2. Velocity can be measured by instruments such as the Pitot tubes - static tubes where:
and Venturi meters where:
3. Basic pumps for liquids include reciprocating, gear, vane and centrifugal
A Pitot tube is to be used for measurement of the rate of flow of steam
at a pressure of 300 kPa above atmospheric pressure, flowing in a 10 cm
diameter pipe. If it is desired to measure flow rates in this pipe of
between 300 and 600 kg h-1, what would be the differential
pressures across the tube, in mm of water?
If across a 2 cm diameter orifice measuring the flow of brine of density
1080 kg m-3 in a 5 cm diameter pipe, the differential pressure
is 182 Pa, estimate the mass rate of flow of the brine. Take the orifice
discharge coefficient as 0.97.
A Venturi meter is being used to determine the flow of soyabean oil at
65°C in a pipe. The particular pipe is 15 cm in diameter, which decreases
to 6 cm in the throat of the Venturi. If the differential pressure is
measured as 14 cm of water, estimate the flow rate of the soyabean oil.
A volume of 0.5 m3 h-1 of water is being pumped
at a velocity of 1.1 m s-1 from the bottom of a header tank,
3 m deep, down three floors (a total fall of 10 m from the bottom of the
header tank) into the top of a water pressure tank which is maintained
at a pressure of 600 kPa above atmospheric. Estimate the theoretical pump
power required, ignoring pipe friction.
In the pumping system of worked Example
4.3, the actual pump selected for the duty would pump more water than
the 1.2 m3 min-1 needed for the duty. By plotting
a capacity curve for the system, varying the flow rate and determining
the total head for each selected rate, determine from the interaction
of this curve and the pump characteristic curve, the expected flow rate.
Assume flow is turbulent.
7. Using the same
flow rate as in worked Example 4.3
and the same piping system, determine the total head against which a
pump would have to operate if the pipeline diameter were halved to 7.5
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