CEBU INSTITUTE OF TECHNOLOGY
N. Bacalso Avenue, Cebu City
Chemical Engineeing Department
FINAL REPORT
ChE Lab 1
Title of Experiment
Juphil A. Lamanilao
BSChE-5
Engr. Lyda P. Abellanosa
Instructor
Abstract:
Controlling the flow in piping systems is a significant issue in the chemical
process industries. Obviously, in order to control the flow in a pipe, the flow must be
measured. This experiment will introduce you to two devices that are used to measure
flow. One, the venturi meter, is a device used for measuring the rate of flow of a fluid
through a pipe. Water is allowed to flow through the meter at different rates ranging
from zero to the maximum and the corresponding pressure differences shown in the
manometer are noted. The actual discharge is determined using the measuring tank and
the stop watch. The second, the orifice meter, is a device used for measuring the rate of
flow of a fluid through a pipe. It works on the same principle as a venturi meter. It
consists of a flat circular plate which has a circular sharp edged hole called orifice,
which is concentric with the pipe. The orifice diameter is 0.5 times the diameter of the
pipe. A differential manometer is connected at section 1 which is at a distance of about
1.5 to 2 times the pipe diameter upstream from the orifice plate, and at section 2, which
is at a distance of about half the diameter of the orifice on the downstream side from the
orifice plate. It can be set up to be read locally or remotely using pressure transducers.
Both are designed for flows that do not contain significant amounts of solid material.
Objectives:
1.) To plot the coefficient of discharge of a sharp – orifice versus Reynold’s number
2.) To plot the coefficient of discharge of a venture versus Reynold’s number.
3.) To obtain data on pressure drop versus water flow rate.
Materials & Equipment:
Hydraulic bench apparatus, orifice meter, venture meter, graduated cylinder, stopwatch,
manometer, water, ruler
Sketch of the Set-up:
Procedure:
A. The inlet head tank was positioned on the mounting studs provided on the bench working
surface so that the orifice set discharges into the weir channel. The inlet hose was attached
from the bench regulating valve to the inlet of P6103. From here, the overflow pipe was
connected to the overflow of the bench measuring tank. The orifice is screwed under test
into the side outlet position or the base outlet as required. Required heads were obtained by
maintaining a small but constant overflow. Flow from the orifice was derived by measuring
the time taken to fill the measuring tank between predetermined levels. Readings were
taken from the provided manometer at a convenient time interval.
B. The procedure above was repeated using venture meter instead of orifice.
Tabulated Data & Result:
Orifice:
TRIAL
1
2
3
4
5
6
7
8
9
10
TRIAL
1
2
3
4
5
6
7
8
9
10
Manometer Reading (mm)
Upstream Downstream
43
2
47.7
2.5
50.7
4.1
52.6
7.3
64
14.5
69.5
18.5
74.5
21.5
82
25.5
88.5
3.
97
31.75
Rm
41
45.2
46.6
45.3
49.5
51
53
56.5
58.5
65.25
Manometer Reading (mm)
Upstream Throat
Downstream
15.5
3
15.5
18.5
6
18.5
22
9.5
22
29.5
15
29.5
33.5
20
33.5
36.5
23
36.5
42.5
28.25
42.5
47
32
47
51.5
36
51.5
63
46
63
Volumeteric
Flow Rate
313.03
345.63
346.15
346.57
347.46
349.77
350
352.38
369.81
381.46
Rm
12.3
12.5
12.5
13.3
13.5
13.5
14.25
15
15.5
17
Co
NRE
2.119
2.228
2.198
2.232
2.1405
2.123
2.084
2.032
2.096
2.047
31204.66
34454.422
34506.263
34548.13
34636.85
34867.12
34890.05
35127.302
36864.83
38026.17
Volumeteric
Flow Rate
324.34
342.35
347.95
348.17
353.17
359.65
372.68
390.34
393.91
430.18
Co
NRE
3.97
4.197
4.266
4.138
4.166
4.2426
4.279
4.368
4.337
4.522
32332.11
34127.45
34685.69
34707.62
35206.05
35852.02
37150.92
38911.38
39267.25
42882.86
Computations:
where:
Do = 14.25 mm = 0.01425 m
Di = 28.5 mm = 0.0285 m
pH2O = 997.08 kg/m3
A = [3.1416(0.01425)2]/4
dP = pg(Rm)
Rm = upstream – downstream (manometric reading)
Vo = Q/A
Orifice:
Trial 1:
Rm = 43 mm – 2mm =41 mm
= 0.041 m
Vo = (313.03 ml/s x 1/1x106)
1.594849x10-4 m2
= 1.9628 m/s
dP = 997.08 kg/m3 (9.81
m/s)(0.041 m)
= 401.36 Pa
from the formula above:
Co = 2.119
Venturi: (same eqn. used above)
Trial 3:
Rm = 0.0466 m
Vo = (346.15 ml/s x 1/1x106)
1.594849x10-4 m2
= 2.1704 m/s
dP = 997.08 kg/m3 (9.81
m/s)(0.0466 m)
= 455.811 Pa
from the formula above:
Co = 2.198
Trial 2:
Rm = 0.0452 m
Vo = (345.63 ml/s x 1/1x106)
1.594849x10-4 m2
= 2.167 m/s
dP = 997.08 kg/m3 (9.81
m/s)(0.0452 m)
= 442.117 Pa
from the formula above:
Co = 2.228
40000
35000
30000
25000
Re
y = 2E+06x 3 - 1E+07x 2 + 2E+07x - 2E+07
20000
15000
10000
5000
0
2
2.05
2.1
2.15
2.2
2.25
Co
Fig.1.1 shows the diagram of Re vs. Co for Orifice
50000
45000
40000
35000
30000
25000
20000
15000
y = -28409x 3 + 384563x 2 - 2E+06x + 3E+06
10000
5000
0
3.9
4
4.1
4.2
4.3
4.4
Fig.1.2 shows the diagram of Re vs. Co for Venturi
4.5
4.6
Data Analysis :
Based on the graph plotted above, the calibration of venturimeter is more
accurate when measuring the rate of flow of a fluid through a pipe than an orifice
meter. Care was handled with the reading of the manometer because only slight
changes occur; a keen eye from the group member was needed. Several parameters
were significant and recorded including the manometer readings in order to compute
for the discharge coefficients.
Recommendation:
From the experiment, one main causes of error is due to the presence of bubbles
within the hose and is assumed by the experimenter to be negligible. It really makes a
big difference with respect to the rate of flow. Also, the orifice meter cannot measure
directly the vertical displacement of the water stream at its varying distances.
Application to ChE:
Basically in industries, they are used for measuring the flow rate of chemicals
through pipe. Both flowmeter is often used in applications where it's necessary with
higher TurnDown Rates, or lower pressure drops. The Venturi meter which has long
been used in hydraulics is applied to the measurement of volume flow of blood through
vessels. One method is by inserting an accurately calibrated Venturi meter made of
glass into the circulation. This method requires an anticoagulant, but is accurate and
sensitive to slight changes in flow. Another method is to produce a constriction in a
vessel by means of a ligature near a branch, which can be used as a side tube, thus
transforming the vessel itself into a Venturi meter. The latter method is subject to
greater error in calibration for absolute flows, but is sensitive for estimating slight
changes in the rate of flow and does not require the use of an anticoagulant. They are
also popular for automatic batching applications.