Edibon Fluid Flow Friction in Pipes AFT M7 Eng PDF

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PRACTICAL EXERCISES MANUALRef.: AFT/AFTB/AFTC/AFTP Date: September 2013 Pg: 1 / 163TABLE OF CONTENTS7 PRACTICAL EXERCISES MANUAL ..................................................................................... 3 7 INTRODUCTION .......................................................................

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PRACTICAL EXERCISES MANUAL Ref.: AFT/AFTB/AFTC/AFTP

Date: September 2013

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TABLE OF CONTENTS 7

PRACTICAL EXERCISES MANUAL ..................................................................................... 3 7.1

INTRODUCTION .......................................................................................................................... 3

7.2

DESCRIPTION .............................................................................................................................. 5

7.2.1 7.2.2 7.2.3

SPECIFICATIONS ..................................................................................................... 6 PRACTICAL POSSIBILITIES .................................................................................. 9 DIMENSIONS AND WEIGHT ................................................................................ 13

7.3

THEORY ...................................................................................................................................... 14

7.4

LABORATORY PRACTICAL EXERCISES ........................................................................... 26

7.4.1 Practical exercise 1: Pressure drop due to friction in a rough pipe with an inner diameter of 17mm ..................................................................................................................... 26 7.4.2 Practical exercise 2: Pressure drop due to friction in a rough pipe with an inner diameter of 23mm ..................................................................................................................... 30 7.4.3 Practical exercise 3: Pressure drop due to friction in a smooth pipe with an inner diameter of 6.5mm .................................................................................................................... 34 7.4.4. Practical exercise 4: Pressure drop due to friction in a smooth pipe with an inner diameter of 16.5mm .................................................................................................................. 38 7.4.5. Practical exercise 5: Pressure drop due to friction in a smooth pipe with an inner diameter of 26.5 mm ................................................................................................................. 42 7.4.6. Practical exercise 6: Influence of the diameter in the pressure drop due to friction in rough pipes ................................................................................................................................ 46 7.4.7. Practical exercise 7: Influence of the diameter in the pressure drop due to friction in smooth pipes.............................................................................................................................. 48 7.4.8. Practical exercise 8: Influence of the roughness in the pressure drop ...................... 50 7.4.9. Practical exercise 9: Friction coefficient in a rough pipe with an inner diameter of 17 mm 52 7.4.10. Practical exercise 10: Friction coefficient in a rough pipe with an inner diameter of 23 mm 55 7.4.11. Practical exercise 11: Friction coefficient in a smooth pipe with an inner diameter of 6.5 mm 58 7.4.12. Practical exercise 12: Friction coefficient in a smooth pipe with an inner diameter of 16.5 mm 61 7.4.13. Practical exercise 13: Friction coefficient in a smooth pipe with an inner diameter of 26.5 mm 64 7.4.14. Practical exercise 14: Influence of the diameter in the friction coefficient in rough pipes 67 7.4.15. Practical exercise 15: Influence of the diameter in the friction coefficient in smooth pipes 69 7.4.16. Practical exercise 16: Friction coefficient in smooth and rough pipes ..................... 71 7.4.17. Practical exercise 17: Pressure drop in an angle-seat valve ...................................... 73 7.4.18. Practical exercise 18: Pressure drop in a gate valve ................................................. 77 7.4.19. Practical exercise 19: Pressure drop in a diaphragm valve ....................................... 81 7.4.20. Practical exercise 20: Pressure drop in a ball valve .................................................. 85 7.4.21. Practical exercise 21: Comparison of pressure drop in different types of valves ..... 89

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7.4.22. 7.4.23. 7.4.24. 7.4.25. 7.4.26. 7.4.27. 7.4.28. 7.4.29. 7.4.30. 7.4.31. 7.4.32. 7.4.33. 7.4.34.

