• Title, Summary, Keyword: Porous Media

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Structural Deformation and Flow Analysis for Designing Air Plate of a Fuel Cell (구조 변형을 고려한 연료전지 공기판의 유동 해석)

  • Yang, Ji-Hae;Park, Jung-Sun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.7
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    • pp.877-884
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    • 2004
  • In this paper, structural analysis is performed to investigate the deformation of porous media in a proton exchange membrane fuel cell (PEMFC). Structural deformation of air plate of the fuel cell causes the change in configuration and cross sectional area of the channel. The distributions of mass flow rate and pressure are major factors to decide the performance of a PEMFC. These factors are affected by channel configuration of air plate. Two kinds of numerical air plate models are suggested for flow analyses. Deformed porous media and undeformed porous media are considered for the two models. The Numerical flow analysis results between deformed porous media and undeformed porous media have some discrepancy in pressure distribution. The pressure and velocity distribution under a working condition are numerically calculated to predict the performance of the air plates. Pressure and velocity distributions are compared for two models. It is shown that structural deformation makes difference in flow analysis results.

Numerical Analysis for Characteristics of Flow Fields and Disinfection Performances in the Clearwell with a Porous media Wall (정수지 내 유동 특성과 유공벽을 이용한 소독능 변화에 대한 수치 해석적 연구)

  • Lee, Suk Won;Rhee, Gwang Hoon;Koo, Ja-Yong
    • Journal of Korean Society of Water and Wastewater
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    • v.21 no.6
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    • pp.755-761
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    • 2007
  • Disinfection performance in clearwell is generally measured by CT, which is expressed by $C{\times}T$. C is represented by disinfection concentration, and T is represented by $T_{10}$ which means 90% contact time in clearwell. In order to improve Disinfection performance, augmentation of $T_{10}$ is required. Guide wall has been generally used to improve $T_{10}$ because $T_{10}$ changes according to flow field. In this study, porous media is proposed instead of guide wall, and disinfection performance between guide wall and porous media wall are compared. Flow field and $T_{10}$ in each clearwell are investigated as well. Improved Disinfection performance appear in case of porous media wall compare to guide wall, and best performance occur in porosity factor ${\beta}$ 1e+4.

A Numerical Study on Plate-Type Heat Exchanger Using One-Dimensional Flow Network Model and Porous-Media Model (1차원 유동 네트워크 모델 및 다공성매질 모델을 이용한 판형 열교환기의 수치적 연구)

  • Park, Jaehyun;Kim, Minsung;Min, June Kee;Ha, Man Yeong
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.28 no.1
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    • pp.21-28
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    • 2016
  • A typical heat exchanger, found in many industrial sites, is made up of a large number of unitary cells, which causes difficulties when carrying out full-scale three-dimensional numerical simulations of the heat exchanger to analyze the aero-thermal performance. In the present study, a three-dimensional numerical study using a porous media model was carried out to evaluate the performance of the heat exchanger modelled in two different ways : full-scale and simplified. The pressure drop in the air side and gas side along with the overall heat transfer rate were calculated using a porous media model and the results were then compared to results obtained with a one-dimensional flow network model. The comparison between the results for two different geometries obtained using a porous media model and a one-dimensional flow network model shows good agreement between the simplified geometry and the one-dimensional flow network model. The full-scale geometry shows reasonable differences caused by the geometry such as sudden expansion and contraction.

Nitrogen Removal in Fluidized Bed and Hybrid Reactor using Porous Media (다공성 담체를 이용한 유동상 및 하이브리드 반응기에서의 질소제거)

  • Jun, Byong-Hee
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.5
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    • pp.542-548
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    • 2005
  • A fluidized bed reactor containing porous media has been known to be effective for nitrogen and organic matters removal in wastewater. The porous media which attached microbes plays important roles in simultaneous nitrification/denitrification (SND) due to coexistence of oxic, anaerobic and anoxic zone. For SND reaction, oxygen and organic substrates should be effectively diffused from wastewater into the intra-carrier zone. However, the overgrowth heterotrophic microbes at the surface of porous media may restrict from substrates diffusion. From these viewpoints, the existence and effect of heterotrophic bacteria at surface of porous media might be the key point for nitrogen removal. A porous media-membrane hybrid process was found to have improved nitrogen removal efficiency, due to stimulated denitrification as well as nitrification. Microelectrode studies revealed that although intra-media denitrification rate in a conventional fluidized bed was limited by organic carbon, this limitation was reduced in the hybrid process, resulting in the increased denitrification rate from 0.5 to $4.2\; mgNO_3-N/L/hr$.

