Losses in
Pipe Flows
Major Losses: due to friction, significant head loss is associated
with the straight portions of pipe
flows. This loss can be calculated
using the Moody chart or
Colebrook equation.
Minor Losses:
Additional components (valves, bends, tees, contractions, etc) in
pipe flows also contribute to the total head loss of the
system. Their contributions
are generally termed minor losses.
The head losses and pressure drops can be characterized
by using the loss coefficient,
KL, which is
defined as
One of the example of minor losses is the entrance flow
loss. A typical flow pattern
for flow entering a sharp-edged entrance is shown in the
following page. A vena
contracta
region is formed at the inlet because the fluid can not turn a sharp
corner.
Flow separation and associated viscous effects will tend
to decrease the flow energy;
the phenomenon is fairly complicated. To simplify the analysis, a head loss and
the
associated loss coefficient are used in the extended
Bernoulli’s equation to take into
consideration this effect as described in the next page.
