고온초전도 케이블의 절연파괴 특성에 미치는 Butt gap의 영향

곽동순,김영석,김해종,조전욱,김상현 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.3

For an electrical insulation design of HTS cable, it is important to understand the dielectric characteristics of insulation materials in L$N_2$ and the insulation type. Generally, the electrical insulation of HTS Cable is classified into two types of the composite insulation and solid insulation type. In this research, we selected the insulation paper/L$N_2$ composite insulation type for the electric insulation of a HTS cable, and studied electric insulation characteristics of synthetic Laminated Polypropylene Paper(LPP) in liquid nitrogen(L$N_2$) for the application to high temperature superconducting(HTS) cable. Furthermore, we compared the breakdown characteristics of the butt gap and bended mini-model cable. It is necessary to understand the winding parameter of insulation paper/LN2 composite insulation.

고온초전도 케이블용 의 단열조건에 cryostat 대한 열침입량 측정

김도형(Do-Hyeong Kim),정원묵(Won-moog Jung),김동락(Dong-Lak Kim),양형석(HyungSuk Yang),조승연(Seungyon Cho),황시돌(Si-Dole Hwang) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

Insulating a heat from the environment is the most important in cryogenic applications like HTS cable system. Vacuum and MLI(Multi-Layer Insulation) have been widely used to get highly efficient cryogenic insulation. In this study, experiment on annular cylinder regarded as basic model of HTS cable cryostat has been performed to measure the heat loads. To investigate the effectiveness of radiation shields in cryogenic insulation system, the experiments are carried out to various number of the shields. The measured values are compared with the results estimated theoretically. The heat loads invaded from the environment was determined by liquid nitrogen boil-off calorimetry.

한국형발사체 극저온열차단계 개발

최상호(Sangho Choi),김종민(Jongmin Kim),이준호(Joon Ho Lee) 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.5

한국형발사체 및 시험발사체에 적용되는 극저온열차단계의 개발 과정에 대하여 기술하였다. 극저온 열차단계는 액체산소로 충전된 산화제 탱크로 인한 극저온 열환경으로부터 발사체 구성품을 보호하고, 내부 공간에 서리 및 이슬 생성을 방지하기 위해 사용된다. 극저온열차단계는 설계 요구 조건, 단열재성능, 화재안전 가연성 시험 통과 여부 등을 종합적으로 고려하여 선정된다. 선정된 극저온 단열재는 시편을 이용하여 내구성 시험 및 극저온/가진 시험 등의 환경시험을 거쳐 적합성 여부를 검증한다. 이후 제작된 극저온열차단계 시제품은 발사체 총조립 과정을 통해 발사체에 장착되고, 추진기관시험설비에서 실물 기체를 이용한 수류 시험을 통해 최종 확인 단계를 거친다. The development process of cryogenic thermal protection system for the Korea Space launch vehicle-II and Test Launch Vehicle is described. The cryogenic thermal protection system is used to protect components from cryogenic thermal environments due to oxidant tanks filled with liquid oxygen and to prevent frost and dew formation in the interior space. The cryogenic thermal protection system is selected considering the design requirements, insulation performance, and whether the fire safety flammability test has passed. The selected cryogenic insulation materials are tested for their suitability through environmental tests such as durability tests and cryogenic/vibration tests using specimens. Then, the cryogenic thermal protection system is installed on the launch vehicle and verified through the filling and draining test of LOX in PSTC facility.

A Study of Cryogenic-Temperature Structural Behavior for KC-1 Corner Insulation System

Kyo Kook Jin(진교국),Byung Taek oh(오병택),Ihn Soo Yoon(윤인수),Young Chul Yang(양영철) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.4-3

고온초전도 시스템 냉각용 고화질소의 기초 절연 특성

崔在亨(Jae-Hyeong Choi),崔眞郁(Jin-Wook Choi),李海根(Haigun Lee),宋廷彬(Jung-Bin Song),金海鍾(Hae-Jong Kim),成耆哲(Ki-Chul Seong),金相賢(Sang-Hyun Kim) 대한전기학회 2009 전기학회논문지 Vol.58 No.1

Recently, for improvement of the magnetic field of high temperature superconductor (HTS) apparatus, many studies investigating on operating in the range of 20 - 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.

