• Tribology and Lubricants
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• v.33 no.1
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• pp.9-14
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• 2017

This paper presents a rotordynamic analysis and the operation of a power turbine applied to a 250 kW super-critical $CO_2$ cycle. The power turbine consists of a turbine wheel and a shaft supported by two fluid film bearings. We use a tilting pad bearing for the power turbine owing to the high speed operation, and employ copper backing pads to improve the thermal management of the bearing. We conduct a rotordynamic analysis based on the design parameters of the power turbine. The dynamic coefficients of the tilting pad bearings were calculated based on the iso-thermal lubrication theory and turbine wheel was modeled as equivalent inertia. The predicted Cambell diagram showed that there are two critical speeds, namely the conical and bending critical speeds under the rated speed. However, the unbalance response prediction showed that vibration levels are controlled within 10 mm for all speed ranges owing to the high damping ratio of the modes. Additionally, the predicted logarithmic decrement indicates that there is no unstable mode. The power turbine uses compressed air at a temperature of $250^{\circ}C$ in its operation, and we monitor the shaft vibration and temperature of the lubricant during the test. In the steady state, we record a temperature rise of $40^{\circ}C$ between the inlet and outlet lubricant and the measured shaft vibration shows good agreement with the prediction.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.88-92
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• 2012

Decrosslinking of crosslinked polypropylene(XLPP) in supercritical methanol was investigated compared with that of crosslinked polyethylene(XLPE). Effect of reaction temperature and initial gel contents was studied using a batch reactor. Gel contents of samples before and after reaction were measured for quantitative analysis. As reaction temperature and initial gel contents increased, the decrosslinking rate increased. The rate of decrosslinking reaction is dependent linearly on the gel contents. Experimental results indicated that the decrosslinking of XLPP was faster than that of XLPE, and it was confirmed quantitatively by the calculation of kinetic constants. In conclusion, it is considered that XLPP has better recyclability than XLPE.

• Polymer(Korea)
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• v.26 no.6
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• pp.785-791
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• 2002

The effect of the supercritical carbon dioxide (sc$CO_2$) on ion-conductive behaviors for polyether electrolytes based on, both poly (ethylene oxide) (PEO) and poly [oligo (oxyethylene glycol) methacrylate] (PMEO) with lithium triflate, LiCF$_3$SO$_3$, has been investigated. In particular, the present research is a new concept for improving the ionic conductivity of polyether electrolytes. The maximum ionic conductivity ($\sigma$$_{max}$) at room temperature of the PEO electrolyte was more than 100 times higher, and the $\sigma$$_{max}$ at 9$0^{\circ}C$ of the PMEO electrolyte was 30 times improved by the se$CO_2$ treatment, respectively. It was revealed that the penetration of $CO_2$ molecules into the polymer matrix causes the increase of carrier ions by ion-dispersion effect and the decrease of glass transition temperature (T$_{g}$) by plasticizing effect that results in the improvement of the ion transport behaviors.viors.

• Journal of Applied Biological Chemistry
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• v.61 no.3
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• pp.239-243
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• 2018

Essential oils of coriander (Coriandrum sativum L.) seeds were extracted by three extraction methods, steam distillation extraction (SDE), hexane extraction (HE) and supercritical extraction (SE), to compare their insecticidal activities against Sitophilus oryzae and S. zeamais. Although the essential oil extracted by HE and SE did not show insecticidal activities, the essential oil extracted by SDE showed the highest insecticidal activities against S. oryzae and S. zeamais. The chemical compositions of the essential oil extracted by SDE were analyzed by GC-MS. The most abundant compounds were linalool (59.92%), camphor (7.94%), linalool oxide (7.70%), p-cymene (7.44%), ${\alpha}-pinene$ (6.44%), limonene (3.29%) and geranyl acetate (3.19%). Camphor and linalool as major constituents showed the highest insecticidal activities against S. oryzae and S. zeamais whereas other constituents did not show insecticidal activities. As a result, the essential oil extracted by SDE, camphor and linalool showed a potential for development as insecticide against the storage pests.

