Pressurizing a Vessel with Air 1

[kryanl]

I am having trouble trying to figure out in a ballpark way, how to determine what flow rate of air is needed to pressurize a vessel to a known pressure, in a set time. I.e, a 8,500 ft3 vessel to 5 psig in 30 min. The inlet line size will be determined at a later date. I vaguely remember from school a couple simple equations that can be used, but all I can think of at the moment is Q=(rho)*A*V, and that doesn't help, since it doesn't deal with pressure. I appreciate your help.

Kayla

 

[insideman]

Howdy!

Let's assume the tank is initially filled with air at 14.7 psia with air weighing .075 lb per cubic foot. Then the initial weight of air in the tank is .075 lb/ft^3 X 8500 ft^3 = 637.5 lb.

Tnen let's assume the tank is filled at constant temperature to 19.7 psia.

New weight is 637.5 X 19.7/14.7 = 854.34 lb.

New weight minus old weight = 854.34-637.5 = 216.34 lb.

To fill in 30 min, flow rate = 216.34/30 = 7.23 lb/min.

To change this to SCFM, divide by standard weight density (.075).

Flow rate = 7.23/.075 = 96.37 scfm.

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