Aerosol particle losses in isokinetic sampling probe inlets

Aerosol Deposition in Sampling Probes

“…Since PI and Stk depend on the lift and inertial forces, as opposed to the external gravitational force, the correlation emphasizes the intrinsic nature of particle deposition in the sampling. The exclusion of the lift force may produce a significant discrepancy between modeling and experiment as shown by Fan et al (1992a). The intrinsic deposition of aerosols can be observed in vertical sampling, in which the external mechanism of gravitational settling is absent.…”

“…The necessity of the inclusion of particle lift effect into general considerations of aerosol particle behavior in internal flows has been confirmed by Fichman et al (1988), McLaughlin (1989, and Fan et al (1992a, b). In contrast to the drag force that acts on a particle in the direction of relative velocity between particle and gas flow, the lift force acts on a particle in a direction transverse to the flow streamline, which, in turn, can cause a particle to be deflected towards a wall.…”

“…Also, it may be surmised that in many high-speed aerosol sampling situations, the gravitational settling will be negligible no matter what the probe orientation and the intrinsic particle deposition will dominate the wall losses. Fan et al (1992a) reviewed the forces that act on aerosol particles in the inlet region of a probe and noted that a force predicted by Saffman (1965), which is a particle lift force that acts in a direction perpendicular to the flow stream, can have a significant effect on particle deposition. This force is of particular consequence in the inlet region of a probe where there is high flow shear combined with particle deceleration in the shear layer.…”

Performance Testing of a Multimetals Continuous Emissions Monitor

“…A distinct disadvantage of the shepherd's crook nozzle is its susceptibility to accumulation of sample aerosols as a result of turbulent deposition. 13 In a former MMCEM adaptation that failed to achieve a level of analytical performance comparable to that of the present system, the Method 5 probe, with a 6.35-mm nozzle orifice, was used in conjunction with a 15.2-m-long, 10-mm i.d. heated Teflon transport line.…”

Functional requirements document for measuring emissions of airborne radioactive materials

“…Previously,the ANSI N13.1 (1969) standardrecommendedprobe designs for aerosol sampling shown in Figure 4.1. However, use of such probes that have constant internalcross sections and a 90 elbow of the same cross section is no longer consideredgood practicebecause of substantialaerosol particle losses in both the straight entrance region and the elbow and because of errors associatedwith off-designoperationalconditions (Fan et al, 1992, McFarland andRodgers, 1993). Also, ANSI N13.1(1969)recommendedthe deploymentof multiple inlets in circular ducts larger than 6-inchesdiameter or in rectangularducts with cross sectionalareas greater than 0.5 ft2.…”