• KSBB Journal
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• v.26 no.5
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• pp.453-458
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• 2011

In this study, two different extraction techniques, organic solvent extraction and supercritical carbon dioxide ($SCCO_2$) extraction, were employed to evaluate the extraction efficiency of oil from Chlorella vulgaris. In the organic solvent extraction, the effects of various organic solvent on the extraction yield were investigated. The $SCCO_2$ extraction was carried out while varying such operating parameters as temperature, pressure, $SCCO_2$ flow rate, and cosolvent. About 4.9 wt% of oil was extracted from ground Chrollera vulgaris for 18 h when dichloromethane/methanol (2：1, v/v) was used as an extraction solvent. The oil yield of the $SCCO_2$ extraction was found to be very low (0.53 wt%) and to increase up to about 0.86 wt% with the addition of cosolvent.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1049-1054
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• 1998

In order to fabricate ideal powders new processing is necessary in which the solute atoms in solution ra-pidly move to mix each other to the degree of molecular level the viscosity of solution should be low not to effect the moving of solute atoms and the powders could be directly obtained as crystalline. Supercritical fluid is defined as condensed gas sated up to its critical pressure and temperature. In this paper su-percritical fluid methods were studied as a new ceramic processing of powder preparation. The crystalline powders of TiO2 which are useful for electronic ceramic materials were fabricated by hydrolysis of titanium (IV) ethoxide using ethanol as a supercritical fluid at the condition of 270$\pm$3$^{\circ}C$, 7.3 MPa for 2hr. The cry stalline anatase powders could be directly obtained and its primary particle size was 20 min.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.625-631
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• 2000

In this study, the characteristics and sinterablities of TiO2 powders which were fabricated on sol-gel process and supercritical fluid process were examined. The powders fabricated on sol-gel process were amorphous. The particle size and shape were changed with the amount of water used for hydrolysis of titanium ethoxide. The powders were changed from amorphous to crystalline by heating at 400℃. The crystalline anatase TiO2 powders were directly prepared in ethanol supercritical fluid condition that temperature was 270±3℃ and pressure was 7.3 MPa. It's primary crystalline size was 20 nm and agglomerated as spherical shape whose size was 0.7∼1㎛. The powders prepared on sol-gel process were not sintered densely at 900℃ because of abnormal grain growth. However, the powders which prepared on supercritical fluid process were sintered densely at the comparatively low temperature of 800℃ by ideal growth of grain, which are fired at 900℃.

• Journal of Power System Engineering
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• v.18 no.4
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• pp.60-65
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• 2014

In this paper, cycle performance analysis for heating capacity, compression work and COP of R134a supercritical heat pump is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include superheating degree, pressure and outlet temperature of gas cooler, compressor efficiency and evaporating temperature in the R134a supercritical heat pump system. The main results were summarized as follows : Superheating degree, pressure and outlet temperature of gas cooler, compressor efficiency and evaporating temperature of R134a heat pump system have an effect on the heating capacity, compression work and COP of this system. With a thorough grasp of these effect, it is necessary to design the supercritical heat pump using R134a. The prediction for COP of R134a supercritical heat pump have been proposed through multiple regression analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.313-318
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• 1996

In this paper, a parametric study of the unbalance response and the stability is carried out to show the influence of seal parameters on the response of rotor. The seal parameters optimized are the seal clearance and the seal length. The minimum quantity of a Q factor in the critical speed and the maximum quantity of a logarithmic decreement in the operating speed, avoiding the reign of resonance, are the objective function. This paper describes a new approach to find a seal parameter of rotor system. The optimization method is used genetic algorithms, which are search algorithms based on the mechanics of natural selection and natural genetics. The results show the capability of this method and indicate that an optimal design of seals can improve the unbalance and the stability of rotor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.330-333
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• 2008

Present paper introduces the research activities on fuel-air mixing and combustion of supersonic turbulent flows in scramjet combustor carried out in Aerospace Combustion and Propulsion Laboratory of the department of Aerospace Engineering of the Pusan national University. Also, an introduction will be given to the characteristics of the supercritical hydrocarbon fuel combustion in a practical scramjet engine and its numerical modeling approaches.

