• 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.

• Clean Technology
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• v.18 no.2
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• pp.155-161
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• 2012

The purpose of this study is to remove paraffin wax binder effectively from powder injection molded part using supercritical fluids in powder injection molding process. For a thin powder injection molded part about 1-2 mm thickness, paraffin wax binder can be removed rapidly without any defect by traditional supercritical extraction process which has fixed high temperature and pressure condition. But, for a thick powder injection molded part, there are limitations in removing paraffin wax binder by the fixed high process condition because crack occurs at the beginning step. Therefore, here we studied variable condition debinding process that starts with mild process condition at the beginning step and then increase the process conditions simultaneously at each step. To find out the initial process condition that has the highest extraction yield without any defect for each sample thickness, we investigated various supercritical debinding conditions using 1-4 mm thickness ceramic injection molded sample. By using the variable condition debinding process that starts with the initial process condition at the first step and then increasing process conditions simultaneously at each step (temperature from 333.15 to 343.15 K, pressure from 12 to 27 MPa, and $CO_2$ flow rate from 1.5 to 10 L/min), over 95% of paraffin wax binder was removed from the 4 mm thick (10 mm diameter) ceramic injection molded disk samples within 5 hours.

• Journal of the Korean Institute of Gas
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• v.25 no.4
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• pp.10-18
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• 2021

CO₂ storage technology in an aquifer is one of the most effective way to decrease global warming due to a high storage capacity and economics. A demonstration-scale offshore CO₂ storage project was performed in a geological deep aquifer in the Pohang Basin, Korea for a technological development of large-scale CO₂ storage. A challenging issue in the early design stage of the project was to establish the proper injectivity during CO₂ injection. To solve this issue, injection conditions were calculated by calculating injection rate, pressure, temperature, CO₂ phase change, and thermodynamic properties. For this study, we simulated and numerically analyzed CO₂ phase change from gas to supercritical phase and flow behavior in transport piping and injection tubing using OLGA program. Our results provide the injectivity conditions of CO₂ injection system combined with a bottomhole pressure of an aquifer.

• Journal of the Semiconductor & Display Technology
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• v.16 no.1
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• pp.22-28
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• 2017

The result of stripping process for the removal of the post etch/ash Photoresist (PR) residue on an aluminum patterned wafer by using supercritical $CO_2$ ($sc-CO_2$) mixture, was investigated by scanning of electron microscope (SEM) inspection of wafer, measuring the cloud points and visual observation of the state of $sc-CO_2$ mixtures. It was found that $sc-CO_2$ mixtures were made by mixing additives and $sc-CO_2$ should form homogeneous and transparent phase (HTP) in order to effectively and uniformly remove the post etch/ash PR residue on the aluminum patterned wafer using them. The additives were formulated by mixing and co-solvents like an amine compound and fluorosurfactants used as HTP agents, and the PR residue on the wafer were able to be rapidly and effectively removed using the $sc-CO_2$ mixture of HTP. The five kinds of additives were formulated by the recipe of mixing co-solvents and surfactants, which were able to remove PR residue on the wafer by mixing with $sc-CO_2$ at the stripping temperature range from 40 to $80^{\circ}C$. The five kinds of $sc-CO_2$ mixtures which were named as PR removers were made, which were able to form HTP within the above described stripping temperature. The cloud points of $sc-CO_2$ mixtures were measured to find correlation between them and HTP.

• Textile Coloration and Finishing
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• v.31 no.1
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• pp.48-64
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• 2019

With evolution in the production environment of the textile industry, the need for non-water-based dyeing technologies and eco-friendly process facilities in the dyeing and processing stages has increased. In recent years, supercritical fluid dyes have been developed and commercialized in Europe, centering on this demand. However, so far, such dyes have been mainly applied in the processing of PET fibers. Basic research has mainly involved investigation of dyeing by supercritical carbon dioxide or solubility of such dyes, and more in-depth research should be continuously carried out. In this review, we describe the types and characteristics of supercritical fluids that exhibit specific properties at pressures and temperatures over the critical point. In addition, the state of the art in the dyeing and processing technology using supercritical fluids and associated, processing problems, environmental regulation, and wastewater treatment issues are described in detail. We hope this review can contribute to the supercritical fluid technology being further developed as an environment friendly dyeing processing method. Furthermore, we expect that the technique can be used as a means of ensuring different, high-quality dyed products.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.292-295
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• 2008

In a SCWR (SuperCritical pressure Water cooled Reactor), the coolant temperature initially at below the pseudo-critical temperature at the bottom of a reactor core increases as the coolant flows upward through the sub-channels of the fuel assemblies, and it finally becomes higher than the pseudo-critical temperature when it leaves the reactor core. At certain conditions, heat transfer deterioration occurs near the pseudo-critical temperature and it may cause a drastic rise of the fuel surface temperature resulting a fuel failure. Therefore, an accurate estimation of the heat transfer coefficient is very important for the thermal-hydraulic design of a reactor core. An experiment on heat transfer to the vertically upward flowing $CO_2$ at a supercritical pressure in a circular tube were performed at KAERI. The internal diameter of the test section is 6.32 mm, which corresponds to the hydraulic diameter of a sub-channel in the conceptional design proposed by KAERI. The test range of the mass flux is 285 to 1200 kg/m$^2$s and the maximum heat flux is 170 kW/m$^2$. The inlet pressure is maintained at 8.12 MPa, which is 1.1 times the critical pressure. A new correlation, which covers both the normal and deterioration heat transfer regimes was proposed and compared with the estimations by exiting correlations.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.95-103
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• 2014

