# The Naked Scientists Forum

### Author Topic: flow rate in pipes  (Read 2631 times)

#### Atomic-S

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##### flow rate in pipes
« on: 15/07/2007 05:25:35 »
What is the formula for the flow rate (e.g., litres/sec) of a liquid in a pipe of a given length and diameter, having a given pressure difference between the ends?

#### eric l

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##### flow rate in pipes
« Reply #1 on: 15/07/2007 08:37:56 »
Poiseulle's formula

D = [(π.r4.d)/8.η].[(p1-p2)/l]

with
• π = pi (or 3.1416)
• D = flow rate in kg/sec
• r = radius of the pipe in m
• d = density in kg/m3
• η = dynamic viscosity in Ns/m2
• (p1- p2) = pressure difference in N/m2
• l = length in m

You'll find this formula in any advance handbook on physics or engineering.  I copied it from "polytechnisch zakboekje", a Dutch pocketbook with all kinds of physical and chemical constants, formulae and other things useful for engineers.
I'm affraid it will require some converting to more traditional units.

#### Atomic-S

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##### flow rate in pipes
« Reply #2 on: 16/07/2007 06:20:25 »
Thanx; I knew it depended steeply upon the diameter, but was not sure just how steeply.

#### The Naked Scientists Forum

##### flow rate in pipes
« Reply #2 on: 16/07/2007 06:20:25 »