• Textile Coloration and Finishing
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• v.31 no.1
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• pp.25-32
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• 2019

The influence of the contact amount of carbon dioxide per unit mass of dyestuff(${\alpha}$) on dyeing uniformity in supercritical fluid dyeing is analyzed in this study. The experiments using a 5L class Pilot Scale dyeing machine is carried out for this study purpose. For a fixed temperature and pressure, the amount of sample and the dyeing leveling time were considered as process variables. The results show that the increase in the amount of the sample causes a higher color difference than the reference sample, and it also increases the amount of residual dye. On the other hand, the color difference tended to decrease with the increase in dyeing time. Based on these results, the correlation between ${\alpha}$ value and dyeing uniformity in supercritical fluid dyeing is obtained.

• Journal of ILASS-Korea
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• v.26 no.4
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• pp.171-181
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• 2021

This study presents a prediction methodology of thermodynamic properties by using RK-PR Equation of State in a wide range of temperature and pressure conditions including both sub-critical and super-critical regions, in order to obtain thermophysical properties for hydrocarbon aviation fuels and their products resulting from endothermic reactions. The density and the constant pressure specific heat are predicted in the temperature range from 300 to 1000 K and the pressure from 0.1 to 5.0 MPa, which includes all of the liquid and gas phases and the super-critical region of three representative hydrocarbon fuels, and then compared with those data obtained from the NIST database. Results show that the averaged relative deviations of both predicted density and constant pressure specific heat are below 5% in the specified temperature and pressure conditions, and the major sources of the errors are observed near the saturation line and the critical point of each fuel.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.31 no.7
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• pp.32-44
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• 2002

1989년 프레온계 냉매의 대체 가능한 물질로서 $CO_2$재 출연하게 되었고, 그 이후 관련 연구는 점차 증가하였다. 1996년 북미 지역에서 $CO_2$의 연구는 일리노이 대학내 ACRC (Air Conditioning and Refrigeration Center)에서 최대로 시작되었다. 연구비의 90%는 산업체에 의해 지원되었고, 나머지는 미국 정부에 의해 지원되었다. 본 고는 자동차 및 가정용 에어컨 및 열펌프 시스템 및 구성부품 개선에 대한 전반적인 연구활동에 관해 기술하였다. 또한 시스템 성능 비교 결과는 열전달, 압력강하, 사이를 변환,냉매 분해에 대한 연구 지침을 제시하였고, 지속적인 연구 노력을 통하여 천연냉매를 이용하여 간접적인 지구온난화 가스 방출을 최소화하기 위한 시스템 효율을 증가시키고 빈다. $CO_2$의 고유 특징인 초임계 $CO_2$사이클, $CO_2$의 열역학 및 전달 물성치를 통한 효율 개선, 내부 열교환을 통한 사이클 성능 개선방안도 기술되었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.1
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• pp.23-31
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• 2011

At supercritical pressure, the physical properties of fluid change substantially and the heat transfer at a temperature similar to the critical or pseudo-critical temperature improves considerably; however, the heat transfer may deteriorate due to a sudden increase in the wall temperature at a certain condition of a mass and heat flux. In this study, the heat transfer rates in $CO_2$ flowing vertically upward and downward in a circular tube with a diameter of 4.57 mm under various conditions were calculated by measuring the temperature of the outer wall of the tube. The published heat transfer correlations were analyzed by comparing their prediction values with 7,250 experimental data. By introducing a buoyancy parameter, a heat transfer correlation, which could be applied only to a normal heat transfer regime, was extended such that it can be applied to regime of heat transfer deterioration. The published criteria for heat transfer deterioration were evaluated against the conditions obtained from the experiment in this study.