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PRACTICAL EXERCISES MANUAL

Unit ref.: FME-04Date: September 2013Pg: 1/25

TABLE OF CONTENTS

7PRACTICAL EXERCISES MANUAL27.1DESCRIPTION OF THE UNIT27.1.1Description27.1.2Practical possibilities37.1.3Specifications47.1.4Dimensions and weight67.1.5Required services77.2LABORATORY PRACTICAL EXERCISES87.2.1Practical exercise 1: Determination of the discharge coefficient for the Venturi type thin wallnozzle..87.2.2Practical exercise 2: Determination of the velocity coefficient for the Venturi type thin wallnozzle.117.2.3Practical exercise 3: Determination of the contraction coefficient for the Venturi type thin wallnozzle.147.2.4Practical exercise 4: Determination of the load coefficient for the diaphragm type thin wallnozzle...177.2.5Practical exercise 5: Determination of the velocity coefficient for the diaphragm type thin wallnozzle...177.2.6Practical exercise 6: Determination of the contraction coefficient for the diaphragm type thin wallnozzle..177.2.7Practical exercise 7: Determination of the discharge coefficient for the colloidal type thin wallnozzle...177.2.8Practical exercise 8: Determination of the velocity coefficient for the colloidal type thin wallnozzle.177.2.9Practical exercise 9: Determination of the contraction coefficient for the colloidal type thin wallnozzle...177.2.10Practical exercise 10: Determination of the discharge coefficient for the cylindrical type thickwall nozzle187.2.11Practical exercise 11: Determination of the velocity coefficient for the cylindrical type thick wallnozzle187.2.12Practical exercise 12: Determination of the contraction coefficient for the cylindrical type thickwall nozzle187.2.13Practical exercise 13: Determination of the discharge coefficient for the Venturi type thick wallnozzle187.2.14Practical exercise 14: Determination of the velocity coefficient for the Venturi type thick wallnozzle187.2.15Practical exercise 15: Determination of the contraction coefficient for the Venturi type thick wallnozzle187.2.16Analysis of the results207.2.17Observations of interest237.2.18Reflections and questions24

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7 PRACTICAL EXERCISES MANUAL

7.1 DESCRIPTION OF THE UNIT

7.1.1 Description The accessory consists of a transparent cylindrical tank that is fed for the superior, part, from the Bench FME00 or the Hydraulic Group FMEO0B. The water of the tank flows through an interchangeable mouthpiece (a game of 5 mouthpieces is given that represent orifices of different characteristics) located in the center of the base. The liquid flowing vein goes directly to the volumetric tank of the Bench or of the Hydraulic Group.

Figure 1.1.1 A tube of Pitot can be placed in any point of the flowing vein to determine its total height of load. A traverse device, joined to the tube of Pitot, allows to determine the diameter of the liquid flowing vein. You can measure the height of the tube of Pitot and the total height through the orifice, in a panel of 2 manometric tubes located beside the tank.

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Figure 1.1.2

7.1.2 Practical possibilities To determine the discharge coefficient C for mouthpiece 1. To determine the velocity coefficient Cv for mouthpiece 1. To determine the contraction coefficient Cc for mouthpiece 1. To determine the discharge coefficient Cv for mouthpiece 2. To determine the velocity coefficient C, for mouthpiece 2. To determine the contraction coefficient Cc for mouthpiece 2. To determine the discharge coefficient C for mouthpiece 3. To determine the velocity coefficient C, for mouthpiece 3. To determine the contraction coefficient Cc for mouthpiece 3. To determine the discharge coefficient C for mouthpiece 4. To determine the velocity coefficient C, for mouthpiece 4. To determine the contraction coefficient Cc for mouthpiece 4. To determine the discharge coefficient Cv for mouthpiece 5. To determine the velocity coefficient C, for mouthpiece 5. To determine the contraction coefficient Cc for mouthpiece 5.

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Unit ref.: FME-04

7.1.3 Specifications

1.

Date: September 2013Pg: 4/25

Five types of mouthpieces: :

Figure 1.3.1: Interchangeable mouthpieces

Figure 1.3.2: Mouthpiece N 1: Venturi type nozzle of thin wall.

