• 기계와재료
• /
• v.24 no.1
• /
• pp.26-35
• /
• 2012

가스액화플랜트는 질소, 산소, 헬륨 등 고순도의 가스를 효율적으로 저장 및 운송을 위해 가스를 액체로 변환하는 플랜트로, 대표적인 플랜트로는 질소, 산소, 아르곤 등의 가스를 생산하는 공기분리플랜트, 헬륨액화플랜트, 수소액화플랜트, 천연가스액화플랜트 등이 있다. 질소, 산소, 수소 등의 가스는 산업의 전반적인 분야에서 널리 사용되고 있으며, 국내의 경우 철강, 반도체, 디스플레이제조산업 등 가스 다소비 분야의 비약적인 발전에 따라 급격하게 수요가 증가하고 있는 상황이다. 대용량의 가스액화플랜트는 원료로부터 불순물을 제거하고, 팽창 또는 열교환 과정을 통해 가스를 액체로 변환하는 극저온기술로 주로 구성되며, 이와 같은 과정은 압축기, 열교환기, 증류탑, 팽창터빈, 콜드박스 등의 구성요소에 의해 구현된다. 따라서 가스액화플랜트에서 효율적인 극저온의 생성 및 유지는 플랜트의 경제성 제고를 위해 핵심적인 요소이다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.10
• /
• pp.1455-1462
• /
• 2010

PHE (Process Heat Exchanger) is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR (Very High Temperature Reactor) to the chemical reaction that yields a large quantity of hydrogen. Korea Atomic Energy Research Institute established the helium gas loop for the performance test of components, which are used in the VHTR, and they manufactured a PHE prototype to be tested in the loop. In this study, as part of the hightemperature structural-integrity evaluation of the PHE prototype, which is scheduled to be tested in the helium gas loop, we carried out high-temperature structural-analysis modeling, thermal analysis, and thermal expansion analysis of the PHE prototype. The results obtained in this study will be used to design the performance test setup for the PHE prototype.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.361-361
• /
• 2011

하나로 냉중성자원(CNS: Cold Neutron Source)은 원자로 수조내 반사체 탱크에 위치한 수직 조사공에 설치되어 하나로 노심에서 발생하는 열중성자를 감속재인 액체 수소층을 통과시켜 냉중성자를 생산한다. 생성된 냉중성자는 유도관을 통하여 냉중성자 산란장치에 공급되어 이용 연구에 활용된다. 감속재로 사용되는 수소는 헬륨냉동계통의 운전에 따라 수소가 수조내기기 집합체(IPA: In Pool Assembly) 내로 이동되어 액화되어지므로, 극저온의 헬륨가스의 흐름이 중요하다. 헬륨냉동기에 의해 만들어진 극저온인 헬륨은 IPA 내의 수소와 열교환을 하기 위해서 배관을 통해 이동되며, 열손실없이 전달하기 위하여 헬륨 배관은 진공층이 형성된 이중배관으로 설계되어 있다. 헬륨 이중배관은 공급 및 회수 배관으로 구성되어 있으며, 헬륨 배관의 외관에 진공층을 20개의 구간으로 나누어 제작 및 설치되었으며, 각각의 진공도를 유지하고 있다. 이 논문에서는 하나로 냉중성자원 헬륨 이중배관의 특성과 헬륨냉동계통의 운전 및 정지시 온도 변화에 따른 이중배관 진공도의 변화를 분석하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2003.10a
• /
• pp.141-144
• /
• 2003

In this paper, to satisfy the temperature requirement of turbopump-inlet condition, the cooling of cryogenic propellant is performed at the simulated suction-line of the Launch Vehicle. The cooling method is by using Gas helium injection. This study investigates the effect of helium injection on the liquid nitrogen which simulates the liquid oxygen. By using helium injection, the subcooling of liquid nitrogen can be achieved within four minute when the ratio of gas volume flowrate to the volume of L$N_2$ is approximately v/v$_{L}$≒0.8min$^{-1}$ . .

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.3
• /
• pp.157-164
• /
• 2016

In this study, researchers performed preliminary design and numerical analysis for a pilot-scale helium heating system intended to support full-scale construction for a sulfur-iodine (SI) cycle. The helium heat exchanger used a liquefied petroleum gas (LPG) combustor. Exhaust gas velocity at the heat exchanger outlet was approximately 40 m/s based on computational thermal and flow analysis. The maximum gas temperature was reached with six baffles in the design; lower gas temperatures were observed with four baffles. The amount of heat transfer was also higher with six baffles. Installation of additional baffles may reduce fuel costs because of the reduced LPG exhausted to the heat exchanger. However, additional baffles may also increase the pressure difference between the exchanger's inlet and outlet. Therefore, it is important to find the optimum number of baffles. Structural analysis, followed by thermal and flow analysis, indicated a 3.86 mm thermal expansion at the middle of the shell and tube type heat exchanger when both ends were supported. Structural analysis conditions included a helium flow rate of 3.729 mol/s and a helium outlet temperature of $910^{\circ}C$. An exhaust gas temperature of $1300^{\circ}C$ and an exhaust gas rate of 52 g/s were confirmed to achieve the helium outlet temperature of $910^{\circ}C$ with an exchanger inlet temperature of $135^{\circ}C$ in an LPG-fueled helium heating system.

