We bought a digital anemometer to check the CFM of various fans we have on hand. My husband designed and 3D Printed this duct that securely mounts fans on to the anemometer for accurate readings, which seems to work great.
The unit we have takes an input of FT² and automatically converts that to CFM, but we don't know how to determine the surface area in FT² of this duct design, given the cone shape, fins and solid center area.
We tried using
Pi x R ^ 2 with Radius from the small fan side, and again with Radius from the large anemometer side, but this isn't quite correct. We're using a high end 6 CFM fan as a baseline, and readings are roughly 2.5 CFM off depending on which end we measure the radius of.
Any advice on how to properly find the surface area of this would be great. We tried loading the STL file in CAD software like Fusion 360, but it measure the design, not the channels for airflow.