Use of a convective emission chamber to study particle resuspension
Shaw, Bryan Webb
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Permalink
https://hdl.handle.net/2142/21010
Description
Title
Use of a convective emission chamber to study particle resuspension
Author(s)
Shaw, Bryan Webb
Issue Date
1994
Doctoral Committee Chair(s)
Christianson, Leslie L.
Department of Study
Agricultural and Biological Engineering
Discipline
Agricultural Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Agricultural
Language
eng
Abstract
A convective emission chamber was developed to deliver a uniform air flow across the source surface and allow control at different levels of air velocity (0-0.5 m/s), turbulent intensity (5-40%), temperature (15-30$\sp\circ\rm C),$ and relative humidity (30-80%). Particle resuspension rates were measured with a laser based optical particle counter for various combinations of environmental conditions with and without the presence of mechanical disturbance of the source. The resuspension rates for the various combinations of environmental conditions were compared to rates for a predefined base case of environmental conditions typical of indoor environments.
Analysis indicated that the velocities and turbulence intensities typically found in commercial, residential, and agricultural facilities are below the threshold required to resuspend the dust tested. Therefore, it was concluded that the primary mechanism for dust resuspension involves the interaction of velocity and mechanical disturbances such as people and animals walking on the source.
Analysis of data from the velocity and mechanical disturbance interaction tests indicated that the resuspension rate was not directly proportional to velocity as expected. In fact, the resuspension rate initially decreased with increasing velocity then began increasing again as the velocity increased above 0.2 m/s. Increases in relative humidity were found to reduce the resuspension rate for relative humidities from 30 to 60%. A low temperature setting $(16\sp\circ\rm C)$ was found to have a higher resuspension rate than the higher temperature settings of 24 and $32\sp\circ\rm C.$ The high turbulence intensity setting had a resuspension rate which was statistically larger than the resuspension rate for the low turbulence intensity setting. Decreased dust source concentration increased the resuspension rate for particles 4 $\mu\rm m$ and below.
High turbulence intensity and low temperature were the two environmental factors that yielded the largest increase in resuspension rate when compared to the base case environmental conditions. The velocity setting of 0.2 m/s produced the largest reduction in resuspension rate when compared to the base case conditions. Although a clear understanding of the mechanisms involved in the effects of velocity and temperature is not yet available, these two factors and turbulence intensity hold the most potential for providing insights into more effective particle control methods.
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