An Aerosol Wind Tunnel for Evaluation of Massive-Flow Air Samplers and Calibration of Snow White Sampler

Abstract

][Massive-flow air samplers are being deployed around the world to collect aerosol samples for analysis of radioactivity as a result of nuclear tests and nuclear accidents. An aerosol wind tunnel capable of an 1100 rrr' min -I flow rate was built at Lovelace Respiratory Research Institute (LRRI) to test the sampling efficiency of these samplers. This aerosol wind tunnel uses a stationary air blender to enha nce mixing, and therefore it achieves the required uniform distribution of wind speed and aerosol concentration in the test section. The test section of the wind tunnel has a cross section that is 4.3 m x 3.7 m. The aero sol wind tunnel was tested for performance in terms of distribution of wind speed, turbulent inten sity, SF6 tracer gas concentration, and aero sol concentration. Test criteria consistent with U.S. Environmental Protection Agency (EPA) and Amer ican National Standards Institute (ANSI) standards were ad opted as the guideline s for the aerosol wind tunnel. Additional cr iter ia for aero sol wind tunnel were also recommended. Initial test of the aero sol wind tunnel showed that the wind tunnel could be operated in a wind speed range of 2 to 24 km h-I. Within this ran ge, th e distribution of wind speed SF 6 trace gas concentration and aero sol concentration in two-thirds of the central area of the test section showed coefficient of variances (Ca Vs) of less than 10% for the ran ge of wind speeds. Thi s met the stringent guidelines for aerosol wind tunnel performance set by EPA and ANSI sta nda rds.The LRRI wind tunnel was used to evaluate the collection efficiency of the sampling head of massive-volume air samplers, including the Snow White sampler. Th e sa mpler was tested in this aero sol wind tunnel for particles between 2 and 20 JLm.The sampling flow rat es were 500 and 700 nr' h-I for th e tested wind speeds of2.2 and 6.6 m S-I, respectivel y. The results showed that sampling efficiency was influenced by both sampling flow rate and wind speed. The sampling efficiency decreased with an increase in particle size of between 2 and 20 JLm. Th e sa mpling efficiency also decrea sed as the wind speed was increased from 2.2 to 6.6 m S-I.

Evaluation of IOM Personal Sampler at Different Flow Rates

“…Schematic of wind tunnel with measurements in inches. Adapted from Figure 1 of Cheng et al (10) by changing the speed of the blower motor. The wind tunnel was calibrated according to U.S Environmental Protection Agency (EPA) (11) and American National Standards Institute (ANSI) standards.…”

“…(10) The wind tunnel consists of an 11-meter-long circular duct with a diameter of 1.83 m; a stationary air blender (Blender Products, Inc. Denver, Colo.), which creates mixing; a flow straightener; a test chamber; and a blower ( Figure 1). …”

“…The COVs of the aerosol concentration were 7.5, 9.1, and 7.5% for wind speeds of 0.56, 2.2, and 6.6 m/s, respectively. The calibration details were described previously in Cheng et al (10) …”

A wind tunnel test of newly developed personal bioaerosol samplers

“…Figure 3 shows the schematic diagram of the Lovelace Respiratory Research Institute (LRRI) large wind tunnel facility employed in this research. This wind tunnel facility has been used in many sampler performance studies for different stationary and personal aerosol samplers (Cheng et al, 2004;Irshad et al, 2006;Zhou and Cheng, 2010), and the results acquired have shown that this wind tunnel can provide reliable experimental data for general aerosol sampler evaluation studies. The LRRI large wind tunnel consists of an 11-m circular duct (1.8 m in diameter), an array of industrial gas mixing blenders (Blender Products, Inc. Denver, CO), a honeycomb flow straightener, a 4.3 m (L) Â 3.7 m (W) Â 3.6 m (H) test chamber, a outflow HEPA filter bank, and a 50-hp motor (Marathon Electric, Wausau, WI).…”

“…The collection efficiency and capture efficiency acquired from the tests were also used as indices for evaluating the design features such as the recirculated liquid in both samplers. The evaluation tests were conducted in a large wind tunnel facility (Cheng et al, 2004), and the personal bioaerosol samplers were mounted on an adult manikin to mimic the sampling scenario of a moving person wearing a personal sampler. The aspiration efficiency acquired was compared with the ACGIH inhalable convention (ACGIH 1985), and the effects of the sampling orientation, wind speed, and aerosol size on the aspiration efficiency were investigated as well.…”