Question on calculating flow velocity and selecting orfice size

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Question on calculating flow velocity and selecting orfice size

Post by Robert » Thu Mar 09, 2017 9:17 am

I have a machine that has a square tube header fed from a 4" water line at 20 PSI and around 65F. The header then has 20 orificed outlets that feed spray bars. 4 outlets feed each spray bar (the spray bars are a rectangle with a water line coming in each corner. Each spray bar has a hundred or more (depends on set up) holes around .125" (also depends on setup/product). my goal is to get around 15fps velocity from all the spray holes at 200gpm (measured back in the 4” pipe) and 25 fps at 360gpm. I have been playing with Bernoulli’s equation and various formulas derived from it that I have found on sites of companies that build or sell spray systems and components, but I don’t think I have all the data I need to calculate the velocity of the sprays. I do not have a good way to measure pressure drop across those orifices. Has anyone done something similar, and do you have formulas I could use to get the velocity at different orifice sizes?

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