• Title, Summary, Keyword: Porous Media

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Study on Flow behavior of Liquid Nitrogen for Porous Media in Square-section Cylinder (사각 기둥 실린더 내부 다공성 매질에서의 액화질소의 거동에 대한 연구)

  • Choi, Sung Woong;Lee, Woo Il
    • Journal of the Korean Institute of Gas
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    • v.17 no.1
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    • pp.26-34
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    • 2013
  • The multiphase flow analysis related to phase change can be adapted to lots of areas such as evaporation and condensation has many interesting branches due to complicated phenomenon. In this study, the experimental investigation of cryogenic liquid in the porous media with various densities was shown how the cryogenic liquid behaves in the porous structure. For this study, permeability behaviors under different applying pressure of the glass wool with different bulk densities are discussed. Experimental investigation on the behavior of cryogenic liquefied nitrogen in the porous media is conducted. The result was that the non linearity of pressure gradient with location is increased and the permeability is decreased as the bulk density of glass wool increased. Lastly, simulation results with CFD commercial package program are used to realize the cryogenic liquid's flow in porous media to compare the finding with experimental results.

Simulation of Two Phase Flow in Porous Media After Disso of Methane Hydrates (다공성 매질 내에서 메탄 하이드레이트의 분해에 의한 2 상 유동 해석)

  • Chang, Dong-Gun;Kim, Nam-Jin;Lee, Jae-Yong;Kim, Chong-Bo
    • Proceedings of the KSME Conference
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    • pp.241-246
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    • 2000
  • Gas hydrates are solid solutions when water molecules are linked through hydrogen bondin create host lattice cavities that can enclose a large variety of guest gas molecules. The natural hydrate crystal may exist at low temperature above the normal freezing point of water and pressure greater than about 30 bars. A lot of quantities of natural gas hydrates exists in the ear many production schemes are being studied. In the present investigation, depressurization method considered to predict the production of gas and the simulation of the two phase flow - gas and - in porous media is being carried out. The simulation show about the fluid flow in porous have a variety of applications in industry. Results provide the appearance of gas and water prod the pressure profile, the saturation of gas/ water/ hydrates profiles and the location of the pl front.

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Two-scale approaches for fracture in fluid-saturated porous media

  • de Borst, Rene;Rethore, Julien;Abellan, Marie-Angele
    • Interaction and multiscale mechanics
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    • v.1 no.1
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    • pp.83-101
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    • 2008
  • A derivation is given of two-scale models that are able to describe deformation and flow in a fluid-saturated and progressively fracturing porous medium. From the micromechanics of the flow in the cavity, identities are derived that couple the local momentum and the mass balances to the governing equations for a fluid-saturated porous medium, which are assumed to hold on the macroscopic scale. By exploiting the partition-of-unity property of the finite element shape functions, the position and direction of the fractures are independent from the underlying discretization. The finite element equations are derived for this two-scale approach and integrated over time. The resulting discrete equations are nonlinear due to the cohesive crack model and the nonlinearity of the coupling terms. A consistent linearization is given for use within a Newton-Raphson iterative procedure. Finally, examples are given to show the versatility and the efficiency of the approach.

Development of Numerical Technique to Analyze the Flow Characteristics of Porous Media Using Lattice Boltzmann Method (격자볼쯔만법을 이용한 다공체의 유동특성 분석방법 개발에 관한 연구)

  • Kim, Hyung Min
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.11
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    • pp.689-695
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    • 2016
  • The performance of proton exchange membrane fuel cells (PEMFC) is strongly related to the water flow and accumulation in the gas diffusion layer (GDL) and catalyst layer. Understanding the behavior of fluid from the characteristics of the media is crucial for the improvement of the performance and design of the GDL. In this paper, a numerical method is proposed to calculate the design parameters of the GDL, i.e., permeability, tortuosity, and effective diffusivity. The fluid flow in a channel filled with randomly packed hard spheres is simulated to validate the method. The flow simulation was performed by lattice Boltzmann method with bounce back condition for the solid volume fraction in the porous media, with different values of porosities. Permeability, which affects the flow, was calculated from the average pressure drop and the velocity in the porous media. Tortuosity, calculated by the ratio the average path length of the randomly injected massless particles to the thickness of the porous media, and the resultant effective diffusivity were in good agreement with the theoretical model. The suggested method can be used to calculate the parameters of real GDL accurately without any modification.

Comparison in Porous Structure and Water Eetention with the Different Porous Media by Fractal Fragmentation Model (다공성 매체의 차원 분열 모델 적용에 의한 토양과 상토의 공극분포와 보수력 비교)

  • Oh, Dong-Shig;Kim, Lee-Yul;Jung, Yeong-Sang
    • 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.

