• Title/Summary/Keyword: Supercritical pressure

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The Study on the Spray Characteristics of Supercritical Spray (초임계상태 분무의 분무 특성에 관한 연구)

  • Park, C.J.
    • Journal of ILASS-Korea
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    • v.4 no.3
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    • pp.8-14
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    • 1999
  • The characteristics of the breakup process in supercritical spray is investigated during the injection of supercritical sulfur hexafluoride into dissimilar gases at supercritical pressures and subcritical temperature of the injected fluid. The visualization techniques used are backlighting and shadowgraph methods. The spray angles are measured and the breakup and mixing process are observed at near and supercritical conditions. The results show that spray angles are decreased with the in..ease of the ratio of density $(\frac{\rho_f}{\rho_g})$. At the supercritical temperature, the spray angles in atomization region are kept nearly constant such as the typical spray angle in gas injection. The mixing process is changed radically at the temperature where $\frac{d\rho}{dT}=\frac{1}{2}[\frac{d\rho}{dT}]_{max}$ at given pressure.

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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.

Effect of Dynamic SGS Model in a Kerosene-LOx Swirl Injector under Supercritical Condition

  • Heo, Jun-Young;Hong, Ji-Seok;Sung, Hong-Gye
    • International Journal of Aeronautical and Space Sciences
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    • v.16 no.2
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    • pp.254-263
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    • 2015
  • In this study, numerical simulations are carried out to investigate the dynamic SGS model effects in a Kerosene-LOx coaxial swirl injector under high pressure conditions. The turbulent model is based on large-eddy simulation (LES) with real-fluid transport and thermodynamics. To assess the effect of the dynamic subgrid-scale (SGS) model, the dynamic SGS model is compared with that of the algebraic SGS model. In a swirl injector under supercritical pressure, the characteristics of temporal pressure fluctuation and power spectral density (PSD) present comparable discrepancies dependant on the SGS models, which affect the mixing characteristics. Mixing efficiency and the probability density (PDF) function are conducted for a statistical description of the turbulent flow fields according to the SGS models. The back-scattering of turbulent kinetic energy is estimated in terms of the film thickness of the swirl injector.

Extraction of Acanthoside-D from Acanthopanax Cortex using Supercritical Carbon Dioxide (초임계 이산화탄소를 이용한 가시오갈피로부터 Acanthoside-D의 추출)

  • 양시중;신재순;강춘형
    • KSBB Journal
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    • v.19 no.4
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    • pp.284-287
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    • 2004
  • The purpose of this study was to find an optimum extraction condition of acanthoside-D from acanthopanax cortex with supercritical carbon dioxide as a solvent. In this effort, effects of the extraction conditions including pressure, temperature and presence or absence of a cosolvent on the extraction efficiency were investigated. The ethanol, water or 50% methanol was used as a cosolvent whilst the operating pressure ranged from 200 bar to 300 bar. The acanthoside-D concentrations were determined by means of HPLC equipped with a UV detector. From the results, it was observed that increase of higher pressure led to the higher extraction efficiency. Further, water was found to be the best cosolvent among the entrainers tested.

A Study on Optical Analysis of the Color Difference Caused by the Overprinting Sequence of Ink (잉크의 중첩인쇄순서에 기인하는 색차의 광학적 해석에 관한 연구)

  • 강상훈
    • Journal of the Korean Graphic Arts Communication Society
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    • v.16 no.1
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    • pp.39-53
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    • 1998
  • The extraction rate of ginger from Korean-grown ginger root with supercritical carbon dioxide was measured as a function of flow rate of supercritical carbon dioxide, particle size, temperature and pressure. the extraction rate increased as the particle size decreased due to a decrease in the diffusion path. The extraction rate were independent of flow rate of supercritical carbon dioxide in a plot of ginger oil yield versus extraction time. This indicated that the extraction process is controlled by intraparticle diffusion within a particle of ginger root. In the case of temperature and pressure effect, the experimental results showed that the extraction rate decreased with an increase in temperature and increased with an increase in pressure.

