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Minor energy (head) losses
Loss of head due to sudden enlargement
Loss of head due to sudden contraction
Loss of head at the entrance of a pipe
Loss of head at the exit of a pipe.
Loss of head due to bend in pipe.
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Loss of head due to sudden enlargement
As a result of sudden enlargement, liquid flowsforming eddies at the corners.
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Loss of head due to sudden contraction
It is due to the sudden enlargement which takes
place after vena-contracta The cross-sectional area of the stream tube becomes the
minimum and less than that of the smaller pipe. This section
of the stream tube is known as vena contracta
hc = (0.5V22/2gf)
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At vena contracta, the velocity is maximum
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Loss of head at the entrance of a pipe
There is sudden contraction to flow of liquid
which results in loss of head
The loss of head at the entrance to the pipe is
therefore given by
=
and is known as entry loss.
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Loss of head at the exit of a pipe
Hexit = V2 / 2g
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Loss of head due to bend in pipe
Loss due to change in velocity and the
direction of flow
Hb =
kV2/ 2g
where, V = velocity of flow
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Laws for fluid friction
Frictional resistance is independent of pressure.
Frictional resistance is proportional to velocity offluid.
Frictional resistance is proportional wetted
surface area. Frictional resistance is independent of nature of
surface in contact.
In streamline flow, friction varies greatly with
temperature.
If velocity of fluid is below critical velocity,flow is viscous flow
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Frictional resistance for turbulent flow
Proportional to v2
Proportional to the density of fluid
Proportional to the area of surface in contact Independent of pressure
Dependent on the nature of the surface in
contact.
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Hydraulic gradient
Imaginary line drawn above the axis of pipe sothat at vertical distance from any point to the
axis represents the pressure head at that point
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Total energy line
The sum of potential head, pressure head and
velocity head is known as total head.If a line joining the total heads at various points, the
line so obtained is called total energy line.
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Power transmitted through pipes
Power transmitted through pipe depends
upon:
1: weight of liquid
2: total head available at the end of pipe.
Then head available at outlet of the pipe
= Total head at inlet
Loss of head dueto friction
= H - hf
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Power transmitted through pipes
= (weight of liquid flowing per sec)
X (head at outlet)= (w * volume of liquid flowing per sec)
X (head at outlet)
= (w * area * velocity of liquid)
X (head at outlet)
Efficiency of transmission
= ( Power at outlet) / (Power at inlet)
= W(H-hf) / WH
= (H- hf)
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Water hammer
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Water hammer
It's also called hydraulic shock.
Water hammer commonly occurs when a valve
closes suddenly at an end of a pipeline system, and a
pressure wave propagates in the pipe. Damage to the pipe due to sudden rise in pressure.
The increase in pressure depends upon velocity of
flow, speed at which valve is closed, length of pipe,material of pipe.
http://en.wikipedia.org/wiki/Pipeline_transporthttp://en.wikipedia.org/wiki/Pipeline_transport -
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Pipes in series
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Pipes in series
Q = Q1= Q2= Q3
Q = A1V1= A2V2
hL= hL1+ hL2+ hL3
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