Practical exercise 22: Pressure drop in the in-line strainer ....................................... 91 Practical exercise 23: Pressure drop in a 90º elbow .................................................. 95 Practical exercise 24: Pressure drop in a double 90º elbow ...................................... 99 Practical exercise 25: Pressure drop in a 45º elbow ................................................ 103 Practical exercise 26: Pressure drop in a 45º tee ..................................................... 107 Practical exercise 27: Pressure drop in an inclined tee ........................................... 111 Practical exercise 28: Pressure drop in a symmetrical Y branch ............................ 115 Practical exercise 29: Pressure drop in a narrowing ............................................... 119 Practical exercise 30: Pressure drop in a gradual widening .................................... 124 Practical exercise 31: Pressure drops in a diaphragm ............................................. 129 Practical exercise 32: Comparison of pressure drop in the different fittings .......... 133 Practical exercise 33: Flow measurement with the Venturi meter .......................... 135 Practical exercise 34: Determination of the discharge factor Cd in the Venturi tube 139 7.4.35. Practical exercise 35: Flow measurement with the Pitot tube................................. 141 7.4.36. Practical exercise 36: Determination of the discharge factor Cd in the Pitot tube... 145 7.4.37. Practical exercise 37: Comparison between the flow measured in the Venturi and Pitot tubes ................................................................................................................................ 147

7.5

7.5.1 7.5.2 7.5.3 7.5.4 7.5.5

ANNEXES .................................................................................................................................. 149

ANNEX A: Assembly and installation ................................................................... 149 ANNEX B: Filling the manometers ........................................................................ 154 ANNEX C: Operation mode of the displacement sensors (AFTC) ........................ 156 ANNEX D: Universal graph ................................................................................... 157 ANNEX E: Tables................................................................................................... 158

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7 PRACTICAL EXERCISES MANUAL 7.1 INTRODUCTION This unit is designed to study the behaviour of closed flows. It makes it possible to study pressure drops in pipes as well as in different hydraulic accessories. The losses by friction in straight pipes of different sizes can be studied on a certain range of the Reynolds’ number. This way, the different types of flows are classified as:  Flow in laminar regime.  Flow in turbulent regime. Osborne Reynolds made a difference between laminar and turbulent flows in pipes in his publication in 1883. Ludwig Prandtl, Thomas Stanton and Paul Blasius analysed the flow data in pipes later on in the beginning of last century, and they created the graph that is well known as the “Stanton Diagram”. John Nikuradse extended the work to cover the case of rough pipes, like the one supplied with this equipment, which have different degrees of roughness in order to compare the currents. Friction in pipes is one of the classic laboratory experiments and it has always had a place in the practical teaching of fluid mechanics. The results and the underlying principles are very important for aeronautical, industrial and mechanical engineers.

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All the necessary instruments are included with the unit and it is supplied as a complete unit.

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7.2 DESCRIPTION The test bench used to study pressure drops in pipes, which we can see in the figure 1.0.1, supplied with either the Basic Hydraulic Feed System or the Hydraulic Bench, and to which we will refer next, basically consists of:  An aluminium panel placed vertically, where all the elements to be studied are located.  A pumping and flow regulation system, which will be the Hydraulic Bench, FME00, or the Basic Hydraulic Feed System, FME00/B. They include all the elements and accessories needed for the equipment to work in an autonomous way. They can be used together with other equipment of the Fluid Mechanics range of EDIBON.

There are 4 different models of the equipment: AFT: the device includes the FME00 hydraulic bench and has a rotameter incorporated (range: 600-6000 l/h). AFT/B: the device includes the FME00/B basic hydraulic feed system. In this case the device does not have a rotameter incorporated inside because it is included in FME00/B. AFT/P: only the device. It does not include FME00 or FME00/B. And, finally, the most advanced one: AFTC: the device structure is the same as that of the previous devices, but

