Calibration of Venturi and Orifice Meters

1. CALIBRATION OF VENTURI AND ORIFICE METERS
ELECCION, NICELY JANE R.
Department of Chemical Engineering
College of Engineering and Architecture
Cebu Institute of Technology – University
N. Bacalso Ave., Cebu City 6000
This experiment aims to calibrate both venturi and orifice apparatus. This can be done
by plotting the coefficient of discharge of a sharp orifice against Reynolds number as well
as the coefficient of discharge of a venturi against the corresponding calculated Reynolds
number. The pressure drop is also plotted against the water flow rate. In order to calibrate
flow meters specifically the venturi and orifice flow meters, a known volume of fluid is
used to pass to measure the rate of flow of the fluid through the pipe. Venturi meters
consist of a vena contracta-shaped, short length pipe which fits into a normal pipe line.
Orifice meters, on the other hand, consists of a flat plate with flanges and is placed at the
middle of the pipe and behaves similarly to a venturi meter. Since it follows the Bernoulli’s
Principle, when Reynolds number is decreased, the coefficient discharge of a venturi flow
meter increases as well as in the orifice meter. The increase in the pressure drop vs
volumetric flow rate in an orifice is greater than in the venturi flow meter. Pressure losses
in an orifice, though, is approximately twice than that of a venturi.

2. 1. Introduction
Both venturi and orifice meters are two typical head meters commonly used to
measure flow rates. Evident in their design, a pressure difference occurs between the
upstream and downstream sides of the apparatus which is caused by the constriction
that changes the pressure head partly into the velocity heads.
First, a venturi meter consists of three parts: a short converging part, a throat and
a diverging part. The converging part is where friction has a negligible effect on the
upstream side while the diverging part is made as smooth and as tapering as possible
to eliminate drag and friction.
Orifice meter, on the other hand, consists of flat circular plate which has a circular
hole, in concentric with the pipe. The sharp-edge holes are usually situated with
respect to the upstream and it resembles a squat frustum of a cone when seen in
cross-section. It is usually cheaper compared to a venturi meter; however, it is
inconvenient in a way that the permanent head loss is always accounted due to friction
at the constriction.
Both devices follows a similar approach which is the Bernoulli’s Principle given in
the equation for incompressible and compressible fluid flow.

3. 2. Materials and Methods
2.1 Equipment and Materials
 Hydraulic bench apparatus
 Venturi and Orifice Meter
 Stopwatch
 Manometer
 Water
 Caliper
2.2 Methods
All materials and apparatus were checked and prepared prior to the experiment
started. All materials and apparatus were also cleaned appropriately. For the
calibration of venture meter/ orifice meter apparatus, the venturi or orifice meter
apparatus was set up. The pump was started and the main regulating flow valve was
opened to fix the water flow rate. The tubes from the venture or orifice pressure
tapping points to the manometer (mouth or inlet tap point and throat tap point) were
connected. It was ensured that there is no trapped air in the connecting lines. Ample
time was allowed to stabilize the flow before readings were taken. The upstream and
downstream of the manometer were read and recorded. The diameter of the
cylindrical cross-section of the tapping points of the venture or orifice apparatus was
recorded. The theoretical volumetric flow rate was computed. For any reading of the
manometer, the volume discharged was collected at the outlet and the time to collect
the volume discharged at the outlet was measured using a graduated cylinder. The
volume collected and the time was recorded. The actual volumetric flow rate from the
volume collected divided by the time obtained was computed. Several trials were
taken by adjusting the main flow regulating valve. All the data were recorded and the
coefficient of discharge of the Venturi and Orifice apparatus and their Reynolds
Number were computed respectively.

4. 3. Results
Table 3.1 Tabulated Data and Results of Venturi Meter
Trial
ΔP (cm
H2O)
ΔP
(N/m2
)
Volume
(m3
)
Time
(s)
Qactual
(m3
/s)
Qtheo (m3
/s) C NRe
1 8.5 831.10 1x10-3
9.3 2.812x10-4
2.126 x10-4
1.324 27775.01
2 9.0 879.99 1x10-3
6.43 2.560 x10-4
2.188 x10-4
1.170 25285.82
3 9.9 967.32 1x10-3
6.37 2.092 x10-4
2.294 x10-4
0.912 17883.98
4 10.2 997.32 1x10-3
5.44 1.910 x10-4
2.329 x10-4
0.820 18858.02
5 10.3 1007.10 1x10-3
5.37 1.862 x10-4
2.340 x10-4
0.796 18385.39
6 11.4 1114.65 1x10-3
5.21 1.919 x10-4
2.462 x10-4
0.779 20212.90
7 14.8 1447.00 1x10-3
5.03 1.988 x10-4
2.805 x10-4
0.708 19629.99
Figure 3.1. Graph of Coefficient of discharge against Reynolds Number in a
Venturi Meter
0
5000
10000
15000
20000
25000
30000
0 0.2 0.4 0.6 0.8 1 1.2 1.4
ReynoldsNumber
Coefficient of Discharge
Reynolds Number vs C in a Venturimeter

