• New & Renewable Energy
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• v.7 no.4
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• pp.18-29
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• 2011

Biofuls are considered as an option to reduce greenhouse gases emission, increase energy supply diversity and security of supply, as well as an opportunity for job creation and rural development. First of all, biofuls technologies have been promoted as a means for reducing the carbon intensity of the transport sector. Hence, in the last decade biofuels production has been driven by governmental policies. The key instruments widely adopted to foster production and increase consumption have been mandatory blending targets, tax exemptions and sibsidies. As one of the most powerful instruments, biofuel mandates require fuel producers to produce a pre-defined amount (or share) of biofuels and blend them with petroleum fuel. National biofuels mandates are in place 35 countries and partially in place in 6 countries. In this study, we reviewed status of global biofuels policies to reduce greenhouse gases in the European Union, United States and other countires worldwide. Especially, we discussed representative biofuels mandates policies same as Renewable Fuel Standard (RFS, US), Renewable Transport Fules Obligation (RTFO, UK) in transport sector.

• Corrosion Science and Technology
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• v.13 no.5
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• pp.170-177
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• 2014

Polyurethane coating was designed to give a hydrophobic property on its surface by modifying it with hydroxyl terminated polydimethylsiloxane and then effects of surface hydrophobic tendency, water transport behavior and hence corrosion protectiveness of the modified polyurethane coating were examined using FT-IR/ATR spectroscopy, contact angle measurement and electrochemical impedance test. As results, the surface of polyurethane coating was changed from hydrophilic to hydrophobic property due primarily to a phase separation tendency between polyurethane and modifier by the modification. The phase separation tendency is more appreciable when modified by polydimethylsiloxane with higher content. Water transport behavior of the modified polyurethane coating decreased more in that with higher hydrophobic surface property. The decrease in the impedance modulus ${\mid}Z{\mid}$ at low frequency region in immersion test for polyurethane coatings was associated with the water transport behavior and surface hydrophobic properties of modified polyurethane coatings. The corrosion protectiveness of the modified polyurethane coated carbon steel generally increased with an increase in the modifier content, confirming that corrosion protectiveness of the modified polyurethane coating is well agreed with its water transport behavior.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.174.1-174.1
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• 2011

Biogas production and utilisation is an emerging alternative energy technology. Biogas is produced from the biological breakdown of organic matter through anaerobic digestion. Biogas can be utilized for various energy services such as heating, electricity generation and vehicle fuel. Especially, to be utilized as vehicle fuel, raw biogas needs to be upgraded, that is, mainly the removal of carbon dioxide to increase the methane content, up to more than 95% in some cases, similar to the composition of fossil-based natural gas. Biogas fuelled vehicles can reduce $CO_2$ emission by between 75% and 200% compared with fossil fuels. Biomethane development is largely driven by national initiative and predominately by concerns for national air pollution and waste management. Recently, biogas projects for vehicle fuels by some companies are ongoing and Korea government also announced investment to develop biogas as a transport fuel. Therefore, the aim of this study is to examine the feasibility of biomethane as a transport fuel in Korea. In this study, we investigated quality characteristics, quality standard and upgrading technology to use vehicle fuel of transport sector in Korea.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.419-420
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• 2012

Lithium-ion battery (LIB) usually used for valuable electronic devices are extended to applications. High stability negative electrode materials for LIB were investigated using electrodeposition of nanoparticles (NPs) on the nanostructured carbon. NPs with about 70 nm diameters were evenly prepared on the graphitic carbon materials using electrodeposition process at room temperature. It was observed that the NPs were homogeneously embedded into not only external surface but bottom part of the graphitic carbon network. The graphitic carbon material covered with NPs enables facile electron transport owing to the network structure and improves structural collapse during cycling. This facile room temperature process is expected to be applicable to other anode materials such as Sn and Al for the anode of LIB.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.6
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• pp.722-733
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• 2013

Ground-based measurements were conducted from August 25 to September 8 of 2011 for understanding characteristics of carbonaceous aerosols measured at Gosan. Chemical components and their sources were discussed by analysis of organic compounds with identification of primary and secondary products in particulate matter. Thus, organic carbon (OC) and elemental carbon (EC) based on the carbonaceous thermal distribution (CTD), which provides detailed carbon signature characteristics relative to analytical temperature, was used to improve the carbon fractionation of the analytical method. In addition, organic compounds by gas chromatography technique with the backward trajectories were discussed for characteristics of carbonaceous aerosols. Different air-masses were classified related to the OC thermal signatures and the organic molecular markers such as aromatic acids and PAHs. We concluded that the aging process was influenced by the long-range transport from East Sea area.

