University College Dublin

Fluid Mechanics 1 Laboratory Report

Module #: MEEN 20010 Experiment#: 1

Pump Laboratory report

Abigail Whitney
23325156

Stage: Stage 2 Mechanical Engineering

Date Performed: 20/09/2024
Lab Period: Friday 11am
Abstract-
This experiment investigates the characteristics of a centrifugal pump by analysing its
performance under various configurations, including single, series, and parallel
arrangements and investigates the effect of height on a siphon. The aim was to measure
the siphon and pump’s flow rate and pressure head using different tubing diameters and
observe how configurations affect output. It was found that increased height caused an
increased pressure gradient which in turn increased the flow rate of a siphon which was
attributed to Pascal’s Law. Also observed was the effect of differing diameter pipes had
on a pumps flow rate where it was found that a smaller diameter causes increased
resistance that reduces the flow rate. Finally, series and parallel pump configurations
were analysed however the expected results did not align with the experimental results
which was explain via the friction ratio. Understanding these characteristics and results
is essential for optimizing pump performance in industrial and household applications.

Introduction-
Figure 1, Ancient Roman
The following pump experiments are used to investigate a aqueduct [4]
pumps characteristics which are essential for moving fluids
such as water.

Water is essential to life on earth and the availability of water has

played a pivotal role in the development of all civilizations [3].
For centuries we have used gravity to move water as far back as
the roman aqueducts (figure 1) for distances as far as 100km [3].
The use of siphons in the following experiment uses this same
concept to move the water so it is easy to see their importance.

A centrifugal pump (which is used in these experiments) is a tool that transforms

mechanical energy into hydraulic energy through centrifugal activity and fluid pressure
in the pump [1]. It works by pushing water in a circular motion causing it to experience
centripetal force as velocity increases with radial distance [13]. This then causes lower
pressure at the centre (eye) of the pump that allows more water to be pulled in as some
exits. Priming the pump i.e. filling it with water is very important for this reason as if it
wasn’t primed and air was the fluid inside, its associated pressure drop wouldn’t be
enough to pull in the water. Pumps are used to move fluids and are commonly used in
the household and industry and play a massive part in the world we live in. Securing
water supply for the population of a city and also for development of agriculture for
example depend highly on the ability to transfer water and therefore pumps [3].

Pumps are arranged in different configurations to change the overall characteristics/

outcome (pressure head, flow rate, efficiency, etc.). The pressure head of a pump is the
pump’s ability to transport fluid to different heights [1].
A pump is defined by its characteristics and analysis of pump performance variations
under different operating conditions such as configurations. The aim of this laboratory
is to investigate a RS-M200S Micro pump by experimentally obtaining its pump head and
volume flow rates for different diameter tubing and analysing how an in series and in
parallel analysis effect its output. By investigating this pump or any pump allow for
easier and possibly more efficient usage of pumps for improvement of existing systems
or implementation of future projects.

Theory-
Each of the experiments for this laboratory involve fluid flow which is a result of pressure.
Pressure is the force per unit area measured in pascals (Pa). In fluids statics pressure is the
normal force exerted by a fluid per unit area. A Pressure gradient which is the change in pressure
from one place to another and causes fluid flow, fluid flows from regions of higher pressure to
lower pressure.

By analysing the sum of forces acting on a fluid element in the streamline direction of it (a fixed
trajectory) Bernoulli’s equation can be
derived. Bernoulli’s equation
Equation 1 – Bernoulli’s equation [12] (equation 1) states that the sum on
each side of equation 1 is constant, or the same at any two
points in an incompressible frictionless fluid [12]. Bernoulli’s equation is fundamental in
describing and analysing fluid kinematics i.e. flow and is used to explain how our siphon and
centripetal pump operates.

