• Bulletin of the Korean Chemical Society
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• 제18권6호
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• pp.584-588
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• 1997

A new device to accurately deliver small amount of modifier into supercritical carbon dioxide fluid is described. Carbon dioxide, the most widely used mobile phase in supercritical fluid chromatography, is a relatively non-polar fluid, and hence the addition of small amount of polar modifiers could be necessary to migrate polar solutes. In this work, supercritical CO₂and modifier are delivered from the pump to a 100 μL mixing chamber in which a small magnetic bar is rotating. After passing through the mixing chamber, supercritical CO₂is changed to a new mobile phase with different polarity. The amount of modifier added into supercritical CO₂is measured by an amperometric microsensor, which is prepared from a thin film of perfluorosulfonate ionomer.

• 대한화장품학회지
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• 제34권3호
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• pp.209-215
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• 2008

화장품, 의약품에서 항비듬제로 널리 사용되는 요도프로피닐 부틸카바메이트와 클림바졸을 초임계 유체를 이용하여 미세입자를 제조하였다. 초임계 유체로는 임계온도와 임계압력이 상대적으로 낮은 이산화탄소가 사용되었다. 초임계 이산탄소에 용해력이 있는 요도프로피닐 부틸카마메이트와 클림바졸을 항비듬제로 선택되었다. 초임계 용액 급속팽창법을 이용하여 압력과 온도를 변화시켜 입자크기와 형상에 미치는 영향을 분석하였다.

• 대한기계학회논문집B
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• 제32권2호
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• pp.158-165
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• 2008

The carbon dioxide properties change sharply near the critical or pseudo-critical point in the heat transfer processes. The reduction in turbulent, convective heat transfer parameters observed in some supercritical data and in experiments with common gases can be due to property variation, acceleration, buoyancy or combinations of these phenomena, depending on the conditions of the applications. In this study, the measurement for the secondary flow driven by buoyancy was carried out on the supercritical carbon dioxide turbulent flows in the different boundary condition with the constant mass flow rate. The available measuring techniques were used to clarify the behaviour of any supercritical fluid. Laser Doppler Velocimeter (LDV) and a special device was used to measure the secondary velocity and turbulent characteristics of the supercritical flows.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2011년도 춘계학술논문집 1부
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• pp.489-492
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• 2011

Supercritical fluid technology has been an alternative for purification and separation of biological compounds in cosmetic, food, and pharmaceutical products. Solubility information of biological compounds in supercritical fluids is essential for choosing a supercritical fluid processes. The equilibrium solubility of hinokitiol was measured in supercritical carbon dioxide with a static method in the pressure range from 8 to 40 MPa and at temperatures equal to 313.2, 323.2 and 333.2 K. The experimental data were correlated well by Peng.Robinson equation of state and quasi-chemical nonrandom lattice fluid model.

• Fibers and Polymers
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• 제6권4호
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• pp.284-288
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• 2005

Poly(ethylene terephthalate) was annealed at different temperature and pressure of supercritical carbon dioxide $(CO_2)$ using samples quenched from the melt. Crystallization and molecular relaxation behavior due to $CO_2-annealing$ of samples were investigated using differential scanning calorimetric and dynamic mechanical measurements. The glass transition and crystallization temperatures significantly decreased with increasing temperature and pressure of $CO_2$. The dynamic mechanical measurement of samples annealed at $150^{\circ}C$ in supercritical $CO_2$ showed three relaxation peaks, corresponding to existence of different amorphous regimes such as rigid, intermediate, and mobile domains. As a result, the mobile chains were likely to facilitate crystallization in supercritical state. It also led to the decreased modulus of $CO_2-annealed$ samples with increasing pressure.

• 한국식품과학회지
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• 제23권6호
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• pp.677-682
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• 1991

초임계 탄산가스를 추출용매로 사용하여 대두유를 추출하였다. 추출압력과 온도의 범위는 각각 3,000-7,000psig와 $40-70^{\circ}C$였다. 1g의 대두유를 추출하기 위하여 7,000psig, $60^{\circ}C$에서는 25l의 탄산가스가 필요하였으나, 3,000psig, $60^{\circ}C$에서는 250l가 소요되었다. 추출압력 6,000 psig 미만에서는 온도가 증가할수록 추출율이 감소하였고, 6,000psig에서는 온도에 관계없이 추출율이 일정한 반면, 6,000psig를 넘어서는 온도가 증가할수록 추출율도 증가하였다. 초임계탄산가스로 추출된 대유는 핵산으로 추출한 대우유보다 색도가 약하였으며 인지질의 함량도 매우 적었다. 지방산조정은 초임계 추출이 진행됨에 따라 변화하였다. 초임계탄산가스를 이용하여 대두유를 추출할 경우, 신속한 추출이 이루어지며, 탈검과 탈색의 정제공정을 삭제내지는 축소하여 정제유를 만들 수 있다.

