When measuring small pressure differences with a manometer, often one arm of the manometer is inclined to improve the accuracy of the reading. (The pressure difference is still proportional to the vertical distance and not the actual length of the fluid along the tube.) The air pressure in a circular duct is to be measured using a manometer whose open arm is inclined 25° from the horizontal, as shown in Fig. P3−149. The density of the liquid in the manometer is 0.81 kg/L, and the vertical distance between the fluid levels in the two arms of the manometer is 8 cm. Determine the gage pressure of air in the duct and the length of the fluid column in the inclined arm above the fluid level in the vertical arm. FIGURE P3−149
When measuring small pressure differences with a manometer, often one arm of the manometer is inclined to improve the accuracy of the reading. (The pressure difference is still proportional to the vertical distance and not the actual length of the fluid along the tube.) The air pressure in a circular duct is to be measured using a manometer whose open arm is inclined 25° from the horizontal, as shown in Fig. P3−149. The density of the liquid in the manometer is 0.81 kg/L, and the vertical distance between the fluid levels in the two arms of the manometer is 8 cm. Determine the gage pressure of air in the duct and the length of the fluid column in the inclined arm above the fluid level in the vertical arm. FIGURE P3−149
Solution Summary: The author analyzes the gage pressure of air in the duct and the length of the fluid column in an inclined arm.
When measuring small pressure differences with a manometer, often one arm of the manometer is inclined to improve the accuracy of the reading. (The pressure difference is still proportional to the vertical distance and not the actual length of the fluid along the tube.) The air pressure in a circular duct is to be measured using a manometer whose open arm is inclined 25° from the horizontal, as shown in Fig. P3−149. The density of the liquid in the manometer is 0.81 kg/L, and the vertical distance between the fluid levels in the two arms of the manometer is 8 cm. Determine the gage pressure of air in the duct and the length of the fluid column in the inclined arm above the fluid level in the vertical arm.
Liquid manometers measure differential pressure by balancing the
weight of a liquid between two pressures. Light liquids such
as water can measure small pressure differences; mercury or other
heavy liquids are used for large pressure differences.
A 15° inclined manometer containing mercury is connected to two
taps A an B containing water. Tap B is 5 ft vertically higher than Tap A.
When the pressure in Tap B is 5 psi, the manometer reads 4 inches
along the inclined tube. Calculate the new manometer reading (in
inches) if the pressure in Tap A is increased by 3 psi.
2. Pipe A contains a liquid of SG=1.45 at and Pipe B contains a liquid of SG=0.95. The pressures are also
shown in the figure. Determine the difference in mercury level in the differential manometer, in mm.
SG=1.45
X
PA =1 kgf/cm²
3.0m
12.0 m
SG=0.95
PB = 1.8 kgf/cm²
X
Q2/
The pressure in a natural gas pipeline is measured by a double U-tube manometer with one
of the arms open to the atmosphere. The absolute pressure in the pipeline is to be
determined if hy-0.7 m, h-0.4 m, and h-1.0 m. Take the densities of water, oil, and
mercury to be 1000 kg/m2, 840 kg/m, and 13,600 kg/m2, respectively.
Oil
Water
ho
Natural
Mercury
(1-1)
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