Siemens SITRANS FUH1010PVDX, Руководство по эксплуатации, Страница: 38 / 308

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CQO:1010PVXFM-3
Section 1
The degree of the flow profile curvature is directly proportional to the Reynolds number of the flowing
liquid. The FUH1010PVX software applies a compensation factor, which is selected based on knowledge
of the Reynolds number of the liquid. The algorithm continuously calculates this number from the mea-
sured flow velocity, the pipe diameter and the viscosity of the liquid. The user enters this information
during the site setup procedure. Certain models infer the current liquid viscosity and accommodate
installations whose piping configuration does not permit fully developed flow, such as conditions where
a limited upstream straight pipe run is available for transducer installation.
Reflect mounting automatically corrects for non-axial flow or cross flow conditions. When the exchange
of sonic signals occur by reflection off the far pipe wall as shown above, the average beam versus
stream angle will be equivalent to that of an axial flow stream.
Another important consideration is that the ultrasonic flowmeter has to compensate for the flow profile to
maintain calibration accuracy. Shown below is a graphic of a “fully-developed” flow profile. Note that the
fluid velocity increases toward the center (axis) of the flow stream.
Fluid velocity near the axis
of the flow stream tends to
be greater
Flow
Direction
Wide Beam transmissions exchanged between the
Upstream and Downstream transducers
Upstream
transducer
Downstream
transducer