• Steel and Composite Structures
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• v.45 no.5
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• pp.641-652
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• 2022

Fluid-conveying tubes are widely used to transport oil and natural gas in industries. As an advanced composite material, functionally graded carbon nanotube-reinforced composites (FG-CNTRC) have great potential to empower the industry. However, nonlinear free vibration of the FG-CNTRC fluid-conveying pipe has not been attempted in thermal environment. In this paper, the nonlinear free vibration characteristic of functionally graded nanocomposite fluid-conveying pipe reinforced by single-walled carbon nanotubes (SWNTs) in thermal environment is investigated. The SWCNTs gradient distributed in the thickness direction of the pipe forms different reinforcement patterns. The material properties of the FG-CNTRC are estimated by rule of mixture. A higher-order shear deformation theory and Hamilton's variational principle are employed to derive the motion equations incorporating the thermal and fluid effects. A two-step perturbation method is implemented to obtain the closed-form asymptotic solutions for these nonlinear partial differential equations. The nonlinear frequencies under several reinforcement patterns are presented and discussed. We conduct a series of studies aimed at revealing the effects of the flow velocity, the environment temperature, the inner-outer diameter ratio, and the carbon nanotube volume fraction on the nature frequency.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.524-529
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• 2001

Because of the ozone layer depletion and global wanning, new alternative refrigerants are being developed. Among them, HFC refrigerants are thought promising, but some European countries are arguing that these refrigerants are also harmful to the global wanning. Therefore, natural refrigerants should be considered as an eventual alternative in refrigerators and heat pumps. In the present study, the supercritical gas cooling process are computationally analysed by employing various turbulence models of carbon dioxide in a trans critical refrigeration cycle. The gas cooling process near the critical point experiences a drastic change in thermodynamic and transport properties, thus the heat transfer characteristics would be different from those of two or single phases. Based on the computational results, the correlations to estimate the near-critical heat transfer characteristics will are obtained.

• Advances in Energy Research
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• v.1 no.1
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• pp.53-78
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• 2013

Methane carbon dioxide reforming (MCDR) is a promising way of utilizing greenhouse gas for hydrogen-rich fuel production. Compared with other types of reactors, Compact Reformers (CRs) are efficient for fuel processing. In a CR, a thin solid plate is placed between two porous catalyst layers to enable efficient heat transfer between the two catalyst layers. In this study, the physical and chemical processes of MCDR in a CR are studied numerically with a 2D numerical model. The model considers the multi-component gas transport and heat transfer in the fuel channel and the porous catalyst layer, and the MCDR reaction kinetics in the catalyst layer. The finite volume method (FVM) is used for discretizing the governing equations. The SIMPLEC algorithm is used to couple the pressure and the velocity. Parametrical simulations are conducted to analyze in detail the effects of various operating/structural parameters on the fuel processing behavior.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.139-148
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• 1999

In oder to analyze the effect of operating conditions on pulverized coal combustion, a numerical study is conducted at the pulverized coal combustor. Eulerian approach is used for the gas phase, whereas Lagrangian approach is used for the particle phase. Turbulence is modeled using standard ${\kappa}-{\varepsilon}$ model. The description of species transport and combustion chemistry is based on the mixture fraction/probability density function(PDF) approach. Radiation is modeled using P-l model. The turbulent dispersion of particles is modeled using discrete random walk model. Swirl number of secondary air affects the flame front, particle residence time and carbon conversion. Primary/Secondary air mass ratio also affects the flame front but little affects the carbon conversion and particle residence time. Air-fuel ratio only affects the flame front due to lack of oxygen. Radiation strongly affects the flame front and gas temperature distribution because pulverized coal flame of high temperature is considered.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.723-728
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• 2007

In order to evaluate the performance of carbon dioxide cycle with a sub-cooling loop. a simulation system was developed to predict the steady state of $CO_2$ trans-critical cycle. Mathematical models are derived to describe the relationships between the system's coefficient of performance and other operating parameters The mathematical models are based entirely on the basic mass and energy conservation law and thermodynamic and transport properties of carbon dioxide A parametric study has been conducted in order to investigate the effect of sub-cooling loop and various operating conditions on the cycle performance. An optimal mass fraction of a refrigerant flowing through sub-cooling cycle existed for the given evaporating temperature, high pressure and air inlet temperature through gas cooler.