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10.19 An ASME long radius nozzle ðb ¼ 0:5Þ is to be used to meter the flow of 20
C water through a
8-cm-i.d. pipe. If flow rates range from 0.6 to 1.6 L/s, select the range required of a single pressure
transducer if that transducer is used to measure pressure drop over the flow rate range. If the
transducer to be used has a typical error of 0.25% of full scale, estimate the uncertainty in flow rate at
the design stage.
10.20 A square-edged orifice plate is selected to meter the flow of water through a 2.3-in.-i.d. pipe
over the range of 10 to 50 gal/min at 60
F. It is desired to operate the orifice in the range where
C is independent of the Reynolds number for all flow rates. A pressure transducer having
accuracy to within 0.5% of reading is to be used. Select a suitable orifice plate and estimate
the design-stage uncertainty in the measured flow rate at 10, 25, and 50 gal/min. Assume
flange pressure taps and reasonable values for the systematic uncertainty on pertinent
parameters.
10.21 Estimate the error contribution to the uncertainty in flow rate due to the effect of the relative
humidity of air on air density. Consider the case of using an orifice plate to meter air flow if the
relative humidity of the 70
F air can vary from 10% to 80% but a density equivalent to 45% relative
humidity is used in the computations.
10.22 For Problem 10.21, suppose the air flow rate is 17 m
3 /hr at 20
C through a 6-cm-i.d. pipe, a squareedged orifice ðb ¼ 0:4Þ is used with flange taps, and the pressure drop can be measured to within
0.5% of reading for all pressures above 5 cm H 2 O using a manometer. If basic dimensions are
maintained to within 0.1 mm, estimate a design-stage uncertainty in the flow rate. Use p 1 ¼ 96:5 kPa
abs, R ¼ 287 N-m/kg-K.
10.23 An application uses water flowing at up to 0.2 m
3 /min of 20
C through a 10-cm-diameter pipe. The
engineer wants to select from a set of orifice plates using flange taps to measure and monitor the
flow. It is desired that the meter develop a nominal 250 mm Hg pressure head. Specify an appropriate
size (d o ) for the orifice meter. S Hg ¼ 13:6.
10.24 A sonic nozzle can be used to regulate air flow by intentionally designing it to choke the flow at the
throat. Consider the case where we use an ASME long radius nozzle to regulate air at 70
F (20
o C) to
45 ft
3 /min (1.27 m
3 /s). Determine the downstream pressure required to choke the nozzle if air
is supplied at 14.1 psia (97.2 kPa abs). Select a suitable nozzle throat diameter. k ¼ 1:4, R ¼ 53:3
(ft-lb)/(lb m -
R) ¼ 287 N-m/kg-K.
10.25 Select an appropriate range for a differential pressure transducer to be used with an ASME long
radius nozzle with b ¼ 0:5. This system is to be used to measure the flow of 20
C water through a
20-cm diameter pipe. The operating flow rate expected is between 5000 cm
3 /s and 50,000 cm
3 /s.
Estimate the permanent pressure loss associated with this nozzle. As an optional assignment, go
to a vendor catalog or Web site and select an appropriate pressure transducer from its listings that has
a 0- to 5-V DC output.
10.26 From a vendor catalog or online site, select a differential pressure transducer to measure between
203 Pa and 20,100 Pa across an obstruction meter. The transducer must be compatible with water.
The output signal is to be measured using a data-acquisition system with 0 to 5 V, 12-bit analog-todigital converter. Estimate the percent relative quantization error at the low and high flow rates.
Based on your selection, do you recommend any signal conditioning?
10.27 A vortex flow meter uses a shedder having a Strouhal number of 0.20. Estimate the mean duct
velocity if the shedding frequency indicated is 77 Hz and the shedder characteristic length is
1.27 cm.
464 Chapter 10 Flow Measurements
13:4:48 Page 464
10.19 An ASME long radius nozzle ðb ¼ 0:5Þ is to be used to meter the flow of 20
C water through a
8-cm-i.d. pipe. If flow rates range from 0.6 to 1.6 L/s, select the range required of a single pressure
transducer if that transducer is used to measure pressure drop over the flow rate range. If the
transducer to be used has a typical error of 0.25% of full scale, estimate the uncertainty in flow rate at
the design stage.
10.20 A square-edged orifice plate is selected to meter the flow of water through a 2.3-in.-i.d. pipe
over the range of 10 to 50 gal/min at 60
F. It is desired to operate the orifice in the range where
C is independent of the Reynolds number for all flow rates. A pressure transducer having
accuracy to within 0.5% of reading is to be used. Select a suitable orifice plate and estimate
the design-stage uncertainty in the measured flow rate at 10, 25, and 50 gal/min. Assume
flange pressure taps and reasonable values for the systematic uncertainty on pertinent
parameters.
10.21 Estimate the error contribution to the uncertainty in flow rate due to the effect of the relative
humidity of air on air density. Consider the case of using an orifice plate to meter air flow if the
relative humidity of the 70
F air can vary from 10% to 80% but a density equivalent to 45% relative
humidity is used in the computations.
10.22 For Problem 10.21, suppose the air flow rate is 17 m
3 /hr at 20
C through a 6-cm-i.d. pipe, a squareedged orifice ðb ¼ 0:4Þ is used with flange taps, and the pressure drop can be measured to within
0.5% of reading for all pressures above 5 cm H 2 O using a manometer. If basic dimensions are
maintained to within 0.1 mm, estimate a design-stage uncertainty in the flow rate. Use p 1 ¼ 96:5 kPa
abs, R ¼ 287 N-m/kg-K.
10.23 An application uses water flowing at up to 0.2 m
3 /min of 20
C through a 10-cm-diameter pipe. The
engineer wants to select from a set of orifice plates using flange taps to measure and monitor the
flow. It is desired that the meter develop a nominal 250 mm Hg pressure head. Specify an appropriate
size (d o ) for the orifice meter. S Hg ¼ 13:6.
10.24 A sonic nozzle can be used to regulate air flow by intentionally designing it to choke the flow at the
throat. Consider the case where we use an ASME long radius nozzle to regulate air at 70
F (20
o C) to
45 ft
3 /min (1.27 m
3 /s). Determine the downstream pressure required to choke the nozzle if air
is supplied at 14.1 psia (97.2 kPa abs). Select a suitable nozzle throat diameter. k ¼ 1:4, R ¼ 53:3
(ft-lb)/(lb m -
R) ¼ 287 N-m/kg-K.
10.25 Select an appropriate range for a differential pressure transducer to be used with an ASME long
radius nozzle with b ¼ 0:5. This system is to be used to measure the flow of 20
C water through a
20-cm diameter pipe. The operating flow rate expected is between 5000 cm
3 /s and 50,000 cm
3 /s.
Estimate the permanent pressure loss associated with this nozzle. As an optional assignment, go
to a vendor catalog or Web site and select an appropriate pressure transducer from its listings that has
a 0- to 5-V DC output.
10.26 From a vendor catalog or online site, select a differential pressure transducer to measure between
203 Pa and 20,100 Pa across an obstruction meter. The transducer must be compatible with water.
The output signal is to be measured using a data-acquisition system with 0 to 5 V, 12-bit analog-todigital converter. Estimate the percent relative quantization error at the low and high flow rates.
Based on your selection, do you recommend any signal conditioning?
10.27 A vortex flow meter uses a shedder having a Strouhal number of 0.20. Estimate the mean duct
velocity if the shedding frequency indicated is 77 Hz and the shedder characteristic length is
1.27 cm.
464 Chapter 10 Flow Measurements