Aerosol penetration through a model transport system: comparison of theory and experiment

Abstract

Numerical predictions were made of aerosol penetration through a model transport system. A physical model of the system was constructed and tested in an aerosol wind tunnel to obtain comparative data. The system was 26.6 mm in diameter and consisted of an inlet and three straight sections (oriented horizontally, vertically, and at 45°). Particle sizes covered a range in which losses were primarily caused by inertial and gravitational effects [3-25Atm aerodynamic equivalent diameter (AED)]. Tests were conducted at two flow rates (70 and 130 L/min) and two inlet orientations (parallel and perpendicular to the free stream). Wind speed was 3 m/s for all test cases. The cut points for aerosol penetration through the experimental model vis-a-vis the numerical results are as follows: At a flow rate of 70 L/min with the inlet at 0°, the experimentally observed cut point was 16.2 µ AED while the numerically predicted value was 18.2 µ AED. At 130 L/min and 0°, the experimental cut point was 12.8 µ AED as compared with a numerically value of 13.7 µ AED. At 70 L/min and a 90°inlet orientation, the experimental and numerical cutpoints were 11.2 and 11.6 µ AED, respectively; and, at 130 L/min and 90°, the experimental cut point was 12.0 µ AED while the numerically calculated value was 11.1 µ AED. Slopes of the experimental penetration curves are somewhat steeper than the numerically predicted counterparts.

Mathematical Modeling for the Design and Scale-Up of a Large Industrial Aerosol-Assisted Chemical Vapor Deposition Process under Uncertainty

“…The total penetration, is obtained by the product of all the individual penetration fractions, P T = ∏ i P S, i ∏ j P B, j , where P S, i is the penetration for each straight pipe section i and P B, j is the penetration for each bend j . Given a straight pipe section i of length L i [m], the penetration P S, i is modeled as ,, where d [m] is the pipe diameter and Q [m 3 ·s –1 ] is the fluid flow rate. V e, i [m·s –1 ] is defined as the effective velocity of aerosol loss, as a function of the three main loss mechanisms: Brownian diffusion, turbulent diffusion, and gravitational settling.…”

Single-point representative sampling with shrouded probes

“…Wall losses in a probe occur as a natural consequence of the sampling process. Fan et al (1992b) showed that Air Sampling with Shrouded Probes at the WIPP Site Saffman force, which arises when aerosol particles are McFarland et al (1989)developed the shrouded probe decelerated (or accelerated) in a shear flow, causes system that is used at the WIPP site to monitor effluent air aerosol particles to be lost to the walls in the entrance discharged from underground disposal areas. The WIPP region of a probe.…”

“…Another factor that should be noted concerning the subisokinetic sampling of the WIND TUNNEL TESTS OF SHROUDED PROBES shroud is that concentration bias, as reflected by the WIPP Probe aspiration ratio, A, depends upon the Stol,'¢s number based upon the shroud diameter. Because the shroud McFarland et al (1989) tested the WIPP shrouded diameter is relatively large, the aspiration ratio will be probe in both aerodynamic and aerosol wind tunnels. nearer to unity as compared with an unshrouded probe With respect to the aerodynamic tests, the shrouded = 51 mm (2 in),free stream velocity = 21.3 m/s, and U/U = 0,25, Note that at the entrance of the shroud, the streamlines near the shroud walls"have greater curvature than those near the center of theflow field (Gong et al 1993).…”

“…Free stream velocity = 15 rrds and sampling flow rate = 170 L/min. (McFarland et al 1989). Reprinted with permission from McFarland, A.R.…”

Measurement of particle deposition in industrial ducts

“…This method is limited to laboratory investigations of particles smaller than 30 m, is di cult to adapt to large ducts, and requires many tests to fully characterize deposition. Other schemes allow ÿeld portability and rapid analysis by extracting particles directly from a duct (Leith, Raynor, Boundy, & Cooper, 1996); however, di culties in aspiration and transport restrict use of these techniques to particles smaller than about 10 m (Fan, Wong, McFarland, & Anand, 1992;Gong, Anand, & McFarland, 1993;McFarland, Wong, Anand, & Ortiz, 1991).…”