Lab Report 2.docx
Course Code: MME 2132 Course Name: Manufacturing Engineering Lab II Experiment: Friction Loss Name: Yazan Mustafa Wajeh
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Course Code: MME 2132 Course Name: Manufacturing Engineering Lab II Experiment: Friction Loss Name: Yazan Mustafa Wajeh Matric Number: 1223495 Date of Experiment: 19/11/2015 Date of Submission: 3/12/2015
Objectives 1- To know how to use and refine Bernoulli’s equation by introducing the frictional head loss, hf, and analyze the equation’s restrictions. 2- To analyze pressure loss due to friction, elbows, bends, and fittings. 3- To estimate friction losses using the energy equation. 4- To understand head loss. 5- To compare the calculated friction factor to the estimated friction factor from Moody’s diagram.
Equipment 1- Cussons Hydraulic Bench.
Introduction To start off, there are three types of fluid flow: laminar, turbulent, and transitional. Laminar flow (or streamline flow) occurs when a fluid flows in layers parallel to the walls of the pipe where the layers slide past one another without mixing laterally. This typically occurs at low velocities. Turbulent flow, on the other hand, is when the fluid flows in an erratic motion with swirls and irregular motions in a manner that is more likely to resemble the mixing of the fluid. In between the laminar and turbulent flow is the transitional flow which from its name, shows that it is similar to a “transitional” phase between the laminar and the turbulent flow. In other words, it is a mix of both flows. The flows are clarified in following drawing as laminar flow, transitional flow, and turbulent flow, respectively. In this experiment, we will try to prove/disprove Bernoulli’s equation that states that energy should be
equal to a constant at any point in a channel. It is of due importance to note that three types of energy can be observed: potential energy (which is due to difference in height), kinetic energy (which is due to the motion of the fluid), and flow energy (which is due to the pressure of the flow). Using the energy equation and some assumptions, we can achieve Bernoulli’s equation as will be proved later in this report.
Method and Procedure Straight pipes (7 mm and 10 mm diameters), Bent pipe (10 mm diameter, and Elbow pipe (10 mm diameter) 1. The pipe was placed securely in its position and the two tubes of the manometer were connected to the pipe. 2. The pump was started and the water level was adjusted using the bench regulation valve. 3. The swivel arm of the outlet tank was set to be vertical. 4. A series flow condition was set. 5. At each variable outlet volume, the time, volumetric flow rate, inlet head, outlet head, and the difference between the two heads were observed and recorded accordingly. 6. Steps 1 to 5 were repeated for the different pipes.
Results and Observations Straight pipe (10 mm diameter) f = 2gDhf/LV Re = D x V/v v = 8.85 x 10-4 / 103 V = Q/A Q = (L/1000) / seconds A = (3.14/4) x D2
Variable outlet volume Volume
35
30
25
20
15
5
5
5
5
5
(L) Time (s) Volumetri c flow rate (L/s) Inlet head (h1) Outlet head (h2) h1-h2
60 1/12
48 5/48
43 5/43
40 1/8
35 1/7
230
214
205
192
185
298
214
205
192
185
-68
-28
9
48
89
#
Volumet ric flow rate Q (m3/s)
1 2 3 4 5
8.30x10-5 1.04x10-4 1.16x10-4 1.25x10-4 1.43x10-4
Avera ge veloci ty V (m/s) 1.06 1.32 1.48 1.59 1.82
Re (dimension less)
11977 14915 16384 17966 20565
Fracti on head loss hf (m) 0.068 0.028 0.009 0.048 0.089
Friction factor f (dimension less)
Log (hf/L )
Log(V )
0.025 0.008 0.002 0.012 0.019
-0.72 -1.11 -1.60 -0.88 -0.61
0.025 0.12 0.17 0.20 0.26
Log(hf/L) vs Log(V) 0 -0.2 0
0.05
0.1
0.15
0.2
0.25
0.3
-0.4 -0.6 -0.8 -1 -1.2 -1.4 -1.6 -1.8
Log(hf/L) vs Log(V)
Straight pipe (7 mm diameter) f = 2gDhf/LV Re = D x V/v v = 8.85 x 10-4 / 103 V = Q/A Q = (L/1000) / seconds A = (3.14/4) x D2 Variable outlet volume Volume (L)
35
30
25
20
15
5
5
5
5
5
Time (s) Volumetri c flow rate (L/s) Inlet head (h1) Outlet head (h2) h1-h2
146 5/146
121 5/121
105 5/105
99 5/99
90 5/90
395
375
355
335
315
215
202
192
184
179
180
173
163
151
136
#
Volumet ric flow rate Q (m3/s)
1 2 3 4 5
