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[Bold alien]

This is a basic question but I do not believe the final answer I get to be correct and need someone to point out the obvious to me.

I have a pipe and vessel with a combined volume of 5m3 and an operating pressure of 1barg.

A relief valve set at 175barg is relieving into this pipe work and vessel.

The relieving rate of the gas is 6000kg/hr with a molecular weight of 22.

The vessel is blocked in so I am looking to calculate the increase in pressure with time.

I calculated the compressed volume of the tank so 5/180 (p1*v1/p2=v2)

Then used the ideal gas law at constant temperature (127degC) and the volume above to calculate the given pressure at 1s, 2s, 3s using the molar flow rate adding this to the original pressure of 1barg each time.

I know to get a truly correct answer I would need to use hysys but am looking for a back of the envelope sort calc. Any comments on my method would be appreciated.

[PingPong]

I calculated the compressed volume of the tank so 5/180 (p1*v1/p2=v2)

Then used the ideal gas law at constant temperature (127degC) and the volume above to calculate the given pressure at 1s, 2s, 3s using the molar flow rate adding this to the original pressure of 1barg each time.

I don't understand what you are saying.

 

I do know however that the temperature of the gas in the tank will gradually rise because the gas is compressed by the incoming gas, so pressure will rise faster than you expect, but I don't think you are taking that into account.

 

Moreover there is heat transfer from the gas to the tank metal wall. And, if the tank is not insulated, there is heat transfer from the tank wall to the ambient air. Howeverm as I suspect that the tank will explode within very short timem the quantity of heat transferred may have little effect on the actual gas temperature.

Edited by PingPong, 25 September 2014 - 04:00 PM.