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in this case it is computerised. It includes the FME00 hydraulic bench. The device consists of: - Flow sensor: range 0-150 l/min. - Pressure sensor: 2 units with a range of 0-2 bar. - Displacement sensor: 2 units with a range of 0-1 meter (0.5 precision) 7.2.1 SPECIFICATIONS The unit consists of: Types of pipes: 1. Rough pipe (PVC covered in sand) with an external diameter of 25mm and an internal diameter of 17mm. 2. Rough pipe (PVC covered in sand) with an external diameter of 32mm and an internal diameter of 23mm. 3. Smooth pipe (methacrylate) with an external diameter of 10mm and an internal diameter of 6.5mm. 4. Smooth pipe (PVC) with an external diameter of 20mm and an internal diameter of 16.5mm. 5. Smooth pipe (PVC) with an external diameter of 32mm and an internal diameter of 26.5mm.

Types of valves:

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1. Angle-seat valve with inner diameter of 20mm. 2. Gate valve with inner diameter of 20mm. 3. Diaphragm valve with inner diameter of 20mm. 4. Ball valve with inner diameter of 20mm.

Types of couplings: 1. In-line strainer. Inner diameter of 20mm. 2. Elbow of 90º. Inner diameter of 20mm. 3. Double elbow of 90º. Inner diameter of 20mm. 4. Elbow of 45º. Inner diameter of 20mm. 5. T of 45º. Inner diameter of 20mm. 6. Inclined T. Inner diameter of 20mm. 7. Symmetrical Y branch. Inner diameter of each pipe 20mm. 8. Gradual narrowing. Its section changes from 40mm to 25mm. 9. Gradual widening. Its section changes from 25mm to 40mm.

Special couplings: 1. Pitot tube of 30mm long, external diameter of 4mm and internal diameter of 2.5mm.

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2. Venturi tube of 180mm long, larger section of 32mm and minor section of 20mm. 3. Diaphragm with a measuring plate, larger diameter of 25mm and minor diameter of 20mm.

The circuits have 7 ball valves (V1-V7), required to distribute the current flow through the different elements tested. The equipment has differential anti-obturant pressure sensors, located at the beginning and at the end of every element studied. Each one of them connects easily to Bourdon type (24) and water manometers (25). The Bourdon manometer will be used to measure larger differences of pressure, while the water manometer will be used to measure small differences of pressure. The columns of the water manometer are communicated between them by a collector located at their top. In one of its sides it has the valve necessary to connect a one-way valve with fast plugs. The manometers’ level can be adjusted by using a manual air pump, connecting it to the one-way valve and pressurising the system. If you wanted to take air out, you would have to disconnect the nylon pipe from the collector’s fast plug. If it is the first time the Bourdon manometer is used, it must be previously prepared. In order to do so, cut the black plug located at the top of the dial off both of them. The transparent polyethylene tubes are also included, so any pair of

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pressure tapping can be promptly connected to one of the two manometers. The relation between the tube’s diameter and the distance between the pressure intakes at the sides of each tube has been set in order to minimise the input and output effects. The flow can be controlled with the regulation valves, both the AFT’s output valve as well as the output one of the pumping system. This last one also makes it possible to adjust the static pressure of the system conveniently depending on the kind of experiment that is going to be performed. The electrical power is supplied to the fluid with a centrifugal pump located inside the Hydraulic Bench or next to the Basic Hydraulic Feed System. This pump is activated and stopped with the on/off switch located in the front panel of both the Hydraulic Bench and the Basic Hydraulic Feed System.

7.2.2 PRACTICAL POSSIBILITIES This unit enables to carry out the following experiments: Obtaining pressure drops in different types of pipes:  Obtaining the pressure drop due to friction in a rough pipe with an inner diameter of 17mm.  Obtaining the pressure drop due to friction in a rough pipe with an inner diameter of 23mm.  Obtaining the pressure drop due to friction in a smooth pipe with an

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inner diameter of 6.5mm.  Obtaining the pressure drop due to friction in a smooth pipe with an inner diameter of 16.5mm.  Obtaining the pressure drop due to friction in a smooth pipe with an inner diameter of 26.5 mm. Comparison of the different parameters that affect pressure drops:  Influence of the diameter in the pressure drop due to friction in rough pipes.  Influence of the diameter in the pressure drop due to friction in smooth pipes.  Influence of the roughness in the pressure drop.  Obtaining the friction coefficient in a rough pipe with an inner diameter of 17 mm.

