Fluid Flow
HEAD LOSS
HEAD LOSS
The head loss that occurs in pipes is dependent on the flow velocity,
pipe length and diameter, and a friction factor based on the roughness
of the pipe and the Reynolds number of the flow. The head loss that
occurs in the components of a flow path can be correlated to a piping
length that would cause an equivalent head loss.
EO 1.21
DEFINE the terms head loss, frictional loss, and minor
losses.
EO 1.22
DETERMINE friction factors for various flow situations
using the Moody chart.
EO 1.23
CALCULATE the head loss in a fluid system due to
frictional losses using Darcy’s equation.
EO 1.24
CALCULATE the equivalent length of pipe that would
cause the same head loss as the minor losses that occur
in individual components.
Head Loss
Head loss is a measure of the reduction in the total head (sum of elevation head, velocity head
and pressure head) of the fluid as it moves through a fluid system. Head loss is unavoidable in
real fluids. It is present because of: the friction between the fluid and the walls of the pipe; the
friction between adjacent fluid particles as they move relative to one another; and the turbulence
caused whenever the flow is redirected or affected in any way by such components as piping
entrances and exits, pumps, valves, flow reducers, and fittings.
Frictional loss is that part of the total head loss that occurs as the fluid flows through straight
pipes. The head loss for fluid flow is directly proportional to the length of pipe, the square of
the fluid velocity, and a term accounting for fluid friction called the friction factor. The head
loss is inversely proportional to the diameter of the pipe.
Head Loss fLv
2
D
Friction Factor
The friction factor has been determined to depend on the Reynolds number for the flow and the
degree of roughness of the pipe’s inner surface.
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HT-03
