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Sampling Probes as Precollectors for Cascade Impactor Measurements on Aerosols in Gas Flows
Author(s) -
Bürkholz Armin
Publication year - 1987
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/ppsc.19870040119
Subject(s) - nozzle , impaction , mechanics , sampling (signal processing) , particle (ecology) , inlet , cascade , aerosol , environmental science , materials science , chemistry , meteorology , optics , physics , geology , thermodynamics , chromatography , surgery , geomorphology , detector , medicine , oceanography
In the measurement of dust particles or droplets with cascade impactors, coarser particles are lost both in the impactor and in the sampling train. In order to reduce these losses and to recover this coarse fraction, the use of a precollector is recommended. As a rule, measurements in industry must generally be made with sampling probes. It is, therefore, reasonable to combine the probe and precollector. We measured the particle losses which occur in probes as a consequence of sedimentation and inertial forces. Wall losses through turbulent deposition seem to play only a minor role. By adjusting the gas inlet to a nozzle‐impaction plate sampling system, the coarse fraction can be collected and assessed quantitatively. Particle losses in the subsequent probe and impactor can, thus, be kept very low. By using nozzles of different apertures and by varying the gas flow rate, isokinetic sampling conditions can be achieved. The collecting properties of the nozzle‐impaction plate system inlet correspond very closely to those predicted by impaction theory. A special adaptation of the nozzle can give a cut point of the precollector close to 10 microns. Cut points at greater particle sizes are not recommended because of uncontrollable particle losses in the probe.