TRIBHUVAN UNIVERSITY
INSTITUTE OF ENGINEERING
THAPATHALI CAMPUS
Lab report on: Losses in pipes
Submitted By: Submitted To:
Name: Raju Pal Department of Civil
Roll No: THA077BCE100 Engineering
Date:2079/12/12 Thapathali Campus
TITLE: "LOSSES IN PIPES"
OBJECTIVES:
To demonstrate and estimate the energy loss(major and minor losses) for fluid flow through pipes
To determine the friction factor (f) and coefficient of energy loss in bend, pipe fittings
APPARATUS REQUIRED:
i. Pipe fittings
ii. Stop watch
iii. Measuring cylinder.
THEORY:
Bernoulli's principle is one of the fundamental principles of fluid flow. Its equation establishes a relationship
between pressure, elevation, weight and velocity of moving fluid. Bernoulli's principle states that "In a steady,
irrotational flow of an incompressible and non-viscous fluid, the total energy at any point remains same."
𝑃 𝑣2
i.e. + 2𝑔 + 𝑧 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 = 𝑇𝑜𝑡𝑎𝑙 ℎ𝑒𝑎𝑑(𝐻)
𝛾
This equation is called Bernoulli's equation.
For any two sections 1 and 2,
𝑃1 𝑣 2 1 𝑃2 𝑣 2 2
+ + 𝑧1 = + + 𝑧2
𝛾 2𝑔 𝛾 2𝑔
But for real flow of fluids through pipes and conduits, there is always some head loss induced and the
Bernoulli's equation is given as:
𝑃1 𝑣 2 1 𝑃2 𝑣 2 2
+ + 𝑧1 = + + 𝑧2 + 𝐸𝑓
𝛾 2𝑔 𝛾 2𝑔
Where, Ef = energy requirement (major and minor losses)(J/kg)
P1, P2 = pressure at two different sections
v1, v2 = average flow velocity at two different sections
g = gravitational acceleration
z1, z2 = flow heads in m
There are two types of energy losses as classified below:
i. Major losses:
These losses are due to wall shear in pipe elements, also called friction losses. And the value of
friction loss (hf) for any circular section in pipe flow is given by Darcy-Weisbach equation as:
𝑓𝐿𝑣 2
ℎ𝑓 =
2𝑔𝑑
8𝑓𝐿𝑄2
ℎ𝑓 =
𝑔𝜋 2 𝑑 5
i.e.
𝑔𝜋 2 𝑑 5
𝑓= ∗ ℎ𝑓
8𝐿𝑄2
Where, f= friction factor
L= length of the section of pipe
v= velocity of flow
d= diameter of pipe
ii. Minor losses:
Pipe systems also consist of valves, elbows, wnlargements of pieps, contraction of pipes, inlets,
outlets, bends and other fittings that cause additional losses, referred to as minor losses. These
minor losses and their related relations are presented below:
(𝑣1 −𝑣2 )2
a. Sudden enlargements: ℎ𝑒 = 2𝑔
0.5∗𝑣2 2
b. Sudden contractions: ℎ𝑐 = 2𝑔
0.5∗𝑣 2
c. Entrance loss: ℎ𝑖 = 2𝑔
𝑣2
d. Exit loss: ℎ𝑜 = 2𝑔
𝑘𝑣 2
e. Bend loss: ℎ𝑏 = 2𝑔
𝑘𝑣 2
f. Pipe fitting: ℎ𝑝 = 2𝑔
PROCEDURE:
1. The apparatus was set and the pump was started.
2. The pipes were selected and by operating appropriate valves, flow was allowed to pass through the
system.
3. The pressure tapping’s were connected at the pipe to the manifold by operating small cocks so that the
manometer comes in contact with water in pipe.
4. Then using the cocks, in the manometer and the air vent, the water level was brought to some
appropriate level in the manometer and the air vent was closed.
5. Operating the drain cocks, in the manometer and the air vent, water level was brought to a level, and
the pressure tapping’s were disconnected right after.
