• Nuclear Engineering and Technology
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• 제50권6호
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• pp.842-848
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• 2018

Motivated by reducing the uncertainties in quantification of debris bed coolability, this paper reports an experimental study on two-phase flow resistances and interfacial drag in packed porous beds. The experiments are performed on the DEBECO-LT (DEbris BEd COolability-Low Temperature) test facility which is constructed to investigate the adiabatic single and two phase flow in porous beds. The pressure drops are measured when air-water two phase flow passes through the porous beds packed with different size particles, and the effects of interfacial drag are studied especially. The results show that, for two phase flow through the beds packed with small size particles such as 1.5 mm and 2 mm spheres, the contribution of interfacial drag to the pressure drops is weak and ignorable, while the significant effects are conducted on the pressure drops of the beds with bigger size particles like 3 mm and 6 mm spheres, where the interfacial drag in beds with larger particles will result in a descent-ascent tendency in the pressure drop curves along with the fluid velocity, and the effect of interfacial drag should be considered in the debris coolability analysis models for beds with bigger size particles.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2491-2498
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• 2020

The paper concentrates on an experimental study of the pressure drop in double-layered packed beds formed by glass spheres, having the configuration of horizontal and vertical stratification. Both single-phase and two-phase flow tests are performed. The pressure drop during the test is recorded and the measured data are compared with those of homogeneous beds consisting of mono-size particles. The results show that for the horizontally stratified bed with fine particles atop coarse particles, the pressure drop in top layer is found higher than those of homogenous bed consisting of the same smaller size particles, while the measured pressure drop of bottom part is similar with those of similar homogenous bed. But for the homologous bed with upside-down structure, the stratification has little or no effect on the pressure drop of the horizontally stratified bed, and the pressure drop of each layer is almost same as that of homogeneous bed packed with corresponding spheres. Additionally, in vertically stratified bed, the pressure drops on the left and right side is almost equal and between those in homogeneous beds. It is speculated that vertically stratified structure may lead to lateral flow which redistributes the flow rate in different parts of packed bed.

• 한국화재소방학회논문지
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• 제22권2호
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• pp.121-128
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• 2008

화재에 의한 흡입연기의 중장기 인체 유해성은 흡입연기가 폐에 침착되는 양과 밀접한 관련이 있다. 연기의 폐 내 침착량을 구하기 위해서는 인체 실험이 불가능한 만큼 폐모델을 이용한 실험이 필요하나 실제 폐형태에서 나타나는 연속적으로 감소되는 분지관의 제작상 어려움으로 인하여 하위 세대에서는 모델실험을 통한 침착 연구가 힘들다. 본 문제를 해결하기 위하여 이 연구에서는 아래로 갈수록 직경이 단계적으로 감소하는 구형 충전층을 이용한 폐모델을 개발하고 이를 폐침착 실험에 적용하였다. 실험장치는 각 입자크기별 호흡 패턴 변화에 따른 입자의 침착량을 측정하도록 구성되었으며 표준입자에 대한 실험 값을 실제 폐에 대한 결과와 비교함으로써 개발된 폐모델의 타당성을 검증하였다. 이 폐모델은 화재시 발생하는 여러 가지 연기입자의 흡입에 의한 인체 피해 연구에 도움이 될 것으로 생각된다.

• Journal of Biosystems Engineering
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• 제11권2호
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• pp.55-65
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• 1986

