How can I calculate the flow to depressurizing in a pipeline???
How can I calculate the flow to depressurizing in a pipeline???
(OP)
How can I calculate the flow to depressurizing in a section of pipeline pressurized with air 60 psig?
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How can I calculate the flow to depressurizing in a pipeline???
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RE: How can I calculate the flow to depressurizing in a pipeline???
I don't mean to be flippant, but your question is really wide open. If you are depressurizing "a section of pipeline", the "flow" is whatever you can get through whatever size vent you have. As long as the system pressure is above a critical value (call it 10 psig), the flow out the vent will be at sonic velocity. For a given upstream pressure, you can calculate the mass flow rate of the air from the system at that velocity. As the pressure comes down, the mass flow rate associated with the sonic velocity will decrease, so the "flow" from the system is a continuously varying parameter down to the critical pressure.
After the critical pressure, velocity rapidly drops away from sonic, and determining flow at any given second is really difficult.
If I may be allowed to read between the lines, people more often want to know the time required to depressurize the system. That is pretty easy down to the critical pressure as long as you can determine the mass of air in the system. I usually calculate the time to critical pressure carefully, then multiply it times 4 to get the total elapsed time. My calculated time to critical is usually within a few seconds of actual. My total time is never very close. Sometimes I'm long, sometimes I'm short. I've been doing this a long time and have never found an equation that even sort of works for the last 8-12 psig.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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