Abstract

In this work, consideration is given to an aerodynamic concept to boost the filtration in face masks of airborne hygroscopic particles such as those caused by an infected person when coughs or sneezes. Nowadays, increasing the filtration efficiency of face masks implies either increasing the number of crisscrossing fiber layers or decreasing the equivalent hydraulic diameter of the pore, however, both measures are in clear detriment of its breathability. Here, a novel strategy is proposed in which the filtration of an airborne particle is boosted by increasing its diameter. We called properly this concept as the aerodynamic barrier layer. In this concept, a traditional crisscrossing fiber layer is replaced by a parallel rearranged of the fibers in the direction of the flow. This rearrangement will promote central lift forces which will push the particles toward the center of the channel where after clustering they will coalesce resulting in a bigger particle that can be now easily captured by a conventional fiber crisscrossing layer. Utilizing a simplified geometrical model, an expression for the required length of the aerodynamic barrier layer was derived. It is shown that an aerodynamic barrier layer with a length of only a few millimeters can aerodynamically focus water droplets around 1 μm-diameter and the penetration of airborne particles can be reduced up to 55%.

References

1.
Tcharkhtchi
,
A.
,
Abbasnezhad
,
N.
,
Zarbini Seydani
,
M.
,
Zirak
,
N.
,
Farzaneh
,
S.
, and
Shirinbayan
,
M.
,
2021
, “
An Overview of Filtration Efficiency Through the Masks: Mechanisms of the Aerosols Penetration
,”
Bioactive Mater.
,
6
(
1
), pp.
106
122
.10.1016/j.bioactmat.2020.08.002
2.
Yao
,
B. G.
,
Wang
,
Y. X.
,
Ye
,
X. Y.
,
Zhang
,
F.
, and
Peng
,
Y. L.
,
2019
, “
Impact of Structural Features on Dynamic Breathing Resistance of Healthcare Face Mask
,”
Sci. Total Environ.
689
, pp.
743
753
.10.1016/j.scitotenv.2019.06.463
3.
Konda
,
A.
,
Prakash
,
A.
,
Moss
,
G. A.
,
Schmoldt
,
M.
,
Grant
,
G. D.
, and
Guha
,
S.
,
2020
, “
Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks
,”
ACS Nano.
,
14
(
8
), pp.
10742
10743
.10.1021/acsnano.0c04676
4.
Wang
,
N.
,
Cai
,
M.
,
Yang
,
X.
, and
Yang
,
Y.
,
2018
, “
Electret Nanofibrous Membrane With Enhanced Filtration Performance and Wearing Comfortability for Face Mask
,”
J. Colloid Interface Sci.
,
530
, pp.
695
703
.10.1016/j.jcis.2018.07.021
5.
Glasstone
,
S.
, and
Sesonske
,
A.
,
1994
,
Nuclear Reactor Engineering: Reactor Systems Engineering
, 4th ed.,
Springer-Science+Business
, Princeton, NJ.
6.
Saffman
,
P. G.
,
1965
, “
The Lift on a Small Sphere in a Slow Shear Flow
,”
J. Fluid Mech.
,
22
(
2
), pp.
385
400
.10.1017/S0022112065000824
7.
Mei
,
R.
, and
Klausner
,
J.
,
1994
, “
Shear Lift Force on Spherical Droplets
,”
Int. J. Heat Fluid Flow
,
15
(
1
), pp.
62
65
.10.1016/0142-727X(94)90031-0
8.
Jia
,
W.
,
Lin
,
Y.
,
Yang
,
F.
, and
Li
,
C.
,
2020
, “
A Novel Lift-Off Diameter Model for Boiling Droplets in Natural Gas Liquids Transmission Pipelines
,”
Energy Rep.
,
6
, pp.
478
489
.10.1016/j.egyr.2020.02.014
9.
Situ
,
R.
,
Hibiki
,
T.
,
Ishii
,
M.
, and
Mori
,
M.
,
2005
, “
Droplet Lift-Off Size in Forced Convective Subcooled Boiling Flow
,”
Int. J. Heat Mass Transfer
,
48
(
25–26
), pp.
5536
5548
.10.1016/j.ijheatmasstransfer.2005.06.031
10.
Jaksic
,
D.
, and
Jaksic
,
N.
,
2004
, “
The Porosity of Masks Used in Medicine
,”
Tekstilec
,
47
, pp.
301
304
.https://www.researchgate.net/publication/261794330_The_porosity_of_masks_used_in_medicine
11.
Rogers
,
R. R.
,
1976
,
A Short Course in Cloud Physics
,
Permagon
,
Oxford, UK
.
12.
Straub
,
W.
,
Beheng
,
K. D.
,
Seifert
,
A.
,
Schlottke
,
J.
, and
Weigand
,
B.
,
2010
, “
Numerical Investigation of Collision-Induced Breakup of Raindrops. Part II: Parameterizations of Coalescence Efficiencies and Fragment Size Distributions
,”
J. Atmos. Sci.
,
67
(
3
), pp.
576
586
.10.1175/2009JAS3175.1
13.
Legendre
,
D.
, and
Magnaudet
,
J.
,
1997
, “
A Note on the Lift Force on a Droplet or a Drop in a low- Reynolds-Number Shear Flow
,”
Phys. Fluids
,
9
(
11
), pp.
3572
3574
.10.1063/1.869466
14.
Landau
,
L. D.
, and
Lifshits
,
E. M.
,
1959
,
Fluid Mechanics
,
Pergamon Press
,
London, UK
.
15.
Schetz
,
J. A.
, and
Fuhs
,
A. E.
,
1996
,
Fundamentals of Fluid Mechanics
,
Wiley
, Hoboken, NJ, p.
630
.
16.
Hocking
,
L. M.
, and
Jonas
,
P. R.
,
1970
, “
The Collision Efficiencies of Small Drops
,”
Quart. J. R. Soc.
,
96
(
410
), pp.
722
729
.10.1002/qj.49709641013
17.
Tadmor
,
R.
,
2001
, “
The London-Van Der Waals Interaction Energy Between Objects of Various Geometries
,”
J. Phys. Condens. Matter
,
13
(
9
), pp.
L195
L202
.10.1088/0953-8984/13/9/101
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