Dynamic Shape Factor of a Plate-Like Particle

Abstract

Talc aerosol particles found in work environments have plate-like shapes. These particles are difficult to characterize by their physical dimensions or their aerodynamic behavior. This paper describes a detailed study of the physical and aerodynamic properties of a commercial-grade, respirable talc aerosol and establishes a relationship between the projected area diameter (D _p) and the aerodynamic resistance diameter (D _ar) The measured bulk density was 3.04 g/cm³. Electron micrographs showed that the particles were plate-like with a fairly constant thickness-to-diameter ratio of 0.096. The aerosol was aerodynamically separated in an aerosol centrifuge, and was collected flat on the substrate. The dynamic shape factor of the size-classified talc particle was calculated to be 1.88, which is in good agreement with the theory based on an oblate spheroid moving with its short axis parallel to the flow. The aerodynamic resistance diameter (D _ar) was linearly related to the projected area diameter (D _p) by the relationship (D = 0.67 where C(D _a) is the slip correction factor based on the adjusted sphere diameter (D _a = 1.21D _p).