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Figure 1.3.3: Mouthpiece N 2: Nozzle of this wall Diaphragm type.

Figure 1.3.4: Mouthpiece N type thin wall

3: Nozzle of Colloidal

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Figure1.3.5: Mouthpiece N 4: Nozzle of Cylindrical type thick wall

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Figure1.3.6: Mouthpiece N 5: Nozzle of Venturi typethick wall

2. Height of maximum load: 400 mm.

7.1.4 Dimensions and weight

- Approximate dimensions: 450x450x900 mm

- Approximate volume: 0.18 m3

- Approximate weight: 15 kg.

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7.1.5 Required services

- Hydraulic bench (FME00) or Hydraulic Group (FMEO0B).

- Set of additional mouthpieces (not supplied).

- Chronometer (not supplied).

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7.2 LABORATORY PRACTICAL EXERCISES

7.2.1 Practical exercise1: Determination of the discharge coefficient for theVenturi type thin wall nozzle

7.2.1.1 Objectives To show and to determine the characteristics of a liquid flow through an orifice. To determine the discharge coefficients (Ca) for a certain constant value of the load height (h).

7.2.1.2 Experimental procedure

1.Assemble the device on the channel of the Hydraulic Bench and level it, so itis horizontal.2. Connect the inlet tube of the device, by means of a flexible conduit (6), to the driving outlet mouthpiece of the Hydraulic Bench. The device should be ready to discharge directly in the channel. The leakage that can take place through the overflow should directed to drain in the overflow channel of the volumetric tank. 3. To obtain readings that are the most stable as possible, the position of the inlet vertical tube should be adjusted so that, the diffuser is simply hidden under the surface free of water in the tank.



Figure 2.1.1: Placement of the equipment in the Hydraulic Bench

4. Place mouthpiece N 1: nozzle of thin wall, Venturi type. Write down the diameter of the discharge orifice. 5. Introduce water in the tank to fill it until the superior level of the overflow tube is reached. Regulate the flow that has been introduced to have a small discharge through the overflow, assuring this way the perseverance of the water level in the tank while the measurements are made. Note: If the device is being used with the Hydraulic Group, the flow measure is directly obtained from the flowmeter assembled in the group. For it, the water level in the FME04 should be below the overflow to guarantee us that the impelled water is similar to the water drained by the orifice.

6. The discharge coefficient is determined by means of the following equation:

Cu = o-2gh

7. Vary the water flow and determine for each case the discharge coefficient.

8. Complete the following table of results:

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QHCiA(1/min)(m)

Table 2.1.1

The flows obtained with different load heights will be registered in table 2.1.1 and, as a result of these measures, they should be obtained a value, Cd = 0.63 where

Cd =A.


Unit ref.: FME-04Date: September 2013Pg:11/25

7.2.2 Practical exercise2: Determination of the velocity coefficient for theVenturi type thin wall nozzle

7.2.2.1 Objectives To show and to determine the characteristics of a liquid flow through an orifice. To determine the Velocity coefficients (Cv) for a certain constant value of the load height (h).

7.2.2.2 Experimental procedure

1.Assemble the device on the channel of the Hydraulic Bench and level it sothat it is horizontal.2. Connect the inlet tube to the device, by means of a flexible conduit (6), to the output driving mouthpiece of the Hydraulic Bench. The device should be ready to discharge directly in the channel. The leakage that can take place through the overflow should be directed to drain in the overflow channel of the volumetric tank. 3. To obtain readings that are the most stable as possible, the position of the inlet vertical tube should be adjusted so that, the diffuser is simply hidden under the surface free of water in the tank. 4. Place mouthpiece N 1. nozzle of thin wall, Venturi type. Write down the diameter of the discharge orifice.

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Unit ref.: FME-04Date: September 2013Pg: 12/255. Introduce water in the tank to fill it until the superior level of the overflow tube is reached. Regulate the flow that has been introduced to have a smalldischarge through the overflow, assuring this way the perseverance of the water level in the tank while the measurements are made.Note: If the device is being used with the Hydraulic Group, the flow measure is directly obtained from the flowmeter assembled in the group. For it, the water level in the FME04 should be below the overflow to guarantee us that the impelled water is similar to the water drained by the orifice.6. To see the velocity coefficient, Cv, it is necessary to place the tube of Pitot inside the liquid flowing vein, in the contracted section (place 1.5 times theorifice diameter, below the plane in which it is contained). Write down the load height indicated by the tube of Pitot, hc.7. Write down the height of the water level, obtained by means of the second manometric tube placed in the panel.

