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Unformatted text preview: ss is duplicated in the reverse direction from B to A, creating frequency
fB. The difference fA fB is proportional to the flow rate. Figure 6.33b shows a dopplertype arrangement, where sound waves from transmitter T are scattered by particles or
contaminants in the flow to receiver R. Comparison of the two signals reveals a doppler
frequency shift which is proportional to the flow rate. Ultrasonic meters are nonintrusive and can be directly attached to pipe flows in the field (Fig. 6.34c). Their quoted
uncertainty of 1 to 2 percent can rise to 5 percent or more due to irregularities in
velocity profile, fluid temperature, or Reynolds number. For further details see Ref. 41.
Rotameter. The variable-area transparent rotameter of Fig. 6.35 has a float which, under the action of flow, rises in the vertical tapered tube and takes a certain equilibrium
position for any given flow rate. A student exercise for the forces on the float would
yield the approximate relation
Q Fig. 6.35 A commercial rotameter.
The float rises in the ta...
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This note was uploaded on 10/27/2009 for the course MAE 101a taught by Professor Sakar during the Spring '08 term at UCSD.
- Spring '08