CDB 2052

CHEMICAL ENGINEERING LABORATORY 1

Sept 2015

Experiment : 5- Flow in Pipes and Fittings

Group : 13

Group Members : Mohd Hafiz bin Mohd Nor 19992

Nurfatien binti Bacho 20005

Tracy Chua Peng Ling 20443

Vegenes A/L Venkatasal Rao 19867

Lab Instructor : Muhammad Shuaib

Date of Experiment : 8th October 2015

Abstract

Flow in Pipe and Fittings experiment is conducted to help the students to study the fluid flow in different types of pipes. Understanding of fluid flow is important for engineering students as in most manufacturing industries, large flow networks are necessary to achieve continuous transportation of raw materials and products from one processing unit to another.

In this experiment, students will be able to study the flow of water different types of pipes and fittings. The few main variables in this experiment include the type of pipes used, the diameter of the pipes, different flow rate of water, pressure difference, velocity, Reynold’s number, friction factor, and friction loss.

There are two parts in Experiment 5 which are part A and Part D. In part A, the main objective of the experiment conducted is to the effect of the volumetric flow rate on the friction factor, pressure drop and Reynolds’s number, the effect of pressure drop on friction loss with different surface roughness and diameters of the pipe. In part A, pipe 1, pipe 2 and pipe 3 are used to conduct the experiment. Pipe 1 and pipe 2 are smooth-surfaced pipes of different inner diameters, which is 6mm for pipe 1 and 10 mm for pipe 2. Pipe 3 is an artificially roughened pipe with the inner diameter of 17mm. Water is passed through the three pipes with different flow rates. 3 readings of pressure change are taken for every flow rate in each pipe. The relationship between the pressure drop and friction loss for flow of water through pipes of different diameter and surface roughness is studied via the principle of Bernoulli’s equation. The assumption made for part A is as the inner diameter of the pipe decreases, the friction factor decreases, thus friction loss is increased. In the case of the smoothness of the pipe surface, it can be assumed that smooth pipe surface will have a lower friction factor compared to a rough pipe surface.

For part D of experiment 5, the main objective is to compare the precision of flow rate measurement using various flow rate measurement devices. In part D, pipe 16, pipe 17 and pipe 18 is used. Pipe 16 is a pitot static tube, pipe 17 is known as the Venturi meter while pipe 18 is an Orifice meter. In this part of the experiment, the pressure loss of a range of different flow rates of water is recorded each for pitot tube, venture and orifice. From the graph, as the volumetric flowrate increases, the pressure drop also increases. It is assumed that, as the flow rate becomes greater, the pressure drop of the venturi meter becomes higher compared to the flow rate of the orifice and pitot tube. Thus, venturi meter is the most accurate measuring instrument as compared to orifice and pitot static tube. From this experiment, it is necessary to relate between the volumetric flow rate and sudden head loss from these devices in order to measure its accuracy.

Results and Discussion

Experiment A : To study the friction loss in variation of pipe

5 10 15 20 25 30 35 40 450

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

Pipe 1 Pipe 2 Pipe 3

Water flowrate (L/min)

∆P (P

a)

Figure 1: Differential pressure vs Flowrate of water in pipes

From the figure above, as the water flowrate increase, the differential pressure for each pipe also gradually increases. Pipe 1 has higher pressure drop than pipe 2 due to the smaller diameter. Pipe 3 is the artificially roughened surface which should be considered since the other pipes have the smooth surface. Thus, pipe 3 should has the highest pressure drop among the three pipes if all of them have the same diameter. However, due to its its large diameter, the pressure drop is low.

Figure 2: Friction factor vs Flowrate of water in pipes

From figure above, the value of the friction factor decreases with the increasing value of flowrate. The value of friction factor depends on the diameter of the pipe and surface roughness of the pipe. As the diameter of pipe increase, friction factor increases because the fluid gets more contact with the inner surface of the pipe creating more friction between them. This friction factor has a relation with pressure drop of the pipe. As the value of friction factor decreases, the value of pressure drop will also increases. Pipe 1 has the highest pressure drop since it is a smooth pipe and has the smallest diameter between all pipes. While pipe 3 has the lowest pressure drop because it has the biggest diameter among all three pipe and it is an artificially roughened pipe. Therefore, the smaller the diameter of the pipe and the smoother the pipe, the higher the friction factor, the bigger the value of the pressure drop.