Fluid experiences the effect of gravity and therefore creates a pressure. The
pressure felt as a result of a fluid is due to the weight of the above fluid
Equation 3 - Pascal's Law [9]
and is governed by pascals law equation 2. P is the pressure, ρ is the
average density of the fluid in our case water, g is the acceleration due to gravity and h is the
height/depth of fluid causing the pressure. One can apply this equation as long as the density
changes are small over the depth considered [12]. This
equation can also be taken from bernouilli’s equation when
we consider static fluids (v=0m/s). Equation 3 shows Equation 2 - Bernoulli's law for static flow [12]
Bernoulli’s equation when the velocity of the fluid is 0m/s and rearanging it the change in
pressure can be seen to equal ρg(change in h) which is pascals Law. We will see that the
pressure caused by heigh h is a way of measuring the max pressure that a pump can overcome
called Pressure head (H).

Another observation taken from Bernoulli’s equation is for fluid with no change in height (h is
constant) which is the case for our pump configurations. It can be seen by rearranging equation
4 that a pressure change causes a change in velocity
i.e. kinetic energy. Therefore, it would suggest that a
drop in pressure would correspond to an increase in
Equation 4 - Bernoulli's equation for
constant h [12] velocity.
 A centripetal pump as seen in figure 2 consist of an impeller with curved vanes
that rotate in the pump housing [6]. The theory behind the operation of a
centripetal pump is circular motion and centripetal force. When the impeller
rotates there will be a centrifugal force on the liquid. This causes a pressure
rise in the liquid toward the outer edge of the housing and causes the liquid to
be dragged to the outside of the impeller where it is transported to the exit
Figure 2 – [6]
pipe. On the other hand, the moved liquid will create a low pressure at the Centripetal Pump
centre/eye, this then sucks in new liquid. The liquid enters the pump axially
and leaves the impeller radially [6].

To investigate pumps or pressure changes in fluid it is easiest to

measure the rate of fluid flow. In this laboratory we use volume flow rate
(Q). The volume flow rate is the amount of volume that per unit of time
flows through a section [6]. The volume flow Q is given by equation 5 Equation 5 - Volume flow rate [7]

and is measured in this experiment in units of ml/s however has standard unit
m3/s. Flow rate and velocity are related by the continuity equation equation 6.
Equation 6 gives the continuity equation as long as the flow is Equation 6 - Continuity equation
incompressable otherewise we would have to consider density so would for incompressible flow [7]
have to look at mass flow rate instead of volume flow rate (which are related by the equation Q =
m/ρ). If the Q is the same through 2 tubes the continuity equation is used to compare velocities
through the pipes as Q=Q therfore A1v1=A2v2 [7]. We can then see that a change in cross
sectional area of part of our system will effect the velocity of the flow which we will see in our
experiment.

With the rate of flow Q we can calculate the change in pressure with
Poiseuille’s equation (equation 4). Poiseuille’s law considers
everything that effects flow, P2-P1 is the pressure gradient, η is
Equation 7 – Poiseuille’s equation
[12]]
the viscousity of the liquid, l is the length it travels under the
pressure gradient and r is the radius of the pipe it travels in [12].
Another way to look at Poiseulli’s equation is that flow rate is equal to the pressure gradient
devided by the resistance R= 8ηl/πr4 [12].

In theory the arrangment of pumps

impacts the outputs/characteristics of
the pump set up. Arranging 2 pumps in
parallel should increase the flow rate
while maintaining the same pressure
head which is observed in figure 3.
Meanwhile arranging 2 pumps in
Figure 3 - Graph of Parallel operation
of 3 identical pumps [13] series increases the pressure head Figure 4 - Graph of Series operation
but maintains the same flow rate of 2 dissimilar pumps [13]
which can be observed in figure 4.
Methodolgy –
The following experiments involve testing performance under four different configurations: a
siphon at different heights, a single pump, two pumps in series, and two pumps in parallel. Flow
rate and pressure head were measured under each configuration.

Equipment needed for all experiments is in figure 5.