• Journal of the Korean Chemical Society
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• v.34 no.6
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• pp.663-672
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• 1990

The extraction of ginseng saponins with near critical or supercritical ammonia(SCF-NH$_3$) was carried out at 80$^{\circ}C$-160$^{\circ}C$ and ammonia densities of 339.8-525 $mg/cm^3$. In order to evaluate brownish color of white ginseng extracts, a spetrophotometric method was applied in ultraviolet and visible range. The extractibilities of ginseonoside $Rb_1$, -$Rb_2$, -Rc, -Rd, -Re, -Rf, $-Rg_1$, and $-Rg_2$ were determined by high performance liquid choromatography. The best extractability was 7.36% at 133$^{\circ}C$ and 403 $\pm$ 24.605 $mg/cm^3$. In the case of the high extraction temperature, it is thought that extraction times can be reduced and the selectivity of protopanaxatriol can be increased. The brownish color of extracts is affected by temperature and extractability. When extraction temperature is between 132$^{\circ}C$ and 140$^{\circ}C$, it is shown that the range is the retrograde region where extractablility decrease with increasing temperature.

• Clean Technology
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• v.13 no.2
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• pp.99-103
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• 2007

Pt/Nafion self-humidifying membranes for Polymer Electrolyte Membrane Fuel Cell (PEMFC) were synthesized via a supercritical-impregnation method. The Nafion 112 membranes were impregnated with Pt(II) acetylacetonate from a supercritical carbon dioxide ($scCO_2$) solution at $80^{\circ}C$ and 19.8 MPa. After the impregnation, the Pt-impregnated Nafion membrane was converted Pt deposited Nafion(Pt/Nafion) membrane by reducing agent, sodium borohydride ($NaBH_4$) under $50^{\circ}C$ and 2 hours. The prepared Pt/Nafion membranes were investigated by SEM, EDS and EPMA. The performance of the Pt/Nafion membranes was examined in PEMFC as a self-humidifying membrane. The cell performance of the Pt/Nafion membrane at $65^{\circ}C$ is better than that of Nafion 112.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.729-732
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• 2010

The present study has been motivated by the development of a reliable numerical methodology for simulation of kerosene/LOx coaxial swirl injectors. To deal with thermodynamic non-ideality and anomalies of transport properties pronounced at supercritical pressures, a set of subroutine libraries has been constructed based on the cubic equations of state, and applied to an existing flamelet analysis code. For computational efficiency, two-dimensional axisymmetric RANS formulation with swirl was adopted and validated successfully against an isothermal coaxial swirling jet. For the actual problem with high pressure combustion, however, numerical results show that the RANS models yield excessive production of turbulence probably due to high density gradient magnitude in the vicinity of mixing layer of swirling film flow, and imply strongly further improvement of the turbulence models.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.658-663
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• 2010

With petroleum reserves dwindling, interest has been increasing worldwide in Fischer-Tropsch synthesis (FT) as a method of producing synthetic liquid fuels and chemicals from coal, natural gas or biomass. In general, FT synthesis is operated through the gas phase fixed-bed reaction system. Recently, there are lots of study in supercritical fluid due to unique characteristics such as the quick diffusion of reactant gas, effective removal of reaction heat, and the in-situ extraction of high molecular weight hydrocarbon, such as wax. In this study, our major aim is to obtain a deeper insight into the effect of the type of support on the reaction performance over a supported cobalt catalyst in a fixed bed reactor.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.388-396
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• 2010

As a part of basic studies on monitoring and saturation estimation of carbon dioxide ($CO_2$) storage using resistivity survey, laboratory experiment has been conducted to measure the change of the electrical resistivity through repeated experiments of supercritical $CO_2$ and brine water injection into homogeneous and heterogeneous sandstones. The $CO_2$ saturation is estimated by using resistivity index based on the resistivity measurements. The experimental results of two types of sandstones show that the effect of pore structure in the rock and the effect of contained clay minerals in the rock can be affected to calculate the $CO_2$ saturation. The result can be useful to evaluate the $CO_2$ saturation based on resistivity survey at the site where $CO_2 sequestrates.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.41 no.2
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• pp.151-157
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• 2015

In this study, we prepared Eriobotrya japonica leaf extracts by several extraction processes and then evaluated their biological activities for their potential application as a new raw material of functional cosmetic. Their whitening effects were measured by tyrosinase inhibitory activities, and anti-inflammatory effects were determined by inhibitory activities of nitric oxide (NO) production. Among the several extracts obtained from E. japonica leaf, supercritical fluid extract showed tyrosinase inhibitory activities at the concentration of 10%. Inhibitory activity on NO production effect related to anti-inflammatory efficacy was in the order: supercritical fluid extract > ethanol extract > hot water extract. According to the results of MTT assay, cell cytotoxicity was not observed at all concentrations except for a 5% concentration of the 70% ethanol extract. For whitening effects, 30% ethanol and 70% ethanol extract showed mushroom tyrosinase inhibitory activity at the concentration of 5%. These results indicated that E. japonica leaf extracts could have the functional effects when they are added as ingredients in cosmetics.