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Friction factor
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1. Definition of friction factor
2. Calculation of friction factor
3. Hagen-Poiseuille relation
1. Definition of friction factor
The friction factor is representing the loss of pressure of a fluid in a pipe due to the interactions in between the fluid and the pipe.
f/2=friction factor - fanning
D=Pipe diameter in m
um=mean velocity in m/s
ΔPf=pressure drop due to friction in Pa
L=length of pipe in m
ρ=specific gravity in kg/m3
D=Pipe diameter in m
um=mean velocity in m/s
ΔPf=pressure drop due to friction in Pa
L=length of pipe in m
ρ=specific gravity in kg/m3
2. Calculation of friction factor
How to find the friction factor of
a pipe ? The different formula below allow you to calculate the
friction factor of a pipe.
In Laminar regime f/2=8/Re
In turbulent regime, different
correlations can be used
Blasius (only applicable
to smooth pipes) f/2=0.023.Re-0.20
Churchill (applicable for any Re and ratio e/D)
With e the pipe roughness in m
Another possibility is to use the
Moody Diagram which is actually a friction factor chart where the
friction factor can be read directly.
3. Hagen-Poiseuille relation
In Laminar regime, the volumic flowrate can be calculated thanks to the Hagen-Poiseuille equation
Q=volumic flowrate in m3/s
μ=dynamic viscosity in Pa.s
Source
Mecanique et Rheologie des fluides en genie chimique, Midoux, Lavoisier 1993, page 162, page 274-275