CHEMICAL ENGINEERING

92 CHEMICAL ENGINEERING VOLUME 1 SOLUTIONS

Position Distance Manometer reading Air Velocityðarea
from axis
Water Air
velocity of annulus
of duct
(mm) (m)
(um/s) m^3 /s
(mm)

1 24 18.5 15.6 17.5 0.124

2 57 18.0 15.17 17.3 0.122

3 75 17.5 14.75 17.0 0.120

4 89 16.8 14.16 16.7 0.118

5 101 15.7 13.23 16.1 0.114

6 111 14.7 12.39 15.6 0.110

7 121 13.7 11.55 15.1 0.107

8 130 12.7 10.71 14.5 0.103

9 139 11.4 9.61 13.7 0.097

10 147 10.2 8.60 13.0 0.092

TotalD 1. 107

The velocity profile across the duct is plotted in Fig. 6d.

20

15

10

5

0 20 40 60 80 100 120 140

Distance from duct axis (mm)

Velocity (m/s)

Centre line

of duct Duct wall

Figure 6d.

PROBLEM 6.17

Explain the principle of operation of the pitot tube and indicate how it can be used in
order to measure the total flowrate of fluid in a duct. If a pitot tube is inserted in a circular