Pressure Drop and Volumetric Flow Rates in Pipe Systems

The experiment aimed to investigate the characteristics of fluid flow in different pipes, including orifice plates, nozzles, and Venturi tubes. The results showed that each type of pipe had its unique characteristics, with the pressure drop increasing as the velocity of the fluid increased. The potentiometer setting was found to affect the air flow rate significantly, with higher settings resulting in greater airflow rates. The experiment also highlighted the importance of using a manometer with a small internal diameter for Pitot tubes to improve their sensitivity and accuracy. Additionally, the different pipe bends were found to have varying pressure drops due to friction and resistance to fluid flow.

AIM
The aim of this experiment is to determine the characteristics of fluid flow of a various tube and
plate in a Gunt flow system.
Equipment
1. Orifice plate
2. Nozzle plate
3. Venturi tube
4. Iris diaphragm valve
5. Pitot tube
6. PVC pipes
7. Hoses
8. Flexible hoses
9. 16 manometers panel
10. anemometer
11. electrical air blower
EXPERIMENTAL
Firstly, a long pipe with 2 sections was unscrewed and pushed away slightly. Between the
spaces created, an orifice plate was installed and screwed between them. Not to forget to
mention, one of the pipe was attached to a fan. Then, hoses were used and attached to the
inlets on the manometer panel. Before doing anything, the potentiometer was set into zero. As
the fan was turned on afterwards, air velocities was recorded for each potentiometer for the
experiment, which is 5, starting from 2. The difference of water level was measured as well.
Steps taken was repeated for the other plate, which is nozzle.
Another thing that were used in this experiment is the pilot tube. Using panel 19 and 20, those
panels were attached to the hoses. Specifically, the hoses that were used were I and J as it were
smaller in diameter. The experiment carried out in five different potentiometer settings with
five different vertical distances from the centre of the pipe.
Alternatively, a venture tube was also used and measured in this experiment. Varying
diameters on the tube, the panel inlets that were used for the hoses were number 21 until 26.
It was recorded with five different potentiometer settings starting from 4 to 9, and also the
airflow for each settings.
Lastly, the venture tube was replaced with diaphragm valve, using panel inlets number 17 and
18 attached to the hoses. The potentiometer settings that were used are 2 until 6.
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RESULT and DISCUSSION
ORIFICE PLATE AND NOZZLE
Table 1: Orifice plate calculated parameters for air flow
Potentiometer settings ∆H / mm ∆P / N.m-2 √∆p / N0.5.m Air Velocity / m s -1
2 6 58.7 7.7 1.40
3 10 98.1 9.9 2.20
4 13 127.5 11.3 2.80
5 17 166.8 12.9 3.70
6 27 264.9 16.3 4.40
7 37 363.0 19.0 5.30
8 53 519.93 22.8 5.90
Table 2: Nozzle plate calculated parameters for air flow
Potentiometer settings ∆H / mm ∆p / N.m-2 √∆p / N0.5.m Air velocity / m s -1
2 11 107.9 10.4 0.65
3 15 147.2 12.1 1.20
4 20 196.2 14.0 1.80
5 30 294.3 17.2 2.20
6 40 392.4 19.8 2.60
7 50 490.5 22.1 3.00
8 65 637.7 25.3 3.50
∆H : Height difference of water on the manometer (mm)
∆p : differential pressure (N.m-2)
√∆p : square root of the differential pressure (N0.5.m)
Figure 1: comparing air flow velocities (m.s-1) vs √ΔP (N0.5.m) comparing the orifice and nozzle
plates
2

