• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.37-46
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• 2013

The gas jet from a coaxial porous injector for two-phase flows is discharged radially from the porous surface, which encloses the center liquid jet. Several hot-firing test using ethanol/nitrous oxide propellants was conducted to analyze the effect of oxidizer/fuel ratio on the combustion performance, and the uncertainty analysis was performed for the results. The characteristic velocity was affected by oxidizer/fuel ratio similarly with the results of CEA calculation except that the maximum characteristic velocity was appeared in the stoichiometric ratio. The characteristic velocity efficiency was increased as the oxidizer/fuel ratio increases.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.260-263
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• 2005

The effects of internal manifold designs the reactant feed-stream in Polymer Electrolyte Fuel Cells (PEFCs) is studied to figure out mass flow-distribution patterns over an entire fuel cell stack domain. Reactants flows are modeled either laminar or turbulent depending on regions and the open channels in the bipolar plates are simulated by porous media where permeability should be pre-determined for computational analysis. In this work, numerical models for reactant feed-stream in the PEFC manifolds are classified into two major flow patterns: Z-shape and U-shape. Several types of manifold geometries are analyzed to find the optimal manifold configurations. The effect of heat generation in PEFC on the flow distribution is also investigated applying a simplified heat transfer model in the stack level (i.e. multi-cell electrochemical power-generation unit). This modeling technique is well suited for many large scale problems and this scheme can be used not only to account for the manifold flow pattern but also to obtain information on the optimal design and operation of a PEMC system.

• New & Renewable Energy
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• v.1 no.2 s.2
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• pp.41-52
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• 2005

The effects of internal manifold designs on the reactants feed-stream in Polymer Electrolyte Fuel Cells [PEFCs] is studied to figure out flow and thermal distribution patterns over an entire fuel cell stack. Reactants flows are modeled either laminar of turbulent depending on regions and the open channels in the bipolar plates are simulated by porous media where permeability should be pre-deter-mined for computational analysis. In this work, numerical models for reactants feed-stream In the PEFC manifolds are classified Into two major flow patterns: Z-shape and U-shape. Several types of manifold geometries are analyzed to find the optimal manifold configurations. The effect of heat generation in PEFC on the flow distribution is also Investigated applying a simplified heat transfer model in the stack level (i.e. multi-cell electrochemical power-generation unit). This modeling technique Is well suited for many large scale problems and this scheme can be used not only to account for the manifold flow pattern but also to obtain Information on the optimal design and operation of PEFC systems.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.139-145
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• 2009

An analytical solution of groundwater flow is applied to design soil vacuum extraction for removing volatile organic compounds from the unsaturation zone. The governing equation of gas or vapor flow in porous media is nonlinear in that gas density depends on gas pressure. A linear equation suggested by researcher is similar to that of groundwater flow. The pressure drawdowns of confined and leaky aqufiers are calculated using Massmann's field data, and the pressure drawdowns are compared. A solution of Theis equation calculated by Massmann is modified using GASSOLVE9 program in this paper. The pressure drawdown using Hantush's analytical solution for leaky aquifer also compared to that of Massmann. Hantush's analytical solution gives good approximations to pressure drawdown.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.67-74
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• 2012

A numerical analysis was carried out to estimate the effect of the gap size ratio on the performance of condensers under noncondensable gas ventilation using the porous medium approach (PMA). In the PMA, the details of the tube bundle in the condenser are considered to be those of a porous medium, and the flow resistance term is added in the momentum equation. Three-dimensional analysis of the condensation for a McAllister condenser was conducted with the PMA using Fluent and user-defined functions (UDFs). The gap size effect on the condensation was negligible under pure steam conditions. However, the gap size effect was dominant in condensation with noncondensable gas and external venting. As the gap size decreased, the condensation rate increased for noncondensable gas in an external venting system.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.191-194
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• 2003

In this study, permeability tensor is computed for a three dimensional braided preform by applying a FVM to a unit cell. It is evident that resin will flow through the inter-tow and the intra-tow regions when pressure gradient is applied to the resin. The intra-tow region in the braided preform is regarded as not only an impermeable solid but also a permeable porous media. When the intra-tow region is excluded from domain of flow analysis in the case of the impermeable solid, the Stokes equation is computer for only inter-tow region. (omitted)

• Geomechanics and Engineering
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• v.9 no.4
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• pp.465-481
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• 2015

Three-dimensional simulation of flow through dam foundation is performed using finite element (Seep3D model) and artificial neural network (ANN) models. The governing and discretized equation for seepage is obtained using the Galerkin method in heterogeneous and anisotropic porous media. The ANN is a feedforward four layer network employing the sigmoid function as an activator and the back-propagation algorithm for the network learning, using the water level elevations of the upstream and downstream of the dam, as input variables and the piezometric heads as the target outputs. The obtained results are compared with the piezometric data of Shahid Abbaspour's Dam. Both calculated data show a good agreement with available measurements that demonstrate the effectiveness and accuracy of purposed methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.569-569
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• 2014

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. This paper presents a numerical analysis method for a simplified vehicle model. The internal air cavity including trim component are included in the simulation. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using CFD Code. The second step consists in the computation of the vibro-acoustic transmission through the window using the finite element vibro-acoustic solver Actran.

• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.71-76
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• 2006

Porous polymer monolithic columns were prepared by the direct free radical copolymerization of methacrylic acid and ethylene glycol dimethacrylate within the confines of a chromatographic column in the presence of toluene-dodecanol as a porogenic solvent. The separation characteristics of the monolithic columns were tested by a homologous series of xanthine derivatives, theophylline and caffeine. The effects of the polymerization mixture composition and polymerization condition, mobile phase composition, flow rate and temperature on the retention times and separation efficiencies were investigated. The results showed that the selection of correct porogenic solvents and appropriate polymerization conditions are crucial for the preparation of the monolithic stationary phases. The separation efficiency was only extremely weakly dependent on flow rate and temperatures. Hydrogen-bonding interaction played an important role in the retention and separation. Compared with conventional particle columns, the monolithic column exhibited good stability, ease of regeneration, high separation efficiency and fast analysis.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.112-117
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• 2024

Numerical simulations on the onset and the growth of viscous fingering during the miscible displacement due to the radial source flow were conducted. With introduction of a new stability criterion, the critical log-viscosity ratio, R_c, was found as a function of the Peclet number, Pe. Similar to the previous linear stability analyses, Pe made the system unstable, i.e., accelerated the onset of instability. For a large Pe system, the present numerical simulation yielded much stable results than the previous theoretical predictions This discrepancy was commonly encountered in the comparison between the theoretical prediction and the experimental finding. Additionally, the difference between the rectilinear system and the present one was also discussed. The present system was found more insensitive to the Peclet number than the rectilinear one.