Pressure Vessel Discharge Time

[Casey96SS]

I am trying to calculate the amount of time it will take compressed air to discharge from a pressure vessel through an orifice.

Here are the varibles.

Vessel volume at 14.7 PSI: 11.52 cubic feet
Filled Pressure: 120 PSI
Volume of compressed air at 120 PSI: 94.04 cubic feet
Orifice Diameter: 3.75"

I originally calculated the amount of flow through a 3.75" orifice at 120 PSI. Then I determined the time by the amount of flow and vessel volume. I am having second thoughts about this because the flow is not constant as the vessel is discharging. The volume and pressure is decreasing which I believe would affect the discharge time.

Anyone have any thoughts or suggestions on this?

Thanks,

Casey

 

[Rich2001]

Here is a link for an approximation of pressurized gas discharge rate to atmosphere

http://www.cheresources.com/discharge.shtml

Vita sine litteris mors est.

 

[Casey96SS]

Thanks Rich, that was the information I was looking for.

 

[TD2K]

What is this calculation for? I looked at it (briefly) with a spreadsheet I have and got something in the order of less than 1/2 a second.

 

[quark]

I didn't dig into the details but total volume of compressed air in the receiver at 120psig receiver pressure is 105.56 cu.ft at 14.7 psia pressure.