lab report on fitting loss

8/12/2019 Lab Report on Fitting Loss

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Title: Fluid Flow Friction and Fitting Loss

Objective: The experiment was conducted to determine the pressure or head loss in different diameter pipes,

joints and valves.

Introduction:

Newtons Third Law of Motion states that for every action there is an equal and opposite reaction to it.

This law applies to fluid flow as well. In a fluid flow, there must be a certain amount of energy to keep the fluid

moving, and a portion of this energy is lost due to the resistance that exists against the fluid flow, which usually

is termed the head loss due to friction. The friction causes eddies and turbulences in the current and is caused by

two main factors, namely the viscosity of the fluid in which the higher the viscosity of the fluid, the greater the

friction acting against the fluid flow and the condition of the inside of the pipe, whereby the rougher the surface

of the inner pipe, the greater the friction acting against the fluid flow. The head loss of the fluid flow is also

affected by the changes in the direction of the flow, usually when the fluid flows in elbows, pipe bends,

junctions and valves. The diameter of the pipe also has an effect on the head loss of the fluid flow whereby

when the diameter of the pipe gets smaller, the flow area decreases. This causes the velocity of the fluid to

increase and as the velocity increases, the head loss due to friction also increases. For a laminar fluid flow with

a Reynolds Number of less than 2000, the head loss is calculated with the equation:

Where = fluid viscosity, = pipe length, d= pipe diameter and Q= volume flowrate

And for a turbulent flow with a Reynolds Number exceeding 4000, the head loss is computed with the

equation, taking into account the wall shear stress:

Where = friction factor, V = fluid velocity

Apparatus: Piping Loss Test Set

Procedure:

1. It is ensured that the water tank was full and all the valves of the set are shut.2. The main power of the test set is switched on and the water pump is checked to ensure it is running.3. The bypass valve and the flow regulating valve is adjusted to achieve the desired volumetric flow

rate.

4. All valves are turned off except V1, then the pressure meter is connected to measure the head lossacross the 8mm copper pipe.

5. The V1is then turned off while the valve V2is turned on. The head loss is then measured across thecontraction, 12mm PVC pipe and the enlargement portion.


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6. The V2 valve is then turned off while the valve V3is turned on. The head loss is then measuredacross the 15.5 mm pipe.

7. The V3valve is turned off and the V4is turned on next. The head loss in the 0elbow, 0T-joint, in-line strainer, gate valve and globe valve is then measured.

8. The experiment is repeated with different flow rates and all the data obtained is recorded in the tableprovided.

Results :

Flow rate 4 GPM,

0.0003 m3/s

6 GPM,

0.0004 m3/s

8 GPM,

0.0005 m3/s

10 GPM,

0.0006 m3/s

12 GPM,

0.0008 m3/s

Fitting Pressure Drop (mH2O)

