• Title/Summary/Keyword: Liquid Nitrogen

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Performance evaluation of 80 GHz FMCW Radar for level measurement of cryogenic fluid

  • Mun, J.M.;Lee, J.H.;Lee, S.C.;Sim, K.D.;Kim, S.H.
    • Progress in Superconductivity and Cryogenics
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    • v.23 no.4
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    • pp.56-60
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    • 2021
  • The microwave Radar used for special purposes in the past is being applied in various areas due to the technological advancement and cost reduction, and is particularly applied to autonomous driving in the automobile field. The FMCW (Frequency Modulated Continuous Wave) Radar can acquire level information of liquid in vessel based on the beat frequency obtained by continuously transmitting and receiving signals by modulating the frequency over time. However, for cryogenic fluids with small impedance differences between liquid medium and gas medium, such as liquid nitrogen and liquid hydrogen, it is difficult to apply a typical Radar-based level meter. In this study, we develop an 80 GHz FMCW Radar for level measurement of cryogenic fluids with small impedance differences between media and analyze its characteristics. Here, because of the low intrinsic impedance difference, most of the transmitted signal passes through the liquid nitrogen interface and is reflected at the bottom of the vessel. To solve this problem, a radar measurement algorithm was designed to detect multiple targets and separate the distance signal to the bottom of the vessel in order to estimate the precise position on the liquid nitrogen interface. Thereafter, performance verification experiments were performed according to the liquid nitrogen level using the developed radar level meter.

Experimental study on the applicability of liquid air as the refrigerant in artificial ground freezing for subsea tunnels (해저터널을 위한 동결공법 냉매로서의 액화공기 적용성에 대한 실험적 연구)

  • Son, Young-Jin;Choi, Hyeungchul;Moon, Hung-Man;Choi, Hangseok;Ko, Tae Young
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.18 no.2
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    • pp.175-181
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    • 2016
  • In this paper, the liquid air was selected as the refrigerant in artificial ground freezing to be used for rapid ground freezing and to reduce the risk of suffocation and the applicability of liquid air was verified. In order to evaluate the stability of the liquid air, the oxygen concentration of mixtures with liquid nitrogen and liquid oxygen was experimentally examined to meet the oxygen concentration criteria in the Occupational Safety and Health Act. In addition, the effects of the mixture ratio of liquid nitrogen and liquid oxygen, pressure and flow rate change in the storage vessel on the oxygen concentration in the liquid air were investigated. As a result, the ratio of liquid nitrogen and liquid oxygen 8: 2 was shown to meet the oxygen concentration standards. Pressure and flow rate change in the storage vessel did not have significant effects on the oxygen concentration in the liquid air.

Analysis and Experiment on Cryogenic Refrigeration Using Solid Nitrogen (고체 질소를 이용한 극저온 냉동의 해석 및 실험)

  • 변정주;이윤숙;장호명
    • Progress in Superconductivity and Cryogenics
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    • v.3 no.2
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    • pp.77-83
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    • 2001
  • The thermal characteristics of solid nitrogen are investigated by experiment and analysis for the purpose of evaluating its feasibility as a cooling medium for HTS (high T$_{c}$ superconductor) magnets. A cryostat to refrigerate a liquid-nitrogen container well below its freezing temperature with a 2-stage GM cryocooler is designed and constructed. The spatial distribution of temperature is measure as a function of time during the freezing and melting processes. from which the thermal diffusivity of solid nitrogen can be approximately calculated. the freezing process is formulated and solved by the integral method with an assumption of phase equilibrium at the solid-liquid interface and experimental observation. It may be concluded that the thermal diffusion in solid phase is much slower than in liquid and the degree of super-saturation is quite severe in the solidification of nitrogen.n.

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A Study on the Thermal Analysis for the Robotic Arm of the Cord Blood Storage Tank (제대혈 용기 내부 로봇 암의 열해석에 관한 연구)

  • Yun, Sang-Kook;You, Sam-Sang
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.5
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    • pp.724-729
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    • 2008
  • Umbilical cord blood has been recently considered an attractive potential alternative as a source of stem cell transplantation to curing diseases such as leukemia, cancers, immune disorders. Normally the stored system of the umbilical cord blood specimen is equipped with a computer-controlled robotic arm that enables the samples to locate the identification places in liquid nitrogen tank at regulated temperature as about $-196^{\circ}C$. As the half of robotic arm is in the air and the rest part is submerged in liquid nitrogen, the temperature of robotic arm varies from ambient to liquid nitrogen temperature. In this study the temperature variation of upper part of arm above tank lid was thermally analysed by using the commercial code of Ansys. The result of analysis was that the upper part of robotic arm was seriously frozen due to heat transfer from liquid nitrogen as low as -$120^{\circ}C$. In order to solve the frost problem of robotic arm, small PTFE tube block as resistance material was introduced into the lower part of tank lid instead of the whole stainless steel(SUS) robotic arm. The results showed that the temperature of robotic arm above the lid was higher enough, and this method would be one of the very effective measure to solve the problem.