5. Table 3.2 Tabulated Data and Results of Orifice Meter
Trial
ΔP (cm
H2O)
ΔP
(N/m2
)
Volume
(m3
)
Time
(s)
Qactual
(m3
/s)
Qtheo (m3
/s) C NRe
1 2.5 244.44 1x10-3
6.6 1.515x10-4
1.241 x10-4
1.221 14448.17
2 2.9 283.55 1x10-3
6.2 1.613 x10-4
1.337 x10-4
1.206 15393.99
3 5.0 488.88 1x10-3
6.03 1.658 x10-4
1.756 x10-4
0.949 15817.97
4 6.9 674.66 1x10-3
6.00 1.667 x10-4
2.063 x10-4
0.808 15899.51
5 8.3 811.55 1x10-3
5.89 1.698 x10-4
2.262 x10-4
0.751 16209.35
6 10.3 1007.10 1x10-3
5.32 1.880 x10-4
2.520 x10-4
0.746 17937.91
7 12.1 1183.10 1x10-3
5.00 2.000 x10-4
2.731 x10-4
0.732 26058.89
Figure 3.2. Graph of Coefficient of Discharge against Reynolds Number in and
Orifice Meter
0
5000
10000
15000
20000
25000
30000
0 0.2 0.4 0.6 0.8 1 1.2 1.4
ReynoldsNumber
Coefficient of Discharge
Reynolds vs C in an Orifice Meter
Reynolds vs C
Linear (Reynolds vs C)

6. Figure 3.3 Graph of Pressure Drop against Flow Rate for both Venturi and
Orifice Meter
4. Calculations
For Venturi Meter
D1=28.5X10-3 m -outer
D2=14.25x10-3 m - inner; A2=
𝜋(14.25𝑥10−3)2
4
= 1.595𝑥10−4
𝑚2
;
ρH2O=998.0 kg/m3
μ=9.027x10-4 Pa.s
𝑸𝒕𝒉𝒆𝒐 =
𝑨 𝟐 √
𝟐𝜟𝑷
𝝆
√𝟏− (
𝑫 𝟐
𝑫 𝟏
) 𝟒
𝑄𝑡ℎ𝑒𝑜1 =
1.595𝑥1010−4 𝑚2√
2(831.10
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
= 2.126x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜2 =
1.595𝑥1010−4 𝑚2√
2(879.99
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
= 2.188x10−4 𝑚3
𝑠
0
200
400
600
800
1000
1200
1400
1600
0 2 4 6 8
PressureDrop
Flow Rate
Pressure Drop Against Flow Rate
Orifice
Venturi

7. 𝑄𝑡ℎ𝑒𝑜3 =
1.595𝑥1010−4 𝑚2√
2(967.99
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
= 2.294x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜4 =
1.595𝑥1010−4 𝑚2√
2(997.32
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
= 2.329x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜5 =
1.595𝑥1010−4 𝑚2√
2(1007.10
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
=2.340 x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜6 =
1.595𝑥1010−4 𝑚2√
2(1114.65
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
= 2.462x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜7 =
1.595𝑥1010−4 𝑚2√
2(1447.09
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
=2.805 x10−4 𝑚3
𝑠
Ѵfinal=
𝑸 𝒂𝒄𝒕𝒖𝒂𝒍
𝑨 𝟐
; Ѵ=velocity
Ѵ1=
2.812𝑥10−4 𝑚3
𝑠
1.595𝑥1010−4 𝑚2 =1.763
𝑚
𝑠
Ѵ2=
2.56𝑥10−4 𝑚3
𝑠
1.595𝑥1010−4 𝑚2
=1.605
𝑚
𝑠
Ѵ3=
2.09210−4 𝑚3
𝑠
1.595𝑥1010−4 𝑚2
=1.312
𝑚
𝑠
Ѵ4=
1.91𝑥10−4 𝑚3
𝑠
1.595𝑥1010−4 𝑚2 =1.197
𝑚
𝑠
Ѵ5=
1.862𝑥10−4 𝑚3
𝑠
1.595𝑥1010−4 𝑚2
=1.167
𝑚
𝑠
Ѵ6=
1.919𝑥10−4 𝑚3
𝑠
1.595𝑥1010−4 𝑚2
=1.203
𝑚
𝑠

