• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.343-351
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• 1998

This paper was investigated degradation of the fracture toughness caused by sensitizing heat-treatment of the cryogenic structural material JN1 base metal using unloading compliance method reported as useful a method in evaluating the elastic-plastic fracture toughness at cryogenic temperature. The specimens used in this paper were 20% side-grooved 0.5T-CT specimens which were machined in the JN1 base metal. Also, to investigate cryogenic fracture toughness of the fusion line region in the JN1 GTA weldments, it was also used 20% side-grooved 0.5T-CT specimens that was machined fusion line to located in the middle of the specimen. The cryogenic fracture toughness values of the JN1 base metal were significantly decreased with increasing the time and temperature of the heat treatment. The fracture toughness value obtained from the fusion line specimen was invalid, but it was lower value than that of the JN1 base metal. Especially, this value was approximately equal with that obtained from the JN1 650.deg. C-5h heat-treated material.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.116-122
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• 2010

It is necessary to be careful about contamination control to minimize the accumulation of the contamination material on satellite surface during the I&T phase. In the space environment which characterized by high vacuum, high and very low temperature, contamination material causes satellite to lose its own performance. Especially, contamination material can accumulate on critical surfaces such as lenses, mirrors, and sensors. KARI(Korea Aerospace Research Institute) conducts the clean room to control and minimize the contamination effect. This paper introduces the principle of contamination and the method of measure and analysis for the contamination.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.28-35
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• 2017

A main oxidizer shutoff valve controls the supply of the oxidizer flow into the combustion chamber of a liquid rocket engine. This shutoff valve also carries out the pre-chilling of oxidizer supply lines by permitting recycling flow for stable transient start of the engine. In the present paper, the flow tests for the recycling line of the valve were conducted in order to evaluate the cooling performance of the main oxidizer shutoff valve. In addition, cryogenic life-cycle tests were performed with an assumption of the increase of spring constant with increasing valve operating times due to ductile-brittle transition effects.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.174-180
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• 2006

The present paper describes transient thermal and mechanical analyses of a lox/kerosene type turbopump in a LRE(Liquid Rocket Engine). Turbopumps are used to pressurize propellants to achieve higher specific impulse of LRE. The turbopump under development has been designed and verified by structural analyses using finite element methods. Some parts of the turbopump operate under cryogenic environments, while the others work under ambient and high temperature environments. Therefore, numerical analysis at a turbopump system level is essential. In this study, casing assemblies of lox pump and fuel pump were analyzed to determine strength test and air-tightness test conditions. Also, some operational stress and strains of fuel pump casings were measured and analyzed. Based on these results, stress concentration of fuel pump casings during the operation could be successfully predicted.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.8-14
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• 2015

More and more, spaces are decreasing which satisfy multiple requirements for wind power plants. However, areas which have excellent wind resources and are free to civil complaints occupy a large space, although they are exposed to the cryogenic environment. This study conducted a thermal-fluid analysis of a cryogenic chamber for testing large wind turbine parts exposed to the cryogenic environment. The position of supply air is placed to the upper area to compare each cooling performance for each location of various outlets in mixing ventilated conditions. The study carried out CFD analysis for the chamber both with and without a test object. For the cases without the test object, the air temperature of the upper supply and down extract type chamber was cooled faster by 5-100% than the others. However, for the cases with the test object, the object temperature of upper supply and center extract on the opposite side type chamber was cooled faster by 33-132% than the others. The cooling performance by the air inside the chamber and the test object did not show the same pattern, which implicates the need to consider the cooling performance by not only the air but also the test object in the large cryogenic chamber design for testing large parts.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.2
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• pp.81-88
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• 2016

