Theory: In this this exper xperim imen entt an orif orifce ce pl plat ate e owow-me mete terr is calibrated and the calculated coecient o discharge, Cd, is compared to the given value in the lab report as well as other published data. he orifce plate ow-meter provides a simple and low cost method or measuring the ow rate in a pipe using the pressure drop measurement across the plate. he orifce plate is a circular plate with a sharp s!uare edge hole in the center inserted in a pipe. "hen a uid is allowed to ow inside the pip pi pe, the the orif orifce ce pl plat ate e obst obstru ruct cts s the the ow ow whic which h results in uid pressure loss. # schematic diagram o an orifce plate installed in a pipe with ow rom let to right is shown in fgure $. he pressure loss is dependent on the orifce diameter, pipe diameter and the ow rate. %ence the ow rate is less than the theoretical ow rate which would occur i there were no losses.
Orifce meter #n orifce ifce meter eter is a di&er &erenti entia al press ssur ure e ow ow meter which reduces the ow area using an orifce plate late.. #n orifce ifce is a at at plate late with with a cent centra rall ll' ' drilled hole machined to a sharp edge. he orifce plate is inserted between two anges perpendicularl' to the ow, so that the ow passes through the hole with the sharp edge o the orifce pointing to the upstream. he relationship between ow ow rate rate and and pres pressu surre drop drop can can be dete deterrmine mined d using (ernoulli)s e!uation as: Qactual =Cd . Ao.
√[ ρ
2g 1
(∆ p ) A 2 )4 A 1
−(
]
where *actual + #ctual + volumetric ow rate ms Cd +ischarge co-ecient o orifce meter Ao= is the orifce cross sectional area
#$ +area at the inlet side in m / #/ +area at the throat side in m /
∆
0 +i&erential pressure head o li!uid in m
g +#cceleration due to gravit' 12.3$ ms /4 ρ
+ensit' o uid
Producers: $. he device is composed o tan5 flled with distilled water and reservoir is composed o pump and control panel. /. (eore start the device all the valves open to get rid o the bubbles and then close all valves except valve leading to the orifce. 6. urn the pump on and ad7ust the ow rate to a constant level using the valve on the tub. o ad7ust the ow rate or the rest o the lab, use the valve located on the orifce meter. his will avoid introducing air into the s'stem. 8. 9pen source o water and pra' the water valve to the tan5 being b' the rising tube. . 9pen the valve control 1valve ;ota meter4 on the ow o water to the c'linder ;ota meter.
<. =ote manometer flled with water b' the pump determine the level o change in height or determine the1h$,h/4 a di&erence 1 ∆ h4 >. ;epeat se several st steps to to ge get se several reading 1 ∆ h 4. 3. #ter the end o the experiment all the valves closed
Calculation: ?/+
√
2g 1
(
p 1 − p 2 γ
−⌊
)
D 2 ⌋ D 1
$. *act + <@@
?/+
√
2
∗9.81 ( 0.019 )
1
−⌊
0.02 0.035
+@.<8
⌋ 4
m sec
*ideal + #/A?/ #+
π 4
( D 2 ) 2
l hr
A
m
3
1000 l
A
1 hr 3600 sec
3
+ @.@@@$<
m sec
π
+
4
( 0.02 ) 2
+ @.@@$/<
m
2
*ideal + #/A?/ + @.@@$/
m sec
+ @.@@@3$6 Qact Qideal
Cd +
0.00016
+
0.000813
+ @.$2>
/. *act + 3@@
?/+
√
(
2∗9.81 0.042 1−⌊
0.02 0.035
)
⌋ 4
m sec
[email protected]<
*ideal + #/A?/ #+ +
π 4
π 4
( D 2 ) 2
( 0.02 ) 2
l hr
A
m
3
1000 l
A
1 hr 3600 sec
3
+ @.@@@//
m sec
m
+ @.@@$/<
2
*ideal + #/A?/ + @.@@$/
+ @.@@$/$
m sec
Qact Qideal
Cd +
0.00022
+
0.00121
+ @.$3/
6.
