• KSBB Journal
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• 제25권3호
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• pp.205-214
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• 2010

역류크로마토그래피 (counter-current chromatography, CCC)는 일련의 분배과정을 한 개의 튜브 내에서 연속적으로 일어나도록 고안된 시스템으로서 컬럼으로는 polytetrafluoroethylene(PTFE) 튜브가 다층으로 감겨있는 원통형의 홀더 3개가 서로 기어를 통해 물려있으며, 홀더가 회전과 공전을 통해 튜브의 꼬임을 방지하는 rotary seal-free flow centrifuge 시스템으로 되어있다. 역상 HPLC (reverse phase HPLC)에서는 고정상이 실리카에 결합된 유기물단 (organic moiety)이 수용성 이동상 물질에 의해서 용매화 (solvated)되는 반면 CCC는 실리카 대신에 강한 중력장에 의해 분리되는 자유로운 용매가 고정상이 되며 이 고정상의 부피비율은 20-30%에 이른다. 즉 고체담체에 결합된 유기관능기 대신에 물과 섞이지 않는 hexane 같은 유기용제가 고정상으로 사용되는 것이다. 고속역류크로마토그래피 (high-performance countercurrent chromatography, HPCCC)는 CCC의 기능을 향상시킨 분리시스템으로서 높은 중력장하에서 높은 이동상 속도와 높은 분리효율과 짧은 분리시간을 특징으로 하고 있다. 특히 mg 단위에서 kg 단위로의 스케일업이 선형적으로 가능하다는 큰 장점을 지니고 있다. 이 총설에서는 현재까지 개발된 CCC의 일반적인 이론을 간략히 정리하고 최신 HPCCC 장비의 적용 예를 살펴보고 그 응용분야로서 생리활성물질의 분리 및 정제와 관련된 연구동향을 정리하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.127-130
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• 2004

In this study, three-dimensional numerical calculations are peformed to simulate the flow and heat transfer in helically coiled tube steam generator employing a commercial CFD (Computational Fluid Dynamics) code. The problem considered herein includes the boiling phase change flow of tube side fluid and the single-phase counter-current flow of shell side hot fluid transferring heat to the tube side flow thru the tube wall. Detailed investigations are performed for both shell-side and tube-side flow fields in terms of density and volume fractions of each phase of fluids as well as for the tube wall heat transfer field in terms of heat transfer coefficients.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.886-892
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• 2024

The cladding temperatures and axial mass distribution computed by MAAP5 were compared with their measured values in the test bundle of the Phebus Test FPT0. The computed cladding temperatures were in good agreed with the measured values in the pre-transient phase. In the transient heat-up phase, the computed temperatures were overestimated by the Baker-Just correlation in MAAP5, but the computed temperatures could simulate the subsequently measured values. The computed mass distribution in the axial direction was in qualitative agreement with the measured one for post-test fuel damage observations. The calculated flow areas of inner and outer regions in the test bundle were compared with the photographic observations. MAAP5 computed them at the height of 0.2 m where the molten pool formed was in qualitative agreement with the photographic observations. It was found that the remaining steam flow paths might be caused by the gas-liquid two-phase flow counter-current flow limitation.

• 설비공학논문집
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• 제12권1호
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• pp.102-111
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• 2000

A numerical model which simulates the simultaneous heat and mass transfer within a vertical tube GAX absorber was developed. The ammonia vapor and the solution liquid are in counter-current flow, and the hydronic fluid flows counter to the solution liquid. The film thickness and the velocity distribution of the liquid film were obtained by matching the shear stress at the liquid-vapor interface. Two-dimensional diffusion and energy equations were solved in the liquid film to give the temperature and concentration, and a modified Colburn-Drew analysis was used for the vapor phase to determine the heat and mass fluxes at the liquid-vapor interface. The model was applied to a GAX absorber to investigate the absorption rates, temperature and concentration profiles, and mass flow rates of liquid and vapor phases. It was shown that the mass flux of water was negligible compared with that of ammonia except the region near the liquid inlet. Ammonia absorption rate increases rapidly near the liquid inlet and decrease slowly. Both the absorption rate of ammonia vapor and the desorption rate of water near the liquid inlet increase as the vapor mass flow rate increases, but the mass fluxes of the ammonia and the water near the liquid outlet decrease as the mass flow rate of the vapor increases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.795-800
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• 2000