The resistance to the passage of airflow through various agricultural products is an important consideration in the design of an aeration or drying system. The amount of resistance to airflow varied widely from one kind of grain to another, and depended upon airflow rate, surface texture and shape of the particles, the size and configuration of voids, and foreign and fine material in the grain bed. The airflow rate was the major factor considered on this kind of study in the early stages. But these days, the studies on the resistance to airflow of grain affected by grain moisture content and foreign and fine material have been widely carried out. However the foreign an fine material in the grain bed could not be a major factor on the study in Korea because there were only a few grain process procedure after harvesting it. The objectives of this study were to investigate the effect of moisture content and airflow rate on airflow resistance to grain, and to develop a model to predict the static pressure drop across the grain bed as a function of moisture content and airflow rate. The rough rice varieties, Akibare, Milyang 15 (Japonica types), Samkwang, Backyang (Indica types)and covered barley variety, Olbori, which were harvested in 1985 were used in the experiment after cleaning them. Resistances to airflow of grain were investigated at four levels of moisture content (13-25%, wb.) for ten different airflow rates($0.01-0.15m^3/sm^2$). The results of this study are summarized as follows; 1. Theaverage bulk densities were $585.3kg/m^3$ for rough rice and $691.6kg/m^3$ for barley at the loose fill, and were $648.8kg/m^3$ for rough rice and $758.2kg/m^3$ for barley at the packed fill. The pressure drops at the packed fill beds were approximately 1.4 to 1.8 times higher than those at the loose fill beds. 2. The pressure drops across grain beds deceased with the increase of moisture content and increased with airflow rate. The decreasing rates of pressure drop across grain beds according to the moisture contents at the lower airflow rates were higher than those at the higher airflow rates, and the increasing rates of pressure drop according to the airflow rates at the lower moisture contents were higher those at higher moisture contents. 3. The pressure drop across barley bed were much higher than rough rice beds and the pressure drops across Japonica type rough rice beds were a little higher than Indica type. 4. The mathematical models to predict the pressure drop across grain beds as a function of moisture content and airflow rate were developed from these experiments.

• Journal of Biosystems Engineering
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• 제21권1호
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• pp.44-51
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• 1996

The purpose of this paper is to obtain the basic data for design of pressure cooling system. Static pressure drop, as a function of superficial velocity, was measured for different stacking methods and stacking heights of some fruits and vegetables. At given superficial velocity, sphericity and void fraction had a much greater influence on static pressure drop than average diameter of spherical fruits such as apple, peach, tomato and kiwi fruit. Among cylindrical vegetables such as cucumber, carrot, radish and chinese cabbage, cucumber showed different pattern of static pressure drop because of its bended shape, radish showed less static pressure drop than other vegetables because its large sizes of voids. When cucumber and spinach were stacked vertically and horizontally to air flow, a much greater static pressure drop was shown in vertical than in horizontal type, therefore static pressure drop was affected not only by void fraction but also by void shape. Also, in packed-beds of fruits and vegetables, static pressure drop could be estimated very well by Ramsins equation.

• KSBB Journal
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• 제14권1호
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• pp.124-130
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• 1999

아적장에서의 석탄의 탈황 가능성을 조사하기 위하여 Thiobacllus ferrooxidans를 이용한 탈황특성을 연구하였다. 배지의 배수를 고려할 때 야적장에서 미생물 탈황공정을 적용하기 위해서는 석탄입자 크기가 1mm 이상이어야 하고, 균일한 입자분포가 요구됨을 확인하였다. 1~2mm의 입자층과 2~4mm의 입자층에서의 약 70일 동안에 24%와 42%의 pyrite를 제거할 수 있었다. 두 석탄 입자층의 탈황속도는 각락 248mg S/kg coal.day (5,638mg S/kg pyritic-S.day)와 803mg S/kg coal.day(6,805mg S/kg pyritic-S,day)로 현탁배양의 약 15~25%로 낮았다. 석탄층에 액체배지를 순환하지 않고 단지 T.ferrooxidans의 접종만으로도 석탄의 표층부에서는 탈황이 가능하였다. 석탄을 야적장 등에 장기간 보관하는 동안에 고유황 석탄으로부터 미생물 탈황공정을 응용하여 부분적인 pyritic sulfur의 제거가 가능한 것을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.45-50
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• 2014

