Chapt06

120 the vortex meter introduces a shedding element

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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.

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