• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1604-1615
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• 2023

In an open-pool type research reactor with a downward forced flow in the core, pipes can be under sub-atmospheric pressure because of the large pressure drop at the reactor core in the atmospheric pool. Sub-atmospheric pressure can result in air inflow into the pipe from the pressure difference between the atmosphere and the inside of the pipe, which in a postulated pipe break scenario can lead to the breakdown of the cooling pump. In this study, a plant-scale experiment was conducted to study air inflow in large piping systems by considering the actual operational conditions of an advanced research reactor. The air inflow rate was measured, and the entrained air was visualized to investigate the behavior of air inflow and flow regime depending on the pipe break size. In addition, the developed drift-flux model for a large vertical pipe with a diameter of 600 mm was compared with other correlations. The flow regime transition in a large vertical pipe under downward flow was also studied using the newly developed drift-flux model. Consequently, the characteristics of two-phase flow in a large vertical pipe were found to differ from those in small vertical pipes where liquid recirculation was not dominant.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.2
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• pp.68-76
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• 2018

A vortex tube is a simple energy separating device that splits a compressed air stream into a cold and hot stream without any external energy supply or chemical reactions. The efforts of many researchers and designers have been focused on improvement of vortex tube efficiency by changing the parameters affecting vortex tube operation. The effective parameters are nozzle specifications and inflow pressure conditions. Effects of different nozzle cross-sectional area and number of nozzles are evaluated by computational fluid dynamics (CFD) analysis. In this study, CFD analysis of 3-D steady state and turbulent flow through a vortex tube was performed. We investigated the cold air mass flow rate, the cold air temperature, and the cold air heat transfer rate behavior of a vortex tube by utilizing seven straight nozzles and four inflow pressure conditions.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.237-238
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• 2014

A correlation between an air inflow velocity and $NO_x$ emission is investigated numerically. The area of a swirl premixed burner is controlled geometrically to increase or decrease an air inflow velocity. When an air velocity increases, mixedness at the burner exit is improved and NO emission at the liner exit is reduced. Although the area of an air slit is the same, NO emission shows discrepancy due to difference of air slit shapes.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.506-513
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• 2008

The engine containing a radical injector has been studied to improve the performances of efficiency and to reduce the exhaust emissions recently. The engine is far different from general compression ignition engines or spark ignition engines for the concept of combustion process. The inflow characteristic from main chamber into radical chamber during compression stroke is important because the radical chamber must have enough fresh air to generate appropriate radicals. The numerical simulation is performed in each specific shape and the engine speed by using KIVA code. The result shows that the fresh air inflow from main chamber into the radical chamber is the best at 45 degree of the hole angle.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.3
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• pp.231-241
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• 1997

A tracer model was applied in the Far East Asia to investigate the dry deposition rates of air pollutants on Korean Peninsula originated from different countries including China and Japan. Wind direction was chosen to predict the maximum deposition rates and SO$_2$ was chosen as a tracer to estimate the source strength. Model simulation shows that inflow, deposition and airborne ratios of China-originated SO$_2$ were 50%, 8% and 30%, respectively, at most. Also it was found that deposition, outbounded and airborne ratios of Korea-originated SO$_2$ were 15~77%, 8~75%, and 3~30%, respectively Model simulation also shows that inflow, deposition and airborne ratios of Kyushu-originated SO$_2$ were, 30~45%, 8~14％ and 20~25%, respectively. This study shows that tracer model can be applied on the estimation of air pollutants partitioning in regional scale and that more sophisticated modules and schemes can be developed and applied to better predict the transboundary amounts of air pollutants in this region.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.7
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• pp.592-598
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• 2002

The characteristics of a pulsating flow field from a heated block representing heat-dissipating electronic component in a channel have been numerically investigated. At the channel inlet a pulsating sinusoidal flow is imposed. The Reynolds number based on the channel height (H) is fixed at Re=500, and the forcing frequency is varied in the range of $0\leqSt\leq2$. Numerical results on the time-dependent flow field are obtained and averaged over a cycle of pulsation. The effect of the important governing parameters such as the Strouhal number is investigated in detail. The results indicate that the recirculating flow behind the block is substantially affected by the pulsation frequency. To characterize the periodic vortex shedding due to the inflow pulsation, numerical flow visualizations are carried out.

• Solar Energy
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• v.9 no.1
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• pp.62-69
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• 1989

This analysis is to investigate the influence of inflow angle when cooling air flows into PC (Printed Circuit) board channels. Flow between PC board channels with heat generating blocks is assumed laminar, incompressible, two-dimensional. Geometric parameters (block spacing (S), block height (H), block width (W) and channel height (L)) are held fixed. Inflow angle variations are $-10^{\circ},\;0^{\circ},\;10^{\circ}$, where uniform heat flux per unit axial length Q (W/m) from heated block surfaces is generated. The governing equations for velocity and temperature are solved by SIMPLE (Semi-Implicit Method Pressure for Linked Equation) algorithm. Nusselt number on each block surfaces is analyzed after a numerical calculation result. The result shows that the assumption on parallel inflow (inflow angle to channel, $0^{\circ}$) to PC board channels can be used without large error even when inflow' angle is varied.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.44 no.12
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• pp.94-97
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• 2015

• Journal of Korea Water Resources Association
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• v.52 no.4
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• pp.235-243
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• 2019

Recently, urban inundation was frequently occurred due to the intensive rainfall exceeding marginal capacity of the flood control facility. Furthermore, needs for the underground storage facilities to mitigate urban flood are increasing according to rapidly accelerating urbanization. Thus, in this study, drainage efficiency in drain tunnel connecting to underground storage was investigated from the air-core measurements in the drop shaft against two types of inlet structure. In case of the spiral inlet, the multi-stage structure is introduced at the bottom of the inlet to improve the vortex induction effect at low inflow discharge (multi-stage spiral inlet). The average cross-sectional area of the air-core in the multi-stage spiral inlet is 10% larger than the tangential inlet, and show the highly air emission effect and the highly inflow efficiency at the high inflow discharge. In case of the tangential inlets, the air emission effect decreased after exceeding the maximum inflow discharge, which is required to maintain the inherent performance of the tangential inlet. From the measurements, the empirical formula for the cross-sectional area of the air-core according to locations inside the drop shaft was proposed in order to provide the experimental data available for the inlet model used in experiments.

• KIEAE Journal
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• v.4 no.3
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• pp.87-94
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• 2004

The purpose of this study is to improve thermal environment of telecommunication equipment rooms that hold TDX-10, TDX-100, 5ESS-2000, PCM of the latest telecommunication equipment. Analysis program is used the commercial CFD code, Star-CD and DOE-2.1E. The result has been compared by the energy consumption and the temperature contour at the 1 m height of room for each case. Different methods such as the relocation of the existing air-conditioner, the inflow of the ambient air into room, the installation of the forced fan and the cooling system equipment of the duct-connection type have been used to test for improvement of thermal environment. The analysis shows that most efficient method is the inflow of the ambient air into room but auxiliary equipment should be needed to prevent the local thermal spot.