• Title/Summary/Keyword: Liquid nitrogen

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The Basic Insulation Characteristics of Solid-Nitrogen for Cryocooling of HTS Systems (고온초전도 시스템 냉각용 고화질소의 기초 절연 특성)

  • Choi, Jae-Hyeong;Choi, Jin-Wook;Lee, Hai-Gun;Song, Jung-Bin;Kim, Hae-Jong;Seong, Ki-Chul;Kim, Sang-Hyun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.1
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    • pp.132-136
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    • 2009
  • Recently, for improvement of the magnetic field of high temperature superconductor (HTS) apparatus, many studies investigating on operating in the range of $20{\sim}65\;K$ with liquid helium or the conducting method using cryocooler are actively reviewed. Also, the cooling method using solid nitrogen as cryogen is being suggested. Since the nitrogen has very large specific heat in solid state, it is expected that it can be operated for a long time without a continuous supply of cooling energy. However, there are still insufficient data on the characteristics of solid nitrogen such as thermodynamic properties and liquid-solid phase change. Especially, there was almost no study done on the electrical insulation properties of solid nitrogen so far. In this study, solid nitrogen to find the electrical characteristics was made by using cryocooler and cryostat, and investigated the flashover discharge and breakdown. The results of this study will be useful as a basic data for electrical insulation design of the HTS system using solid nitrogen as cryogen.

Experimental investigation on No-Vent Fill (NVF) process using liquid Nitrogen

  • Kim, Youngcheol;Seo, Mansu;Yoo, Donggyu;Jeong, Sangkwon
    • Progress in Superconductivity and Cryogenics
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    • v.16 no.4
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    • pp.71-77
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    • 2014
  • For a long-term space mission, filling process of cryogenic liquid propellant is operated on a space vehicle in space. A vent process during transfer and filling of cryogenic propellant is needed to maintain the fuel tank pressure at a safe level due to its volatile characteristic. It is possible that both liquid and vapor phases of the cryogenic propellant are released simultaneously to outer space when the vent process occurs under low gravity environment. As a result, the existing filling process with venting not only accompanies wasting liquid propellant, but also consumes extra fuel to compensate for the unexpected momentum originated from the vent process. No-Vent Fill (NVF) method, a filling procedure without a venting process of cryogenic liquid propellant, is an attractive technology to perform a long-term space mission. In this paper, the preliminary experimental results of the NVF process are described. The experimental set-up consists of a 9-liter cryogenic liquid receiver tank and a supply tank. Liquid nitrogen ($LN_2$) is used to simulate the behavior of cryogenic propellant. The whole situation in the receiver tank during NVF is monitored. The major experimental parameter in the experiment is the mass flow rate of the liquid nitrogen. The experimental results demonstrate that as the mass flow rate is increased, NVF process is conducted successfully. The quality and the inlet temperature of the injected $LN_2$ are affected by the mass flow rate. These parameters determine success of NVF.

A Study to Draw a Plan of Liquid Fertilizer Quality Certification Standards for Livestock Manure Management (가축분뇨의 관리를 위한 액비품질인증기준 방안도출 연구)

  • Jeon, Sang-Joon;Kim, Soo-Ryang;Hong, In-Gi;Kim, Ha-Je;Kim, Dong-Gyun;Lee, Myung-Gyu
    • Journal of Animal Environmental Science
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    • v.19 no.2
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    • pp.183-190
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    • 2013
  • Establishment of a new concept of environmental friendly livestock manure management is required based on the facts. But now liquid fertilizer quality in korea shows a large difference among regions and the regulations are uncertain. Focusing on precedent study on main level-grading factors of liquid fertilizer quality certification, the study collected laws and standards related to liquid fertilizer of livestock manure at home and abroad and produced evaluation standards. Liquid fertilizer was divided into four factors (fertilizing value, harmfulness, stability and uniformity). According to each item, scores were awarded based on 16 details: fertilizing value (Nitrogen concentration, the whole concentration of Nitrogen, Phosphoric acid and Kalium), harmfulness (heavy metals, pathogenic microorganism and antibiotics), stability (maturity degree and odour), uniformity (EC, BOD, SS, moisture content and salt). The grade of liquid fertilizer, A (42~48), B (34~41), C (26~33) were rated using total scores.

