• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.6
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• pp.599-608
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• 2000

One dimensional numerical modeling was carried out for the melting behavior of dry snow and the unsaturated flow when heat was supplied from the bottom surface. Discrepancy between the previous experimental data and the present numerical results is substantially reduced by considering the density change of water permeation layer due to the infiltration of meltwater. In the parametric study for effective thermal conductivity, it was found that the effect of this parameter to the behavior of snow melting is minor. Sensitivity analysis showed that the melting time is most sensitive to changes in supplied heat flux, snow temperature, and bulk density, whereas snow bulk density and residual saturation have a significant effect on the height of water permeation layer in snow.

• KSBB Journal
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• v.10 no.5
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• pp.482-490
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• 1995

The relationship between pressure drop and liquid flow rate, for an axial and a radial flow chromatographic column packed with compressible porous media was theoretically analyzed using modified Kozeny-Carman equation. The results were compared with experimental observations obtained using compressible DEAE-agarose as a model medium. At 2-9 psi range studied, the theoretical derivation accounting for 'gel compression' effect predicted simple Langmuirian type response of volumetric flow rate to changes in pressure drop. On the other hand, the experimental response was more or less sigmoidal. At the same pressure drop, radial column showed 2-3 times higher flow rates than those of axial column both theoretically and experimentally. Using r-HBsAg crude extract, protein resolution effects between the two types of columns at different flow rates were compared side-by-side. It turned out that, though general chromatographic behavior was very similar, axial column was somewhat superior in terms of r-HBsAg recovery yield and specificity. However, the number of theoretical plates analysis indicated the protein resolution effects were comparable.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.41-43
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• 2013

In order to simulate and visually observe combustion phenomena in cylindrical radial-flow porous inert media, a radial multi-channel burner, made of transparent quartz plates, was fabricated. Flame stabilization characteristics and its pulsating instability in the burner were experimentally investigated with respect to various mixture flow rates and equivalence ratio. As a result, five different flame behaviors, such as stable flame, pulsating instability, sudden extinction, blowout and unstable extinction, were observed. Mean radial position of circularly arranged multi-flame and its averaged burning velocity were measured and then compared to the freely propagating flame. The multi-flame pulsation frequency is about several tens of Hz and it is supposed to be generated by the heat diffusion enhancement to cold pre-mixture by the intensive gas-solid interaction.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.207-212
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• 1999

화학반응이 일어나는 고정층 반응기의 성능을 모사하고 해석하기 위해서는 반응베드의 열 및 물질전달 특성을 정확히 아는 것이 중요하다. 본 연구에서는 화학열펌프에 사용되는 금속염-팽창흑연 다공성 반응매체의 유효열전도도와 기체투과도를 측정하였다. 유효열전도도는 전이 일차원 열류기법을 이용하여 측정하였고, 기체투과도는 Darcy's law를 이용하여 측정하였다. 팽창흑연이 함유된 반응베드의 유효열전도도와 기체투과도는 흑연을 기준으로 한 겉보기밀도에 따라 각각 14.1-36.5 W/mK, 8.0x$10^{-15}$-$10^{-12}$ $m^2$의 범위에 있었다.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.24-32
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• 2018

Nanocellulose was surface-functionalized toward the applications in enhanced oil recovery (EOR) as a green alternative. The focus of this paper is on the effect of this material based nanofluid (NF) on foam lamella stabilization through studying its bubble breakup dynamics and flow behaviors in constricted mircofluidic devices. The NF stabilized foam produced an improved flow resistance across the capillary largely due to the capillary trapped bubbles at the contraction. The "snap-off" caused the NF stabilized foam to produce finer textured bubbles, which can migrate readily forward to the deep porous media, as revealed by the pressure profiles.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.238-238
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• 2019

