Spray Characterization of Aerosol Delivery Systems for Use in Stored Product Facilities

Abstract

HighlightsHandheld sprayers generated larger droplets and wider droplet size distributions than compressed gas sprayers.Sprayers with higher pressure and nozzles with wider spray angle produced smaller droplets.Droplet size distribution influenced spray coverage, mass concentration, deposition, and sprayer efficacy.The handheld sprayers had less spray coverage and efficiency than the compressed gas sprayers.The deposition at different locations was influenced by the volume of the space, aerosol dosage, and spray time.Abstract. Aerosol insecticides, including pyrethrins, can be used as methyl bromide replacements to control stored product insects inside flour mills and rice mills. The effectiveness of aerosol application for insect control requires knowing the spray characteristics of the equipment to be used and understanding factors that influence the effectiveness of insecticide application. The objectives of this study, as part of efforts to optimize aerosol applications, were to evaluate the characteristics of six aerosol delivery systems (two handheld sprayers and compressed gas sprayer systems fitted with two types of manifolds and two types of nozzles), estimate the dispersion and deposition of aerosol in a simulated stored product facility, and determine how the dispersion and deposition are affected by the characteristics of the sprayers. Results showed that the spray systems differed significantly in spray characteristics. The compressed gas sprayers generated significantly smaller droplets, more uniform droplet size distribution, and better spray coverage than the handheld sprayers. The ellipsoidal nozzle produced significantly smaller droplets than the circular nozzle. While the type of manifold had no significant effect on deposition, higher aerosol dosage and spray time resulted in significantly higher deposition. Results of this study will be used to improve spray techniques for stored product insect control, to validate computational fluid dynamics modeling of aerosol application, and to improve testing methods in large-scale spray testing inside commercial facilities. Keywords: APS spectrometer, Droplet size distribution, HELOS KR-Vario, Mass deposition, Spray characteristics, Spray nozzles.