• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.937-938
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• 2006

Tungsten heavy alloys with different ratios of Mo and Ni-Fe matrix were liquid-phase-sintered to investigate their microstructural evolution. Results indicated that increased Mo in the alloy promoted the formation of a (W,Mo)(Ni,Fe) type intermetallic compound in the furnace-cooled condition. It was a monoeutectic reaction when the added Mo content was higher than 49at.%, or a eutectic reaction when this value was between 37at,% to 49at.%. When Mo was added between 25at.% to 37at.%, the precipitation of the intermetallic compound took place by either a eutectoid or peritectoid reaction.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.281-284
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• 2004

According to the National Space Program of Korea, KARI (Korea Aerospace Research Institute) has been developing a large space simulator (working dimension; $\Phi8m\;\times\;L10m$) to verify the performance of future large satellites under the space environment conditions. Especially, a very low temperature condition of space will be simulated by shrouds covering the inside surface of the vessel. The surface of shrouds will be cooled down to 17K by liquid nitrogen (LN2) from ambient temperature and hence, an optimal LN2 circulation system design is necessary to remove gaseous nitrogen (GN2) sufficiently and maintain the shrouds at the LN2 temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.9
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• pp.845-852
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• 2001

The phenomena of energy separation in vortex tubes was investigated experimentally to see the effects of the conductivity of a tube and convective heat transfer on the outer surface of a tube. The experiment was carried out with different conductivity (pyrex, stainless steel and copper) of a tube and three kinds of convective heat transfer modes (adiabatic condition, natural convection (air) and forced convection (water) on the outer surface of a tube. the results were obtained that hot exit fluid temperature was highly affected by a change of conductivity of a tube when the outer surface was cooled by the forced convection of water. However, the cold exit temperature was little affected by heat transfer modes on the outer surface in vortex tubes.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.3
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• pp.317-324
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• 2010

It was used as measuring system to diagnose insulating condition, by which was kept a insulating resistance of inner stack and at the same time was cooled electrochemical heat of reaction of FCEV(fuel cell electric vehicle) stack that used a compressed hydrogen gas reacting with oxygen in accordance with variation on thermal degradation of nonconductive heat transfer fluid. Consequently it was developed a cylindrical multi-terminal capacitive-conductive sensor that could be attached to the internal surface of cooling system pipe to evaluate capacitance and conductivity of heat transfer fluid.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1846-1849
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• 2000

Off-line and on-line partial discharges were measured on a 828MVA, 22kV and direct hydrogen-cooled large turbine generator. Partial discharge tests were conducted using digital partial discharge detector(PDD) and turbine generator analyzer(TGA). PDD and TGA showed that off-line partial discharge pattern seems to be very, similar to that found with on-line. Most of the partial discharge is originating with the stator slot in the three phases. As the partial discharge activity is very low, the stator insulation condition of this generator is very good.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.11
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• pp.1125-1133
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• 2001

Since the surface temperature of the evaporating tube in an ammonia unit cooled is lower than the dew point of atmosphere, the moisture in the atmosphere condenses and the frost grows on the tube. The frost of liquid film decreases the heat transfer rate. The reliable analysis of the heat transfer is required for the prediction of the optimal design of the ammonia unit cooler. For the specific commercial model, the performance was numerical1y estimated for the variation of operating condition and geometric configuration. It is found that there exists an optimum range for the parameters such as mass flow rate of air and refrigerant, humidity, refrigerant quality, fin pitch, the number of step, the number of rows and the pattern of refrigerant path.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.148-154
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• 2004

As a rocket propellent of hydrocarbon fuels, the characteristics of liquefied natural gas was evaluated with the viewpoint of the constituents and content, the cooling performance as a coolant, and characteristic velocity and specific impulse as parameters of the engine performance. Content of methane was a principal factor to determine the characteristics as a rocket propellant and more than 90 % of it was needed as a fuel and coolant in the regenerative cooled liquid rocket engine. Some constituents of the liquefied natural gas can be frozen by the pre-cooling of the pipe lines, therefore they can be a factor disturbing the normal working of engine. In case the content of methane is around 90% in the liquefied natural gas, a normalized stoichiometric O/F mixture ratio of 0.75 is suggested for a nominal operation condition to get the maximum specific impulse and characteristic velocity.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.2
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• pp.59-70
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• 1990

Crack of breaking toughness of most Ceramics material is 1-5MPa .root.m but that of Zirconia Ceramics is improved to be 6-8MPa .root.m and its development of machining difficult-to-machine material is on the rise as urgent subject. For general Zirconia Ceramics machining, diamond grinding wheel is generally used by selecting an appropriate one and establishing grinding condition but due to such limitations as economics, grinding efficiency and machining geometry, great interest in machining method being used for diamond tool is emphasized. But it is reported that diamond tool is oxidized by cutting heat in the air and is graphitized in vacuum, which causes bad effects on tool life. In this study, to restraint cutting heat the internal side of tool is cooled, and restraint low temperature cooling system and being experimented. Further, the machinability of diamond tool for Zirconia Ceramics machining is analyzed with respect to tool wear and stress.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.31-44
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• 2019

This study simulated a control rod assembly (CRA), which is a part of reactor shutdown systems, in immersed and fluid flow conditions. The CRA was inserted into the reactor core within a predetermined time limit under normal and abnormal operating conditions, and the CRA (which consists of complex geometric shapes) drop behavior is numerically modeled for simulation. A full-scale prototype CRA drop test is established under room temperature and water-fluid conditions for verification and validation. This paper describes the details of the numerical modeling and analysis results of the several conditions. Results from the developed numerical simulation code are compared with the test results to verify the numerical model and developed computer code. The developed code is in very good agreement with the test results and this numerical analysis model and method may replace the experimental and CFD method to predict the drop behavior of CRA.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.932-941
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• 2021

This paper suggests a fracture simulation method for SFR metallic fuel pin under accident condition. Two major failure mechanisms - creep damage and eutectic penetration - are implemented in the suggested method. To simulate damaged element, stress-reduction concept to reduce stiffness of the damaged element is applied. Using the proposed method, the failure size of cladding can be predicted in addition to the failure time and failure site. To verify the suggested method, Whole-pin furnace (WPF) test and TREAT-M test conducted at Argonne National Laboratory (ANL) are simulated. In all cases, predicted results and experimental results are overall in good agreement. Based on the simulation result, the effect of eutectic-penetration depth representing failure behavior on failure size is studied.