Evaluation of resistances to fluid flow in fibrous ceramic medium

Abstract

Ceramic filters have encountered a variety of applications. A knowledge of the fluid dynamics in these devices is essential for an efficient design and operability. Macroscopically, the pressure drop in these systems may be modeled employing Forchheimer's equation, which takes into account two resistances in the porous region: A viscous resistance, important at low flow rates, and an inertial resistance, which plays a major role at high fluid velocities. These resistances, particularly inertial resistance, have been the subject of investigation in recent decades, especially regarding to the inertial one. Fundamental questions concerning their nature and dependence on the material structure and flow regime are still open to debate. In general, as the material structure becomes more complex and, consequently, the flow inside the intricate porous network more chaotic, as in the case of fibrous ceramic materials, the impact of nonlinearities is enhanced. Thus, computational models may be useful resources for the prediction of the system behavior, as well as for the elucidation of the physics involved. In this study, the commercial code ANSYS® CFD (FLUENT®) was applied to predict the pressure drop in a complex microstructured fibrous ceramic filter as a function of the flow rate. The simulated results were validated with experimental data collected in a wind tunnel, where air was used as the working fluid and its superficial velocity was varied in the range of 2.5 × 10-2-1.7 m · s-1 for three porosities (0.50, 0.65 and 0.73) at different temperatures (300 and 973 K). Finally, the validated model was used to assess the effect of varying the resistances (to levels of ±10%, ±20% and ±50%) on the fluid flow.