• Title/Summary/Keyword: Liquid Nitrogen

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The Lubrication Effect of Liquid Nitrogen in Cryogenic Machining [I]- Part 1: Cutting Force Component with Physical Evidences - (Liquid Nitrogend의 감찰효과 -물리적 현상에 의한 절삭력-)

  • Jun Seong Chan;Jeong Woo Cheol
    • Journal of the Korea Safety Management & Science
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    • v.4 no.2
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    • pp.209-221
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    • 2002
  • Machinability improvement by the use of liquid nitrogen in cryogenic machining has been reported in various studies. This has been mostly attributed to the cooling effect of liquid nitrogen. However, No study has been found in discussion on whether liquid nitrogen possesses lubrication effect in cryogenic cutting. In machining tests, cryogenic machining reduced the force component in the feed direction, indicating that the chip slides on the tool rake face with lower friction. This study also found that the effectiveness of LN2 lubrication depends on the approach how LN2 is applied regarding cutting forces related.

Characteristics of Surface Flashover on Partially Immersed of Spacer in Liquid Nitrogen (액체질소 중에서 spacer의 부분적 침적에 대한 연면 방전특성)

  • 김영석;이병성;백승명;정종만;정순용;김상현
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.2
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    • pp.177-182
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    • 2000
  • Composite insulation system of liquid nitrogen and solid spacer is widely applied in high temperature superconduction power machine. This study has three step procedure. As follow, first step is composition of parallel deposited electrode and vertically deposited electrode along the direction of immersion in liquid nitrogen(LN2). Second step is investigation into surface flashover voltage of solid spacer under partially immersed in LN2, and last step is comparison the result of this research with that of fully immersed in LN2 and at cryogenic temperature gaseous nitrogen(GN2). This result presented that surface flashover voltage along solid spacer half immersed in LN2 was almost the same as that of fully immersed spacer when the thickness of spacer(t) was t<10mm. In the case of t> 10mm, however, spacer flashover voltage was equal to that obtained in GN2 at cryogenic temperature. And the immersed direction functions as role of deciding the difference of surface flashover voltage.

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Simple and Flexible Temperature Control System for Space Environment Test

  • Lee, Sang-Hoon;Cho, Hyok-Jin;Seo, Hee-Jun;Moon, Guee-Won;Choi, Seok-Weon
    • Bulletin of the Korean Space Science Society
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    • pp.29.1-29.1
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    • 2008
  • The temperature control system which is using liquid and gaseous nitrogen has been known as the most economical system to simulate space temperature condition due to relatively not expansive price of the liquid nitrogen (less than 0.2 USD per liter). And, among these systems, the closed loop system which circulates compressed nitrogen gas come from sprayed liquid nitrogen by blower and makes a target temperature with heat from an electrical heater and flow rate of liquid nitrogen is prevail all over the world. But, this complete closed loop system requires expansive equipments such as blower, heater, and liquid nitrogen injector, and special maintenance on the system. Therefore, KARI is developing efficient and simple open loop system which utilizes liquid and gaseous nitrogen with eliminating a special blower and other expansive units. In this study, this open loop system with more efficiency and flexibility will be designed and introduced.

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Cryogenic Performance Test of a Turbopump Inducer (터보펌프 인듀서에 대한 극저온 성능시험)

  • Hong Soon-Sam;Kim Jin-Sun;Kim Jin-Han
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.93-99
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    • 2006
  • A test facility was developed where an inducer for a liquid rocket engine turbopump can be tested using liquid nitrogen as a working fluid. At the facility, a hydrodynamic performance test and a cavitation performance test for an oxidizer turbopump were carried out. Head-flow relation at liquid nitrogen test was similar to the case at water test. However, cavitation performance at the liquid nitrogen was superior to the case at water test, which results from the thermodynamic effect of cavitation.

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A Study on the Dielectric Characteristics of Insulation Gases for a Sub-cooled Liquid Nitrogen System (이용률을 이용한 과냉질소 냉각시스템용 절연가스의 절연특성에 관한 연구)

  • Kang, Hyoung-Ku;Ko, Tae-Kuk
    • Progress in Superconductivity and Cryogenics
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    • v.12 no.1
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    • pp.52-55
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    • 2010
  • A sub-cooled liquid nitrogen system is known as a promising method to develop high voltage superconducting apparatuses such as superconducting fault current limiters (SFCLs) and superconducting cables. To develop a high voltage superconducting machine adopting the sub-cooled liquid nitrogen system with a constant pressure. injecting a non-condensable gas is indispensable. In this study. the dielectric characteristics of insulation gases are investigated and analyzed by using electric utilization factors ($\xi$). It is found that the maximum electric field at sparkover that occurs with 50 % probability. $E_{MAX.50%}$ exponentially decreases as the S increases. This means that the $E_{MAX.50%}$ at sparkover can be estimated with the $E_{MAX.50%}$

