• Title/Summary/Keyword: Liquid Nitrogen

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Experimental Investigation of the Subcooled Liquid Nitrogen for Resistive Superconducting Fault Current Limiter (저항형 한류기 운전조건에서의 과냉각 액체질소 특성 실험)

  • 조승연;김동락;양형석;정원묵;김도형;김혜림;현옥배
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2003.10a
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    • pp.332-334
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    • 2003
  • A subcooled liquid nitrogen cryostat is required for the cooling of a 6.6 ㎸, 200 A resistive type superconductive fault current limiter (SFCL). To help understand and design an appropriate cryostat for SFCL a prototype cryostat was fabricated and tested. Several states of subcooled liquid nitrogen were obtained by using cryocooler and helium gas. The temperature was uniformly distributed inside the liquid nitrogen vessel within the range of 0.4 K proving the effectiveness of the conduction cylinder.

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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 $E_{MAX.50%}$

Pressure-volume-temperature gauging method experiment using liquid nitrogen under microgravity condition of parabolic flight

  • Seo, Mansu;Park, Hana;Yoo, DonGyu;Jung, Youngsuk;Jeong, Sangkwon
    • Progress in Superconductivity and Cryogenics
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    • v.16 no.2
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    • pp.64-69
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    • 2014
  • Measuring an exact amount of remaining cryogenic liquid propellant under microgravity condition is one of the important issues of rocket vehicle. A Pressure-Volume-Temperature (PVT) gauging method is attractive due to its minimal additional hardware and simple gauging process. In this paper, PVT gauging method using liquid nitrogen is investigated under microgravity condition with parabolic flight. A 9.2 litre metal cryogenic liquid storage tank containing approximately 30% of liquid nitrogen is pressurized by ambient temperature helium gas. During microgravity condition, the inside of the liquid tank becomes near-isothermal condition within 1 K difference indicated by 6 silicon diode sensors vertically distributed in the middle of the liquid tank. Helium injection with higher mass flow rate after 10 seconds of the waiting time results in successful measurements of helium partial pressure in the tank. Average liquid volume measurement error is within 11% of the whole liquid tank volume and standard deviation of errors is 11.9. As a result, the applicability of PVT gauging method to liquid propellant stored in space is proven with good measurement accuracy.

Effect of Topdressing Methods of Nitrogen Fertilizer on Growth, Yield and Storage of Onion(Allium cepa L.) in Mulch-Cropping System (양파(Allium cepa L,) 멀칭재배시 질소비료 추비방법이 생육, 수량 및 저장성에 미치는 영향)

  • 김우일;서전규
    • Food Science and Preservation
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    • v.5 no.2
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    • pp.127-132
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    • 1998
  • In order to fad out an efficient way of topdressing nitrogen fertilizer in mulch-cropping system of onion(Allium cepa L.), solid, slow-release, and liquid forms of nitrogen fertilizers were allied to cv. 'Changnyungdaego' various number of times at different time, with 5 topdress applications of solid fertilizer serving as a control. Whole basal application of conventional solid fertilizer and 2 slow-release fertilizers were labor-saving and showed improved storage quality of bulbs, but resulted in poor plant growth and considerably low yield due to fertilizer shortage from early April. This suggests that topdress application is necessary. Liquid form of nitrogen fertilizer was more effective for plant growth and yield and saving labor than the solid form. Early applications was effective for increasing yield and storage quality of onion bulbs harvested. Thus two applications of liquid form of nitrogen fertilizer in February and March at rome month interval are recommended in mulch crowing system of onion.

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Removal of Inorganic Nitrogen and Phosphorus from Cow s Liquid Manure by Batch Algal Culture

  • KIM, MAM-SOO;MOO-YOUNG PACK
    • Journal of Microbiology and Biotechnology
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    • v.3 no.3
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    • pp.214-216
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    • 1993
  • Cow's liquid manure (CLM), an animal waste, was treated by a batch algal culture to remove inorganic nutrients. CLM used in this study was especially high in concentrations of inorganic nitrogen and phosphorus. The optimum dilution ratio of the CLM for maximum algal growth was 1:25. Ninety five percent of inorganic nitrogen and 100% of inorganic phosphorus were removed from the CLM with a dilution ratio of 1:25.

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Dielectric Characteristics of Subcooled $LN_2$ for Insulation Design of HTS Fault Current Limiters (고온초전도 한류기의 절연설계를 위한 과냉각 액체질소의 절연내력 특성)

  • 백승명;정종만;김상현
    • Progress in Superconductivity and Cryogenics
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    • v.5 no.2
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    • pp.46-50
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    • 2003
  • In the dielectric insulation design of any high temperature superconducting (HTS) apparatus as well as HTS fault current limiter in the electrical power systems, the breakdown characteristics of cryogenic coolants such as liquid nitrogen ($LN_2$) are an important factor of the insulating engineering. Previous reports concerned with the breakdown characteristics of liquid nitrogen have pointed out that bubbles and gaseous nitrogen have a treat influence on their breakdown phenomena, However, useful data for practical insulation design of HTS fault CUITent limiter operating at subcooled L$N_2$ have not been obtained enough. Therefore, this paper presents an experimental investigate of breakdown phenomena in liquid nitrogen under AC voltage, And, we observed the breakdown voltage (BDV) of liquid nitrogen with lowering temperature. The Weibull plots of the breakdown voltage of subcooled $LN_2$ for the needle-plane electrode with d= 10 mm are studied, The dependence of breakdown voltage for needle-plane and pancake coil-pancake coil electrode on temperature is illustrated, The relationship between the AC breakdown characteristics and the temperature were clarified.