8. The velocity coefficient is determined by means of the following equation:CV Vh

==where h, is the total height obtained by the tube of Pitot andVhh the height of the liquid.

9. Vary the water flow and determine, for each case, the velocity coefficient.

10.Complete the following table of results:



HeHCv(m)(m)

Table 2.2.1

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Unit ref.: FME-04Date: September 2013Pg:14/25

7.2.3 Practical exercise 3: Determination of the contraction coefficient for the Venturi type thin wall nozzle

7.2.3.1 Objectives To show and to determine the characteristics of the liquid flow through an orifice. To determine the contraction coefficients (Ce) for a certain constant value of the load height (h).

7.2.3.2 Procedure 1. Assemble the device on the channel of the Hydraulic Bench and level it so that it is horizontal. 2. Connect the inlet tube to the device, by means of a flexible conduit (6), to the output driving mouthpiece of the Hydraulic Bench. The device should be ready to discharge directly in the channel. The leakage that can take place through the overflow should be directed to drain in the overflow channel of the volumetric tank. 3. To obtain readings that are the most stable as possible, the position of the inlet vertical tube should be adjusted so that, the diffuser is simply hidden under the surface free of water in the tank. 4. Place mouthpiece N 1. nozzle of thin wall, Venturi type. Write down the diameter of the discharge orifice. 5. Introduce water in the tank to fill it until the superior level of the overflow tube is reached. Regulate the flow that has been introduced to have a small

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discharge through the overflow, assuring this way the perseverance of the water level in the tank while the measurements are made. Note: If the device is being used with the Hydraulic Group, the flow measure is directly obtained from the flowmeter assembled in the group. For it, the water level in the FME04 should be below the overflow to guarantee us that the impelled water is similar to the water drained by the orifice. 6. To obtain the contraction coefficient C0 it is necessary to measure the diameter of the liquid vein in the contracted section. For it, the blade has to be used, which is coupled to the tube of Pitot and placed perpendicularly to its displacement direction. The sharp border of the blade is located, approximately, in the contracted section and tangent (with the help of the ferrule that allows its advance and setback along the displacement screw (1mm/turn)) in a point of the contour of the flowing vein and, later on, it moves until being tangent in the diametrically opposed point of this contour. The situation of both positions settles down with controlled readings in the graduated ferrule and the advance screw; the difference of the readings corresponding to the two positions represents the diameter of the vein.

7. Write down the contraction diameter for each flow.

8. The velocity coefficient is determined by means of the following equation:

aC =cac=

2dc where al. is the area of the contracted vein and a the area ofd3

the mouthpiece.

9. Vary the water flow and determine, for each case, the velocity coefficient.

10.Complete the following table of results:


Unit ref.: FME-04

acQ(m)L/min

Table 2.3.1

Date: September 2013Pg: 16/25

Cc



7.2.4 Practical exercise4: Determination of the load coefficient for thediaphragm type thin wall nozzle

Repeat the experiment 7.2.1 but change the mouthpiece 1 for 2.

7.2.5 Practical exercise5: Determination of the velocity coefficient for thediaphragm type thin wall nozzle

Repeat experiment 7.2.2, but change mouthpiece 1 for mouthpiece 2.

7.2.6 Practical exercise6: Determination of the contraction coefficient for thediaphragm type thin wall nozzle

Repeat experiment 7.2.3 but change mouthpiece 1 for mouthpiece 2.