6. The flow was regulated and a small discharge was allowed to pass through the pipe.
7. Then the manifold cock was opened so that the manometer liquid would stand at two different heights.
8. The pressure difference for the corresponding height difference was noted and discharge was recorded.
9. The process was repeated for few observations.
OBSERVATION:
Table 1:
Pipe Length (cm) Diameter (cm) Materials
1-2 200 1.25
2-3 1.25
3-4 18 1.25
4-5 1.25 GI Pipe
5-6 62.7 1.25
6-7 1.25-2.5
7-8 84 2.5
8-9 2.5—2.5
Table 2:
S.N. Manometer reading (cm) Volume time Discharge Mean
1 2 3 4 5 6 7 8 9 (ml) Q= v/t (m3/sec)
1. 54.5 27.3 33.2 48 42.2 28.5 24.6 23.3 10 710 4.155 1.7×10-4
680 3.625 1.9×10-4 1.7×10-4
850 5.28 1.6×10-4
2. 68.7 36.9 42 56.5 49.5 33.5 29.5 28.2 12.5 890 5.155 1.7×10-4
660 3.725 1.8×10-4 1.8×10-4
700 3.765 1.9×10-4
COMPUTATION:
From 1st Observation:
1-2
Friction loss
2𝑔𝑑
f1-2 = × ℎf
𝑙𝑣 2
2×9.81×0.0125×(54.5−27.3)
= 2 =0.0173
1.7×10−4
2×( )×100
𝜋×0.01252
4
2gd
f3-4 = × hf
l𝑣 2
2×9.81×0.0125×(33.2−12.5−(48−30.5))
= 1.7×10−4 2
=0.02272
0.18×( ) ×100
𝜋×0.01252
4
2gd
f5-6 = × hf
l𝑣 2
2×9.81×0.0125×(42.2−28.5)
= 1.7×10−4 2
=0.02792
0.627×( ) ×100
𝜋×0.01252
4
2gd
f7-8 = × hf
l𝑣 2
2×9.81×0.025×(24.6−23.3)
= 1.7×10−4 2
=0.06329
0.84×( ) ×100
𝜋×0.0252
4
Bend loss
1-3
𝑘𝑣 2
ℎ𝑏 =
2𝑔
2𝑔ℎ𝑏
𝑘=
𝑣2
(27.3−33.2+12.5)
2×9.81×
100
= 1.7×10−4 2
( )
𝜋×0.01252
4
= 0.6747
4-5
2𝑔ℎ𝑏
𝑘=
𝑣2
(48−30.5−42.2+33)
2×9.81×
100
= 1.7×10−4 2
( )
𝜋×0.01252
4
= 0.8485
Expansion Loss
6-7
(𝑣1 − 𝑣2 )2
ℎ𝑒 =
2𝑔
𝜋 𝜋
(1.7 × 10−4 )2 × ( 2 − 4 × 72 )
2
4 × 𝑑6
=
2𝑔
= 0.0209
Contraction Loss
8-9
0.5 ∗ 𝑣2 2
ℎ𝑐 =
2𝑔
𝑄
(𝐴 )2
9
= 0.5
2𝑔
= 0.04890
RESULT: From I Observation And Calculation
S.N. Pipe Head Loss(cm) Coefficient Remarks
1. 1-2 54.5-27.3=27.2 0.0173 Friction loss
2. 2-3 27.3-(33.2-12.5)=6.6 0.6747 Bend loss
3. 3-4 (33.2-12.5)-(48-30.5)=13.2 0.02272 Friction loss
4. 4-5 (48-30.5)-(42.2-33)=8.3 0.8485 Bend loss
5. 5-6 (42.2-33)-(38.5-33)=13.7 0.02792 Friction loss
6. 6-7 28.5-24.6=3.9 0.0209 Expansion loss
7. 7-8 24.6-23.3=1.3 0.06329 Friction loss
8. 8-9 23.3-10=13.3 0.04890 Contraction loss
From II Observation And Calculation
S.N. Pipe Head Loss(cm) Coefficient Remarks
1. 1-2 68.7-36.9=31.8 0.0181 Friction loss
2. 2-3 36.9-(42-12.5)=6.6 0.6748 Bend loss
3. 3-4 42-56.5+18=3.5 0.0221 Friction loss
4. 4-5 56.5-49.5+2.5=9.5 0.8663 Bend loss
5. 5-6 49.5-33.5=16 0.02908 Friction loss
6. 6-7 33.5-29.5=4 0.0234
7. 7-8 29.5-28.2=1.3 0.05645 Friction loss
8. 8-9 28.2-12.5=15.7 0.05482
From I Observation
0.0173+0.02272+0.02792+0.06329
Friction factor(f)= 4
=0.03280
From II Observation
0.018`+0.0221+0.0290+0.5645
Friction factor(f)= 4
=0.03086
CONCLUSION:
Hence, in this way we can find the friction factor along with other coefficients of minor losses by using the
required pipe fitting.
