Experimental and Numerical Investigations of Air Flow Characteristics Through Microporous Media

2006 ◽  
Author(s):  
Ruina Xu ◽  
Peixue Jiang
Keyword(s):  
Experimental Data ◽  
Porous Media ◽  
Flow Regime ◽  
Air Flow ◽  
Slip Flow ◽  
Particle Diameter ◽  
Flow Characteristics ◽  
Average Particle ◽  
Friction Factors ◽  
Slip Flow Regime

The effect of particle diameter on the air flow characteristics in various micro-porous media test sections was studied experimentally and numerically. The test sections were made of bronze particles with average diameters of 200 μm, 125 μm, 90 μm and 40 μm. The experimentally measured friction factors in the porous media with average diameters of 200 μm and 125 μm agree well with the known correlation. However, the experimental values for the friction factors in the micro-porous media with 90 μm a and 40 μm average diameters are much less than the known correlation. Also, the differences between the experimental results and the known correlation increase with decreasing average particle diameter. Numerical simulations of the air flow in micro-porous media including rarefaction were performed using the CFD code FLUENT 6.1 to predict the pressure drop characteristics in the four test sections. The calculated friction factors for the non-slip flow regime in the micro-porous media agree well with the known correlation and the experimental data. The numerically predicted friction factors for the slip flow regime in the micro-porous media with 90 μm and 40 μm diameter particles were less than the known correlation and close to the experimental data. The results show that rarefaction effects occur in air flows in the micro-porous media with particle diameters less than 90 a and that numerical calculations with velocity slip on the boundary can simulate the slip flows in micro-porous media.

A fractal model for gas slippage factor in porous media in the slip flow regime

2013 ◽  
Vol 87 ◽  
pp. 209-215 ◽  
Author(s):  
Qian Zheng ◽  
Boming Yu ◽  
Yonggang Duan ◽  
Quantang Fang
Keyword(s):  
Porous Media ◽  
Flow Regime ◽  
Slip Flow ◽  
Fractal Model ◽  
Gas Slippage ◽  
Slip Flow Regime

Microscale Flow Through Channels With a Right-Angled Bend: Effect of Fillet Radius

2008 ◽  
Vol 130 (10) ◽  
Author(s):  
V. Raghavan ◽  
B. Premachandran
Keyword(s):  
Flow Regime ◽  
Knudsen Number ◽  
Pressure Ratio ◽  
Slip Flow ◽  
Flow Characteristics ◽  
Velocity Profiles ◽  
Exit Velocity ◽  
Fillet Radius ◽  
Flow Through ◽  
Slip Flow Regime

Microscale gas flow through channels with a right-angled bend has been numerically analyzed to study the effect of the fillet radius on flow characteristics. The flow is assumed to be incompressible, laminar, and hydrodynamically developing. The fillet radius has been varied from zero, representing a sharp corner, to 0.6 times the height of the channel. The Knudsen number has been varied from zero, representing no-slip at the boundary, to 0.1, which is the limiting case for the slip-flow regime. A low Reynolds number of value 1 has been considered in the present study, which makes the flow to be within the incompressible slip-flow regime. The flow characteristics in terms of velocity profiles, velocity vectors, and the pressure ratio between the inlet and outlet of the channel have been presented for several cases. Results show that for the case of the fillet radius equal to zero, the flow separation occurs after the bend and due to this, the exit velocity profile changes significantly. The highest pressure ratio between the inlet and the outlet is required to maintain a specific mass flow rate for this case. The cases with a nonzero fillet radius exhibit exit velocity profiles identical to that of a straight channel. The pressure ratio decreases when the fillet radius and the Knudsen number are increased.

Flow Characteristics and Convection Heat Transfer in Microporous Media

2008 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Rui-Na Xu ◽  
Chen-Ru Zhao
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Porous Media ◽  
Slip Flow ◽  
Convection Heat Transfer ◽  
Flow Characteristics ◽  
Flow In Porous Media ◽  
Convection Heat ◽  
Microporous Media ◽  
Internal Convection

The flow characteristics of water and air in micro porous tubes with average diameters of 200 μm ∼ 10 μm were studied experimentally and numerically. The results showed that compressibility significantly influence the air flow in porous media with the particle diameters of 200 μm ∼ 10 μm, which increases the friction factor in porous media. Rarefaction effects occur in air flows in the microporous media with particle diameters less than 90 μm. New correlations for K and F were proposed with consideration of Kn. The numerically predicted friction factors for the slip-flow regime in the micro-porous media with 90 μm ∼ 10 μm diameter particles were less than the known correlation and close to the experimental data. The internal convection heat transfer coefficients between particles and fluid in the micro porous media were determined experimentally and numerically. The experimental data for the micro porous media with particle diameters of 20 and 10 μm are much lower than the previously published results. A new correlation for Nusslet number was proposed with consideration of the influence of Kn. Numerical calculation with consideration of slip-flow and temperature jump in micro porous media can properly simulate internal convection heat transfer.

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