and a deep high aspect ratio process becomes important. The cryogenic etching process enables high aspect ratio etching by suppressing the chemical reaction of reactive ions on the sidewall while maintaining the process temperature of -100℃. ESC is an important part for temperature control in cryogenic etching equipment. Through the cooling path inside the ESC, liquid nitrogen is used as cooling water to create a cryogenic environment. And since the ESC directly contacts the wafer, it affects the temperature uniformity of the wafer. The temperature uniformity of the wafer is closely related to the yield. In this study, the cooling path was designed and analyzed so that the wafer could have a uniform temperature distribution. The optimal cooling path conditions were obtained through the analysis of the shape of the cooling path and the change in the speed of the coolant. Through this study, by designing ESC with optimal temperature uniformity, it can be expected to maximize wafer yield in mass production and further contribute to miniaturization and high performance of semiconductor devices.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.43-48
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• 2023

Polymer composites, especially glass fiber reinforced polymer (GFRP) are finding ever-increasing applications in areas such as superconductivity, space technology, cryogenic rocket engines, and cryogenic storage vessels. Various components made of polymer composites are much lighter than their metallic counterparts but have equivalent strength for ultra-low temperature applications. In this paper, we have investigated the tensile properties of an indigenously prepared unidirectional cylindrical hollow composite tube for its use as a neck of the cryogenic vessel. XRD and SEM of the tube are completed before cryogenic conditioning to ascertain the fiber and resin distribution in the matrix. The result shows that for composites, after 15, 30, 45, and 60 minutes of cryogenic conditioning at 77K in a liquid nitrogen bath, the strength and modulus increase significantly with the increase of strain rate and reach the optimum value for 45 minutes of conditioning. The results are encouraging as they will be helpful in assessing the suitability of GFRP in the structural design of epoxy-based components for cryogenic applications.

• 한국안전학회지
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• 제28권2호
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• pp.1-5
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• 2013

Liquefied Natural Gas is liquefied at the condition of atmosphere pressure and cryogenic temperature. LNG is exposed very long time under the cryogenic temperature and high pressure, and it is very important to retain the structural safety in this envelopment. Until now, the material which are composing the storage tank of LNG ship has experimented at room temperature, so it is not enough to apply for the design at the cryogenic temperature. The purposes of this study are investigated mechanical properties for aluminum alloy. To evaluate tensile and fatigue test for aluminum alloy, it was considering static and fatigue conditions at room and cryogenic temperature. S-N curves were designed at both temperature respectively. Also, P-S-N curve was performed statistical method by JSME-S002.

• 한국초전도ㆍ저온공학회논문지
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• 제11권2호
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• pp.37-40
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• 2009

A mixed working fluid has a potential to widen the operation temperature range of the thermosiphon. In this study, the thermosiphon using $N_2\;and\;CF_4$ mixture as the working fluid is fabricated and tested to verify its transient thermo hydraulic characteristic. A transparent pyrex glass tube was used for the thermosiphon itself and the vacuum chamber was also fabricated by glass to visualize the internal state of thermo siphon. Onset of condensation temperature was related to the partial pressure of $CF_4$. Two solidifications were observed and condensate temperature range of mixed working fluid was from 160K to 70.7K with $N_2$ 25% composition.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.1048-1051
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• 2001

This paper presents an analytical and experimental study of a cryogenic machining for precision hard turning. A cryogenic circulation system is designed and mounted on the top of the tool insert. The machining process used is facing operation on a CNC turning center with dry and cryogenic conditions. The tool temperature and cutting forces are measured by the K-type thermocouple and by a three-component Kistler dynamometer, respectively. Both data are fed into the data acquisition program through an A/D card. Surface roughness and form accuracy of the machined surface are measured by WYKO NT2000. It is also found that surface roughness and form accuracy with cryogenic cooling are better than those with no coolant.

• 한국초전도ㆍ저온공학회논문지
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• 제17권3호
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• pp.41-46
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• 2015

Recently, the development of the HTS power cable is actively promoted. As the length of HTS power cable increases, there have been many efforts to develop large capacity cryocooler. Among the various cryocooler, the Brayton refrigerator is the most competitive for HTS power cable. The Brayton refrigerator is composed of recuperative heat exchangers, a compressor, and a cryogenic turbo expander. In these components, the cryogenic turbo expander is a part to decrease the temperature and it is the most significant component that is closely related with overall system efficiency. It rotates with high speed using a high-pressure helium or neon gas at cryogenic temperature. This paper describes the design of a 10 kW class Brayton refrigeration cycle and the cryogenic turbo expander. Flow and structural analysis are performed for the rotating impeller and nozzle to verify the efficiency and the design performance.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권2호
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• pp.74-79
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• 2009

The performance of cryogenic refrigerator greatly depends on the effectiveness of heat exchanger, which generates major entropy at low temperature. There are numerous types of heat exchanger available, but it is not easy to apply most of them to cryogenic application because the cryogenic heat exchanger must have high effectiveness value as well as small conduction loss in the environment of considerable temperature difference. In this paper, two kinds of heat exchanger are noticeably introduced for high-effectiveness miniature cryogenic recuperator(recuperative heat ex-changer). Also, the flow mal-distribution problem, which is a critical issue of performance deterioration in a high-effectiveness recuperator, is addressed with simplified model, and its alleviation method is discussed.

• 대한기계학회논문집
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• 제16권6호
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• pp.1099-1107
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• 1992

본 연구에서는 극저온에서의 스트레인 게이지의 특성을 결정하기 위하여 이태 리의 표준기관인 IMGC (Istituto Di Metrologia "G.Colonnett")를 중심으로 세계의 측 정표준 기관과 대학이 참여하는 라운드 로빈(round robin) 시험이 진행되고 있다. 국내에서도 이 계획에 참여하여 본 연구를 수행하였다. 라운드 로빈 시험계획의 궁 극적인 목적은 세계의 주요 스트레인 게이지에 대해 여러가지 험조건에 의한 시험결과 를 가지고 극저온 환경에서의 변형측정에 이용될 수 있는 최적의 스트레인 게이지, 시 험재료, 전선연결, 시험장치 등의 시험조건을 선택하는 것이다. 이 목적을 위하여 본 연구에서는 가장 널리 쓰이는 3종류의 스트레인 게이지-미국Micro-Measurement, 일본 Kyowa, 독일 Hottinger Baldwin Mestechnik-에 대한 겉보기 변형률 대 온도의 곡선을 시험을 통하여 4.2K로 부터 293K까지의 온도 범위에서 구한다. 사용된 시편 은 스테인레스 강(AISI 316LN), 구리(Cu), 알루미늄(Al)이고 온도는 액체헬륨과 액체 질소를 이용하여 변화시켰으며, 그외의 모든 시험조건은 국제 법정계량기구(OIML) 규 정에 따라 모든 기관이 통일되도록 하였다.통일되도록 하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.163-167
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• 2003

The large deformation at cryogenic temperature would be one of the effective methods to produce large bulk UFG materials. The effects of annealing temperature 150∼300$^{\circ}C$, on microstructure and mechanical properties of the sheets received 85% reduction at cryogenic temperature were investigated. In comparison with those at room temperature. Annealing of 5083 Al alloy deformed 85%, at 200$^{\circ}C$ for an hour, results in the considerable increase of tensile elongation without the great loss of strength and the occurrence of equiaxed grains less than 300nm in diameter.