• Journal of the Korean Institute of Gas
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• v.18 no.4
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• pp.56-62
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• 2014

The present study investigated numerically heat and mass transfer characteristics of a fixed bed reactor by using a computational fluid dynamics (CFD) code of Fluent (ver. 13.0). The temperature and species fraction were estimated for different porosities. For modeling of the catalyst in a fixed bed tube, catalysts were regarded as the porous material, and the empirical correlation of pressure drop based on the modified Eugun equation was used for simulation. In addition, the averaged porosities were taken as 0.545, 0.409, and 0.443 and compared with non-porous state. The predicted results showed that the temperature at the tube wall became higher than that estimated along the center line of tube, leading to higher hydrogen generation by the endothermic reaction and heat transfer. As the mean porosity increases, the hydrogen yield and the outlet temperature decreased because of the pressure drop inside the reformer tube.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.265-270
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• 1989

The present study considers the thermal structure variation in a porous medium caused by changing the most important radiative property of porous medium, absorption coefficient, as well as altering the physical dimension of porous medium and the equivalence ratio of premixed gas mixture. The radiation model was introduced as an unsteady differential form using the two-flux gray radiation model. The role of the conductive heat transfer through both gas phase and porous medium was found to be almost insignificant compared with that of the radiative heat transfer. The reaction zone shifted upstream and the flame thickness decreased as either the geometrical length of porous medium increased or the absorption coefficient decreased.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.342-347
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• 1998

Light-weight conductive polymer composites were prepared by incorporating polyheterocycles such as polypyrrole and polythiophene into pores of a highly porous cross-linked polystyrene, host polymer, to form a conductive network. The highly hydrophobic and porous host polymer was synthesized by concentrated emulsion polymerization method. Polypyrrole-based composites, prepared by employing ferric chloride-methanol system, showed a conductivity as high as 0.82 S/cm. Conductivity of polythiophene-based composites, prepared from ferric chloride-acetonitrile system, was 6.05 S/cm. Conductivity of compositivity was influenced by the initial molar ratio of oxidant to monomer as well. SEM micrographs of the composites showed that conducting polymer coated uniformly the inside wall of the porous host polymer. Shielding effectiveness of the polypyrrole-based composites and of the polythiophene-based composites were 15.2 dB and 22.5 dB at 2.0 GHz, respectively. In the temperature range from 20 to 300K, a polypyrrole impregnated composite exhibited seimiconducting behavior and followed the variable range hopping(VRH) model for charge transport.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.9
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• pp.855-862
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• 2013

A series of 1/5 scale-down reactor flow distribution tests had been conducted to determine the hydraulic characteristics of an APR+ (Advanced Power Reactor Plus), which were used as the input data for an open core thermal margin analysis code. In this study, to examine the applicability of computational fluid dynamics with the porous model to the analysis of APR+ internal flow, simulations were conducted using the commercial multi-purpose computational fluid dynamics software ANSYS CFX V.14. It was concluded that the porous domain approach for some reactor internal structures could adequately predict the flow characteristics inside a reactor in a qualitative manner. If sufficient computational resources are available, the predicted core inlet flow distribution is expected to be more accurate by considering the real geometry of the internal structures, especially upstream of the core inlet.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.81-88
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• 2001

The behavior of porous medium is modeled by linear thermoporoelastic behavior, linear poroviscoelastic behavior, poroplastic behavior, and poroviscoplastic behavior, etc. The behavior has, in general, a complicated aspect which makes a mechanical description of the problem with time. Constitutive modeling for deformation behavior of porous medium with coupling effects is needed since there is interaction between the constituents in pores with a relative velocity to each other. In this work, it is explained 3-dimensional behavior depending on degree of saturation for porous medium composed of homogeneous, isotropic materials. It is obtained the governing equations based on continuum porous mechanics. In addition, it is developed constitutive model which can be understood of behavior for porous medium which can be understood, analysed behavior of porous medium. It can be accomplished exact analysis and prediction of behavior in porous medium. The behavior for porous medium is analysed exactly, and the prediction of deformation behavior is accomplished. Consequently, it will be basis to analyze 3-dimensional behavior in municipal solid waste landfill, and the practical using of porous medium ground which are composed of nonhomogeneous, anisotropic materials can be done widely.

• Composites Research
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• v.25 no.1
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• pp.1-8
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• 2012

In order to predict the thermoelastic behavior of porous composites, poroelastic parameters are measured by using micromechanics-based finite element models. The expanding deformation caused by pore pressure, and the degradation of homogenized elastic moduli with pores are calculated for the assessment of the poroelastic parameters. Various representative volume elements considering the shape, size, and array pattern of pores are modeled and analyzed by a finite element method. The effects of porosity and material anisotropy, and the distribution of stain energy density are investigated carefully. In addition, the measured poroelastic parameters are verified by predicting the thermo-pore-elastic behavior of carbon/phenolic composites.

• Journal of computational fluids engineering
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• v.4 no.3
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• pp.28-34
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• 1999

The objective of this study is to present a numerical treatment of the pressure gradient when control volumes are sharing the interface between a homogeneous fluid and a porous medium. Two possible approaches, e.g. linear interpolation and extrapolation, are considered, and they are applied to the case of a steady and two-dimensional curved channel flow which is partially filled with a porous medium. It was found that the linear extrapolation produces a continuous velocity-field at the interface and thus is recommended. On the contrary, the linear interpolation entails a discontinuous velocity field at the interface, thereby warning its use in connection with the Brinkman-Forchheimer-extended Darcy flow model.

• Korean journal of communication and information
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• v.58
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• pp.178-200
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• 2012

This paper seeks to deal with the point that in order to perform meaningful communication, a conscious act of reflexion must be involved. In other words, performance of communication inevitably requires self-reflexion. It is known that rationality and dialogism function as necessary preconditions and as goals of communication. But these concepts are very ambiguous because the communicational paradox is not considered. The interaction model could be thought to solve the paradox problems, but such solution can ultimately be seen as a result of ignoring the point that personal reflexion is necessary or covering up the logical problem by depending on concepts such as 'legitimation' or 'ideal discourse situation.' Therefore this paper views that the theory of communication based on Luhmann's system theory and constructivism has a more meticulous logics, and considers that the concept of reflexion specifically supplements the interaction model also by examining Schmidt's concept of fiction and Grant's concept of porous communication.

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.676-678
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• 2011

히트펌프 사이클을 이용한 건조 공정은 최종 제품의 생산을 위하여 많은 산업 분야에 요구되는 필수 공정으로 본 논문에서는 대형 히트펌프 건조기의 상부 분리대의 가이드 베인의 형상 및 수량을 최적화 하였다. 이를 위해 팬은 성능곡선 모델을 사용하였고, 증발기와 응축기는 다공성 매질로 가정하였다. 이는 팬을 통과하여 가이드 베인을 따라 건조기 입구로 들어가는 바람의 균일도를 예측할 수 있어 설계 정확도 향상에 기여할 수 있다.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05b
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• pp.78-81
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• 2004

막을 이용한 기체분리의 경우 높은 투과도와 높은 선택도를 얻는 것은 매우 중요하면서도 어려운 일이다. 일반적으로 투과도가 높아지면 선택도가 낮아지고 선택도가 높아지면 투과도가 낮아지는 거동을 보인다. 이 두 가지의 특성을 적절히 조절하여 최적화하기 위하여 막은 기계적 강도를 높이기 위한 다공성의 지지층과 실질적인 분리가 일어나는 얇은 선택 층으로 구성된 복합막의 형태로 제조된다.(중략)