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Modeling of aerosol particles collected in swirling sampler with re-circulating liquid film.
Sigaev GI; Tolchinsky AD; Sigaev VI; Soloviev KG; Varfolomeev AN; Bean CT
J Aerosol Sci 2004 Jul; 35(Suppl 1):S409-S410
One of the factors that ensure efficient control of the airborne microflora is the use of methods allowing for gentle sampling to sustain specific morphological and physiological properties of the microbes under control. According to Henningson and Ahlberg (1994) the most promising device in this respect is liquid absorptive samplers which provide precise detel1oInation of airborne microbes due to disintegration of aerosol particles-carriers into single cells and application of special absorptive liquids containing the components that ensure sustaining of the microbes viability. In liquid aerosol samplers a bubbling mode of airflow intake and liquid interaction is commonly used. At that, in thin films in the point of the air bubbles touch, high shear tensions leading to considerable inactivation of the settled bioagent occur. This is considered to be the main deficiency of such-type devices. At the tangent settling of particles on the water film in the centrifugal field provided are minimal shear tensions on aerosol particles and thus minimal inactivation of bioaerosol. Another critical condition for sustaining of the collected bioagent sample is laminar motion of liquid while circulating in the sample. These conditions are realized in a swirl sampling device. It is based on the principle of producing a rotating liquid film on the inner side of the settling cyclone by using the energy of the sucked-In from outside airflow. With this aim the inlet nozzle of the sampler is inserted into the cyclone in such a way that its long axis is tangentially located with regard to the cross cyclone plane. The air vortex twisted along the cyclone perimeter has three speed vector components: tangential, centrifugal (radial) and vertical, which taken together move the vortex in a stable spiral manner. The vortex produces a negative pressure difference in the cyclone center and in the area from the cut bottom edge of the nozzle to the cyclone bottom. Due to this difference a continuous suction of absorptive liquid from the liquid reservoir located at the bottom of sampler via axial cyclone connecting pipe, as well as its rising along the cylinder wall; thinning in the form of the helix-moving film; and flowing over the upper cut of the cyclone. Under specific conditions laminar manner of the film moving along the cyclone surface and its overflow is achieved. Centrifugal forces cause aerosol particles from the airflow to mechanically settle on the liquid film surface. Since the trajectory of the moving particles is nearly tangential to the film surface, it provides a gentler mode of bioagent sustaining. In addition, application of the mode of continuous recirculation of absorptive liquid in the sampler cyclone increases the coefficient of its volume use during sampling and ensures a longer possible interval of taking samples compared to the known liquid samplers (Sigaev et al, 2001).
Models; Aerosols; Aerosol-particles; Aerosol-sampling; Mathematical-models; Airborne-particles; Airborne-dusts; Samplers; Sampling; Sampling-methods; Author Keywords: Bioaerosols; Swirling Cyclone; Mathematical Model; Particle Capturing Efficiency; Experimental Measuring
Journal of Aerosol Science
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division