Orifice Mouthpiece Manual

8/11/2019 Orifice Mouthpiece Manual

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______________________________________________________________________________________

INSTRUCTION MANUAL

for

ORIFICE & MOUTHPIECE

SET UP

OBJECTIVE:

To study the flow of liquid through orifice & mouthpiece

AIM:

To determine the co-efficient of discharge. (Cd)

To determine the coefficient of Velocity. (Cv)To determine the coefficient of Contraction (Cc)

INTRODUCTION:

An orifice is an opening or hole of any size, shape or form, through which liquid flow such that its

upper edge remains below the free surface of the liquid. Orifices are used for measurement or control offlow. Orifices may have any shape but generally they are circular, square or rectangular.

A mouthpiece is a relatively short pipe, which is fitted internally or externally to the orifice in theside of the tank. Mouthpieces are sometimes used as a flow measurement device.

THEORY:

ORIFICE :

When a liquid flows from a vessel or a tank through an orifice it changes its direction. Due to this

change of direction of the liquid the jet is acted upon by lateral or side forces, which gradually reduces its

area up to certain section. This area does not reduce further beyond which the jet ceases & streamlines, firstbecomes parallel is known as vena-contracta.


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MOUTHPIECE:

A short piece of length about three times of its diameter, connected to the face of an orifice is known

as a mouthpiece. In what follows, it will be proved that under a given head, the rate of discharge through a

mouthpiece will be more than that through orifice of the same diameter. The reason being that whileentering into the mouthpiece, the liquid gets contracted at vena-contracta. Due to this contraction the

velocity of the liquid increase and the pressure decreases. The pressure at vena-contracta is less than at

atmosphere. This may be verified by applying the Bernoullis theorem at the vena-contracta.

COEFFICIENT OF VELOCITY:

It is defined as the ratio between the actual velocity of a jet of liquid at a vena-contracta & thetheoretical velocity of the Jet. It is denoted by Cv andthe ratio of Cv isgiven as:

Cv = Actual velocity of the Jet at Vena-contracta

Theoretical Velocity

= V

2gH

COEFFICIENT OF DISCHARGE:

It is defined as the ratio of the actual discharge through the orifice to the theoretical discharge from

the orifice. It is denoted by Cd. If Qathe actual discharge and Qtis the theoretical discharge then ratio of Cdis given as:

Cd = QaQt

DESCRIPTION:

It consists of a constant head tank that supplies the water to the orifice and mouthpiece. It has a

piezometer with scale for head measurement. A measuring arrangement for X Y Co-ordinates of vena-

contracta is provided. Discharge is measured in measuring tank with the help of a stop watch. Water iscirculated from the sump tank through the centrifugal pump.

PROCEDURE:

1. Clean the apparatus and make All Tanks free from Dust.

2. Close the drain valves provided.

3. Fill Sump tank with Clean Water and ensure that no foreign particles are there.4.

Close all Flow Control Valves given on the water line.

5. Open By-pass valve.

6. Fix the desired test piece at the testing section.


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7. Ensure that On/Off Switch given on the Panel is at off position.

8. Now switch on the Main Power Supply (220 Volts AC, 50 Hz).9. Switch on the Pump.

10. Operate the Flow Control Valve to regulate the flow of water in variable head tank.

11. Adjust the head of water in the tank with the help of given flexible varying head system.

12.

Now fix the pointer gauge at Vienna observed in water stream coming out of the tank.13. Record the head of the Water in the tank.

14. Record pointer gauge reading.

15. Measure the flow of water, discharge through desired test section using stop watch and

Measuring Tank.16. Repeat the same procedure for different water heads.

17. When experiment is over for one desired test piece, open the By-pass Valve fully then close the

flow control valve.18. Drain the variable head tank in the sump tank by means of given drain valve.

19.

Change the test piece.20. Switch off Pump.

21. Switch off Power Supply to Panel.

FORMULAE:

Cv = V = x

2gH 4yH

Actual discharge (Qa):

Qa = A x R

t

Theoretical Discharge (Qt) :

Qt = area of orifice/mouthpiece x 2 g H

Co- efficient of discharge (Cd):

t

a

d

Q

QC =

Co- efficient of Contraction (Cc):

v

d

cC

CC =

OBSERVATION & CALCULATIONS:


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DATA:

1. Dia of the Orifice = 10 mm & 15 mm = 0.01 m & 0.15 m

2. Length of Orifice = 10 mm = 0.01 m

3. Area of Orificed

2

= 7.854 x 10

-5

m

2

& 1.767 x 10

-4

m

2

4

4. Dia of Mouth piece = 10 mm, 15mm

5. Length of Mouthpiece = 10 mm, 25 mm6. Area of Mouthpiece d2 = 7.854 x 10-5m2

4

7. Area of the Measuring tank (A) = 0.1 m2

OBSERVATION TABLE:

S. No.

Water Head

(cm) x (cm) y (cm)

Rise of Water

Level R (cm)

Time taken

for R, t

(sec)

1

2

3

CALCULATION TABLE:

S.

No. H (cm) x (cm) y (cm) Qa, (m3/s) Qt, (m

3/s) Cv Cd

1

2

3


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NOMENCLATURE:

V = Actual velocity at vena-contracta.

2gh = Theoretical velocity (m/sec)

R = Rise of water level in measuring tank (cm)

t = Time taken to R (sec)

H = Water Head

x = Horizontal distance traveled by the liquid particle from the vena-contracta.

y = Vertical distance between vena-contracta & liquid particle.

PRECAUTION & MAINTENANCE INSTRUCTIONS:

1. Do not run the pump at low voltage i.e. less than 180 Volts.2. Never fully close the Delivery line and By-Pass line Valves simultaneously.

3.

Always keep apparatus free from dust.4. To prevent closing of moving parts, Run Pump at least once in a fortnight.

5. Frequently Grease/oil the rotating parts, once in three months.6. Always use clean water.

7. It apparatus will not in use for more than one month, drain the apparatus completely.

TROUBLE SHOOTINGS:

1. It pump gets jam, open the back cover of pump and rotate the shaft manually.2. If pump gets heat up, switch off the main power for 15 minutes and avoid closing.

3. The flow control valve and by pass valve simultaneously during operation.

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Orifice Mouthpiece Manual