Straight Pipes

8 mm copper

tube

1.13 2.23 3.71 5.50 7.35

Flow rate 4 GPM,0.0003 m3/s 7.5 GPM,0.0006 m

3/s 11 GPM,0.0007 m

3/s 14.5GPM,0.0009 m

3/s 18 GPM,0.0011 m

3/s


Straight Pipes

12 mm (PVC) 0.12 0.33 0.61 0.91 1.27

15.5mm (PVC) 0.06 0.12 0.23 0.35 0.48

18 mm (PVC) 0.07 0.20 0.38 0.52 0.72

Sudden

contraction

0.1 0.33 0.63 0.97 1.30

Bends

4 -joint 0 0.01 0.03 0.04 0.05

Flow rate 7 GPM,

0.0004 m3/s

9 GPM,

0.0006 m3/s

11 GPM,

0.0007 m3/s

13 GPM,

0.0008 m3/s

15 GPM,

0.0009 m3/s


Bends

0lbow 0.02 0.09 0.16 0.22 0.31

0T-joint 0.06 0.14 0.23 0.29 0.4

Valve

Gate 0.13 0.21 0.29 0.38 0.48

Ball 0.25 0.42 0.58 0.75 0.93

Globe 1.95 3.15 4.35 5.88 7.04In-line strainer 3.8 6.25 9.05 11.6 14.6

Flow rate 8 GPM,0.0005 m

3/s

10 GPM,0.0006 m

3/s

12 GPM,0.0008 m

3/s

14 GPM,0.0009 m

3/s

16 GPM,0.001 m

3/s


Bends

0end 0.02 0.08 0.15 0.21 0.30


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Flow rate 10 GPM,

0.0006 m3/s

12 GPM,

0.0008 m3/s

14 GPM,

0.0009 m3/s

16 GPM,

0.001 m3/s

18 GPM,

0.0011 m3/s


Straight Pipes

Sudden

enlargement

0.01 0.02 0.03 0.04 0.05

Fitting Flowrate : 4 GPMStraight Pipes h l / d V / 2g Friction

factor, Friction factor,k8mm copper

tube

1.1296 125 1.2842 0.007 -

12mm (PVC) 0.12 83.33 0.2537 0.0057 -

15.5mm (PVC) 0.059 64.51 0.0911 0.0102 -

18mm (PVC) 0.07 55.55 0.0501 0.0251 -

Sudden

contraction

0.099 - 2.4991 - 0.04

4-joint 0 - 0 - 0.4

Fitting Flowrate : 6 GPM

Straight Pipes h l / d V / 2g Friction

factor, Friction factor,k8mm coppertube

2.299 125 2.8897 0.0062 -

Fitting Flowrate : 7 GPMBends h l / d V / 2g Friction

factor, Friction factor,k0lbow 0.019 - 0.0133 - 1.5

0T-joint 0.059 - 0.0299 - 2.0

Valves

Gate 0.129 - 0.8664 - 0.15

Ball 0.249 - 4.9983 - 0.05

Globe 1.949 - 0.1949 - 1.95

Inline strainer 3.799 - 47.4838 - 0.08

Fitting Flowrate : 7.5 GPM


factor, Friction factor,k12mm (PVC) 0.3299 83.33 0.8919 0.0044 -

15.5mm (PVC) 0.1199 64.51 0.3204 0.0058 -

18mm (PVC) 0.1999 55.56 0.1762 0.0204 -

Sudden

contraction

0.3299 - 8.2472 - 0.04

4-joint 0.01 - 0.0249 - 0.4


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tube

3.7087 125 5.1372 0.0057 -

Bends

0end 0.0199 - 0.0182 - 1.1


Bends h l / d V / 2g Friction


0T-joint 0.1399 - 0.0699 - 2.0

Valves

Gate 0.2099 - 1.3995 - 0.15

Ball 0.4199 - 8.3971 - 0.05

Globe 3.1489 - 0.3149 - 10

Inline strainer 6.2479 - 78.0983 - 0.08




tube

5.4981 125 8.0268 0.0055 -

Sudden

enlargement

0.01 - 0.01 - 1.0

Bends

0end 0.0799 - 0.0727 - 1.1




15.5mm (PVC) 0.2299 64.51 0.6892 0.0052 -

18mm (PVC) 0.3799 55.56 0.3790 0.018 -

18mm (PVC) -

Sudden

contraction

0.6298 - 15.7446 - 0.04

0lbow 0.1599 - 0.1066 - 1.5

0T-joint 0.2299 - 0.1150 - 2.0

4-joint 0.0299 - 0.0749 - 0.4

Valves

Gate 0.2899 - 1.9327 - 0.15

Ball 0.5798 - 11.596 - 0.05

Globe 4.3485 - 0.4349 - 10

Inline strainer 9.0469 - 113.086 - 0.08


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tube

7.3475 125 11.5587 0.0051 -

Sudden

enlargement

0.0199 - 0.0199 - 1.0

Bends

0end 0.1499 - 0.1363 - 1.1




0T-joint 0.2899 - 0.1449 - 2.0

Valves

Gate 0.3798 - 2.5325 - 0.15

Ball 0.7497 - 14.99 - 0.05

Globe 5.8779 - 0.5878 - 10

Inline strainer 11.596 - 144.95 - 0.08



factor, Friction factor,kSudden

enlargement

0.0299 - 0.0299 - 1.0

