Last Rev.: 12 JUL 08
Pump Performance : MIME 3470
Page 1
Grading Sheet
~~~~~~~~~~~~~~
MIME 3470—Thermal Science Laboratory
~~~~~~~~~~~~~~
Laboratory №. 10
PUMP PERFORMANCE
Students’ Names / Section №
POINTS
SCORE
TOTAL
PRESENTATION—Applicable to Both MS Word and Mathcad Sections
5
5
5
GENERAL APPEARANCE
ORGANIZATION
ENGLISH / GRAMMAR
ORDERED DATA, CALCULATIONS & RESULTS—MATHCAD
PLOT PREFORMANCE CURVES FOR LOWER RPM CASE
PLOT PREFORMANCE CURVES FOR HIGHER RPM CASE
PLOT LOWER & HIGHER h vs. Q & SCALED UP LOWER CASE
20
20
20
TECHNICAL WRITTEN CONTENT
DISCUSSION—GENERAL DISCUSSION OF CALCULATIONS
HOW WELL DOES SCALED UP LOWER CASE MATCH & WHY?
KLINE-McCLINTOCK CALCULATION 
CONCLUSIONS
ORIGINAL DATASHEET
TOTAL
5
5
5
5
5
100
COMMENTS In gen., terminology of actual and theoretical are misleading in this and many experiments. Use power IN & OUT
d
GRADER—
Last Rev.: 12 JUL 08
Pump Performance : MIME 3470
MIME 3470—Thermal Science Laboratory
~~~~~~~~~~~~~~
Laboratory №. 10
PUMP PERFORMANCE
~~~~~~~~~~~~~~
LAB PARTNERS: NAME
NAME
NAME
SECTION
№
EXPERIMENT TIME/DATE:
NAME
NAME
NAME
TIME, DATE
~~~~~~~~~~~~~~
OBJECTIVES—of this experiment are to
1. Take the data necessary to map out the performance characteristics of a centrifugal pump at two different RPMs.
2. Then generate plots of these characteristics in the form of change
in head, power consumed, and pump efficiency vs. volumetric
flow rate.
3. Demonstrate the validity of turbomachinery scaling characteristics. This is achieved by scaling up the lower RPM head vs. flow
rate curve to the higher RPM curve.
INTRODUCTION—Pumps are machines that add energy to a
liquid in order to increase its pressure for different purposes. For
example, a pump may be used to move a liquid against gravity, or
to overcome friction in a pipe network.
The two basic types of pumps are:
1. Positive displacement pumps (PDPs), and
2. Dynamic or momentum-change pumps.
Positive displacement pumps have a moving boundary which forces
the fluid to flow by volume changes of one or more chambers within
the pump. Positive displacement pumps are characterized by a pulsating flow, high pressure increase, and low volumetric flow rate.
Examples are automotive piston with cylinder, sliding vane pumps,
and a mammal’s heart. Some advantages of PDPs are that they are
capable of delivering almost any fluid regardless of viscosity, and the
flow rate has only a weak dependence on the resistance against which
the pump is working (because of the “positive displacement”
associated with the volume changes within the pump).
Dynamic pumps add momentum to the fluid as it passes through an
impeller. The liquid injected at the center of a pump’s rotating blades
will be pushed to the circumference by centrifugal force. Dynamic
pumps generally provide a higher flow rate and a steadier discharge
compared to the PDP’s slower, pulsating flow; but, dynamic pumps
are not effective at all in handling high viscosity fluids. Dynamic
pumps are the most common and can be divided into three categories:
1. Centrifugal or radial flow,
2. Axial flow, and
3. Mixed (radial and axial) flow.
These pumps require priming.
OPERATION OF CENTRIFUGAL PUMPS—Most centrifugal
pumps are electrically driven; i.e., a pump is attached to the shaft of
an electric motor. The motor drives the impeller by supplying a
torque through a shaft. The impeller converts this mechanical energy
into hydraulic energy in the fluid.
The fluid is drawn into the pump
axially through the suction
(negative gage pressure) port of the
pump housing and then through the
eye of the impeller. The rotating
impeller
whirls
the
fluid
tangentially, and then centrifugal
action causes the fluid to move
http://www.kraftunitops.com/pump
radially outward. The centrifugal
_centrifugal.html
work done by the impeller on the
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fluid increases the fluid’s energy as it passes through the impeller.
