Calibration of Venturi Meter

8/9/2019 Calibration of Venturi Meter

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Expt No:

Date :

DETERMINATION OF COEFFICIENT OF DISCHARGE AND

CALIBRATION OF VENTURI METER

AIM

i) To find the co-efficient of discharge

ii) To calibrate the given venturimeter.

iii) To plot the graphs Cd Vs ! log "a Vs log and "a Vs #calibration curve)

APPARATUS

$pparatus consists of a closed circuit pipe arrangement connected %ith an venture meter.$ centrifugal pump is used to suppl& %ater! the flo% rate can be varied b& ad'usting the valve

fitted to the suppl& pipe. $ (-tube manometer is used for measuring the pressure difference

bet%een the inlet and the 'ust outlet of the venturimeter. $ measuring tan having dimensions

*+cm , +cm! fitted %ith a pieometer is used to measure the actual discharge through the

t t


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venture meter

The theoretical discharge for a venturi is given b& the e0uation

1 2

2 2

1 2

. 2th

A A gH Q

A A=

−m3s

4here $1 is the area of the pipe! $2 is the area at the venture throat! the head causing

flo%! and g the acceleration due to gravit&.

The above e0uation is applicable for incompressible frictionless flo% onl&. /n order to

account for the frictional and other losses! a discharge coefficient! Cd must be introduced in the

above e0uation to get the actual discharge

Therefore

a

d

th

Q C =

Q

The actual discharge "a is measured b& experiment and hence Cd can be calculated.

The calibration e0uation is given b&n

aQ = KH

! %here 5 and n are constants and is the

manometer reading.

PROCEDURE

1) 6 h f l i ll h d li l


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I. Determinti!n !" #!e""i#ient !" $i%#&r'e

Coefficient of discharge!

a

d

th

Q C =

Q

4here "a is the actual discharge in cm3sec

"th is the theoritical discharge in cm3sec

I.) C#ti!n !" A#t Di%#&r'e *

$ctual discharge is measured using a collecting tan.

"a < #$ = x)3t cm3s

$rea of the collecting tan! $ < cm2

ise of %ater in the collecting tan! x < cm

Time for 8cm of rise of %ater level

in the collecting tan! t < s

$ctual discharge! #$ = x)3t < cm3s.


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Cross sectional area at the inlet of the venturimeter!$

2

11

π * d =

4 cm2

Cross sectional area at the inlet of the venturimeter!1$ <

1$ <

cm2

Cross sectional area at the throat of the venturimeter!

2

2

2

π * d A =

4 cm2

Cross sectional area at the throat of the venturimeter! 2$ <

cm2

2$ <

c m2

I./1)C#ti!n !" He$ C%in' F!2

ead-causing flo% is measured using a (- tube manometer.

1

2

>eft side reading of the (- tube manometer! h < cm of mercur&

:ight side reading of the (- tube manometer! h < cm of mercur&

m 2 1h = h - h cm of Hg


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Theoretical Discharge! "th

1 2

2 2

1 2

. 2th

A A gH Q

A A=

− cm

3s

T&e!reti# $i%#&r'e+ *t& , #m-

%.

T&ere"!re+

C!e""i#ient !" Di%#&r'e

Coefficient of discharge!

a

d

th

Q C =

Q

<

T&ere"!re+ C!e""i#ient !" $i%#&r'e+ C$ ,

II) Ci/rti!n !" 0entrimeter

The calibration e0uation of the venturimeter is discharge!n

aQ = KH

.

4here K and n are constants for the venturimeter.

H i th h d i fl i ti t f t


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1. T&e 'i0en 0entrimeter i% #i/rte$

-. T&e 'r4&% C$ V% H+ !' * V% !' H n$ * V% H (#i/rti!n #r0e) re 4!tte$.

INFERENCE


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*) Can %e use an inverted (-tube manometer /f so! ho% %ill &ou determine Cd

8) 4hat changes in the formula %ill be re0uired if the venturimeter is vertical

9) 4hat are the advantages and disadvantages of a venturimeter over an orificemeter


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O/%er0ti!n% n$ T/r C!mn

Diameter at the inlet d1


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5 < $ntilog #log 5) < $ntilog #log ---------) <

n is slop of the graph log " a Vs log < &3x <

therefore! $ctual discharge! Qa= K H n

Ci/rti!n t/e

ead in cm of

%ater

$ctual

discharge"a

Documents

Calibration of Venturi Meter