Aspiration Efficiency of a Thin-Walled Probe at Right Angles to the Wind

Details

• Personal Author:
  Brixey LA ; Evans DE ; Vincent JH
• Description:
  A new experimental system was recently developed for the rapid acquisition of data for aerosol sampler aspiration efficiency, and was applied in this latest work to the experimental study of thin-walled probes oriented at 90 degrees to the freestream. Previous experimental studies from the 1980s, backed up by a physical model, suggested that aspiration efficiency for this orientation (A90) may be uniquely described as a function of StR 1/2 (where St is the Stokes number for particle motion in the region of the sampler entry, and R is the ratio of the freestream air velocity to the average air velocity across the plane of the sampler inlet). But in this new work the experimental system was sufficiently selective as to allow detection of an additional dependency on R not revealed by the previous work. It is proposed that this additional dependency is associated with effects associated with the non-uniformity of the airflow distribution across the plane of the test sampler at such extreme orientations, derived from the inertia of the air motion as it approaches the sampler. One result of such non-uniformity is to reduce the effective cross-sectional area of the inlet as R increases. The experimental results suggest that A90 is now better described as a unique function of StR 1/4 (instead of StR 1/2 ). Such new insights into the basic physical behavior of a simple aerosol sampling scenario may be useful in helping to explain some aspects of the performances of more complicated aerosol samplers like those used in practical occupational and environmental air sampling situations. [Description provided by NIOSH]
• Subjects:
  Aerosols Occupational Exposure Occupational Health Safety
• Keywords:
  Aerosol-particles Aerosol-sampling Aspiration Efficiency Author Keywords: Aerosol Samplers Models Occupational-exposure Right Angles Samplers Sampling Sampling-methods Thin-walled Probes

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• ISSN:
  0021-8502
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Michigan ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  36
• Issue:
  9
• NIOSHTIC Number:
  nn:20029585
• Citation:
  J Aerosol Sci 2005 Sep; 36(9):1144-1156
• Email:
  jhv@umich.edu
• Federal Fiscal Year:
  2005
• NORA Priority Area:
  Research Tools and Approaches: Exposure Assessment Methods
• Performing Organization:
  University of Michigan, Ann Arbor, Michigan
• Peer Reviewed:
  True
• Start Date:
  19940901
• Source Full Name:
  Journal of Aerosol Science
• End Date:
  20090831
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:9bf52fd89f9ca3bcf9f8827bf8a308dbabde1517eeae1fc56836b4bd707db8117b6c019edbb3fd183d51e716ee9a0ffb4b27a5fd490cb15bc763e32af5e6d4d0
• Download URL:
  https://stacks.cdc.gov/view/cdc/190534/cdc_190534_DS1.pdf
• File Type:
  [PDF - 373.16 KB ]