The pump discharges the fluid at a velocity proportional to the motor
shaft speed and the setting of a downstream valve. The difference in
total energy between discharge and inlet openings represents the
energy added to the fluid by the pump. This increase in energy comes
from both the increased velocity as the fluid passes through the
impeller and the increased pressure. When the liquid exits the
impeller and enters the spiral casing (called the volute), most of the
dynamic pressure (velocity head) is converted into pressure head.
The fluid then leaves the volute through a tangential discharge port.
It is important to know how this energy varies with input power
and the amount of fluid pumped. Other essentials are the
efficiency of the pump (actually the impeller) transferring energy
from the motor to the fluid being pumped. These and other pump
characteristics are the subject of this experiment
Pump and Motor Characteristics
Impeller OD:
5”
№ of Impeller Blades: 6
Type of Impeller:
Open Type of Blades:
Backward Curving
Torque Arm Length: 5”
Motor Speed Range: 0-3000 rpm
Motor

Pump
(see below)
Volumetric
Measuring
Tank
 Torque Arm
Sump Tank
Weight Hanger 
Figure 1—Centrifugal Pump Testing Apparatus
Last Rev.: 12 JUL 08
Pump Performance : MIME 3470
EXPERIMENTAL PROCEDURE
The following characteristics are sufficient to completely define
the pump performance at any shaft speed (rpm):
1. Pump input torque (alternately, torque of the motor), T.
2. Pump shaft speed, N.
3. Rate of fluid discharge from the pump, Q.
4. Differential pressure across the pump, h.
5. Fluid velocities in the inlet, Vi, and outlet piping, Vo.
6. Difference in elevation between the suction and discharge
pressure taps.
If these characteristics can be measured experimentally, then the
pump’s performance can be adequately defined. In the laboratory
is a centrifugal pump test rig (Figure 1) with self contained sump
tank and a volumetric measuring tank. Each of the above
quantities can be found directly or calculated from data taken from
measurements using this testing rig.
The procedures for measuring each of these quantities follow.
1. Rate of fluid discharge, Q, from the pump—is determined by filling
the volumetric measuring tank to whatever level and noting the
time to do so. A vertical sight glass calibrated at 2 gallon increments
is on the outside of the tank. Record the level of water indicated and
then using a stopwatch record the time to fill the tank to some new
level and record the level and time duration. From these recorded
values, the pump discharge rate, Q, can be easily calculated.
Note that a manual diverter value is located on the top of the test
rig, so that the measuring tank can be either filled or bypassed.
There is also a drain valve at the bottom of the measuring tank.
Be sure to drain the measuring tank in preparation for the next
run; also, be sure to close the drain valve before the next run.
2. Pump input torque, T—Protruding from the motor’s side is a detachable trunnion mounted motor stator. Provided with the stator is a
weight hanger at a fixed distance from the center of the motor’s
shaft. Be sure to measure this distance in the lab. By adjusting the
weights on the hanger so that the motor housing is free-floating,
torque readings can be taken at different RPMs and flow rates.
3. Pump shaft speed, N—can be determined with a laser tachometer.
4. Differential pressure across the pump, h—Two Bourdon-type
gages are mounted on the test rig, one with a pressure tap near
the pump suction and the other near the discharge. The suction
gage indicates a gage vacuum (negative) pressure. The
discharge reads a positive gage pressure. Units may differ from
one gage to another. The differential pressure can be determined
from the difference between the two pressures.
Alternately, the differential pressure, h, can be obtained from
Bernoulli’s equation modified to account for the energy added
to the fluid by the pump. For an incompressible fluid and using
subscripts s and d to indicate suction (inlet) and discharge
(outlet) respectively this relation is
ps g c
V 2 Pg c
p g
V2
 zs  s 
 d c  zd  d
g
2g 
Qg
g
2g
h
This relation is used to find theoretical power.
Note the dimensions of each term in this relation are length. Thus,
the power term, Pgc/(Qg), is in fact a length indicating the energy
increase imparted to the fluid in terms of an equivalent fluid head
being pumped. This head rise can then be equated to the original
power term to find the theoretical power needed by the pump for a
Page 3
given set of conditions. This equation can be easily solved for the
head across the pump, h. Check the units carefully so that the
units of each grouping is length.
5. Fluid velocities in the inlet, Vi, and outlet piping, Vo—can be
found by taking the volumetric flow rate at a given setting and
dividing by the cross-sectional area of the suction or discharge
piping, respectively.
6. Suction/discharge pressure tap elevation difference, z—Just a
simple length measurement.
The actual pump power draw, P, can be found from the relation
P  2TN
The pump efficiency, , can be found by dividing the theoretical
power by the actual power draw and multiplying by 100.
