UNCLASSI FIED
APPENDIX 3
NOTES ON ELECTROSTATIC PRECIPITATOR
By H. d. wmUiovanni
I.
Laws of Motion of Small Particles Subjected to a Force
(a)
A small particle subjected to a force is accelerated through the
Re kdvse
(1)
For spheres k = 377. When the velocity through the medie is such
that the resistive force is equal to the accelerating force, the
acceleration will be zero resulting in a constant velocity termed
the terminal velocity.
(>)
For a spherical particle in a gravitational field
F
=
}
m=5 7 8p
me?
._
=
l< 1] a3 p
The terminal velocity will result when
F
=
1
2
eae Pe
Ror
_
=
a
314 vf
ld pg
ory * 18
(c)
AL
(2)
If the particle acquires an electrical charge and is in an electrical field the force on the particle will be
F
=
QE
The terminal velocity will then be
QE
-_seoOo-
.
(ad)
media
in the surrounding space, the resulting metion through the particles of
the mediaresults in a resistive force to the motion given by Stokes as
37T aH
(3)
For particles of a size approaching the mean free path of sir
mclecules, a correction due to Cunningham is required to account
for the additional velocity caused by the particle accelerating
between impacts.
vs
This is given br
"Stokes
(l+ ky 2)
-;
{=
UNCLASSIFIED
(L)