• Journal of Welding and Joining
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• v.35 no.3
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• pp.82-87
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• 2017

Recent trends in shipbuilding and offshore industries are a huge increase in the ship size and the exploration and production of oil and natural gas in the arctic offshore region. High performance steel plates are required by these industrial trends. Also in IMO(International Maritime Organization) has begun to regulate of fuel of ship to environmental protection, therefore it is little bit difficult to use bunker-C oil to working ship. As the problem of environmental change such as global warming is emerged, the operation of the ship is considered to be involved in the environmental change problem, and the regulation of environmental pollution is gradually strengthened. As these environmental regulations are strengthened demand for LNG fuel ships is rapidly increasing. Currently, cryogenic steels used in LNG tanks include aluminum alloy, SUS 304, and 9%-Ni steel. Those steels are has high cost to construction of large LNG carrier. The new materials were suggested several steel mills to decrease construction cost and easy construction. The new cryogenic steel should be evaluate safety to applied real structure include LNG ship. Therefore, in this study, fracture toughness of weld joints were investigated with cryogenic steel for application of LNG tank.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.642-650
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• 2016

One of the most feasible solution for reducing the excessive energy consumption and carbon dioxide emission is usage of more efficient fuel such as hydrogen. As is well known, there are three viable technologies for 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, the cryogenic liquid storage has a significant disadvantage of boiling losses. That is, high performance of thermal insulation systems must be studied for reducing the boiling losses. This paper presents an experimental study on the effective thermal conductivities of the composite layered insulation with aerogel blankets($Cryogel^{(R)}$ Z and $Pyrogel^{(R)}$ XT-E) and Multi-layer insulation(MLI). The aerogel blankets are known as high porous materials and the good insulators within a soft vacuum range($10^{-3}{\sim}1$ Torr). Also, MLI is known as the best insulator within a high vacuum range(<$10^{-6}{\sim}10^{-3}$ Torr). A vertical axial cryogenic experimental apparatus was designed to investigate the thermal performance of the composite layered insulators under cryogenic conditions as well as consist of a cold mass tank, a heat absorber, annular vacuum space, and an insulators space. The composite insulators were laminated in the insulator space that height was 50 mm. In this study, the effective thermal conductivities of the materials were evaluated by measuring boil-off rate of liquid nitrogen and liquid argon in the cold mass tank.

• Composites Research
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• v.19 no.4
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• pp.23-30
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• 2006

In the development of a cryogenic propellant tank, the proper selection of adhesives to bond composite and metal liner is important for the safety of operation. In this study, 3 types of adhesives were tested for the ability to bond CFRP composites developed for cryogenic use and aluminum alloy (Al 6061-T6) for lining the tank using double-lap joint specimens. The double-lap joint specimens were tested inside an environmental chamber at room temperature and cryogenic temperature ($-150^{\circ}C$) respectively to compare the bond strength of each adhesive and fracture characteristics. The material properties with temperature of component materials of double-lap joints were measured. In addition, ABAQUS was used for the purpose of analyzing the experimental results.

• Transactions of the Korean hydrogen and new energy society
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• v.35 no.1
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• pp.34-39
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• 2024

Korea government is trying to supply liquid hydrogen from another country to domestic The research for liquid hydrogen transportation and liquefaction plant of hydrogen underway for several years, and empirical research is also planned in the future. Along with the development of liquid hydrogen transport ship/liquefaction plant technology, the development of liquid hydrogen reception base technology must be carried out. In this study, a concept level liquid hydrogen receiving terminal is constructed based on the process of the LNG receiving terminal. Based on this, a study is conducted on the development of analysis technology for the amount of BOG (pipe, tank) generated during cooldown and unloading in the liquid hydrogen unloading line (loading arm to storage tank). The research results are intended to be used as basic data for the design and liquid hydrogen receiving terminal in the future.

• Journal of Welding and Joining
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• v.17 no.3
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• pp.50-54
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• 1999

Feasibility study of the application of a developed annealed austenitic stainless steel at cryogenic temperature has been performed for membrane tank of LNG ship. Chemical properties of developed stainless steel are compared with a domestic commercial stainless steel and a foreign stainless steel which are used for LNG ships. Tensile properties at cryogenic temperature and fatigue strength at room temperature are measured for but and lap joints which are TIG welded specimens. Developed stainless steel having a small amount of titanium component shows the finest grain size in the HAZ, compared with the other stainless steel studied. Tensile strength, elongation and fatigue strength of the developed stainless steel are equal to those of the foreign stainless steel studied and are higher than the domestic commercial stainless steel studied.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1171-1175
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• 2017