The equation used to find the differential pressure on the table above:
∆ p=ρw × g × Δhw=1000 × 9.81× Δhw( based onthe table givenabove )
Based on the table shown above, it is safe to suggest that the orifice plate has bigger pressure
drop than the nozzle plate. Pressure drops in this experiment means that there were a lot of energy lost
due to the friction inside the tube.
From the graph, it was found that the gradient of both graph were different from each other, for
the orifice plate, the equation that was found from the orifice plate graph is y = 0.3025x - 0.6456, while
from the nozzle plate, y = 0.1814x - 0.9975. Comparing both gradients, there was a pretty huge gap
between them, therefore an average from it was used for the expression for flow on both plates. Hence,
y = 0.24.
V 1=constant × √ ΔP=0.24 × √ ΔP
PILOT TUBE
Table 3: Pilot tube calculated parameters for air flow
Potentiometer
settings
∆H / mm ∆p / N.m-2 √∆p / N0.5.m Vertical distance
y (mm)
Air velocity / m s -1
3 3 29.4 5.4 -40
3.8
3 3 29.4 5.4 -20
3 6 58.9 7.7 0
3 6 58.9 7.7 20
3 3 29.4 5.4 40
4 4 39.2 6.3 -40
3
5 10 15 20 25 30
0
1
2
3
4
5
6
7
Orifice Plate Linear (Orifice Plate)
Nozzle Plate Linear (Nozzle Plate)
√∆p / N0.5.m
Air velocity / m s -1

5.2
4 9 88.2 9.4 -20
4 10 98.1 9.9 0
4 10 98.1 9.9 20
4 3 29.4 5.4 40
5 5 49.0 7.0 -40
6.2
5 12 117.6 10.8 -20
5 14 137.2 11.7 0
5 13 127.4 11.3 20
5 6 58.9 7.7 40
6 10 98.1 9.9 -40
7.8
6 17 166.8 12.9 -20
6 22 215.8 14.7 0
6 18 176.4 13.3 20
6 11 107.9 10.4 40
7 20 196.0 14.0 -40
9.4
7 30 294.0 17.1 -20
7 33 323.73 18.0 0
7 30 294.0 17.1 20
7 15 147.0 12.1 40
Table 4: Pressure affecting volumetric flowrate
Potentiometer
settings
∆p / N.m-2 Area of pipe / m2 Volumetric flow rate / m3 s-1
3 29.4 5.62 × 10-3 676.1
4 39.2 5.62 × 10-3 925.3
5 49.0 5.62 × 10-3 1103.2
6 98.1 5.62 × 10-3 1387.9
7 196.0 5.62 × 10-3 1672.6
Figure 2: comparing vertical distances vs √∆p / N0.5.m in each potentiometers settings
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Figure 3: comparing volumetric rate and pressure differences at the centre of the pipe
The figure 2 above shows the root of differential pressure changes due to the vertical distances
in each potentiometers, while the third one shows the pressure differences affecting the volumetric flow
rate in the centre of the pipe.
As it shown in the table above, the velocity of air flow continuously increasing for the increase
of each vertical distances. The reason for these characteristics is related to turbulent flow, not laminar
flow. To recognize the symptoms, the following formula were used:
ℜ=× Vd i
❑
 = Fluid density (kg/m3)
V = average velocity of the fluid (m/s)
di = internal diameter of pipe (m)
 = fluid dynamic viscosity (Ns/m2)
5
4 6 8 10 12 14 16 18 20
-50
-40
-30
-20
-10
0
10
20
30
40
50
Setting 3 Setting 4 Setting 5 Setting 6 Setting 7
√∆p / N0.5.m
Vertical distance (mm)
20 40 60 80 100 120 140 160 180 200 220
0
200
400
600
800
1000
1200
1400
1600
1800
∆p / N.m-2
Volumetric flow rate / m3 s-1