Calculation of the friction coefficient in different types of pipes:  Calculation of the friction coefficient in a rough pipe with an inner diameter of 17 mm.  Calculation of the friction coefficient in a rough pipe with an inner diameter of 23 mm.  Calculation of the friction coefficient in a smooth pipe with an inner diameter of 6.5 mm.

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 Calculation of the friction coefficient in a smooth pipe with an inner diameter of 16.5 mm.  Calculation of the friction coefficient in a smooth pipe with an inner diameter of 26.5 mm.

Influence of different parameters in the friction coefficient:  Influence of the diameter in the friction coefficient in rough pipes.  Influence of the diameter in the friction coefficient in smooth pipes.  Calculation of the friction coefficient in smooth and rough pipes.

Obtaining the pressure drop in different types of valves: - Obtaining the pressure drop in an angle-seat valve. - Obtaining the pressure drop in a gate valve. - Obtaining the pressure drop in a diaphragm valve. - Obtaining the pressure drop in a ball valve.

Comparison between different types of valves: - Comparison of pressure drops in different types of valves.

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Obtaining the pressure drop in different types of fittings: - Obtaining the pressure drop in an in-line strainer. - Obtaining the pressure drop in a 90º elbow. - Obtaining the pressure drop in a 90º double elbow. - Obtaining the pressure drop in a 45º elbow. - Obtaining the pressure drop in a 45º T. - Obtaining the pressure drop in an inclined T. - Obtaining the pressure drop in a symmetrical Y branch. - Obtaining the pressure drop in a narrowing. - Obtaining the pressure drop in a gradual narrowing. - Obtaining the pressure drop in a diaphragm.

Comparison between different types of fittings: - Comparison of pressure drops in the fittings.

Flow measurement through different systems: - Flow measurement with a Venturi meter. - Determination of the discharge coefficient Cd in a Venturi tube.

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- Flow measurement with a Pitot tube. - Determination of the discharge coefficient Cd in a Pitot tube.

Comparison between different systems: - Comparison between the flows measured in the Venturi and Pitot tubes.

7.2.3 DIMENSIONS AND WEIGHT The maximum dimensions of the AFT/AFTB/AFTC/AFTB unit are: APPROXIMATE HEIGHT: 1000 mm. APPROXIMATE LENGTH: 2300 mm.

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7.3 THEORY Osborne Reynolds demonstrated that two types of currents could be established inside a pipe.  Laminar flow regime. There is a proportion relation between the pressure drop and the current velocity.  Turbulent flow regime. Pressure drop is proportional to the square of the velocity. He also observed that there was an area between one and the other behaviour where it did not exist a clear relation between the pressure loss and the flow velocity. He achieved to classify the kind of current regardless of the size and type of pipe through a dimensionless parameter, the Reynolds number.

Re 

 u d 

(1)

being: : The fluid density [kg/m3] U: its velocity [m/s] : The dynamic viscosity [kg/m· s] d: The pipe diameter [m]

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The kinematic viscosity  and dynamic viscosity  can be related by means of the following expression:



Re 

 

(2)

ud

(3)



being the Reynolds number in function of the velocity and the inner diameter of the pipe and inversely proportional to the kinematic viscosity. The following table indicates the values of the water kinematic viscosity depending on the temperature:

Temperature (ºC)

Kinematic viscosity (m2/seg).10-6

5

1.52

10

1.308

15

1.142

20

1.007

25

0.897

30

0.804

35

0.727

40

0.661

50

0.556 Table 3.1.1

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The flows inside two geometrically identical pipes obey...