• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.289-295
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• 2004

The heat transfer coefficient and pressure drop during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flowmeter, an evaporator, and a gas cooler(test section). The main components of the water loop consist of a variable-speed pump, an isothermal tank, and a flowmeter. The gas cooler is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The test section consists of smooth, horizontal stainless steel tube of the outer diameter of 9.53mm and of the inner diameter of 7.75mm. The length of the test section is 6m. The refrigerant mass fluxes were 200∼300kg/(m2$.$s) and the inlet pressure of the gas cooler varied from 7.5㎫ to 8.5㎫. The main results were summarized as follows : Pressure drop of CO2 increases with increasing gas cooler pressure. The friction factors of CO2 in a horizontal tube show a relatively good agreement with the correlation by Blasius. The heat transfer coefficient of CO2 in transcritical region increases with decreasing gas cooler pressure and decreasing mass flux of CO2. Most of correlations proposed in a transcritical region showed significant deviations with experimental data except for those predicted by Gnielinski.

• Food Science and Preservation
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• v.13 no.3
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• pp.363-368
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• 2006

This study was performed to develop flavor materials from Elsholtzia ciliata Hylander with analyzing functionality and aroma profile and to optimize supercritical fluid extraction method and optimum condition. The qualities of water extracts such as total yield total phenolic compound electron donation ability, estragole and L-carvone, were affected by extraction pressure than time. The response variables had significant with pressure than with time and the established polynomial model was suitable(P>0.05) model by Lack-of-Fit analysis. The optimum extraction conditions which were limited of maximum value for dependent variables under experimental conditions based on central composite design were 238 bar and 42 min.

• Polymer(Korea)
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• v.24 no.4
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• pp.505-512
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• 2000

The mixture density data for poly(lactide-co-glycolide) [PLGA] with supercritical $CO_2$, CHF$_3$ and CHClF$_2$ were obtained in the temperature range of 27 to 10$0^{\circ}C$ and at pressures as high as 3000 bar (PLGA$_{x}$, Where the molar concentration of glycolide in the backbone, x, range from 0 to 50 mol%). The PLA-$CO_2$, PLA-CHF$_3$, and PLA-CHClF$_2$ systems dissolve in the pressure less than 1430 below 700, and below 100 bar, respectively. The mixture density shows from 1.084 to 1.334 g/cm$^3$ at temperatures from 27 to 93$^{\circ}C$. The PLGA$_{15}$ -$CO_2$ mixture dissolves at pressures of below 1900 bar and the mixture density is in the range of 1.158 to 1.247 g/cm$^3$ at temperatures between 37 and 92$^{\circ}C$. The solubilities of the PLGA$_{25}$ for $CO_2$, CHF$_3$, and CHClF$_2$ are shown to pressure as high as 2390, 1470, and 118 bar, respectively, and the mixture density exhibits iron 1.154 to 1.535 g/cm$^3$ at temperatures from 29 to 81$^{\circ}C$. The PLGA$_{50}$-$CO_2$ system does not dissolve at 24$0^{\circ}C$ and 3000 bar while the PLGA$_{50}$-CHCIF$_2$ does easily at 5$0^{\circ}C$ and 100 bar. The mixture density for the PLGA-CHClF$_2$ system increases even at low pressures as the glycolide molar concentration increases.es.es.

• Polymer(Korea)
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• v.24 no.4
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• pp.529-537
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• 2000

The effects of the gel content on the cell structures of PP sheets by using an electron-curing system were investigated. Three extruded PP sheets crosslinked by three different doses were used for the batch foaming process with the supercritical state $CO_2$. Experiments were also performed in order to study the effects of the gel content, saturation pressure and temperature on cell structures. Then foaming conditions, such as temperature and duration of time, were changed. The amount of gas absorbed into PP samples was not affected by gel contents and the operating condition of saturation pressure, which was higher than 2000 psi. The foam cells of PP with a low gel content grew irregularly at a higher foaming temperature and for a longer duration of foaming time. However, PP samples with high gel content showed even cell structures and narrow tell size distributions under the severe conditions of high foaming temperatures and long duration of foaming time.

• Food Science of Animal Resources
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• v.32 no.5
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• pp.644-651
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• 2012

We have investigated the effect of lard fraction extracted with supercritical carbon dioxide (SC-$CO_2$) on the flavor enhancement of maillard reaction product (MRP) based meat flavors. MRP based meat flavors were prepared with low glutamic acid (Glu) hydrolyzed wheat gluten (NaCl concentration: 7.61%(w/v)), ribose, cysteine, garlic juice powder, protease-digested Lentinus edodes powder and lard fractions extracted with SC-$CO_2$. Lard was extracted with SC-$CO_2$ at each of three temperatures (40, 60, and $80^{\circ}C$) and at each of four pressures (30, 40, 50, and 60 MPa). Obtained lard SC-$CO_2$ fractions and MRP based meat flavors with those fractions were analyzed for their total yield, aroma pattern by SMart nose system, and sensorial properties. The extraction yield had no difference as temperature increased from $40^{\circ}C$ to $60^{\circ}C$ and even decreased at $80^{\circ}C$. However, increase in pressure level at $40^{\circ}C$ drastically increased the extraction yield. The aroma patterns of raw lard and lard SC-$CO_2$ fractions with 30 MPa were significantly discriminated from those of SC-$CO_2$ lard fractions extracted with higher pressure by SMart nose system. Aroma pattern of MRP based meat flavors with higher pressure extracted lard fractions also showed significant difference through pattern analysis by the SMart nose system. The MRP based meat flavor with lard SC-$CO_2$ fractions at 50 and 60 MPa were described as less sulfuric, less pungent, and more balanced in roasted meat and sweet attributes from sensory evaluation.