Type C 연료탱크에 적용되는 분말형 단열 소재의 상온/극저온 기계적 특성에 관한 연구

김태욱 ( Tae-wook Kim ),오재원 ( Jae-won Oh ),서영균 ( Young-kyun Seo ),한성종 ( Seong-jong Han ),이제명 ( Jae-myung Lee ) 한국산업융합학회 2021 한국산업융합학회 논문집 Vol.24 No.6

The global demand for Liquefied Natural Gas(LNG) continues to increase and is facing a big cycle. To keep pace with the increase in international demand for LNG, the demand for LNG fueled ships is also increasing. Since LNG fuel tanks are operated in a cryogenic environment, insulation technology is very important, and although there are various types of insulation applied to Type C tanks, multi-layer insulation and vacuum insulation are typically applied. Powder insulation materials are widely used for storage and transportation of cryogenic liquids in tanks with such a complex insulation structure. In this study, compression tests at room and cryogenic temperature were performed on closed perlite, glass bubble, and fumed silica, which are representative powder insulation material candidates. Finally, the applicability to the Type C fuel tank was reviewed by analyzing the experimental results of this study.

Evaluation of mechanical and thermal properties of insulation materials for HTS power devices at liquid nitrogen temperature

Shin, Hyung-Seop,Diaz, Mark Angelo The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.2

In superconducting power devices including power cables in which high temperature superconducting (HTS) tapes are utilized, a reliable electrical insulation should be achieved for its maximum performance. For an efficient design of HTS superconducting devices, a comparative evaluation of the mechanical and thermal propperties for various insulation materials at cryogenic temperatures is required. Especially, in the process of the property evaluation of the sheet-shaped insulation materials, anisotropy according to the machining direction should be considered because the mechanical and thermal properties are significantly influenced by the sample orientation. In this study, the cryogenic thermal and mechanical properties of various insulation material sheets such as PPLP, Cryoflex, Teflon, and Kapton were determined considering sample orientation. All samples tested at cryogenic temperature showed significantly higher tensile strength as compared with that of room temperature. The ultimate tensile strength at both temperature conditions significantly depended upon the sample orientation. The thermal properties of the insulation materials exhibited a slight difference among samples depending on the orientation: for the PPLP and Cryoflex, the CD orientation showed larger thermal contraction up to 77 K as compared to the MD one. MD samples in PPLP and Cryoflex showed a lower CTE and thermal contraction which made it more promising as an insulation material due to its comparable CTE with HTS CC tapes.

진공 단열 배관의 진공도 변화에 따른 열전달 특성 평가

김명진(Myeong-Jin Kim),한승호(Seung-Ho Han) 한국기계가공학회 2023 한국기계가공학회지 Vol.22 No.2

In cryogenic piping transportation systems, cryogenic liquids evaporate and produce vapor due to differences in internal and external temperatures, which is typically referred to as boil-off gas. This causes an increase in pressure inside the systems; consequently, the vaporized cryogenic liquids reduce the amount of transportation and can damage the pipelines. To decrease the amount of vaporized cryogenic liquids, a vacuum insulated pipe with an inner line and an outer jacket has been used widely. The inner line transports the cryogenic liquid, whereas the vacuum space between the inner and outer pipes provides insulation to minimize heat transfer and boil-off gas. The vacuum pressure in the vacuum space is referred to as the degree of vacuum, which affects the heat transfer characteristics significantly. Furthermore, selecting an appropriate degree of vacuum at the early stage of design for the vacuum insulated pipe is difficult. In this study, a heat transfer analysis is performed for a cryogenic vacuum insulated pipe comprising inner and outer pipes, vacuum space, and multilayer insulation thin films. The working fluid used is liquid nitrogen, and heat fluxes in the vacuum insulated pipe are evaluated based on the change in the degree of vacuum, such as 1, 10<SUP>-1</SUP>, 10<SUP>-2</SUP>, 10<SUP>-3</SUP>, and 10<SUP>-4</SUP> Experiments are performed using a prototype of the vacuum insulated pipe, and the obtained results are compared with the results of the heat transfer analysis. In addition, the availability of the vacuum insulated pipe for liquid hydrogen transportation is reviewed.

