Connecting a straight duct to the side of a trunk duct is similar to connecting a branch take off; a dynamic loss is experienced when the air must turn 90°. Devices to reduce this dynamic loss include splitter dampers, extractors, scoops, cones, elbows, and 45° and radiused tap-ins. Listed in order of improving performance; a basic straight 90° take off falls in the middle of the list with C=1.2. Splitter dampers, extractors, and scoops are counterproductive; a 45° tap in is both economical and efficient (C=0.7). Coefficients will vary with area ratios and velocity ratios.
