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Fans – Lecture 2

Fans – Lecture 2. Fan testing:. Dr. C. L. Jones Biosystems and Ag. Engineering . Axial flow fans. propeller fan. tube-axial fan. vane-axial fan. Dr. C. L. Jones Biosystems and Ag. Engineering . Radial flow fans. centrifugal. Sukup literature. Dr. C. L. Jones

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Fans – Lecture 2

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  1. Fans – Lecture 2 • Fan testing: Dr. C. L. Jones Biosystems and Ag. Engineering

  2. Axial flow fans propeller fan tube-axial fan vane-axial fan Dr. C. L. Jones Biosystems and Ag. Engineering

  3. Radial flow fans centrifugal Sukup literature Dr. C. L. Jones Biosystems and Ag. Engineering

  4. cross-flow (tangential) fans Dr. C. L. Jones Biosystems and Ag. Engineering

  5. mixed-flow tubular cent. fans Dr. C. L. Jones Biosystems and Ag. Engineering

  6. Fan Curves • AMCA Handout Dr. C. L. Jones Biosystems and Ag. Engineering

  7. Total pressure, total efficiency, static efficiency • Total Pressure: eqn. 5.1, pg 127 • Find v: eqn. 5.2 • Conversions: • 1 “H2O = 249 Pa • 1 ft/min = .00508 m/sec • 1 lb/in^3 = 27679.9 kg/m^3 • 1 ft^3/min = .000471947 m^3/sec • 1 HP = 745.7 Watts • Total efficiency eqn. 5.3 • Static efficiency eqn. 5.4 • Assume 1750 rpm • Outlet of 10” x 12” • Q = 12030 cfm • Static pressure = 2” • 50 hp • Density = 3.9E-5 lb/in^3 Dr. C. L. Jones Biosystems and Ag. Engineering

  8. Chpt. 10, Aerodynamic and Hydrodynamic Properties • 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) • Reference Figure 10.1 • FD depends on the drag coefficient CD which is quantified using the Reynolds number. Dr. C. L. Jones Biosystems and Ag. Engineering

  9. Chpt. 10, Aerodynamic and Hydrodynamic Properties • NRe = Vdpρf/η • Where: • V = fluid velocity • Dp = particle dimension • ρf= fluid density • η = absolute viscosity • NRe<1.0, Stokes flow, FD=3πdpμV • NRe<1,000 Laminar flow • NRe >20,000 Turbulent flow Dr. C. L. Jones Biosystems and Ag. Engineering

  10. Chpt. 10, Aerodynamic and Hydrodynamic Properties • 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 • 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) Dr. C. L. Jones Biosystems and Ag. Engineering

  11. Chpt. 10, Aerodynamic and Hydrodynamic Properties Read 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 velocity Dr. C. L. Jones Biosystems and Ag. Engineering

  12. Chpt. 10, Aerodynamic and Hydrodynamic Properties Application 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? Dr. C. L. Jones Biosystems and Ag. Engineering

  13. Chpt. 10, Aerodynamic and Hydrodynamic Properties Application 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? Dr. C. L. Jones Biosystems and Ag. Engineering

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