Example: Darcy’s Head Loss Equation
A pipe 100 feet long and 20 inches in
diameter contains water at 200°F flowing at a mass flow
rate of 700 lbm/sec. The water has a density of 60 lbm/ft3
and a viscosity of 1.978
x 10-7
lbf-sec/ft2.
The relative roughness of the pipe is 0.00008. Calculate the
head loss for the pipe.
Solution:
The sequence of steps necessary to solve this
problem is first to determine the flow velocity.
Second, using the flow velocity and the fluid properties
given, calculate the Reynolds
number. Third, determine the friction factor from the
Reynolds number and the relative
roughness. Finally, use Darcy’s equation to determine the
head loss.
Use the Moody Chart for a Reynolds number of
8.4 x 107
and a relative roughness
of 0.00008.
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