Particle Deposition in Ventilation Ducts: Connectors, Bends and Developing Turbulent Flow

Figures & data

FIG. 1 Side-view schematic diagram of the experimental apparatus (not to scale). Straight duct sections are square in crosssection, 15 cm on a side by 152 cm long. The inset shows a close-up side view of an S-connector between two duct sections.

FIG. 2 Dimensionless deposition velocities to S-connectors on the ceiling, wall, and floor at air speeds of (a) 2.2 m/s, (b) 5.3 m/s, and (c) 9.0 m/s.

FIG. 3 S-connector deposition fraction versus connector Stokes number for S-connectors on the ceiling, wall, and floor at the three nominal air speeds.

TABLE 1 Average S-connector deposition fractions in the bare steel duct system ^a

Run #(−)	U ave (m s^−1)	u* (m s^−1)	d p (μm)	StS (−)	η S,c (−)	η S,w (−)	η S,f (−)
1	2.2	0.12	1.0	4.2×10^−3	1.8×10^−3	1.0×10^−4	1.4×10^−3
2	2.2	0.12	2.8	0.026	8.1×10^−3	4.2×10^−4	5.0×10^−3
3	2.1	0.12	5.2	0.091	0.015	9.0×10^−4	0.014
4	2.2	0.13	9.1	0.25	0.021	6.7×10^−3	0.024
5	2.2	0.12	16 0.0	0.66	0.046	0.065	0.078
6	5.3	0.28	1.0	0.015	7.9×10^−4	4.2×10^−4	8.1×10^−4
7	5.2	0.26	1.0	0.014	6.7×10^−4	1.9×10^−4	7.5×10^−4
8	5.2	0.26	3.1	0.11	3.3×10^−3	1.8×10^−3	4.7×10^−3
9	5.4	0.27	5.2	0.31	0.029	0.020	0.029
10	5.3	0.28	9.8	0.97	0.038	0.013	0.028
11	5.3	0.28	160.0	2.3	0.10	0.13	0.15
12	9.0	0.45	1.0	0.030	5.2×10^−4	3.9×10^−4	6.5×10^−4
13	9.0	0.42	3.1	0.21	4.6×10^−3	3.4×10^−3	4.8×10^−3
14	8.8	0.44	5.4	0.68	0.020	0.013	0.028
15	9.2	0.46	8.7	1.5	0.027	0.010	0.022
16	9.1	0.45	150.0	4.2	0.14	0.068	0.086
U ave , mean air speed through duct; u*, friction velocity; d p , particle diameter; StS, S-connector Stokes number (see Equation (14)); η S,c , S-connector deposition fraction at a duct ceiling; η S,w , S-connector deposition fraction at a duct wall; η S,f , S-connector deposition fraction at a duct floor.

FIG. 4 Penetration through (a) bend 5 and (b) bend 6 versus bend Stokes number for all air speeds in both the bare steel and insulated systems.

FIG. 5 Composite dimensionless deposition velocities in (a) bend 5 and (b) bend 6 compared to dimensionless deposition velocities in straight steel ducts at nominal air speeds of 2.2 m/s, 5.3 m/s, and 9.0 m/s.

TABLE 2 Measured bend penetrations for all experiments ^a

Run #(−)	U ave (m s^−1)	u* (m s^−1)	d p (μm)	Stbend (−)	P bend5 (−)	P bend6 (−)
1	2.2	0.12	1.0	—	—	—
2	2.2	0.12	2.8	—	—	—
3	2.1	0.12	5.2	2.9×10^−3	0.999	0.999
4	2.2	0.13	9.1	7.5×10^−3	0.995	0.997
5	2.2	0.12	160.0	0.020	0.977	0.990
6	5.3	0.28	1.0	—	—	—
7	5.2	0.26	1.0	3.2×10^−4	1.00	1.00
8	5.2	0.26	3.1	2.4×10^−3	0.999	1.00
9	5.4	0.27	5.2	7.3×10^−3	0.982	0.998
10	5.3	0.28	9.8	0.021	0.967	0.997
11	5.3	0.28	160.0	0.051	0.952	0.986
12	9.0	0.45	1.0	5.8×10^−4	1.00	1.00
130.0	9.0	0.42	3.1	4.3×10^−3	0.995	1.00
14	8.8	0.44	5.4	0.013	0.923	0.993
15	9.2	0.46	8.7	0.029	0.941	0.992
16	9.1	0.45	150.0	0.081	0.873	0.974
17	2.2	0.16	1.0	1.3×10^−4	1.00	1.00
18	2.2	0.16	3.0	9.4×10^−4	1.00	1.00
19	2.2	0.16	5.3	3.0×10^−3	0.999	0.998
20	2.2	0.16	8.4	6.7×10^−3	0.992	0.996
21	2.2	0.16	130.0	0.014	0.964	0.988
22	5.3	0.37	1.0	3.3×10^−4	0.999	1.00
23	5.2	0.37	2.9	2.1×10^−3	0.999	1.00
24	5.2	0.37	4.9	6.1×10^−3	0.994	0.998
25	5.3	0.38	8.2	0.016	0.967	0.991
26	5.3	0.38	130.0	0.034	0.970	0.983
27	8.9	0.62	1.0	5.4×10^−4	1.00	1.00
28	8.7	0.62	2.8	3.4×10^−3	0.997	0.999
29	8.9	0.62	5.0	0.011	0.971	0.996
30	8.9	0.64	8.4	0.027	0.975	0.985
31	8.9	0.64	130.0	0.055	0.959	0.976
U ave , mean air speed through duct; u*, friction velocity; d p , particle diameter; Stbend, bend Stokes number (see Equation (18)); P bend5 , penetration through bend 5; P bend6 , penetration through bend 6.