• Korean Journal of Food Science and Technology
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• v.30 no.3
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• pp.574-580
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• 1998

The technical feasibility of removing cholesterol from milk fat by supercritical carbon dioxide $(SC-CO_2)$ extraction followed by adsorption on different adsorbents and of fractionating milk fat into different fatty acid composition at $40^{\circ}C/276$ bar was investigated. Cholesterol could be selectively removed from milk fat by adsorption on a typical commercial florisil with $SC-CO_2$ extraction. Lower weight ratio of milk fat feed to florisil showed higher reduction of cholesterol, but gave lower yield in the milk fat fractions. The effective capacity of florisil for removing cholesterol from milk fat was 2.0g/g, which is the ratio of the fat feed to the adsorbent for 89% cholesterol reduction with a fat yield of 57.5%. Fatty acid composition showed higher short-chain and lower unsaturated long-chain fatty acids in the extracted fractions. Milk fat fractionation method by supercritical fluid extraction in coupled with adsorption would appear suitable for removing undesirable ingredients such as cholesterol and for enriching short-chain fatty acids in the fractions.

• Clean Technology
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• v.24 no.4
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• pp.275-279
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• 2018

In this study, microemulsion formation of water and carbon dioxide was investigated by using surfactant as one of the methods for increasing the mutual solubility between water and carbon dioxide. The surfactant 2,2,3,3,3-Pentafluoro-1-propanol was added to form a microemulsion of water and carbon dioxide. The cloud point change and trend of micro emulsion were investigated by adding water and a certain amount of surfactant, 2,2,3,3,3-Pentafluoro-1-propanol to supercritical carbon dioxide. In the case of surfactant + carbon dioxide system, it was 8.35 ~ 12.69 MPa in temperature range of 313.2 ~ 353.2 K. In the case of water + surfactant + carbon dioxide system, the temperature ranged from 318.2 ~ 338.2 K to pressure range 7.83 ~ 17.28 MPa.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.3
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• pp.17-24
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• 2016

The reacting flows of gaseous hydrogen/liquid oxygen 2D coaxial shear injector with varying recess length are numerically analyzed. The standard ${\kappa}-e$ model and laminar flamelet model are adopted for the steady turbulent combustion with the ideal and real gas equations. As the recess length increases, the recirculating region in the combustion chamber expands and the vorticity is intensified. Also, the variations of temperature, products, and pressure are strongly related to the recess length. The results show that an efficient combustor can be obtained by the introduction of the recessed injector.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.55-56
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• 2006

냉매 충전량과 이차유체의 입구조건은 $CO_2$용 열펌프시스템의 성능실험에서 중요한 제어변수이다. 따라서, 열펌프사이클의 적용과 난방성능 향상을 위해 제어변수의 특성을 조사하는 것이 필요하다. 본 논문에서, $CO_2$용 열펌프 사이클의 성능 실험은 여러 가지 냉매 충전량에서 이차유체 입구조건에 변화를 주어 수행 되었다. 실험결과, 난방COP는 냉매 충전량이 증가함에 따라 1158g의 냉매 충전량에서 최대가 되었다가 감소하는 경향이 나타나며, 이는 COP가 최대가 되는 냉매충전량이 존재함을 나타낸다. 또한, 난방성능은 가스쿨러내 이차유체의 질량유량의 증가에 따라 증가하였다. 가스냉각기내 2차유체의 입구은도가 $10^{\circ}C$에서 $40^{\circ}C$로 증가하면, 난방용량, 압축일량, 토출압력은 각각 -8.57%, -35.89%, 32.78%로 변화했으며, 증발기 2차유체의 입구 온도가 감소하였을 때 난방COP는 감소하는 경향을 보였다.

• Textile Coloration and Finishing
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• v.31 no.1
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• pp.14-24
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• 2019

In this study, dyeability of PET fabric was investigated depending on dyeing temperature, pressure, and leveling time using laboratory scale supercritical $CO_2(scCO_2)$ dyeing machine. Dyeing temperature, pressure, leveling time were varied from 100, 120, $130^{\circ}C$, 150, 200, 250bar, 40, 60, 80, 100min, respectively. It is proved that the higher temperature of $scCO_2$ dyeing process, the higher K/S value and the lower $L^*$ value, which in turn means the lower amount of dyeing molecules remained after process done. Compared 200bar with 250bar of dyeing pressure, $scCO_2$ dyeing fabrics under 250bar appeared to have a lower $L^*$ value, a higher K/S value than those from 200bar, meaning that dyeing color turns to darker with higher dyeing pressure. The experiments showed that the most ideal condition for $scCO_2$ dyeing process is $120^{\circ}C$, 250bar for 60 - 100min of leveling time.