Figure 3: Friction Loss, F vs Flowrate of water in pipes

As we can see from the figure, as the water flowrate increases, the friction loss also increases. This is proven from the relation stated in the formula below

F=( 4 fLD

)(V2

2)❑

Pipe 1 has the highest friction loss since it has the highest pressure drop (due to its nature of small diameter ansd smooth pipe). While Pipe 3 has the lowest pressure drop and friction loss because of its biggest diameter and roughened pipe. Thus, smaller diameter pipe will lead to bigger pressure drop and higher friction loss.

Figure 4: Reynolds Number vs Flowrate of water in pipes

The graph above show a relation between Reynolds number and water flowrate which is directly proportional to each other. The higher the water flow rate, the higher is the Reynolds number. Pipe 3 has the highest Reynolds number. Theoretically, Reynolds number decreases as the diameter of the pipe increases. This is because velocity is inversely proportional to the diameter of pipes.

Thus, we have some errors in our experiment as the theoretical result should be a decreasing Reynolds number from pipe 1, 2 and 3. So the line of pipe 1 should lie between pipe 2 and 3. Bubbles might still exist in the pipe and that brought to some errors. Waiting longer for the water to flow in the pipe might produce better result. For pipe 3, it is artificially made to be rough. In pipes, the rougher it is, the thicker the layer of non-moving or slow moving liquid near the pipe wall. This reduces the inside diameter of the pipe, increasing the velocity of the liquid. With the increase in velocity comes an increase in Reynolds number. That is why pipe 3 has the highest Reynolds Number if compared to pipe 1 and 2. This relation proves that not only flow rates and diameters are important in pipes, but the pipes’ inner roughness, also influence Reynolds number significantly.

Figure 5: Head Loss vs Flowrate of water in pipes

From the graph, as the water flowrate increases, the head loss also increases. An energy or pressure difference must exist to cause the liquid to move. A portion of that energy is lost to the resistance to flow. This resistance to flow is called head loss due to friction. The rougher the pipe, the thicker the layer of non-moving or the slow moving liquid near the pipe wall. This will reduces the inner diameter of the pipe and therefore increasing the velocity of the liquid. Subsequently, the value of head loss will also increases. Hence, the bigger the pipe, the lower the pressure drop, and the lower is the head loss.

Figure 6: h measured vs h actual in pipes

As water flow rate increases, the percentage difference between head loss measured and head loss calculated also increases. However, this does not apply to pipe 1. For the smooth pipe, the bigger the the diameter of the pipe, the bigger the percentage difference as the water flowrate increases.

Calculated friction head loss is obtained through equation of friction loss as shown in the appendices.Whereas the measured friction loss, is obtained when we conducted the experiment, the data that is read from the “Main Switch Board”. Values of the measured head loss should be approximately the same as the calculated friction head loss. However, due to some errors in the experiment such as the presence of bubbles in the pipe, values of measured head losses deviate from the calculated values. What can be seen for the smooth pipes is that the bigger the diameter of the pipe, the bigger the percentage difference for a constant value of water flow rate. The lower the Reynolds number in the pipe, the higher is the percentage difference. Thus, in real applications, theoretical values can only be used for the small diameter pipes, or pipes with high Reynolds number. The rough pipe 3 is having the highest percentage difference. This is because the non-constant inner surface of the pipe cannot be calculated perfectly accurate and precise. The equations given are only based on assumptions because roughness itself cannot be measured.

Experiment D: To compare the precision of flow rate measurement using various flow rate measurement devices that which are orifice, venture meter and pitot static tube.

