Blast Pressure Calc for Pneumatic Test Chamber

[wallace24]

I am designing a blast chamber to contain potential failure of a pressure vessels tested with air. In order to do this, "the available energy released by isentropic expansion of the fluid from rupture conditions to one atmosphere" must be calculated. I'm more than a little rusty on thermo!
The largest vessel that will be put into the chamber would be 400 gallons, at ambient temp(60degF) and at a test pressure of 404.7 psia.
Can anyone help me?
Any other info on this would be helpful too.
Thanks.

 

[spayette]

The stored energy (U=Internal energy, ft-lb) in a pressurized volume filled with a gas can be estimated by referring to a method in the Lawrence Livermore National Laboratory ES & H Manual. The required parameters are as shown below.



P1= Vessel or piping pressure, psia
P2= Atmospheric pressure, psia
V1= Volume of vessel or piping, ft3
k= Ratio of specific heats (k= 1.66 for He; k= 1.41 for H2, O2, N2, and air)

The internal energy “U” can be compared with the potential energy release in TNT. One pound of TNT contains the explosive equivalent of 1,551,000 ft-lb. (LLNL ES & H Manual)

The pressure from a blast can be approximated, if you care to obtain this additional data, by using Hyde’s equation (referenced in several Internet sources).

 

[sailoday28]

The original question was posted on forum for thermodynamics thread391-122701