[SEGi University]
[Chemical Engineering Laboratory 2]
SEGi University EXPERIMENT EXPERIMENT 2: Friction Loss Along A Pipe Candidate’s Name: Ahmed Name: Ahmed Khalid GasmElseed Student ID: scm 031773 Group Member’s Name: Giethijwok Joshua Otor
scm 030290
Harjendar singh
scm 030698
Ronald Selvam
scm 024241
Sivaraj A/L Kunajegar
scm 024052
Oliver prasath A/L Richard scm 023448
Lecturer/ Supervisor: Dr.Chan Date of Submission: 06/11/2015
Abstract This experiment was conducted to verify the Darcy Weisbach equation by determining the
pressure loss along a horizontal pipe.
Also to differentiate between the types of fluid flows (laminar, transition and turbulent).
Introduction The frictional resistance to fluid as it flows along a pipeline results in continuous loss of energy or total head loss of the fluid. Friction loss is t he loss of energy or “head” that occurs in pipe flow due to viscous effects generated by the surface of the pipe. Friction Loss is considered as a "major loss" and it is not to be confused with “minor loss” which includes energy lost due to obstructions. In mechanical systems such as internal combustion engines, it refers to the power lost overcoming the friction between two moving surfaces. This energy drop is dependent on the wall shear stress (τ) between the fluid and pipe surface. The shear stress of a flow is also dependent on whether the flow is turbulent or laminar. For turbulent flow, the pressure drop is dependent on the roughness of the surface, while in laminar flow, the roughness effects of the wall are negligible. This is due to the fact that in turbulent flow, a thin viscous layer is formed near the pipe surface which causes a loss in energy, while in laminar flow, this viscous layer is non-existent. Figure 2.1 ill ustrates that the frictional loss along a horizontal pipe with length, , is equals to the difference in levels between piezometers A and B,h .
Figure 2.1: Diagram illustrating the frictional loss i n terms of pressure head.
The frictional loss (h f ) also can be determined by Darcy Weisbach equation: - h f is the head loss due to friction (SI units: m); - L is the length of the pipe (m); - D is the hydraulic diameter of the pipe (for a pipe of circular section, this equals the internal diameter of the pipe) (m); - V is the average velocity of the fluid flow, equal to the volumetric flow rate per unit cross-sectional wetted area (m/s); - g is the local acceleration due to gravity (m/s2 ); - f D is a dimensionless coefficient called the Darcy friction factor. It can be found from a Moody diagram or more precisely by solving the Modified Colebrook equation. Friction factor is affected by the type of flows; laminar transition and turbulent, as well as the relative roughness of the pipe. Figure 2.2 shows the motions of different type of flows by introducing a filament of dye into the flow of the water along a glass pipe. At low velocities, the filament appeared as a straight line, which passed down the whole length of the tube indicating laminar flow. At intermediate velocities, transitional flow is observed where the filament is found to be fluctuated in the water. At higher velocities, the filament mixed with the surrounding water randomly after passing a little way along the pipe. The motion has now becomes turbulent. This flow is laminar, transitional or turbulent is depends on the value of the Reynolds number, Re.
Figure 2.2: Experiment to illustrate laminar, transitional and turbulent flows
Experimental procedure 1- The inlet valve was adjusted to obtain a flow of water through the required test pipe. 2- Flow rates were measured using the volumetric tank in conjunction with flow control valve. 3- For small flow rates the measuring cylinder was used in conjunction with flow control. 4- Head loss was measured between the tapping using the mercury manometer or pressurized water manometer as appropriate. 5- The pressure head readings were obtained (at t he inlet, and outlet, ) on test section. 6- Steps 1 -5 were repeated to obtain at least three sets of data for laminar, transitional and turbulent flows.
Results
Volume (mL)
Time (s)
h 1
115
19.97
370
165
205
mmH2O
mmH2O
mmH2O
335
205
130
mmH2O
mmH2O
mmH2O
320
222
98
mmH2O
mmH2O
mmH2O
495
140
355
mmH2O
mmH2O
mmH2O
430
115
315
mmH2O
mmH2O
mmH2O
305
230
75
mmH2O
mmH2O
mmH2O
98
164
-66
mmHg
mmHg
mmHg
49
210
-161
mmHg
mmHg
mmHg
55
195
-140
mmHg
mmHg
mmHg
95
150
150
200
100
145
250
200
19.7
39
19.73
28.77
31.29
12.52
11
9.51
h 2
h 1 - h 2
Re
Type of flow
0.815
386.352
laminar
-6 4.822 x10
0.682
323.303
laminar
-6 3.846 x10
0.544
257.884
laminar
7.603 x10-6
1.075
509.605
laminar
-6 6.952 x10
0.983
465.993
laminar
-6 3.196 x10
0.452
214.271
laminar
1.158 x10-5
1.638
7051.21
turbulent
-5 2.273 x10
3.215
13839.82
turbulent
-5 2.103 x10
2.975
12806.68
turbulent
Q (m3/s)
(m/s)
-6 5.759x10
Table 1: Flow Rate and Pressure Head
V
400
350
300
250
200
150
100
50
0 0
0.5
1
1.5
2
Graph 1: h1-h2 versus V
205 130 98 75 315 355 66 140 161
0.815 0.682 0.544 0.452 0.983 1.075 1.638 2.975 3.215
2.5
3
3.5
3
2.5
2
1.5
1
0.5
0 -0.4
-0.3
-0.2
-0.1
0
0.1
0.2
Graph 2: logh1-h2 versus logV
0.3
0.4
0. 5
0.6
Calculation 1] f = 0.166
= 0.891m
2] f = 0.199
=0.748m
3] f = 0.248
= 0.593m
4] f = 0.126
= 1.176m
5] f = 0.137
= 1.069m
6] f = 0.299
= 0.493m
7] f = 0.034
= 0.737m
8] f = 0.028
= 2.338m
9] f = 0.029
= 2.073m
Discussion We noticed that the valueof h1-h2 become negative, that’s because of the equipment set up that was used, so we changed it into h2-h1. differences were noticed in the values of head loss in the experiment and in the calculation which is caused by errors and mistakes.
Conclusion In conclusion the Darcy Weisbach equation was approved to be an efficient way to calculate h f from what was calculated an measured. Also the errors in the experiment can be avoided by many ways such as registering the values of h1 and h2 the moment the machine starts because of the fluctuations of water and mercury in the pipes.
References [1]Introduction to Fluid Mechanics, 3rd Edition ,William S. Janna (1993) [2]Cemical Engineering II laboratory handbook [3] http://staff.fit.ac.cy/eng.fm/classes/amee202/Fluids%20Lab%20Friction%20losses.pdf (accesed on 3/11/2015)
