• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.1
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• pp.76-83
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• 2011

This paper focuses on the thermal design of a signal processor in Micro-Wave Seeker. High temperature environment and ESS(Environmental Stress Screening) test condition should be considered in designing a signal processor. First, we performed the thermal analysis to know conditions under which a signal processor is thermally reliable. As a result of thermal analysis, we found that adopting heat transfer block to the thermally fragile components is most efficient, because the heat transfer block can control the thermal loads of the individual components. Next, we verified this solution by numerical simulation and experiment and concluded that thermal reliability of a signal processor can be achieved. Maximum temperature difference between numerical simulation and experiment is about $2^{\circ}C$.

• Journal of Aerospace System Engineering
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• v.10 no.4
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• pp.26-34
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• 2016

In a number of industries, porous insulations have been frequently used, reducing thermal insulation space through excellent performance of the thermal insulation's characteristics. This paper suggests an effective thermal conductivity prediction model. Firstly, we perform a literature review of traditional effective thermal conductivity prediction models and compare each model with experimental heat transfer results. Furthermore, this research defines the effectiveness of thermal conductivity prediction models using experimental heat transfer results and the Zehner-Schlunder model. The newly defined effective thermal conductivity prediction model has been verified to better predict performance than other models. Finally, this research performs a transient heat transfer analysis of a thermal protection system with a porous insulation in a high speed vehicle using the finite element method and confirms the validity of the effective thermal conductivity prediction model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.3
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• pp.201-209
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• 2009

The objective of present research work is to design the heat conductive mould to improve cooling characteristics of the injection mould for a mouse. In order to obtain the high cooling rate of the mould, a heat conductive mould with three different materials was designed. The materials of the base structure, the mid-layer and the molding part of the heat conductive mould were chosen as Cu-Ni alloy (Ampcoloy 940) to improve the heat conductivity of the mould, Ni-Cu alloy (Monel 400) to reduce a thermal stress, injection tool steel (P21), respectively. Through the three-dimensional transient heat transfer analysis and the thermal stress analysis, the effects of the geometrical arrangement of each material on the cooling characteristics and the thermal stress distribution were examined. From the results of the analyses, a proper design of the thermal conductive mould was obtained.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.205-210
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• 2002

This article presents an integrated modeling approach for coupled analysis of heat transfer and microstructure evolution in welding carbon steel. The modeling procedure utilizes commercial [mite element code ABAQUS/Standard as the platform for solving the equation of heat conduction. User subroutines that implement computational thermodynamics and kinetics models are integrated with the FEA code to compute the transient microstructure evolution. In this study, the integrated models are applied to simulate the hot-tap repair welding of carbon steel pipeline. Microstructural components are treated as user output variables. Based on the predicted microstructure and cooling rates, hardness distributions in the welds were also predicted. The predicted microstructure and hardness distribution were found in good agreement with metallographic examinations and hardness measurements. This study demonstrates the applicability of computational models for the development of welding procedure for in-service pipeline repair.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.831-846
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• 2012

KAERI has developed a two-phase CFD code, CUPID, for a refined calculation of transient two-phase flows related to nuclear reactor thermal hydraulics, and its numerical models have been verified in previous studies. In this paper, the CUPID code is validated against experiments on the downcomer boiling and moderator flow in a Calandria vessel. Physical models relevant to the validation are discussed. Thereafter, multi-scale thermal hydraulic analyses using the CUPID code are introduced. At first, a component-scale calculation for the passive condensate cooling tank (PCCT) of the PASCAL experiment is linked to the CFD-scale calculation for local boiling heat transfer outside the heat exchanger tube. Next, the Rossendorf coolant mixing (ROCOM) test is analyzed by using the CUPID code, which is implicitly coupled with a system-scale code, MARS.

• Journal of Korea Foundry Society
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• v.12 no.5
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• pp.378-389
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• 1992

A numerical model based on the SOLA-VOF method, which can calculate the transient free-surface configuration of the melt, has been developed in order to analyze melt flow in the investment mold. The computational results were compared with experimental results obtained from pure aluminum investment casting. Heat transfer analysis, with and without consideration of melt flow effect has been performed. It can be concluded that analysis of melt flow in the investment mold, provides the optimum conditions for gating design. It also enables more precise solidification simulation, since heat loss, while filling the thin and complex investment mold, plays an important role in determining the solidification sequence.

• International Journal of Korean Welding Society
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• v.2 no.2
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• pp.1-6
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• 2002

This article presents an integrated modeling approach for coupled analysis of heat transfer and microstructure evolution in welding carbon steel. The modeling procedure utilizes commercial finite element code ABAQUS/Standard as the platform for solving the equation of heat conduction. User subroutines that Implement computational thermodynamics and kinetics models are integrated with the FEA code to compute the transient microstructure evolution. In this study, the integrated models are applied to simulate the hot-tap repair welding of carbon steel pipeline. Microstructural components are treated as user output variables. Based on the predicted microstructure and cooling rates, hardness distributions in the welds were also predicted. The predicted microstructure and hardness distribution were found in good agreement with metallographic examinations and hardness measurements. This study demonstrates the applicability of computational models for the development of welding procedure for in-service pipeline repair.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.289-296
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• 2017

This study aimed to analyze the deck floor heating system of an outdoor swimming pool in terms of the thermal capacity/output and the surface temperature distribution based on the outdoor temperature, to design for anti-freezing during winter. Through the transient heat transfer simulation with PHYSIBEL and theoretical equations, the surface temperature distribution of the floor heating system at two outdoor conditions in Jeju, were calculated and evaluated. The results indicate that the specific thermal output required for maintaining $4^{\circ}C$ surface temperature at the design outdoor temperature of $0.1^{\circ}C$, was about $90W/m^2$. This performance analysis can be applied for future design criteria, including optimizations of system capacity and size.

• Progress in Superconductivity and Cryogenics
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• v.22 no.4
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• pp.51-56
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• 2020

In order to increase thrust of the space launch vehicle, liquid oxygen as an oxidizer and kerosene or liquid hydrogen as a fuel are generally used. The oxidizer tank and fuel tanks are manufactured by composite materials such as CFRP (Carbon Fiber Reinforced Plastic) to increase pay load. The thermal stress of the cryogenic propellant tank should be considered because it has large temperature gradient. In this study, to confirm the design integrity of the oxidizer tank of liquid oxygen, a numerical analysis was conducted on the thermal stress and temperature distribution of the tank for various charging speed of the cryogenic fluid from 100 ~ 900 LPM taking into account the evaporation rate of the liquid nitrogen by convective heat transfer outside the tank and boiling heat transfer inside the tank. The thermal stress was also calculated coupled with the temperature distribution of the CFRP tank. Based on the analysis results, the charging speed of the LN2 can majorly affects the charging time and the resultant thermal stress.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.792-801
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• 2000

The problem of phase change from liquid to solid in the inviscid plane-stagnation flow is theoretically investigated. The solution at the initial stage of freezing is obtained by expanding it in powers of time, and the final equilibrium state is determined from the steady-state governing equations. The transient solution is dependent on the three dimensionless parameters, but the equilibrium state is determined by one parameter of (temperature ratio/conductivity ratio). The effect of the fluid flow on the growth rate of the solid in the pure conduction problem can be clearly seen from the solution of the initial stage and the final equilibrium state. The characteristics of the transient heat transfer at the surface of the solid and the liquid side of the solid-liquid interface for all the dimensionless parameters are elucidated.