TABLE 3 Dimensionless deposition velocities for all panels in test duct 4 for all experiments ^{a b}

			Ceiling, (−)				Wall, (−)				Floor, (−)
Run #	U ave (m/s)	d p (μm)	Panel 1	Panel 2	Panel 3	Panel 4	Panel 1	Panel 2	Panel 3	Panel 4	Panel 1	Panel 2	Panel 3	Panel 4
1	2.2	1.0	—	—	—	—	—	—	—	—	—	—	—	—
2	2.2	2.8	—	—	—	—	—	—	—	—	—	—	—	—
3	2.1	5.2	1.9 × 10^−5	2.4 × 10^−5	2.8 × 10^−5	2.6 × 10^−5	7.7 × 10^−4	5.8 × 10^−4	4.9 × 10^−4	3.4 × 10^−4	0.011	0.010	0.011	0.011
4	2.2	9.1	4.7 × 10^−5	4.0 × 10^−5	2.9 × 10^−5	2.6 × 10^−5	6.3 × 10^−4	1.1 × 10^−3	1.0 × 10^−3	1.0 × 10^−3	0.029	0.029	0.031	0.031
5	2.2	16	1.3 × 10^−4	8.3 × 10^−5	8.7 × 10^−5	4.0 × 10^−5	0.017	0.012	8.9 × 10^−3	5.0 × 10^−3	0.063	0.063	0.067	0.060
6	5.3	1.0	—	—	—	—	—	—	—	—	—	—	—	—
7	5.2	1.0	1.7 × 10^−5	1.2 × 10^−5	1.2 × 10^−5	1.0 × 10^−5	5.5 × 10^−5	4.2 × 10^−5	4.0 × 10^−5	3.7 × 10^−5	2.3 × 10^−4	2.3 × 10^−4	2.2 × 10^−4	2.0 × 10^−4
8	5.2	3.1	2.3 × 10^−5	1.4 × 10^−5	1.1 × 10^−5	1.1 × 10^−5	1.5 × 10^−4	1.1 × 10^−4	1.0 × 10^−4	9.3 × 10^−5	1.6 × 10^−3	1.6 × 10^−3	1.6 × 10^−3	1.6 × 10^−3
9	5.4	5.2	2.3 × 10^−4	8.8 × 10^−5	9.2 × 10^−5	5.7 × 10^−5	2.9 × 10^−3	1.7 × 10^−3	9.4 × 10^−4	5.9 × 10^−4	8.8 × 10^−3	8.5 × 10^−3	8.7 × 10^−3	8.9 × 10^−3
10	5.3	9.8	1.8 × 10^−3	7.4 × 10^−4	2.8 × 10^−4	1.2 × 10^−4	9.0 × 10^−3	5.0 × 10^−3	2.3 × 10^−3	8.8 × 10^−4	0.019	0.021	0.021	0.021
11	5.3	16	0.017	7.4 × 10^−3	3.7 × 10^−3	1.6 × 10^−3	0.092	0.080	0.050	0.022	0.075	0.062	0.081	0.070
12	9.0	1.0	8.0 × 10^−5	4.5 × 10^−5	3.1 × 10^−5	2.4 × 10^−5	9.6 × 10^−5	3.7 × 10^−5	6.3 × 10^−5	5.6 × 10^−5	2.5 × 10^−4	2.3 × 10^−4	2.6 × 10^−4	2.9 × 10^−4
13	9.0	3.1	5.8 × 10^−4	2.0 × 10^−4	1.0 × 10^−4	5.9 × 10^−5	8.1 × 10^−4	4.4 × 10^−4	2.7 × 10^−4	1.9 × 10^−4	1.3 × 10^−3	1.3 × 10^−3	1.3 × 10^−3	1.3 × 10^−3
14	8.8	5.4	0.011	5.5 × 10^−3	2.8 × 10^−3	1.4 × 10^−3	0.012	6.5 × 10^−3	4.0 × 10^−3	2.8 × 10^−3	0.014	0.014	0.015	0.015
15	9.2	8.7	0.026	0.011	6.7 × 10^−3	3.9 × 10^−3	0.016	0.011	9.1 × 10^−3	6.5 × 10^−3	0.028	0.029	0.033	0.035
16	9.1	15	0.020	0.021	0.019	0.015	0.043	0.040	0.038	0.040	0.10	0.10	0.10	0.11
17	2.2	1.0	1.9 × 10^−3	9.9 × 10^−4	8.3 × 10^−4	7.2 × 10^−4	1.3 × 10^−3	8.9 × 10^−4	7.6 × 10^−4	4.7 × 10^−4	5.8 × 10^−4	5.2 × 10^−4	5.0 × 10^−4	5.2 × 10^−4
18	2.2	3.0	6.4 × 10^−3	3.4 × 10^−3	2.3 × 10^−3	2.7 × 10^−3	4.7 × 10^−3	2.7 × 10^−3	2.5 × 10^−3	1.7 × 10^−3	2.3 × 10^−3	2.2 × 10^−3	2.3 × 10^−3	2.1 × 10^−3
