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 = m/sec
1 lb/in^3 = kg/m^3
1 ft^3/min = m^3/sec
1 HP = Watts
Total efficiency eqn. 5.3
Static efficiency eqn. 5.4
Assume 1750 rpm
Outlet of 10” x 12”
Q = 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)( (Rep)0.687)
Dr. C. L. Jones
Biosystems and Ag. Engineering

11. Chpt. 10, Aerodynamic and Hydrodynamic Properties
Read Example Problem 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