• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.148-152
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• 1997

A numerical method is presented to predict and analyze the shape and the temperature history of a growing billet produced form the "spray forming" which is a fairly new near net-shape manufacturing process. It is important to understand the mechanism of billet growing and the cooling history of the spray deposited body, because one can obtain a billet with the desired final shape without secondary operations by accurate control of the billet shape and, moreover, growing velocity together with the cooling rate define the microstructure of the final formed product. In the present study, a theoretical model is first established to predict the shape of the billet and next the transient axisymmetric heat conduction problem with growing domain is solved using the so called "front tracking finite element technique".ent technique".uot;.

• Journal of The Korean Astronomical Society
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• v.40 no.4
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• pp.161-164
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• 2007

We calculate the evolution of multiple supernova (SN) explosions inside a pre-exiting bubble blown up by winds from massive stars, using one-dimensional hydrodynamic simulations including radiative cooling and thermal conduction effects. First, the development of the wind bubble driven by collective winds from multiple stars during the main sequence is calculated. Then multiple SN explosion is loaded at the center of the bubble and the evolution of the SN remnant is followed for $10^6$ years. We find the size and mass of the SN-driven shell depend on the structure of the pre-existing wind bubble as well as the total SN explosion energy. Most of the explosion energy is lost via radiative cooling, while about 10% remains as kinetic energy and less than 10% as thermal energy of the expanding bubble shell. Thus the photoionization and heating by diffuse radiation emitted by the shock heated gas is the most dominant form of SN feedback into the surrounding interstellar medium.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.10 no.1
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• pp.1-6
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• 2014

In order to evaluate the performance of ground heat source in thermal labyrinth on pre-heating in winter season and pre-cooling in summer season, the followings are made as a conclusion through case study of H project by using the weather data from Korea meteorological administration and CFD model. By making outdoor air inlet via ground heat source in thermal labyrinth for conduction, convection and etc., the temperature rise is $13.4^{\circ}C$as the effect of pre-heating in winter season. On the other hand, as the effect of pre-cooling in summer season, the temperature decrease is $7.2^{\circ}C$. The energy saving rate by the application of ground heat source in thermal labyrinth is 9.1%.

• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.47-50
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• 2019

The paper gives the results of the experiments with a model two-section REBCO solenoid cooled by either gaseous helium (GHe) or sub-cooled/solid nitrogen (SN2) in (50-77) K temperature range. The major cooling source was a single-stage cryocooler Sumitomo CH-110 with the cooling power of 175 W and 130 W at 77 K and 50 K respectively. The coil itself was not directly conduction cooled. We compare the time taken by both coolants to obtain the temperature of the magnet of about 50 K and the homogeneity of the temperature distribution within the cryostat. Test results for the coil operation in solid nitrogen together with the comparison of its critical properties in SN2 and GHe are also presented.

• Progress in Superconductivity and Cryogenics
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• v.12 no.2
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• pp.25-28
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• 2010

A cooldown time is one of the major factors in many cryocooler applications, especially for the design of conduction-cooled superconducting apparatus. The estimation of cooldown seeks the elapsed time to cool thermal object by a cryocooler during initial cooldown process. This procedure includes the dimension of cold mass, heat transfer analysis for cryogenic load and available refrigerating capacity of a cryocooler. This method is applied to the specific cooling system for a 3 Tesla superconducting magnet cooled by a two-stage GM cryocooler. The result is compared with that of experiment, showing that the results of proposed method have a good agreement with experiments during initial cooling of superconducting magnet.

• Tribology and Lubricants
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• v.11 no.5
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• pp.150-155
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• 1995

In order to analyze the thermal effects of the rotor models, the finite element technique was used in this study. The length of the hat was investigated as a design parameter. At the start of each brake application the disk surface temperature rapidly increases to a maximum value and then decays due to external cooling and thermal conduction to the hat. The calculated results indicate that the long length of the hat shows the minimum deformation in axial direction, which is related to the thermal problems, coned wear, vibration and noise.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3559-3566
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• 2009

Heating and cooling plate are separately used for heating and cooling cast dies for footwear parts. However, this has a disadvantage that it takes a long time to manufacture footwear parts etc.. In the present study, the pipe-inserted cast die for press forming process was proposed to substitute heating and cooling plate. The temperature distribution on the pipe-inserted cast die was analyzed by numerical work using a FEM. And its temperature was measured by LabView. A manufacturing by the pipe-inserted cast die for press forming process was effectively verified, especially in a productivity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.867-868
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• 2011

Transient Analysis on heat transfer of rocket engine combustion chamber and wall temperature variation was carried out, especially, calculations of LOx/kerosene rocket engine with/without fuel film-cooling were conducted. Convective and radiative heat flux inside combustion chamber wall were calculated by the empirical equations for rocket engine combustion, and conduction of wall interior was calculated by numerical method with 2D axisymmetric grid. In this calculations the transient variations of wall temperature, the location changes of peak temperature and so on affected by film-cooling were analyzed.

• Nuclear Engineering and Technology
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• v.32 no.4
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• pp.410-423
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• 2000

A two-dimensional numerical model is developed and applied to the LAVA-EXV tests performed at the Korea Atomic Energy Research Institute (KAERI) to investigate the external cooling effect on the thermal margin to failure of a reactor pressure vessel (RPV) during a severe accident. The computational program was written to predict the temperature profile of a two-dimensional spherical vessel segment accounting for the conjugate heat transfer mechanisms of conduction through the debris and the vessel, natural convection within the molten debris pool, and the possible ablation of the vessel wall in contact with the high temperature melt. Results of the sensitivity analysis and comparison with the LAVA-EXV test data indicated that the developed computational tool carries a high potential for simulating the thermal behavior of the RPV during a core melt relocation accident. It is concluded that the main factors affecting the RPV failure are the natural convection within the debris pool and the ablation of the metal vessel, The simplistic natural convection model adopted in the computational program partly made up for the absence of the mechanistic momentum consideration in this study. Uncertainties in the prediction will be reduced when the natural convection and ablation phenomena are more rigorously dealt with in the code, and if more accurate initial and time-dependent conditions are supplied from the test in terms of material composition and its associated thermophysical properties.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.365-369
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• 2007

The solid rocket interacts circumscriptively in terms of is many more than liquid rocket. It is uncontrollable than liquid rocket because all part of combustion is decided such as Mixture ratio of propellant, burning time and area. However, production cost is cheap and because authoritativeness security can be easy and enlarge the early speed that follow thrust-to-weight ratio, it is used comprehensively by small size rocket. Considered about nozzle cooling to control phenomenon that burn by thermal conduction in interior wall of nozzle that follow in thrust increase of solid rocket and erosion phenomenon by combustion gas of high speed.