19	2.2	5.3	0.018	9.0 × 10^−3	4.7 × 10^−3	3.9 × 10^−3	7.0 × 10^−3	6.4 × 10^−3	6.2 × 10^−3	4.1 × 10^−3	5.9 × 10^−3	5.8 × 10^−3	5.9 × 10^−3	5.9 × 10^−3
20	2.2	8.4	0.026	0.010	5.9 × 10^−3	3.9 × 10^−3	0.023	0.018	0.014	7.3 × 10^−3	0.021	0.018	0.020	0.018
21	2.2	13	0.065	0.038	0.013	7.6 × 10^−3	0.056	0.038	0.022	8.6 × 10^−3	0.062	0.058	0.061	0.055
22	5.3	1.0	4.9 × 10^−3	2.6 × 10^−3	2.1 × 10^−3	2.0 × 10^−3	2.6 × 10^−3	2.4 × 10^−3	2.4 × 10^−3	2.2 × 10^−3	1.7 × 10^−3	1.6 × 10^−3	1.7 × 10^−3	1.9 × 10^−3
23	5.2	2.9	0.028	0.020	0.012	8.1 × 10^−3	0.016	0.013	9.4 × 10^−3	7.6 × 10^−3	6.0 × 10^−3	6.8 × 10^−3	8.2 × 10^−3	8.2 × 10^−3
24	5.2	4.9	0.066	0.038	0.031	0.017	0.048	0.034	0.029	0.022	0.016	0.018	0.022	0.024
25	5.3	8.2	0.12	0.065	0.047	0.029	0.074	0.050	0.036	0.031	0.034	0.040	0.041	0.037
26	5.3	13	0.23	0.11	0.079	0.067	0.11	0.10	0.097	0.083	0.079	0.073	0.075	0.079
27	8.9	1.0	5.2 × 10^−3	4.1 × 10^−3	3.6 × 10^−3	2.5 × 10^−3	4.0 × 10^−3	3.8 × 10^−3	4.4 × 10^−3	3.5 × 10^−3	2.4 × 10^−3	2.1 × 10^−3	2.8 × 10^−3	2.6 × 10^−3
28	8.7	2.8	0.053	0.028	0.025	0.021	0.029	0.025	0.023	0.019	0.013	0.018	0.018	0.020
29	8.9	5.0	0.14	0.071	0.053	0.045	0.072	0.065	0.047	0.047	0.027	0.033	0.042	0.042
30	8.9	8.4	0.16	0.093	0.073	0.063	0.11	0.090	0.079	0.063	0.061	0.057	0.061	0.053
31	8.9	13	0.092	0.076	0.046	0.040	0.084	0.056	0.053	0.045	0.044	0.048	0.046	0.042

FIG. 6 Enhancement factors at the ceiling, wall, and floor at panels in duct 4 in the bare steel system at three air speeds. Panels measure approximately 10 cm × 20 cm and are centered 30, 61, 91, and 122 cm downstream from the leading edge of a duct. See Sippola and Nazaroff (2004) for additional details.

FIG. 7 Enhancement factors at the ceiling, wall, and floor at panels in duct 4 in the insulated system at three air speeds. Panels measure approximately 10 cm × 20 cm and are centered 30, 61, 91, and 122 cm downstream from the leading edge of a duct. See Sippola and Nazaroff (2004) for additional details.

Sippola , M. R. and Nazaroff , W. W. 2004 . Experiments Measuring Particle Deposition from Fully Developed Turbulent Flow in Ventilation Ducts . Aerosol. Sci. Technol. , 38 : 914 – 925 . http://dx.doi.org/10.1080%2F027868290507213

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