• Title, Summary, Keyword: supercritical carbon dioxide

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Development of a New Correlation for the Heat Transfer Coefficient of Turbulent Supercritical Carbon Dioxide Flow (초임계 상태 이산화탄소 난류유동의 새로운 열전달계수 상관식 개발)

  • 임홍영;최영돈;김용찬;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.4
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    • pp.274-286
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    • 2003
  • Numerical simulations are performed to investigate the turbulent convective heat transfer of the supercritical carbon dioxide flows in vertical and horizontal square ducts. The gas cooling process at the supercritical state experiences a sudden change in thermodynamic and transport properties. This results in the extraordinary variations of the heat transfer coefficients in the supercritical state, which are much different from those of single or two phase flows. Algebraic second moment closure which can include the effects of large thermophysical property variations of carbon dioxide and of buoyancy is employed to model the Reynolds stresses and turbulent heat fluxes in the governing equations. The previous correlations for the turbulent heat transfer coefficient for the supercritical carbon dioxide flows couldn't reflect the buoyancy effect. The present results are used to establish a new heat transfer coefficient correlation including the effects of large thermophysical property variation and buoyancy on in-duct cooling process of supercritical carbon dioxide.

New Device for Addition of Modifier to Supercritical Fluid Carbon Dioxide Mobile Phase

  • 표동진;김호현
    • Bulletin of the Korean Chemical Society
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    • v.18 no.6
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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.

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Hydrolysis of Starch by $\alpha$-Amylase and Glucoamylase in Supercritical Carbon Dioxide

  • CHUL KIM;LEE, HYEON SUP;YEON WOO RYU
    • Journal of Microbiology and Biotechnology
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    • v.4 no.3
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    • pp.230-232
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    • 1994
  • The enzymes $\alpha$-amylase and glucoamylase used in starch hydrolysis were found active in the supercritical carbon dioxide solvent Higher hydrolysis of starch sluny in supercritical $CO_2$ was achieved by operating the reactor for the first two hours with $\alpha$ -amylase and to subsequent addition of glucoamylase for continued hydrolysis.

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Ethanol Modified Supercritical$CO_2$ Extraction of Daidzein from Soybean (에탄올 보조용매 초임계$CO_2$를 이용한 대두 Daidzein 추출)

  • 부성준;변상요
    • KSBB Journal
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    • v.16 no.1
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    • pp.95-98
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    • 2001
  • Various factors affecting the supercritical carbon dioxide extraction of daidzein from soybean were studied. Daidzein was not extracted with pure supercritical carbon dioxide. The ethanol was an efficient modifier for supercritical carbon dioxide to extract daidzein. The extraction efficiency increased as the pressure increased up to 300 bar. At $35^{\circ}C$ and 300 bar, 93% of daidzein was extracted with supercritical carbon dioxide modified with 15% of ethanol.

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Research on the Development of the Supercritical CO2 Dual Brayton Cycle (초임계 이산화탄소 이중 브레이튼 사이클 개발 연구)

  • Baik, Young-Jin;Na, Sun Ik;Cho, Junhyun;Shin, Hyung-Ki;Lee, Gilbong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.10
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    • pp.673-679
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    • 2016
  • Because of the growing interest in supercritical carbon dioxide power cycle technology owing to its potential enhancement in compactness and efficiency, supercritical carbon dioxide cycles have been studied in the fields of nuclear power, concentrated solar power (CSP), and fossil fuel power generation. This study introduces the current status of the research project on the supercritical carbon dioxide power cycle by Korea Institute of Energy Research (KIER). During the first phase of the project, the un-recuperated supercritical Brayton cycle test loop was built and tested. In phase two, researchers are designing and building a supercritical carbon dioxide dual Brayton cycle, which utilizes two turbines and two recuperators. Under the simulation condition considered in this study, it was confirmed that the design parameter has an optimal value for maximizing the net power in the supercritical carbon dioxide dual cycle.

Manufacturing Polymer/clay Nanocomposites Using a Supercritical Fluid Process

  • Jung, Hyun-Taek;Yoon, Ho-Gyu;Lim, Soon-Ho
    • International Journal of Precision Engineering and Manufacturing
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    • v.9 no.4
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    • pp.63-65
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    • 2008
  • The increased interest in reducing the environmental effects caused by releasing organic compounds and aqueous waste has motivated the development of polymeric materials in supercritical fluids. Recently, supercritical fluids have been used in material synthesis and processing because of their special properties, such as high diffusivity, low viscosity, and low surface tension. Supercritical carbon dioxide is the most attractive because it is non-toxic, non-flammable, and has moderate critical temperature and critical pressure values. Supercritical carbon dioxide can also swell most polymers. In this study, we prepared polymer/clay nanocomposites using supercritical fluids. Cloisites 10A, 15A, 25A, and 30B used in this study are montmorillonites modified with a quaternary ammonium salt. The nanocomposites of polymer/clay were characterized by X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry.

