• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1113-1120
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• 1988

This paper presents the results of an experimental investigation on one dimensional excess enthalpy flame formed in a porous block. The investigation is undertaken in order to further the physical understanding of internal heat recirculation from reaction zone to unburned mixture. Two porous blocks are placed at both sides of combustion block to control the temperature distribution in the combustion block by means of radiation heat transfer. Mean temperature measurement reveals the general nature of the reaction zone in the porous material. It is conformed that the temperature of reaction zone exceeds the adiabatic flame temperature and the flame is stabilized at the out range of flammibility limit derived by conventional burner.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.375-388
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• 2022

This paper deals with the process of obtaining sound transmission loss of a cylindrical silencer lined with multi-layered poroelastic sound absorbing materials. The Biot model and the Johnson-Champoux-Allard-Lafarge (JCAL) model were used to deal with waves propagating in multi-layered poroelastic materials. The boundary conditions required for analysis of the silencer were obtained and the numerical process of finding modes was explained. A numerical experiment was conducted on the 2-layered silencer using the modes and the transmission loss converged with the first 12 modes. Finally, the mode matching method proposed in this research was validated by being compared with the results calculated from Finite Element Method (FEM) about different kinds of sound absorbing materials.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.3
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• pp.189-195
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• 2007

Using fractal dimensionality theory proposed by Riew and Sposito (1991), we attempted to analyze quantitatively the characteristics of porous distribution for built-in soils in the mini-lysimeter and artificial seed-bed media. The 2" stainless core soil samples were taken from lysimeter soils. Artificial seed-bed media were compacted in the acrylic core filled with raw materials consisted of cocopeat, zeolite and perlite. N (Constant number of partitioned group size smaller media volumes) and r (Self-similarity ratio) parameters consisting of fractal dimension D=log(N)/log(1/r) were obtained by Excel Programme using the Riew and Sposito's fractal model. The pore distribution of tested media was screened in pore size and its occurring frequency. The results reveal that the distribution range of pores is wider in the lysimeter soils than in the seed-bed media, while average size of pores in the media is smaller in lysimeter core soils than in seed-bed media.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.10
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• pp.927-932
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• 2009

Toxic and recalcitrant organic pollutants in wastewaters can be effectively treated when advanced oxidation and biodegradation are combined, ideally with intimate coupling, in which both processes occur simultaneously in the same system. One means to achieve intimate coupling is to coat nanoscale $TiO_2$ on the outside of macroporous biofilm carriers. This study investigated the kinetics of photocatalysis with $TiO_2$-coated porous carriers. The carriers were made of polyvinyl alcohol (PVA) and coated with $TiO_2$ using a low-temperature sol-gel process. The $TiO_2$-coated carriers catalyzed the oxidation of methylene blue (MB) effectively under irradiation of UV light. The overall reaction rate with adsorption and photolysis saturated at high MB concentration, and approached the adsorption rate, which was first order for all MB concent rations. This result indicates that adsorbed MB may have slowed photocatalysis by blocking active sites for photocatalysis. The overall kinetics could be described by a quasi-Langmuir model. The estimated maximum specific (per unit mass of $TiO_2$) transformation rate of MB by the $TiO_2$-coated carriers was four times larger than that obtained from slurry-$TiO_2$ reactors. This observation demonstrated that the $TiO_2$ present as a coating on the carriers maintained high efficiency for transforming recalcitrant organic matter via photocatalysis. These findings serve as a foundation for advancement of an intimate coupling of photocatalysis to biodegradation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.2
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• pp.223-232
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• 2018

Bird screen meshes are installed at the air inlet and outlet ducts of spent fuel storage casks to inhibit the intrusion of debris from the external environment. The presence of these screens introduces an additional resistance to air flow through the ducts. In this study, a porous media model was developed to simplify the bird screen meshes. CFD analyses were used to derive and verify the flow resistance factors for the porous media model. Thermal analyses were carried out for concrete storage cask using the porous media model. Thermal tests were performed for concrete casks with bird screen meshes. The measured temperatures were compared with the analysis results for the porous model. The analysis results agreed well with the test results. The analysis temperatures were slightly higher than the test temperatures. Therefore, the reliability and conservatism of the analysis results for the porous model have been verified.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.358-367
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• 2013

