Homework SourseSize the supply and return ducts if the supply flow is 1000
Size the supply and return ducts if the supply flow is 1000 CFM and the return is 700 CFM with a pressure drop on the lower recommended limit (to be green).
Use: http://efficientcomfort.net/asp/ResDuct_Web/ResDuct_Web.asp%5C
Why is the return flow rate typically smaller than the supply?
Solution
This Ductulator uses the Colebrook equation to calculate the smallest duct size acceptable for the selected friction rate and duct type that stays within the selected ACCA Manual D recommended velocities. Unless within 2%, the diameter is rounded up to the nearest inch. Rectangular duct is rounded up to the nearest 1/4 inch. Calculations are for 60°F dry air at sea level, from 5 to 3000 cfm (approximately standard air which is 0.075lbda/ft³). If \"ASHRAE 2013\" is selected, Flexible roughness is 0.003 ft when straight and fully stretched tight at 0% compression (adjusted at other compressions), otherwise the original method of constant 0.01 ft roughness is used.
