• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.175-176
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• 2008

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.23-23
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• 2004

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.98-109
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• 2021

Fundamental parameters describing overall operational characteristics of active cooling systems of a hypersonic flight vehicle are mainly classified into endothermic hydrocarbon fuels, regenerative cooling channels, and materials and system structures. Of primary importance is the improvement of endothermic performance of hydrocarbon aviation fuels in a series of studies developing efficient regenerative cooling systems. In a previous study, therefore, an extensive technical analysis has been carried out on thermal decomposition characteristics of liquid hydrocarbon fuels. As a subsequent study, catalytic cracking and steam reforming technologies have been reviewed to find a way for the improvement of endothermic reaction performance of hydrocarbon aviation fuels.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.63-72
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• 2011

In recent years, hot-stamped components are more increasingly used in the automotive industry in order to reduce weight and to improve the strength of vehicles. In hot stamping process, blank is hot formed and press hardened in a tool. However, in hot stamping without cooling channel, temperature of the tool increases gradually in mass production thus cannot meet the critical cooling rate to obtain high strength over 1500MPa. Warpage occurs in the hot stamped component due to non-uniform stress state caused by unbalanced cooling. Therefore, tools should be uniformly as well as rapidly cooled down by the coolant which flows through cooling channel. In this paper, optimal design method of cooling channel to obtain uniform and high strength of the component is proposed. Optimized cooling channel is applied to the hot press V-bending process. As a result of measuring strength, hardness and microstructure of the hot formed parts, it is known that the design methodology of cooling channel is effective to the hot stamping process.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.1
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• pp.35-44
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• 2011

Mathematical modelling for liquid rocket engine(LRE) main components were conducted to predict the dynamic characteristics when the LRE operates at the transient condition, which include engine start up, shut down, or thrust control. Propellant feeding system is composed of fuel and oxidizer feeding components except for regenerative cooling channel for the fuel circuit. Components modeling of pump, pipe, orifice, control valve, regenerative cooling channel and injector was serially made. Hydraulic tests of scale down component were made in order to validate modelling components. The mathematical models of engine components were integrated into LRE transient simulation program in concomitant with experimental validation.

• Journal of computational fluids engineering
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• v.17 no.3
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• pp.93-98
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• 2012

The injection molding process is suitable for manufacturing complicated plastic products. As the customer request higher quality products increase, realization of the precise dimensional and shape controls is getting more important. For this purpose it is important to obtain uniform cooling procedure over the whole surface of the high temperature molded plastic. Failure to this may lead to different shrinkage speed, internal stresses and unwanted shape deformations. It is necessary to distribute coolant flow rates to the main channel and to the sub-channels properly to insure uniform cooling process when there are parallel cooling channels. In this study, three-dimensional turbulent flow simulations for representative parallel cooling channels were performed. To insure the intended flow rate to each sub-channels, various shape designs for the channel system were investigated. The results show that as the Reynolds number increases the effect of shape design is more profound. Through the proper flow distribution, uniform cooling effects would be expected.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.73-82
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• 2017

Low-cycle thermal fatigue problem resulting from multiple use of a liquid rocket engine has to be considered for the development of a reusable launch vehicle. In this study, life prediction equations suggested by previous researchers were compared as applied to various copper alloy cases to predict fatigue lives from tensile test data. The present study has revealed that among the presently considered life prediction methods, universal slopes method provides the best life prediction result for the copper alloys, and the modified Mitchell's method provides the best life prediction result for oxygen free high conductivity (OFHC) copper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.580-584
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• 2004

In the present study, an evaluation technology for heating channel layout was investigated in SMC molding system design. Conventional design rules of cooling channel in injection molding process were applied to the present work. Finite element thermal analysis with ANSYSTM was performed to evaluate the temperature distribution of mold surface. SMC mold was manufactured to test the effect of a proposed heating channel layout system on the temperature distribution of mold surface and infrared camera was applied to a measurement of temperature. It was shown that infrared camera application was possible in a measurement of temperature distribution on mold surface.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.74-84
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• 2007

The flowfield characteristics in a straight rectangular channel have been investigated through a numerical model to analyze the regenerative cooling system that is used in rocket engine cooling. The supercritical hydrogen coolant introduces strong property variations that have a major influence on the developing flow and heat transfer characteristics. Of particular interest is the improved understanding of the physical characteristics of such flows through parametric studies. The approach used is a numerical solution of the full Navier-Stokes equations in the three dimensional form including the arbitrary equation of state and property variations. The present study compares constant and variable property solutions for both laminar and turbulent flow. For laminar flow, the variation of aspect ratio is examined, while for turbulent flow, the effects of variation of channel length and Reynolds number are discussed.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.114-121
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• 2013

In order to estimate the efficiency of an evaporative heat exchanger having mini channel, the equations to calculate heat exchanger properties, those are air temperatures and water temperatures etc, are derived from the governing equations based on the Navier-Stokes equation, even though there are several assumptions to make problem simplify. There are three heat transfer zones at the mini channel heat exchanger depending on the water condition. So, there are three governing equations and solutions to calculate the properties. As the results of this study, the equations to calculate a saturation point and a dry point are derived to evaluate an evaporative heat exchanger having micro channel. It is supposed to predict and evaluate the performance of a mini channel heat exchanger with evaporation of liquid.