Determination of performance-parameter design and impact factors of sampling efficiency for bioaerosol cyclones

Figures & data

Table 1. Categories of bioaerosol samplers.

Samplers	Collection mechanism	Pros	Cons	Air flow rate	Particle size range (aerodynamic diameter)	References
Nutrient plates	Passive inertial	Easy-to-use low-cost, no need for post-sampling preparation	Long culturing time (48 h), no sampling quantitative measurements for microorganisms and air volume	Natural	Any	[1] [8] [13]
Surface sampler	Passive inertial	Easy-to-use, low-cost, no need for post-sampling preparation	Long natural culturing time (48 h), no sampling quantitative measurements for microorganisms and air volume	Natural	Any	[1] [8] [13]
Six stage viable cascade impactor	Active inertial	Particle size separation	Better for lower-concentration bioaerosols, damages microorganisms with violent impact	28.3 L/min	0.65–7 μm	[1] [14]
Impinger	Active inertial	Better pathogen viability, higher collecting efficiency for cut-off size of 1–3 μm	Low flow rate, liquid evaporation	12.5 L/min	0.3 μm	[14] [15]
Wetted-wall cyclone	Active inertial	High flow rate, better pathogen viability, good collection efficiency	Loses smaller and lighter particles, liquid evaporation,	60–400 L/min	0.5–1 µm	[15] [16]
Batch-type wetted wall cyclone	Active inertial	High flow rate, better pathogen viability, no liquid evaporation, good collection efficiency	Low collecting efficiency for cut-off size ≤ 1 µm, and ≥ 10 µm, losses of large particles in the inlet nozzle	265–307 L/min	1–10 µm	[17] [18] [19]
Virtual cyclone	Active inertial	Better pathogen viability, better collection efficiency for small cut-off size particles, good collection efficiency	Unclear relationship between inlet/outlet width and the collection efficiency, unclear separation mechanism	10–50 L/min	0.8–3.2 μm	[20] [21] [22]
Filters	Inertial force, diffusion, and electrostatic attraction	Simple, low cost, and effective	Small filter size and limited flow rate, better for lower-concentration bioaerosols	4 L/min	0.2–3 μm	[5] [23] [24]
Electrostatic precipitation	Others	More concentrated culturable samples for bacteria	Nonviable, lower concentrations of fungal spores	1–10 L/min	0.2–3 μm	[25] [26] [27]

Figure 1. Cyclone with swirling spiral pattern (Reused from Peng et al. [31] with permission).

Figure 2. WWC-1250 device with four modifications by McFarland et al. [32] [Reused with permission]. Red circled numbers: $1$ the aerosol inlet of the upgraded device forms a converging flow path into the cyclone, $2$ the liquid is atomized before entering the inlet slot of this device, $3$ the length of the cylindrically shaped cyclone body is shorter, and $4$ the skimmer was changed to a straight shape rather than a divergent opening.

Figure 3. Virtual cyclone. Left: airflow in the virtual sampler (Reused from Haig et al. [28] with permission). Right: schematic of a virtual cyclone (Reused from Song et al. [20] with permission).

Figure 4. Recent commercial bioaerosol cyclones: Coriolis®µ (a), Research International SASS2300 (b), FLIR Systems BioCapture650 (c), Dekati S110 (d), Burkard C90M (e) and Fuji Biotechnology BIO-Capturer-6 (f).

Figure 5. Venn diagram of the three cyclone performance parameters associated with the inlet efficiency, transport efficiency, and deposition efficiency. (1) Yellow: the common factors associated with all parameters. These are the sampled air-flow rate, particle concentration in the air stream, and particle size. (2) Blue: common factors between the inlet and deposition efficiencies. These are the particle concentrations in the air at the inlet. (3) Pink: common factors between the sampling and deposition efficiencies. These are particle concentrations in the liquid medium. (4) Green: common factors between the inlet and transport efficiencies. These are sampled with the air flow rate [8].

Figure 6. Modifications in aerosol-to-hydrosol cyclone based on CFD simulations (Reused from Hu & McFarland [16] with permission): $1$ narrowing the rectangular entrance slot, $2$ narrowing the shape of air-flow inlet, $3$ adding water injection at the top of cyclone inlet, $4$ changing to a rectangular cyclone body and $5$ re-designing the shape of the cyclone skimmer in the rectangular region.

Figure 7. Integrated scheme for development of an ideal design of a cyclone.

Table 2. Listing of various geometric design units for the cyclone sampling system.

	Design parameters of sampling system components
Main parts	Sampling inlet	Sampling transport	Sampling deposition
Detailed units	Air flow rate Inlet shape: orientation, width, angles Particle size Pressure drop	Tube length Bend angle Transit time Flow type (laminar/turbulent) Materials of tube and probe Contraction on tube	Liquid flow rate Film thickness Shape of collecting container Liquid medium

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