5 10 15 20 25 30 35 400

0.2

0.4

0.6

0.8

1

1.2

OrifacePitotVenturi

Volumetric Flowrate, L/min

Pres

sure

Dor

p, m

H2O

Figure 7: Pressure Difference vs Flowrate of water in venture orifice and pitot static tube

From the graph, as the volumetric flowrate increases, the pressure drop also increases. The slope of the pitot tube is lesser than the slope of orifice meter. The highest slope is for venturi following by orifice and then pitot static tube. It is clearly illustrated by the above graph. As the flow rate becomes greater, the pressure drop of the venturi meter becomes higher compared to the flow rate of the orifice and pitot tube.

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Pitot Orifice

Actual Head Loss (h actual), m

Mea

sure

d He

ad Lo

ss (h

mea

sure

d),m

Figure 8: h measured vs h actual in orifice and pitot static tube

0 0.2 0.4 0.6 0.8 1 1.20

0.2

0.4

0.6

0.8

1

1.2

Oriface Venturi

Actual Head Loss (h actual), m

Mea

sure

d He

ad Lo

ss (h

mea

sure

d),m

Figure 9: h measured vs h actual in orifice and venturi

The objective of this experiment is to compare the precision of flow rate measurement using various flow rate measurement devices. In order to compare, we need the value of h measured and hcalculated. The lesser the percentage error, the more precise the measurement device. Thus, the graph of measured head loss vs actual head loss will be compared if it is directly proportional or not.

The measured head loss vs actual head loss graph had to be done separately for venturi and pitot since the value in pitot is relatively very small.

Based on the graph, it shows that measured friction head loss is linearly proportional to calculated friction head loss. By theory, the relation that we suppose to get is directly proportional. This is because values of measured friction head loss should be approximately same with calculated friction head loss. However, due to some error present during the experiment such as presence of bubbles in the pipe, there is difference between measured friction head loss and calculated friction head loss.

For the Graph Qset vs. Qcalc, this graph gives us the relation among of Qset and Qcalc, where Qset is equivalent to Qcalc. As Qcalc decreases, Qset also decreases. From the Graph Hset vs Hcalc, as Hset increases, Hcalc increases. But when Hcalc decreases to a certain value, Hset increases.

For the orifice meter and venturi meter, the flow rate and differential head are related by the Bernoulli equation with a correction coefficient for energy degradation.

Calculations :

Q=C D A0[1−( A0A1 )2]

−12

√2 g(h1−h2)

Where Q = Flow rate m3

sCD= Discharge coefficient

Cd= 0.97 for venturi meter

Cd= 0.62 for orifice meter

A0= Area of the throat

d0= 16mm for the venturi meter (A0=2.011×10−4m2)

d0= 20mm for the orifice meter (A0=3.143×10−4m2)

A1=¿ Area of the pipe upstream m2

d1= 26mm for the venturi meter (A1=5.311×10−4m2)

d1= 24mm for the orifice meter (A1=4.526×10−4m2)

h1−h2 = Differential head, m H 2O

g = 9.81 (acceleration due to gravity, m/s2)

Errors and recommendation

1. Bubbles are formed in the pipe as the water flows. To avoid such scenario, the water should be continuously flowed into the pipe for about 2-5minutes.

2. Inaccuracy of the flowrate throughout the experiment. Make sure the pipes are connected properly and not leaking out to get accurate value of flow rate and head loss.

3. Water-hammering can cause serious damage towards the fittings in the pipeline and also inaccuracy readings. Make sure that the V1 is opened slowly and not open it abruptly in order to void this phenomenon happen in the system.

4. There is high fluctuation in the experiment. Thus, the experiment was repeated to get 3 reading at 2 minute intervals so that we can get an average reading.

Conclusion

In experiment 5, part A of the experiment aims to study the friction loss in different pipes which differ in terms of surface roughness and diameter but with constant length. By the end of this experiment, the friction head loss in different pipe diameter and different roughness is determined. The results of part A showed that with different diameter, the larger the diameters of the pipe, the higher the friction factor but friction loss is reduced. Pipe with different surface roughness effects the friction factor of the fluid. It can be seen that pipe 3 has the highest friction factor compared to other pipes as it has the roughest surface. This experiment proves that Mechanical Energy’s Equation is an effective way to calculate friction loss of flowing water in small pipes.

