Minor Losses In Pipe

 

Minor losses mean losses due to local disturbances of the flow in conduit. Minor losses can be expressed as:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Loss of Head at Entrance

• The streamlines continue to converge and with maximum velocity and minimum pressure exist.

• The minimum flow area is known as vena contracta.

 

 

 

 

 

 

 

 

 

 

 

 

 

Loss of Head At Submerged Discharge

 

 

 

A) Discharge Into Still Water

 

• Discharge from the end of the pipe into closed tank or reservoir

• Velocity is large ,kinetic energy is dissipated

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

B) Discharge into Moving Water

• Discharged enter a body of water moving away in a channel

• Discaharge loss is equal to the difference between the discharged and ultimate velocity heads.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Loss Due to Contraction

• There is a drop in pressure due to the increase in velocity

• Loss of energy in turbulence

 

 

 

 

 

 

 

 

 

• To reduce the loss of head, it can be changing one diameter to the other with smoothly curved transition (with or with frustrum of a cone (with , and angle 20 -40 )

 

 

 

 

 

 

 

 

 

Loss Due to Expansion

• There is a rise of pressure due to the decrease in velocity

• Excessive turbulence

• Eddy currents are created

 

 

 

 

 

 

 

• To reduce the head loss, a diffuser can be used.

• This will results gradual expansion

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Loss in Pipe Fitting

• The loss coefficient k depends on the type of fitting

 

 

 

 

 

 

 

 

 

 

 

Loss in Elbows and Bends

• There is an increase in pressure (outer wall) and a decrease in pressure (inner wall)

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• Most of the head loss due to a sharp bend may be eliminated by using a vaned elbow.

• The vanes impede the formation of the secondary flows.