CE 230-Engineering Fluid Mechanics

Lecture # 31-32

Minor losses

Characteristic curve of a pump

Parallel pipes

Components of head loss

Losses due to friction along the length of the pipe call MAJOR LOSS

Losses at localized regions like inlets, outlets, bends.. CALL MINOR LOSS

g

V

D

Lfh f 2

2

g

VKh Lm 2

2

Example 10.9Find the elevation of the left reservoir given:

D=15 cmQ= 0.028 m3/s

ν = 4x10-5 m2/sS=0.9

Characteristic curve of a pump

The head produced by a pump will depend on the discharge rate varying from maximum value when there is no flow and decreasing as Q increases.

The nature of this variation is unique for every pump and is usually supplied by the manufacturer as a curve called the characteristic curve of the pump.

Characteristic curve of a pump

If we place a pump of known c.c. in a pipe line and want to determine the head required from the pump apply the energy equation we could get an equation for hp

hp will be a function of Q (system curve)

Example 10.11Find the flow rate of water. The pump has the shown c.c.

f=0.015

hp=30+127Q2

Flow in parallel pipes

How much will flow in pipe 1 and 2?

Key concept is the head difference between ant two junctions in the same regardless of the path.

Pipe networks

Water distribution system

Hardy cross methodIterative procedureCEdelta hL=0