• Title/Summary/Keyword: Porous Channel

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On Numerical Treatment of Pressure Gradient at the Interface Between a Homogeneous Fluid and a Porous Medium (순수유체와 다공성물질의 경계면에서 압력구배의 수치적 처리에 관하여)

  • Kim I. S.;Nam J. H.;Kim C.-J.
    • Journal of computational fluids engineering
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    • v.4 no.3
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    • pp.28-34
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    • 1999
  • The objective of this study is to present a numerical treatment of the pressure gradient when control volumes are sharing the interface between a homogeneous fluid and a porous medium. Two possible approaches, e.g. linear interpolation and extrapolation, are considered, and they are applied to the case of a steady and two-dimensional curved channel flow which is partially filled with a porous medium. It was found that the linear extrapolation produces a continuous velocity-field at the interface and thus is recommended. On the contrary, the linear interpolation entails a discontinuous velocity field at the interface, thereby warning its use in connection with the Brinkman-Forchheimer-extended Darcy flow model.

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PTV velocity field measurements of flow around a triangular prism located behind a porous fence (다공성 방풍벽 뒤에 놓인 삼각 프리즘 주위 유동의 PTV 속도장 측정)

  • Kim, Hyeong-Beom;Lee, Sang-Jun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.5
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    • pp.708-715
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    • 1998
  • The shelter effect of a porous wind fence on a triangular prism was experimentally investigated in a circulating water channel. A porous fence of porosity .epsilon.=38.5% was installed in front of the prism model. The fence and prism model were embedded in a turbulent boundary layer. The instantaneous velocity fields around the fence and prism model were measured by using the instantaneous velocity fields around the fence and prism model were measured by using the 2-frame PTV(Particle Tracking Velocimetry) system. By installing the fence in front of the prism, the recirculation flow region decreases compared with that of no fence case. The porous fence also decreases the mean velocity, turbulent intensity and turbulent kinetic energy around the prism. Especially, at the top of the prism, the turbulent kinetic energy is about half of that without the fence.

Heat Transfer and Pressure Drop Characteristics of a Horizontal Channel Filled with Porous Media (다공성매질을 삽입한 수평채널의 열전달 및 압력강하 특성)

  • Son, Young-Seok;Shin, Jee-Young;Cho, Young-Il
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.2
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    • pp.244-251
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    • 2009
  • Porous media have especially large surface area per volume, which contain complex fluid passage. If porous media can be applied to cool a CPU or an electronic device with large heat dissipation, it could result in heat transfer enhancement due to the enlargement of the heat transfer area and the flow disturbance. This study is aimed to identify the heat transfer and pressure drop characteristics of high-porosity metal foams in a horizontal channel. Experiment is performed with the various heat flux, velocity and pore density conditions. Permeabilities, which is deduced from Non-Darcy flow model, become lower with increasing pore density. Nusselt number also decreases with higher pore density. High pore density with same porosity case shows higher pressure loss due to the increase of surface area per unit volume. The fiction factor decreases rapidly with increase of Reynolds number in Darcy flow region. However, it converges to a constant value of the Ergun coefficient in Non-Darcy flow region.

Basic Experiment on the Propagation Characteristics of Premixed Flames in Narrow Annular Coaxial Quartz Tubes (좁은 다중 동축 석영관 내부에서의 예혼합 화염의 전파 특성에 대한 기초 실험)

  • Cho, Moon Soo;Baek, Da Bin;Kim, Nam Il
    • Journal of the Korean Society of Combustion
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    • v.18 no.2
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    • pp.1-7
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    • 2013
  • Flame stabilization characteristics of premixed flames in narrow annular coaxial tubes (NACT) were investigated experimentally. The NACT burner was proposed as a model of a cylindrical refractory burner, and it was made of quartz tubes. Flame stabilization conditions affected by the characteristic length of the burner was investigated with the variation of the equivalence ratio and the flow rates. Flame behaviors in narrow spaces could be directly observed. Conclusively, more wide flame stabilization conditions could be obtained at the case of the decreased channel scale. A flame instability, such as combustion noise was detected concerned with the flame oscillation observed at the surface of multi channel stage. Some flame propagation characteristics had complicated tendencies that may exist in practical porous-media combustors. Therefore, this NACT burner can be a basic configuration for the development of flame stabilization model in porous media combustor, and it will enhance our understanding about the behavior of flames in meso-scale combustion spaces.

Heat Transfer Characteristics depending on the Length of a Channel with Pin-Fin Array (핀-휜을 삽입한 채널의 길이에 따른 열전달 특성 변화)

  • Son, Young-Seok;Shin, Jee-Young;Lee, Sang-Rog
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.19 no.5
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    • pp.418-425
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    • 2007
  • The power consumption and heat generation in a chip increase as the components are miniaturized and the computing speed becomes faster. Therefore, suitable heat dissipation has become one of the primary limiting factors to ensure the guaranteed performance and reliable operation of the electronic devices. A pin-fin array which may be considered as a porous medium could be used as an alterative cooling system of the electronic equipment. The aim of the present study is to investigate the forced-convective heat transfer characteristics of pin-fin heat exchangers. Convective heat transfer through the pin~fin array is analyzed experimentally based on porous medium approach. The influence of the structure of the pin-fin array including the pin-fin spacing, the pin diameter and plate length on heat transfer characteristic is investigated and compared with the Previous analytical results and existing correlation equations. Nowadays, electronic and mechanical devices become smaller and smaller. In this sense, the main purpose of this study is to decide the optimum pin-fin arrangement to get similar heat transfer performance when the length of the existing cooling system is reduced as a half.

