Experiment Research Of Flow Characteristic In Porous Media

Porous media is applied in industry, agriculture, and all areas of nature. Complex flowin porous media and fluid involves a lot of industrial engineering and natural processes,such as gas adsorption, filtration, combustion, catalytic reactor, hydrological monitoring,etc. The mechanism of the complex flow is not clear, such as flow pattern change,resistance calculation and so on, which brings difficulties to the application of porousmedia in lives and engineering.In this paper, visualization of single-phase flow inside a crystal glass ball packed bedis studied using the particle image velocimetry (PIV) and refractive index matchingtechnique. The experimental section is a cylindrical quartz glass tube with100mm innerdiameter,110mm outer diameter, and250mm high. It was filled with25mm diametercrystal glass ball and pore rate is0.45. The fluid is mixed by65%benzyl alcohol and35%anhydrous ethanol and its refractive index is1.477. The experiment was conducted underatmospheric pressure, liquid flow rate of0.03-2.3m3/h, and Reynolds number range from100to1000.The pore structure of random pecked bed is not isotropic. It can be seen from imagesof the center section: pore structure in different location varies greatly. Size and shape ofthroat interconnected to pore in all directions is different. In addition, a large circulationchannel exists in the central region. channel on the left side appeared obvious. The channelon the right side is very small. The main flow characteristic is determined by this structure.With the increase of Reynolds number, pressure drop gradually increased, and theincrease tendency is nonlinear. In terms of the experimental conditions in this paper, in acertain area (Rep<500), the calculated value of Ergun empirical formula and experimentaldata are very close; but when Rep>1000, the relative deviation between experimentalvalue and calculation value is beyond50%.Vector direction of the flow in the porous media is influenced by viscous force andinertial force and velocity distribution is influenced by pore and throat size together. At low Reynolds number (Rep<130), the flow field vector direction is mainly influenced byviscous force. in the center of the pore, the vector direction is consistent with themainstream direction; on the edges, vector direction changes along with the shape ofporous medium. At high Reynolds number (Rep>220), the vector direction is mainlyinfluenced by the inertial force, and becomes irregular.Comparing the streamline in different Reynolds number, we conclude: when Rep<130,Streamlines are approximately parallel along the pore shape; When130<Rep<220,streamlines begin to interfere with each other and at some point streamlines begin to gatherand gradually develop into small vortex. When Rep>220, vortex flow in porous mediabecomes mature and stable.Finally, comparing the simulation results by Fluent with the experimental results,wefind that k–model can simulate the flow in porous media on qualitative but cannotsimulate such as local characteristics, vortex flow and so on.