MECH 322 Instrumentation
Lab 6 Fluid Speed and Volume Flow Rate
Performed: February 27, 2007
Group 0
Miles Greiner
Lab Instructors:
Mithun Gudipati, Venkata Venigalla
Abstract
• The volumetric flow rate and centerline speed of air in a
tube wind tunnel were measured for a range of blower
speeds. As a consistency check, the measured centerline
speed was compared to the centerline speeds calculated
from the volume flow rate based on slug and parabolic
velocity profiles.
• The volume flow rate and centerline speed were
determined by measuring the pressure from a Venturi tube
and a Pitot probe using pressure transmitters.
• The maximum volume flow rate was 0.062 ± 0.001 m3/s
• The measured centerline speed was bracketed by the
values predicted for slug and parabolic velocity for all
blower speeds.
Table 1 Atmospheric Conditions, Dimensions and
Parameters for Experiment
Tatm
Patm
Dpipe Dtube
Apipe
2
[°C] [mbar] [inch] [inch]
[m ]
22
873 2.07 2.25 0.002165
Atube
2
[m ]
0.002565
K
[-]
0.381
W 40-inch W 3-inch
[Pa]
25
[Pa]
1.9
• This table presents the atmospheric temperature and pressure
during the experiment.
• It also presents the pipe and tube inner diameters and areas,
and the Venturi tube flow coefficient.
• The manufacturer stated uncertainties of the pressure
transmitters are also included.
Table 2 Measured Pressure Transmitter Currents
Blower
Condition
Blower off
1
2
3
4
5
6
7
8
9
10
Blower off
IV
[mA]
4.01
8.9
8.59
8.33
7.74
7.15
6.74
6.39
6.09
5.59
5.09
4.02
IP
IG
[mA] [mA]
4.02
4
14.9
5
14.34 4.99
13.17 4.88
12.05 4.78
11.4 4.72
10.87 4.68
10.4 4.62
8.38 4.43
7.96
4.4
6.18 4.21
4.02 4.01
Table 3 Measurement Reading and Calculated Values
Blower
Condition
Blower off
1
2
3
4
5
6
7
8
9
10
Blower off
Uncertainty
PV
[Pa]
6.2
3048.3
2855.4
2693.7
2326.7
1959.6
1704.6
1486.8
1300.2
989.1
678.1
12.4
24.9
PP
[Pa]
0.9
508.6
482.4
427.8
375.6
345.3
320.5
298.6
204.4
184.8
101.7
0.9
1.9
PG
[Pa]
0
622
616
547
485
448
423
386
268
249
131
6
25
P
[kPa]
87.3
86.7
86.7
86.8
86.8
86.9
86.9
86.9
87.0
87.1
87.2
87.3
0.5
r
[kg/m3]
1.031
1.024
1.024
1.025
1.025
1.026
1.026
1.027
1.028
1.028
1.030
1.031
Wr
[kg/m3]
0.007
0.007
0.007
0.007
0.007
0.007
0.007
0.007
0.007
0.007
0.007
0.007
Q
[m3/s]
0.0029
0.0637
0.0616
0.0598
0.0556
0.0510
0.0475
0.0444
0.0415
0.0362
0.0299
0.0041
WQ
[m3/s]
0.0057
0.0013
0.0013
0.0012
0.0012
0.0011
0.0010
0.0010
0.0009
0.0009
0.0008
0.0041
VC
[m/s]
1.35
31.5
30.7
28.9
27.1
25.9
25
24.1
19.9
19
14.1
1.35
WVc
[m/s]
1.35
0.12
0.12
0.12
0.11
0.11
0.11
0.11
0.11
0.11
0.14
1.35
VP
[m/s]
2.2
49.6
48.0
46.6
43.3
39.7
37.1
34.6
32.3
28.2
23.3
3.2
VS
[m/s]
1.1
24.8
24.0
23.3
21.7
19.9
18.5
17.3
16.2
14.1
11.7
1.6
ReP
3,881
85,608
82,858
80,509
74,850
68,708
64,090
59,869
56,024
48,870
40,491
5,489
• This table presents the transmitter pressure differences for the Venturi tube, Pitot
probe and gage pressure for different flow conditions. The uncertainty of the
pressures is also included.
• The calculated tube absolute pressure, density, volume flow rate and centerline speed
are also presented.
• The uncertainty of the volume flow rate and speed are based on uncertainties of the
Venturi tube flow coefficient and pressure measurements.
• When the blower was on, the pipe Reynolds number is within or close to the
prescribed range for the Venturi tube calibration, 54,000 < 𝑅𝑒P < 137,000
Figure 1 Measured and Predicted Centerline Velocities
Versus Volume Flow Rate
• When the blower was on, the measured centerline speed was
between the values predicted for slug and parabolic velocity
profiles.
• The uncertainty in Q was more significant than that for VC