Unformatted text preview: m Eq. (6.125) is the desired solution to the fluid-metering problem.
The mass flow is related to Q by
˙ Q (6.131) and is thus correlated by exactly the same formulas.
Figure 6.39 shows the three basic devices recommended for use by the International
Organization for Standardization (ISO) : the orifice, nozzle, and venturi tube. Thin-plate orifice. The thin-plate orifice, Fig. 6.39b, can be made with in the range
of 0.2 to 0.8, except that the hole diameter d should not be less than 12.5 mm. To measure p1 and p2, three types of tappings are commonly used: | v v 398 | e-Text Main Menu | Textbook Table of Contents | Study Guide 6.10 Fluid Meters 399 Ellipse 2d
d Bevel angle:
45° to 60° 0.6 d
d Flow D
d Flow Edge thickness:
0.005 D to 0.02 D t2 < 13 mm Plate thickness:
up to 0.05 D t1 < 0.15 D
nozzle shape Fig. 6.39 International standard
shapes for the three primary
Bernoulli obstruction-type meters:
(a) long radius nozzle; (b) thinplate orifice; (c) venturi nozzle.
(From Ref. 31 by permission of the
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- Spring '08
- Fluid Dynamics, e-Text Main Menu, Osborne Reynolds