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How to calculate pressure increase from expanding gas
3

How to calculate pressure increase from expanding gas

How to calculate pressure increase from expanding gas

(OP)
It has been over 20 years since I studied Thermo. I am trying to run safety calculations on a pressure vessel. The PV contains batteries than may generate gas under certain conditions. I know the size of the PV and the volume of gas generated by the batteries.

How do I determine the change in pressure inside of the PV? The phyical size of the chamber does not change so Boyle's Laws do not fit (P1V1=P2V2) because V1 = V2.

The problem sounds easy ie the volume of gas inside of the cylinder increases by say 100 cu in so what is the new pressure? What are the governing equations?

RE: How to calculate pressure increase from expanding gas

2
Don't forget n, those pesky moles.

You are creating gas that wasn't there before, the number of moles of gas is not constant.

P1V1/T1n1 = P2V2/T2n2

RE: How to calculate pressure increase from expanding gas

presumably the volume of gas created is at STP conditions, then P1 = normal atmosphere pressure and V1 = tank volume + battery gas volume and V2 = tank volume, so
P2 = Psl*(Vt+Vg)/Vt  

RE: How to calculate pressure increase from expanding gas

(OP)
Aerospace:
Can I assume you meant to type: P2 = P1*(Vt+Vg)/Vt

RE: How to calculate pressure increase from expanding gas

yeah P1 = standard pressure = sea-level pressure = 1 atm

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