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Unformatted text preview: s linearly proportional to the pressure drop.
(Courtesy of Martin Girard, DH
Instruments, Inc.) | e-Text Main Menu Pressure-equalization chamber | Textbook Table of Contents | Study Guide 6.10 Fluid Meters 397 times. Careful calibration is thus necessary. In Fig. 6.37 the laminar-flow concept has
been synthesized into a complete mass-flow system, with temperature control, differential pressure measurement, and a microprocessor all self-contained. The accuracy of
this device is rated at 0.2 percent. Bernoulli obstruction theory. Consider the generalized flow obstruction shown in Fig.
6.38. The flow in the basic duct of diameter D is forced through an obstruction of
diameter d; the ratio of the device is a key parameter
D (6.122) After leaving the obstruction, the flow may neck down even more through a vena contracta of diameter D2 d, as shown. Apply the Bernoulli and continuity equations for
incompressible steady frictionless flow to estimate the pressure change:
Continuity: Q Bernoulli: 4 p0 p1 D2V1 1
loss p1 – p2
head loss Vena contracta D2
D V1 d = βD V2 ≈ V1 2 ()
streamline | v v Fig. 6.38 Velocity and pressure
change through a generalized
Bernoulli obstruction meter. | e-Text Main Menu Deadwater
region | Textbook Table of Contents | Study Guide Chapter 6 Viscous Flow in Ducts Eliminat...
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- Spring '08