Sativa1970
Well-Known Member
Volume is like lanes in a highway. Velocity would be the speed of the cars. Cutting the number of lanes in half would require doubling the speed to just break even on trafic flow. 4 to 3 inch reduction would be roughly 12 to 7 area reduction. Some velocity is created by the reduction but closer to 25% when you need 100% to break even. That's why you may need a bigger fans velocity for smaller duct to move the same CFMs.Isnt more Velocity better or am i tripping