Development Study of Mono-Propellant Micro Propulsion Using MEMS Technology

  • Dan, Yoichiro;Kishida, Masahiro;Ikuta, Tatsuya;Takahashi, Koji
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.597-600
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    • 2004
  • Fabrication technique and performance test of catalytic micro propulsion are treated based on MEMS technology. This propulsion is designed to use hydrogen peroxide as liquid mono-propellant for attitude control of pica-satellite. The propellant is fed into the micro reactor channel and decomposed into hot gas yielding controllable thrust by catalyst. In order to increase the efficiency of the reaction that depends on the contact area of propellant and catalyst, porous surface formation on the channel accompanied by platinum particle deposition has been performed using H$_2$PtCl$_{6}$ solution as a precursor. Several thrusters were fabricated in different concentration of H$_2$PtCl$_{6}$ solution to determine the best quantity of Pt particles. For the comparison of the performance of each thruster, the volume of oxygen generated by the decomposition of hydrogen peroxide and the thrust were measured.red.

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Analysis on the Cooling Characteristics of a Channel with Pin-Fin Structure (핀-휜 구조물을 이용한 채널의 냉각특성 해석)

  • 신지영;손영석;이대영
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.8
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    • pp.667-673
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    • 2003
  • Recent trends in the electronic equipment indicate that the power consumption and heat generation in a chip increase as the components are miniaturized and the computing speed becomes faster. Suitable heat dissipation is required to ensure the guaranteed performance and reliable operation of the electronic devices. The aim of the present study is to investigate the forced-convective thermal-hydraulic characteristics of a pin-fin heat exchanger as a candidate for cooling system of the electronic devices. The influence of the structure of the pin-fin assembly on heat transfer is investigated by porous medium model. The results are compared with the experimental data or correlations of several researchers for the heat transfer coefficients for the channel flow with pin-fin arrays. Finally, the effects of design parameters such as the pin-fin diameter and the spacing are examined.

The Flow Analysis of Virtual Channel depending upon the change of two ingates

  • Kim, Nam-Hyeong;Kim, Gyeong-Bo
    • Proceedings of the Korea Water Resources Association Conference
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    • 2006.05a
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    • pp.1636-1640
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    • 2006
  • SMAC method, one of the computational fluid dynamics techniques, is modified from the original MAC method for the time-dependent variation of flow analysis. The Navier-Stokes equations for incompressible time-dependent viscous flow are applied, and also marker particles that present the visualization of flow analysis are used. In this study SMAC technique is used to analyze the flow behavior in the water-filling of virtual channel. Then by changes of diameter of two ingates, the change of velocity and discharge when two ingates are filled the water to virtual channel are simulated. As a result, water-filling flow pattern in the virtual channel is simulated very well. Therefore, this numerical simulation will also be applied for the design of structures as open flume and porous breakwater.

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Methane carbon dioxide reforming for hydrogen production in a compact reformer - a modeling study

  • Ni, Meng
    • Advances in Energy Research
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    • v.1 no.1
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    • pp.53-78
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    • 2013
  • Methane carbon dioxide reforming (MCDR) is a promising way of utilizing greenhouse gas for hydrogen-rich fuel production. Compared with other types of reactors, Compact Reformers (CRs) are efficient for fuel processing. In a CR, a thin solid plate is placed between two porous catalyst layers to enable efficient heat transfer between the two catalyst layers. In this study, the physical and chemical processes of MCDR in a CR are studied numerically with a 2D numerical model. The model considers the multi-component gas transport and heat transfer in the fuel channel and the porous catalyst layer, and the MCDR reaction kinetics in the catalyst layer. The finite volume method (FVM) is used for discretizing the governing equations. The SIMPLEC algorithm is used to couple the pressure and the velocity. Parametrical simulations are conducted to analyze in detail the effects of various operating/structural parameters on the fuel processing behavior.

Microstructure Control of HAp Based Artificial Bone Using Multi-extrusion Process

  • Jang, Dong-Woo;Lee, Byong-Taek
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.05a
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    • pp.54.1-54.1
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    • 2011
  • Porous hydroxyapatite has been widely used as clinical implanted material. However, it has poor mechanical properties. To increase the strength as well as the biocompatibility of the porous HAp based artificial bone, it was fabricated by multi-extrusion process. Hydroxyapatite and graphite powders were mixed separately with ethylene vinely acetate and steric acid by shear mixing process. Hydroxyapatite composites containing porous microstructure were fabricated by arranging it in the die and subject it to extrusion process. Burn-out and sintering processes were performed to remove the binder and graphite as well as increase the density. The external and internal diameter of cylindrical hollow core were approximately 10.4 mm and 4.2 mm, respectively. The size of pore channel designed to increase bone growth (osteconduction) was around 150 ${\mu}m$ in diameter. X-ray diffraction analysis and SEM observation were performed to identity the crystal structure and the detailed microstructure, respectively.

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