3.42x10-5 4.13x10-5 4.76x10-5 5.05x10-5 5.56x10-5
Avera ge veloci ty V (m/s) 0.89 1.07 1.24 1.31 1.44
Re (dimension less)
7040 8463 9808 10362 11390
Fracti on head loss hf (m) 0.180 0.173 0.163 0.151 0.136
Friction factor f (dimension less)
Log (hf/L )
Log(V )
0.077 0.062 0.050 0.044 0.036
-0.30 -0.32 -0.34 -0.38 -0.42
-0.051 0.029 0.093 0.117 0.158
Log(hf/L) vs Log(V) 0 -0.1
-0.05
-0.05
0
0.05
0.1
0.15
0.2
-0.1 -0.15 -0.2 -0.25 -0.3 -0.35 -0.4 -0.45
Log(hf/L) vs Log(V)
Bent pipe (10 mm diameter) Variable outlet volume Volume (L) Time (s) Volumetri c flow rate (L/s) Inlet head (h1) Outlet head (h2) h1-h2
35
30
25
20
15
5
5
5
5
5
68 5/66
57 5/57
52 5/52
46 5/46
43 5/43
380
360
335
310
290
296
246
190
139
84
84
114
145
171
206
Elbow pipe (10 mm diameter) Variable outlet volume Volume (L) Time (s) Volumetri c flow rate (L/s) Inlet head (h1) Outlet head (h2) h1-h2
35
30
25
20
15
5
5
5
5
5
118 5/118
98 5/98
87 5/87
79 5/79
72 5/72
428
420
412
404
396
300
252
200
150
96
128
168
212
254
300
V = Q/A Q = (L/1000) / seconds A = (3.14/4) x D2 f = 2gDhf / V2 (L+N(30D)) h f = h1 – h 2 hL = LV2f / 2gD hB = hf – hL / N
KB = hB / (V2 / 2g)
Bent pipe (10 mm diameter) #
Volumet ric flow rate Q (m3/s)
1 2 3 4 5
7.35x10-5 8.77x10-5 9.62x10-5 1.09x10-4 1.16x10-4
Averag e velocit yV (m/s) 0.94 1.12 1.22 1.39 1.48
f
Fractio n head loss hf (m)
hL
hB
KB
0.024 0.023 0.025 0.023 0.024
0.084 0.114 0.145 0.171 0.206
0.050 0.068 0.088 0.105 0.124
1.68 0.046 0.057 0.066 0.082
0.390 0.007 0.008 0.007 0.008
Elbow pipe (10 mm diameter) #
Volumet ric flow rate Q (m3/s)
1 2 3 4 5
4.24x10-7 5.10x10-5 5.75x10-5 6.33x10-5 6.94x10-5
Averag e velocit yV (m/s) 0.525 0.649 0.732 0.806 0.884
f
Fractio n head loss hf (m)
hL
hB
KB
0.160 0.158 0.157 0.155 0.152
0.128 0.168 0.212 0.254 0.300
0.040 0.159 0.269 0.390 0.554
0.088 0.009 -0.057 -0.136 -0.254
0.065 0.004 -0.022 -0.043 -0.066
Discussion Starting by comparing the first two pipes (straight 10 mm diameter and straight 7 mm diameter), one can see that in both pipes, there is a general pattern of decreasing friction and increasing velocity, thus, increasing volumetric rate. We had turbulent flow in both pipes since the beginning because reynold’s number > 4000. Since the smaller pipe allows less fluid to flow at a time, it is clear from the results that reynold’s number is smaller
which is logical since the fluid has less room for irregular flows. Comparing the times of both pipes, it can be easily perceived that the pipe with 10 mm diameter requires less time, obviously, than the pipe with 7 mm diameter. Comparing the elbow and the bent pipes (both with 10 mm diameter), one can see that the bent pipe required less time in general than the elbow and this can be easily inferred by looking at the fraction head loss and friction factor which are both less in the bent pipe than the elbow pipe, hence, the velocity was also bigger in the bent pipe. Due to the bent pipe having a smoother inner conduit than that of the elbow, it can be seen that the head loss is less there. Now, comparing the 3 pipes with 10 mm diameter, it is clear that the straight pipe has the highest velocity of flow and the bends become sharper, the velocity decreases sharply. In both cases of the bent pipe and the elbow pipe, KB constant keeps decreasing and this is due to both hB and the velocity having a general decreasing trend.
Conclusion In this experiment, we came to observe and understand the three different types of flow – namely laminar,
transitional, and turbulent. Also, we observed how different pipes diameters and contours affect the velocity, pressure drop, friction, and volumetric rate. We also managed to derive Bernoulli’s equation from the energy equation and prove that Bernoulli’s statement about energy being constant at any point in the length of channel is correct.
Recommendation 1- Ensure the pipes are securely tightened so no leakage will take place and give wrong readings. 2- Ensure you turn off the machine before each pipe change. 3- Ensure the manometer is bubble-free to avoid getting wrong readings.
References 1. Lab Manual 2. Heat Transfer (Hallman) 3. efm.leeds.ac.uk 4. hyperphysics.phy-astr.gsu.edu 5.engineeringtoolbox.com