• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.201-205
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• 2011

In a cryogenic propellant tank the pressurant is contracted due to heat loss and the propellant itself evaporates. On a restartable propulsion system such phenomena are more intensive because the propellant contacts with the pressurant on the larger surface during the coast flight. Such heat and mass transfer phenomena should be considered for estimating the amount of pressurant. On the hypothesis that the heat and mass transfer quasi-equilibrium is achieved during the coast flight, the calculation process of the equilibrium pressure is presented. On the process the amount of loaded helium on the Falcon-1 second stage is calculated.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.15-22
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• 2018

A compressible multiphase flow was investigated using a DIM consisting of seven equations, including the fifth-order MLP and a modified HLLC Riemann solver to achieve a precise interface structure of liquid and gas. The numerical methods were verified by comparing the flow structures of the high-pressure water and low-pressure air in the shock tube. A 2D air-helium shock-bubble interaction at the incident shock wave condition (Mach number 1.22) was numerically solved and verified using the experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.279-284
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• 2008

Propellant pressurization system in liquid rocket propulsion system plays a role in supplying pressurant gas at a controlled pressure into the ullage space of propellant tanks. The most important design parameter for such propellant pressurization system is the temperature of pressurant gas fed from pressurant tank, which is placed inside of cryogenic propellant tank. Such pressurant is gaseous state, of which density is very sensitive to the temperature of pressurant. Previous investigation dealt with thermal correlation of pressurant and external fluid at room temperature. This study investigates the temperature variation of cryogenic pressurant (GHe) at the time when the pressurant is coming out of pressurant tank, which is submerged in a liquid oxygen, experimentally as well as numerically.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.58-64
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• 2007

Propellant pressurization system in liquid rocket propulsion system plays a role supplying pressurant gas at a controlled pressure into the ullage space of propellant tanks. The most important design parameter for such propellant pressurization system is the temperature of pressurant gas fed from pressurant tank, which is placed inside of cryogenic propellant tank. Such pressurant is gaseous state, of which density is very sensitive to the temperature of pressurant. Previous investigation dealt with thermal correlation of pressurant and external fluid at room temperature. This study investigates the temperature variation of cryogenic pressurant (GHe) at the time when the pressurant is coming out of pressurant tank, which is submerged in a liquid oxygen, experimentally as well as numerically.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.54-61
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• 2007

Propellant pressurization system in liquid rocket propulsion system plays a role supplying pressurant gas at a controlled pressure into the ullage space of propellant tanks. The most important design parameter for such propellant pressurization system is the temperature of pressurant gas fed from pressurant tank. Such pressurant is gaseous state, of which density is very sensitive to the temperature of pressurant. Generally for the propulsion system, which requires high thrust and is consisted of cryogenic propellant the pressurant is stored at high density and high pressure to reduce the weight of pressurant tanks, which are placed inside of cryogenic propellant tank. That is called cryogenic storage pressurization system. This study investigates the temperature variation of pressurant at the time when the pressurant is coming out of pressurant tank experimentally as well as numerically. Fluids used in this study are air and liquid oxygen as outer fluid and gaseous nitrogen and gaseous helium as pressurant respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.802-808
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• 2011

One of the important mechanical properties of cryogenic temperature structure material is fracture toughness. Research on normalization of fracture toughness test method is becoming very important issue with development of cryogenic structural elements. Specially, mechanical properties estimation by each micro-structure of welding department is important because it can cause unstable fracture when use under cryogenic environment in case of welding department. In this study, fracture toughness estimation test was carried out to unloading compliance method and sensitization heat-tread minimized test specimen at liquid nitrogen (77K), liquid helium (4K), 293K temperature to STS-316L base metal and weld metal.

• Journal of the Korean Vacuum Society
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• v.16 no.5
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• pp.388-396
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• 2007

KSTAR (Korea Superconducting Tokamak Advanced Research) current lead system (CLS) has a role to interconnect magnet power supply (MPS) in room temperature (300 K) and superconducting (SC) bus-line, electrically. For the first plasma experiments, it should be assembled 4 current leads (CL) on toroidal field (TF) current lead box (CLB) and 14 leads on poloidal field (PF) CLB. Two current leads, with the design currents 17.5 kA, and SC bus-lines are connected in parallel to supply 35 kA DC currents on TF magnet. Whereas, it could supply $20\;{\sim}\;26\;kA$ to each pairs of PF magnets during more than 350 s. At the cold terminals of the leads, there are joined SC bus-lines and it was constructed helium coolant control system, aside from main tokamak system, to protect heat flux through current leads and enhanced Joule heat due to supplied currents. Throughout the establishment processes, it was tested the high vacuum pumping, helium leak of the helium lines and hardwares mounted between the helium lines, flow controls for CL, and liquid nitrogen cool-down of possible parts (current leads, CL helium lines, and thermal shield helium lines for CLB), for the accomplishment of the required performances.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2613-2616
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• 2003

This paper presents a realization of LonWorks communication based remote monitoring and control system for old-dated Helium Liquefier to be automated in operation and data acquisition. Through Inn nodes, tank level, valve position, gasbag level and temperatures are collected and valve position is adjusted by step motor control. Also, field data acquired can be monitored at a remote site through LAN.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1117-1118
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• 2011

NMR이나 MRI와 같은 고자장을 필요로 하는 마그넷은 높은 운전전류를 갖는 초전도 선재를 이용하여 제작된다. 이때 마그넷은 여러 코일을 겹쳐서 제작하는 것이 일반적이고, 크게 내측마그넷과 외측 마그넷으로 구분할 수 있다. 본 논문에서는 15T 외측마그넷 안에서 동작하는 5T급 내측마그넷의 설계 과정을 나타내었다. 내측마그넷은 2세대 고온초전도 선재를 이용하여 설계되고, 4.2K의 액체헬륨 안에서 동작한다. 마그넷의 임계전류는 초전도 선재의 $I_c$-B 특성을 고려하여 산정하였고, 임계전류를 바탕으로 운전전류를 결정하였다. 내측마그넷의 발생자장이 5T를 만족하는 운전전류와 마그넷의 형상을 계산을 통하여 제시하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.1
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• pp.11-19
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• 1994

An optimal design for Gifford-McMahon/Joule-Thomson(GM-JT) refrigerators was performed by a numerical method. The design goal was to meet the cooling requirement for MRI systems, which was 3 Watt at 4 K. A general cycle analysis program was written to calculate the cooling capacity of the GM-JT refrigerators for the givenstage GM refrigerator. The program was executed for a specific refrigerator with various design parameters. The optimal values for the maximum cooling were found for the sizes of the heat exchangers, the mass flow rate of helium, and the compression pressure.