• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1111-1116
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• 2011

Heat exchangers have been used for the automotive, HVAC systems, and other various industrial facilities, so the market is very wide. In general, high-efficiency heat exchangers with louver fins are used in the dust-free environment while heat exchangers with wavy fins are used for dusty environment such as construction site, etc. In this study, numerical analysis has been performed for typical heat exchangers, used as oil coolers or fuel coolers, with dual cell model that can handle different grids for the air-side and oil-side of heat exchangers. First wind tunnel tests were conducted to obtain one-dimensional thermal performance data of heat exchangers. Then, heat release rates with varying air flows were numerically predicted using the three-dimensional dual-cell model. The model can greatly enhance the accuracy of thermal design since it includes the effects of nonuniformity of air flows across heat exchangers.

• Journal of the Korean Solar Energy Society
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• v.31 no.3
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• pp.101-108
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• 2011

This study aims to suggest an energy consumption improvement plan for university buildings through an analysis of energy consumption. Upon a simulation of subject building to interpret energy consumption, it was found that 154.07kWh/$m^2$ of energy is consumpted annually. Improvement of design elements can cut down the energy consumption to 135.61kWh/$m^2$ according to an energy reduction analysis related to envelope performance improvement. Additional improvement of lights and heat exchanger can curtail annual energy consumption to 108.32kWh/$m^2$. Also, an analysis of energy consumption while increasing indoor temperature gradually showed that the two factors are in proportion. $6^{\circ}C$ higher temperature requires over twice of the current energy. Based on this survey result, performance improvement due to building management and envelope elements which influence to building cooling and heating loads can curtail building energy consumption.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.4
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• pp.44-50
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• 2011

Turbulent mixing of hot and cold coolants is one of the possible causes of high cycle thermal fatigue in piping systems of nuclear power plants. A typical situation for such mixing appears in turbulent flow through a T-junction. Since the high cycle thermal fatigue caused by thermal striping was not considered in the piping fatigue design in several nuclear power plants, it is very important to evaluate the effect of thermal striping on the integrity of mixing tees. In the present work, before conducting detailed evaluation, three thermal striping evaluation methodology suggested by EPRI, JSME and NESC are analyzed. Then, a by-pass pipe connected to the shutdown cooling system heat exchanger is investigated by using these evaluation methodology. Consequently, the resulting thermal stresses and the fatigue life of the mixing tee are reviewed and compared to each other. Futhermore, the limitation of each methodology are also presented in this paper.

• Journal of Bio-Environment Control
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• v.11 no.3
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• pp.101-107
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• 2002

This study was carried out to improve the performance of heat recovery device attached to exhaust gas flue connected to combustion chamber of greenhouse heating system. Three different units were prepared far the comparison of heat recovery performance; A-type is exactly the same with the typical one fabricated for previous study of analyzing heat recovery performance in greenhouse heating system, other two types (B-type and C-type) modified from the control unit are different in the aspects of airflow direction (U-turn airflow) and pipe arrangement. The results are summarized as follows ; 1. In the case of Type-A, when considering the initial cost and current electricity fee required for system operation, it was expected that one or two years at most would be enough to return the whole cost invested. 2. Type-B and Type-C, basically different with Type-A in the aspect of airflow pattern, are not sensitive to the change of blower capacity with higher than 25m$^3$.min$^{-1}$ . Therefore, heat recovery performance was not improved so significantly with the increment of blower capacity. This was assumed to be that air flow resistance in high air capacity reduced the heat exchange rate as well. Never the less, compared with control unit, resultant heat recovery rate of Type-B and Type-C was improved by about 5％ and 13％, respectively 3. Desirable blower capacity of these heat recovery units experimented were expected to be about 25m$^3$.min$^{-1}$ , and at the proper blower capacity, U-turn airflow units showed better heat recovery performance than control unit. But, without regard to the type of heat recovery unit, it was recommended that comprehensive consideration of system's physical factors such as pipe arrangement density, unit pipe length and pipe thickness, etc., was required for the optimization of heat recovery system in the aspects of not only energy conservation but economic system design.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.3
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• pp.123-128
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• 2020

Analysis of the 2016 Gyeongju earthquake and the 2017 Pohang earthquake showed the characteristics of a typical high-frequency earthquake with many high-frequency components, short time strong motion duration, and large peak ground acceleration relative to the magnitude of the earthquake. Domestic nuclear power plants were designed and evaluated based on NRC's Regulatory Guide 1.60 design response spectrum, which had a great deal of energy in the low-frequency range. Therefore, nuclear power plants should carry out seismic verification and seismic performance evaluation of systems, structures, and components by reflecting the domestic characteristics of earthquakes. In this study, high-frequency amplification factors that can be used for seismic verification and seismic performance evaluation of nuclear power plant systems, structures, and equipment were analyzed. In order to analyze the high-frequency amplification factor, five sets of seismic time history were generated, which were matched with the uniform hazard response spectrum to reflect the characteristics of domestic earthquake motion. The nuclear power plant was subjected to seismic analysis for the construction of the Korean standard nuclear power plant, OPR1000, which is a reactor building, an auxiliary building assembly, a component cooling water heat exchanger building, and an essential service water building. Based on the results of the seismic analysis, a high-frequency amplification factor was derived upon the calculation of the floor response spectrum of the important locations of nuclear power plants. The high-frequency amplification factor can be effectively used for the seismic verification and seismic performance evaluation of electric equipment which are sensitive to high-frequency earthquakes.