Effect of an Orifice on Collection Efficiency and Wall Loss of a Slit Virtual Impactor

Figures & data

TABLE 1 Dimensions and operation conditions of the slit virtual impactors tested in this study, with W_c /W_a = 1.4, S/W_a = 1.5, T/W_a = 1.1, d/W_a = 1, D/W_a = 6, l/W_a = 10, L/W_a = 4∼36, and r = 0.1

Wa (mm)	0.8	1	1.2	1.8	2	2.2	2.8	3	3.2	4	5
Q (L/min)	5.31	10.4	17.9	10.1	13.9	18.5	11.9	14.6	17.8	34.7	67.8
Re	730	1140	1640	620	760	920	470	540	610	950	1490

FIG. 1 Cross-sectional view of the slit virtual impactor with an orifice.

FIG. 2 Schematic of the experimental setup.

FIG. 3 Particle trajectories in the slit virtual impactor: (a) without orifice; (b) with orifice.

FIG. 4 Comparison of numerical and experimental data for collection efficiency and wall loss of the slit virtual impactor: (a) without orifice; with orifice where (b) L = 4 mm, (c) L = 12 mm, (d) L = 20 mm, (e) L = 28 mm, and (f) L = 36 mm.

FIG. 5 Numerically obtained collection efficiencies and wall losses of the slit virtual impactors with various nozzle sizes as a function of the square root of the Stokes number: (a) without orifice; (b) with orifice, L = 20W_a .

FIG. 6 Numerically obtained collection efficiency and wall loss of the slit virtual impactor without or with orifice: (a) PM₁ nozzle; (b) PM_2.5 nozzle; (c) PM₁₀ nozzle.