Key Parameters Used in Modeling Pressure Loss of Fibrous Filter Media

Accurate pressure loss modeling of randomly oriented fibrous filter structures over a broad range of solidity requires that one accurately account for the following effects:

1) Fiber crossings and the resulting effective transverse boundary proximity and shape parameters and the fiber dynamic shape factor which all vary with the average solidity.

2) Slip and transition flow effects on small fibers or at low gas densities.

3) Perturbations due to manufacturing processes and multi modal fiber size distributions which cause fiber curvature, random orientation and solidity gradients in both the transverse and axial directions.

Prominent pressure loss models of both the pore and fibrous type have been found lacking in their ability to predict measured pressure loss of randomly oriented fibrous filters made of near uniform size fibers over a broad range of solidity. A mitered cylinder layered screen like pressure loss model is described which is capable of accurately accounting for the effects described.