Slide 1Figure 10.1Slide 3Slide 4Slide 5Slide 6Slide 7Slide 83/31/08 BAE 2023 Physical Properties 1Dr. C. L. JonesBiosystems and Ag. Engineering•Air and water are used to remove foreign material from products•How much air required depends on the drag force FD ( sum of skin friction and pressure drag)•FD affected by density, abs. viscosity, area and velocity (equation 10.1)•Reference Figure 10.1Aero/Hydrodynamic Properties3/31/08 BAE 2023 Physical Properties 2Figure 10.13/31/08 BAE 2023 Physical Properties 3Dr. C. L. JonesBiosystems and Ag. Engineering•FD depends on the drag coefficient CD which is quantified using the Reynolds number.•NRe = Vdpρf/η Where: »V = fluid velocity»dp = particle dimension»ρf= fluid density»η = absolute viscosity•NRe<1.0, Stokes flow, FD=3πdpμV (sphere)•NRe<1,000 Laminar flow• NRe >20,000 Turbulent flowAero/Hydrodynamic Properties3/31/08 BAE 2023 Physical Properties 4Dr. C. L. JonesBiosystems and Ag. Engineering•Terminal velocity: occurs when drag force balances gravitational force•See Table 10.1•For a sphere–Fdrag=CD(πd2/4)(ρfv2/2)•CD depends on the Reynold number of the particle: Rep= ρfvd/μ (restated from eqt. 10.1 in different terms)•If Rep<0.2, CD=24/Rep•If Rep>200,000, CD=0.44•If Repis between 500 and 200,000, CD=(24/Rep)(1.0 + 0.15(Rep)0.687)Aero/Hydrodynamic Properties3/31/08 BAE 2023 Physical Properties 5Dr. C. L. JonesBiosystems and Ag. EngineeringLecture 17 – Aero/Hydrodynamic Properties (Ch. 10)3/31/08 BAE 2023 Physical Properties 6Dr. C. L. JonesBiosystems and Ag. EngineeringRead Example Problem 10.1. You will need to be familiar with it. This examples shows how to find a Reynolds number for a particle, the drag coefficient and the terminal velocityAero/Hydrodynamic Properties3/31/08 BAE 2023 Physical Properties 7Dr. C. L. JonesBiosystems and Ag. EngineeringApplication example: Can corn stalks be separated from corn cobs pneumatically? What minimum air velocity can be used?How well will it be separated?How could we improve the separation?Aero/Hydrodynamic Properties3/31/08 BAE 2023 Physical Properties 8Dr. C. L. JonesBiosystems and Ag. EngineeringApplication example: A seed company would like to move soybeans through a pipe (5.25” inside diameter) pneumatically. What capacity should the air source (the fan) be rated for?Aero/Hydrodynamic
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