Droplet Characteristics and Near Nozzle Dispersion of Cold and Thermal Fog

摘要

In an effort to improve application methods for controlling sand flies in desert environments, a hand-held ultra-low volume (ULV) aerosol generator, a truck-mounted ULV aerosol generator, and a hand-held thermal fogger were evaluated. The velocity and temperature of the air and characteristics of droplets generated by these aerosol generators were measured at various distances from the nozzle. The droplet size characteristics were measured for three flow rates each of BVA-13 mineral oil and a mixture of water and non-ionic surfactant with a phase Doppler particle analyzer. Moving 0.9 m away from the nozzle, the velocity of air produced by the two hand-held sprayers decreased to <5 m/s, whereas the truck-mounted sprayer still had an air velocity of 15 m/s. The air produced by truck-mounted cold fogger, thermal fogger, and hand-held ULV applicator was 38, 49.2, and 8.5°C above ambient temperature, respectively. Increases in flow rate, generally, did not affect the droplet size for the two hand-held units; however the droplet size increased as the flow rate increased on the truck-mounted sprayer. For all three aerosol generators, droplet concentration increased with increasing flow rates. Both ULV generators showed an increase in droplet size and a decrease in droplet concentration as the distance from nozzle increased. However, the droplet size decreased and the droplet concentration increased when applied using the thermal fogger.