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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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