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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    • 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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Performance Test of Cooling System for the KEPCO HTS Power Cable (한전 초전도전력케이블 냉각시스템 성능시험)

  • Yang, H.S.;Kim, D.L.;Sohn, S.H.;Lim, J.H.;Choi, H.O.;Lee, B.S.;Choi, Y.S.;Ryoo, H.S.;Hwang, S.D.
    • Proceedings of the KSME Conference
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    • pp.2206-2210
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    • 2007
  • As a power transmission line supplying power to a densely populated city, the high temperature superconducting (HTS) cable is expected to one of the most effective cables with a compact size because of its high current density. The verification of HTS power cable system have been progressed by KEPRI. A cooling system for a 3-phase 100m HTS power cable with 22.9kV/1.25kA was installed and tested at KEPCO's Gochang power testing center in Korea. The system consists of a liquid nitrogen decompression cooling system with a cooling capacity of 3kW and a closed circulation system of subcooled liquid nitrogen. Several performance tests of the cable system with respect to the cooling such as cooling capacity, heat load and temperature stability, were performed at several temperatures. Thermal cycle test, cool-down to liquid nitrogen temperature and warm-up to room temperature, was also performed to investigate thermal cycle influences. The outline of the installed cooling system and performance test results are presented in this paper.

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Effects of Temperature and Pressure on the Breakdown Characteristics of Liquid Nitrogen

  • Baek, Seung-Myeong;Joung, Jong-Man;Kim, Sang-Hyun
    • KIEE International Transactions on Electrophysics and Applications
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    • v.3C no.5
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    • pp.171-176
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    • 2003
  • For practical electrical insulation design of high temperature superconducting (HTS) power apparatuses, knowledge of the dielectric behavior of both liquid nitrogen (L$N_2$) and subcooled liquid nitrogen (SL$N_2$) are essential. To achieve SL$N_2$ at atmospheric pressure, cryostat was designed and constructed. By pumping up the L$N_2$ in the outer dewar, the temperature of L$N_2$ in the inner dewar at atmospheric pressure can be controlled. The breakdown characteristics of L$N_2$ in quasi-uniform and non-uniform electrical fields for temperatures ranging from 77 K to 65 K at atmospheric pressure and pressure ranging from 0.1 to 0.5 MPa were investigated experimentally. The experimental data suggested that the breakdown voltage (BDV) of L$N_2$ is both highly temperature and pressure dependent. We also carried out statistical analysis of the experimental results using the Weibull distribution. The Weibull shape parameter m for the sphere-to-plane electrodes in SL$N_2$ was estimated to be 11 to 18.

Preservation of Fungi in Liquid Nitrogen Using Polypropylene Straws (폴리프로필렌 스트로를 이용한 곰팡이의 액체질소 보존)

  • Jeon, Young-Ah;Shin, Myung-Sook;Kim, Hyo-Jin;Kim, Dae-Ho;Go, Seung-Joo;Hong, Seung-Beom
    • The Korean Journal of Mycology
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    • v.34 no.1
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    • pp.54-58
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    • 2006
  • Liquid nitrogen storage is the most effective way to preserve many fungi including what cannot be lyophilized. The use of polypropylene straws instead of cryotubes has many advantages in economy, safety, convenience, and space-saving. We, Korean Agricultural Culture Collection (KACC), established the fungal preservation methods in liquid nitrogen using polypropylene drinking straws and introduced the methods in detail.

Effect of Nitrogen Injection Pressure on Lqiufied Engine Performance (질소 분사 압력이 액화질소 엔진의 성능 특성에 미치는 영향)

  • Shin, Donggil
    • Journal of Energy Engineering
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    • v.26 no.1
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    • pp.28-33
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    • 2017
  • A liquid nitrogen engine is a highly clean power engine, which does not emit any hazardous substances in its fumes. Additionally, it has an advantage over electric vehicles, as its energy density is larger than that of a battery. The use of an existing liquid nitrogen engine is typically limited to the reciprocation type. In this study, the concept of a nitrogen engine equipped with a scroll expander is introduced. The engine's efficiency was shown to increase when the scroll expander was utilized in the engine, while also adding to the simplification of the structure. Therefore, compared to the existing reciprocation-type engine, the engine with the scroll expander has the potential to be both technically and economically more competitive. In this study, the performance of a liquid nitrogen engine equipped with a scroll expander was analyzed while altering the injection pressure profile of liquid nitrogen.