In the present paper, we apply a porous modelling technique to accurately predict the pressure drop through the strainer by replacing all or some of the filter composed of perforated plates with porous media and there imposing the streamwise and transverse loss coefficients required according to the Forchheimer law and then confirm its effectiveness. At first, the streamwise coefficient is obtained by performing a simple simulation on the pipe flow mimicking the hole flow. Subsequently, the transverse coefficient is obtained by setting a unit pattern to have common flow loss characteristics with the repeated shape patterns in the filter, then performing numerical simulations on the prototype and porous model of the unit shape pattern, and finally comparing their results of pressure drop. To validate the applied modeling technique, we perform the numerical simulation with the two specified loss coefficients on a whole shape of strainer and compare the modeling results with those of the corresponding prototype numerical simulation. Comparison indicates that the modeling technique can predict the pressure drop and flow characteristics comparatively accurately and save the number of nodes closely related to the computational cost (CPU and memory) by about 3~4 times compared with the prototype simulation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.984-990
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• 2017

Mesh screen modeling and liquid propellant discharge simulation of surface tension tank were performed using commercial CFD software Flow-3d. $350{\times}2600$, $400{\times}3000$ and $510{\times}3600$ DTW mesh screen were modeled using macroscopic porous media model. Porosity, capillary pressure, and drag coefficient were assigned for each mesh screen model, and bubble point simulations were performed. The mesh screen model was validated with the experimental data. Based on the screen modeling, liquid propellant discharge simulation from PMD tank was performed. NTO was assigned as the liquid propellant, and void was set to flow into the tank inlet to achieve an initial volume flow rate of liquid propellant in $3{\times}10^{-3}g$ acceleration condition. The intial flow pressure drop through the mesh screen was approximately 270 Pa, and the pressure drop increased with time. Liquid propellant discharge was sustained until the flow pressure drop reached approximately 630 Pa, which was near the estimated bubble point value of the screen model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.4
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• pp.257-268
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• 2017

This paper proposes an efficient two-dimensional simulation model for solid oxide fuel cells (SOFCs) based on the electrochemical effectiveness model. The effectiveness model is known to accurately predict the current generation performance of SOFC electrodes, by considering the complex reaction/transport processes that occur within thin active functional layers near the electrolyte. After validation tests, the two-dimensional simulation model was used to calculate the distribution of current density and oxygen concentration transverse to the flow channel in anode-supported SOFCs, with which the oxygen depletion characteristics were investigated in detail. In addition, simulations were also conducted to determine the minimum number of grids required in the transverse direction to efficiently obtain accurate results.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.04b
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• pp.21-22
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• 1997

최근의 이온교환막은 종래의 양이온교환막의 표면에 polycation 등의 얇은 층을 덧붙인 다층막(multi-layer membrane)의 형태가 많이 이용되고 있으며, 정전기적 반발력의 차 등을 이용하여 원자가가 다른 이온들간의 투과성에 차를 부여하기 위하여 이용되고 있다. 이 때문에 polycation막을 통한 1가 이온과 2가 이온의 투과성을 연구하는 것은 우수한 이온교환막을 제작하는것 이상으로 중요하다. 본 연구에서는 고정전하농도(fixed charge density, $\Phi$ X)가 낮은 다공성 저전하음이온교환막을 제작하여, 양측에 대이온(counterion)은 같고 복이온(co-ion)이 다른 전해질용액을 두었을 경우에 관찰되는 막전위를 측정하였다. 이를 토대로 음이온교환막을 통한 막전위의 농도의존성에 관하여 검토하였으며, 비평형열역학(non-equilibrium thermodynamies)에 기초한 이론적 모델을 도입하여 실험치와 비교, 해석하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.4
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• pp.162-167
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• 2005

As the properties of porous materials during the drying process relate to the atomistic defects of heterogeneous materials such as dislocation, grain, grain boundary, pore, etc., the knowledge of nano-scale analysis is needed in order to accurately analyze the drying process for porous materials. In this study, the atomic behavior of porous materials Is statically predicted by using the molecular dynamics simulation and the nano-scale material properties are computed. The elastic modulus, thermal expansion coefficient, and volumetric heat capacity numerically found from the molecular dynamics simulation are compared with those of experiment and theory and proved the accuracy.