×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Calculating Flow Dynamics

Calculating Flow Dynamics

Calculating Flow Dynamics

(OP)
Trying to determine flow rate from one tank to another via a 3" SCH 80 PVC pipe. The tanks are exact same size and the 3" pipe is an equalization pipe between the two tanks. I would like to determine the flow from one tank to the other with a 1" solution differential.

Thanks

Mike

RE: Calculating Flow Dynamics

And your problem is?

There are many simple charts showing this. 1" differential is very low. Any length will result in very low flow

Why is this important?

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

RE: Calculating Flow Dynamics

Quote (Master Yoda)

Do. Or, do not. There is no try.

I recommend you refer to Crane Technical Paper No. 410. If you don't have it, buy it. It'll be the best $60 you ever spent. Crane TP410

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

RE: Calculating Flow Dynamics

(OP)
We have varying volumes of fluid coming into each tank from other sources. This pipe is used to equalize the two tanks. There is a point where the pipe will not be able to equalize the two tanks. We are trying to maintain the 1" differential and want to know how much flow there is between the tanks with 1" differential. In other words, if we pump too much too quickly into one tank to where the equalization pipe does not keep up it will overflow the tank.The equalization pipe is very short only about 18" long.

Perhaps you could point me to a chart. I would appreciate it.

Thanks,

Mike

RE: Calculating Flow Dynamics

With such a short pipe you can get a good estimate ignoring the friction in the pipe itself. All that is consuming your 1" of head is the resistance to getting the fluid into the pipe (i.e. the entrance loss) and accelerating the fluid to whatever velocity is achieved (i.e. the exit loss). These losses are expressed as Resistance Coefficients, commonly called K values. The Crane manual referred to above describes this in detail, or you can get a summary here.

The formula is h = KV2/(2g), or V=√(2hg/K)

h is the head, which you would have to express as 1/12 ft if the velocity is in ft/s
V is velocity in ft/s
g is acceleration of gravity = 32.2 ft/s2

If your pipe is welded flush to the tank wall then the entrance loss is K=0.5 and for the exit loss K=1.0, giving a total K of 1.5

This makes V = √(2 x 32.2 / (12 x 1.5)) = 1.89 ft/s
which is 38.8 USgpm in a 2.9" ID pipe. I would take off 15% for friction and safety and assume that the flow is 33 USgpm


Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

RE: Calculating Flow Dynamics

Trip spike, you won't get a better answer than that provided by katmar. At that length you might also be able to estimate flow by using a restriction orifice calculation, there are many online versions available then subtract a but for the pipe run, but the pressure loses are dominated by other things than the pipe friction as katmar says.

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

RE: Calculating Flow Dynamics

Or measure it and don't worry if you used the right equation. So many engineers love equations because they don't have to leave their desks and they get to use a computer. However, if you do not validate the calculation though some measurement it is basically worthless. Calculations are somewhat useful when designing something to build. Operations after construction will validate the calculations. Your system is apparently already built and operating.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources