Development of a high-volume air sampler for nanoparticles

Abstract

As a tool to evaluate the characteristics of aerosol nano-particles, a high-volume air sampler for the collection of nano-particles was developed based on the inertial filter technology. Instead of the webbed fiber geometry of the existing inertial filter, wire mesh screens alternately layered using spacing sheets with circular holes aligned to provide multi-circular nozzles were newly devised and the separation performance of the filter was investigated experimentally. The separation performance was evaluated for a single-nozzle inertial filter at different filtration velocities. A webbed stainless steel fiber mat attached on the inlet surface of the developed inertial filter was discussed as a pre-separator suppressing the bouncing of particles on meshes. The separation performance of a triple-nozzle inertial filter was also discussed to investigate the influence of scale-up on the separation performance of a multi-nozzle inertial filter. The influence of particle loading on the pressure drop and separation performance was discussed. A supplemental inlet for the nano-particle collection applied to an existing portable high-volume air sampler was devised and the consistency with other types of existing samplers was discussed based on the sampling of ambient particles. The layered-mesh inertial filter with a webbed stainless steel fiber mat as a pre-separator showed good performance in the separation of particles with a d p50 ranging from 150 to 190 nm keeping the influence of loaded particles small. The developed layered-mesh inertial filter was successfully applied to the collection of particles at a d p50∼ 190 nm that was consistent with the results from existing samplers.

Development of a Sharp-Cut Inertial Filter Combined with an Impactor

“…In both figures, the collection efficiency curve for layered mesh inertial filter combined with a stainless steel fiber matt is shown for comparison. The cut-off size d p50 is ~190 nm at u = 17.0 m s -1 and the collection efficiency of the layered mesh inertial filter were in good agreement with previous data obtained for ambient particles (Hata et al, 2013a). The collection efficiency of particles larger than ~400 nm decreased due to the bouncing effect at large velocities.…”

“…400-550 L min -1 . The layered-mesh inertial filter showed good performance when a webbed SUS fiber mat was used as a pre-separator, which reduced the bouncing effect of particles larger than 300 nm (Hata et al, 2013a). However, the characteristics of the inertial filter are rather similar to those of an air filter and the separation curve lacks steepness.…”

“…The separation performance of the proposed type inertial filter was tested for single nozzle geometry taking into account the scale up ability shown for the multi-nozzle type using the same nozzle (Hata et al, 2013a). Separation efficiency curves and pressure drop for a layered mesh inertial filter, an impactor and an impactor combined layered mesh inertial filter were compared.…”

“…5-circular wire mesh screens (a) were sandwiched by 6-spacers (b) and were held tightly in the holder to produce a single nozzle inertial filter. For the uniform layered mesh structure projected in the flow direction (Hata et al, 2013a), wire mesh screens were aligned tangentially uniform in order to maximize the coverage of the nozzle cross section by the mesh wires. The impactor (c) is connected upstream of the filter holder when the performance of the hybrid inertial filter was evaluated.…”

“…A layered mesh inertial filter using TEM grids as wire mesh was used in the case of a small flow rate (5-6 L min -1 ) and was successfully applied to a personal sampler (Thongyen et al, 2015). For a high volume flow rate, a multi nozzle layered mesh inertial filter was developed using screen wire mesh sandwiched between spacers with circular holes so as to be aligned to provide multi nozzles (Hata et al, 2013a). It has been applied to flow rates of 20-30 L min -1 for each nozzle, corresponding to a total of ca.…”