Rectangular Duct Reducer Length Calculation
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.
Rectangular duct reducer length calculation. Calculate duct size for a given velocity v a d a d example 2. Often used in tight spaces such as in walls and ceilings rectangular duct allows you to select larger sizes without increasing duct height. 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. 5 cfm fpm x area given any two of these three quantities the third can be readily determined.
Duct and fittings have interconnecting ends that lock together with brackets. The fittings add up to 290 feet and 85 feet respectively. Do that for all the ducts and branches on the table. Fpm cfm area area cfm fpm.
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. Duct size or cross sectional area.