Cryogenic helium gas is used as the pressurant for the oxidizer pressurization of DR(Damper Receiver) sphere in the PSD(Pogo Suppression Device) system and liquid oxygen is used as the oxidizer for the propellant in Korea Space Launch Vehicle-II. The helium gas is stored in pressurant cylinders inside the cryogenic liquid oxygen tank and liquid oxygen is stored in the oxidizer tank. In this study, the performance test of PSD liquid oxygen drain valve for KSLV-II was considered.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.8
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• pp.426-431
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• 2015

The advantages of a printed circuit heat exchanger (PCHE) are the compactness and efficiency derived from its heat-transfer characteristics; furthermore, a PCHE for which a diffusion bonding method was used during production can be applied to extreme environments such as a cryogenic condition. In this study, a micro-channel PCHE fabricated by diffusion bonding was investigated in a cryogenic environment regarding its thermal performance and the pressure drop. The test rig consists of an LN2 storage tank, vaporizers, heaters, and a cold box, whereby the vaporized cryogenic nitrogen flows in hot and cold streams. The overall heat-transfer coefficients were evaluated and compared with traditional correlations. Lastly, we suggested the modified heat-transfer correlations for a PCHE in a cryogenic condition.

• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.8-16
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• 2024

Because hydrogen has very low density, a different storage method is required to store the same amount of energy as fossil fuel. One way to increase the density of hydrogen is through liquefaction. However, since the liquefied temperature of hydrogen is extremely low at -252 ℃, it is easily vaporized by external heat input. When liquid hydrogen is vaporized, a self-pressurizing phenomenon occurs in which the pressure inside the hydrogen tank increases, so when designing the tank, this rising pressure must be carefully predicted. Therefore, in this paper, the internal pressure of a cryogenic liquid fuel tank was predicted according to the liquid hydrogen filling ratio. A one-dimensional thermodynamic model was applied to predict the pressure rise inside the tank. The thermodynamic model considered heat transfer, vaporization of liquid hydrogen, and fuel discharging. Finally, it was confirmed that there was a significant difference in pressure behavior and maximum rise pressure depending on the filling ratio of liquid hydrogen in the fuel tank.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.580-597
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• 2013

Three materials SUS304, 9% Ni steel and Al 5083-O alloy, which are considered possible candidate for International Maritime Organization (IMO) type B Cargo Containment System, were studied. Monotonic tensile, fatigue, fatigue crack growth rate and Crack Tip Opening Displacement tests were carried out at room, intermediate low ($-100^{\circ}C$) and cryogenic ($-163^{\circ}C$) temperatures. The initial yield and tensile strengths of all materials tended to increase with decreasing temperature, whereas the change in elastic modulus was not as remarkable. The largest and smallest improvement ratio of the initial yield strengths due to a temperature reduction were observed in the SUS304 and Al 5083-O alloy, respectively. The fatigue strengths of the three materials increased with decreasing temperature. The largest increase in fatigue strength was observed in the Al 5083-O alloy, whereas the 9% Ni steel sample showed the smallest increase. In the fatigue crack growth rate test, SUS304 and Al 5083-O alloy showed a decrease in the crack propagation rate, due to decrease in temperature, but no visible improvement in da/dN was observed in the case of 9% Ni steel. In the Crack Tip Opening Displacement (CTOD) test, CTOD values were converted to critical crack length for the comparison with different thickness specimens. The critical crack length tended to decrease in the case of SUS304 and increase for the Al 5083-O alloy with decreasing temperature. In case of 9% Ni steel, change of critical crack length was not observed due to temperature decrease. In addition, the changing material properties according to the temperature of the LNG tank were analyzed according to the international code for the construction and equipment of ships carrying liquefied gases in bulk (IGC code) and the rules of classifications.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.4
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• pp.33-41
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• 2008

The prelaunch thermal transients in the cryogenic oxidizer tank of liquid propulsion rocket subjected to uniform heat flux from outside are numerically analyzed through thermodynamic equations and heat and mass transfer relations. The prelaunch stage is assumed to be composed of five idealized sub-stages including pressurization process by helium gas injection. The Peng-Robinson equation of state is utilized in the lumped analysis of ullage gas. The liquid region is divided into a number of horizontal layers of uniform properties to account for the thermal stratification. The computational result for the typical case shows that the temperature rise of liquid oxidizer is less than 1K and the adsorbed helium into the liquid is approximately 10g.