For Experiment D, we were able to compare the accuracy of flow rate measurement using various flow rate measurement devices. In this experiment, the pressure loss of three types of measuring devices, pitot static tube, venturi and orifice is recorded using different ranges of flow rate. The results shows that most venturi meter tend to promote laminar flow due to the slower transitions from one part of the venturi than the other when compared to an orifice, while orifice meter and pitot static tube tends to have sharper transitions resulting in turbulent flow. From the graph, as the volumetric flowrate increases, the pressure drop also increases. The slope of the pitot tube is lesser than the slope of orifice meter. The highest slope is for venturi following by orifice and then pitot static tube. As the flow rate becomes greater, the pressure drop of the venturi meter becomes higher compared to the flow rate of the orifice and pitot tube.Therefore it can be seen that venturi meter is a more accurate measuring device as compared to orifice meter and pitot static tube.

In conclusion, as the fluid flow through the pipe, there will be pressure lost which is called friction loss due to the flow nature in pipes. We can identify from the experiment that Reynolds number and the friction factor of the pipes allows us to determine the friction loss of the pipe. Therefore, the objectives had been achieved. Any inaccurate or errors occurred in the recording and calculation of the data are due to the faultiness of the measuring equipment and due the effect from the environment.

References

Equations of Motion and Mechanical Energy (n.d.). Losses Due to Sudden Enlargement. Retrieved October 7, 2014, from http://nptel.ac.in/courses/Webcourse-contents/IIT-KANPUR/FLUID-MECHANICS/lecture-14/14-6_losses_sudden_enlarg.htm

Fluid Flow & Transport Processes (n.d.). CHAPTER 4 Incompressible Fluid Flow. Retrieved October 7, 2014, from http://elearnstag.utp.edu.my/0913/mod/resource/view.php?id=2763

MathWorks (n.d.). Sudden Area Change. Retrieved October 7, 2014, from http://www.mathworks.com/help/physmod/hydro/ref/suddenareachange.html

Nevers, N. D. (2005). Fluid Mechanics for Chemical Engineers. McGraw-Hill.

Plant and Environmental Hydrology Centre (n.d.). Correction factor for friction loss down a pipe with outlets. Retrieved October 7, 2014, from http://hydrology1.nmsu.edu/teaching/soil456/Friction.htm

Thermo Fluid Lab (n.d.). Pipe friction loss in a smooth pipe. Retrieved October 7, 2014, from http://faculty.uoh.edu.sa/m.mousa/Courses/ThermoLab%20ME%20316/ME%20316_2nd_semester%2012-13/ME316-2nd-12-13-%20Exps/Exp6-Pipe%20friction%20loss.pdf

Appendix

Experiment A

Pipe 1 (Smooth pipe)

Inner Diameter: 6 mm

Length: 1mArea: 0.0000283 m2

Flowrate (L/min)Pressure Difference (mH2O)2nd minute (s) 4th minute (s) 6th minute (s) Average

17.5 8.945 8.959 8.949 8.95115.0 6.822 6.814 6.813 6.81612.5 4.933 4.921 4.916 4.92310.0 3.384 3.390 3.377 3.3847.5 2.139 2.115 2.090 2.115

Pipe 2 (Smooth pipe)

Inner Diameter: 10 mm

Length: 1mArea: 0.0000785 m2

Flowrate (L/min)Pressure Difference (mH2O)

2nd minute (s) 4th minute (s) 6th minute (s) Average

39.5 6.857 6.859 6.845 6.85434.5 5.375 5.367 5.359 5.36729.5 4.026 4.048 4.056 4.04324.5 2.918 2.898 2.885 2.90019.5 1.957 1.945 1.939 1.947

Pipe 3 (Artificially roughened pipe)

Inner Diameter: 17 mm

Length: 1mArea: 0.000227 m2

Flowrate (L/min)Pressure Difference (mH2O)2nd minute (s) 4th minute (s) 6th minute (s) Average

35 9.024 9.038 9.015 9.02630 6.583 6.552 6.541 6.55925 4.589 4.574 4.566 4.57720 2.914 2.904 2.882 2.9

