# How to convert pressure (Bar) to flow rate (L/min)?

#### avishay

hii,

I'm try to calculate the pressure (in bar) needed for a certain flow rate 3 L/min of Argon gas given the following setup:
- I have a tank of Argon gas and the line pressure can be between 0 bar to 5 bar.
- The gas will flow out to the open air in the end.
- My pipe has an internal radius of 2.3mm.

I will be very happy if someone can also explain to me the process of getting to the answer...

Thanks for the help :)

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#### BvU

Homework Helper
Hello avishay, $\qquad$ $\qquad$ !

Your problem statement isn't complete: for a short pipe the pressure drop is less than for a long pipe.

With the expressions in the link you can calculate $\Delta p$ for your pipe length.

#### avishay

I didnt realy understod how to calculate this prameter, I'm not realy sure why i need this...
any help?
:)

#### russ_watters

Mentor
I didnt realy understod how to calculate this prameter, I'm not realy sure why i need this...
Pressure drop is a function of length or rather is given per unit length.

#### BvU

Homework Helper
calculate this parameter
It's not really a parameter: according to the link it's a result of a bunch of variables.

What have you calculated yourself so far ?

#### Chestermiller

Mentor
The methodology for solving a problem like this is presented in Chapter 7 of Transport Phenomena by Bird, Stewart, and Lightfoot. But, please note that, in a case like this where the gas pressure change can be as large as a factor of 6, you will need to take into account the compressibility of the gas, and, as such, will probably be working in terms of the square of the absolute pressure (rather than the absolute- or gauge pressure to the 1st power).

"How to convert pressure (Bar) to flow rate (L/min)?"

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