The following are calculations for the CFM and CFM/bu. for the eight bins we had trials on for 2017. We measured the airflow into the fans in km/hr. so the first conversion is to get this into ft/min because we eventually want to get to cubic feet per minute.
kmph –> ft./min 1 kmph = 0.9113 ft/sec = 54.678 ft./min H2O pressure
Bin 18 (3500 bu, Diam 23″) 11.2 km/hr x 54.678 = 612.4 ft/min x Area (pi r^2) 23/12/2 2.88sq ft = 1767 CFM /3500 0.50 CFM/bu 5.5″/7.4″
Bin 19 (3500 bu, Diam 23″) 11.2 km/hr x 54.678 = 612.4 ft/min x Area (pi r^2) 23/12/2 2.88sq ft = 1767 CFM /3500 0.50 CFM/bu 5.5″/7.4″
Bin 9 (2200 bu, Diam 15″) 30 km/hr x 54.678 = 1640 ft/min x Area (pi r^2) 15/12/2 1.22 sq ft = 2013 CFM /2000 1.0 CFM/bu 3.25″/5.0″
Bin 10 (2200 bu, Diam 15″) 30 km/hr x 54.678 = 1640 ft/min x Area (pi r^2) 15/12/2 1.22 sq ft = 2013 CFM /2000 1.0 CFM/bu 3.25″/5.0″
Bin 15 (10000 bu, Diam 15″) 70 km/hr x 54.678 = 3827 ft/min x Area (pi r^2) 15/12/2 1.22 sq ft = 4669 CFM /10000 0.466 CFM/bu 6″ (inside )
Bin 14 (5000 bu, Diam 15″) 85 km/hr x 54.678 = 4647 ft/min x Area (pi r^2) 15/12/2 1.22 sq ft = 5669 CFM /5000 1.13 CFM/bu 5″
Bin 16 (3500 bu, Diam 16″) 18 km/hr x 54.678 = 984 ft/min x Area (pi r^2) 16/12/2 1.39 sq ft = 1373 CFM /3500 0.3925 CFM/bu 5″/6″
Bin 16 (3500 bu, Diam 16″) 18 km/hr x 54.678 = 984 ft/min x Area (pi r^2) 16/12/2 1.39 sq ft = 1373 CFM /3500 0.3925 CFM/bu 4.8″/5.75″
The pressure is in inches of water ; the first number is outside the plenum and the number after the / is the inside of the plenum, so you can see the pressure drop across the perforated holes in the pipe.