• 2 x plastic jug (one filled with ~500ml water)

• 2 x 1m long tubing with 3.2mm internal diameter (D)
• 1 m long tubing, 1.6 mm internal diameter
• 3 m long tubing with 3.2mm internal diameter
• 2 x 30 mm sections of 3.2 mm internal diameter
• 2 x Y-junction fitting
• 3m measuring tape. a
• Battery pack (3x NiMH AA) )
• Plastic syringe
• 2 x RS Pro Micro pump Figure 5 - Image of experiment
equipment
• Adhesive tape
• Stopwatch

Experiment 1 – Investigating a siphon

1. Using 2 surfaces of different height, place the water filled

jug (jug 1) on the higher surface and the other (jug 2) on the
lower surface (as in figure 6)
2. Place one end of the 1m long 3.2mm diameter tube into
one jug and the other end into the other. g
e
3. Measure the height difference between the 2 ends of the )
tubing in the jugs (as marked in figure 6) ) f
4. Prime the tube: Using the syringe suck some of the ) water
into the tube, at the tube end which is in the empty jug.
5. Place the tube back into the jug and observe the fluid flow
and start the timer.
6. Once the tube’s water flow starts to include air, stop the
timer and record the time.
7. Record the volume of water now in the bottom jug.
Figure 6 - Diagram and Image for experiment 1
8. Calculate the flow rate using equation 5.
9. Repeat for different smaller heights until there is no water flow.
Experiment 2 – Single pump characterisation

1. Connect the 1m long 3.2mm diameter tube to

the inlet port on the pump with the other end in
the water filled jug (jug 1) and the other 1m
long 3.2mm diameter tube to the exit port (inlet
and exit valves can be seen in figure 8) with the
other end in the empty jug (jug 2) as shown in
figure 7
2. Place the 3 batteries correctly into the battery pack and connect the
wires to the pump. Make sure to connect the positive to the positive
terminal and the negative to the negative terminal, the correct set up
can be seen in figure 7. The pump should now be powered on.
3. Prime the tube, with the syringe by sucking some water through the
Figure 7 - Diagram and image
tubing and pump via the tube end in jug 2. of experiment 2
4. Place the tube back into the jug and observe the fluid flow and start the timer.
5. Once the tube’s water flow starts to include air, stop the timer and record the time.
6. Record the volume of water now in the 2nd jug.
7. Calculate the volume flow rate using equation 5.
8. Repeat 2 times one for a different exit tube of diameter 1.6mm and one with no exit tube
placing the pump exit valve over jug 2.

Additionally with the same set up raise the 2nd jug with the tubbing inside until the
water flow stops and measure its height. Also find Q with no 2nd tube

Figure 8 - Diagrams and image of battery pump setup

Experiment 3 – Pumps in Series

1. Connect the pumps and tubing as seen

in figure 9. The first 1m 3.2mm diameter
tube from the water filled jug (jug 1) to the
inlet port of pump 1, the small 30 mm
section of 3.2 mm diameter tube from
the exit port of pump 1 to the inlet port of
pump 2 and the 2nd 1m 3.2mm diameter tube from the exit
port of pump 2 to the empty jug (jug 2).
2. Place the 3 batteries correctly into the battery pack and
connect the wires to the pump. Make sure to connect the
positive to the positive terminal and the negative to the Figure 9 – Diagram and image of experiment 3
negative terminal, the correct set up can be seen in figure 8.
 The pump should now be powered on. Do this for both pumps with the 2 separate
battery packs.
3. Prime the tube: with the syringe by sucking some water through the tubing and pumps
via the tube end in the 2nd jug.
4. Place the tube back into the jug and observe the fluid flow and start the timer.
5. Once the tube’s water flow starts to include air, stop the timer and record the time.
6. Record the volume of water now in the 2nd jug.
7. Calculate the flow rate using equation 5.
8. Repeat for a different exit tube of diameter 1.6mm.

