Theoretical and experimental work has been conducted to develop a calibration reference device that could be used in test facilities that conform to ANSI/ASHRAE Standard 52.2 2007. After exploring alternative concepts, including electrostatic precipitators, cyclones, and wire mesh screens, a three-stage parallel flow inertial impactor using round orifices as flow nozzles was selected. Small-scale versions were fabricated and tested for flow rate versus pressure drop and particle capture efficiency versus size. The full-scale prototype was fabricated from aluminum and stainless steel and tested in a wind tunnel configured according to ANSI/ASHRAE Standard 52.2 2007. Oleic acid and potassium chloride aerosols were introduced, and the upstream and downstream particle concentrations were measured with optical particle counters with the channels as required in the standard. Results show a pressure drop of 950 Pa (3.8 in. water) at 0.944m 3/s (2000 cfm) rather than the 750 Pa (3.0 in. water) used in the design. Particle collection efficiency for liquid oleic acid particles nearly agrees with the design theory and provides a minimum efficiency reporting value value of 9. However, solid KCl particles larger than about 3 microns are not captured well, perhaps caused by particle bounce from the porous, oil-impregnated impaction plates. Additional theoretical work is required on pressure drop and solid particle capture for impactors of this design before theoretical predictions agree well with the measured results.
Bibliographical noteFunding Information:
The authors wish to thank ASHRAE for financial support under 1466-RP and members of ASHRAE TC 2.4, Particulate Air Contaminants and Particulate Contaminant Removal Equipment, and members of the project monitoring sub-committee for their support, advice, and guidance throughout this investigation. This project would not have been possible without significant assistance provided by the following companies (in alphabetical order): Cap-tiveAire, Incorporated; Compotech, Incorporated; Donaldson Corporation; Particle Instruments, LLC; Topas GmbH; and TSI, Incorporated.