• 제목, 요약, 키워드: Porous Media

검색결과 554건 처리시간 0.047초

구조 해석과 유동 해석을 통한 연료전지 공기판 설계 (Structural and Flow Analysis for Designing Air Plate of a Fuel Cell)

  • 박정선;양지혜;이원용
    • 대한기계학회:학술대회논문집
    • /
    • /
    • pp.585-590
    • /
    • 2003
  • The distributions of mass flow rate and pressure are major factors to deside the performance of a proton exchange membrane fuel cell (PEMFC). These factors are affected by channel configuration of air plate. In this paper. structural analysis is performed to investigate deformation of porous media. Two kind of models are suggest for flow analyses. Deformed porous media and undeformed porous media are considered for air plate model. The Numerical flow analysis results with deformed porous media and undeformed porous media had some discrepancy in pressure distribution. The pressure and velocity in a working condition are numerically calculated to predict the performance of the air plates. Distributions of the parameters in the PEMFC are analyzed numerically under steady-state conditions.

  • PDF

CONVERGENCE OF APPROXIMATE SOLUTIONS TO SCALAR CONSERVATION LAWS BY DEGENERATE DIFFUSION

  • Hwang, Seok
    • 대한수학회논문집
    • /
    • v.22 no.1
    • /
    • pp.145-155
    • /
    • 2007
  • In this paper, we show the convergence of approximate solutions to the convective porous media equation using methodology developed in [8]. First, we obtain the approximate transport equation for the given convective porous media equation. Then using the averaging lemma, we obtain the convergence.

Modeling of coupled THMC processes in porous media

  • Kowalsky, Ursula;Bente, Sonja;Dinkler, Dieter
    • Coupled systems mechanics
    • /
    • v.3 no.1
    • /
    • pp.27-52
    • /
    • 2014
  • For landfill monitoring and aftercare, long-term prognoses of emission and deformation behaviour are required. Landfills may be considered as heterogeneous porous soil-like structures, in which flow and transport processes of gases and liquids interact with local material degradation and mechanical deformation of the solid skeleton. Therefore, in the framework of continuous porous media mechanics a model is developed that permits the investigation of coupled mechanical, hydraulical and biochemical processes in municipal solid waste landfills.

건자재활용을 위한 축열용 다공성 미립자 상변환 물질 흡착 특성 (Charateristics on the PCM absorbed porous media as thermal storage applicable for construction material)

  • 이효진
    • KIEAE Journal
    • /
    • v.17 no.3
    • /
    • pp.107-112
    • /
    • 2017
  • Purpose: Both silica gel and activated carbon black particles were adopted for use as PCM absorbed porous media applicable as construction materials. To investigate usable methods for absorbing PCM into the media, they were soaked into PCM and also tested for enhancement of PCM absorption into them. Method: To test PCM absorption into some porous media such as both ${\varphi}1{\sim}2mm$ and $10{\mu}m$ silica gels, and $50{\mu}m$ activated carbon black, $43^{\circ}C$ PCM was used as a laten heat material. The method, soaking into PCM was applied to this study, and the media were moderately rotated by centrifuge to have the extra PCM flow out. DSC analysis was conducted to investigate the melting and solidifying of the PCM absorbed into the porous media. Result: It was found that PCM was absorbed into the porous media by over 85 wt% of all particles. In addition, it was noted that the ultrasonic vibrator was accelerating the PCM absorption into the particles to three times higher speed than simple soaking. Centrifuge was adopted to remove extra PCM sticking on the particle surfaces and extra PCM was moderately removed from the surfaces of the particles. DSC analysis indicated that the latent heat of the absorbed PCM particles was 160 J/g, and the melting temperature was approximately $40^{\circ}C{\sim}50^{\circ}C$.