Bends

0end 0.2099 - 0.1908 - 1.1

Fitting Flowrate : 14.5 GPM



15.5mm (PVC) 0.3499 64.51 1.1976 0.0045 -

18mm (PVC) 0.5198 55.56 0.6585 0.0142 -

Sudden

contraction

0.9697 - 24.242 - 0.04

4-joint 0.0399 - 0.0999 - 0.4



factor, Friction factor,k0Elbow 0.3099 - 0.2066 - 1.5

0T-joint 0.3999 - 0.1999 - 2.0

Valves

Gate 0.4798 - 3.1989 - 0.15

Ball 0.9297 - 18.59 - 0.05


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Globe 7.0376 - 0.70376 - 10

Inline strainer 14.595 - 182.44 - 0.08



factor, Friction factor,kSudden

enlargement

0.0399 - 0.0399 - 1.0

Bends

0end 0.2999 - 0.2726 - 1.1




15.5mm (PVC) 0.4798 64.51 1.8455 0.004 -

18mm (PVC) 0.7198 55.56 1.0148 0.0128 -

Suddenenlargement

0.0499 - 0.0499 - 1.0

Sudden

contraction

1.2996 - 32.4889 - 0.04

4-joint 0.0499 - 0.1249 - 0.4

0

2

4

6

8

10

12

14

16

0 5 10 15 20

8mm copper tube

12mm PVC

15.5mm PVC

18mm PVC

Sudden enlargement

Sudden contraction


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-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0 5 10 15 20

90bend

90elbow

90T-joint

45Y-joint


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Calculations:

For a straight pipe(8mm copper tube at 4GPM)

Q = 4 GPM = 0.000252 m3

/s, = 1.13 mH2O = 11 100 Pa,To calculate the cross-sectional area of the pipe,

A1=

=

= 5.027 x 10-5m2

To calculate for the velocity of manometer 1 when flow rate = 4.0 gallons/min or 0.0002523m3/s.

Q1 = A1v1

v1=

0

2

4

6

8

10

12

14

16

0 2 4 6 8 10 12 14 16

Gate

Ball

Globe

In line strainer


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=

= 5.02 m/s

To calculate for friction factor,

( )

1.13 mH2O 11 100 Pa =

To calculate for the head loss h,

()

= 0.007036 (125)(

)= 1.1296 m

For a sudden contractionfitting at 4GPM,

Q = 4GPM = 0.000252 m3

/s ,

=0.1 mH2O = 981 Pa

Assuming the sudden contraction fitting is well-rounded, the obtained from the textbook is 0.04To calculate for the velocity in the fitting, V,

Rearranging the equation,

= = 7.0036 m/s

To calculate for the head loss in the fitting, h,


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= 0.04 (

= 0.1 m

For a bend fitting0elbow at M

Q = 7 GPM = 0.0004416 m3/s, 0.02mH2O = 196 Pa

A regular 0threaded elbow has a KL value of 1.5

To calculate for the velocity in the fitting, V,


= = 0.5112 m/s


= 1.5 (

= 0.019 m

For a valve fitting(Gate valve at 7 GPM)

Q = 7 GPM = 0.0004416 m3/s, 0.13mH2O = 1274.83 Pa

A fully open gate valve has a KL value of 0.15

To calculate for the velocity in the fitting, V,


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= = 4.1228 m/s


= 0.15 (

= 0.129 m

Discussion:

From both the Actual measured pressure head values and the values for the Ideal pressure head

calculated, it is shown that at x = 43mm where the duct converges, the pressure head values dropped

significantly as the velocity of the fluid flow here increases before rising again back up at x = 78mm, where the

duct diverges. This verifies ernoullis Theorem whereby in a steady, incompressible fluid flow, when the

velocity of the fluid increases, the pressure of the fluid decreases. This phenomenon applies to all flow rates. By

comparing the Actual measured pressure heads obtained with the Ideal pressure head calculated with the

