If I have a tank of volume V, pressure P, and temperature T, what is the most effective way to determine the volume flow rate if I were to suddenly allow the air to discharge through a hose? My first thought was that I could use Boyle's Law to determine the compressed volume of air in the tank: Vc = Va*(Pc/Pa) Where Va is the volume of the non-pressurized vessel, and Pa is atmospheric pressure. Then I could measure the pressure at certain time intervals (say, once every 5 seconds) and calculate a new compressed volume. From there I could calculate the average flow rate during that period as Q = (Va,2 - Va,1) / (t2 - t1) And if I take the measurements at even shorter time intervals I believe the result should tend toward the instantaneous flow rate. Am I on the right track with this? Should I be looking at compressible flow theory for a crude converging nozzle instead? Any help or feedback is greatly appreciated in advance!