*act + $@@@ 3
m sec
@.@@@/> ?/+
√
(
2∗9.81 0.058 1− ⌊
0.02 0.035
+$.$/3
)
⌋ 4
m sec
*ideal + #/A?/
l hr
A
m
3
1000 l
A
1 hr 3600 sec
+
π
#+ +
4
π 4
( D 2 ) 2
( 0.02 ) 2
+ @.@@$/<
m
2
*ideal + #/A?/ + @.@@$/
m sec
+ @.@@$8/ Qact Qideal
Cd +
0.00027
+
0.00142
+ @.$2
8-*act + $/@@
?/+
√
(
2∗9.81 0.08 1− ⌊
0.02 0.035
+$.6/
m sec
⌋
)
l hr
A
m
3
1000 l
A
1 hr 3600 sec
3
+ @.@@@66
m sec
*ideal + #/A?/ #+
π 4
+
( D 2 ) 2
π 4
( 0.02 ) 2
m
+ @.@@$/<
2
*ideal + #/A?/ + @.@@$/
+ @.@@$<>
m sec
Qact Qideal
Cd +
0.00033
+
0.00167
+ @.$23 . *act + $8@@
?/+
√
(
∗
2 9.81 0.11 1
−⌊
0.02 0.035
+$.8
)
⌋ 4
m sec
l hr
A
m
3
1000 l
A
1 hr 3600 sec
3
+ @.@@@63
m sec
*ideal + #/A?/ π
#+ +
4
π 4
( D 2 ) 2
( 0.02 ) 2
+ @.@@$/<
m
2
*ideal + #/A?/ + @.@@$/
+ @.@@$2< Cd +
m sec
Qact Qideal
0.00038
+
0.00196
+ @.$28
Cd
V2 m sec
Qideal 3
m sec
∆h m
∆h Qact mm m 3
sec
Qact l hr
@.$2 @.<8 >
@.@@@3 @.@$ $2 @.@@@$ <@@ $6 2 <
@.$3 @.2< /
@.@@$/ @.@8 8/ @.@@@/ 3@@ $ / /
@. $ 2 $. $ / 3
@.@@$8 @.@ 3 @.@@@/ $@@ / 3 > @
@.$2 $.6/ 3
@.@@$< @.@3 >
3@ @.@@@6 $/@ 6 @
@.$2 $. 8 8
@.@@$2 @.$$ <
$$ @.@@@6 $8@ @ 3 @
Discussion:
$-In engineering practice, it is rarel' possible to measure the rate o ow o a uid b' a direct volumetric or gravimetric determination. Bre!uentl', the metering is accomplished b' the observation o some measurable !uantit' related to the rate o discharge. discharge. 9rifces, noles, 0itot and orifce meter tubes produce a di&erential pressure related to the ow velocit'. he di&erential pressure can be measured with a manometer, pressure gage, or pressure pressure sensor. sensor. 0ressure sensors are widel' used because the' provide a voltage output that can be monitored easil' b' computer.
/- #ter an experience we noticed several errors in the readings due to lac5 o bubbles out completel'. In order to correct the piece must ta5e out all the bubbles rom the pipeline ;ota meter b' pressure on the tube and then we pressing the pump to see the di&erence between 1h$, h/4
(ut i orifce meter diagonall' ma' di&er rom the usual orifce meter and the piece because the angle changed. 6- o calculate theoretical discharge rate through through orifce meter 1*t4 and to measure actual ow rate ra te 1*a4 1*a 4 through orifce meter. meter.o o determine determine the value o coecient o discharge Cd.
8- #lso, there ma' be a slight di&erence di&erence between *act and *ideal teams called this rate errors rate error error =
Qideal −Qact Qact
#n error rate as a result o the mista5es o the process which ma' be the result o not controlling controlling the read *; or not to calculate the exact time when the c'linder with water movement. #nd too5 man' di&erent di&erent read and *;Ds and get di&erent results.
iagram:
$/
$@
3
∆h
<
8
/
@ @
/
8
< Qact
3
$@
$/