Bernoulli Equation, it can be seen very clearly, on a general overview, that the values of the Actual measured

pressure heads are lower than the Ideal pressure head values. For the Ideal case, it is assumed that there is no

frictional losses in a fluid flow, thus the total pressure heads will remain a constant. But in reality, there will

always be frictional losses in a fluid flow which could also be attributed to turbulences in the flow, thus the

Actual total pressure heads will be lower than the Ideal total pressure heads as the values for the actual pressure

heads obtained from the measurements will always be lower than the calculated ideal pressure heads. However,

observing the results in the tables closely, the actual pressure heads are higher than the ideal pressure heads at

the distance of x = 31mm. As the flow rate increases, especially to 6.0 and 6.5 gallons/min, the actual pressure

heads at x = 43mm and x = 78mm are also higher than the ideal pressure heads, resulting a negative head loss at

all these distances as the actual total pressure heads at these distances have a higher value than the ideal total

pressure heads. A plausible explanation is that at x = 31mm where the duct begins to converge, a possibility is

that flow separation occurred around this region in which sediments or dirt may exist causing the cross sectional

area of the flow to decrease resulting in a higher pressure head value. Since pressure is inversely proportional to

the cross-sectional area, as in the formula P = F/A, this supports the hypothesis that as the cross sectional area of


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the flow decreased, the pressure of the flow increased, which in turn would result in a higher actual pressure

head than the ideal value. And as pressure is directly proportional to the amount of force, it could also explain

that at higher flow rates, the actual pressure heads at x = 43mm and 78mm also turned out to be higher than the

ideal pressure heads.

Pressure head, x =

x (=Px (= ,where F is force and A is cross sectional area

If the convergent-divergent duct is inclined upwards, the increased potential energy will inevitably result

in decreased dynamic () and pressure ( ) heads. The velocity of the fluid flow will decrease since it isacting against the forces of gravity while travelling up a slope thus resulting in a decreased dynamic head. Since

according to ernoullis Theorem, velocity of the fluid flow is inversely proportional to the pressure of the

fluid, thus as the velocity decreases, the pressure of the fluid will subsequently increase, thus resulting in an

increased pressure head. The total head H when the duct is inclined will remain the same as when the

convergent-divergent duct is horizontal. This is in accordance with the Law of Conservation of Energy whereby

the total energy at the first point of the flow has to be equal to the total energy at the second point of the fluid

flow. Thus, each of the heads will balance each other out in order to obey the stated law. The total head will

always remain a constant along a streamline for the Ideal case. Thus, if frictional losses are taken into account,

the resulting total head will theoretically, be lesser than the total head of an ideal case.

Conclusion:

The application of the Bernoullisequation as applied to the flow in a convergent-divergent duct shows

that when the velocity of the fluid flow increases at the part where the duct converges, the pressure of the fluid

decreases and the same relationship applies when the velocity of the fluid flow decreases back again as the duct

diverges, the pressure increases. This relationship is brought forward as applied to the heads whereby as thepressure head increases, the velocity head decreases. It is also shown that the actual measured pressure heads

are lower than the ideal calculated pressure heads. This is due to frictional losses in the fluid flow which occur

in reality, thus the corresponding actual total heads will also be lower than the ideal total heads calculated using

the ernoullis quation.

Reference:


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i) Munson, B.R., Okiishi, T.H., Huebsch, W.W., & Rothmayer, A.P. (2013).Fundamentals ofFluid Mechanics (7

thed.). United States of America: John Wiley & Sons, Inc.

ii) Sleigh, A., & Noakes, C. (2009). The Bernoulli Equation.Retrieved June 15, 2014 from

http://www.efm.leeds.ac.uk/CIVE/CIVE1400/Section3/bernoulli.htm

lab report on fitting loss

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