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# Gas Flow Rate

## Gas Flow Rate

(OP)
Hello,

I am working on a problem to calculate the gas flow rate from a pressurized tank to another tank at 0 psi. Initially, the tank outside the building is at 150 psi. It is connected to smaller tank inside thru 0.25" pipe with a closed valve. The gas is O2. The length of pipe is 75ft. The volume of tank inside is 25 in^3. When valve is opened the tank inside equilibrate to 140psi in just 11.2 seconds.
The flow rate I am interested in is the average value. Is it just a matter of using idea gas law to calculate the flow rate.. Is it right to assume the flow rate is just the volume of tank inside divided by time?

### RE: Gas Flow Rate

I think that's the definition of average...

You must be going at sonic velocity at the start though.

I'm not sure I want to do that in oxygen.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Gas Flow Rate

If this is a real world problem then you should be careful when flowing O2 (as Littleinch also mentions)

--- Best regards, Morten Andersen

### RE: Gas Flow Rate

But to answer your question i also second what littleinch says here: Flow is probably choked somewhere in the tube. This will limit the flow and the flow rate will be fairly constant until you receiving bottle is almost full. So as you suggest you can use ideal gas law to calculate the increase in moles in the bottle and then use an average molar flow, convert that to mass flow or what ever you need. But you should also notice that your bottle gets hotter?

--- Best regards, Morten Andersen

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