Effects of die cooling on change of extrusion characteristics of Al-Mn-based thin-walled flat multi-port tube (금형 냉각이 Al-Mn계 다중압출 평판관의 압출 특성 변화에 미치는 영향)

  • Young-Chul Shin;Seong-Ho Ha;Tae-Hoon Kang;Kee-Ahn Lee;Seung-Chul Lee
    • Design & Manufacturing
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    • v.17 no.4
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    • pp.63-71
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    • 2023
  • In order to increase the extrusion production speed of aluminum, extrusion die cooling technology using liquid nitrogen has recently attracted a lot of attention. Increasing the extrusion speed increases the temperature of the bearing area of extrusion dies and the extrusion profile, which may cause defects on the surface of extruded profile. Extrusion die cooling technology is to directly inject liquid nitrogen through a cooling channel formed between the die and the backer inside the die-set. The liquid nitrogen removes heat from the die-set, and gaseous nitrogen at the exit of the channel, covers the extrusion profile of an inert atmosphere reducing the oxidation and the profile temperature. The aim of this study is to evaluate the cooling capacity by applying die cooling to extrusion of Al-Mn-based aluminum alloy flat tubes, and to investigate the effects of die cooling on the change in extrusion characteristics of flat tubes. Cooling capacity was confirmed by observing the temperature change of the extrusion profile depending on whether or not die cooling is applied. To observe changes in material characteristics due to die cooling, surface observation is conducted and microstructure and precipitate analysis are performed by FE-SEM on the surface and longitudinal cross section of the extruded flat tubes.

A Study on the Insulation Properties of Cryogen for the HTS SMES (고온 초전도 에너지 저장장치용 극저온 냉매의 절연 특성 연구)

  • Choi, Jae-Hyeong;Choi, Jin-Wook;Lee, Hai-Gun;Song, Jung-Bin;Kim, Hae-Jong;Seong, Ki-Chul;Kim, Sang-Hyun
    • Progress in Superconductivity and Cryogenics
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    • v.11 no.1
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    • pp.16-19
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    • 2009
  • Recently, for improvement of the magnetic field of high temperature superconductor (HTS) apparatus, many studies investigating on operating in the range of $20{\sim}65K$ with liquid helium or the conducting method using cryocooler is actively reviewed. Also, the cooling method using solid nitrogen as cryogen is being suggested. Since the nitrogen has very large specific heat in solid state, it is expected that it can enable long time operation without a continuous supply of cooling energy. However, there is still insufficient data on the characteristics of solid nitrogen such as thermodynamic properties and liquid-solid phase change. Especially, there was almost no study done on the electrical insulation properties of solid nitrogen so far. In this study, solid nitrogen to find the electrical characteristics was made by using cryocooler and cryostat, and investigated the flashover discharge and breakdown. The results of this study will be useful as a basic data for electrical insulation design of the HTS system using solid nitrogen as cryogen.

Characteristics of Surface Flashover of spacer in Liquid Nitrogen (액체 질소중에서 고체 Spacer에 의한 연면 방전특성)

  • Kim, Y.S.;Back, S.M.;Lee, B.S.;Jang, H.M.;Kim, S.H.
    • Proceedings of the KIEE Conference
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    • 1999.11d
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    • pp.912-914
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    • 1999
  • Composite insulation system of liquid nitrogen and solid spacer is widely applied in high temperature superconducting 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($LN_2$). Second step is investigation into surface flashover voltage of solid spacer under partially immersed in $LN_2$, and last step is comparison the result of this research with that of fully immersed in $LN_2$ and at cryogenic temperature gaseous nitrogen($GN_2$). This result presented that surface flashover voltage along solid spacer half immersed in $LN_2$ was almost the same as that of fully immersed spacer when the thickness of spacer(t) was t<10 mm. In the case of t>10 mm, however, spacer flashover voltage was equal to that obtained in $GN_2$ at cryogenic temperature.

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Nitrogen Removal from a mixed Industrial Wastewater using Food-Waste Leachate and Sugar Liquid Waste as External Carbon Sources: Full-Scale Experiment (혼합 산업폐수의 질소제거를 위한 외부 탄소원 투입과 물질수지: 실증실험)

  • Lee, Monghak;Ahn, Johwan;Lee, Junghun;Bae, Wookeun;Shim, Hojae
    • Journal of Korean Society on Water Environment
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    • v.28 no.5
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    • pp.663-668
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    • 2012
  • The feasibility of enhancing biological nutrient removal from an industrial wastewater was tested with food waste leachate and sugar liquid waste as external carbon sources. Long term influences of adding external carbon sources were investigated to see how the biological nutrient removal process worked in terms of the removal efficiency. The addition of the external carbons led to a significant improvement in the removal efficiency of nutrients: from 49% to approximately 76% for nitrogen and from 64% to around 80% for phosphorus. Approximately, 20% of the removal nitrogen was synthesized into biomass, while the remaining 80% was denitrified. Though the addition of external carbon sources improved nutrient removal, it also increased the waste sludge production substantially. The optimal observed BOD/TN ratio, based on nitrogen removal and sludge production, was around 4.0 in this study.