A Study on the Power Generation Using Supercritical Carbon Dioxide (초임계 이산화탄소를 활용한 발전에 대한 연구)

  • NOH, SANGGYUN
    • Transactions of the Korean hydrogen and new energy society
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    • v.30 no.4
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    • pp.297-302
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    • 2019
  • In this paper, the power generation efficiency increase has been studied for a Rankine cycle using both supercritical carbon dioxide as a working fluid and LNG as a coolant with PRO/II with PROVISION release 10.0 from Aveva company. Peng-Robinson equation of the state model with Twu's alpha function was selected for the modeling of the power generation cycle using LNG cold heat. Power generation efficiency was increased from 24.82% to 57.76% when using LNG as a coolant for supercritical carbon dioxide power generation cycle.

The Activation of PPAR-α and Wnt/β-catenin by Luffa cylindrica Supercritical Carbon Dioxide Extract

  • Kim, Bora
    • Natural Product Sciences
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    • v.25 no.4
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    • pp.341-347
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    • 2019
  • Luffa cylindrica (LC) is a very fast-growing climber and its fruit have been considered as agricultural wastes. We conducted to check the comparative qualities of ethanol solvent extraction (LCE) and supercritical carbon dioxide extraction (LCS) of L. cylindrica fruit and seed. LCS had higher antioxidant and polyphenol contents than LCE. LCS were significantly increased peroxisome proliferator-activated receptor (PPAR)-a and involucrin expression as epidermal differentiation marker in 3D skin equivalent model. LCS also showed antimicrobial activity against Staphylococcus aureus, a causative bacteria in atopic dermatitis. In addition, LCS inhibited the adipocyte differentiation of 3T3-L1 cells. When treated with the extract at a concentration of 100 ㎍/mL, the Wnt/β-catenin pathway reporter luciferase activity of HEK 293-TOP cells was increased approximately by 2-folds compared to that of the untreated control group. These results indicate that L. cylindrica supercritical carbon dioxide extract may serve as a cosmeceutical for improving skin barrier function and the treatment of obesity.

The activation of PPAR-α and Wnt/β-catenin by Paeonia lactiflora root supercritical carbon dioxide extract

  • Kim, Bora
    • Journal of the Korean Applied Science and Technology
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    • v.36 no.4
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    • pp.1136-1142
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    • 2019
  • The root of Paeonia lactiflora has been used in Chinese medicine. We conducted to check the comparative qualities of ethanol solvent extraction (PLE) and supercritical carbon dioxide extraction (PLS) of P. lactiflora root. PLE had higher antioxidant and polyphenol contents than PLS. But, PLS were significantly increased peroxisome proliferator-activated receptor (PPAR)-α. In addition, PLS inhibited the adipocyte differentiation of 3T3-L1 cells. When treated with the extract at a concentration of 100 ㎍/mL, the Wnt/β-catenin pathway reporter luciferase activity of HEK 293-TOP cells increased approximately by 3-folds compared to that of the untreated control group. These results indicate that P. lactiflora supercritical carbon dioxide extract may serve as a cosmeceutical for improving skin barrier function and the treatment of obesity.

Experimental Studies on Heat Transfer and Pressure Drop Characteristics during Gas Cooling Process of Carbon Dioxide in the Supercritical Region (이산화탄소의 초임계 가스냉각 과정의 열전달 및 압력강하 특성에 관한 실험적 연구)

  • 윤석호;김주혁;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.6
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    • pp.538-545
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    • 2004
  • This paper presents the experimental data for the heat transfer and pressure drop characteristics obtained during the gas cooling process of carbon dioxide in a horizontal tube. The tube in which carbon dioxide flows is made of copper with an inner diameter of 7.73 mm. Experiments were conducted for various mass fluxes and inlet pressures of carbon dioxide. Mass fluxes are controlled at 225, 337 and 450 kg/$m^2$s and inlet pressures are adjust-ed from 7.5 to 8.8 ㎫. The experimental results in this study are compared with the existing correlations for the supercritical heat transfer coefficient, which generally under-predict the measured data. Pressure drop data agree very well with those calculated by the Blasius' equation. Based on the experimental data, a new empirical correlation to estimate the near-critical heat transfer coefficients has been developed.