Operating the Atomizer 4-3
5. To change the aerosol particle size, use a solution of different
concentration. Flush the Atomizer with about 25 cubic
centimeters of solvent and then refill the syringe with the new
solution. (A thorough cleaning—which means disassembling the
Atomizer—is usually unnecessary unless you change from a
high-solute concentration to a low-solute concentration.)
Prepare the Atomizer for operation as done in step 3.
Drying the Aerosol
When generating aerosols from solid solute, the particles coming
out of the Atomizer are still wet and must be dried. Usually, the
aerosol is mixed with a large volume of dry, dilution air. Another
approach is to pass the aerosol through a diffusion dryer
(Figure 4-1). In this device, the aerosol passes through an inner
tube, made of wire screen. The silica gel surrounding the inner tube
maintains a dry atmosphere at the tube’s outer wall and the porous
wall absorbs water vapor as aerosol passes through.
Figure 4-1
Model 3062 Diffusion Dryer
Frequently check the condition of the silica gel around the inner
tube of the Atomizer to make sure the silica gel in the region next to
the screen tube is in active condition, that is, it looks blue. Install
the neutralizer immediately downstream of the diffusion dryer. The
dilution air used to dilute aerosol to the desired concentration must
be completely dry. Use a Swagelok-brand heat-exchanger tee to mix
the aerosol and the dilution air. By using such a tee, the aerosol
can be fed into the center of an annular, clean air stream, and thus
avoid excessive wall losses.
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