Experiment 4 – Pumps in Parallel

1. Connect the pumps and tubing as seen in figure 10 The first 1m 3.2mm diameter tube
from the water filled jug (jug 1) to the Y-junction fitting, connect the 2 ends of the Y-
junction fitting to the 2 inlet ports of each pump, connect the 2nd Y-junction fitting to the
2 exit ports of the pumps and the other end to the 2nd 1m 3.2mm diameter tube to the
empty jug (jug 2)
2. Place the 3 batteries correctly into the battery pack and connect
the wires to the pump. Make sure to connect the positive to the
positive terminal and the negative to the negative terminal the
correct set up can be seen in figure 8. The pump should now be
powered on. Do this for both pumps with the 2 separate battery
packs.
3. Prime the tube: with the syringe suck some water through the
tubing and pumps via the tube end in the 2nd jug.
4. Place the tube back into the jug and observe the fluid flow and start the timer.
5. Once the tube’s water flow starts to include
air, stop the timer and record the time.
6. Record the volume of water now in the 2nd
jug.
7. Calculate the flow rate using equation 5.
8. Repeat for a different exit tube of diameter
1.6mm.
Figure 10 - Diagram and image of experiment 4

Results –
Experiment 1
Time [s] Volume [ml] Height [m] Flow rate [ml/s] change in pressure [Pa]
62 470 0.73 7.580645161 7139.8161
197 480 0.31 2.436548223 3031.9767
375 480 0.225 1.28 2200.62825
Table 1 – Experiment 1 Measurements and calculated flow rates and associated pressure change with
height difference using pascals law equation 3
 Experiment 2
Diameter [mm] Time[s] Volume [ml] Flow Rate [ml/s] Fluid velocity [m/s] Change in pressure [Pa] Head [m]
3.2 88 460 5.227272727 1.62494E-07 1269.450373 0.129533
1.6 280 300 1.071428571 1.33225E-07 4163.166439 0.424805
Pump Characteristics
No tube/max Q 78 430 5.512820513 1.71371E-07
No flow Q=0 0 0 0 29106.5643 2.97
Table 2 – Experiment 2 Measurements and calculated flow rates, fluid velocities and associated pressure
change needed calculated using Poiseuille’s equation (equation 7)

Pressure vs Flow rate

Pump curve

Tube curve
R1.6
Pressure

Tube curve
R3.2

Flow rate
Graph 1 – Pressure vs flow rate graph to show the pump and tube curves for analysis

Experiment 3 - In series
Diameter [mm] Time[s] Volume [ml] Flow Rate [ml/s] Change in pressure [Pa]
3.2 35 370 10.57142857 2567.285971
1.6 119 370 3.109243697 12081.34574
Table 3 – Experiment 3 Measurements and calculated flow rates and associated pressure change needed
calculated using Poiseuille’s equation (equation 7)

Experiment 4 - In parallel
Diameter [mm] Time[s] Volume [ml] Flow Rate [ml/s] Change in pressure [Pa]
3.2 67 360 5.373134328 1304.873063
1.6 215 350 1.627906977 6325.431179
Table 4 – Experiment 4 Measurements and calculated flow rates and associated pressure change needed
calculated using Poiseuille’s equation (equation 7)

Series Vs Parallel

Series

D3.2
Parallel
D1.6

0 2000 4000 6000 8000 10000 12000

Pressure [Pa]
Graph 2 – Histogram Comparing series and parallel flow rates for the 2 diameter tubes
Discussion –
Experiment 1

It was easy to see that the flow rate increases with increasing height and vice versa as seen in
table 1 and that fluid flow stops when there is no change in hight. Using Pascal’s law equation 3
the associated pressure changes with the height differences. Everything measured and
calculated is seen to agree with the theory discussed. It was mentioned that fluid moves from
higher to lower pressure and that the weight of the fluid causes a pressure which can be
measured using pascal’s law. With greater height of the 1st jug, we notice a higher pressure
change and therefore causes the greater volume flow rate seen and so when no height
difference is present there is no pressure gradient and therefore no flow.