Where the density of air is 1.177 kg/m3, and the fluid viscosity of air 1.846×10−5 Ns/m2. Hence:
ℜ=1.177 x 4.3 ×84.6 x 10−3
1.846 ×10 −5 =23194.4
Since Re > 4000, then it is a turbulent.
VENTURI TUBE
Table 5: measured and calculated parameters value for venture tube
Potentiometer
settings
Measuring
points
Href
(mm)
∆H (mm) ∆p
(N.m-2)
√∆p
(N0.5.m)
Air velocity
(m.s-1)
4
21
183
0 0.00 0.00
6.6
22 5 68.6 8.3
23 17 166.6 12.9
24 12 117.6 10.8
25 4 39.2 6.3
26 2 19.6 4.4
5
21
186
0 0.00 0.00
8.4
22 10 98.0 9.9
23 39 382.6 19.6
24 23 225.6 15.0
25 9 88.3 9.4
26 6 58.8 7.7
6
21
192
0 0.00 0.00
10.0
22 14 137.3 11.7
23 57 559.2 23.6
24 33 323.7 18.0
25 14 137.3 11.7
26 8 78.4 8.9
7
21
200
0 0.00 0.00
12.0
22 20 196.0 14.0
23 79 775.0 27.8
24 45 441.5 21.0
6

25 20 196.0 14.0
26 12 117.6 10.8
8
21
210
0 0.00 0.00
14.0
22 28 274.7 16.6
23 106 1039.9 32.2
24 60 588.6 24.3
25 17 166.8 13.0
26 15 147.0 12.1
Figure 4: relationship between √∆p (N0.5.m) and air velocity on measuring point 23
Figure 5: relationship between measuring point vs ∆p (N.m-2) in settings 4
7
1 2 3 4 5
0
5
10
15
20
25
30
35
Air velocity (m.s-1)
√∆p (N0.5.m)

Figure 6: relationship between measuring point vs ∆p (N.m-2) in settings 5
Figure 7: relationship between measuring point vs ∆p (N.m-2) in settings 6
8
1 2 3 4 5
0
20
40
60
80
100
120
140
160
180
measuring points
∆p
(N.m-2)
1 2 3 4 5
0
50
100
150
200
250
300
350
400
450
measuring points
∆p
(N.m-2)

Figure 8: relationship between measuring point vs ∆p (N.m-2) in settings 7
Figure 9: relationship between measuring point vs ∆p (N.m-2) in settings 8
9
1 2 3 4 5
0
100
200
300
400
500
600
measuring points
∆p
(N.m-2)
1 2 3 4 5
0
100
200
300
400
500
600
700
800
900
measuring points
∆p
(N.m-2)

First of all, the measuring point number 23 was used since it has the smallest diameter,
therefore it has the maximum pressure drop. From figure number 4 above, it shows that the pressure
was frequently increasing with the higher velocity it gets, hence it is proportional. From the table above,
the measuring point number 21 was shown as the reference for the other measuring points, hence from
there, the ∆H of the water manometer can be found. To be specific to the points, both points 21
and 26 were actually have the same diameter. Nevertheless, in point 26, it has a sudden
enlargement in the pipe, while in point 21 it remains constant, hence no pressure drop.
IRIS DIAPHGRAM
Table 6: measured and calculated values for parameters air flow in iris diaphgram
Potentiometer
settings
∆H (mm) ∆p
(N.m-2)
Air flowrate (dm3.s-1) % valve opening
diameter
0 0 0.00 0
10.8
2 4 39.2 11.0
3 9 88.3 15.0
4 14 137.3 20.0
5 27 264.6 27.0
6 37 363.0 30.0
0 0 0.00 0
21.7
2 3 29.4 17.0
3 9 88.3 20.0
4 13 127.4 25.0
5 25 245.0 35.0
10
1 2 3 4 5
0
200
400
600
800
1000
1200
measuring points
∆p
(N.m-2)

