The duct is open at the end, so there is not pressure.
Let me ask this: If you have the nozzle at the end of a hose, would you do the calculation assuming the duct is the size of said nozzle and length doesn't matter (not worried about loss)?
Hello, I'm having a hard time coming up with a flow velocity out of a nozzle.
I have a fan that is putting 300 cfm of air through a 3" ID hose. The 3" hose is 45in long, and ends with a rectangular nozzle that has an opening 4.5" x 0.5".
Any help would be greatly appreciated.