For the report
1. For the lower RPM case, prepare a set of performance curves. That
is, graph on one plot efficiency, ; power, P; and head rise, h;
all plotted against the flow rate, Q.
2. Do the same for the higher RPM case.
3. On a single plot, graph both the higher and lower RPM cases’
experimental head rise, h, curves vs. flow rate, Q. On the same
plot, the lower RPM case h vs. Q scaled up to the higher RPM
case using turbomachinery scaling relations (see inset below).
They should match fairly well, verifying that such scaling
relationships do indeed work. In the scaling, note that for this
case the flow rate at a given point scales up as a ratio of the
RPMs, and the flow rate for the same point being scaled up
scales as the square of the ratio of the RPMs. Comment on how
well they do or do not match each other, and if not, why.
4. Considering that the only uncertainty in your data is due to the
Bourdon-type gages, use a Kline-McClintock method to determine
the uncertainty in the head rise across the pump. There is a separate
downloadable file describing the Kline-McClintock method.
Dimensional Analysis Given the variables defined above plus the
impeller diameter, Dimp, the following dimensionless parameters can
be determined from the principles of dimensional analysis:
Q
hg
P
,
,
.
5
3
2
Dimp
N 3 NDimp
Dimp
N2
Example: From product testing (Condition 1) it is found that
N1=900rpm, Dimp1= 5in, h1=10ft, Q1=3ft3/s, P1 = 2hp.
Predict the performance (i.e., h2, Q2, & P2) of an as yet undeveloped
pump having Dimp2 =15in, N 2 = 300 rpm.
 hg 
 hg 
10 ft g
h2 g

 
 
 2
2
2
2
 D2 N 2 
 D N2 






300rpm2
5
in
900
rpm
15
in
imp
imp

1

2
 h2  10 ft
 Q

 ND 3
imp

3
ft

 Q
3 s
 
 

3
3
 NDimp
1 900rpm5in 


P

 D 5 N 3
imp

3
ft

Q2 s
 
 Q2  27

3
 2 300rpm15in 


2hp
P
 


5
3
 D 5 N 3





5
in
900
rpm

1
ft 3
s

P2
 
5
3

 2 15in  300rpm
 P2  18hp
The first two parts of the example above can be used to scale h and
Q in this experiment.
Last Rev.: 12 JUL 08
Pump Performance : MIME 3470
ORDERED DATA, CALCULATIONS, & RESULTS
MATHCAD OBJECT--DOUBLE CLICK TO OPEN
Page 4
Last Rev.: 12 JUL 08
Pump Performance : MIME 3470
DISCUSSION OF RESULTS
How well does the scaled up case match the actual data. Why?
Answer:
Considering that the only uncertainty in your data is due to the
Bourdon-type gages, use a Kline-McClintock method to determine
the uncertainty in the head rise across the pump. There is a separate
downloadable file describing the Kline-McClintock method.
Answer:
CONCLUSIONS
Page 5
Last Rev.: 12 JUL 08
Pump Performance : MIME 3470
Page 6
APPENDICES
APPENDIX A —DATA SHEET FOR PUMP PERFORMANCE
Time/Date:
___________________
Lab Partners
____________________________
____________________________
____________________________
____________________________
____________________________
____________________________
Pump Suction ID, ds
Finest Gradation on
Suction Bourdon Tube Scale
_____2 in____
_________(______)
Pump Discharge ID, dd
Finest Gradation on
Discharge Bourdon Tube Scale
_____1.5 in___
Elevation of Suction Pressure Tap, zs
_________(______)
Elevation of Discharge Pressure Tap, zd _________(______)
_________(______)
Moment Arm for Torque Measurements, R _________(______)
LOWER SPEED CASE
Flow
Volume, Vol
(
)
Time, t
(
)
Torque Arm
Mass, m
(
)
Discharge
Pressure, pd
(
)
Suction
Pressure, ps
(
)

D
D
D
D
D
D
rpm






HIGHER SPEED CASE
Flow
Volume, Vol
(
)
Time, t
(
)
Torque Arm
Mass, m
(
)
D
D
D
D
D
D
An example set of curves from the web http://pump.net/liquiddata/performance.GIF
Discharge
Pressure, pd
(
)
Suction
Pressure, ps
(
)






rpm

Last Rev.: 12 JUL 08
Pump Performance : MIME 3470
Page 81