8. Ѵ7=
11.988𝑥1.10−4 𝑚3
𝑠
1.595𝑥1010−4 𝑚2
=1.246
𝑚
𝑠
For Orifice Meter
D1=28.5X10-3 m - outer
D2=14.75x10-3 m - inner; A2=
𝜋(14.75𝑥10−3)2
4
= 1.709𝑥10−4
𝑚2
;
ρH2O=998.0 kg/m3
μ=9.027x10-4 Pa.
𝑸𝒕𝒉𝒆𝒐 =
𝑨 𝟐 √
𝟐𝜟𝑷
𝝆
√𝟏− (
𝑫 𝟐
𝑫 𝟏
) 𝟒
𝑄𝑡ℎ𝑒𝑜1 =
1.709𝑥1010−4 𝑚2√
2(244.44
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
=
1.241x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜2 =
1.709𝑥1010−4 𝑚2√
2(283.55
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
=
1.337x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜3 =
1.709𝑥1010−4 𝑚2√
2(488.88
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
=
1.756x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜4 =
1.709𝑥1010−4 𝑚2√
2(674.66
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
=
2.063x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜5 =
1.709𝑥1010−4 𝑚2√
2(811.55
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
=
2.262x10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜6 =
1.709𝑥1010−4 𝑚2√
2(1007.10
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
=2.520x
10−4 𝑚3
𝑠
𝑄𝑡ℎ𝑒𝑜7 =
1.709𝑥1010−4 𝑚2√
2(1183.10
𝑁
𝑚2)
𝜌
√1− (
14.75𝑥10−3 𝑚
28.5𝑋10−3 𝑚
)4
=2.731x
10−4 𝑚3
𝑠

9. Ѵfinal=
𝑸 𝒂𝒄𝒕𝒖𝒂𝒍
𝑨 𝟐
; Ѵ=velocity
Ѵ1=
1.515𝑥10−4 𝑚3
𝑠
1.709𝑥1010−4 𝑚2
=0.886
𝑚
𝑠
Ѵ2=
1.613 x10−4
𝑚3
𝑠
1.709𝑥1010−4 𝑚2 =0.944
𝑚
𝑠
Ѵ3=
1.658 x10−4
𝑚3
𝑠
1.709𝑥1010−4 𝑚2
=0.970
𝑚
𝑠
Ѵ4=
1.667 x10−4
𝑚3
𝑠
1.709𝑥1010−4 𝑚2
=0.975
𝑚
𝑠
Ѵ5=
1.698 x10−4
𝑚3
𝑠
1.709𝑥1010−4 𝑚2
=0.994
𝑚
𝑠
Ѵ6=
1.880 x10−4
𝑚3
𝑠
1.709𝑥1010−4 𝑚2
=1.100
𝑚
𝑠
Ѵ7=
2.000 𝑥10−4
𝑚3
𝑠
1.709𝑥1010−4 𝑚2 =1.598
𝑚
𝑠

10. 5. Sketch

11. 6. Discussion
In an orifice plate, there is restriction in the flow, thereby causing a pressure drop
which is related to the volumetric flow based on Bernoulli’s equation. Orifice plates
results to high energy and pressure loss with respect to the flow being measured.
Venturi meter, on the other hand, is also based on Bernoulli’s principle just like the
orifice plate. Instead of sudden constriction caused by an orifice, venturi meter uses a
relatively gradual constriction similar to a reducer to cause the pressure drop by
increasing velocity of the fluid. The volumetric flow is proportional to the square root
of this pressure drop and venture meter can be calibrated accordingly. For the orifice
meter, if viscosity is higher, Reynolds number is lower and a higher flow rate for the
same pressure difference in front of and after the orifice leads to a higher coefficient
of discharge. The discharge coefficient in a venture meter varies noticeably at low
values of the Reynolds.
The probable sources of error in the result hereby conducted are the bubbles that
may have appeared in the hose. Another is in reading the measurements and some
human errors.
7. Conclusion
This experiment aims to calibrate the venture and orifice flow meters by letting a
known volume of water pass through and reading the pressure change from a
manometer. The data gathered in the venturi is more accurate as seen in the graph
which shows how the data fits in the regression line. When Reynolds number is
decreased, the coefficient discharge of a venturi flow meter increases. The increase in
the pressure drop vs volumetric flow rate in an orifice is greater than in the venturi flow
meter. Pressure losses in an orifice, though, is approximately twice than that of a
venturi.

12. 8. Recommendation
In this experiment, it is best to make sure that no bubbles appear in the hose
and accurate reading of the pressure in the manometer must thereby constituted. A
functional apparatus must also be ensured in order to arrive to accurate results.
9. References
[1] Geankoplis, C.J. (2009) Principles of Transport Processes and Separation
Processes. 1st edition. Pearson Education South Asia PTE. LTD.
10.Web References
[1] Orifice Meter. Retrieved March 10, 2018, from
http://www.nptel.ac.in/courses/112104118/lecture-15/15-3_orificemetr.htm
[2] What is the difference between venturimeter and orificemeter? (n.d.). Retrieved
March 10, 2018, from https://www.quora.com/What-is-the-difference-between-
venturimeter-and-orificemeter