대용량 액체 수소 저장탱크를 위한 다층단열재의 단열성능 분석

김경호,신동환,김용찬,강상우 한국수소및신에너지학회 2016 한국수소 및 신에너지학회논문집 Vol.27 No.6

One of the most feasible solution for reducing the excessive energy consumption and carbon dioxideemission is usage of more efficient fuel such as hydrogen. As is well known, there are three viable technologiesfor storing hydrogen fuel: compressed gas, metal hydride absorption, and cryogenic liquid. In these technologies,the storage for liquid hydrogen has better energy density by weight than other storage methods. However, thecryogenic liquid storage has a significant disadvantage of boiling losses. That is, high performance of thermalinsulation systems must be studied for reducing the boiling losses. This paper presents an experimental study onthe effective thermal conductivities of the composite layered insulation with aerogel blankets(Cryogel®Z andPyrogel®XT-E) and Multi-layer insulation(MLI). The aerogel blankets are known as high porous materials andthe good insulators within a soft vacuum range(10-3~ 1 Torr). Also, MLI is known as the best insulator withina high vacuum range(<10-6~ 10-3Torr). A vertical axial cryogenic experimental apparatus was designed to investigatethe thermal performance of the composite layered insulators under cryogenic conditions as well as consist of acold mass tank, a heat absorber, annular vacuum space, and an insulators space. The composite insulators werelaminated in the insulator space that height was 50 mm. In this study, the effective thermal conductivities of thematerials were evaluated by measuring boil-off rate of liquid nitrogen and liquid argon in the cold mass tank.

BMS 단열재 및 복합재 샌드위치 극저온 강도 시험

남기원,공철원,장영순,이영무 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11

발사체에서는 액체연료(LOX) 탱크 등에 연결된 구조체에 단열재를 적용 시 극저온 환경에서 단열재의 강도 특성이 요구될 수 있다. 특히 공력가열-극저온의 반복 환경에서 팽창 수축 사이클을 견딜 정도의 충분한 탄성강도가 충족되지 않으면 박리(delamination)의 위험도가 증가하게 된다. 또한 경량화가 필요한 동체 등에는 기존의 금속재를 대체하여 복합재 샌드위치 사용이 검토되어야 한다. 본 논문에서는KSLV-Ⅰ PLF 콘부 단열재로 사용되었던 BMS 10-102 소재의 상온 및 극저온 전단강도 시험결과를 정리하였다. 또한 KSLV-Ⅰ PLF 스킨소재로 사용되었던 carbon/epoxy 면재와 알루미늄 코아로 구성된 복합재 샌드위치구조에 대하여 Flat-wise 상온 인장 시험 결과와, 상온 및 극저온 압축 시험결과를 정리하였다. Mechanical strength properties of the insulation material are required in cryogenic temperature. Especially, enough elastic properties are needed to reduce the risk of delamination for launch vehicle. And composite sandwich structure should be considered as the substitution of metallic structures to lighten the main structure of the vehicle. In the same way as insulation material, structures connected with liquid fuel tanks could be asked the high mechanical strength properties in the cryogenic temperature. Therefore this study focuses on the cryogenic tension strength of the BMS 10-102 insulation material and tension and compression strength of the flat-wise sandwich specimen in the cryogenic temperature.