7.2.7 Practical exercise7: Determination of the discharge coefficient for thecolloidal type thin wall nozzle


7.2.8 Practical exercise8: Determination of the velocity coefficient for thecolloidal type thin wall nozzle


7.2.9 Practical exercise9: Determination of the contraction coefficient for thecolloidal type thin wall nozzle




7.2.10Practical exercise10: Determination of the discharge coefficient for thecylindrical type thick wall nozzle


7.2.11Practical exercise11: Determination of the velocity coefficient for thecylindrical type thick wall nozzle


7.2.12 Practical exercise12: Determination of the contraction coefficient for thecylindrical type thick wall nozzle


7.2.13Practical exercise13: Determination of the discharge coefficient for theVenturi type thick wall nozzle

Repeat experiment 7.2.1 but change mouthpiece 1 for mouthpiece 5

7.2.14Practical exercise14: Determination of the velocity coefficient for theVenturi type thick wall nozzle


7.2.15Practical exercise15: Determination of the contraction coefficient for theVenturi type thick wall nozzle



Unit ref.: FME-04Date: September 2013Pg: 19/25Note: It is considered that, approximately, with determining eight values of different flows it is enough to establish the relationship, Q = f(h) between the flow and the load height on the plane of the orifice.


eC I 00Unit ref.: FME-04Date: September 2013

7.2.16Analysis of the results

With the previous results, verify the following equation:

CuCy Cc

Table to register the measures of Q and of h:

VolumeTimeFlow (Q)Load height1sm3/s(h) mm

Table 2.13.1

Pg: 20/25

H 1/2m 1/2

With the data of this table represent, according to the graphic type which is going to be described next:

Q = F (H %)

Graphic type to indicate the variation of Q in function of h '/2

CC I0

Q

PRACTICAL EXERCISES MANUAL0Unit ref.: FME-04Date: September 2013Pg: 21/25

A

00.10.2030.40.50.60.7

H(M 1/2)

Figure 2.13.1

The results obtained, in this type of typical laboratory equipment and with a

height of constant load, they are:

Ci, = 0.63

Cv = 0.996

Cc = 0.65 and the average value of the discharge coefficient, for a series of different load heights, is:

Cm = 0.63



These values agree enough with those that are registered in the specialized books. They are also consistent by themselves because the relation:

Cu = Cc Cv

is satisfied inside the acceptable error margins in the experimental process.



7.2.17 Observations of interest It is necessary to point out that there is not any theoretical value for the previous coefficients, since the determination of the load loss and of the contraction of the liquid vein can be only carried out experimentally. It is, also, necessary to indicate that the total loss of load is too small to be able to influence in an appreciable way in the decrement of the flowing flow. This decrement is, mainly, provoked by the contraction that suffers the liquid vein between the plane of the orifice and the contracted section. The expression Q = f (h) shows that, for values of h approximately between 150 mm and 350 mm, the discharge coefficient stays constant. This fact should be interpreted as a positive experimental result since, a priori; there is no reason to suppose it this way. Indeed, experiments carried out with a more extensive field of values of load heights and with orifices of sharp contour show certain variations in the value of C, especially when the size of the orifice and the load height are reduced.



7.2.18 Reflections and questions Q.1 If in the graphic representation of Q = Cu (h 1/2) the line that is obtained seems not to go by the origin, what possible reasons justify it? How will the value of C be affected?

Q.2 It has been supposed that the tank is big enough as to reject the arrival velocity from the current to the free surface of the liquid in the tank. Is this justified?

If the area of the traverse section of the tank is of 4,12 x 10 -2 m2 Which is the arrival velocity from the liquid to the free surface when the outlet flow through the orifice is 1,97 x 10 -4 m3/s?, to which kinetic height is it equivalent to?

Q.3 Supposing that it is not possible to measure the diameter of the contracted section, but that it is possible to measure the one of a section of the vein located at certain distance below it, estimate the effects of making this measure in a plane located 25 mm of the plane that contains the contracted section.

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Complete, with the results obtained, the following table for each one of themouthpieces given with the equipment.

Types of mouthpiece

Diaphragm

Colloidalnozzle

Venturi

Cylindrical

Diameter Section x 1 0-4 d (mm) (m2)

VolumeTime #FlowsCu(liters)t (s)x10-4

Table 2.15.1

C.4 Do these experiments confirm these theoretical statements?. Why?

C.5 For the same load height value that in the previous practical exercise, has the discharge coefficient (Cu) been improved with the incorporation of these mouthpieces? In which percentage? If there are discrepancies, what reasons can they be argued?

# Only in those experiments where the hydraulic Bench is used

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