A CCFL(Counter Current Flow Limit) test have been performed in narrow annular gaps with large diameter, because it has been confirmed that the CCFL phenomena affected the critical power in hemispherical narrow gap geometries from the SONATA(Simulation Of Naturally Arrested Thermal Attack)-IV (In-Vessel)/VISU(Visualization)-II experiments. The objectives of the CCFL experiments are to investigate the small gap sizes(1, 2mm) effect on CCFL under the large diameter condition and to confirm the findings of the VISU-II study that global dryout in hemispherical narrow gaps was induced by the CCFL. The test section was made of acrylic resin to allow visual observation on the two-phase flow behaviors inside annular gaps. It was observed from visualization that a part of water supplied was accumulated in the upper plenum and a significant increase in the differential pressure across the gap was occurred, which was the definition of the CCFL occurrence in this experimental study. From the experimental results in annular gap with large diameter it can be known that an increase in the differential pressure was not big at small air flow-rates. When the CCFL was occurred, the differential pressure across gaps was increased significantly and a water accumulated in the upper plenum. The occurrence of CCFL was correlated using the Wallis parameter.

• 한국수소및신에너지학회논문집
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• 제21권3호
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• pp.158-166
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• 2010

The purification of two liquid phases ($H_2SO_4$ phase and HIx phase) formed from a Bunsen reaction in Sulfur-Iodine (SI) hydrogen production process was investigated in order to operate SI process efficiently. The each synthetic solution for two liquid phases contained impurities was prepared on the basis of a proper composition obtained from Bunsen reaction. The purification of each solution was performed by counter-current flow using a packed column at different temperatures and $N_2$ flow rates. As the results of purification, impurities existed in each phase were decreased with increasing the temperature and the $N_2$ flow rate. In particular, the increase of the $N_2$ flow rate at the lower temperatures was effective to remove impurities by a reverse Bunsen reaction without side reactions. On the whole, it may be concluded that the purification of each phase is accomplished by mixing effects of the stripping, the evaporation, and the reverse Bunsen reaction.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.100.3-100
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• 2001

This article deals with the development of a mathematical model for the finishing polycarbonate polymerization process using a horizontal rotating disk-ring reactor with counter-current gas sweeping and the performance analysis of the reactor system by using the model. Here we intend to propose a model describing the reactor system consisting of two phases, in which by-product phenol is removed from the polymer of high molecular weight compatible with the products of commercial grades. The vapor phase is represented by a tanks-ln-series model while the polymer melt phase is regarded as a plug flow reactor.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.447-452
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• 2001

Quenching phenomena of hemispherical downward facing convex surfaces with narrow gaps have been investigated experimentally. Experiments employed test sections having 1 and 2 mm in gap thickness and 1 atm in system pressure. From interpretations of the temperature and the heat flux history, it was found that the flooding inside the gap was restricted by CCFL phenomena and quenching process was propagated from lower to upper region of the internal copper shell. The ratio of the maximum heat fluxes at 1 mm to 2mm in gap thickness was the almost same that obtained by steady state experiments. The quenching scenario of the hemispherical downward facing surface with narrow gap has been suggested.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.235-240
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• 2001

The CHFG (Critical Heat Flux in Gap) test results have been evaluated to quantify the critical power in hemispherical narrow gaps and a new correlation has been developed. The CHFG test results have shown that increases in the gap thickness and pressure lead to an increase in critical power. The pressure effect on the critical power was found to be much milder than predictions by CHF correlations of other researches. From the CHFG test results, a new correlation on critical power in the hemispherical gap has been developed using the non-dimensional parameters as follows: $$\frac{qCHF}{{\rho}g^hfg}{\cdot}4\sqrt{\frac{{\rho}_g^2}{g{\sigma}{\Delta}{\rho}}=\frac{0.1042}{1+0.1375({\rho}g/{\rho}l)^{0.21}(D/s)}$$ The developed correlation has been expanded to apply the spherical geometry using the Siemens/KWU's correlation.