6 35 343.4 38.0
0 0 0.00 0
39.8
2 4 39.2 19.0
3 8 78.4 29.0
4 12 117.6 33.0
5 23 225.6 45.0
6 30 294.0 50.0
0 0 0.00 0
54.2
2 4 39.2 25.0
3 7 68.6 33.0
4 11 107.8 41.0
5 17 166.6 59.0
6 27 264.4 71.0
0 0 0.00 0
71.1
2 2 19.62 26.0
3 6 58.8 39.0
4 10 98.0 50.0
5 15 147.1 66.0
6 20 196.0 82.0
0 0 0.00 0
85.5
2 1 9.8 34.0
3 4 39.2 49.0
4 6 58.8 66.0
5 9 88.3 70.0
6 15 147.1 89.0
Figure 10: air flow rate vs % valve opening diameter in iris diaphragm
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The following formula were used to find the % valve opening diameter:
% valve opening diameter=(diameter of valve – 38.5)
41.5 ×100 %
Since 38.5mm is the fully closed diameter of valve, and 41.5mm is the difference (80-38.5 = 41.5 mm)
Table above shows that the airflows increased as the potentiometer was increased, hence it is
proportional. The figure above also shows the relationship between the valve opening diameters and
the air flowrate for each settings of potentiometers.
CONCLUSION
In conclusion, each type of pipes has each characteristics that only can be found with
experiment such as this one. The biggest part of this experiment that played the most is the
potentiometer. For each settings, it could affect each of the pipes effectively. Most part of it,
the aim for this experiment has been achieved.
However, there are few errors that was caught during the experiment. One of the errors were
the accuracy of the water height recorded during the experiment. Another example could be
the screw that wasn’t screwed perfectly so there were a little bit gap between the pipe that
may affect the calculation in the final.
QUESTIONS
1. What are the relative merits of the ‘orifice plate’, ‘nozzles’ and the ‘Venturi tube’ for
measuring flowrates in a pipe?
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1 2 3 4 5 6 7 8 9 10
0
10
20
30
40
50
60
70
80
90
100
Setting 2 Setting 3 Setting 4
Setting 5 Setting 6 Series6
% valve opening diameter
Air flowrate (dm3.s-1)

The measurements mentioned above are used to measure flowrates of fluids. It helps us
find the characteristics of fluid flow for each tube or plates. For orifice plate, it is a
simple and cheap plate, and requires minimum amount of space in industry. Nozzle
plates it is also relatively cheap with huge frictional loss for fluid flows. And the last one,
venture tube is a frictionless tube that has the most accurate result, and has the biggest
size between the measurements mentioned above.
2. Calculate the volumetric flow rates of air for the nozzle and orifice plate (50mm
diameter each) if the pressure drop across both devices was 710 Nm-2. The α and β
values are 1.1377 and 0.937 for nozzle, and 0.7588 and 0.9705 for the orifice plate.
Known:
The diameter (d) = 50mm = 0.05m
α = 1.1377 and β = 0.937
ρ Is the density of air = 1.177 kg/m3
Volumetric flow rate (dm3.s-1) ¿ α . β . A √ 2 ∆ P
ρ
A=π r2
A nozzle=π ( 0.05
2 )
2
=1.963 ×10−3 m2
V.F.R nozzle ¿ 1.1377 ×0.937 × 1.963× 10−3 × √ 2 ×710
1.2 = 0.07200×103=¿ 72.00 dm3.s-1
A=π r2
A orifice plate=π ( 0.05
2 )
2
=1.963× 10−3 m2
V.F.R orifice plate ¿ 0.7588 ×0.9705 ×1.963 ×10−3 × √ 2 ×710
1.2 =¿ 0.0497 ×103=49.74
dm3.s-1
3. Why is a manometer with small internal diameter recommended for Pitot tube?
Manometers with smaller internal diameter recommended for Pitot tube to improve the
sensitivity of the Pitot tube and give more accurate reading hence more accurate
results.
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4. What does an anemometer measure?
Anemometer is an instrument that used to calculate and measure the speed and
gases velocity that contained in airflow no un airflows condition (Carpenter, 2017)
5. Why do the different pipe bends have different pressure drop?
Different pipe bends have different pressure drop because of the friction and or the
resistance of the fluid flow, therefore they have different potential energy losses.
Depending on the pipe bends diameter, the pipe itself would also affect the pressure
drop due to friction.
References
Carpenter, M. E. (2017, April 25). Differernt Types of Anemometer. Retrieved from Sciencing:
https://sciencing.com/different-types-anemometers-8526081.html
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