There are many types of national and international standards for low temperature tests depending on the products. This study conducted CFD analysis and estimation of the energy efficiency of the chamber both with and without a test object by considering variations of COP and specific volume according to temperature. The supply air was located in the upper area to compare the cooling performance for each location using various outlets in mixed ventilated conditions. For cases without the test object, the air temperature of the upper supply and center extract on the opposite side type chamber cooled faster than other areas by 4.3~29.8%. However, for cases with the test object, the object temperature of the upper supply and lower extract type chamber cooled faster than the other areas by 7.2~31.5%. The cooling efficiency of the air inside the chamber and the test object did not show the same pattern, which indicates the need to consider the cooling performance by not only the air but also the test object in the cryogenic chamber design for testing.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.49-57
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• 2023

The autogenous pressurization has been widely adopted for propulsion systems of next-generation reusable rockets due to its low cost and high reliability. The autogenous pressurization has a simple structure, but an understanding of the heat and mass transfer occurring inside the tank is essential. For this reason, a simulation test of the autogenous pressurization was conceived. The experiment equipment was constructed based on overseas pressurization test facilities cases and expert advice. Unlike the actual autogenous pressurization system, the propellant tank was insulated to exclude external influences. The pressurized gas supply line and the propellant pipe were separated. Using the manufactured autogenous pressure experiment equipment, it is possible to evaluate the condensation phenomenon of pressurants in cryogenic propellants, comparison of the efficiency of pressurization using helium and evaporated gas and the pressurization capacity according to the temperature of pressurant.

• Journal of Astronomy and Space Sciences
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• v.23 no.4
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• pp.425-434
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• 2006

The KASINICS (KASI Nea.-Infrared Camera System) is a ground-based instrument developed by the Korea Astronomy and Space Science Institute (KASI). We developed a temperature and vacuum monitoring system for operating the KASINICS. The system consists of hardware and software parts. The acquired data we saved on a hard disk in a real-time mode. This system on also be applied to general cryogenic instruments. We tested our monitoring system for the cooling and vacuum performance of the KASINICS. The results show that our system is efficient and stable for the operation of the KASINICS.

• Journal of IKEEE
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• v.23 no.4
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• pp.1230-1235
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• 2019

In this paper, we have developed sensor composited heater of 2-pin, and unified the fuel filter. In order to evaluate the performance of the 2-pin sensor composited fuel heater, we have make of the low temperature fluidity system. The one measure and analysis the electrical and oil flow quantity characteristics at an input and out port of 2-pin sensor composited fuel heater. Especially, in the characteristics verification elements of the proposed goods, we use the test chamber for the temperature variable and oil flow quantity test, and designed an embedded system for interfacing an engine. By interfacing both user and the system, it support an experimental and date gathering function in 2-pin sensor composited fuel filter. And then test the temperature, oil pressure, electrical characteristics and oil flow quantity in variable status from - 30 ℃ to + 80 ℃. These can help us to determine the quality and performance of elementary goods.

• Journal of the Korea Institute of Building Construction
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• v.16 no.1
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• pp.67-76
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• 2016

Concrete exposed to severely low temperature below $-20^{\circ}C$ should be provided with proper heat supplying curing to protect the concrete from early frost damage at the time of pouring.meanwhile, so far, effective heat curingmethods of the concrete under severely low temperature are not well established in Korea. For this reason, the objective of this paper is to provide effective heat curingmethod of concrete exposed to severely low temperature to protect early frost damage by varying the combination of heat curingmaterial combinations. Temperature history,maturity development and core strength results are investigated. Fourmock-up specimens simulating slab, wall and column were prepared and heat insulation, heat supplying and both were applied. Test results indicate that the combination of quadruple layer bubble sheet(4BS) and embedding of heating cable has desirable performance for a slab, and heat supplying curing inside heat enclosure and heat generationmat also shows desirable performance for a wall, and for a column, use of EPS heat insulation has proper performance against early frost damage, which reaches $45^{\circ}D{\cdot}D$ and helps the concretemaintain above $0^{\circ}C$ within 3 days. Themethodsmentioned above are believed to be optimum protection from early frost damage of the concrete under $-20^{\circ}C$.