TSI Instruments 3079A, Operation And Service Manual, Page: 22 / 39

Chapter 5
5-4 Model 3079A
Generation of Tracer Particles
The continuous and stable generation of particles is important when using optical methods for
measuring flow velocities and distributions. The Model 3079A meets these requirements and makes it
also suitable for tracer particle generation.
Generation of Salt Aerosols
The Model 3079A Atomizer Aerosol Generator is also suitable for salt aerosol production. The
resulting particle size d
p
depends on the droplet size generated by the atomizer d
d
and can be varied
by altering the salt solution concentration c according to the following equation:
√
In the diagram below, a calculated particle size distribution for a salt solution with a concentration of
200 ppm (e.g. 200 mg NaCl/1l H
2
O) is shown and compared with the droplet particle size distribution
of water which has been characterized by means of the
“residual technique.”
The residual technique is very useful for characterizing droplet distributions of water, for instance,
which evaporates very quickly under normal conditions. In this method the produced droplet aerosol is
completely dried and the residual distribution is measured afterwards. From this residual distribution
the droplet distribution can be recalculated using the given equation.
0%
20%
40%
60%
80%
100%
0,01 0,1 1 10 100
Particle diameter, µm
C
u
m
u
la
ti
v
e
m
a
s
s
d
is
tr
ib
u
ti
o
n
Calculated distribution of
a 200ppm NaCl-solution
measured
primary droplet size
distribution for H
2
O
Figure 7 : Recalculated Size Distribution
Note : If liquids like water are atomized over longer periods (>1hour), the equipment connected to the
Model 3079A cools down below the saturation temperature. In this case, droplets will
inevitably condense again. It is recommended to use a diffusion dryer and heat the connected
aerosol tubes for such applications.