Lecture 10

Fluid Mechanics II

Lecture 10
Muhammad Usman

Example 4
• A single acting reciprocating pump has a stroke of length
150 mm. The suction pipe is 7.5 meters long and the
ratio of plunger diameter to the suction diameter is 4/3.
The water level in the pump is 2.5 meters below the axis
of the pump cylinder, and the pipe connecting the sump
and pump cylinder is 75 mm diameter. If the crank is
running at 75 r.p.m. Find the pressure head on the piston
• In the begining of the suction stroke.
• In the middle of the suction stroke.
• In the end of the suction stroke.
• Take coefficient of friction as 0.01.

Example 5
• A double acting reciprocating pump has a
cylinder of 200 mm diameter and stroke of 400
mm. The pump delivers water toa height of 10
meters througha pipe 36 meters lond and 150
mm diameter at 40 r.p.m. Find the pressure in
the cylinder at the begining of the delivery
stroke, if a large air vessel is fitted in the delivery
pipe at teh same level of the pump, but 3 meters
from the cylinder. Take coefficient of friction to
be 0.008.

Manometeric Efficiency
• It is the ratio of manometric head to the
energy supplied by the impeller/kN of
water.

Example 6
• A centrifugal pump delivers 30 litres of
water per second against a head od 12
meters and runninng at 1200 r.p.m.
requires 6 kW power. Determine the
discharge, head of teh pump and power
required, if the pump runs at 1500 r.p.m.

Example 7
• A centrifugal pump was built to supply
water against a head of 22.5 mters. But
later on it was required to supply the
required quantity of water against a head
of 20 meters. Find teh necessary
reduction in the impeller diamter, if it
planned to reduce the original diameter of
300 mm without reducing the speed of
impeller.

Example 8
• Find the specific speed of a centrifula
pump, delivering 750 litres of water per
second against a head of 15 meters at
725 r.p.m.

Example 9
• A multistage centrifugal pump is required
to lift 9000 litres of water per minute from
a mine, the total head including friction
being 75 meters. If the speed of the pump
is 1200 r.p.m. Find the least number of
stages, if teh specific speed per stage is
not to be less than 60 r.p.m.

Example 10
• A single stage centrifugal pump with
impeller diameter of 300 mm rorates at
2000 r.p.m and lifts 3 m3 of water per
minute to a height of 30 meters. Find the
number of stages and teh diameter of
each impeller of a similar multistage pump
to lift 4.5 m3 of water per minute toa
height of 130 m when rotating at 1500
r.p.m.

Problem 1
• A single acting reciprocating pump has
plunger of diameter 150 mm and stroke of
length 400 mm. It draws water fram a
depth of 4.5 m through a pipe 8 m long
and 80 mm diameter at 25 r.p.m. If the
atmospheric pressure head is 10.3 find the
pressure head on teh piston at the
begining and end of the suciton stroke.

Problem 2
• A single acting reciprocating pump has plunger
of diameter 150 mm and stroke of 300 mm. The
lengths of suction and delivery pipes are 6.5 m
and 39 m respectively and both the pipes are of
teh same diameter of 75 mm. The axis of the
pump is 5 m above the level of the water in the
sump and 33 m below the delivery water level. If
the atmospheric pressure head is 10.3 m of
water and coefficient of friction of both pipes is
0.01. Find the pressure head of the piston at the
beginning, middle and end of the suction
strokes. Take speed of crank as 30 r.p.m.

Lecture 10

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Lecture 10