Experiments of Continuous Release of Liquid Nitrogen (액체질소의 연속 누출 실험)

  • YONG-SHIK HAN;MYUNGBAE KIM;LE-DUY NGUYEN;MINCHANG KIM;CHANGHYUN KIM;TAE-HOON KIM;KYU HYUNG DO;BYUNG-IL CHOI
    • Transactions of the Korean hydrogen and new energy society
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    • v.34 no.5
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    • pp.526-534
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    • 2023
  • To evaluate the risk of leakage when using liquid hydrogen, a leakage test was conducted using liquid nitrogen in an outdoor environment rather than a laboratory environment. To assume a real-scale continuous leak, liquid nitrogen was allowed to leak for 5 minutes through a pipe with a diameter of 25.4 mm at a design spill rate of 60 L/min. The measurement system consisted of devices for climate conditions, LN2 spread and vapor clouds. The main experimental results are the liquid pool radius and the concentration of vapor cloud, and the radius of the liquid pool was compared with the numerical analysis results.

Pilot-scale Study on Nitrogen Removal of Effluent from Biogas Plant (바이오가스 플랜트 처리수의 고농도 질소 제거)

  • Yoo, Sungin;Yu, Youngseob;Lee, Yongsei;Park, Hyunsu;Yoo, Heechan
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.11a
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    • pp.175.1-175.1
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    • 2011
  • A rotating activated bacillus contactor (RABC) process with a series of aerobic reactors was tested in pilot scale to treat digested liquid from an anaerobic digester treating swine wastewater and sewage sludge. The influent (digested liquid) for the RABC process showed C/N ratios less than 2 as a typical feature of effluent from anaerobic digesters. The pilot process, which consists of three 3 RABC reactors, four aerobic tanks and a sedimentation tank, was operated for 210 days with a hydraulic retention time of 20 days without pH and temperature control. Since the Bacillus-enriched aerobic reactors shows high efficiencies of nitrogen removal at low DO levels less than 1.0 mg/L, they were operated at reduced aeration intensities. With relatively low concentrations of organics in comparison with nitrogen concentrations, the RABC process tested in this study showed stable and high nitrogen and organics removal efficiencies over 80%. The nitrogen removal process tested in this study was proven to be an effective and operation-cost saving (lower aeration) method to remove nitrogen without adding external carbon sources to meet the optimum C/N ratio.

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Assessing the Impact of Liquid Potassium Permanganate on Litter Quality of Poultry (액상 과망간산칼륨 적용시 육계 깔짚의 특성 평가)

  • Choi, In-Hag
    • Journal of Environmental Science International
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    • v.29 no.1
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    • pp.119-122
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    • 2020
  • The effects of liquid potassium permanganate (KMnO4) on the litter quality of poultry were investigated. Two-hundred-forty 0-day-old broiler chickens (Arbor Acres) were randomly assigned to two treatments with four replicated pens of 30 chickens each. Treatment liquid KMnO4 at a rate of 50 g of liquid KMnO4/kg of poultry litter was sprayed onto the litter surface using a small hand pump; others served as a control that was applied without liquid KMnO4 additions. Compared with controls, the treatment liquid KMnO4 showed no differences in pH, total nitrogen and ammonia concentration. It was concluded that liquid KMnO4 did not significantly increase poultry litter quality. Mechanisms relating to increasing litter pH and ammonia using liquid KMnO4 are an oxidant agent (not acid-foaming agents).

Hydraulic Performance Test of a Turbopump Inducer in Liquid Nitrogen (액체질소를 이용한 터보펌프 인듀서의 수력성능시험)

  • Kim, Jin-Sun;Hong, Soon-Sam;Kim, Jin-Han
    • 유체기계공업학회:학술대회논문집
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    • 2005.12a
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    • pp.348-353
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    • 2005
  • A cryogenic test facility has been developed to perform inducer and pump tests using liquid nitrogen. Performance tests of a turbopump in the maximum 50ton-thrust class can be performed with cryogenic fluid in the facility which operates at a temperature around $-196^{\circ}C$ with the rotational speed up to 30,000rpm. To verify the reliability of the cryogenic pump test facility, hydraulic performance tests of an inducer were accomplished, and their results were compared with the result from a water test The results confirm the reliability of the cryogenic test facility, and it is expected to contribute for on-going development of a turbopump for liquid rocket engines.

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