• Journal of Microbiology and Biotechnology
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• 제19권12호
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• pp.1596-1602
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• 2009

A lipase-catalyzed esterification reaction of (S)-naproxen ethyl ester by CALB (Candida antarctica lipase B) enzyme was performed in supercritical carbon dioxide. Experiments were performed in a high-pressure cell for 10 h at a stirring rate of 150 rpm over a temperature range of 313.15 to 333.15 K and a pressure range of 50 to 175 bar. The productivity of (S)-naproxen ethyl ester was compared with the result in ambient condition. The total reaction time and conversion yields of the catalyzed reaction in supercritical carbon dioxide were compared with those at ambient temperature and pressure. The experimental results show that the conversion and reaction rate were significantly improved at critical condition. The maximum conversion yield was 9.9% (216 h) at ambient condition and 68.9% (3 h) in supercritical state. The effects of varying amounts of enzyme and water were also examined and the optimum condition was found (7 g of enzyme and 2% water content).

• KSBB Journal
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• 제22권5호
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• pp.336-340
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• 2007

초임계 이산화탄소를 이용하여 커피의 악취 성분을 제거하였고, 탈취된 커피로부터 에스프레소 방식으로 커피음료를 만들어 대조군과 제거 효율을 비교하였다. 커피의 대표적인 다섯 가지 악취 성분을 대상으로 GC를 이용하여 분석하고 탈취 효율을 측정하였다. 초임계 이산화탄소는 압력과 온도의 영향을 받아 밀도와 용해도가 변화하고 이로써 용해력이 변화하기 때문에, 압력과 온도의 최적화 실험을 하였고 그 결과 350 bar, 70$^{\circ}C$의 조건에서 커피 악취 성분이 최대로 제거됨을 알 수 있었다. 탈취된 커피 분말로부터 에스프레소 방식으로 추출된 커피 음료의 향 성분을 변형된 헤드스페이스법으로 수거하여 분석하였다. 그 결과 초임계 탈취 (deodorized)된 커피 분말에서 발생된 악취 성분은 탈취하지 않은 커피 분말에서 발생된 악취 성분보다 총 73% 감소한 것을 확인할 수 있었다.

• 한국표면공학회지
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• 제37권6호
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• pp.344-349
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• 2004

Emulsions were formed through putting small quantity of nickel electroplating solution into supercritical carbon dioxide, and then electroplating in the $sc-CO_2$ emulsions was conducted. It is an environmental-friendly technology that can solve the treatment of a large quantity of toxic plating wastewater, which is a big problem in the existing wet plating, and also can reduce secondary waste generation fundamentally. Supercritical carbon dioxide emulsions enhanced by ultrasonic horn were formed by non-ionic surfactant and nickel solution. Plating condition within emulsions was set up as 120bar and $55^{\circ}C$ through measurement of electrical conductivity following the pressure change. Experiments were conducted respectively against supercritical carbon dioxide emulsions electroplating and general chemical electroplating, and then their results were compared and analyzed. As the experiment result utilizing emulsions, plating surface was formed very evenly even with a small quantity of electroplating solution, and fine particles were plated compactly without any pinhole or crack due to hydrogenation, which occurs in general electroplating. Used electroplating solution can be reused through recovery process. Therefore, this technology will be able to be applied as new clean technology in electro-plating.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3540-3550
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• 2022

The supercritical carbon dioxide (S-CO₂) Brayton cycle is an important energy conversion technology for the fourth generation of nuclear energy. Since the printed circuit heat exchanger (PCHE) used in the S-CO₂ Brayton cycle has narrow channels, Rayleigh-Bénard (RB) convection is likely to exist in the tiny channels. However, there are very few studies on RB convection in supercritical fluids. Current research on RB convection mainly focuses on conventional fluids such as water and air that meet the Boussinesq assumption. It is necessary to study non-Boussinesq fluids. PRB convection refers to RB convection that is affected by horizontal incoming flow. In this paper, the computational fluid dynamics simulation method is used to study the PRB convection phenomenon of non-Boussinesq fluid-supercritical carbon dioxide. The result shows that the inlet Reynolds number (Re) of the horizontal incoming flow significantly affects the PRB convection. When the inlet Re remains unchanged, with the increase of Rayleigh number (Ra), the steady-state convective pattern of the fluid layer is shown in order: horizontal flow, local traveling wave, traveling wave convection. If Ra remains unchanged, as the inlet Re increases, three convection patterns of traveling wave convection, local traveling wave, and horizontal flow will appear in sequence. To characterize the relationship between traveling wave convection and horizontal incoming flow, this paper proposes the relationship between critical Reynolds number and relative Rayleigh number (r).