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Development of Dynamic Simulation Software for Power Plant and its Application to Once-Through Boiler (플랜트 동특성 해석용 소프트웨어 개발 및 초임계압 관류형 보일러에의 적용)

  • Lee, Ki-Hyun;Lee, Dong-Su;Cho, Chang-Ho
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.656-661
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    • 2000
  • In the recent trend of electric power supply market, a variable pressure operation supercritical once-through steam generator is highlighted as a thermal power plant for cycling load because of its superiority in load regulation. Almost all thermal power plants of the future are expected to be variable pressure operation supercritical once-through units. APESS(Advanced Plant Engineering & Simulation System) is a dynamic simulation software for power plant which is under being developed by Korea Heavy Industries & Construction Co., Ltd. This paper present the introduction of APESS and the result of simulation for variable pressure operation supercritical once-through steam generator.

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Supercritical Carbon Dioxide Extraction of Dried Egg Yolk (초임계 이산화탄소에 의한 난황분의 추출)

  • 임상빈;좌미경;고영환;유익종
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.26 no.5
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    • pp.860-865
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    • 1997
  • Investigations were performed on the effects of extraction temperature, pressure, time on solubility and selectivity of egg yolk lipid and cholesterol, and color and fatty acid composition of the residue in supercritical carbon dioxide(SC-Co$_2$) extraction. Lipid and cholesterol solubility increased as the increase of Co$_2$ density and was found to strongly depend on the extraction pressure rather than the extraction temperature. The relative concentration of cholesterol in the extract increased with an increase in temperature and decreased with an increase in pressure and extraction time. extraction of dried eg yolk for 3hr at 4$0^{\circ}C$/276 bar removed 46.1% of cholesterol from the residual egg yolk with a yield of 63.2%. SC-Co$_2$ extraction produced a lighter color egg yolk with less redness and yellowness. As the extraction time increased, the resultant residual egg yolk became more saturated with fatty acids. SC-$CO_2$ extraction offers a safe, natural method for removing cholesterol from dried egg yolk.

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Analysis for Local Structure of Gaseous Hydrogen/liquid Oxygen Flame at Supercritical Pressures (초임계 압력상태에서 기체수소/액체산소 국소화염구조 해석)

  • Kim, Tae-Hoon;Kim, Seong-Ku;Kim, Yong-Mo
    • Journal of ILASS-Korea
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    • v.15 no.4
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    • pp.182-188
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    • 2010
  • Significant real fluid behaviors including rapid property changes take place where high pressure combustion devices such as rocket engines. The flamelet model is the reliable approach to account for the real fluid effects. In the present study, the flamelet equations are extended to treat the general fluids over transcritical and supercritical states. The real fluid flamelet model is carried out for the gaseous hydrogen and cryogenic liquid oxygen flames at the wide range of thermodynamic conditions. Based on numerical results, the precise discussions are made for effects of real fluid, pressure, and differential diffusion on the local flame structure.

Color and Texture Changes of Dried Apple Slab After Supercritical Carbon Dioxide Pretreatment (초임계 이산화탄소 전처리에 따른 건조 사과절편의 색 및 물성변화)

  • Lee, Bo-Su;Lee, Won-Young
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.39 no.7
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    • pp.1018-1023
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    • 2010
  • This study was conducted to investigate quality changes of apple slab after pretreating with supercritical $CO_2$. L, a, b and color difference values were little changed at increasing temperature and pressure. Polyphenol oxidase was inhibited according to increment of supercritical $CO_2$ temperature and pressure. Springiness and hardness were increased at increasing pressure and temperature condition of pretreatment but hardness showed lower value than untreatment. The texture like sponge of dried apple slab was probably due to channels which were made during penetration and release of carbon dioxide.

Design of a Model Combustor for Studying the Combustion Characteristics of O2/H2 Flames at Supercritical Conditions (O2/H2 화염의 초임계 조건 연소 특성 연구를 위한 모델 연소기 설계)

  • AHN, YEONG JONG;KIM, YOUNG HOO;KWON, OH CHAE
    • Transactions of the Korean hydrogen and new energy society
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    • v.31 no.1
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    • pp.96-104
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    • 2020
  • A model combustor has been designed and fabricated for studying the combustion characteristics of oxygen (O2)/hydrogen (H2) flames under supercritical conditions. The combustor is designed to allow combustion experiments up to 60 bar, the supercritical pressure condition of O2 and H2. Injectors can be replaced to study various types of flames and the combustion chamber is designed to visualize flames by installing optical windows. Through the preliminary tests, including a high-pressure (up to 60 bar) test using air and combustion tests for coaxial jet flames of liquid oxygen (LO2)/gaseous hydrogen (GH2) at elevated pressure, the reliability of the combustor has been demonstrated.