A fully packed capillary electrochromatographic (CEC) microchip with an on-column micro-solid phase extraction (SPE) bed for the preconcentration and separation of organic analytes was prepared. A linear microchannel with monodisperse colloidal silica packing was formed on a cyclic olefinic copolymer microchip with two reservoirs on both ends. Silver-cemented silica packing frit structure was formed at the entrance of the microchannel by electroless plating treatment as a base layer. A gold coating was formed on it by reducing $Au^{3+}$ to gold with hydroxylamine. Finally micro-SPE bed was formed by self-assembly adsorption of 1-dodecanethiol on it. Micro-SPE beds were about 100-150 ${\mu}m$ long. Approximately $10^3$ fold sensitivity enhancements for Sulforhodamine B, and Fluorescein in nM concentration levels were possible with 80 s preconcentration. Basic extraction characteristics were studied.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.636-643
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• 2024

The coolability of the debris bed with a simulant of solidified corium is experimentally studied, focusing on the effects of the structure of the axial stratified debris bed on the dryout heat flux (DHF). DHF was obtained for the four structures with different particle sizes for the axial stratified debris bed under top flooding. The experimental results show that the dryout position of the axial stratified debris bed is formed at the stratified interface indicated by the temperature rise, and the DHF of the axial stratified bed is much lower than that of the homogeneous bed packed with the upper small particles. To predict the dryout heat flux of the stratified debris beds, by considering the properties of the mixed area, a one-dimensional dryout heat flux model of the porous medium is derived from a water and vapor momentum equation for porous medium, two-phase permeability modifications, interfacial drag, and the correlation between capillary pressure and liquid saturation and verified with the experimental data. The modified model can give reasonable results under different structures.

• Nuclear Engineering and Technology
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• 제37권5호
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• pp.401-422
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• 2005

We review here research and development progress achieved in US Plasma Chamber technology roughly over the last decade. In particular, we focus on two major programs carried out in the US: the APEX project (1998-2003) and the US ITER TBM activities (2003-present). The APEX project grew out of the US fusion program emphasis in the late 1990s on more fundamental science and innovation. APEX was commissioned to investigate novel technology concepts for achieving high power density and high temperature reactor coolants. In particular, the idea of liquid walls and the related research is described here, with some detailed examples of liquid metal and molten salt magnetohydrodynamic and free surface effects on flow control and heat transfer. The ongoing US ITER Test Blanket Module (TBM) program is also described, where the current first wall/blanket concepts being considered are the dual coolant lead lithium concept and the solid breeder helium cooled concepts, both using ferritic steel structures. The research described for these concepts includes both thermofluid MHD issues for the liquid metal coolant in the DCLL, and thermomechanical issues for ceramic breeder packed pebble beds in the solid breeder concept. Finally, future directions for ongoing research in these areas are described.

• 한국산학기술학회논문지
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• 제12권6호
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• pp.2898-2903
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• 2011

휘발성 유기화합물인 저 농도의 MEK와 톨루엔을 사용하여 고정층 반응기에서 활성탄소섬유의 흡착 및 탈착특성을 조사하였다. 활성탄소섬유의 성능은 평형흡수량, 평형에 도달하는 시간, 그리고 탈착효율로 파악하였다. 다양한 실험을 통해 흡착공정에 있어 중요한 공정변수인 유입가스농도, 유량, 수분함량, 흡착제 주입량에 대한 영향을 연구하였다. 흡착층의 온도, 유량 그리고 유입가스농도가 증가할수록 파과시간이 감소하였다. 그리고 흡착제의 충전높이가 증가할수록 파과시간은 길어짐을 알 수 있었다. MEK와 톨루엔으로 흡착된 활성탄소섬유는 일정속도 가열과정을 통해 만족스럽게 재생되었으며 두 휘발성 유기화합물 중 MEK가 $150^{\circ}C$이하의 온도에서 훨씬 손쉽게 재생됨을 알 수 있었다.