AIRBORNE SPRAY COLLECTION EFFICIENCY OF NYLON SCREEN

Abstract

Nylon filter screens of several porosities and fiber sizes were evaluated for effectiveness in collecting spray droplets.Droplets with volume median diameters of 30 and 44 .m, transported by air speeds of 2, 4, and 6 m/s (4.5, 8.9, and13.4 mph), were used. Collection efficiency of the best screen was compared to string and plastic tapes of several widths. Thisscreen appeared to be nearly as efficient as strings and much better than plastic tapes, based on collection efficiency per unitfrontal area. Total spray collected on an array of screens was compared to the total spray emitted from the air atomizingnozzles. Results were compared with the classic results of May and Clifford (1967). The screen collection efficiency was about120% for 30-.m droplets and 140% for 44-.m droplets, using calculation methods similar to those of May and Clifford. Airvelocities were measured with no screens and behind single screens, for a wind tunnel speed of 4 m/s and a nozzle air pressureof 138 kPa (20 psi). Air speed behind screens with a porosity of 39% was about 50% of air speed behind screens with 53%porosity.