ME 391
Instrumentation
LAB #6
Volume Flow Rate and Centerline Speed in a
Tube Wind Tunnel
Performed: 03/05/2004
Soma: I believe I performed 50% of this lab.
(Participation: __/50)
Sinan Ozcan: I believe I performed 50% of this lab.
(Participation: __/50)
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 centerline
speed for each flow rate was compared to the
centerlines speed 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 0.077 + 0.002
m3/s.
• The measured centerline speed was bracketed by the
values predicted for slug and parabolic velocity for all
blower speeds.
Table 1
Atmospheric Pressure and
Temperature Readings
Tatm
Patm
[°C] [hPa]
23
860
Dpipe
[inch]
2.067
Dtube
Apipe
Atube
[inch]
[m2]
[m2]
2.25 0.002165 0.002565
K
[1]
0.381
W40-inch W4-inch
[Pa]
2.5
[Pa]
0.25
• This table presents the atmospheric temperature and
pressure during the experiment.
• It also presents the pipe and tube inner diameters and
areas, and the flow coefficient for the venturi tube.
• The manufacture stated uncertainties of the pressure
transmitters are also included.
Table 2
Measurement Readings and Calculated Values
Flow Condition
Blower Off
1 Fully Open
2
3
4
5
6
7 Fully Closed
Pressure
Uncertainty
IV
[mA]
4
11.08
10.88
10.36
9.82
9.45
8.98
4.16
PV
[Pa]
0.0
4410.4
4285.8
3961.9
3625.5
3395.0
3102.2
99.7
2.5
IP
[mA]
4
20.90
20.40
19.57
18.28
17.73
16.12
4.22
PP
[Pa]
0.00
1052.76
1021.61
969.91
889.55
855.29
755.00
13.70
0.25
IG
[mA]
4
5.7
5.7
5.5
5.4
5.4
5.2
4.1
PG
[Pa]
0.0
1065.2
1034.1
959.3
897.0
841.0
766.2
87.2
P
[kPa]
86
85
85
85
85
85
85
86
3
[kg/m ]
1.012
1.000
1.000
1.001
1.002
1.002
1.003
1.011
Q
WQ
S
WS
3
3
[m/s]
0.000
45.891
45.198
44.020
42.142
41.309
38.794
5.206
[m/s]
0.054
0.055
0.057
0.059
0.060
0.064
0.475
[m /s]
0.0000
0.0775
0.0764
0.0734
0.0702
0.0679
0.0649
0.0116
[m /s]
0.0016
0.0015
0.0015
0.0014
0.0014
0.0013
0.0015
2.5
• This table presents the transmitter current and 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 the
uncertainties of the venturi tube flow coefficient and pressure
measurements.
Figure 1 Measured and Predicted Centerline
Velocities Versus Volume Flow Rate
70
Centerline Speed, S [m/s]
60
50
Laminar Flow
40
30
20
Slug Flow
10
0
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Volume Flow Rate, Q [m3/s]
• The measured centerline velocity is between the
values predicted for slug and parabolic velocity.