E1C09 09/14/2010
15:5:1 Page 418
9.2 Convert the following gauge pressures into absolute pressure relative to one standard atmosphere:
a. À12.0 psi
b. 200 mm Hg
c. 10.0 kPa
d. 7.62 cm H 2 O
9.3 A water-filled manometer is used to measure the pressure in an air-filled tank. One leg of the
manometer is open to atmosphere. For a measured manometer deflection of 250 cm water, determine
the tank static pressure. Barometric pressure is 101.3 kPa abs.
9.4 A deadweight tester is used to provide a standard reference pressure for the calibration of a pressure
transducer. A combination of 25.3 kg f of 7.62-cm-diameter stainless steel disks is needed to balance
the tester piston against its internal pressure. For an effective piston area of 5.065 cm
2 and a piston
weight of 5.35 kg f , determine the standard reference pressure in bars, N/m
2 , and Pa abs. Barometric
pressure is 770 mm Hg abs, elevation is 20 m, and latitude is 42 degrees.
9.5 The pressure differential across an orifice plate meter is measured using an inclined tube manometer
with one pressure attached to each end of the manometer. Under no flow conditions, the manometer deflection is zero. For a set flow rate, the manometer deflects 10 cm H 2 O. With a manometer
inclination of 30 degrees relative to horizontal, determine the pressure differential across the orifice
meter.
9.6 Show that the static sensitivity of an inclined tube manometer is a factor of 1=sinu higher than for a
U-tube manometer.
9.7 Determine the static sensitivity of an inclined tube manometer set at an angle of 30 degrees. The
manometer tube measures the pressure difference of air using mercury as the manometer fluid.
9.8 Show that the instrument (systematic) uncertainty in an inclined tube manometer in Example 9.3
increases to 6.8 N/m
2 as u goes to 90 degrees.
9.9 Determine the maximum deflection and the natural frequency of a 0.1-in.-thick diaphragm made of
steel (E m ¼ 30 Mpsi, v p ¼ 0.32, r= 0.28 lb m /in.
3 ) if the diaphragm must be 0.75 in. in diameter.
Determine its differential pressure limit.
9.10 A strain gauge, diaphragm pressure transducer (accuracy: <0.1% reading) is subjected to a pressure
differential of 10 kPa. If the output is measured using a voltmeter having a resolution of 10 mV and
accuracy of better than 0.1% of the reading, estimate the uncertainty in pressure at the design stage.
How does this change at 100 and 1000 kPa?
9.11 Select a practical fluid to use in a manometer to measure pressures up to 69 kPa of an inert gas (g ¼
10.4 N/m
3 ), if water (g ¼ 9800 N/m
3 ), oil (S ¼ 0.82), and mercury (S ¼ 13.57) are available. Discuss
the rationale for your choice(s).
9.12 An air pressure over the 200- to 400-N/m
2 range is to be measured relative to atmosphere using a Utube manometer with mercury (S ¼ 13.57). Manometer resolution is 1 mm with a zero error
uncertainty of 0.5 mm. Estimate the design-stage uncertainty in gauge pressure based on the
manometer indication at 20
C. Would an inclined manometer (u ¼ 30 degrees) be a better choice if
the inclination could be set to within 0.5 degree?
9.13 Calculate the design-stage uncertainty in estimating a nominal pressure of 10,000 N/m
2 using an
inclined manometer (resolution: 1 mm; zero error uncertainty: 0.5 mm) with water at 20
C for
inclination angles of 10 to 90 degree (using 10-degree increments). The inclination angle can be set
to within 1 degree.
418 Chapter 9 Pressure and Velocity Measurements
15:5:1 Page 418
9.2 Convert the following gauge pressures into absolute pressure relative to one standard atmosphere:
a. À12.0 psi
b. 200 mm Hg
c. 10.0 kPa
d. 7.62 cm H 2 O
9.3 A water-filled manometer is used to measure the pressure in an air-filled tank. One leg of the
manometer is open to atmosphere. For a measured manometer deflection of 250 cm water, determine
the tank static pressure. Barometric pressure is 101.3 kPa abs.
9.4 A deadweight tester is used to provide a standard reference pressure for the calibration of a pressure
transducer. A combination of 25.3 kg f of 7.62-cm-diameter stainless steel disks is needed to balance
the tester piston against its internal pressure. For an effective piston area of 5.065 cm
2 and a piston
weight of 5.35 kg f , determine the standard reference pressure in bars, N/m
2 , and Pa abs. Barometric
pressure is 770 mm Hg abs, elevation is 20 m, and latitude is 42 degrees.
9.5 The pressure differential across an orifice plate meter is measured using an inclined tube manometer
with one pressure attached to each end of the manometer. Under no flow conditions, the manometer deflection is zero. For a set flow rate, the manometer deflects 10 cm H 2 O. With a manometer
inclination of 30 degrees relative to horizontal, determine the pressure differential across the orifice
meter.
9.6 Show that the static sensitivity of an inclined tube manometer is a factor of 1=sinu higher than for a
U-tube manometer.
9.7 Determine the static sensitivity of an inclined tube manometer set at an angle of 30 degrees. The
manometer tube measures the pressure difference of air using mercury as the manometer fluid.
9.8 Show that the instrument (systematic) uncertainty in an inclined tube manometer in Example 9.3
increases to 6.8 N/m
2 as u goes to 90 degrees.
9.9 Determine the maximum deflection and the natural frequency of a 0.1-in.-thick diaphragm made of
steel (E m ¼ 30 Mpsi, v p ¼ 0.32, r= 0.28 lb m /in.
3 ) if the diaphragm must be 0.75 in. in diameter.
Determine its differential pressure limit.
9.10 A strain gauge, diaphragm pressure transducer (accuracy: <0.1% reading) is subjected to a pressure
differential of 10 kPa. If the output is measured using a voltmeter having a resolution of 10 mV and
accuracy of better than 0.1% of the reading, estimate the uncertainty in pressure at the design stage.
How does this change at 100 and 1000 kPa?
9.11 Select a practical fluid to use in a manometer to measure pressures up to 69 kPa of an inert gas (g ¼
10.4 N/m
3 ), if water (g ¼ 9800 N/m
3 ), oil (S ¼ 0.82), and mercury (S ¼ 13.57) are available. Discuss
the rationale for your choice(s).
9.12 An air pressure over the 200- to 400-N/m
2 range is to be measured relative to atmosphere using a Utube manometer with mercury (S ¼ 13.57). Manometer resolution is 1 mm with a zero error
uncertainty of 0.5 mm. Estimate the design-stage uncertainty in gauge pressure based on the
manometer indication at 20
C. Would an inclined manometer (u ¼ 30 degrees) be a better choice if
the inclination could be set to within 0.5 degree?
9.13 Calculate the design-stage uncertainty in estimating a nominal pressure of 10,000 N/m
2 using an
inclined manometer (resolution: 1 mm; zero error uncertainty: 0.5 mm) with water at 20
C for
inclination angles of 10 to 90 degree (using 10-degree increments). The inclination angle can be set
to within 1 degree.
418 Chapter 9 Pressure and Velocity Measurements