다공성 매질에서 액화질소의 거동에 대한 연구 (STUDY ON BEHAVIOR OF LIQUID NITROGEN IN POROUS MEDIA)

  • 최성웅;이우일
    • 한국전산유체공학회지
    • /
    • v.18 no.2
    • /
    • pp.17-25
    • /
    • 2013
  • The process of flow through porous media is of interest a wide range of engineering fields and areas, and the importance of fluid flow with a change in phase arises from the fact that many industrial processes rely on these phenomena for materials process, energy transfer. Especially, the flow phenomena of cryogenic liquid subjected to evaporation is of interest to investigate how the cryogenic liquid behaves in the porous structure. In this study, thermo physical properties, morphological properties of the glass wool with different bulk densities in terms of its temperature-dependence and permeability behaviors under different applying pressure are discussed. Using the experimentally determined properties, characteristics of two main experimental results are investigated. In addition, simulation results are used to realize the cryogenic liquid's flow in porous media, and are compared with experimental results. By using the experimentally determined properties, more reasonable results can be suggested in dealing with porous media flow.

공극매체에서의 파동장에 대한 Boussinesq 방정식의 유도 및 적용 (Derivation and Application of Boussinesq Equations for the Wave Field in Porous Media)

  • 전인식;민용침;임학수
    • 대한토목학회논문집
    • /
    • v.35 no.5
    • /
    • pp.1061-1071
    • /
    • 2015
  • 공극매체에서의 파동장을 해석할 목적으로 공극매체 흐름에 대한 Reynolds 이송정리를 적용하여 공극매체에서의 Navier-Stokes 방정식을 유도하였으며 기존의 연구들과 비교하였다. 또한, 이 N-S 방정식을 이용하여 공극매체 내외에서 파동장의 비선형성과 분산성을 적절히 재현하기 위한 확장형 Boussinesq 방정식을 유도하였다. 이들 방정식의 정확도를 검증하기 위하여 공극방파제의 반사율과 투과율에 대한 수치해석을 수행하여 그 결과를 기존의 수리실험결과들과 비교하였다. 수치해석결과는 토립자의 가상질량계수에 민감하게 반응하였으며 계수를 영으로 처리했을 때 수리실험결과와 비교적 잘 일치하는 것으로 나타났다.

Silica nanoparticles as a high-performance filtrate reducer for foam fluid in porous media

  • Lv, Qichao;Li, Zhaomin;Li, Binfei;Shi, Dashan;Zhang, Chao;Li, Binglin
    • Journal of Industrial and Engineering Chemistry
    • /
    • v.45
    • /
    • pp.171-181
    • /
    • 2017
  • During the fracturing operations for oils and gases, not only the oil and gas reservoirs, but also the nearby civil aquifers are often polluted by the invasion of fracturing fluid filtrates. In this study, we investigated the potential of silica nanoparticles as a high-performance filtrate reducer for a foam fluid in a porous media. First, the three factors affecting filtration reduction using nanoparticles, i.e., surface rheology, foam slipping, and foam stability, were described. Then, the foam filtration through a porous media in the core was measured using a dynamic fluid-loss device, and the effects of foam quality, pressure drop, and core permeability on the performance of the filtrate reducer were evaluated. The difficulty of bubbles flowing from a throat to a pore in a porous media was described by resistance gradient coefficient $C_f$, which is a combination of surface tension and viscoelastic modulus and increases by adding nanoparticles. Nanoparticles improve the roughness of the $SiO_2/sodium$ dodecyl benzene sulfonate foam film surface, thus increasing the slipping resistance $F_{slip}$ when foams flow on the wall of a throat in a porous media. For the foams in a porous media, the diffusion of bubbles decreased in the presence of nanoparticles, and the growth rate of gas bubble size also decreased, thus increasing the foam resistance to gas channeling. The results of core filtration tests indicate that the fluid-loss-control properties increased with foam quality ranging from 0 to 85%, and the negative effects of pressure drop and permeability increase to foam filtration were weakened by adding $SiO_2$ nanoparticles. Thus, silica nanoparticles can be used as a high-performance filtrate reducer for a foam fluid in a porous media.