Measurement of the Effective Thermal Conductivity of Porous Media in the Mockup Apparatus of Reactor Vessel (원자로 모의 다공질 매체의 유효 열전달 계수 측정)

  • 김용균;황종선;이용범;최석기;남호윤
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.447-450
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    • 1997
  • Temperature distribution measurements in the mockup apparatus of reactor vessel were performed to determine the effective thermal conductivity of Al powder porous media where stainless steel tubes were installed with different geometry. The temperature distributions at four separated sections with different arrangements of porous media have different slopes according to the geometrical configuration. From the measured temperature distribution, effective thermal conductivity have been derived using the least square fitting method.

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Computational rock physics: Lattice-Boltzmann fluid flow simulation in porous media and its applications

  • Keehm, Young-Seuk;Mukerji, Tapan;Nur, Amos
    • 한국지구물리탐사학회:학술대회논문집
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    • pp.661-668
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    • 2003
  • This paper presents Lattice-Boltzmann simulation techniques for single-phase and two-phase fluid flow in porous media. Numerical experiments were performed in a digital rock sample from X-ray microtomography. Computed results showed very good agreement with laboratory measurements of permeability and relative permeability. Two applications using these simulation techniques show the potential of the Lattice-Boltzmann flow simulation to solve many difficult problems coupled with fluid flow in porous media.

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A Comparative Study of Tracer Tests in Fractured and Porous Media (단열 및 다공질 대수층에서의 추적자 시험연구)

  • 이진용;이지훈;김용철;천전용;이민효;이강근
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.132-135
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    • 2001
  • To understand and compare tracer transport in fractured and porous media. multiple tracer tests were conducted in Wonju and Uiwang sites. The target media were fractured in Wonju site and porous in Uiwang site. It was known that groundwater flow for the two hydrogeologic systems could be represented using a EPM approach. However, the tracer transport in the two aquifer systems was greatly different. In this study, we analyzed the different tracer transport behavior in the two systems, from which our understanding of the tracer dispersion was greatly enhanced. we used bromide and chloride as tracers.

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An Experimental study on the Freezing Phenomena of Saturated Porous Media in a Rectangular Cavity (장방형내 함수 다공성 물질의 동결거동에 관한 실험적 연구)

  • Kim, B.C.;Kim, J.I.;Kim, J.H.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.5
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    • pp.386-394
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    • 1991
  • Freezing of saturated porous media contained in a rectangular cavity has been studied experimentally. Water and different diameter glass beads consitituted the liquid and porous media. Solidification front shape, the effects of bead diameter and initial liquid temperature was investigated. When the hot wall temperature was below $4^{\circ}C$, the freezing rate was higher at the top than at the bottom due to the density inversion, but with increasing the hot wall temperature the freezing rate at the top was effected by the liquid temperature and was lower than at the bottom. With increasing the bead diameter, the difference of freezing rate between top and bottom was increased and depends on thermal conductivity. When the liquid temperature was low in the beginning, the freezing rate was high, but with increasing the time almost the same with those of high temperature liquid.

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An Experimental Study on Vacuum Drying of Water-Saturated Porous Media (함수다공질층의 진공건조에 관한 실험적 연구 (Ⅰ))

  • Park, Hyeong-Jin;Kim, Gyeong-Geun;Kim, Myeong-Hwan
    • Journal of Advanced Marine Engineering and Technology
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    • v.20 no.5
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    • pp.68-75
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    • 1996
  • The vacuum drying characteristics of water-saturated porous media were studied experimentally. The water-saturated porous media, water-saturated sand layer, was heated by the isothermal bottom wall of the rectangular vessel. The vacuum drying rate and temperature distribution of the sand layer were measured and calculated under a variety of conditions of heated wall temperature, vacuum rate, and thickness of the test material. It was found that the drying rate due to the heat and mass teansfer is greatly influenced by the heated wall temperature, vacuum rate, and thickness of the test material.

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Analysis of Calculation Model for Specific Air-water Interface Area in Unsaturated Porous Media (불포화 다공성 매질체의 공기-물 경계면 비표면적 계산모델 분석)

  • Kim, Min-Kyu;Kim, Song-Bae;Park, Seong-Jik
    • Journal of The Korean Society of Agricultural Engineers
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    • v.48 no.5
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    • pp.83-93
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    • 2006
  • In unsaturated porous media, the air-water interface (AWI) plays an important role in removing of biocolloids such as bacteria, viruses, and protozoan (oo)cysts. In this study, four models related to calculation of specific AWI area are analyzed to determine the appropriate model, and the selected models are verified using the previously reported experimental data. The results indicate that the modified model from Niemet et al. (2002) is the most appropriate tool for calculating the specific AWI area using the van Genuchten (1980) parameters obtained from the water retention curve. Hence, it is expected that this model could be used to quantitatively determine the attachment of biocolloids to AWI in the transport modeling of biocolloids in unsaturated porous media.