# Q-4 The apparatus shown in the figure is used to measure the velocity of air at the center of a duct

Excerpt
duct, the liquid moves up to 6.7 cm on the slanted scale. Find the velocity of the air in the duct. Assuming a uniform velocity profile in the duct, calculate the rate of flow of the air. S = 0.7 6.7 cm – 2.3 cm

Q-4 The apparatus shown in the figure is used to measure the velocity of air at the center of a duct having a 10 cm diameter. A tube mounted at the center of the duct has a 2 mm diameter and is attached to one leg of a slant-tube manometer. A pressure tap in the wall of the duct is connected to the other end of the slant-tube manometer. The well of the slant-tube manometer is sufficiently large that the elevation of the fluid in it does not change significantly when fluid moves up the leg of the manometer. The air in the duct is at a temperature of 20°C, and the pressure is 150 kPa. The manometer liquid has a specific gravity of 0.7, and the slope of the leg is 30°. When there is no flow in the duct, the liquid surface in the manometer lies at 2.3 cm on the slanted scale. When there is flow in the duct, the liquid moves up to 6.7 cm on the slanted scale. Find the velocity of the air in the duct. Assuming a uniform velocity profile in the duct, calculate the rate of flow of the air. Transcribed Image Text: Q-4 The apparatus shown in the figure is used to measure the velocity
of air at the center of a duct having a 10 cm diameter. A tube mounted
at the center of the duct has a 2 mm diameter and is attached to one
leg of a slant-tube manometer. A pressure tap in the wall of the duct is
connected to the other end of the slant-tube manometer. The well of
10 cm
the slant-tube manometer is sufficiently large that the elevation of the
fluid in it does not change significantly when fluid moves up the leg of
p = 150 kPa
T= 20°C
the manometer. The air in the duct is at a temperature of 20°C, and
the pressure is 150 kPa. The manometer liquid has a specific gravity
30
of 0.7, and the slope of the leg is 30°. When there is no flow in the duct,
the liquid surface in the manometer lies at 2.3 cm on the slanted scale.
When there is flow in the duct, the liquid moves up to 6.7 cm on the
slanted scale. Find the velocity of the air in the duct. Assuming a
uniform velocity profile in the duct, calculate the rate of flow of the air.
S = 0.7
6.7 cm
– 2.3 cm