Thermal diffusion experiment of impulsive heat in subcooled liquid nitrogen (과냉 액체질소 내에서 순간적 열확산 실험)

  • Choi, J.H.;Ha, J.C.;Byun, J.J.;Chang, H.M.;Kim, H.M.;Ko, T.K.
    • Progress in Superconductivity and Cryogenics
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    • v.8 no.1
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    • pp.65-70
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    • 2006
  • Transient heat transfer caused by an impulsive heating in subcooled liquid nitrogen is investigated experimentally. This study is part of out ongoing efforts directed to a stable cryogenic cooling system lot superconducting fault current limiters (SFCL). A thin heater attached by epoxy on one surface of a GFRP plate is immersed in liquid-nitrogen bath at temperatures between 77 K and 55 K. A strong heat flux up to $150W/cm^2$ is generated lot 100 ms, and the temperature of the heater sulfate is measured as a function of time. The behavior of bubbles on the heating surface can be explained by comparing the measured temperature history for vertical and two horizontal (up and down) orientations. It is concluded that the subcooling of liquid nitrogen below 70 K is very effective in suppressing bubbles, resulting in better thermal protection and faster recovery from an impulsive heat.

Vacuum Test of Cavity with Liquid Nitrogen

  • Choi, Suk;Park, Gunn-Tae;Kim, Heetae
    • Applied Science and Convergence Technology
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    • v.24 no.5
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    • pp.132-135
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    • 2015
  • Schematic of RAON vacuum system is introduced. Vacuum test for superconducting cavity with liquid nitrogen is performed. Schematic plan for RAON vacuum system is introduced and vacuum control system for superconducting cavity test is constructed. Vacuum pressure of cavity is shown as a function of pumping time. The temperature of cavity is shown as a function of cooling time. Outgassing species from cavity is also detected. Detailed experimental procedure is presented to test the cavity vacuum with liquid nitrogen.

Design of Termination Cryostat for HTS Power Cable (고온초전도 케이블 단말용 cryostat 설계)

  • 양형석;김승현;김동락;조승연;김도형;류희석;성기철
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2003.02a
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    • pp.160-162
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    • 2003
  • Termination cryostat for 22.9kV, 1.26kA-class HTS power cable has been designed. The cryostat consists of vacuum vessel, liquid nitrogen vessel, current lead and HTS power cable. The current lead and the HTS power cable are connected in liquid nitrogen vessel cooled by forced-circulation subcooled liquid nitrogen. The maximum total heat load of this cryostat is expected to be 150w. In this paper, the detailed design of the termination cryostat is mentioned.

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Fabrication of Level Meter for Liquid Nitrogen (액체 질소 액면계의 제작)

  • 김상보;김근홍;김종윤;이정민;김동락
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 1999.02a
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    • pp.182-184
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    • 1999
  • Very simple continuous level meter with capacitive transducer for cryogenic liquid is fabricated and tested with liquid nitrogen. The principle of the level meter operation is presented.

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Studies on Simplified Procedures for Freezing and Thawing of Bovine Embryos VII. Effects of freezing procedures in a liquid nitrogen container on the survival rate of mouse embryos (육우수정란 간역동결 및 융해방법에 관한 연구 제칠보. 내동제에 Sucrose 첨가에 따른 액체질소에 미치는 영향)

  • 김중규;강만종;김영훈;장덕지;강민수;김승호
    • Korean Journal of Animal Reproduction
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    • v.12 no.2
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    • pp.84-90
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    • 1988
  • This study was done with mouse embryos to determine effects of the freezing media with or without 10% sucrose, and seeding methods (pincette, no seeding, liquid nitrogen gas phase and copper wire coiled straw) on embryo survival were determined using the FDA test. The summarized results are the following. 1. The FDA score found with copper wire coiled straw, no seeding, pincette and liquid nitrogen gas phase was 3.6, 3.6, 3.3 and 3.0, respectively. There were no significant differences. 2. The embryo score shows higher (P<0.05) survival rate using a freezing medium with sucrose than the one without it. Among the seeding procedure, better resutls are copper wire coiled straw and no seeded. 3. The results suggest that copper wire coiled seeding no seeding be as good as seeding when the mouse embryos were frozen in a liquid nitrogen container using both the freezing and dilution media containing 10% sucrose.

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Breakdown Characteristics of Liquid Nitrogen in the Environment to Restrain Vapor Bubbles (비등 기포를 억제한 환경에서 액체 질소의 절연파괴 특성)

  • 백승명;정종만;김영석;곽동순;한철수;김상현
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2003.02a
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    • pp.228-231
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    • 2003
  • Experimental investigations of AC breakdown characteristics of liquid nitrogen in the environment to restrain boil bubbles are presented in this paper. The environment to restrain vapor bubble in the liquid nitrogen is both increasing pressure and decreasing temperature. Measurements of the breakdown voltage of liquid nitrogen in the environment to restrain vapor bubbles are investigated under AC high voltage in a quasi-uniform and non-uniform electrical field for pressures and temperatures ranging from 0 to 0.5 MPa and 77 K to 65 K respectively.

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