During the international effort to develop the next generation nuclear reactor technologies, many new power cycle concepts were derived to improve efficiency and reduce the capital cost. Among many innovative power cycles, it was identified that the supercritical $CO_2$ (S-$CO_2$) Brayton cycle technology has a big potential to outperform the existing steam cycle and eventually replace it. The S-$CO_2$ cycle achieves high efficiency with very compact size, which is the ultimate advantage for a power cycle to have. The S-$CO_2$ cycle has a great potential not only for the future nuclear applications but also for general heat sources such as coal, natural gas, and concentrated solar. In this paper, a brief introduction to the S-$CO_2$ power cycle technologies will be first provided, and a short summary of current research and development status of the power cycle technology around the world will be followed. Especially the research works performed by KAIST, KAERI and several related research institutions in Korea will be reviewed in more detail, since they have recently developing a strong infrastructure to test these ideas by constructing a demonstration facility while producing many innovative ideas to improve and realize the concept.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.386-391
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• 2022

This study is about a technique for obtaining collagen by extracting fat by treating collagen-containing liposuction effluent in the presence of supercritical fluid. Using a supercritical solvent, a collagen extract could be obtained from animal-derived fat in a short time (about 6 hours), and about 2-3% of collagen by mass compared to the raw material could be obtained. The presence of collagen in the extract obtained by supercritical extraction was confirmed by SDS-PAGE, and it was confirmed that it was type 1 collagen having a relatively large molecular weight. In addition, the growth factors of IGF-1, bFGF, VEGF and NGF were analyzed to find out which growth factors were present in the collagen obtained by supercritical extraction, and it was found that these growth factors were contained in the extract. There was no significant difference in DNA content per mg of sample before and after supercritical treatment. Further in-depth studies are likely to be needed on decellularization technology using the supercritical process. In conclusion, the extracellular matrix obtained through the solvent extraction process using a supercritical fluid contains growth factors above a certain amount even after decellularization and removal of fat, so that it was found that not only biocompatibility is greatly increased, but also tissue regeneration can be rapidly induced.

• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.498-508
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• 2021

Micro reactors are increasingly being considered for utilization as distributed power sources. Hence, the probabilistic safety assessment (PSA) of a direct supercritical-CO₂-cooled fast reactor, called micro modular reactor (MMR), was performed in this study; this reactor was developed using innovative design concepts. It adopted a modular design and passive safety systems to minimize site constraints. As the MMR is in its conceptual design phase, design weaknesses and valuable safety insights could be identified during PSA. Level 1 internal event PSA was carried out involving literature survey, system characterization, identification of initiating events, transient analyses, development of event trees and fault trees, and quantification. The initiating events and scenarios significantly contributing to core damage frequency (CDF) were determined to identify design weaknesses in MMR. The most significant initiating event category contributing to CDF was the transients with the power conversion system initially available category, owing to its relatively high occurrence frequency. Further, an importance analysis revealed that the safety of MMR can be significantly improved by improving the reliability of reactor trip and passive decay heat removal system operation. The findings presented in this paper are expected to contribute toward future applications of PSA for assessing unconventional nuclear reactors in their conceptual design phases.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1482-1494
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• 2022

Power conversion cycles (Subcritical Steam, Supercritical Steam, Open Air Brayton, Recuperated Air Brayton, Combined Cycle, Closed Brayton Supercritical CO₂ (sCO₂), and Stirling) are evaluated for land-based nuclear microreactors based on technical maturity, system efficiency, size, cost and maintainability, safety implications, and siting considerations. Based upon these criteria, Air Brayton systems were selected for further evaluation. A brief history of the development and applications of Brayton power systems is given, followed by a description of how these thermal-to-electrical energy conversion systems might be integrated with a nuclear microreactor. Modeling is performed for optimized cycles operating at 3 MW(e) with turbine inlet temperatures of 500 ℃, 650 ℃ and 850 ℃, corresponding to: a) sodium fast, b) molten salt or heat pipe, and c) helium or sodium thermal reactors, coupled with three types of Brayton power conversion units (PCUs): 1) simple open-cycle gas turbine, 2) recuperated open-cycle gas turbine, and 3) recuperated and intercooled open-cycle gas turbine. Aeroderivative turboshaft engines employing the simple Brayton cycle and two industrial gas turbine engines employing recuperated air Brayton cycles are also analyzed. These engines offer mature technology that can facilitate near-term deployment with a modest improvement in efficiency.