I'm currently designing an air filtration system for the filling compartment of a beverage filler. The goal is to introduce HEPA filtered air at a rate of 2 CFM through a circular pipe opening with diameter of x inches. The air is provided by a compressed air system at a pressure of 120PSI (I plan on reducing this pressure through an air regulator) My problem is that I do not know how to calculate the air flow rate in CFM using the information I have (PSI and diameter/CSA). Is there a formula or method of determining the CFM from the above information and possibly other information I could easily find? Thanks for your help. T.K.