# Fibrous filter efficiency and pressure drop in the viscous-inertial transition flow regime.

## Abstract

Fibrous filter pressure drop and aerosol collection efficiency were measured at low air pressures (0.2 to 0.8 atm) and high face velocities (5 to 20 meters per second) to give fiber Reynolds numbers in the viscous-inertial transition flow regime (1 to 16). In this regime, contemporary filtration theory based on Kuwabara's viscous flow through an ensemble of fibers under-predicts single fiber impaction by several orders of magnitude. Streamline curvature increases substantially as inertial forces become dominant. Dimensionless pressure drop measurements followed the viscous-inertial theory of Robinson and Franklin rather than Darcy's linear pressure-velocity relationship (1972). Sodium chloride and iron nano-agglomerate test aerosols were used to evaluate the effects of particle density and shape factor. Total filter efficiency collapsed when plotted against the particle Stokes and fiber Reynolds numbers. Efficiencies were then fitted with an impactor type equation where the cutpoint Stokes number and a steepness parameter described data well in the sharply increasing portion of the curve (20% to 80% efficiency). The cutpoint Stokes number was a linearly decreasing function of fiber Reynolds number. Single fiber efficiencies were calculated from total filter efficiencies and compared to contemporary viscous flow impaction theory (Stechkina et al. 1969), and numerical simulations from themore »

- Authors:

- Publication Date:

- Research Org.:
- Sandia National Laboratories

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 1030245

- Report Number(s):
- SAND2011-6940C

TRN: US201124%%43

- DOE Contract Number:
- AC04-94AL85000

- Resource Type:
- Conference

- Resource Relation:
- Conference: Proposed for presentation at the American Association of Aerosol Research Conference held October 3-7, 2011 in Orlando, FL.

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 54 ENVIRONMENTAL SCIENCES; AEROSOLS; AIR; EFFICIENCY; FIBERS; FILTRATION; IRON; METERS; PRESSURE DROP; REYNOLDS NUMBER; SHAPE; SODIUM CHLORIDES; TRANSITION FLOW; VISCOUS FLOW

### Citation Formats

```
Sanchez, Andres L., Brockmann, John E., Dellinger, Jennifer Gwynne, Lucero, Daniel A., Hubbard, Joshua A., and Servantes, Brandon Lee.
```*Fibrous filter efficiency and pressure drop in the viscous-inertial transition flow regime.*. United States: N. p., 2011.
Web.

```
Sanchez, Andres L., Brockmann, John E., Dellinger, Jennifer Gwynne, Lucero, Daniel A., Hubbard, Joshua A., & Servantes, Brandon Lee.
```*Fibrous filter efficiency and pressure drop in the viscous-inertial transition flow regime.*. United States.

```
Sanchez, Andres L., Brockmann, John E., Dellinger, Jennifer Gwynne, Lucero, Daniel A., Hubbard, Joshua A., and Servantes, Brandon Lee. Sat .
"Fibrous filter efficiency and pressure drop in the viscous-inertial transition flow regime.". United States.
```

```
@article{osti_1030245,
```

title = {Fibrous filter efficiency and pressure drop in the viscous-inertial transition flow regime.},

author = {Sanchez, Andres L. and Brockmann, John E. and Dellinger, Jennifer Gwynne and Lucero, Daniel A. and Hubbard, Joshua A. and Servantes, Brandon Lee},

abstractNote = {Fibrous filter pressure drop and aerosol collection efficiency were measured at low air pressures (0.2 to 0.8 atm) and high face velocities (5 to 20 meters per second) to give fiber Reynolds numbers in the viscous-inertial transition flow regime (1 to 16). In this regime, contemporary filtration theory based on Kuwabara's viscous flow through an ensemble of fibers under-predicts single fiber impaction by several orders of magnitude. Streamline curvature increases substantially as inertial forces become dominant. Dimensionless pressure drop measurements followed the viscous-inertial theory of Robinson and Franklin rather than Darcy's linear pressure-velocity relationship (1972). Sodium chloride and iron nano-agglomerate test aerosols were used to evaluate the effects of particle density and shape factor. Total filter efficiency collapsed when plotted against the particle Stokes and fiber Reynolds numbers. Efficiencies were then fitted with an impactor type equation where the cutpoint Stokes number and a steepness parameter described data well in the sharply increasing portion of the curve (20% to 80% efficiency). The cutpoint Stokes number was a linearly decreasing function of fiber Reynolds number. Single fiber efficiencies were calculated from total filter efficiencies and compared to contemporary viscous flow impaction theory (Stechkina et al. 1969), and numerical simulations from the literature. Existing theories under-predicted measured single fiber efficiencies although the assumption of uniform flow conditions for each successive layer of fibers is questionable; the common exponential relationship between single fiber efficiency and total filter efficiency may not be appropriate in this regime.},

doi = {},

journal = {},

number = ,

volume = ,

place = {United States},

year = {2011},

month = {10}

}