|
No. 8
Laskin Nozzle Aerosol Concentration
The purpose of this bulletin is to summarize
the basics of concentration expected from a Laskin Nozzle
aerosol generator, which includes the ATI Models TDA-4B, 4Blite
& 6C.
The standard Laskin III-A Nozzle has four jets
located beneath four entraining holes. The volume of compressed
air required to produce a given amount of aerosol depends on the
pressure of compressed air applied to the nozzle.
The original design research was conducted by Echols
and Young of the Naval Research Laboratory. This information
is covered in Naval Research Laboratory
Report #5929, dated 26 July 1963. Using this report and it's Appendix, the concentration versus pressure
of the Laskin Nozzle can be extrapolated. Using the report information, it can be shown that when 20 psig is applied to the nozzle and diluted with 135 cfm of
air, the output of one Laskin Nozzle provides a concentration
of 100 micrograms per liter. The data also indicates that
each nozzle requires 2.67 cfm of compressed air to maintain the 20 psig pressure drop.
Over the years, the impression has been that
the only way the Laskin Nozzle Generator can be used is by
applying 20 psig to the nozzle. According to the Echols &
Young Report, as you increase the pressure, the concentration
increases and as you decrease the pressure, the concentration
decreases. Further studies by Dr. Melvin First at the Harvard
School of Public Health and Wendell Anderson at the Naval
Research Laboratory have shown that by varying the pressure
up and down on the Laskin Nozzle, the aerosol size distribution
is not significantly affected. Wendell Anderson has also concluded that
two of the jet holes may be plugged to obtain half of the
standard concentration. Also, if three jets are plugged the concentration
drops to one-fourth of the standard output concentration. This information
is useful for customers who want to test air filtration systems
that operate at lower than 135 cfm and other special low flow applications.
Detailed information on the Laskin Nozzle
and its use is available in Section 8 of the U.S. Department
of Energy, Nuclear
Air Cleaning Handbook. Dr. First's reference is available
in the American Industrial Hygiene Association's 1983 Journal,
Pages 495 - 500.
ATI presented a paper to the Institute of
Environmental Sciences (IEST) in 1993 which confirmed that
the liquid level did not have significant effect on aerosol
concentration. This data begins on Page 559 of the 1993 IEST
Proceedings, Volume I.
|