• Analytical Science and Technology
• /
• v.26 no.4
• /
• pp.235-244
• /
• 2013

Detection of halogens using laser-induced breakdown spectroscopy (LIBS) in open air is very difficult since their strong atomic emission lines are located in VUV region. In NIR region, there are other emission lines of halogens through electronic transitions between excited states. However, these lines undergo Stark broadening severely. We report the observation of the emission lines of halogens in laser-induced plasma (LIP) spectra in NIR region using a helium gas flow. Particularly, the emission lines of iodine at 804.374 and 905.833 nm from LIPs have been observed for the first time. In the helium ambient gas, Stark broadening of the emission lines and background continuum emission could be suppressed significantly. Variations of the line intensity, plasma temperature, and electron density with the helium flow rate was investigated. Detection of chlorine and bromine in flame retardant of rubbers was demonstrated using this method. Finally, we suggest a pulsed helium gas jet as a practical and ecomonical helium gas source for the LIBS analysis of halogens in open air.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.293-297
• /
• 2009

Valves, which are used to supply or block the flow of cryogenic pressurant in the pressurization system of liquid-propellant propulsion system in a launch vehicle, are pneumo-actuated valve, solenoid valve, pyro-valve, etc. Both pneumo-actuated valve and solenoid valve have more complex structure and are heavier than pyro-valve. For this study, a couple of pyro-valves, which are applicable to cryogenic and high-pressure fluid (cryogenic gaseous helium), have a simple structure, and are comparably light, are designed, manufactured, and tested (proof-pressure/leakage tests, performance test, vibration test, helium supply tests).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.2
• /
• pp.213-218
• /
• 2010

A cooling system utilizing liquid helium to chill the cryopanel (800 mm $\times$ 700 mm dimensions) down to 4.2 K was designed, implemented, and tested to verify the role of the cryopanel as a heat sink for the payload of a spacecraft inside the large thermal vacuum chamber (effective dimensions : 8 m ($\Phi$) $\times$ 10 m (L)) of KARI (Korea Aerospace Research Institute). Two LHe (Liquid Helium) Dewars, one for the main supply and the other for refilling, were used to supply liquid helium or cold helium gas into this cryopanel, and flow control for the target temperature of the cryopanel within requirements was done through fine adjustment of the pressure inside the LHe Dewars. The return helium gas from the cryopanel was reused as a thermal barrier to minimize the heat influx on the core liquid helium supply pipe. The test verified a cooling time of around three hours from the ambient temperature to 40 K (combined standard uncertainty of 194 mK), the capacity for maintaining the cryopanel at intermediate temperatures, and a 1 K uniformity over the entire cryopanel surface at around 40 K with 20 W cooling power.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.2
• /
• pp.146.1-146.1
• /
• 2011

최근의 관측에 의하면 우리 은하의 헤일로내 field에 위치한 subdwarf B 항성이 헬륨이 증가된 구상성단의 푸른 수평계열성 ( Extreme Blue Horizontal Branch ) 과 동일한 기원을 가질 것으로 예측된다. 초기 우주 환경과 비슷한 헬륨 함량을 보이는 환경에서는 Building Block 내부 이외에는 헬륨이 충분히 증가된 가스를 공급할 수 없기 때문에 이러한 기원을 가지는 sdB 항성의 개수를 예측함으로써 우리 은하의 초기 Building Block으로 부터 얼마나 많은 수의 항성이 헤일로에 뿌려졌는지 예측할 수 있다. 우리는 우리 은하내 나이가 많은 항성들로 이루어진 헤일로와 Bulge 내에 이러한 기원을 가지는 sdB 항성의 개수를 예측한 결과, 초기 Building Block으로 부터 유입된 sdB 항성이 최소 8만 여개 이상일 것으로 추정하였다. 이 개수는 우리 은하 구상 성단 중 은하 Building Block의 잔재로 생각되는 성단에 존재하는 헬륨이 증가된 수평계열성의 총 합의 10배 이상의 규모에 해당한다. 이는 이들 성단이 은하 생성 초기에는 현재의 질량 규모보다 최소 10배 이상 무거웠을 것이라는 가정과 일치하는 결과이다.

• Journal of the Korean Vacuum Society
• /
• v.16 no.2
• /
• pp.153-159
• /
• 2007

In-cryostat helium lines are under installation to transfer a cryogenic helium into cold components in KSTAR device. In KSTAR, three kinds of helium should be supplied into the cold components, which are supercritical helium Into superconduction(SC) magnet system, liquid helium into current lead system, and gas helium into thermal shields. Cryogenic helium lines consist of transfer lines outside the cryostat, in-cryostat helium lines, and electrical breaks. In-cryostat helium lines should be guaranteed of leak tightness for tong time operation at high internal helium pressure of 20 bar. We wrapped the helium line with multi-layer insulator(MLI) to reduce radiation heat and insulated the surface of the high potential part with prepreg tape. The electrical break was fabricated by brazing ceramic tube with stainless steel tube. To ensure the operation reliability at operation temperature, all the electrical break have been examined by the thermal cycle test at liquid nitrogen and by the hydraulic test at 30 bar. And additional surface insulation was prepared with prepreg tape to give structural safety. At present most of the in-cryostat helium lines have been installed and the final inspection test is progressing.