Determination of the flow rate characteristics of porous media under the positive pressure and vacuum

Porous media is widely used to replace the conventional orifices as restrictors in vacuum handling process. In this study, a theoretical model describing the flow rate characteristics, including effects from both viscosity and inertia, is established based on Darcy-Forchheimer's law. The simulation work is firstly conducted, followed by establishing apparatuses to determine permeability and inertial coefficients. The permeability is determined within a small pressure difference (< 2 kPa) and the inertial coefficient is obtained with Re > 0.1 as the boundary. The average permeability is 1.21 × 10-12 m2, 1.56 × 10-12 m2, 3.41 × 10-12 m2 and 12.21 × 10-12 m2, respectively. The inertial coefficient is determined under the positive pressure at the maximum pressure difference and vacuum with pressure difference from 50 kPa to 70 kPa. For different pressure conditions, it is confirmed that the theoretical flow rate can predict the experimental data within a 3% uncertainty, which is sufficient for most applications. Finally, to obtain the inertial coefficient, two methods including the single-point method and the multi-point method are proposed. We found that the single-point method gives an error of 3.1% while the multi-point method gives an error of 1.9% for the determination of the entire flow rate characteristics.