산지계곡에는 큰 자갈이나 호박돌이 무더기로 퇴적되어 있어서 대규모 공극을 구성한다. 호우시 이 돌무더기 내부에 빠른 흐름이 형성되고 이에 따른 퇴적사면의 급격한 변동이 발생하기도 한다. 본 연구에서는 대공극 매질의 흐름은 산지계곡에 퇴적된 균일 직경을 가진 구형 입자로 구성된 대규모 공극 매질을 구성하고, 비 Darcy 흐름의 유속에 미치는 입경의 영향을 수리실험으로 조사하였다. 실험에 사용된 구형 입자는 크기가 15.5mm, 25mm, 36.5mm인 유리구슬이고, 조성된 매질의 공극율은 Table 1과 같으며, 실험에서 침투거리는 40cm로 하였다. 실험유량은 0.98~15.41 t/s이고 입자 Reynolds 수는 120~4,580의 범위였다. 동수경사가 증가하면 매질의 단면평균 유속이 비선형적으로 증가하였다. 입경이 작을수록 유속과 동수경사 사이의 비선형적 경향이 더 크다(Fig.1). 동일한 동수경사에서 매질의 입경이 클수록 유속이 빠르게 나타났다.

• Coupled systems mechanics
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• v.3 no.1
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• pp.73-88
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• 2014

The paper deals with a model founded on the physical processes in concrete subject to high temperatures. The model is developed in the framework of continuum damage mechanics and the theory of porous media and is demonstrated on selected structures. The model comprises balance equations for heat transfer, mass transfer of water and vapour, for linear momentum and for reaction. The balance equations are completed by constitutive equations considering the special behaviour of concrete at high temperatures. Furthermore, the limitation and decline of admissible stresses is achieved by using a composed, temperature depending crack surface with a formulation for the damage evolution. Finally, the complete coupled model is applied to several structures and to different concrete in order to determine their influence on the high-temperature-behaviour.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.2
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• pp.25-34
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• 2020

As leakage in nuclear power plants could cause a variety of problems, it is very critical to monitor leakage from the safety point of view. Accordingly, a new type of leak detection system is currently being developed and flow characteristics of the sampling and transportation system are investigated by using numerical analysis as a part of the development process in this study. The results showed that the steam mass fraction varied according to the effect of the gap between the insulation and piping component, transportation velocity, and material properties of porous media during the sampling and transportation process. The results of this study should be useful for understanding flow characteristics of the sampling and transportation system and its design and application.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3390-3397
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• 2022

Among the different techniques available, nuclear methods, including gamma-gamma logging tools, are of special importance. Though the real environment which surrounds the drilled borehole is a complex fractured medium which the fluid can flow through the porosities, simulation studies generally use the traditional model of a homogeneous mixture of formation and the liquid. Considering a previously published study, which shows that modeling of fluid flow in fractured reservoirs and simulating the formation as an inhomogeneous fractured medium leads to different results compared with those of homogeneous mixture, here we study the effect of the presence of drilling fluid (mudcake) on the response of the detectors in both the models. To study this effect, a typical gamma-gamma logging tool was modeled by using the MCNPX Monte Carlo code. The results show that the responses of the detectors in the mixture model in the presence of various thicknesses of mudcake are sensitive to the density of the formation material. However, this effect is not notable in the inhomogeneous fractured medium. These results emphasize the importance of the model employed for simulation of the medium in gamma-gamma well-logging.

• Korean Journal of Microbiology
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• v.45 no.2
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• pp.133-139
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• 2009

A nutrient-concentrating system was operated to retrieve total phosphorus efficiently from a non-point pollution source. Attached bacteria were expected to play an important role in the system. Phosphorous was concentrated by formation of bacterial biofilms on rubberized coconut fiber media of the system. While concentration of total phosphorus (TP) ranged merely 0.12~0.35 mg/L in the stream water, TP levels in pore water and the media were 0.45~0.86 mg/L and 40.91~242.71 mg/kg, respectively. Total bacterial number (TBN) ranged $0.3\sim2.3\times10^6$ cells/ml in stream water, $0.4\sim4.4\times10^6$ cells/ml in pore water and $0.8\sim1.9\times10^9$ cells/g in media. There was a close correlation between TP and TBN. Based on band profiles in DGGE analyses, bacterial communities in the media were different from that in the stream water. Clostridium spp. were abundant in the stream water while Aquabacterium spp. were dominant species in early stages of biofilm formation in the media. The genera predominant in matured biofilms of the media were Clostridium and Enterococcus.