Comparison of Enhancement Effect of Ninhydrin Fluorescent Fingerprints Using Zinc Chloride and Liquid Nitrogen and Introducing the New Cooling Method for Post Treatment of Ninhydrin (염화아연(Zinc Chloride)과 액화질소를 사용한 닌히드린(Ninhydrin) 형광지문의 증강 효과 비교 및 실무적 사용을 위한 새로운 냉각방법에 관한 연구)

  • Jeon, Su-Yeon;Kim, Chang-Yong;Kim, Mi-So;Yu, Je-Seol
    • Journal of the Korea Convergence Society
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    • v.11 no.6
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    • pp.75-82
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    • 2020
  • We identify the enhancement effects of zinc chloride and liquid nitrogen on low quality ninhydrin-developed fingerprint and we wanted to find out another cooling methods available for ninhydrin/Zn fingerprint enhancement besides the liquid nitrogen, which is hard to access. Artificial sweat was used to make the same level of fingerprints, and fingerprints developed by each technique were evaluated by SWGFAST standard and compared the average score and standard deviation. As a result of the experiment, ninhydrin/Zn-liquid nitrogen got 3.2 and 3.3 as average scores that enough to identify an individual such as 1,2-IND/Zn or DFO. Also, experiments using dry ice instead of liquid nitrogen as a way of the ninhydrin/Zn-developed fingerprints enhancement resulted in 3.0 and 2.9 as average scores, therefore, it was confirmed that dry ice is also a sufficient cooling method to be considered in practice in the field of forensic science.

Effects of Different Infusion Frequency of Liquid Nitrogen on Human Embryo Development and Pregnancy Rates after Freezing and Thawing (인간 배아 동결 해빙시 액체질소의 분사속도가 배아 발달 및 임신에 미치는 영향)

  • Kim, Young-Ah;Seo, Seong-Seog;Kim, Mi-Ran;Hwang, Kyung-Joo;Park, Dong-Wook;Jo, Mi-Yeong;Ryu, Hee-Suk
    • Clinical and Experimental Reproductive Medicine
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    • v.28 no.4
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    • pp.287-293
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    • 2001
  • Objective : To investigate the efficacy of high infusion frequency of liquid nitrogen on pregnancy in human embryo after freezing and thawing. Materials and Methods: 150 infertile patients underwent 162 consecutive thawing-ET cycles. In the high infusion frequency group (Group A), 47 patients (50 cycles) underwent cryopreservation with high infusion frequency of liquid nitrogen. In the low infusion frequency group (Group B), 103 patients (112 cycles) underwent cryopreservation with low infusion frequency of liquid nitrogen. We analyzed the clinical characteristics, fertilization rates, development of embryo, good quality embryo ratio, implantation rates, and pregnancy rates between these two groups. Results: There was no difference between the groups with regard to clinical characteristics (mean age, infertility duration, infertility factors, hormone profile), mean number of oocyte retrieval, fertilization rates, and mean embryo number of transfers. The survival rates in group A was 64.9% (228 of 350 embryos), and among the 228 embryos 190 embryos (83.3%) which progressed to the two- to eight-cell stage. After thawing, the embryo numbers were 65 (34.2%), 29 (15.3%), 35 (18.4%), and 37 (19.5%) of grades 1, 2, 3, and above 4, respectively. The survival rates in group B was 63.8% (482 of 755 embryos), and among the 482 embryos 465 embryos (96.5%) which progressed to the two- to eight-cell stage. After thawing, the embryo numbers were 106 (22.8%), 94 (20.2%), 89 (19.1%), and 112 (24.1%) of grades 1, 2, 3, and above 4, respectively. There was no difference in embryo quality change after the freezing-thawing procedure between the groups. Implantation rates (31.1% vs. 34.3%) were not significant. However hCG positive rates in group A (40%) were higher than group B, but not statistically significant. Clinical pregnancy rate (26% vs. 25.9%), on going pregnancy rates (>20 weeks) were not significant (26% vs. 25%). Conclusion: We compared embryo quality change, survival rates, and pregnancy rates between high infusion frequency group and low infusion frequency group and the results were similar between the two groups. Therefore, high infusion frequency of liquid nitrogen for cryopreservation is a worthy method to preserve in human embryos.

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Study on the Breakdown Performance of Synthetic Polypropylene Laminated Paper for Application of a HTS Cable (고온초전도 케이블의 응용을 위한 PPLP의 절연파괴 특성연구)

  • Kwag, Dong-Soon;Kim, Young-Seok;Kim, Hae-Jong;Kim, Sang-Hyun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05e
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    • pp.65-68
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    • 2003
  • In this paper, we researched breakdown characteristics of paper/liquid nitrogen composite insulation system for application of a high temperature superconducting cable. And, we have studied the AC breakdown performance of paper/ice composite insulating system immersed in liquid nitrogen. The electric strength in this paper/ice composite system is higher than that of paper/liquid nitrogen system. Furthermore this system shows a self-healing type breakdown behavior. Among the many kinds of liquid to be immersed and frozen to the ice, deionized water gives the highest electric breakdown strength. The paper/ice composite insulation system is thought to be one of good candidate for the electrical insulating system at cryogenic temperature.

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