A Numerical Study on Flow in Porous Structure using Non-Hydrostatic Model (비정수압 수치모형을 이용한 다공성 구조물의 유동에 관한 수치적 연구)

  • Shin, Choong Hun;Yoon, Sung Bum
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.30 no.3
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    • pp.114-122
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    • 2018
  • This paper introduces a non-hydrostatic wave model SWASH for simulating wave interactions with porous structures. This model calculates the flow in porous media based on volume-averaged Reynolds-averaged Navier-Stokes equations (VARANS) in ${\sigma}$-coordinate. The empirical coefficients of resistance used to account for the flow in a porous media often need to be measured or calibrated. In this study, the empirical resistance coefficients used in the model are calibrated and validated using laboratory experiments, involving dam-break flow through porous media, and solitary wave interactions with a porous structure. It is shown that the agreement between experimental and numerical results is generally satisfactory. It is also confirmed that non-hydrodynamic model, SWASH, is computationally much more efficient than the three-dimensional porous flow models based on VOF approach.

Determination of porosity and effective porosity of saturated porous media using a permittivity method in the laboratory (유전율법을 이용한 다공질 매질의 공극률 및 유효공극률의 측정에 관한 연구)

  • 김만일;니시가끼마코토
    • The Journal of Engineering Geology
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    • v.13 no.4
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    • pp.419-428
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    • 2003
  • In order to evaluate groundwater movement and the infiltration of contaminants, such as petroleum products, the determination of porosity and effective porosity is very important. Porosity and effective porosity are important physical parameters that determine the transfer and movement of water and solutes in porous media. Various methods of determining these parameters have been developed, with varying degrees of accuracy and applicability. Most of the existing methods produce static results. They do not produce instantaneous and real time of porosity and effective porosity in a porous media. In this study, we used a new permittivity method called Frequency Domain Reflectometry with Vector analyzer (FDR-V) to determine the porosity and effective porosity of some sand samples in the laboratory. The advantage of the FDR-V method is that it instantaneously determines the temporal variation of dielectric constants of porous media. Then, the porosity and the effective porosity of porous media are computed using well established empirical equations. Results obtained from the FDR-V method compared favorably with results from other permittivity methods such as gravimetric, injection and replacement tests. The ratio of effective porosity to porosity was 85 - 92 %, when FDR-V was used. This value compared favourably with 90 %, which has been usually quoted in previous studies. Considering the convenience and its applicability, the EDR-V permittivity holds a great potential in porous media and contaminant transport studies.

A Study on Measuring Electrical Capacitance to Access the Volumetric Water Content of Simulated Soil

  • Rial, W.S.;Han, Y.J.
    • Agricultural and Biosystems Engineering
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    • v.1 no.1
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    • pp.30-37
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    • 2000
  • Wet porous media representing agronomic soil that contains variable water content with variable electrolyte concentration was measured to study the shape of the curves of the electric double layer capacitance versus frequency (from 10 KHz to 10 MHz. This was done in an attempt to find the lowest practical operating frequency for developing low cost dielectric constant soil moisture probes. Cellulose sponge was used as the porous media. A high frequency electronic bridge circuit was developed for measuring the equivalent network parallel resistance and capacitance of porous media. It appears that the effects of the electric double layer component of the total parallel network capacitance essentially disappear at operating frequencies greater than approximately 25 MHz at low electrolyte concentrations but are still important at 50 MHz at higher concentrations. At these frequencies, the double layer capacitance masks the diffusion region capacitance where true water content capacitance values reside. The general shape of the curve of volumetric water content versus porous media dielectric constant is presented, with an empirical equation representing data for this type of curve. It was concluded that the lowest frequency where dielectric constant values which represent true water content information will most likely be found is between 30 and 50 MHz at low electrolyte concentrations but may be above 50 MHz when the total electrolyte concentration is near the upper level required for most mesophyte plant nutrition.

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An Experimental Study on the Combustion Characteristics with Superadiabatic Combustor in Porous Media (다공성물질을 이용한 초단열 연소장치에서의 연소특성의 실험적 연구)

  • Chae, J.O.;Dobrego, K.V.;Sim, M.S.;Chung, S.C.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.6 no.4
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    • pp.399-405
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    • 1994
  • Beacuse of the energy resources exhaustion, the aggravating environmental air pollution and the smoke phenomena etc., the importance of clean gas fuel compared with liquid fuel is highly considered in recent years. The combustion system which consists of porous media is actively studied as a new method for solving above problems. Therefore, excess enthalpy combustion using porous media was interested by many researchers and investigated through numerical and experimental analysis. In this study, the simplified combustor has the unique combustion characteristics of mixture gas preheated effect using radiative and convective heat energy by changing the flow passage of unburned gas with solenoid valves and has the intensive excess enthalpy phenomena As the result of according to reduce equivalence ratio, flame temperature was remarkably higher than adiabatic flame temperature. This show the ability of super-lean combustion.

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