15 1.677 1.66 1.664 1.667Pipe 1 (Smooth pipe)

Water flowrate (L/min)

Pipe 1Differential pressure∆P (Pa)

Head Loss, hmeasured

(m)

Velocity, V (m/s)

Reynolds number, Re

Type of flow

Friction Factor, f

Friction Loss, F (m2 /s2 )

Head Loss, hcalculated

(m)

Percentage difference(%)

17.5 87779.32 8.9479 7.2874 43724.4 Turbulent 0.005303 93.8741 9.5692 6.9415.0 66842.13 6.8137 6.3592 38155.2 Turbulent 0.005450 73.4650 7.4888 9.9112.5 48278.14 4.9213 5.4045 32427.0 Turbulent 0.005630 54.8148 5.5876 13.5410.5 33185.70 3.3828 4.4807 26884.2 Turbulent 0.005844 39.1094 3.9867 17.857.5 20741.06 2.1143 3.5424 21254.4 Turbulent 0.006126 25.6242 2.6120 23.54

Pipe 2 (Smooth pipe)

Water flowrate (L/min)

Pipe 2Differential pressure∆P (Pa)

Head Loss, hmeasured

(m)

Velocity, V (m/s)

Reynolds number, Re

Type of flow

Friction Factor, f

Friction Loss, F (m2 /s2 )

Head Loss, hcalculated

(m)

Percentage difference(%)

39.5 67214.78 6.8517 6.3769 63769 Turbulent 0.004917 39.9898 4.0764 40.5134.5 52632.29 5.3652 5.6429 56429 Turbulent 0.005039 32.0907 3.2712 39.0329.5 39648.29 4.0416 4.8977 48977 Turbulent 0.005183 24.8654 2.5347 37.2824.5 28439.29 2.8990 4.1480 41480 Turbulent 0.005359 18.4413 1.8798 35.1619.5 19093.55 1.9463 3.3987 33987 Turbulent 0.005577 12.8842 1.3134 32.52

Pipe 3 (Artificially roughened pipe)

Water flowrate (L/min)

Pipe 3Differential pressure∆P (Pa)

Head Loss, hmeasured

(m)

Velocity, V (m/s)

Reynolds number, Re

Type of flow

Friction Factor, f

Friction Loss, F (m2 /s2 )

Head Loss, hcalculated

(m)

Percentage difference(%)

35 88514.82 9.0229 7.3179 124404.3 Turbulent 0.004302 33.4099 3.4057 62.2530 64321.82 6.5568 6.2382 106049.4 Turbulent 0.004442 24.2785 2.4749 62.2525 44885.04 4.5754 5.2111 88588.7 Turbulent 0.004604 16.9419 1.727 62.2520 28439.29 2.899 4.148 70516 Turbulent 0.004819 10.7345 1.0942 62.1315 16347.69 1.6664 3.1449 53463.3 Turbulent 0.005094 6.1704 0.629 62.25

1. Convert the differential pressure from mH20 to Pa

Differential pressure (Pa )=8.951mH 2

O∗9806.65N /m2

mH 2O = 87779.32 Pa

2. Calculate the head loss, hmeasured is calculated through the formula: 𝛥ℎ = 𝛥𝑃 𝜌𝑔 , where density = 1000kg/m3 ; g=9.81m/s2

Δh= ΔPρg

¿ 87779.32 Pa

(1000kg

m3 )(9.81m

s2) = 8.9479 m

3. calculate the velocity in the pipev=k √2gΔh where k is a constant at k=0.55V

v=0.55V √2 (9.81 ) (8.9479m )v=¿7.2874 m/s

4. Calculate the Reynold Number, Re

ℜ= ρvdμ

ℜ=1000

kg

m3×7.2874m

s×0.006m

(1×10−3 kgms )

ℜ=43724.4

Laminar flow occurs when Re< 2100 and turbulent flow occurs when Re > 4000; interval

between 2300 and 4000 are called transition flows

5. Calculating friction factorFor smooth pipe, friction factor is calculated through Blassius equation where C=0.046, n=0.2 for Turbulent flow, 𝜇 = 0.00089Pa.s at about 25 °C

f=C ( ρVDμ

)−n

¿0.046 (1000

kgm3×

7.2874ms

×0.006m

0.00089 Pa . s)

−0.2

¿0.005303

6. Calculating Friction Loss

Since fDarcy = 4fFanning, so the equation for calculating Friction loss will modified to

