# The Equation for Volumetric Flow Rate?

8
I'm not sure how to clearly express my query, so I'll round up the gist of it. I understand that this is an entry level question.

I was told that, in order to calculate Volume Flow Rate (VFR), I would use these equations:

* Q = Velocity * Area [EQUATION 1]
* Q = Volume / Time [EQUATION 2]
Units: m^3 / s

Questions:
^Do I use both equations? Are they both deemed correct or only one and which one?
^Can you give an example problem or scenario in which I would use the appropriate equation?

Last edited: Nov 27, 2012
2. ### WillemBouwer

82
Example: You have a pipe with a diameter of 400mm. Water flows through the pipe at a velocity of 1 m/s. Determine how many liters you would have collected in a minute?

Use your equation as you mentioned and come up with a solution, don't et sidetracked by the units, do the first principals correctly...

8
@WillemBouwer Correct?

Prompt: A pipe has a diameter of .4 meters. Water flows through the pipe at 1 m/s. Determine how many liters (water) you would have collected in a minute?

Vinitial: 1 m/s
Volume: ?
Time: 60 seconds

Q = V * A
Q = 1 * (∏(.22))
Q = 0 .1256637061 m3/s

--> Q = V / T
.1256637061 = V / 60
Volume = 7.539822369 m3 or
7.539822369 * 1000 = 7,539.822369 L

1 m3 = 1000 Liters (L)

Last edited: Nov 27, 2012
4. ### WillemBouwer

82
There you go... Using the equation right...
The second equation is just an explaining of the units or terminology, Volume flowrate is exactly that, m^3/s, volume over time. But the first equation is the most commonly used.

However when you get a question, make sure to answer the question as asked with units, always remember your units... But you understand the principal! Cool beans...

So, how many liters per minute?

8
It should be on there.
7,539.822369 L ?
Thank you very much Mr. Bouwer. (:

6. ### WillemBouwer

82
No problem. I see it shows now, didn't the previous one, haha. good job though, correct answer...