Experiment 2

Firstly, the difference of flow rate between the 2 tube diameters was noticed in this experiment
and in table 2. The difference can be explained by using Poiseuille’s law discussed in the theory.
Equation 7 is Poiseuille’s equation and can be rearranged to see that Pressure is proportional to
flow rate and inversely proportional to the radius of the pipe to the power of 4 and so it is easy to
see that the greater the radius/diameter the less pressure required to achieve the same flow
rate. Poiseuille’s law was also described in terms of the resistance a flow feels. This means that
the greater the resistance the greater the pressure to obtain a certain flow rate is needed which
we can see is the case in table 2. All of this was most easily observed in graph 1 where the tube
curves were plotted, the smaller diameter tube is seen to have a much steeper slope than the
larger diameter this corresponds to a larger resistance as again in the theory we said that flow
rate is equal to the pressure gradient devided by the resistance and the slope of our graph is the
pressure divided by the flow rate. Equation 4 is a variation of Bernoulli’s equation and we said
showed that a drop in pressure would result in an increase in velocity, in table 2 the 3.2mm
diameter tube has a lower pressure and a higher velocity than the higher pressure 1.6mm
diameter tube which once again affirms the theory.

Also achieved from experiment 2 was the pressure head i.e. the max height the pump can
overcome to cause fluid flow. It was measured at 2.97m which corresponds to a pressure of
29kPa calculated using equation 3. Using this value and the calculated value for the max flow
rate which was achieved by not having a second tube and therefore not having any resistance,
the pump characteristic curve could be plotted as in graph 1. This is a very useful way to analyse
a pump as it allows you to read the maximum flow rate for any given head value.

Putting the tube curves and pump curves together in graph 1 allows the max flow rate and head
of each tube to be read as well via the tube curves intersection with the pump curve. This is very
useful and is done for nearly all pumps as a way to analyse and decided on the best
configurations and what its limitations are.

Experiment 3 and 4
The individual results of experiments 3 and 4 show the same results as experiment 2 and further
cement that the smaller diameter tube has a smaller volume flow rate and can be seen in both
table 3 and 4. However the more important observations of the experiments come from
comparing the 2 experiments. In graph 2 it is clear that the flow rate was much higher in series
than parallel. This does not align with the theory as it would have been expected that the series
pumps would have similar flow rate to that of the singular pump although its pressure head
would have increased and that the parallel pumps would have had an increases flow rate and a
similar pressure head. The best way to explain this is to consider the friction ratio. The friction
ratio is the ratio of the difference between the total head and friction head to the total head [13].
Where the friction head is the head lost by flowing water as a result of friction and just like your
average friction it increases the faster the water flows.

Parallel pumping is best reserved for systems where the friction ratio is low [13]. However, for
our pump and tube set up as seen in graph 1 there is a relatively low-pressure head and
therefore the friction ratio is very high as the parallel configuration doesn’t increase the pressure
head. This friction head coupled with the relatively high velocity causes increased turbulence
which all in all prohibits the expected output of an increased flow rate although there is a slight
increase from the single pump observed between table 2 and 4.

The expected outcome of a series configuration is to increase the pressure head and is best
reserved for systems where the friction ratio is high, this is because if a single pump has to
operate, there may be an issue of insufficient pump head to meet the minimum static head [13].
In our case we seen that the flow rate of the series pumps was much higher than that of the
single pump. The series configuration does not have the same problems with friction head as it
generates a larger head that overcomes the friction head and reduces the friction ratio. This
could explain the increased flow rate over the parallel as it means the resistance was
significantly lower in the series configuration over the parallel and therefore had faster flow rate.

Conclusion –
Key findings

• The flow rate through a tube between different heights was seen to increase with
increasing height. This was attributed to an increase in the pressure change which is
described by Pascal’s Law.
• Flow rate through a tube can be described by Poiseuille’s Law. It was shown that with
increased resistance caused by a smaller radius tube a greater pressure difference is
required to create a specified fluid flow rate.
• Visual analysis of pressure vs flow rate is achieved with a pump characteristic curve and
demonstrates how resistance impacts pump performance.
• The series configuration of our pump is capable of overcoming a higher friction
resistance and therefore has a greater performance causing the flow rate to increase.
Meanwhile, the parallel configuration of our pump is hindered by friction and turbulence
which causes the anticipated increase of flow rate to be negligible especially at higher
velocities.
Future work

For future work it would be beneficial to measure the pressure head of the 2 pump
configurations as well as the singular pump to also check that the theory for its values align with
the experimental values.

References –
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and Parallel. Rekayasa Mekanika, 5(2), pp.41-46.
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