Table 2: Selected experimental studies with turbulent flow for particle deposition through bends (2007–2018).

InvestigatorsWilson et al. [21]Ghaffarpasand et al. [24]Sun et al. [22, 23]Lin et al. [10]

Duct bends
Bend typeSmall tubeSmall tubeIndoor rectangular ventilation ductSmall tube
Deposition surface materialStandard stainless steel (grade 304)Stainless steel, hydraulically smoothGalvanized steel and acrylic glassPlexiglass
OrientationDownwards vertical to horizontalNRdHorizontal to horizontalNRd
Construction techniqueMade by a standard tube benderNRdMade by university industrial centerNRd
Hydraulic diameter, (cm)1.020.48101.2
Curvature ratio, (–)7.413.25–543.4NRd
Bend angle, (deg)909090NRd

Airflow
Reynolds number, (×103)10.25, 20.5, and 30.754.5–10.5 De = 1426–2885e17.9, 35.6De = 370–950e
Bulk velocity, (m·s−1)15.4, 30.8, and 46.2NRd2.58, 5.14NRd

Particles
Aerosol type and material (density) (g/cm3)Vitamin E, that is, alpha-tocopheryl acetate (0.91)Tungsten oxide (10.8) and ammonium nitrate (1.725)Arizona standard test particle, basically SiO2, and Al2O3 (2.65)Polydisperse particles with vegetable oil
Diameter, (μm)2.2–110.001–0.02 (monodisperse)0.7–100 (polydisperse)0.008–0.55
Stokes number, (–)0.12–1.080.001–0.035.2 × 10−4–0.55NRd
Reynolds numberb2, (–)NRdNRdNRdNRd
Dimensionless relaxation time, (-)NRdSc = 15–820f0.34–27.6Sc = 186–268,819f

CommentsAssumption of no particle reboundingNanoparticle, neglected coagulationWith particle-wall collisionNanoparticle mechanism considered

eDean number, ; fSchmidt number, , where is the dynamic viscosity.