• Resources Recycling
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• v.7 no.3
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• pp.42-51
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• 1998

Hydrogen in atmosphere can easily dissolve in melt of light metal alloys. Increasing demand for recycling of light metal a alloys has, therefore, focused attention on the removal of hydrogen gas, and alloy addition in melt has become an imporLant r refining process. For this purpose behaviors of mixing and hydrogen degassing in impeller agitated refming vessel with/without barnes were investigated. Flow patterns, mixing time behavior and kinetics of degassing in various agitating conditions were analysed in watet model experiments. And, numerical analysis on turbulent flow pattern in impeller agitated vessels was performed.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.113-126
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• 2021

In order to develop active cooling systems for a hypersonic cruise vehicle, a series of studies need to be preceded on regenerative cooling technologies by using endothermic reaction of liquid hydrocarbon aviation fuels. Among them, it is essential to scrutinize fluid flow/heat transfer/endothermic pyrolysis characteristics of supercritical hydrocarbons in a micro-channel, as well as to acquire thermophysical properties of hydrocarbon fuels in a wide range of temperature and pressure conditions. This study, therefore, reviewed those technologies and analyzed major findings in related research areas which have been carried out worldwide for the development of efficient operational regenerative cooling systems of a hypersonic flight vehicle.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.3
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• pp.43-53
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• 2022

In this study, analysis of the flow characteristics of pintle-controlled nozzle with split-line TVC system and the thrust performance prediction was performed. The numerical computation was verified by comparing the thrust coefficient derived from the analysis results with the experimental data. By applying the same numerical analysis technique, the flow characteristics of nozzle were confirmed according to operating altitude, pintle stroke position and TVC angle with the 1/10 scale. As the TVC angle increased, thrust loss occurred and the tendency of AF was different depending on the position of the pintle stroke. Based on the analysis results, the relation of thrust coefficient was derived by applying the response surface methods. The thrust performance model with a slight difference of 1.2% on average from the analysis result was generated.

• Geophysics and Geophysical Exploration
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• v.18 no.4
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• pp.223-231
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• 2015

Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finite-element-method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

• Journal of Energy Engineering
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• v.9 no.4
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• pp.348-357
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• 2000

본 연구에서는 동해화력 순환유동층 보일러와 유사한 3개의 사이클론을 갖는 직사각형 구조의 순환유동층 반응기를 이용하여 동해화력 운전조건 -연소로 공기 속도, 일-이차 공기비, 전체 고체량(inventory), 입도 및 입도분포 등- 에 따른 축방향 고체 체류량 및 순환량 등의 수력학적 특성을 고찰하였다. 상승관에서의 공기유속(U$_{0}$)이 증가함에 따라, 또는 PA/[PA+SA]비가 증가함에 따라, 그리고 전체 고체량(inventory)이 증가함에 따라 고채 채류량 및 순환량은 증가하는 것으로 나타났다. 또한 넓은 입도 분포를 갖는 석탄 회재의 경우는 균일한 입도 분포의 입자들에 비해 입자 비산량 및 고체 순환량이 작을 것으로 나타났다. 한편, 층내에서의 고체 체루량 분포를 감소지수 a 및 K를 사용하여 나타낼 수 있었으며, a 및 K와 유속 및 입자간의 상관 특성치를 도출하여 유동 및 순환특성을 고찰하였다. 상기의 상관수는 균일한 입도의 모래에 비해 석탄회재가 비교적 큰 값을 나타내었으며, 상관수가 클수록 희박상 영역에서의 비산 및 고체 순환량이 작은 것으로 나타났다.다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.7-7
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• 1998

액체 연료 분포의 균일성과 대칭성은 연소 효율을 높이고, 공해 물질을 줄이는데 있어서 필수적인 요소이기 때문에 분무 패턴을 정량적으로 해석하는 것은 매우 중요하다. 고전적으로 사용되고 있는 mechanical patternator는 ⅰ) 유동을 교란시키고, ⅱ) 공간 분해능이 떨어지며, ⅲ) 복잡한 재순환 유동이나 화학 반응이 있는 유동에서의 적용이 어렵다는 단점을 가지고 있다. 이러한 단점들을 극복하기 위하여 레이저를 이용한 optical patternator에 대한 연구가 진행되고 있다. Optical patternator는 유동을 교란시키지 않으면서 고해상도의 분무 패턴 측정을 할 수 있다. 형광 신호는 물질의 체적에 비례한다. 따라서, 레이저 평면광을 분무에 조사시켜 주어서 유도되는 형광 신호를 이용하는 평면액체 레이저 유도 형광법(PLLIF : Planar Liquid Laser Induced Fluorescence)은 분무패턴을 알아보는 매우 유용한 방법이다.

• Clean Technology
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• v.18 no.4
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• pp.398-403
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• 2012

Selective nitrification and granulation have been carried out in a pilot scale air-lift sequencing batch reactor (SBR) for stable and economical nitrogen removal from wastewater. The SBR showed about 100% nitrification efficiency up to 1.0 kg ${NH_4}^+-N/m^3{\cdot}d$, about 90% efficiency at 1.0-2.0 kg ${NH_4}^+-N/m^3{\cdot}d$, and it was less than 90% when the load was higher than 2.0 kg ${NH_4}^+-N/m^3{\cdot}d$. Nitrite accumulation was induced by selective inhibition of nitrite oxidizing bacteria by free ammonia inhibition and dissolved oxygen limitation. For the purpose, high nitrite ratio (> 0.95) was obtained by keeping the pH higher than 8.0 and dissolved oxygen lower than 1.5 mg/L. In addition, sludge granulation was achieved by keeping reactor settling time to 5 minutes to wash out poor settling sludge and to promote the growth of granulation sludge. The operation accelerated sludge granulation and the sludge volume index (SVI) decreased and stably maintained to less than 75 in 60 days.

• The KSFM Journal of Fluid Machinery
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• v.19 no.3
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• pp.10-13
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• 2016

The wet-air oxidation in gravity pressure reactor is effective for organic waste treatment with energy saving under high pressure and high temperature. But its oxidation control is difficulty because its multi-phase flow characteristics is very complicated. The flow characteristics of an oxidizer feed section in the gravity pressure reactor were investigated using numerical method which are verified by comparison with experimental results. In this study, the results showed that the flow rate of oxidizer have an effect on the generation of bubble around feed section.

• Journal of computational fluids engineering
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• v.15 no.1
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• pp.9-16
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• 2010

The characteristics of flow and heat transfer in a bubbling fluidized bed are investigated by means of computational fluid dynamics (CFD). To simulate two-phase flow for the gas and solid flows, Eulerian-Eulerian approach is applied. Attention is paid for a heat transfer from the wall to fluidized bed by bubbling motion of the flow. From the result, it is confirmed that heat transfer is promoted by chaotic bubbling motion of the flow by enhancement of mixing among solid particles. In particular, the vortical flow motion around gas bubble plays an important role for the mixing and consequent heat transfer. Discussion is made for the time and space averaged Nusselt number which shows peculiar characteristics corresponding to different flow regimes.

• Journal of the Korean Society of Visualization
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• v.8 no.3
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• pp.29-34
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• 2010

This paper proposes a design method to provide uniform flow in a microreactor. Uniform momentum approach is adopted with 10 pillars before and after the chamber having a different slope inlet channel. The slope and number of pillars are two factors to make a uniform flow in the microreactor, covering the hexagonal gold layer. The CFD analysis about the designed microreactor is carried out and the velocity vector field measurements are made in the fabricated microreactor by micro PIV technique. The uniformity of microreactor flow was confirmed by both numerical simulation and experimental results.