F=( 4 fLD

)(V2

2)❑

F=( 4∗0.005303∗10.006

)(7.28742

2)❑

F=93.8741 m2

s2

7. Calculate head loss, hcalculated

hcalc=Fg

¿93.87419.81

= 9.5692 m

8. Calculate the percentage difference

Percentage difference (%) = hcalc−hmeasured

hcalc

* 100 %

= 9.5692−8.9479

9.5692 * 100 %

= 6.49 %

Experiment D

Venturi Meter ( do = 16 mm , d1 = 26 mm, Cd = 0.97 )

Flowrate (L/min)

Pressure Difference (mH2O) Pressure Difference (mmH2O)

2nd minute (s)

4th minute (s)

6th minute (s)

Average Average

37 1.003 0.996 0.988 0.996 99632 0.758 0.737 0.732 0.742 74227 0.549 0.54 0.529 0.539 53922 0.37 0.366 0.363 0.366 36617 0.227 0.225 0.233 0.228 228

Oriface Meter ( do = 16 mm , d1 = 24 mm, Cd = 0.62 )

Flowrate (L/min)

Pressure Difference (mH2O) Pressure Difference (mmH2O)

2nd minute (s)

4th minute (s)

6th minute (s)

Average Average

30 0.236 0.238 0.235 0.236 23625 0.156 0.154 0.157 0.156 156

20 0.099 0.098 0.099 0.099 9915 0.055 0.052 0.053 0.053 5310 0.024 0.023 0.024 0.024 24

Pitot static tube

Flowrate (L/min)

Pressure Difference (mH2O) Pressure Difference (mmH2O)

2nd minute (s)

4th minute (s)

6th minute (s)

Average Average

35 0.088 0.089 0.085 0.087 8732.5 0.074 0.073 0.072 0.073 7330 0.053 0.048 0.05 0.050 5027.5 0.033 0.036 0.034 0.034 3425 0.015 0.014 0.013 0.014 14

Venturi Meter ( do = 16 mm , d1 = 26 mm, Cd = 0.97 )

Flow Rate, Q (L/min)

Flow Rate, Q (m3/s)

∆P (mH20)

∆P (Pa)

h actual (m)

h calculated (m)

Error percentage (%)

37 0.000617 0.996 9767.2 0.996 0.999 0.3032 0.0005337 0.742 7276.3 0.742 0.746 0.5327 0.00045 0.539 5285.6 0.539 0.545 1.1122 0.000367 0.366 3589.1 0.366 0.376 2.7317 0.000283 0.228 2235.8 0.228 0.238 4.38

Oriface Meter ( do = 16 mm , d1 = 24 mm, Cd = 0.62 )

Flow Rate, Q (L/min)

Flow Rate, Q (m3/s)

∆P (mH20)

∆P (Pa)

h actual (m)

h calculated (m)

Error percentage (%)

30 0.0005 0.236 2314.3 0.591 0.593 0.3425 0.000417 0.156 1529.8 0.312 0.314 0.6420 0.000333 0.099 970.8 0.158 0.161 1.8915 0.00025 0.053 519.7 0.069 0.072 4.3410 0.000167 0.024 235.4 0.028 0.03 7.14

Pitot static tube

Flow Rate, Q (L/min)

Flow Rate, Q (m3/s)

∆P (mH20) ∆P (Pa)

h actual (m)

h calculated (m)

Error percentage (%)

35 0.000583333 0.087 853.15506

0.087 0.089 2.298850575

32.5 0.000541667 0.073 715.86574

0.073 0.076 4.109589041

30 0.0005 0.05 490.319 0.05 0.054 8

27.5 0.000458333 0.034 333.41692

0.034 0.035 2.941176471

25 0.000416667 0.014 137.28932

0.014 0.015 7.142857143