The lengths of straight sections of duct add up to 36 feet for the supply side and 13 feet for the return side.
Rectangular duct reducer length calculation.
The fittings add up to 290 feet and 85 feet respectively.
Square feet air volume in cfm can be calculated by multiplying the air velocity by the cross sectional area of the duct in square feet.
Fpm cfm area area cfm fpm.
Now find the total duct losses for each duct and branch that s very easy to do simply multiply the duct length by the pressure drop per meter in our example we found it to be 0 65pa m.
If the design volume flow rate and velocity is 13 000 cfm and 4000 fpm respectively what is the h dimension in a rectangular duct if the w dimension is 14 inches ad q v 13 000 4000 3 25 ft2 multiply by 144 to get in2 468 in2 a d wh h a d w.
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Duct and fittings have interconnecting ends that lock together with brackets.
Do that for all the ducts and branches on the table.
5 cfm fpm x area given any two of these three quantities the third can be readily determined.
Often used in tight spaces such as in walls and ceilings rectangular duct allows you to select larger sizes without increasing duct height.