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Unformatted text preview: STEVENS INSTITUTE OF TECHNOLOGY
CHARLES V. SCHAEFER, JR. SCHOOL OF ENGINEERING
MECHANICAL ENGINEERING DEPARTMENT
FLUID MECHANICS LABORATORY
FLOW METERS AND PIPE FLOW
To determine the characteristics of a common type of fluid flow meter, the sharp-edge orifice, and to analyze
the flow development in a straight pipe using the Air-flow facility.
The movement of fluid is a concept which relates to many disciplines in engineering. The losses incurred in
pipes or ducts, the losses in associated fittings and measurement of the fluid flows involved form a basic part
of most engineering courses and demand a practical demonstration in the laboratory. The following two
aspects of fluid flow systems that are of importance in flow metering and design of piping systems are considered in this laboratory experiment.
I) Orifice-plate flow meter: Orifice-plate flow meter is a device which causes a pressure drop in a flowing fluid
by providing a changing flow area. Since the pressure drop depends on flow rate, the orifice-plate flow meter
may be calibrated for use in pipe systems. Many other types of fluid flow meters are used in practice, based
on different operating principles1.
II) Flow development: Another aspect of piping system design involves the estimation and control of the flow
development in a straight pipes. The entrance length in any piping system is the region wherein the boundary layer develops to merge along the pipe axis2.
The experimental apparatus consists essentially of a long smooth walled pipe supported on a steel frame
with a centrifugal blower at the suction side as shown in the accompanying sketch. The pipe is segmented
so that it can be rearranged to insert flowmeInlet Flow Nozzle
ters and pipe fittings. A
& Flow Straightener
conical diffuser is used to
connect the piping sysDiffuser
tem to the centrifugal
blower that is mounted on
a floor standing metal
frame. A control panel
with a frequency-based
motor speed control is
used for flow control,
while pressure taps along
the complete length of the pipe permit the determination of pressure gradients.
A traversing Pitot tube enables the measurement of the velocity profile at three different stations along the
pipe. A fourteen tube bank manometer allows for head loss and velocities in the pipe to be measured. A precalibrated 80 mm inlet nozzle with a fixed coefficient of discharge (Cd) of 0.98 and contraction ratio of 4/7 is
1.See Fluid Mechanics, F. M. White, 6th edition, McGraw Hill, N.Y, pp. 402-424
2.See Fluid Mechanics, F. M. White, 6th edition, McGraw Hill, N.Y, pp. 346-349
Fluid Mechanics Laboratory: Flow Meters & Pipe Flow Page 1/2 used for all flow measurements. The nominal inlet diameter of the pipe is 80 mm, while the orifice is 50 mm
Please read the appropriate sections in the text to familiarize yourself with the concepts dealing with pipe
flow and losses in pipe fittings, and the principles of operation of orifice meter and other flow meters.
1) Use the preset configuration to measure the pressure drop across the orifice meter at two different flow
2) Remove the orifice meter and using the traversing Pitot tube, measure the velocity profile in the straight
pipe at three different (preassigned) locations for two different flow rates.
1) Plot the velocity profiles in the piping system (at the three locations where the measurements were
made) and determine the entrance length as a function of the flow Reynolds number.
2) Determine the coefficient of discharge, Cd, for the orifice meter and calculate its loss coefficient, Km.
1) Can the elbows and bends be used for flow metering? Use the results and the data for the orifice meter
(as well as others, such as the venturimeter or the flow nozzle) to discuss their feasibility.
2) Using the experimental data and the discharge coefficient, Cd, for the orifice meter, specify the range of
values for these coefficients which result from experimental error and uncertainty. How does the discharge coefficient, Cd, and the loss coefficient, Km, for the orifice meter compare with results from the literature?
3) How well did the functional relation for entrance length compare with the theory? In answering this question, be sure to allow for the effects of measurement errors.
4) How do the loss coefficients for the orifice plate, elbows, bends, and inlet nozzle, differ? Why? What significance does this difference have in selecting a meter for a specific application? Page 2/2 Fluid Mechanics Laboratory: Flow Meters & Pipe Flow ...
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- Spring '09