Dale A. Lundgren

Evaluation of aerosol aspiration efficiency as a function of stokes number, velocity ratio and nozzle angle

Abstract Inertial effects in the aspiration of aerosols from a moving fluid are described in this experimental study. Aspiration coefficients were determined by comparing concentrations collected by two nozzles simultaneously sampling in a 10 cm wind tunnel. The control nozzle was aligned parallel to the axis of the duct and sampled isokinetically. The test nozzle was inserted at angles of 0, 30, 60 and 90° and sampled at a velocity ranging from one half to two times the isokinetic velocity. Particle size, nozzle diameter and free stream velocity were varied to produce a range of Stokes numbers from 0.007 to 3. Data obtained by Belyaev and Levin (1974) were incorporated with experimental data to develop an empirical expression describing the relationship between the aspiration coefficient and the Stokes number as a function of angle of misalignment and velocity ratio. An adjusted Stokes number is described which takes into account the effect of an apparent change in nozzle diameter due to misalignment of the nozzle to the flow stream. Analysis of the probe wash showed that from 15 to 60% of the total particulate matter entering the sampler inlet was lost on the nozzle walls. Implications of this phenomenon are described.

Evaluation of Six Inhalable Aerosol Samplers

Six inhalable aerosol samplers were evaluated experimentally as area samplers using monodisperse solid particles with aerodynamic diameters ranging from 5 to 68 microm. Sampler performance and inside particle loss at two test wind speeds (0.55 and 1.1 m/sec) and three wind orientations (0, 90, and 180 degrees) were investigated. The six inhalable aerosol samplers tested were a RespiCon, an Institute of Occupational Medicine (IOM), a seven-hole, a conical inhalable sampler, a prototype button sampler, and a closed-face 37-mm cassette. The area sampling performance of the RespiCon sampler matched the inhalable convention fairly well. The sampling performances of the other five samplers depended on wind speed, wind direction, and particle size, and they may not be appropriate for area sampling if the wind speeds are greater than 0.5 m/sec.

Comparison and Combination of Aerosol Size Distributions Measured with a Low Pressure Impactor, Differential Mobility Particle Sizer, Electrical Aerosol Analyzer, and Aerodynamic Particle Sizer

Data from a different mobility particle sizer (DMPS) or an electrical aerosol analyzer (EAA) has been combined with data from an aerodynamic particle sizer (APS) and converted to obtain aerosol mass distribution parameters on a near real-time basis. A low pressure impactor (LPI), a direct and independent measure of this mass distribution, provided information for comparison. The number distribution of particles within the electrical measurement range was obtained with the DMPS and EAA. Data from the APS for particles greater than that size were used to complete the number distribution. Two methods of obtaining mass distribution parameters from this number data were attempted. The first was to convert the number data, channel by channel, to mass data and then fit a log-normal function to this new mass distribution. The second method was to fit a log-normal function to the combined number distribution and then use the Hatch-Choate equations to obtain mass parameters. Both the DMPS / APS and the EAA / APS sy...

PM10/PM2.5/PM1 data from a trichotomous sampler

ABSTRACT As part of an effort to determine whether 1 μm or 2.5 μam is the better choice for a new fine particulate matter standard, Professor Virgil A. Marple of the University of Minnesota developed a high volume trichotomous (PM10/PM2.5 /PM1) sampler. Two of these samplers were used to obtain particulate matter (PM) samples at a site located in Phoenix, Arizona, from May 1995 through October 1995. All filter samples were analyzed for mass concentrations and a few for elemental and chemical compositions. Relative fractions were determined for PM10, PM2.5, PM1, PM2.5–10, and PM1–2.5. Calculations were made to evaluate how coarse and fine mode aerosol contributed to the intermediate size range. Results indicated that most of the PM10 in Phoenix was coarse mode PM (windblown dust), which was also a primary contributor to PM25.

Characterization of reaerosolization from impingers in an effort to improve airborne virus sampling.

Aims:  To assess the impact of reaerosolization from liquid impingement methods on airborne virus sampling.

Assessment of iodine‐treated filter media for removal and inactivation of MS2 bacteriophage aerosols

Aims:  To investigate the performance of an iodine‐releasing filter medium for use as a protective device against airborne pathogens.

The Performance of Piezoelectric Crystal Sensors Used to Determine Aerosol Mass Concentrations

Aerosol mass concentration determination using piezoelectric crystal sensors was investigated. Five areas of influence were studied: temperature, humidity, particle collection characteristics, response linearity, and mass sensitivity. A theoretical review is included. Neither air stream temperature nor humidity fluctuations were compensated by the use of a reference crystal. The temperature induced error was satisfactorily reduced by minimizing the inlet temperature change rate. The humidity induced error resulted principally from moisture absorption and desorption by the aerosol deposit. The observed linear response limits ranged from 0.2 to 6 mug/mm2 for various aerosols and instrument designs. No relationship between the linearity limit and the point of complete saturation was apparent. The mass sensitivity was a function of the deposit size and location. Energy trapping theory helped to predict the mass sensitivity distribution. The mass sensing ability decreased for particle sizes beginning at approximately 2 mum diameter, reaching essentially zero at 20 mum. The use of viscous crystal coatings appeared to improve the sensing ability in the 2 to 20 mum size range.

Large Particle Size Distribution in Five U.S. Cities and the Effect on a New Ambient Participate Matter Standard (PM10)

A mobile aerosol-sampling system was used to determine the large particle ambient aerosol size distribution (up to approximately 100 μm particle diameter) in five cities across the United States: Birmingham, Alabama; Research Triangle Park, North Carolina; Philadelphia, Pennsylvania; Phoenix, Arizona; and Riverside, California. A mobile wide range aerosol classifier (WRAC) developed at the University of Florida was used. The study shows that any measurement of ambient particulate matter with a size-fractionating inlet sampler will be influenced by the ambient particle size distribution. Mass distribution measurements determined by the WRAC were compared with mass measurements obtained simultaneously using TSP Hi-Vol and 15 μm cut-size inhalable particulate network samplers. Aerosol size-classification results showed the presence of a large particle mass mode at all sites sampled. The position and magnitude of the large particle mode varied and was not a simple function of concentration. The percentage of ...

Design and Calibration of an In-Stack Low-Pressure Impactor

A high-flow-rate, 10-stage, low-pressure impactor has been constructed for the in-stack measurement of industrial aerosols. The particle collection characteristics of the stages were determined using solid ammonium fluorescein calibration aerosols in conjunction with greased impaction substrates. Cutpoints of the stages were 10, 5.5, 2.9, 1.7, 0.95, 0.50, 0.32, 0.20, 0.11, and 0.047 (μm aerodynamic diameter. Measurement of the nonideal fluid behavior through the impaction nozzles under compressible flow conditions led to the development of empirical discharge coefficients for sharp entry nozzles. Use of these coefficients allows prediction of stage pressure drops as a function of the nozzle dimensions and the fluid properties at the nozzle inlet. Variations in the low-pressure impactor performance have been predicted as a function of temperature and pressure.

Sampling of tangential flow streams.

The causes and characteristics of tangential flow in industrial stacks are described. Errors induced by tangential flow in the determination of volumetric flow rate and particulate concentration are analyzed. Experiments were conducted at the outlet of a cyclone collector in order to investigate the effect of tangential flow on the determination of emission rates. Straightening vanes were found to be useful in the reduction of error in flow rate measurements.