사용후핵연료 집합체의 다공성 매질 적용영역에 따른 콘크리트 저장용기 열전달 해석 (HEAT TRANSFER ANALYSIS OF CONCRETE STORAGE CASK DEPENDING ON POROUS MEDIA REGION OF SPENT FUEL ASSEMBLY)

  • 김형진;강경욱
    • 한국전산유체공학회지
    • /
    • v.21 no.4
    • /
    • pp.33-39
    • /
    • 2016
  • Generally, thermal analysis of spent fuel storage cask has been conducted using the porous media and effective thermal conductivity model to simplify the structural complexity of spent fuel assemblies. As the fuel assembly is composed of two regions; active fuel region corresponding to UO2 pellets and unactive fuel region corresponding to the top and bottom nozzle, the heat transfer performance can be influenced depending on porous media application at these regions. In this study, numerical analysis on concrete storage cask of spent fuel was performed to investigate heat transfer effects for two cases; one was porous media application only to active fuel region(case 1) and the other one was porous media to whole length of fuel assembly(case 2). Using computational fluid dynamics code, the three dimensional, 1/4 symmetry model was constructed. For two cases, maximum temperatures for each component were evaluated below the allowable limits. For the case 1, maximum temperatures for fuel cladding, neutron absorber and baskets inside the canister were slightly higher than those for the case 2. In particular, even though the helium flows with low velocity due to buoyant forces occurred at the top and bottom of unactive fuel region, treating only active fuel region as the porous media was ineffective in respect of the heat removal performance of concrete storage cask, implying a conservative result.

다공성(多孔性) 유리메디아를 이용한 고정상(固定床) 생물막법(生物膜法)에 관한 연구(硏究) (A Study on a Fixed Bed Biofilm Process Using Porous Glass Media)

  • 윤태일;김재훈
    • 상하수도학회지
    • /
    • v.10 no.1
    • /
    • pp.112-120
    • /
    • 1996
  • In this study, the porous glass media was utilized as biomass carrier, and the optimum characteristics of this new media in fixed bed biofilm process were investigated. The characteristics of media considered here are a void volume fraction, a specific surface area, and surface characteristics of media. The effect of surface roughness and material could be clearly demonstrated by the fact that the porous glass media showed a good potential for biofilm development. This might results from the fact that biofilm is initially formed in the surface cavities of the media is protect from the shear effect. Therefore, the microcolonies are not readily detached by the fluid shear. In the steady state, biofilm formation along the packing bed depth was different from media to media. The specific area was also an important factor for the attachment of microorganism on the media surface. The specific area was also an important factor for the attachment of microorganism on the media surface. In the case of porous glass media, about $100m^2/m^3$ was enough to obtain a good organic removal efficiency The organic removal efficiency could be improved by increasing the void volume fraction in the reactor, at least 80% was required to obtain a high removal efficiency and prevent clogging. From the analysis of kinetics study, the yield coefficient, Y, was 0.42 mgMLSS/mgSBOD, endogenous respiration coefficient, ke, was $0.12day^{-1}$ and substrate removel coefficient of Mckinney. km, was $16.8hr^{-1}$ for the porous glass media G-2

  • PDF

발포금속을 삽입한 밀집형 열교환기 최적 설계 (Optimum Design of a Compact Heat Exchanger with Foam Metal Insertion)

  • 이대영;진재식;강병하
    • 설비공학논문집
    • /
    • v.13 no.7
    • /
    • pp.612-620
    • /
    • 2001
  • The optimum design of a heat exchanger with porous media insertion is studied in this paper. It is considered that the aluminum foam metal is inserted in a flat plate channel and air flows through it. The influence of the microstructure of the foam metal on the pressure drop and heat transfer is investigated utilizing previous analytical results and existing correlation equations. Design parameters are identified as the unit-cell size and the ligament thickness of the porous medium, and their effects are examined. The results show that there exists optimum microstructure of the porous media maximizing heat transfer with a constant pressure drop. When the increase in the pressure drop is within a practically acceptable range, the increase in the heat transfer is dominated by the increase in the heat transfer area due to the porous medium insertion. Consequently, among the porous media with a constant pressure drop, the heat transfer is maximized with a microstructure with maximum specific surface area.

  • PDF